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Archive for the ‘Diagnostic Immunology’ Category


Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

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.

 

References:

 

https://www.nature.com/articles/s41467-019-11370-y?elqTrackId=dc86e0c60f574542b033227afd0fdc8e

 

https://www.jci.org/articles/view/88879

 

https://www.nature.com/articles/nm.2353

 

https://diabetes.diabetesjournals.org/content/57/6/1470

 

https://www.sciencedirect.com/science/article/pii/S1550413115001047?via%3Dihub

 

https://www.sciencedirect.com/science/article/pii/S1550413115002326?via%3Dihub

 

https://www.sciencedirect.com/science/article/pii/S1931312814004636?via%3Dihub

 

https://www.nature.com/articles/nature15766

 

https://www.sciencedirect.com/science/article/pii/S1550413116000371?via%3Dihub

 

https://www.nature.com/articles/nm.2001

 

https://www.sciencedirect.com/science/article/abs/pii/S1550413118305047?via%3Dihub

 

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Newly Found Functions of B Cell

Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

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.

 

References:

 

https://www.cell.com/cell/fulltext/S0092-8674(19)30278-8

 

https://onlinelibrary.wiley.com/doi/full/10.1002/hon.2405

 

https://www.pnas.org/content/115/18/4743

 

https://onlinelibrary.wiley.com/doi/full/10.1111/all.12911

 

https://cshperspectives.cshlp.org/content/10/5/a028795

 

https://www.sciencedirect.com/science/article/abs/pii/S0049017218304955

 

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Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

Hepatitis B virus can cause serious, long-term health problems, such as liver disease and cancer, and can spread from mother-to-child during delivery. According to the latest estimates from the World Health Organization (WHO), approximately 257 million people in 2015 were living with the virus. Countries in Asia have a high burden of hepatitis B. There is no cure, and antiviral drugs used to treat the infection usually need to be taken for life.

 

To prevent infection, WHO recommends that all newborns receive their first dose of hepatitis B vaccine within 24 hours of delivery. Infants born to hepatitis B-infected mothers are also given protective antibodies called hepatitis B immune globulin (HBIG). However, mother-to-child transmission can still occur in women with high levels of virus in their blood, as well as those with mutated versions of the virus.

 

Tenofovir disoproxil fumarate (TDF), an antiviral drug commonly prescribed to treat hepatitis B infection, does not significantly reduce mother-to-child transmission of hepatitis B virus when taken during pregnancy and after delivery, according to a phase III clinical trial in Thailand funded by the National Institutes of Health. The study tested TDF therapy in addition to the standard preventative regimen — administration of hepatitis B vaccine and protective antibodies at birth — to explore the drug’s potential effects on mother-to-child transmission rates. The results appear in the New England Journal of Medicine.

 

The present study was conducted at 17 hospitals of the Ministry of Public Health in Thailand. It screened more than 2,500 women for eligibility and enrolled 331 pregnant women with hepatitis B. The women received placebo (163) or TDF (168) at intervals from 28 weeks of pregnancy to two months after delivery. All infants received standard hepatitis B preventatives given in Thailand, which include HBIG at birth and five doses of the hepatitis B vaccine by age 6 months (which differs from the three doses given in the United States). A total of 294 infants (147 in each group) were followed through age 6 months.

 

Three infants in the placebo group had hepatitis B infection at age 6 months, compared to zero infants in the TDF treatment group. Given the unexpectedly low transmission rate in the placebo group, the researchers concluded that the addition of TDF to current recommendations did not significantly reduce mother-to-child transmission of the virus.

 

According to the study, the clinical trial had enough participants to detect statistical differences if the transmission rate in the placebo group reached at least 12 percent, a rate observed in previous studies. Though the reasons are unknown, the researchers speculate that the lower transmission rate seen in the study may relate to the number of doses of hepatitis B vaccine given to infants in Thailand, lower rates of amniocentesis and Cesarean section deliveries in this study, or the lower prevalence of mutated viruses that result in higher vaccine efficacy in Thailand compared to other countries.

 

References:

 

https://www.nih.gov/news-events/news-releases/antiviral-drug-not-beneficial-reducing-mother-child-transmission-hepatitis-b-when-added-existing-preventatives

 

https://www.ncbi.nlm.nih.gov/pubmed/29514030

 

https://www.ncbi.nlm.nih.gov/pubmed/29514035

 

https://www.ncbi.nlm.nih.gov/pubmed/25240752

 

https://www.ncbi.nlm.nih.gov/pubmed/28188612

 

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Accelerating Clinical Next-Generation Sequencing: Navigating the Path to Reimbursement

Reporter: Aviva Lev-Ari, PhD, RN

Session at PMWC 2018 Silicon Valley

http://www.pmwcintl.com/sessionthemes-accelerating-clinical-next-generation-sequencing-2018sv/

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cell-free DNA (cfDNA) tests could become the ultimate “Molecular Stethoscope” that opens up a whole new way of practicing Medicine

 

Reporter: Aviva Lev-Ari, PhD, RN

The first commercial application of cfDNA sequencing debuted in 2011. New blood tests can identify Down’s syndrome and similar genetic conditions during the first months of pregnancy by checking the fetal DNA in the bloodstream of a pregnant woman. (Anywhere from 10 to 15 percent of the DNA in a pregnant woman’s blood comes from the placenta, which is genetically similar to the fetus.) These maternal blood tests are fast replacing less-accurate procedures, such as ultrasound plus blood analysis.

More recently, researchers have started looking at cfDNA to develop so-called liquid biopsies, which analyze a tumor’s genetic makeup or look for evidence of a cancer recurrence. Tumors often spill DNA into the blood as they grow and divide, and because they are usually riddled with mutations, their scrambled DNA is clearly different from that found in normal DNA fragments. The first liquid biopsy test was launched only three years ago; although they are not yet part of routine care, the field is growing quickly. One company says it will give liquid biopsy tests to one million people in the next five years, and another has raised nearly $1 billion for its studies.

A similar cfDNA method is being tested for newly transplanted organs, which are at risk of being rejected by the recipient’s immune system. Currently, transplant doctors check a transplanted organ’s health by performing repeated biopsies, which are expensive and invasive. After a transplant small amounts of donor DNA from the new heart or kidney, for example, circulate in the blood as part of the normal process of cell birth and death. If the host immune system attacks the foreign organ, the proportion of donor DNA increases as more and more foreign cells die. One company, CareDx, already sells a test that picks up on that change for people who have had kidney transplants.

The researchers invented a way to boost the signal by reducing human DNA in blood samples. Their spin-off company, Karius, launched a test earlier this year to identify bacteria, fungi, viruses or parasites in hospitalized patients. It can spot infections in organs that are too dangerous for biopsies, including the lung and the brain, Kertesz says—and it is most useful for people with mystery infections or who are too sick to endure a surgery.

cell-free DNA tests in the future include stroke, or autoimmune conditions such as lupus

 

SOURCE

One Test May Spot Cancer, Infections, Diabetes and More

Researchers are starting to diagnose more ailments using DNA fragments found in the blood

https://www.scientificamerican.com/article/one-test-may-spot-cancer-infections-diabetes-and-more/

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Reporter and Curator: Dr. Sudipta Saha, Ph.D.

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.

References:

https://blogs.scientificamerican.com/guest-blog/shortchanging-a-babys-microbiome/

https://www.ncbi.nlm.nih.gov/pubmed/23926244

https://www.ncbi.nlm.nih.gov/pubmed/26412384

https://www.ncbi.nlm.nih.gov/pubmed/25290507

https://www.ncbi.nlm.nih.gov/pubmed/25974306

https://www.ncbi.nlm.nih.gov/pubmed/24637604

https://www.ncbi.nlm.nih.gov/pubmed/22911969

https://www.ncbi.nlm.nih.gov/pubmed/25650398

https://www.ncbi.nlm.nih.gov/pubmed/27362264

https://www.ncbi.nlm.nih.gov/pubmed/27306663

http://www.mdpi.com/1099-4300/14/11/2036

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4464665/

https://www.ncbi.nlm.nih.gov/pubmed/24848255

https://www.ncbi.nlm.nih.gov/pubmed/26412384

https://www.ncbi.nlm.nih.gov/pubmed/28112736

http://ndnr.com/gastrointestinal/the-infant-microbiome-how-environmental-maternal-factors-influence-its-development/

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Multiple copies of the alpha tryptase gene drive Tryptase elevations may contribute to symptoms of dizziness and lightheadedness, skin flushing and itching, gastrointestinal complaints, chronic pain, and bone and joint problems

 

Reporter: Aviva Lev-Ari, PhD, RN

 

Monday, October 17, 2016

NIH scientists uncover genetic explanation for frustrating syndrome

Previously unexplained symptoms found associated with multiple copies of a single gene.

Other studies have indicated that four to six percent of the general public has high tryptase levels. While not all of these people experience symptoms, many do, raising the possibility that this mildly prevalent trait in some cases drives the symptoms, although how it does so remains unclear.

“This work suggests that multiple alpha tryptase gene copies might underlie health issues that affect a substantial number of people,” said NIAID Director Anthony S. Fauci, M.D. “Identifying one genetic cause for high tryptase opens the door for us to develop strategies for diagnosing and treating people carrying this genetic change.”

Previously,NIH’s National Institute of Allergy and Infectious Diseases (NIAID) researchers had observed that a combination of chronic and sometimes debilitating symptoms, such as hives, irritable bowel syndrome and overly flexible joints, runs in some families and is associated with high tryptase levels. Many affected family members with high tryptase also reported symptoms consistent with disorders of autonomic nervous system function (dysautonomia), including postural orthostatic tachycardia syndrome (POTS), which is characterized by dizziness, faintness and an elevated heartbeat when standing up.

SOURCE

https://www.nih.gov/news-events/news-releases/nih-scientists-uncover-genetic-explanation-frustrating-syndrome

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