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Posts Tagged ‘SARS-CoV-2 Entry Factors’


From AAAS Science News on COVID19: New CRISPR based diagnostic may shorten testing time to 5 minutes

Reporter: Stephen J. Williams, Ph.D.

 

 

 

 

 

 

 

 

 

A new CRISPR-based diagnostic could shorten wait times for coronavirus tests.

 

 

New test detects coronavirus in just 5 minutes

By Robert F. ServiceOct. 8, 2020 , 3:45 PM

Science’s COVID-19 reporting is supported by the Pulitzer Center and the Heising-Simons Foundation.

 

Researchers have used CRISPR gene-editing technology to come up with a test that detects the pandemic coronavirus in just 5 minutes. The diagnostic doesn’t require expensive lab equipment to run and could potentially be deployed at doctor’s offices, schools, and office buildings.

“It looks like they have a really rock-solid test,” says Max Wilson, a molecular biologist at the University of California (UC), Santa Barbara. “It’s really quite elegant.”

CRISPR diagnostics are just one way researchers are trying to speed coronavirus testing. The new test is the fastest CRISPR-based diagnostic yet. In May, for example, two teams reported creating CRISPR-based coronavirus tests that could detect the virus in about an hour, much faster than the 24 hours needed for conventional coronavirus diagnostic tests.CRISPR tests work by identifying a sequence of RNA—about 20 RNA bases long—that is unique to SARS-CoV-2. They do so by creating a “guide” RNA that is complementary to the target RNA sequence and, thus, will bind to it in solution. When the guide binds to its target, the CRISPR tool’s Cas13 “scissors” enzyme turns on and cuts apart any nearby single-stranded RNA. These cuts release a separately introduced fluorescent particle in the test solution. When the sample is then hit with a burst of laser light, the released fluorescent particles light up, signaling the presence of the virus. These initial CRISPR tests, however, required researchers to first amplify any potential viral RNA before running it through the diagnostic to increase their odds of spotting a signal. That added complexity, cost, and time, and put a strain on scarce chemical reagents. Now, researchers led by Jennifer Doudna, who won a share of this year’s Nobel Prize in Chemistry yesterday for her co-discovery of CRISPR, report creating a novel CRISPR diagnostic that doesn’t amplify coronavirus RNA. Instead, Doudna and her colleagues spent months testing hundreds of guide RNAs to find multiple guides that work in tandem to increase the sensitivity of the test.

In a new preprint, the researchers report that with a single guide RNA, they could detect as few as 100,000 viruses per microliter of solution. And if they add a second guide RNA, they can detect as few as 100 viruses per microliter.

That’s still not as good as the conventional coronavirus diagnostic setup, which uses expensive lab-based machines to track the virus down to one virus per microliter, says Melanie Ott, a virologist at UC San Francisco who helped lead the project with Doudna. However, she says, the new setup was able to accurately identify a batch of five positive clinical samples with perfect accuracy in just 5 minutes per test, whereas the standard test can take 1 day or more to return results.

The new test has another key advantage, Wilson says: quantifying a sample’s amount of virus. When standard coronavirus tests amplify the virus’ genetic material in order to detect it, this changes the amount of genetic material present—and thus wipes out any chance of precisely quantifying just how much virus is in the sample.

By contrast, Ott’s and Doudna’s team found that the strength of the fluorescent signal was proportional to the amount of virus in their sample. That revealed not just whether a sample was positive, but also how much virus a patient had. That information can help doctors tailor treatment decisions to each patient’s condition, Wilson says.

Doudna and Ott say they and their colleagues are now working to validate their test setup and are looking into how to commercialize it.

Posted in:

doi:10.1126/science.abf1752

Robert F. Service

Bob is a news reporter for Science in Portland, Oregon, covering chemistry, materials science, and energy stories.

 

Source: https://www.sciencemag.org/news/2020/10/new-test-detects-coronavirus-just-5-minutes

Other articles on CRISPR and COVID19 can be found on our Coronavirus Portal and the following articles:

The Nobel Prize in Chemistry 2020: Emmanuelle Charpentier & Jennifer A. Doudna
The University of California has a proud legacy of winning Nobel Prizes, 68 faculty and staff have been awarded 69 Nobel Prizes.
Toaster Sized Machine Detects COVID-19
Study with important implications when considering widespread serological testing, Ab protection against re-infection with SARS-CoV-2 and the durability of vaccine protection

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Miniproteins against the COVID-19 Spike protein may be therapeutic

Reporter: Stephen J. Williams, PhD

Computer-designed proteins may protect against coronavirus

At a Glance

  • Researchers designed “miniproteins” that bound tightly to the SARS-CoV-2 spike protein and prevented the virus from infecting human cells in the lab.
  • More research is underway to test the most promising of the antiviral proteins.

 

 

 

 

 

 

 

An artist’s conception of computer-designed miniproteins (white) binding coronavirus spikes. UW Institute for Protein Design

The surface of SARS-CoV-2, the virus that causes COVID-19, is covered with spike proteins. These proteins latch onto human cells, allowing the virus to enter and infect them. The spike binds to ACE2 receptors on the cell surface. It then undergoes a structural change that allows it to fuse with the cell. Once inside, the virus can copy itself and produce more viruses.

Blocking entry of SARS-CoV-2 into human cells can prevent infection. Researchers are testing monoclonal antibody therapies that bind to the spike protein and neutralize the virus. But these antibodies, which are derived from immune system molecules, are large and not ideal for delivery through the nose. They’re also often not stable for long periods and usually require refrigeration.

Researchers led by Dr. David Baker of the University of Washington set out to design synthetic “miniproteins” that bind tightly to the coronavirus spike protein. Their study was funded in part by NIH’s National Institute of General Medical Sciences (NIGMS) and National Institute of Allergy and Infectious Diseases (NIAID). Findings appeared in Science on September 9, 2020.

The team used two strategies to create the antiviral miniproteins. First, they incorporated a segment of the ACE2 receptor into the small proteins. The researchers used a protein design tool they developed called Rosetta blueprint builder. This technology allowed them to custom build proteins and predict how they would bind to the receptor.

The second approach was to design miniproteins from scratch, which allowed for a greater range of possibilities. Using a large library of miniproteins, they identified designs that could potentially bind within a key part of the coronavirus spike called the receptor binding domain (RBD). In total, the team produced more than 100,000 miniproteins.

Next, the researchers tested how well the miniproteins bound to the RBD. The most promising candidates then underwent further testing and tweaking to improve binding.

Using cryo-electron microscopy, the team was able to build detailed pictures of how two of the miniproteins bound to the spike protein. The binding closely matched the predictions of the computational models.

Finally, the researchers tested whether three of the miniproteins could neutralize SARS-CoV-2. All protected lab-grown human cells from infection. Candidates LCB1 and LCB3 showed potent neutralizing ability. These were among the designs created from the miniprotein library. Tests suggested that these miniproteins may be more potent than the most effective antibody treatments reported to date.

“Although extensive clinical testing is still needed, we believe the best of these computer-generated antivirals are quite promising,” says Dr. Longxing Cao, the study’s first author. “They appear to block SARS-CoV-2 infection at least as well as monoclonal antibodies but are much easier to produce and far more stable, potentially eliminating the need for refrigeration.”

Notably, this study demonstrates the potential of computational models to quickly respond to future viral threats. With further development, researchers may be able to generate neutralizing designs within weeks of obtaining the genome of a new virus.

—by Erin Bryant

Source: https://www.nih.gov/news-events/nih-research-matters/computer-designed-proteins-may-protect-against-coronavirus

Original article in Science

De novo design of picomolar SARS-CoV-2 miniprotein inhibitors

 

  1. View ORCID ProfileLongxing Cao1,2
  2. Inna Goreshnik1,2
  3. View ORCID ProfileBrian Coventry1,2,3
  4. View ORCID ProfileJames Brett Case4
  5. View ORCID ProfileLauren Miller1,2
  6. Lisa Kozodoy1,2
  7. Rita E. Chen4,5
  8. View ORCID ProfileLauren Carter1,2
  9. View ORCID ProfileAlexandra C. Walls1
  10. Young-Jun Park1
  11. View ORCID ProfileEva-Maria Strauch6
  12. View ORCID ProfileLance Stewart1,2
  13. View ORCID ProfileMichael S. Diamond4,7
  14. View ORCID ProfileDavid Veesler1
  15. View ORCID ProfileDavid Baker1,2,8,*

See all authors and affiliations

Science  09 Sep 2020:
eabd9909
DOI: 10.1126/science.abd9909

Abstract

Targeting the interaction between the SARS-CoV-2 Spike protein and the human ACE2 receptor is a promising therapeutic strategy. We designed inhibitors using two de novo design approaches. Computer generated scaffolds were either built around an ACE2 helix that interacts with the Spike receptor binding domain (RBD), or docked against the RBD to identify new binding modes, and their amino acid sequences designed to optimize target binding, folding and stability. Ten designs bound the RBD with affinities ranging from 100pM to 10nM, and blocked ARS-CoV-2 infection of Vero E6 cells with IC 50 values between 24 pM and 35 nM; The most potent, with new binding modes, are 56 and 64 residue proteins (IC 50 ~ 0.16 ng/ml). Cryo-electron microscopy structures of these minibinders in complex with the SARS-CoV-2 spike ectodomain trimer with all three RBDs bound are nearly identical to the computational models. These hyperstable minibinders provide starting points for SARS-CoV-2 therapeutics.

 

RESEARCH ARTICLE

De novo design of picomolar SARS-CoV-2 miniprotein inhibitors

  1. View ORCID ProfileLongxing Cao1,2
  2. Inna Goreshnik1,2
  3. View ORCID ProfileBrian Coventry1,2,3
  4. View ORCID ProfileJames Brett Case4
  5. View ORCID ProfileLauren Miller1,2
  6. Lisa Kozodoy1,2
  7. Rita E. Chen4,5
  8. View ORCID ProfileLauren Carter1,2
  9. View ORCID ProfileAlexandra C. Walls1
  10. Young-Jun Park1
  11. View ORCID ProfileEva-Maria Strauch6
  12. View ORCID ProfileLance Stewart1,2
  13. View ORCID ProfileMichael S. Diamond4,7
  14. View ORCID ProfileDavid Veesler1
  15. View ORCID ProfileDavid Baker1,2,8,*

See all authors and affiliations

Science  09 Sep 2020:
eabd9909
DOI: 10.1126/science.abd9909

Abstract

Targeting the interaction between the SARS-CoV-2 Spike protein and the human ACE2 receptor is a promising therapeutic strategy. We designed inhibitors using two de novo design approaches. Computer generated scaffolds were either built around an ACE2 helix that interacts with the Spike receptor binding domain (RBD), or docked against the RBD to identify new binding modes, and their amino acid sequences designed to optimize target binding, folding and stability. Ten designs bound the RBD with affinities ranging from 100pM to 10nM, and blocked ARS-CoV-2 infection of Vero E6 cells with IC 50 values between 24 pM and 35 nM; The most potent, with new binding modes, are 56 and 64 residue proteins (IC 50 ~ 0.16 ng/ml). Cryo-electron microscopy structures of these minibinders in complex with the SARS-CoV-2 spike ectodomain trimer with all three RBDs bound are nearly identical to the computational models. These hyperstable minibinders provide starting points for SARS-CoV-2 therapeutics.

 

SARS-CoV-2 infection generally begins in the nasal cavity, with virus replicating there for several days before spreading to the lower respiratory tract (1). Delivery of a high concentration of a viral inhibitor into the nose and into the respiratory system generally might therefore provide prophylactic protection and/or therapeutic benefit for treatment of early infection, and could be particularly useful for healthcare workers and others coming into frequent contact with infected individuals. A number of monoclonal antibodies are in development as systemic treatments for COVID-19 (26), but these proteins are not ideal for intranasal delivery as antibodies are large and often not extremely stable molecules and the density of binding sites is low (two per 150 KDa. antibody); antibody-dependent disease enhancement (79) is also a potential issue. High-affinity Spike protein binders that block the interaction with the human cellular receptor angiotensin-converting enzyme 2 (ACE2) (10) with enhanced stability and smaller sizes to maximize the density of inhibitory domains could have advantages over antibodies for direct delivery into the respiratory system through intranasal administration, nebulization or dry powder aerosol. We found previously that intranasal delivery of small proteins designed to bind tightly to the influenza hemagglutinin can provide both prophylactic and therapeutic protection in rodent models of lethal influenza infection (11).

Design strategy

We set out to design high-affinity protein minibinders to the SARS-CoV-2 Spike RBD that compete with ACE2 binding. We explored two strategies: first we incorporated the alpha-helix from ACE2 which makes the majority of the interactions with the RBD into small designed proteins that make additional interactions with the RBD to attain higher affinity (Fig. 1A). Second, we designed binders completely from scratch without relying on known RBD-binding interactions (Fig. 1B). An advantage of the second approach is that the range of possibilities for design is much larger, and so potentially a greater diversity of high-affinity binding modes can be identified. For the first approach, we used the Rosetta blueprint builder to generate miniproteins which incorporate the ACE2 helix (human ACE2 residues 23 to 46). For the second approach, we used RIF docking (12) and design using large miniprotein libraries (11) to generate binders to distinct regions of the RBD surface surrounding the ACE2 binding site (Fig. 1 and fig. S1).

 

 

 

 

 

 

 

 

 

 

 

Download high-res image

Fig. 1 Overview of the computational design approaches.

(A) Design of helical proteins incorporating ACE2 helix. (B) Large scale de novo design of small helical scaffolds (top) followed by rotamer interaction field (RIF) docking to identify shape and chemically complementary binding modes.

For full article please  go to Science at https://science.sciencemag.org/content/early/2020/09/08/science.abd9909

 

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The Wide Variability in Reported COVID-19 Epidemiologic Data May Suggest That Personalized Omic Testing May Be Needed to Identify At-Risk Populations

Curator: Stephen J. Williams, PhD

I constantly check the Youtube uploads from Dr. John Campbell, who is a wonderful immunologist and gives daily reports on new findings on COVID-19 from the scientific literature.  His reporting is extremely insightful and easily understandable.  This is quite a feat as it seems the scientific field has been inundated with a plethora of papers, mostly reported clinical data from small retrospective studies, and many which are being put on preprint servers, and not peer reviewed.

It has become a challenge for many scientists, already inundated with expanding peer reviewed literature in their own fields, as well as the many requests to review papers, to keep up with all these COVID related literature.  Especially when it is up to the reader to do their own detailed peer review. So many thanks to people like Dr. Campbell who is an expert in his field for doing this.

However the other day he had posted a video which I found a bit disturbing, as a central theme of the video was that many expert committee could not find any reliable epidemiologic study concerning transmission or even incidence of the disease.  In all studies, as Dr. Campell alluded to, there is such a tremendous variability in the reported statistics, whether one is looking at percentage of people testing positive who are symptomatic, the percentage of asymptomatic which may be carriers, the transmission of the disease, and even the percentage of people who recover.

With all the studies being done it would appear that, even if a careful meta analysis were done using all available studies, and assuming their validity before peer review, that there would be a tighter consensus on some of these metrics of disease spread, incidence and prevalence.

Below is the video from Dr. Campbell and the topic is on percentage of asymptomatic carriers of the COVID-19 virus.  This was posted last week but later in this post there will be updated information and views by the WHO on this matter as well as other literature (which still shows to my point that this wide variability in reported data may be adding to the policy confusion with respect to asymptomatic versus symptomatic people and why genetic testing might be needed to further discriminate these cohorts of people.

 

Below is the video: 

From the Oxford Center for Evidence Based Medicine: COVID-19 Portal at https://www.cebm.net/oxford-covid-19-evidence-service/

“There is not a single reliable study to determine the number of asymptomatic infections”

And this is very troubling as this means there is no reliable testing resulting in any meaningful data.

As Dr. Campell says

” This is not good enough.  There needs to be some sort of coordinated research program it seems all ad hoc”

A few other notes from post and Oxford Center for Evidence Based Medicine:

  • Symptom based screening will miss a lot of asymptomatic and presymptomatic cases
  • Some asymptomatic cases will become symptomatic over next week (these people were technically presymptomatic but do we know the %?)
  • We need a population based antibody screening program
  • An Italian study of all 3,000 people in city of Vo’Euganeo revealed that 50-75% of those who tested positive were asymptomatic and authors concluded that asymptomatic represents “a formidable source of infection”; Dr. Campbell feels this was a reliable study
  • Another study from a Washington state nursing facility showed while 56% of positive cases were asymptomatic, 75% of these asymptomatic developed symptoms within a week. Symptom based screening missed half of cases.
  • Other studies do not follow-up on the positive cases to determine in presymptomatic
  • It also appears discrepancies between data from different agencies (like CDC, WHO) on who is shedding virus as different tests used (PCR vs antibody)

 

Recent Studies Conflict Concerning Asymptomatic, Presymtomatic and Viral Transmission

‘We don’t actually have that answer yet’: WHO clarifies comments on asymptomatic spread of Covid-19

From StatNews

A top World Health Organization official clarified on Tuesday that scientists have not determined yet how frequently people with asymptomatic cases of Covid-19 pass the disease on to others, a day after suggesting that such spread is “very rare.”

The clarification comes after the WHO’s original comments incited strong pushback from outside public health experts, who suggested the agency had erred, or at least miscommunicated, when it said people who didn’t show symptoms were unlikely to spread the virus.

Maria Van Kerkhove, the WHO’s technical lead on the Covid-19 pandemic, made it very clear Tuesday that the actual rates of asymptomatic transmission aren’t yet known.

Some of the confusion boiled down to the details of what an asymptomatic infection actually is, and the different ways the term is used. While some cases of Covid-19 are fully asymptomatic, sometimes the word is also used to describe people who haven’t started showing symptoms yet, when they are presymptomatic. Research has shown that people become infectious before they start feeling sick, during that presymptomatic period.

At one of the WHO’s thrice-weekly press briefings Monday, Van Kerkhove noted that when health officials review cases that are initially reported to be asymptomatic, “we find out that many have really mild disease.” There are some infected people who are “truly asymptomatic,” she said, but countries that are doing detailed contact tracing are “not finding secondary transmission onward” from those cases. “It’s very rare,” she said.

Source: https://www.statnews.com/2020/06/09/who-comments-asymptomatic-spread-covid-19/

 

Therefore the problems have been in coordinating the testing results, which types of tests conducted, and the symptomology results.  As Dr. Campbell previously stated it appears more ‘ad hoc’ than coordinated research program.  In addition, defining the presymptomatic and measuring this group have been challenging.

However, an alternative explanation to the wide variability in the data may be we need to redefine the cohorts of patients we are evaluating and the retrospective data we are collecting.  It is feasible that sub groups, potentially defined by genetic background may be identified and data re-evaluated based on personalized omic data, in essence creating new cohorts based on biomarker data.

From a Perspective in The Lancet about a worldwide proteomic effort (COVID-19 MS Coalition) to discover biomarkers related to COVID19 infection risk, by identifying COVID-related antigens.

The COVID-19 MS Coalition is a collective mass spectrometry effort that will provide molecular level information on SARS-CoV-2 in the human host and reveal pathophysiological and structural information to treat and minimise COVID-19 infection. Collaboration with colleagues at pace involves sharing of optimised methods for sample collection and data generation, processing and formatting for maximal information gain. Open datasets will enable ready access to this valuable information by the computational community to help understand antigen response mechanisms, inform vaccine development, and enable antiviral drug design. As countries across the world increase widespread testing to confirm SARS-CoV-2 exposure and assess immunity, mass spectrometry has a significant role in fighting the disease. Through collaborative actions, and the collective efforts of the COVID-19 MS Coalition, a molecular level quantitative understanding of SARS-CoV-2 and its effect will benefit all.

 

In an ACS Perspective below, Morteza Mahmoudi suggests a few possible nanobased technologies (i.e., protein corona sensor array and magnetic levitation) that could discriminate COVID-19-infected people at high risk of death while still in the early stages of infection.

Emerging Biomolecular Testing to Assess the Risk of Mortality from COVID-19 Infection

Morteza Mahmoudi*

Publication Date:May 7, 2020

 

Please see other articles on COVID-19 on our Coronavirus Portal at

An Epidemiological Approach Stephen J. Williams, PhD and Aviva Lev-Ari, PhD, RN Lead Curators – e–mail Contacts: sjwilliamspa@comcast.net and avivalev-ari@alum.berkeley.edu

https://pharmaceuticalintelligence.com/coronavirus-portal/an-epidemiological-approach-stephen-j-williams-phd-and-aviva-lev-ari-phd-rn-lead-curators-e-mail-contacts-sjwilliamspacomcast-net-and-avivalev-arialum-berkeley-edu/

and

https://pharmaceuticalintelligence.com/coronavirus-portal/

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Innate Immune Genes and Two Nasal Epithelial Cell Types: Expression of SARS-CoV-2 Entry Factors – COVID19 Cell Atlas

Reporter: Aviva Lev-Ari, PhD, RN

 

SARS-CoV-2 entry factors are highly expressed in nasal epithelial cells together with innate immune genes

Abstract

We investigated SARS-CoV-2 potential tropism by surveying expression of viral entry-associated genes in single-cell RNA-sequencing data from multiple tissues from healthy human donors. We co-detected these transcripts in specific respiratory, corneal and intestinal epithelial cells, potentially explaining the high efficiency of SARS-CoV-2 transmission. These genes are co-expressed in nasal epithelial cells with genes involved in innate immunity, highlighting the cells’ potential role in initial viral infection, spread and clearance. The study offers a useful resource for further lines of inquiry with valuable clinical samples from COVID-19 patients and we provide our data in a comprehensive, open and user-friendly fashion at www.covid19cellatlas.org.

To further characterize specific epithelial cell types expressing ACE2, we evaluated ACE2 expression within the lung and airway epithelium. We found that, despite a low level of expression overall, ACE2 was expressed in multiple epithelial cell types across the airway, as well as in alveolar epithelial type II cells in the parenchyma, consistently with previous studies9,10,11. Notably, nasal epithelial cells, including two previously described clusters of goblet cells and one cluster of ciliated cells, show the highest expression among all investigated cells in the respiratory tree (Fig. 1b). We confirmed enriched ACE2 expression in nasal epithelial cells in an independent scRNA-seq study that includes nasal brushings and biopsies. The results were consistent; we found the highest expression of ACE2 in nasal secretory cells (equivalent to the two goblet cell clusters in the previous dataset) and ciliated cells (Fig. 1b).

In addition, scRNA-seq data from an in vitro epithelial regeneration system from nasal epithelial cells corroborated the expression of ACE2 in goblet/secretory cells and ciliated cells in air–liquid interface cultures (Extended Data Fig. 1). Notably, the differentiating cells in the air–liquid interface acquire progressively more ACE2 (Extended Data Fig. 1). The results also suggest that this in vitro culture system may be biologically relevant for the study of SARS-CoV-2 pathogenesis.

Coronavirus Entry Genes Highly Expressed in Two Nasal Epithelial Cell Types

Apr 23, 2020

staff reporter

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TEM of SARS-CoV-2 particles; Credit: NIAID-RML

This story has been updated to include information on a related study appearing in Cell.

NEW YORK – Two types of cells inside the nose express high levels of the genes encoding proteins the SARS-CoV-2 uses to enter cells, suggesting they are the likely entry points for the virus.

SARS-CoV-2, the virus that causes COVID-19, uses its spike protein to bind to cellular receptors in the human body. The virus relies on the ACE2 receptor protein and the TMPRSS2 protease to enter cells, but which cells are initially infected has been unclear.

An international team of researchers used single-cell RNA sequencing datasets put together by the Human Cell Atlas consortium to search for cell types that express both the ACE2 and TMPRSS2 genes. As they reported in Nature Medicine Thursday, they found a number of cells in different organs express the genes encoding these proteins, but they homed in on cells of the respiratory system, especially goblet cells and ciliated cells in the nose.

“Mucus-producing goblet cells and ciliated cells in the nose had the highest levels of both these [genes], of all cells in the airways,” first author Waradon Sungnak from the Wellcome Sanger Institute said in a statement. “This makes these cells the most likely initial infection route for the virus.”

Using the Human Cell Atlas dataset, Sungnak and his colleagues analyzed ACE2 and TMPRSS2 expression in a range of tissues, including not only respiratory tissue — previous analyses using immunohistochemistry had detected both ACE2 and TMPRSS2 in the nasal and bronchial epithelium — but also tissue from the eyes, digestive tract, muscle, and more.

ACE2 gene expression was generally low across the datasets analyzed, while TMPRSS2 was more broadly expressed, the researchers found. This suggested that ACE2 expression might be the limiting factor for viral entry in initial infections.

However, ACE2 was expressed in a number of epithelial cell types of respiratory tissues, and its expression was particularly high among goblet cells and ciliated cells of the nose. The researchers confirmed this finding using data from two other scRNA-seq studies.

Other genes often co-expressed alongside ACE2 in the respiratory system included ones involved in carbohydrate metabolism — possibly due to their role in goblet cell mucin synthesis — and those involved in innate and antiviral immune functions.

The ACE2 and TMPRSS2 genes were also expressed outside of the respiratory system, including by cells of the cornea and the lining of the intestine, which the researchers noted is in line with some clinical reports suggesting fecal shedding of the virus.

Where these viral entry receptor genes are expressed in the respiratory system could influence how transmissible a virus is. The researchers compared the tissue expression patterns of these viral receptor genes to those of receptor genes used by other coronaviruses and influenza viruses. The receptors used by highly infectious viruses like influenza were expressed more in the upper airway, while receptors for less infectious viruses like MERSCoV were expressed in the lower airway. This indicated to the researchers that the spatial distribution of the viral receptors may influence how transmissible a virus is.

“This is the first time these particular cells in the nose have been associated with COVID-19,” study co-author Martijn Nawijn from the University Medical Center Groningen and the HCA Lung Biological Network said in a statement. “The location of these cells on the surface of the inside of the nose make them highly accessible to the virus, and also may assist with transmission to other people.”

Another study that appeared as a preprint at Cell also used single-cell RNA-sequencing datasets from humans, nonhuman primates, and mice to examine where cells expressing both the ACE2 and TMPRSS2 genes are located. Those researchers, led by the Broad Institute’s Jose Ordovas-Montanes, found both genes were expressed among type II pneumocytes and ileal absorptive enterocytes as well as among nasal goblet secretory cells.

SOURCE

https://www.genomeweb.com/infectious-disease/coronavirus-entry-genes-highly-expressed-two-nasal-epithelial-cell-types?utm_source=Sailthru&utm_medium=email&utm_campaign=GWDN%20Thurs%20PM%202020-04-23&utm_term=GW%20Daily%20News%20Bulletin#.XqIbG1NKgdU

SOURCE for Original Research Study 

Sungnak, W., Huang, N., Bécavin, C. et al. SARS-CoV-2 entry factors are highly expressed in nasal epithelial cells together with innate immune genes. Nat Med (2020). https://doi.org/10.1038/s41591-020-0868-6

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