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One of the most contagious diseases known to humankind, measles killed an average of 2.6 million people each year before a vaccine was developed, according to the World Health Organization. Widespread vaccination has slashed the death toll. However, lack of access to vaccination and refusal to get vaccinated means measles still infects more than 7 million people and kills more than 100,000 each year worldwide as reported by WHO. The cases are on the rise, tripling in early 2019 and some experience well-known long-term consequences, including brain damage and vision and hearing loss. Previous epidemiological research into immune amnesia suggests that death rates attributed to measles could be even higher, accounting for as much as 50 percent of all childhood mortality.
Over the last decade, evidence has mounted that the measles vaccine protects in two ways. It prevents the well-known acute illness with spots and fever and also appears to protect from other infections over the long term by giving general boost to the immune system. The measles virus can impair the body’s immune memory, causing so-called immune amnesia. By protecting against measles infection, the vaccine prevents the body from losing or “forgetting” its immune memory and preserves its resistance to other infections. Researchers showed that the measles virus wipes out 11% to 73% of the different antibodies that protect against viral and bacterial strains a person was previously immune to like from influenza to herpes virus to bacteria that cause pneumonia and skin infections.
This study at Harvard Medical School and their collaborators is the first to measure the immune damage caused by the virus and underscores the value of preventing measles infection through vaccination. The discovery that measles depletes people’s antibody repertoires, partially obliterating immune memory to most previously encountered pathogens, supports the immune amnesia hypothesis. It was found that those who survive measles gradually regain their previous immunity to other viruses and bacteria as they get re-exposed to them. But because this process may take months to years, people remain vulnerable in the meantime to serious complications of those infections and thus booster shots of routine vaccines may be required.
VirScan detects antiviral and antibacterial antibodies in the blood that result from current or past encounters with viruses and bacteria, giving an overall snapshot of the immune system. Researchers gathered blood samples from unvaccinated children during a 2013 measles outbreak in the Netherlands and used VirScan to measure antibodies before and two months after infection in 77 children who’d contracted the disease. The researchers also compared the measurements to those of 115 uninfected children and adults. Researchers found a striking drop in antibodies from other pathogens in the measles-infected children that clearly suggested a direct effect on the immune system resembling measles-induced immune amnesia.
Further tests revealed that severe measles infection reduced people’s overall immunity more than mild infection. This could be particularly problematic for certain categories of children and adults, the researchers said. The present study observed the effects in previously healthy children only. But, measles is known to hit malnourished children much harder, the degree of immune amnesia and its effects could be even more severe in less healthy populations. Inoculation with the MMR (measles, mumps, rubella) vaccine did not impair children’s overall immunity. The results align with decades of research. Ensuring widespread vaccination against measles would not only help prevent the expected 120,000 deaths that will be directly attributed to measles this year alone, but could also avert potentially hundreds of thousands of additional deaths attributable to the lasting damage to the immune system.
Obesity is a global concern that is associated with many chronic complications such as type 2 diabetes, insulin resistance (IR), cardiovascular diseases, and cancer. Growing evidence has implicated the digestive system, including its microbiota, gut-derived incretin hormones, and gut-associated lymphoid tissue in obesity and IR. During high fat diet (HFD) feeding and obesity, a significant shift occurs in the microbial populations within the gut, known as dysbiosis, which interacts with the intestinal immune system. Similar to other metabolic organs, including visceral adipose tissue (VAT) and liver, altered immune homeostasis has also been observed in the small and large intestines during obesity.
A link between the gut microbiota and the intestinal immune system is the immune-derived molecule immunoglobulin A (IgA). IgA is a B cell antibody primarily produced in dimeric form by plasma cells residing in the gut lamina propria (LP). Given the importance of IgA on intestinal–gut microbe immunoregulation, which is directly influenced by dietary changes, scientists hypothesized that IgA may be a key player in the pathogenesis of obesity and IR. Here, in this study it was demonstrate that IgA levels are reduced during obesity and the loss of IgA in mice worsens IR and increases intestinal permeability, microbiota encroachment, and downstream inflammation in metabolic tissues, including inside the VAT.
IgA deficiency alters the obese gut microbiota and its metabolic phenotype can be recapitulated into microbiota-depleted mice upon fecal matter transplantation. In addition, the researchers also demonstrated that commonly used therapies for diabetes such as metformin and bariatric surgery can alter cellular and stool IgA levels, respectively. These findings suggested a critical function for IgA in regulating metabolic disease and support the emerging role for intestinal immunity as an important modulator of systemic glucose metabolism.
Overall, the researchers demonstrated a critical role for IgA in regulating intestinal homeostasis, metabolic inflammation, and obesity-related IR. These findings identify intestinal IgA+ immune cells as mucosal mediators of whole-body glucose regulation in diet-induced metabolic disease. This research further emphasized the importance of the intestinal adaptive immune system and its interactions with the gut microbiota and innate immune system within the larger network of organs involved in the manifestation of metabolic disease.
Future investigation is required to determine the impact of IgA deficiency during obesity in humans and the role of metabolic disease in human populations with selective IgA deficiency, especially since human IgA deficiency is associated with an altered gut microbiota that cannot be fully compensated with IgM. However, the research identified IgA as a critical immunological molecule in the intestine that impacts systemic glucose homeostasis, and treatments targeting IgA-producing immune populations and SIgA may have therapeutic potential for metabolic disease.
4.1.8 Newly Found Functions of B Cell, Volume 2 (Volume Two: Latest in Genomics Methodologies for Therapeutics: Gene Editing, NGS and BioInformatics, Simulations and the Genome Ontology), Part 4: Single Cell Genomics
The importance of B cells to human health is more than what is already known. Vaccines capable of eradicating disease activate B cells, cancer checkpoint blockade therapies are produced using B cells, and B cell deficiencies have devastating impacts. B cells have been a subject of fascination since at least the 1800s. The notion of a humoral branch to immunity emerged from the work of and contemporaries studying B cells in the early 1900s.
Efforts to understand how we could make antibodies from B cells against almost any foreign surface while usually avoiding making them against self, led to Burnet’s clonal selection theory. This was followed by the molecular definition of how a diversity of immunoglobulins can arise by gene rearrangement in developing B cells. Recombination activating gene (RAG)-dependent processes of V-(D)-J rearrangement of immunoglobulin (Ig) gene segments in developing B cells are now known to be able to generate an enormous amount of antibody diversity (theoretically at least 1016 possible variants).
With so much already known, B cell biology might be considered ‘‘done’’ with only incremental advances still to be made, but instead, there is great activity in the field today with numerous major challenges that remain. For example, efforts are underway to develop vaccines that induce broadly neutralizing antibody responses, to understand how autoantigen- and allergen-reactive antibodies arise, and to harness B cell-depletion therapies to correct non-autoantibody-mediated diseases, making it evident that there is still an enormous amount we do not know about B cells and much work to be done.
Multiple self-tolerance checkpoints exist to remove autoreactive specificities from the B cell repertoire or to limit the ability of such cells to secrete autoantigen-binding antibody. These include receptor editing and deletion in immature B cells, competitive elimination of chronically autoantigen binding B cells in the periphery, and a state of anergy that disfavors PC (plasma cell) differentiation. Autoantibody production can occur due to failures in these checkpoints or in T cell self-tolerance mechanisms. Variants in multiple genes are implicated in increasing the likelihood of checkpoint failure and of autoantibody production occurring.
Autoantibodies are pathogenic in a number of human diseases including SLE (Systemic lupus erythematosus), pemphigus vulgaris, Grave’s disease, and myasthenia gravis. B cell depletion therapy using anti-CD20 antibody has been protective in some of these diseases such as pemphigus vulgaris, but not others such as SLE and this appears to reflect the contribution of SLPC (Short lived plasma cells) versus LLPC (Long lived plasma cells) to autoantibody production and the inability of even prolonged anti-CD20 treatment to eliminate the later. These clinical findings have added to the importance of understanding what factors drive SLPC versus LLPC development and what the requirements are to support LLPCs.
B cell depletion therapy has also been efficacious in several other autoimmune diseases, including multiple sclerosis (MS), type 1 diabetes, and rheumatoid arthritis (RA). While the potential contributions of autoantibodies to the pathology of these diseases are still being explored, autoantigen presentation has been posited as another mechanism for B cell disease-promoting activity.
In addition to autoimmunity, B cells play an important role in allergic diseases. IgE antibodies specific for allergen components sensitize mast cells and basophils for rapid degranulation in response to allergen exposures at various sites, such as in the intestine (food allergy), nose (allergic rhinitis), and lung (allergic asthma). IgE production may thus be favored under conditions that induce weak B cell responses and minimal GC (Germinal center) activity, thereby enabling IgE+ B cells and/or PCs to avoid being outcompeted by IgG+ cells. Aside from IgE antibodies, B cells may also contribute to allergic inflammation through their interactions with T cells.
B cells have also emerged as an important source of the immunosuppressive cytokine IL-10. Mouse studies revealed that B cell-derived IL-10 can promote recovery from EAE (Experimental autoimmune encephalomyelitis) and can be protective in models of RA and type 1 diabetes. Moreover, IL-10 production from B cells restrains T cell responses during some viral and bacterial infections. These findings indicate that the influence of B cells on the cytokine milieu will be context dependent.
The presence of B cells in a variety of solid tumor types, including breast cancer, ovarian cancer, and melanoma, has been associated in some studies with a positive prognosis. The mechanism involved is unclear but could include antigen presentation to CD4 and CD8 T cells, antibody production and subsequent enhancement of presentation, or by promoting tertiary lymphoid tissue formation and local T cell accumulation. It is also noteworthy that B cells frequently make antibody responses to cancer antigens and this has led to efforts to use antibodies from cancer patients as biomarkers of disease and to identify immunotherapy targets.
Malignancies of B cells themselves are a common form of hematopoietic cancer. This predilection arises because the gene modifications that B cells undergo during development and in immune responses are not perfect in their fidelity, and antibody responses require extensive B cell proliferation. The study of B cell lymphomas and their associated genetic derangements continues to be illuminating about requirements for normal B cell differentiation and signaling while also leading to the development of targeted therapies.
Overall this study attempted to capture some of the advances in the understanding of B cell biology that have occurred since the turn of the century. These include important steps forward in understanding how B cells encounter antigens, the co-stimulatory and cytokine requirements for their proliferation and differentiation, and how properties of the B cell receptor, the antigen, and helper T cells influence B cell responses. Many advances continue to transform the field including the impact of deep sequencing technologies on understanding B cell repertoires, the IgA-inducing microbiome, and the genetic defects in humans that compromise or exaggerate B cell responses or give rise to B cell malignancies.
Other advances that are providing insight include:
single-cell approaches to define B cell heterogeneity,
glycomic approaches to study effector sugars on antibodies,
new methods to study human B cell responses including CRISPR-based manipulation, and
the use of systems biology to study changes at the whole organism level.
With the recognition that B cells and antibodies are involved in most types of immune response and the realization that inflammatory processes contribute to a wider range of diseases than previously believed, including, for example, metabolic syndrome and neurodegeneration, it is expected that further
basic research-driven discovery about B cell biology will lead to more and improved approaches to maintain health and fight disease in the future.
The human body is often described as being ‘at war’. By this, it is meant that the body is constantly under attack from things that are trying to do it harm. These include toxins, bacteria, fungi, parasites and viruses. The human immune system is one of the most effective defense mechanisms known to nature and can sometimes can be overwhelmed by disease. Yet, on occasions our immune systems turn on our own tissue and attack it which can trigger conditions such as type I diabetes, rheumatoid arthritis and lupus.
In the case of rheumatoid arthritis, immune cells start to attack tissues in the joins which causes them to become painful, stiff and swollen. It is known that one third of those who develop rheumatoid arthritis, feel the horrible effects of the disease within two years of its onset. Immunologist Adrian Hayday, which is a researcher at Francis Crick Institute of London says that the current treatment for rheumatoid arthritis require patients to take the drugs for the rest of their lives. But, researchers such as Hayday found an unexpected ally in the battle against autoimmune disease, cancer.
However, there is a positive consequence to the discovery that cancer immunotherapies have the effect of triggering autoimmune diseases and for the first-time rheumatoid arthritis can be detected at the earliest stages. At present, people are not diagnosed with the condition until symptoms have already made their lives so unpleasant, they have gone to see their doctors. As a result, research backed by Cancer Research UK and Arthritis Research UK, has been launched with the aim of uncovering the roots of autoimmune disease from research on cancer patients.
The scientists mentioned stress that their work is only now start and warn that it will still take several years of research to get substantial results. Nevertheless, uncovering the first stages of an autoimmune disease emerging in a person’s body should give researchers a vital lead in ultimately developing treatments that will prevent or halt a range of conditions that currently cause a great deal of misery and require constant medication.
Our immune defenses consist of a range of cells and proteins that notice invading micro-organisms and attack them. The first line of defense, yet, consists of simple physical barriers similar to skin, which blocks invaders from entering your body. When this defense is penetrated, they are attacked by a number of agents. The key cells, leukocytes seek out and destroy disease-causing organisms. Neutrophils rush to the site of an infection and attack invading bacteria. Helper T-cells give instructions to other cells while killer T-cells punch holes in infected cells so that their contents ooze out. After these macrophages clean up the mess left behind.
Another significant agent is the B-cell, which produces antibodies that lock on to sites on the surface of bacteria or viruses and immobilize them until macrophages consume them. These cells can live a long time and can answer quickly following a second exposure to the same infections. In conclusion, suppressor T-cells act when an infection has been distributed with and the immune system needs to be reassured, the killer cells may keep on attacking, as they do in autoimmune diseases. By slowing down the immune system, regulatory T-cells prevent damage to “good” cells.
During pregnancy, the baby is mostly protected from harmful microorganisms by the amniotic sac, but recent research suggests the baby could be exposed to small quantities of microbes from the placenta, amniotic fluid, umbilical cord blood and fetal membranes. One theory is that any possible prenatal exposure could ‘pre-seed’ the infant microbiome. In other words, to set the right conditions for the ‘main seeding event’ for founding the infant microbiome.
When a mother gives birth vaginally and if she breastfeeds, she passes on colonies of essential microbes to her baby. This continues a chain of maternal heritage that stretches through female ancestry for thousands of generations, if all have been vaginally born and breastfed. This means a child’s microbiome, that is the trillions of microorganisms that live on and in him or her, will resemble the microbiome of his/her mother, the grandmother, the great-grandmother and so on, if all have been vaginally born and breastfed.
As soon as the mother’s waters break, suddenly the baby is exposed to a wave of the mother’s vaginal microbes that wash over the baby in the birth canal. They coat the baby’s skin, and enter the baby’s eyes, ears, nose and some are swallowed to be sent down into the gut. More microbes form of the mother’s gut microbes join the colonization through contact with the mother’s faecal matter. Many more microbes come from every breath, from every touch including skin-to-skin contact with the mother and of course, from breastfeeding.
With formula feeding, the baby won’t receive the 700 species of microbes found in breast milk. Inside breast milk, there are special sugars called human milk oligosaccharides (HMO’s) that are indigestible by the baby. These sugars are designed to feed the mother’s microbes newly arrived in the baby’s gut. By multiplying quickly, the ‘good’ bacteria crowd out any potentially harmful pathogens. These ‘good’ bacteria help train the baby’s naive immune system, teaching it to identify what is to be tolerated and what is pathogen to be attacked. This leads to the optimal training of the infant immune system resulting in a child’s best possible lifelong health.
With C-section birth and formula feeding, the baby is not likely to acquire the full complement of the mother’s vaginal, gut and breast milk microbes. Therefore, the baby’s microbiome is not likely to closely resemble the mother’s microbiome. A baby born by C-section is likely to have a different microbiome from its mother, its grandmother, its great-grandmother and so on. C-section breaks the chain of maternal heritage and this break can never be restored.
The long term effect of an altered microbiome for a child’s lifelong health is still to be proven, but many studies link C-section with a significantly increased risk for developing asthma, Type 1 diabetes, celiac disease and obesity. Scientists might not yet have all the answers, but the picture that is forming is that C-section and formula feeding could be significantly impacting the health of the next generation. Through the transgenerational aspect to birth, it could even be impacting the health of future generations.
Single-cell RNA sequencing (scRNA-seq) is a recent technology that enables fine-grained discovery of cellular subtypes and specific cell states. It routinely uses machine learning methods, such as feature learning, clustering, and classification, to assist in uncovering novel information from scRNA-seq data. However, current methods are not well suited to deal with the substantial amounts of noise that is created by the experiments or the variation that occurs due to differences in the cells of the same type. Here, we develop a new hybrid approach, Deep Unsupervised Single-cell Clustering (DUSC), that integrates feature generation based on a deep learning architecture with a model-based clustering algorithm, to find a compact and informative representation of the single-cell transcriptomic data generating robust clusters. We also include a technique to estimate an efficient number of latent features in the deep learning model. Our method outperforms both classical and state-of-the-art feature learning and clustering methods, approaching the accuracy of supervised learning. We applied DUSC to single-cell transcriptomics dataset obtained from a triple-negative breast cancer tumor to identify potential cancer subclones accentuated by copy-number variation and investigate the role of clonal heterogeneity. Our method is freely available to the community and will hopefully facilitate our understanding of the cellular atlas of living organisms as well as provide the means to improve patient diagnostics and treatment.
Jenny Mjösberg and Rickard Sandberg are principal investigators at Karolinska Institutet’s Department of Medicine, Huddinge and Department of Cell and Molecular Biology, respectively. Credit: Stefan Zimmerman.
A relatively newly discovered group of immune cells known as ILCs have been examined in detail in a new study published in the journal Nature Immunology. By analysing the gene expression in individual tonsil cells, scientists at Karolinska Institutet have found three previously unknown subgroups of ILCs, and revealed more about how these cells function in the human body.
Innate lymphoid cells (ILCs) are a group of immune cells that have only relatively recently been discovered in humans. Most of current knowledge about ILCs stems from animal studies of e.g. inflammation or infection in the gastrointestinal tract. There is therefore an urgent need to learn more about these cells in humans.
Previous studies have shown that ILCs are important for maintaining the barrier function of the mucosa, which serves as a first line of defence against microorganisms in the lungs, intestines and elsewhere. However, while there is growing evidence to suggest that ILCs are involved in diseases such as inflammatory bowel disease, asthma and intestinal cancer, basic research still needs to be done to ascertain exactly what part they play.
Two research groups, led by Rickard Sandberg and Jenny Mjösberg, collaborated on a study of ILCs from human tonsils. To date, three main groups of human ILCs are characterized. In this present study, the teams used a novel approach that enabled them to sort individual tonsil cells and measure their expression across thousands of genes. This way, the researchers managed to categorise hundreds of cells, one by one, to define the types of ILCs found in the human tonsils.
Unique gene expression profiles
Rickard Sandberg, credit: Stefan Zimmerman,
“We used cluster analyses to demonstrate that ILCs congregate into ILC1, ILC2, ILC3 and NK cells, based on their unique gene expression profiles,” says Professor Sandberg at Karolinska Institutet’sDepartment of Cell and Molecular Biology, and the Stockholm branch of Ludwig Cancer Research. “Our analyses also discovered the expression of numerous genes of previously unknown function in ILCs, highlighting that these cells are likely doing more than what we previously knew.”
By analysing the gene expression profiles (or transcriptome) of individual cells, the researchers found that one of the formerly known main groups could be subdivided.
Jenny Mjösberg, credit: Stefan Zimmerman.
“We’ve identified three new subgroups of ILC3s that evince different gene expression patterns and that differ in how they react to signalling molecules and in their ability to secrete proteins,” says Dr Mjösberg at Karolinska Institutet’s Department of Medicine in Huddinge, South Stockholm. “All in all, our study has taught us a lot about this relatively uncharacterised family of cells and our data will serve as an important resource for other researchers.”
The study was financed by grants from a number of bodies, including the Swedish Research Council, the Swedish Cancer Society, the EU Framework Programme for Research and Innovation, the Swedish Society for Medical Research, the Swedish Foundation for Strategic Research and Karolinska Institutet.
Compilation of References by Leaders in Pharmaceutical Business Intelligence in the Journal http://pharmaceuticalintelligence.com about
Proteomics, Metabolomics, Signaling Pathways, and Cell Regulation
Curator: Larry H Bernstein, MD, FCAP
Proteomics
The Human Proteome Map Completed
Reporter and Curator: Larry H. Bernstein, MD, FCAP
33. Cardiac Contractility & Myocardial Performance: Therapeutic Implications of Ryanopathy (Calcium Release- related Contractile Dysfunction) and Catecholamine Responses
Author, and Content Consultant to e-SERIES A: Cardiovascular Diseases: Justin Pearlman, MD, PhD, FACC
Author and Curator: Larry H Bernstein, MD, FCAP
and Article Curator: Aviva Lev-Ari, PhD, RN
8. microRNA called miRNA-142 involved in the process by which the immature cells in the bone marrow give rise to all the types of blood cells, including immune cells and the oxygen-bearing red blood cells
36. Harnessing Personalized Medicine for Cancer Management, Prospects of Prevention and Cure: Opinions of Cancer Scientific Leaders @http://pharmaceuticalintelligence.com
37. GSK for Personalized Medicine using Cancer Drugs needs Alacris systems biology model to determine the in silico
effect of the inhibitor in its “virtual clinical trial”
11. Disruption of Calcium Homeostasis: Cardiomyocytes and Vascular Smooth Muscle Cells: The Cardiac and
Cardiovascular Calcium Signaling Mechanism
Author and Curator: Larry H Bernstein, MD, FCAP, Author, and Content Consultant to e-SERIES A:
Cardiovascular Diseases: Justin Pearlman, MD, PhD, FACC and Curator: Aviva Lev-Ari, PhD, RN
12. The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and
Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia,
Similarities and Differences, and Pharmaceutical Targets
Author and Curator: Larry H Bernstein, MD, FCAP, Author, and Content Consultant to
e-SERIES A: Cardiovascular Diseases: Justin Pearlman, MD, PhD, FACC and
Curator: Aviva Lev-Ari, PhD, RN
Computationally designed “self”-peptide could be used to better target drugs to tumors, to ensure pacemakers are not rejected, and to enhance medical imaging technologies
Researchers have created a molecule that helps nanoparticles evade immune attack and could improve drug delivery.
By Dan Cossins | February 21, 2013
A macrophage at work in a mouse, stretching itself to gobble up two smaller particlesFLICKR, MAGNARAMA synthetic molecule attached to nanoparticles acts like a passport, convincing immune cells to let the particles pass unimpeded through the body, according to a study published today (February 21) in Science. The computationally designed “self”-peptide could be used to better target drugs to tumors, to ensure pacemakers are not rejected, and to enhance medical imaging technologies.
“It’s the first molecule that can be attached to anything to attenuate the innate immune system, which is currently limiting us from delivering therapeutic particles and implanting devices,” saidDennis Discher, a professor of biophysical engineering at the University of Pennsylvania and a coauthor of the study.
“This is really interesting work,” said Joseph DeSimone, a chemical engineer at the University of North Carolina, Chapel Hill, who was not involved in the research, in an e-mail to The Scientist. “[It] strongly validates the idea of using biological evasion strategies.”
Macrophages recognize, engulf, and clear out foreign invaders, whether they’re microbes entering through a wound or a drug-loaded nanoparticle injected to target disease. Previously, researchers have attempted to escape this response by coating nanoparticles with polymer “brushes” to physically block the adhesion of blood proteins that alert macrophages to the particles’ presence. But these brushes can only delay the macrophage-signaling proteins for so long, and they can hinder uptake by the diseased cells being targeted.
With that in mind, Discher and colleagues tried instead to find a way to convince macrophages that nanoparticles are part of the body. Their previous research had shown that a membrane protein called CD47, which binds to macrophages in humans, signals “self” to the immune system, so that particles with this protein are not attacked.
Examining the architecture of the bond between CD47 and its macrophage receptor, SIRPα, the researchers were able to design a synthetic self-peptide with a similarly snug fit. “This is the key, literally, to unlocking innate immune pacification,” said Discher.
When they chemically synthesized the 21-amino-acid self-peptide and attached it to nanobeads as small as viruses in mice genetically engineered to have human-like SIRPα receptors, the researchers showed that beads with the self-peptide stayed in the blood of for longer than beads with no peptide: 30 minutes after being injected with equal numbers of each type, there were 4 times as many beads with the peptide attached than without. The results demonstrate that the synthetic molecule can reduce the rate at which phagocytes clear the beads from the body, said Discher.
Then, in mice with human lung cancer, the researchers injected fluorescently dyed beads with and without the peptide, and saw that the “self”-beads got through the macrophage-filled spleen and liver and accumulated in greater numbers in the tumor, providing a brighter signal under when imaged. In fact, the self-beads provided a signal from the tumor as strong as beads coated with human CD47.
Finally, to see whether the biological evasion strategy can be successfully combined with targeting, the researchers loaded an anticancer drug into self-beads also coated with antibodies that target cancer cells. Sure enough, these antibody-coated self-beads consistently shrank tumors more than antibody-coated beads lacking the peptide. This confirmed that when antibodies draw the attention of the macrophage, the self-peptides inhibit the macrophage’s response, acting as a “don’t-eat-me” signal, said Discher.
The results demonstrate that the synthetic peptide can provide therapeutic nanoparticles with extra time in the body—time that improves drug delivery. Furthermore, the relative simplicity of the peptide means it can be easily synthesized, making it an attractive component for use in a variety of future applications.
“The findings are “compelling” and “the technology merits moving forward,” Omid Farokhzad, director of the Laboratory of Nanomedicine and Biomaterials at Brigham and Women’s Hospital, part of Harvard Medical School, said in an e-mail to The Scientist.
A crucial next step is to test the efficacy of synthetic self-peptides in humans, Farokhzad added. “The truly relevant test is looking at human pharmacokinetics to see circulating half-life advantages of nanoparticles and their effect on therapeutic outcome.”
P.L. Rodriguez et al., “Minimal ‘self’ peptides that inhibit phagocytic clearance and enhance delivery of nanoparticles,” Science, 339: 971-74, 2013.
TABLE 4: Current Interventions______________________________________________________________________________________________________________
ABSTRACT:
Overall purpose is to find a method to manipulate IDO for clinical applications, mainly the focus of this review is is cancer prevention and treatment. The first study proving the connection between IDO and immune response came from, a very natural event, a protection of pregnancy in human. This led to discover that high IDO expression is a common factor in cancer tumors. Thus, attention promoted investigations on IDO’s role in various disease states, immune disorders, transplantation, inflammation, women health, mood disorders.
Many approaches, vaccines and adjuvants are underway to find new immunotherapies by combining the power of DCs in immune response regulation and specific direction of siRNA. As a result, with this unique qualities of IDO, DCs and siRNA, we orchestrated a novel intervention for immunomodulation of IDO by inhibiting with small interference RNA, called siRNA-IDO-DCvax. Proven that our DCvax created a delay and regression of tumor growth without changing the natural structure and characterization of DCs in melanoma and breast cancers in vivo. (** The shRNA IDO- DCvax is developed by Regen BioPhrama, San Diego, CA , Thomas Ichim, Ph.D, CSO. and David Koos, CEO)
Double-Edged Sword of IDO: The Good and The Bad for Clinical intervention and Developments
IDO almost has a dual role. There is a positive side of high expression of IDO during pregnancy(29; 28; 114), transplants (115; 116; 117; 118; 119), infectious diseases(96)and but this tolerance is negative during autoimmune-disorders (120; 121; 122), tumors of cancer (123; 124; 117; 121; 125; 126; 127) (127), and mood disorders (46). The increased IDO expression has a double-edged sword in human physiology provides a positive role during protection of fetus and grafts after transplantations but becomes a negative factor during autoimmune disorders, cancer, sepsis and mood disorders.
Prevention of allogeneic fetal rejection is possible by tryptophan metabolism (26) rejecting with lack of IDO but allocating if IDO present (29; 28; 114). These studies lead to find “the natural regulation mechanism” for protecting the transplants from graft versus host disease GVHD (128) and getting rid of tumors.
The plasticity of mammary and uterus during reproduction may hold some more answers to prevent GVHD and tumors of cancer with good understanding of IDO and tryptophan mechanism (129; 130). After allogeneic bone marrow transplants the risk of solid tumor development increased about 80% among 19,229 patients even with a greater risk among patients under 18 years old (117). The adaptation of tolerance against host mechanism is connected to the IDO expression (131). During implantation and early pregnancy IDO has a role by making CD4+CD25+Foxp3+ regulatory T cells (Tregs) and expressing in DCs and MQs (114; 132; 133).
Clonal deletion mechanism prevents mother to react with paternal products since female mice accepted the paternal MHC antigen-expressing tumor graft during pregnancy and rejected three weeks after delivery (134). CTLA-4Ig gene therapy alleviates abortion through regulation of apoptosis and inhibition of spleen lymphocytes (135).
Immune System and IDO DCs are the orchestrator of the immune response (56; 57; 58) with list of functions in uptake, processing, and presentation of antigens; activation of effector cells, such as T-cells and NK-cells; and secretion of cytokines and other immune-modulating molecules to direct the immune response. The differential regulation of IDO in distinct DC subsets is widely studied to delineate and correct immune homeostasis during autoimmunity, infection and cancer and the associated immunological outcomes. Genesis of antigen presenting cells (APCs), eventually the immune system, require migration of monocytes (MOs), which is originated in bone marrow. Then, these MOs move from bloodstream to other tissues to become macrophages and DCs (59; 60).
Initiation of immune response requires APCs to link resting helper T-cell with the matching antigen to protect body. DCs are superior to MQs and MOs in their immune action model. When DCs are first described (61) and classified, their role is determined as a highly potent antigen-presenting cell (APC) subset with 100 to 1000-times more effective than macrophages and B-cells in priming T-cells. Both MQs and monocytes phagocytize the pathogen, and their cell structure contains very large nucleus and many internal vesicles. However, there is a nuance between MQ and DCs, since DCs has a wider capacity of stimulation, because MQs activates only memory T cells, yet DCs can activate both naïve and memory T cells.
DCs are potent activators of T cells and they also have well controlled regulatory roles. DC properties determine the regulation regardless of their origin or the subset of the DCs. DCs reacts after identification of the signals or influencers for their inhibitory, stimulatory or regulatory roles, before they express a complex repertoire of positive and negative cytokines, transmembrane proteins and other molecules. Thus, “two signal theory” gains support with a defined rule. The combination of two signals, their interaction with types of cells and time are critical.
In short, specificity and time are matter for a proper response. When IDO mRNA expression is activated with CTL40 ligand and IFNgamma, IDO results inhibition of T cell production (4). However, if DCs are inhibited by 1MT, an inhibitor of IDO, the response stop but IgG has no affect (10). In addition, if the stimulation is started by a tryptophan metabolite, which is downstream of IDO, such as 3-hydroxyantranilic or quinolinic acids, it only inhibits Th1 but not Th2 subset of T cells (62).
Furthermore, inclusion of signal molecules, such as Fas Ligand, cytochrome c, and pathways also differ in the T cell differentiation mechanisms due to combination, time and specificity of two-signals. The co-culture experiments are great tool to identify specific stimuli in disease specific microenvironment (63; 12; 64) for discovering the mechanism and interactions between molecules in gene regulation, biochemical mechanism and physiological function during cell differentiation.
As a result, the simplest differential cell development from the early development of DCs impact the outcome of the data. For example, collection of MOs from peripheral blood mononuclear cells (PBMCs) with IL4 and GM-CSF leads to immature DCs (iDCs). On next step, treatment of iDCs with tumor necrosis factor (TNF) or other plausible cytokines (TGFb1, IFNgamma, IFNalpha, IFNbeta, IL6 etc.) based on the desired outcome differentiate iDCs into mature DCs (mDCs). DCs live only up to a week but MOs and generated MQs can live up to a month in the given tissue. B cells inhibit T cell dependent immune responses in tumors (65).
AutoImmune Disorders:
The balance of IDO expression becomes necessary to prevent overactive immune response self-destruction, so modulation in tryptophan and NDA metabolisms maybe essential. When splenic IDO-expressing CD11b (+) DCs from tolerized animals applied, they suppressed the development of arthritis, increased the Treg/Th17 cell ratio, and decreased the production of inflammatory cytokines in the spleen (136).
The role of Nicotinamide prevention on type 1 diabetes and ameliorates multiple sclerosis in animal model presented with activities of NDAs stimulating GPCR109a to produce prostaglandins to induce IDO expression, then these PGEs and PGDs converted to the anti-inflammatory prostaglandin, 15d-PGJ(2) (137; 138; 139). Thus, these events promotes endogenous signaling mechanisms involving the GPCRs EP2, EP4, and DP1 along with PPARgamma. (137).
Modulating the immune response at non-canonical at canonocal pathway while keeping the non-canonical Nf-KB intact may help to mend immune disorders. As a result, the targeted blocking in canonical at associated kinase IKKβ and leaving non-canonocal Nf-kB pathway intact, DCs tips the balance towards immune supression. Hence, noncanonical NF-κB pathway for regulatory functions in DCs required effective IDO induction, directly or indirectly by endogenous ligand Kyn and negative regulation of proinflammatory cytokine production. As a result, this may help to treat autoimmune diseases such as rheumatoid arthritis, type 1 diabetes, inflammatory bowel disease, and multiple sclerosis, or allergy or transplant rejection.
While the opposite action needs to be taken during prevention of tumors, that is inhibition of non-canonical pathway. Inflammation induces not only relaxation of veins and lowering blood pressure but also stimulate coagulopathies that worsen the microenvironment and decrease survival rate of patients after radio or chemotherapies.Cancer Generating tumor vaccines and using adjuvants underway (140).
Clinical correlation and genetic responses also compared in several studies to diagnose and target the system for cancer therapies (127; 141; 131). The recent surveys on IDO expression and human cancers showed that IDO targeting is a candidate for cancer therapy since IDO expression recruiting Tregs, downregulates MHC class I and creating negative immune microenvironment for protection of development of tumors (125; 27; 142). Inhibition of IDO expression can make advances in immunotherapy and chemotherapy fields (143; 125; 131; 144).
IDO has a great importance on prevention of cancer development (126). There are many approaches to create the homeostasis of immune response by Immunotherapy. However, given the complexity of immune regulations, immunomodulation is a better approach to correct and relieve the system from the disease. Some of the current IDO targeted immunotherapy or immmunomodulations with RNA technology for cancer prevention (145; 146; 147; 148; 149; 150) or applied on human or animals (75; 151; 12; 115; 152; 9; 125) or chemical, (153; 154) or radiological (155). The targeted cell type in immune system generally DCs, monocytes (94)T cells (110; 156)and neutrophils (146; 157). On this paper, we will concentrate on DCvax on cancer treatments.
T-reg, regulatory T cells; Th, T helper; CTLA-4, cytotoxic T lymphocyte-associated antigen 4; TCR, T cell receptor; IDO, indoleamine 2,3-dioxygenase. (refernece: http://www.pnas.org/content/101/28/10398/suppl/DC)
IDO and the downstream enzymes in tryptophan pathway produce a series of immunosuppressive tryptophan metabolites that may lead into Tregs proliferation or increase in T cell apoptosis (62; 16; 27; 158), and some can affect NK cell function (159).
The interesting part of the mechanism is even without presence of IDO itself, downstream enzymes of IDO in the kynurenine tryptophan degradation still show immunosuppressive outcome (160; 73) due to not only Kyn but also TGFbeta stimulated long term responses. DC vaccination with IDO plausible (161) due to its power in immune response changes and longevity in the bloodstream for reversing the system for Th17 production (162).
Clinical Interventions are taking advantage of the DC’s central role and combining with enhancing molecules for induction of immunity may overcome tolerogenic DCs in tumors of cancers (163; 164).
The first successful application of DC vaccine used against advanced melanoma after loading DCs with tumor peptides or autologous cell lysate in presence of adjuvants keyhole limpet hematocyanin (KLH) (165). Previous animal and clinical studies show use of DCs against tumors created success (165; 166; 167) as well as some problems due to heterogeneity of DC populations in one study supporting tumor growth rather than diminishing (168).
DC vaccination applied onto over four thousand clinical trial but none of them used siRNA-IDO DC vaccination method. Clinical trials evaluating DCs loaded ex vivo with purified TAAs as an anticancer immunotherapeutic interventions also did not include IDO (Table from (169). This table presented the data from 30 clinical trials, 3 of which discontinued, evaluating DCs loaded ex vivo with TAAs as an anticancer immunotherapy for 12 types of cancer [(AML(1), Breast cancer (4), glioblastoma (1), glioma (2), hepatocellular carcinoma (1), hematological malignancies (1), melanoma (6), neuroblastoma sarcoma (2), NSCLC (1), ovarian cancer (3), pancreatic cancer (3), prostate cancer (10)] at phase I, II or I/II.
Tipping the balance between Treg and Th17 ratio has a therapeutic advantage for restoring the health that is also shown in ovarian cancer by DC vaccination with adjuvants (161). This rebalancing of the immune system towards immunogenicity may restore Treg/Th17 ratio (162; 170) but it is complicated. The stimulation of IL10 and IL12 induce Treg produce less Th17 and inhibiting CTL activation and its function (76; 171; 172) while animals treated with anti-TGFb before vaccination increase the plasma levels of IL-15 for tumor specific T cell survival in vivo (173; 174) ovarian cancer studies after human papilloma virus infection present an increase of IL12 (175).
Opposing signal mechanism downregulates the TGFb to activate CTL and Th1 population with IL12 and IL15 expression (162; 173). The effects of IL17 on antitumor properties observed by unique subset of CD4+ T cells (176) called also CD8+ T cells secrete even more IL17 (177).
Using cytokines as adjuvants during vaccination may improve the efficacy of vaccination since cancer vaccines unlike infections vaccines applied after the infection or disease started against the established adoptive immune response. Adjuvants are used to improve the responses of the given therapies commonly in immunotherapy applications as a combination therapy (178).
Enhancing cancer vaccine efficacy via modulation of the microenvironment is a plausible solution if only know who are the players. Several molecules can be used to initiate and lengthen the activity of intervention to stimulate IDO expression without compromising the mechanism (179). The system is complicated so generally induction is completed ex-vivo stimulation of DCs in cell lysates, whole tumor lysates, to create the microenvironment and natural stimulatory agents. Introduction of molecules as an adjuvants on genetic regulation on modulation of DCs are critical, because order and time of the signals, specific location/ tissue, and heterogeneity of personal needs (174; 138; 180). These studies demonstrated that IL15 with low TGFb stimulates CTL and Th1, whereas elevated TGFb with IL10 increases Th17 and Tregs in cancer microenvironments.
For example Ret-peptide antitumor vaccine contains an extracellular fragment of Ret protein and Th1 polarized immunoregulator CpG oligonucleotide (1826), with 1MT, a potent inhibitor of IDO, brought a powerful as well as specific cellular and humoral immune responses in mice (152).
The main idea of choosing Ret to produce vaccine in ret related carcinomas fall in two criterion, first choosing patients self-antigens for cancer therapy with a non-mutated gene, second, there is no evidence of genetic mutations in Ret amino acids 64-269. Demonstration of proliferating hemangiomas, benign endothelial tumors and often referred as hemangiomas of infancy appearing at head or neck, express IDO and slowly regressed as a result of immune mediated process.
After large scale of genomic analysis show insulin like growth factor 2 as the key regulator of hematoma growth (Ritter et al. 2003). We set out to develop new technology with our previous expertise in immunotherapy and immunomodulation (181; 182; 183; 184), correcting Th17/Th1 ratio (185), and siRNA technology (186; 187). We developed siRNA-IDO-DCvax. Patented two technologies “Immunomodulation using Altered DCs (Patent No: US2006/0165665 A1) and Method of Cancer Treatments using siRNA Silencing (Patent No: US2009/0220582 A1).
In melanoma cancer DCs were preconditioned with whole tumor lysate but in breast cancer model pretreatment completed with tumor cell lysate before siRNA-IDO-DCvax applied. Both of these studies was a success without modifying the autanticity of DCs but decreasing the IDO expression to restore immunegenity by delaying tumor growth in breast cancer (147) and in melanoma (188). Thus, our DCvax specifically interfere with Ido without disturbing natural structure and content of the DCs in vivo showed that it is possible to carry on this technology to clinical applications.
Furthermore, our method of intervention is more sophisticated since it has a direct interaction mechanism with ex-vivo DC modulation without creating long term metabolism imbalance in Trp/Kyn metabolite mechanisms since the action is corrective and non-invasive.
First, prevention of tumor development studies targeting non-enzymatic pathway initiated by pDCs conditioned with TGFbeta is specific to IDO1 (189).
Second, IDO upregulation in antigen presenting cells allowing metastasis show that most human tumors express IDO at high levels (123; 124).
Third, tolerogenic DCs secretes several molecules some of them are transforming growth factor beta (TGFb), interleukin IL10), human leukocyte antigen G (HLA-G), and leukemia inhibitory factor (LIF), and non-secreted program cell death ligand 1 (PD-1 L) and IDO, indolamine 2.3-dioxygenase, which promote tumor tolerance. Thus, we took advantage of DCs properties and Ido specificity to prevent the tolerogenicity with siRNA-IDO DC vaccine in both melanoma and breast cancer.
Fourth, IDO expression in DCs make them even more potent against tumor antigens and create more T cells against tumors. IDOs are expressed at different levels by both in broad range of tumor cells and many subtypes of DCs including monocyte-derived DCs (10), plasmacytoid DCs (142), CD8a+ DCs (190), IDO compotent DCs (17), IFNgamma-activated DCs used in DC vaccination. These DCs suppress immune responses through several mechanisms for induction of apoptosis towards activated T cells (156) to mediate antigen-specific T cell anergy in vivo (142) and for enhancement of Treg cells production at sites of vaccination with IDO-positive DCs+ in human patients (142; 191; 192; 168; 193; 194). If DCs are preconditioned with tumor lysate with 1MT vaccination they increase DCvax effectiveness unlike DCs originated from “normal”, healthy lysate with 1MT in pancreatic cancer (195). As a result, we concluded that the immunesupressive effect of IDO can be reversed by siRNA because Treg cells enhances DC vaccine-mediated anti-tumor-immunity in cancer patients.
Gene silencing is a promising technology regardless of advantages simplicity for finding gene interaction mechanisms in vitro and disadvantages of the technology is utilizing the system with specificity in vivo (186; 196). siRNA technology is one of the newest solution for the treatment of diseases as human genomics is only producing about 25,000 genes by representing 1% of its genome. Thus, utilizing the RNA open the doors for more comprehensive and less invasive effects on interventions. Thus this technology is still improving and using adjuvants. Silencing of K-Ras inhibit the growth of tumors in human pancreatic cancers (197), silencing of beta-catenin in colon cancers causes tumor regression in mouse models (198), silencing of vascular endothelial growth factor (VGEF) decreased angiogenesis and inhibit tumor growth (199).
Combining siRNA IDO and DCvax from adult stem cell is a novel technology for regression of tumors in melanoma and breast cancers in vivo. Our data showed that IDO-siRNA reduced tumor derived T cell apoptosis and tumor derived inhibition of T cell proliferation. In addition, silencing IDO made DCs more potent against tumors since treated or pretreated animals showed a delay or decreased the tumor growth (188; 147)
Clinical Trials:
First FDA approved DC-based cancer therapies for treatment of hormone-refractory prostate cancer as autologous cellular immunotherapy (163; 164). However, there are many probabilities to iron out for a predictive outcome in patients.
Table 2 demonstrates the current summary of clinical trials report. This table shows 38 total studies specifically Ido related function on cancer (16), eye (3), surgery (2), women health (4), obesity (1), Cardiovascular (2), brain (1), kidney (1), bladder (1), sepsis shock (1), transplant (1), nervous system and behavioral studies (4), HIV (1) (Table 4). Among these only 22 of which active, recruiting or not yet started to recruit, and 17 completed and one terminated.
Most of these studies concentrated on cancer by the industry, Teva GTC ( Phase I traumatic brain injury) Astra Zeneca (Phase IV on efficacy of CRESTOR 5mg for cardiovascular health concern), Incyte corporation (Phase II ovarian cancer) NewLink Genetics Corporation Phase I breast/lung/melanoma/pancreatic solid tumors that is terminated; Phase II malignant melanoma recruiting, Phase II active, not recruiting metastatic breast cancer, Phase I/II metastatic melanoma, Phase I advanced malignancies) , HIV (Phase IV enrolling by invitation supported by Salix Corp-UC, San Francisco and HIV/AIDS Research Programs).
Many studies based on chemotherapy but there are few that use biological methods completed study with IDO vaccine peptide vaccination for Stage III-IV non-small-cell lung cancer patients (NCT01219348), observational study on effect of biological therapy on biomarkers in patients with untreated hepatitis C, metastasis melanoma, or Crohn disease by IFNalpha and chemical (ribavirin, ticilimumab (NCT00897312), polymorphisms of patients after 1MT drug application in treating patients with metastatic or unmovable refractory solid tumors by surgery (NCT00758537), IDO expression analysis on MSCs (NCT01668576), and not yet recruiting intervention with adenovirus-p53 transduced dendric cell vaccine , 1MT , radiation, Carbon C 11 aplha-methyltryptophan- (NCT01302821).
Among the registered clinical trials some of them are not interventional but observational and evaluation studies on Trp/Kyn ratio (NCT01042847), Kyn/Trp ratio (NCT01219348), Kyn levels (NCT00897312, NCT00573300), RT-PCR analysis for Kyn metabolism (NCT00573300, NCT00684736, NCT00758537), and intrinsic IDO expression of mesenchymal stem cells in lung transplant with percent inhibition of CD4+ and CD8+ T cell proliferation toward donor cells (NCT01668576), determining polymorphisms (NCT00426894). These clinical trials/studies are immensely valuable to understand the mechanism and route of intervention development with the data collected from human populations
Future Actions for Molecular Dx and Targeted Therapies:
Viable tumor environment. Tumor survival is dependent upon an exquisite interplay between the critical functions of stromal development and angiogenesis, local immune suppression and tumor tolerance, and paradoxical inflammation. TEMs: TIE-2 expressing monocytes; “M2” TAMs: tolerogenic tumor-associated macrophages; MDSCs: myeloid-derived suppressor cells; pDCs: plasmacytoid dendritic cells; co-stim.: co-stimulation; IDO: indoleamine 2,3-dioxygenase; VEGF: vascular endothelial growth factor; EGF: epidermal growth factor; MMP: matrix metaloprotease; IL: interleukin; TGF-β: transforming growth factor-beta; TLRs: toll-like receptors. (reference: http://www.hindawi.com/journals/cdi/2012/937253/fig1/)
Current survival or response rate is around 40 to 50 % range. By using specific cell type, selected inhibition/activation sequence based on patient’s genomic profile may improve the efficacy of clinical interventions on cancer treatments. Targeted therapies for specific gene regulation through signal transduction is necessary but there are few studies with genomics based approach.
On the other hand, there are surveys, observational or evaluations (listed in clinical trials section) registered with www.clinicaltrials.gov that will provide a valuable short-list of molecules. Preventing stimulation of Ido1 as well as Tgfb-1gene expression by modulating receptor mediated phosphorylation between TGFb/SMAD either at Mad-Homology 1 (MH1) or Mad-Homology 1 (MH2) domains maybe possible (79; 82; 80). Within Smads are the conserved Mad-Homology 1 (MH1) domain, which is a DNA binding module contains tightly bound Zinc atom.
Smad MH2 domain is well conserved and one the most diverse protein-signal interacting molecule during signal transduction due to two important Serine residues located extreme distal C-termini at Ser-Val-Ser in Smad 2 or at pSer-X-PSer in RSmads (80). Kyn activated orphan G protein–coupled receptor, GPR35 with unknown function with a distinct expression pattern that collides with IDO sites since its expression at high levels of the immune system and the gut (63) (200; 63).
The first study to connect IDO with cancer shows that group (75). The directly targeting to regulate IDO expression is another method through modulating ISREs in its promoter with RNA-peptide combination technology. Indirectly, IDO can be regulated through Bin1 gene expression control over IDO since Bin1 is a negative regulator of IDO and prevents IDO expression. IDO is under negative genetic control of Bin1, BAR adapter–encoding gene Bin1 (also known as Amphiphysin2). Bin1 functions in cancer suppression since attenuation of Bin1 observed in many human malignancies (141; 201; 202; 203; 204; 205; 206) . Null Bin-/- mice showed that when there is lack of Bin1, upregulation of IDO through STAT1- and NF-kB-dependent expression of IDO makes tumor cells to escape from T cell–dependent antitumor immunity.
This pathway lies in non-enzymatic signal transducer function of IDO after stimulation of DCs by TGFb1. The detail study on Bin1 gene by alternative spicing also provided that Bin1 is a tumor suppressor. Its activities also depends on these spliced outcome, such as Exon 10, in muscle, in turn Exon 13 in mice has importance in role for regulating growth when Bin1 is deleted or mutated C2C12 myoblasts interrupted due to its missing Myc, cyclinD1, or growth factor inhibiting genes like p21WAF1 (207; 208).
On the other hand alternative spliced Exon12A contributing brain cell differentiation (209; 210). Myc as a target at the junction between IDO gene interaction and Trp metabolism. Bin1 interacts with Myc either early-dependent on Myc or late-independent on Myc, when Myc is not present. This gene regulation also interfered by the long term signaling mechanism related to Kynurenine (Kyn) acting as an endogenous ligand to AHR in Trp metabolite and TGFb1 and/or IFNalpha and IFNbeta up regulation of DCs to induce IDO in noncanonical pathway for NF-kB and myc gene activations (73; 74). Hence, Trp/Kyn, Kyn/Trp, Th1/Th17 ratios are important to be observed in patients peripheral blood. These direct and indirect gene interactions place Bin1 to function in cell differentiation (211; 212; 205).
Table 3 contains the microarray analysis for Kyn affect showed that there are 25 genes affected by Kyn, two of which are upregulated and 23 of them downregulated (100). This list of genes and additional knowledge based on studies creating the diagnostics panel with these genes as a biomarker may help to analyze the outcomes of given interventions and therapies. Some of these molecules are great candidate to seek as an adjuvant or co-stimulation agents. These are myc, NfKB at IKKA, C2CD2, CREB3L2, GPR115, IL2, IL8, IL6, and IL1B, mir-376 RNA, NFKB3, TGFb, RelA, and SH3RF1. In addition, Lip, Fox3P, CTLA-4, Bin1, and IMPACT should be monitored.
In addition, Table 4 presents the other possible mechanisms. The highlights of possible target/biomarkers are specific TLRs, conserved sequences of IDO across its homologous structures, CCR6, CCR5, RORgammat, ISREs of IDO, Jak, STAT, IRFs, MH1 and MH2 domains of Smads. Endothelial cell coagulation activation mechanism and pDC maturation or immigration from lymph nodes to bloodstream should marry to control not only IDO expression but also genesis of preferred DC subsets. Stromal mesenchymal cells are also activated by these modulation at vascular system and interferes with metastasis of cancer. First, thrombin (human factor II) is a well regulated protein in coagulation hemostasis has a role in cell differentiation and angiogenesis.
Protein kinase activated receptors (PARs), type of GPCRs, moderate the actions. Second, during hematopoietic response endothelial cells produce hematopoietic growth factors (213; 214). Third, components of bone marrow stroma cells include monocytes, adipocytes, and mesenchymal stem cells (215). As a result, addressing this issue will prevent occurrence of coagulapathologies, namely DIC, bleeding, thrombosis, so that patients may also improve response rate towards therapies. Personal genomic profiles are powerful tool to improve efficacy in immunotherapies since there is an influence of age (young vs. adult), state of immune system (innate vs. adopted or acquired immunity). Table 5 includes some of the current studies directly with IDO and indirectly effecting its mechanisms via gene therapy, DNA vaccine, gene silencing and adjuvant applications as an intervention method to prevent various cancer types.
CONCLUSION
IDO has a confined function in immune system through complex interactions to maintain hemostasis of immune responses. The genesis of IDO stem from duplication of bacterial IDO-like genes. Inhibition of microbial infection and invasion by depleting tryptophan limits and kills the invader but during starvation of trp the host may pass the twilight zone since trp required by host’s T cells. Thus, the host cells in these small pockets adopt to new microenvironment with depleted trp and oxygen poor conditions. Hence, the cell metabolism differentiate to generate new cellular structure like nodules and tumors under the protection of constitutively expressed IDO in tumors, DCs and inhibited T cell proliferation.
On the other hand, having a dichotomy in IDO function can be a potential limiting factor that means is that IDOs impact on biological system could be variable based on several issues such as target cells, IDO’s capacity, pathologic state of the disease and conditions of the microenvironment. Thus, close monitoring is necessary to analyze the outcome to prevent conspiracies since previous studies generated paradoxical results.
Current therapies through chemotherapies, radiotherapies are costly and effectiveness shown that the clinical interventions require immunotherapies as well as coagulation and vascular biology manipulations for a higher efficacy and survival rate in cancer patients. Our siRNA and DC technologies based on stem cell modulation will provide at least prevention of cancer development and hopefully prevention in cancer.
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The immune response mechanism is the holy grail of the human defense system for health. IDO, indolamine 2, 3-dioxygenase, is a key gene for homeostasis of immune responses and producing an enzyme catabolizing the first rate-limiting step in tryptophan degradation metabolism. The hemostasis of immune system is complicated. In this review, the properties of IDO such as basic molecular genetics, biochemistry and genesis will be discussed.
IDO belongs to globin gene family to carry oxygen and heme. The main function and genesis of IDO comes from the immune responses during host-microbial invasion and choice between tolerance and immunegenity. In human there are three kinds of IDOs, which are IDO1, IDO2, and TDO, with distinguished mechanisms and expression profiles. , IDO mechanism includes three distinguished pathways: enzymatic acts through IFNgamma, non-enzymatic acts through TGFbeta-IFNalpha/IFNbeta and moonlighting acts through AhR/Kyn.
The well understood functional genomics and mechanisms is important to translate basic science for clinical interventions of human health needs. In conclusion, overall purpose is to find a method to manipulate IDO to correct/fix/modulate immune responses for clinical applications.
The first part of the review concerns the basic science information gained overall several years that lay the foundation where translational research scientist should familiar to develop a new technology for clinic. The first connection of IDO and human health came from a very natural event that is protection of pregnancy in human. The focus of the translational medicine is treatment of cancer or prevention/delay cancer by stem cell based Dendritic Cell Vaccine (DCvax) development.
Table of Contents:
Abstract
1 Introduction: IDO gene encodes a heme enzyme
2 Location, location, location
3 Molecular genetics
4 Types of IDO:
4.1 IDO1,
4.2 IDO2,
4.3 IDO-like proteins
5 Working mechanisms of IDO
6 Infection Diseases and IDO
7. Conclusion
1. Indoleamine 2, 3-dioxygenase (IDO) gene encodes a heme enzyme
IDO is a key homeostatic regulator and confined in immune system mechanism for the balance between tolerance and immunity. This gene encodes indoleamine 2, 3-dioxygenase (IDO) – a heme enzyme (EC=1.13.11.52) that catalyzes the first rate-limiting step in tryptophan catabolism to N-formyl-kynurenine and acts on multiple tryptophan substrates including D-tryptophan, L-tryptophan, 5-hydroxy-tryptophan, tryptamine, and serotonin.
The basic genetic information describes indoleamine 2, 3-dioxygenase 1 (IDO1, IDO, INDO) as an enzyme located at Chromosome 8p12-p11 (5; 6) that active at the first step of the Tryptophan catabolism. The cloned gene structure showed that IDO contains 10 exons ad 9 introns (7; 8) producing 9 transcripts.
After alternative splicing only five of the transcripts encode a protein but the other four does not make protein products, three of transcripts retain intron and one of them create a nonsense code (7). Based on IDO related studies 15 phenotypes of IDO is identified, of which, twelve in cancer tumor models of lung, kidney, endometrium, intestine, two in nervous system, and one HGMD- deletion.
The specific cellular location of IDO is in cytosol, smooth muscle contractile fibers and stereocilium bundle. The expression specificity shows that IDO is present very widely in all cell types but there is an elevation of expression in placenta, pancreas, pancreas islets, including dendritic cells (DCs) according to gene atlas of transcriptome (9). Expression of IDO is common in antigen presenting cells (APCs), monocytes (MO), macrophages (MQs), DCs, T-cells, and some B-cells. IDO present in APCs (10; 11), due to magnitude of role play hierarchy and level of expression DCs are the better choice but including MOs during establishment of three DC cell subset, CD14+CD25+, CD14++CD25+ and CD14+CD25++ may increase the longevity and efficacy of the interventions.
IDO is strictly regulated and confined to immune system with diverse functions based on either positive or negative stimulations. The positive stimulations are T cell tolerance induction, apoptotic process, and chronic inflammatory response, type 2 immune response, interleukin-12 production (12). The negative stimulations are interleukin-10 production, activated T cell proliferation, T cell apoptotic process. Furthermore, there are more functions allocating fetus during female pregnancy; changing behavior, responding to lipopolysaccharide or multicellular organismal response to stress possible due to degradation of tryptophan, kynurenic acid biosynthetic process, cellular nitrogen compound metabolic process, small molecule metabolic process, producing kynurenine process (13; 14; 15).
IDO plays a role in a variety of pathophysiological processes such as antimicrobial and antitumor defense, neuropathology, immunoregulation, and antioxidant activity (16; 17; 18; 19).
A: Structure of human IDO2 gene and transcripts. Complete coding region is 1260 bps encoding a 420 aa polypeptide. Alternate splice isoforms lacking the exons indicated are noted. Hatch boxes represent a frameshift in the coding region to an alternate reading frame leading to termination. Black boxes represent 3′ untranslated regions. Nucleotide numbers, intron sizes, and positioning are based on IDO sequence files NW_923907.1 and GI:89028628 in the Genbank database. (reference: http://atlasgeneticsoncology.org/Genes/IDO2ID44387ch8p11.html)
Molecular genetics data from earlier findings based on reporter assay results showed that IDO promoter is regulated by ISRE-like elements and GAS-sequence at -1126 and -1083 region (20). Two cis-acting elements are ISRE1 (interferon sequence response element 1) and interferon sequence response element 2 (ISRE2).
Analyses of site directed and deletion mutation with transfected cells demonstrated that introduction of point mutations at these elements decreases the IDO expression. Removing ISRE1 decreases the effects of IFNgamma induction 50 fold and deleting ISRE1 at -1126 reduced by 25 fold (3). Introducing point mutations in conserved t residues at -1124 and -1122 (from T to C or G) in ISRE consensus sequence NAGtttCA/tntttNCC of IFNa/b inducible gene ISG4 eliminates the promoter activity by 24 fold (21).
ISRE2 have two boxes, X box (-114/1104) and Y Box 9-144/-135), which are essential part of the IFNgamma response region of major histocompatibility complex class II promoters (22; 23). When these were removed from ISRE2 or introducing point mutations at two A residues of ISRE2 at -111 showed a sharp decrease after IFNgamma treatment by 4 fold (3).
The lack of responses related to truncated or deleted IRF-1 interactions whereas IRF-2, Jak2 and STAT91 levels were similar in the cells, HEPg2 and ME180 (3). Furthermore, 748 bp deleted between these elements did not affect the IDO expression, thus the distance between ISRE1 and ISRE2 elements have no function or influence on IDO (3; 24)
B: Amino acid alignment of IDO and IDO2. Amino acids determined by mutagenesis and the crystal structure of IDO that are critical for catalytic activity are positioned below the human IDO sequence. Two commonly occurring SNPs identified in the coding region of human IDO2 are shown above the sequence which alter a critical amino acid (R248W) or introduce a premature termination codon (Y359stop).
4. There are three types of IDO in human genome:
IDO was originally discovered in 1967 in rabbit intestine (25). Later, in 1990 the human IDO gene is cloned and sequenced (7). However, its importance and relevance in immunology was not created until prevention of allocation of fetal rejection and founding expression in wide range of human cancers (26; 27).
There are three types of IDO, pro-IDO like, IDO1, and IDO2. In addition, another enzyme called TDO, tryptophan 2, 3, dehydrogenase solely degrade L-Trp at first-rate limiting mechanism in liver and brain.
4.1. IDO1:
IDO1 mechanism is the target for immunotherapy applications. The initial discovery of IDO in human physiology is protection of pregnancy (1) since lack of IDO results in premature recurrent abortion (28; 26; 29). The initial rate-limiting step of tryptophan metabolism is catalyzed by either IDO or tryptophan 2, 3-dioxygenase (TDO).
Structural studies of IDO versus TDO presenting active site environments, conserved Arg 117 and Tyr113, found both in TDO and IDO for the Tyr-Glu motif, but His55 in TDO replaced by Ser167b in IDO (30; 2). As a result, they are regulated with different mechanisms (1; 2) (30). The short-lived TDO, about 2h, responds to level of tryptophan and its expression regulated by glucorticoids (31; 32). Thus, it is a useful target for regulation and induced by tryptophan so that increasing tryptophan induces NAD biosynthesis. Whereas, IDO is not activated by the level of Trp presence but inflammatory agents with its interferon stimulated response elements (ISRE1 and ISRE2) in its (33; 34; 35; 36; 3; 10) promoter.
TDO promoter contains glucorticoid response elements (37; 38) and regulated by glucocorticoids and other available amino acids for gluconeogenesis. This is how IDO binds to only immune response cells and TDO relates to NAD biosynthesis mechanisms. Furthermore, TDO is express solely in liver and brain (36). NAD synthesis (39) showed increased IDO ubiquitous and TDO in liver and causing NAD level increase in rat with neuronal degeneration (40; 41). NAM has protective function in beta-cells could be used to cure Type1 diabetes (40; 42; 43). In addition, knowledge on NADH/NAD, Kyn/Trp or Trp/Kyn ratios as well as Th1/Th2, CD4/CD8 or Th17/Threg are equally important (44; 40).
Active site of IDO–PI complex. (A) Stereoview of the residues around the heme of IDO viewed from the side of heme plane. The proximal ligand H346 is H-bonded to wa1. The 6-propionate of the heme contacts with wa2 and R343 Nε. The wa2 is H-bonded to wa1, L388 O, and 6-propionate. Mutations of F226, F227, and R231 do not lose the substrate affinity but produce the inactive enzyme. Two CHES molecules are bound in the distal pocket. The cyclohexan ring of CHES-1 (green) contacts with F226 and R231. The 7-propionate of the heme interacts with the amino group of CHES-1 and side chain of Ser-263. The mutational analyses for these distal residues are shown in Table 1. (B) Top view of A by a rotation of 90°. The proximal residues are omitted. (http://www.pnas.org/content/103/8/2611/F3.expansion.html)
4.2. IDO2:
The third type of IDO, called IDO2 exists in lower vertebrates like chicken, fish and frogs (45) and in human with differential expression properties. The expression of IDO2 is only in DCs, unlike IDO1 expresses on both tumors and DCs in human tissues. Yet, in lower invertebrates IDO2 is not inhibited by general inhibitor of IDO, D-1-methyl-tryptophan (1MT) (46). Recently, two structurally unusual natural inhibitors of IDO molecules, EXIGUAMINES A and B, are synthesized (47). LIP mechanism cannot be switch back to activation after its induction in IDO2 (46).
Crucial cancer progression can continue with production of IL6, IL10 and TGF-beta1 to help invasion and metastasis. Inclusion of two common SNPs affects the function of IDO2 in certain populations. SNP1 reduces 90% of IDO2 catalytic activity in 50% of European and Asian descent and SNP2 produce premature protein through inclusion of stop-codon in 25% of African descent lack functional IDO2 (Uniport).
4.3. IDO-like proteins: The Origin of IDO:
Knowing the evolutionary steps will helps us to identify how we can manage the regulator function to protect human health in cancer, immune disorders, diabetes, and infectious diseases.
Bacterial IDO has two types of IDOs that are group I and group II IDO (48). These are the earliest version of the IDO, pro-IDO like, proteins with a quite complicated function. Each microorganism recognized by a specific set of receptors, called Toll-Like Receptors (TLR), to activate the IDO-like protein expression based on the origin of the bacteria or virus (49; 35). Thus, the genesis of human IDO originates from gene duplication of these early bacterial versions of IDO-like proteins after their invasion interactions with human host. IDO1 only exists in mammals and fungi.
Fungi also has three types of IDO; IDOa, IDO beta, and IDO gamma (50) with different properties than human IDOs, perhaps multiple IDO is necessary for the world’s decomposers.
All globins, haemoglobins and myoglobins are destined to evolve from a common ancestor, which is only 14-16kDa (51) length. Binding of a heme and being oxygen carrier are central to the enzyme mechanism of this family. Globins are classified under three distinct origins; a universal globin, a compact globin, and IDO-like globin(52). IDO like globin widely distributed among gastropodic mollusks (53; 51). The indoleamine 2, 3-dioxygenase 1–like “myoglobin” (Myb) was discovered in 1989 in the buccal mass of the abalone Sulculus diversicolor (54).
The conserved region between Myb and IDO-like Myb existed for at least 600 million years (53). Even though the splice junction of seven introns was kept intact, the overall homolog region between Myb and IDO is only about 35%.
No significant evolutionary relationship is found between them after their amino acid sequence of each exon is compared to usual globin sequences. This led the hint that molluscan IDO-like protein must have other functions besides carrying oxygen, like myoglobin. Alignment of S. cerevisiae cDNA, mollusk and vertebrate IDO–like globins show the key regions for controlling IDO or myoglobin function (55). These data suggest that there is an alternative pathways of myoglobin evolution. In addition, understanding the diversity of globin may help to design better protocols for interventions of diseases.
Mechanisms of IDO:
The dichotomy of IDO mechanism lead the discovery that IDO is more than an enzyme as a versatile regulator of innate and adaptive immune responses in DCs (66; 67; 68). Meantime IDO also involve with Th2 response and B cell mediated autoimmunity showing that it has three paths, short term (acute) based on enzymatic actions, long term (chronic) based on non-enzymatic role, and moonlighting relies of downstream metabolites of tryptophan metabolism (69; 70).
IFNgamma produced by DC, MQ, NK, NKT, CD4+ T cells and CD8+ T cells, after stimulation with IL12 and IL8. Inflammatory cytokine(s) expressed by DCs produce IFNgamma to stimulate IDO’s enzymatic reactions in acute response. Then, TDO in liver and tryptophan catabolites act through Aryl hydrocarbon receptor induction for prevention of T cell proliferation. This mechanism is common among IDO, IDO2 (expresses in brain and liver) and TDO expresses in liver) provide an acute response for an innate immunity (30). When the pDCs are stimulated with IFNgamma, activation of IDO is go through Jak, STAT signaling pathway to degrade Trp to Kyn causing Trp depletion. The starvation of tryptophan in microenvironment inhibits generation of T cells by un-read t-RNAs and induce apoptosis through myc pathway. In sum, lack of tryptophan halts T cell proliferation and put the T cells in apoptosis at S1 phase of cell division (71; 62).
The intermediary enzymes, functioning during Tryptophan degradation in Kynurenine (Kyn) pathway like kynurenine 3-hydroxylase and kynureninase, are also induced after stimulation with liposaccaride and proinflammatory cytokines (72). They exhibit their function in homeostasis through aryl-hydrocarbon receptor (AhR) induction by kynurenine as an endogenous signal (73; 74). The endogenous tumor-promoting ligand of AhR are usually activated by environmental stress or xenobiotic toxic chemicals in several cellular processes like tumorigenesis, inflammation, transformation, and embryogenesis (Opitz ET. Al, 2011).
Human tumor cells constitutively produce TDO also contributes to production of Kyn as an endogenous ligand of the AhR (75; 27). Degradation of tryptophan by IDO1/2 in tumors and tumor-draining lymph nodes occur. As a result, there are animal studies and Phase I/II clinical trials to inhibit the IDO1/2 to prevent cancer and poor prognosis (NewLink Genetics Corp. NCT00739609, 2007).
Systemic inflammation (like in sepsis, cerebral malaria and brain tumor) creates hypotension and IDO expression has the central role on vascular tone control (63). Moreover, inflammation activates the endothelial coagulation activation system causing coagulopathies on patients. This reaction is namely endothelial cell activation of IDO by IFNgamma inducing Trp to Kyn conversion. After infection with malaria the blood vessel tone has decreases, inflammation induce IDO expression in endothelial cells producing Kyn causing decreased trp, lower arterial relaxation, and develop hypotension (Wang, Y. et. al 2010). Furthermore, existing hypotension in knock out Ido mice point out a secondary mechanism driven by Kyn as an endogenous ligand to activate non-canonical NfKB pathway (63).
Another study also hints this “back –up” mechanism by a significant outcome with a differential response in pDCs against IMT treatment. Unlike IFN gamma conditioned pDC blocks T cell proliferation and apoptosis, methyl tryptophan fails to inhibit IDO activity for activating naïve T cells to make Tregs at TGF-b1 conditioned pDCs (77; 78).
The second role of the IDO relies on non-enzymatic action as being a signal molecule. Yet, IDO2 and TDO are devoid of this function. This role mainly for maintenance of microenvironment condition. DCs response to TGFbeta-1 exposure starts the kinase Fyn induce phosphorylation of IDO-associated immunoreceptor tyrosine–based inhibitory motifs (ITIMs) for propagation of the downstream signals involving non-canonical (anti-inflammatory) NF-kB pathway for a long term response. When the pDCs are conditioned with TGF-beta1 the signaling (68; 77; 78) Phospho Inositol Kinase3 (PIK-3)-dependent and Smad independent pathways (79; 80; 81; 82; 83) induce Fyn-dependent phosphorylation of IDO ITIMs. A prototypic ITIM has the I/V/L/SxYxxL/V/F sequence (84), where x in place of an amino acid and Y is phosphorylation sites of tyrosines (85; 86).
Smad independent pathway stimulates SHP and PIK3 induce both SHP and IDO phosphorylation. Then, formed SHP-IDO complex can induce non-canonical (non-inflammatory) NF-kB pathway (64; 79; 80; 82) by phosphorylation of kinase IKKa to induce nuclear translocation of p52-Relb towards their targets. Furthermore, the SHP-IDO complex also may inhibit IRAK1 (68). SHP-IDO complex activates genes through Nf-KB for production of Ido1 and Tgfb1 genes and secretion of IFNalpha/IFNbeta. IFNa/IFNb establishes a second short positive feedback loop towards p52-RelB for continuous gene expression of IDO, TGFb1, IFNa and IFNb (87; 68). However, SHP-IDO inhibited IRAK1 also activates p52-RelB. Nf-KB induction at three path, one main and two positive feedback loops, is also critical. Finally, based on TGF-beta1 induction (76) cellular differentiation occurs to stimulate naïve CD4+ T cell differentiation to regulatory T cells (Tregs). In sum, TGF-b1 and IFNalpha/IFNbeta stimulate pDCs to keep inducing naïve T cells for generation of Treg cells at various stages, initiate, maintain, differentiate, infect, amplify, during long-term immune responses (67; 66).
Moonlighting function of Kyn/AhR is an adaptation mechanism after the catalytic (enzymatic) role of IDO depletes tryptophan and produce high concentration of Kyn induce Treg and Tr1 cell expansion leading Tregs to use TGFbeta for maintaining this environment (67; 76). In this role, Kyn pathway has positive-feedback-loop function to induce IDO expression.
In T cells, tryptophan starvation induces Gcn2-dependent stress signaling pathway, which initiates uncharged Trp-tRNA binding onto ribosomes. Elevated GCN2 expression stimulates elF2alfa phosphorylation to stop translation initiation (88). Therefore, most genes downregulated and LIP, an alternatively initiated isoform of the b/ZIP transcription factor NF-IL6/CEBP-beta (89).
This mechanism happens in tumor cells based on Prendergast group observations. As a result, not only IDO1 propagates itself while producing IFNalpha/IFNbeta, but also demonstrates homeostasis choosing between immunegenity by production of TH17or tolerance by Tregs. This mechanism acts like a see-saw. Yet, tolerance also can be broken by IL6 induction so reversal mechanism by SOC-3 dependent proteosomal degradation of the enzyme (90). All proper responses require functional peripheral DCs to generate mature DCs for T cells to avoid autoimmunity (91).
Niacin (vitamin B3) is the final product of tryptophan catabolism and first molecule at Nicotinomic acid (NDA) Biosynthesis. The function of IDO in tryptophan and NDA metabolism has a great importance to develop new clinical applications (40; 42; 41). NAD+, biosynthesis and tryptophan metabolisms regulate several steps that can be utilize pharmacologically for reformation of healthy physiology (40).
IDO for protection in Microbial Infection with Toll-like Receptors
The mechanism of microbial response and infectious tolerance are complex and the origination of IDO based on duplication of microbial IDO (49). During microbial responses, Toll-like receptors (TLRs) play a role to differentiate and determine the microbial structures as a ligand to initiate production of cytokines and pro-inflammatory agents to activate specific T helper cells (92; 93; 94; 95). Uniqueness of TLR comes from four major characteristics of each individual TLR by ligand specificity, signal transduction pathways, expression profiles and cellular localization (96). Thus, TLRs are important part of the immune response signaling mechanism to initiate and design adoptive responses from innate (naïve) immune system to defend the host.
TLRs are expressed cell type specific patterns and present themselves on APCs (DCs, MQs, monocytes) with a rich expression levels (96; 97; 98; 99; 93; 100; 101; 102; 87). Induction signals originate from microbial stimuli for the genesis of mature immune response cells. Co-stimulation mechanisms stimulate immature DCs to travel from lymphoid organs to blood stream for proliferation of specific T cells (96). After the induction of iDCs by microbial stimuli, they produce proinflammatory cytokines such as TNF and IL-12, which can activate differentiation of T cells into T helper cell, type one (Th1) cells. (103).
Utilizing specific TLR stimulation to link between innate and acquired responses can be possible through simple recognition of pathogen-associated molecular patterns (PAMPs) or co-stimulation of PAMPs with other TLR or non-TLR receptors, or even better with proinflammatory cytokines. Some examples of ligand- TLR specificity shown in Table1, which are bacterial lipopeptides, Pam3Cys through TLR2 (92; 104; 105). Double stranded (ds) RNAs through TLR3 (106; 107), Lipopolysaccharide (LPS) through TLR4, bacterial flagellin through TLR5 (108; 109), single stranded RNAs through TLR7/8 (97; 98), synthetic anti-viral compounds imiquinod through TLR 7 and resiquimod through TLR8, unmethylated CpG DNA motifs through TLR9 (Krieg, 2000).
Then, the specificity is established by correct pairing of a TLR with its proinflammatory cytokines, so that these permutations influence creation and maintenance of cell differentiation. For example, leading the T cell response toward a preferred Th1 or Th2 response possible if the cytokines TLR-2 mediated signals induce a Th2 profile when combined with IL-2 but TLR4 mediated signals lean towards Th1 if it is combined with IL-10 or Il-12, (110; 111) (112).
TLR ligand
TLR
Reference
Lipopolysaccharide, LPS
TLR4
(96). (112).
Lipopeptides, Pam3Cys
TLR2
(92; 104; 105)
Double stranded (ds) RNAs
TLR3
(106; 107)
Bacterial flagellin
TLR5
(108; 109)
Single stranded RNAs
TLR7/8
(97; 98)
Unmethylated CpG DNA motifs
TLR9
(Krieg, 2000)
Synthetic anti-viral compounds imiquinod and resiquimod
TLR7 and TLR8
(Lee J, 2003)
Furthermore, if the DCs are stimulated with IL-6, DCs relieve the suppression of effector T cells by regulatory T cells (113).
The modification of IDO+ monocytes manage towards specific subset of T cell activation with specific TLRs are significantly important (94).
The type of cell with correct TLR and stimuli improves or decreases the effectiveness of stimuli. Induction of IDO in monocytes by synthetic viral RNAs (isRNA) and CMV was possible, but not in monocyte derived DCs or TLR2 ligand lipopeptide Pam3Cys since single- stranded RNA ligands target TLR7/8 in monocytes derive DCs only (Lee J, 2003). These data show that TLRs has ligand specificity, signal transduction pathways, expression profiles and cellular localization so design of experiments should follow these rules.
Conclusion:
Overall our purpose of this information is to find a method to manipulate IDO to correct/fix/modulate immune responses for clinical applications. This first part of the review concerns the basic science information gained overall several years that lay the foundation that translational research scientist should familiar to develop a new technology for clinic. The first connection of IDO and human health came from a very natural event that is protection of pregnancy in human. The focus of the translational medicine is treatment of cancer or prevention/delay cancer by stem cell based Dendritic Cell Vaccine (DCvax) development.
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