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UCSF Researchers Identify Genetic Mutation That Promotes an Asymptomatic Response in Humans to COVID-19 Infection

Apr 12, 2023 | Laboratory News, Laboratory Testing, Molecular Diagnostics, Genetic Testing, Whole Gene Sequencing, Precision Medicine

Understanding why some people display no symptoms during a COVID-19 infection could lead to new precision medicine genetic tests medical labs could use to identify people with the mutated gene

New research from the University of California San Francisco (UCSF) may explain why some people could get COVID-19 but never test positive on a clinical laboratory test or develop symptoms despite exposure to the SARS-CoV-2 coronavirus.

According to the UCSF study, variations in a specific gene in a system of genes responsible for regulating the human immune system appears to be the factor in why about 10% of those who become infected with the virus are asymptomatic.

These scientific insights did not receive widespread news coverage but will be of interest to clinical laboratory managers and pathologists who oversee SARS-CoV-2 testing in their labs.

Jill Hollenbach, PhD

“Some people just don’t have symptoms at all,” Jill Hollenbach, PhD (above), Professor of Neurology at UCSF’s Weill Institute for Neurosciences and lead researcher in the study, told NBC News. “There’s something happening at a really fundamental level in the immune response that is helping those people to just completely wipe out this infection.” Identifying a genetic reason why some people are asymptomatic could lead to new precision medicine clinical laboratory diagnostics for COVID-19. (Photo copyright: Elena Zhukova /University of California San Francisco.)

Fortunate Gene Mutation

According to the Centers for Disease Control and Prevention’s (CDC) COVID Data Tracker, as of April 5, 2023, a total of 104,242,889 COVID-19 cases have been reported in the United States. However, according to a CDC Morbidity and Mortality Weekly Report (MMWR), “Traditional methods of disease surveillance do not capture all COVID-19 cases because some are asymptomatic, not diagnosed, or not reported; therefore, [knowing the true] proportion of the population with SARS-CoV-2 antibodies (i.e., seroprevalence) can improve understanding of population-level incidence of COVID-19.”

Jill Hollenbach, PhD, lead researcher in the UCSF study and Professor of Neurology at UCSF’s Weill Institute for Neurosciences, runs the Hollenbach Lab at UCSF. The lab specializes in the study of two important elements in human immune response:

She also participates in the COVID-19 HLA and Immunogenetics Consortium, a group of academic researchers, clinical laboratory directors, journal editors, and others who examine the role of HLA variations in determining COVID-19 risk.

Hollenbach’s research identified an HLA variant—known as HLA-B*15:01—that causes the human immune system to react quickly to SARS-CoV-2 and “basically nuke the infection before you even start to have symptoms,” she told NPR.

“It’s definitely luck,” she added. “But, you know, this [gene] mutation is quite common. We estimate that maybe one in 10 people have it. And in people who are asymptomatic, that rises to one in five.”

The researchers published their findings on the medRxiv preprint server titled, “A Common Allele of HLA Mediates Asymptomatic SARS-CoV-2 Infection.” The UCSF study has not yet been peer-reviewed.

UCSF Study Methodology

“HLA variants are among the strongest reported associations with viral infections,” the UCSF study notes. So, the researchers theorized that HLA variations play a role in asymptomatic SARS-CoV-2 infections as well.

To conduct their study, shortly after the SARS-CoV-2 outbreak in 2020, the researchers recruited approximately 30,000 volunteer bone marrow donors from the National Marrow Donor Program to respond to periodic questions via a smartphone app or website. Because HLA variations can determine appropriate matches between donors and recipients, the database includes information about their HLA types.

Each week, respondents were asked to report if they had been tested for SARS-CoV-2. Each day, they were asked to report whether they had symptoms associated with COVID-19. “We were pretty stringent in our definition of asymptomatic,” Hollenbach told NBC News. “[The respondents couldn’t] even have a scratchy throat.”

The researchers eventually identified a cohort of 1,428 people who had tested positive for SARS-CoV-2 between February 2020 and April 30, 2021, before vaccines were widely available. Among these individuals, 136 reported no symptoms for two weeks before or two weeks after a positive test.

“Overall, one in five individuals (20%) who remained asymptomatic after infection carried HLA-B*15:01, compared to 9% among patients reporting symptoms,” the researchers wrote in their medRxiv preprint. Study participants with two copies of the gene were more than eight times more likely to be asymptomatic.

The UCSF researchers also looked at four other HLA variants and found none to be “significantly associated” with lack of symptoms. They confirmed their findings by reproducing the HLA-B association in two additional independent cohorts, one from an earlier study in the UK and the other consisting of San Francisco-area residents.

Individuals in the latter group had either tested positive for SARS-CoV-2 or reported COVID symptoms, and their DNA was analyzed to determine their HLA types.

Pre-existing T-Cell Immunity May Reduce Severity of COVID-19 Infection

The UCSF researchers also attempted to determine how HLA-B*15:01 plays a role in knocking out SARS-CoV-2 infections. They noted previous research that indicated previous exposure to seasonal coronaviruses, such as common cold viruses, could limit the severity of COVID-19. The scientists hypothesized that pre-existing T-cell immunity in HLA-B carriers may be the key.

The COVID-19 HLA and Immunogenetics Consortium website describes how HLA and T-cells work together to ward off disease. HLA “proteins are found on the surface of all cells except red-blood cells.” They’re “like windows into the inner workings of a cell,” and T-cells use the molecules to determine the presence of foreign proteins that are likely signs of infection. “Activated T-cells can kill infected cells, or activate B-cells, which produce antibodies in response to an infection,” the website explains.  

Hollenbach’s research team analyzed T-cells from pre-pandemic individuals and observed that in more than half of HLA-B carriers, the T-cells were reactive to a SARS-CoV-2 peptide. The scientists corroborated the hypothesis by examining crystal structures of the HLA-B*15:01 molecule in the presence of coronavirus spike peptides from SARS-CoV-2 and two other human coronaviruses: OC43-CoV and HKU1-CoV.

“Altogether, our results strongly support the hypothesis that HLA-B*15:01 mediates asymptomatic COVID-19 disease via pre-existing T-cell immunity due to previous exposure to HKU1-CoV and OC43-CoV,” the researchers wrote.

Can Genes Prevent COVID-19 Infections?

Meanwhile, researchers at The Rockefeller University in New York City are attempting to go further and see if there are mutations that prevent people from getting infected in the first place. NPR reported that they were seeking participants for a study seeking to identify so-called “superdodger” genes.

“You fill out a questionnaire online about your exposures to SARS-CoV-2,” explained Jean-Laurent Casanova, MD, PhD, professor, senior attending physician, and head of the St. Giles Laboratory of Human Genetics of Infectious Diseases at The Rockefeller University, who is leading the study.

Study participants identified as possibly having superdodger genes receive a kit designed to collect saliva samples, after which the researchers sequence the respondents’ genomes. “We hope that in a group of 2,000 to 4,000 people, some people will have genetic mutations that tell us why they’re resistant to infection,” Casanova told NPR.

All this genetic research is in very early stages. But results are promising and may lead to new precision medicine clinical laboratory tests for identifying people who are predisposed to having an asymptomatic response to COVID-19 infection. That in turn could help scientists learn how to moderate or even eliminate symptoms in those unfortunate people who suffer the typical symptoms of the disease.   

—Stephen Beale

Related Information:

A Common Allele of HLA Mediates Asymptomatic SARS-CoV-2 Infection

What People with ‘Super Immunity’ Can Teach Us about COVID and Other Viruses

So, You Haven’t Caught COVID Yet. Does That Mean You’re a Superdodger?

If You Haven’t Gotten COVID Yet, This Might Be Why

Trends in Number of COVID-19 Cases and Deaths in the US Reported to CDC, by State/Territory

UC San Francisco Researchers Discover Why Some People Are Asymptomatic When Infected with COVID-19

Seroprevalence of Infection-Induced SARS-CoV-2 Antibodies—United States, September 2021–February 2022

Two University of North Carolina School of Medicine Laboratories Develop Technique for Seeing How Proteins Change Shape In Vivo

Jun 17, 2022 | Laboratory Instruments & Laboratory Equipment, Laboratory News, Laboratory Pathology, Laboratory Resources, Laboratory Testing, Precision Medicine

UNC’s novel way to visualize the human proteome could lead to improved clinical laboratory tests along with the development of new therapies

Diagnostic testing based on proteomics is considered to be a field with immense potential in diagnostics and therapeutics. News of a research breakthrough into how scientists can visualize protein activity within cells will be of major interest to the pathologists, PhDs, and medical laboratory scientists who specialize in clinical laboratory testing involving proteins.

Proteins are essential to all life and to the growth, maintenance, and repair of the human body. So, a thorough understanding of how they function within living cells would be essential to informed medical decision-making as well. And yet, how proteins go about doing their work is not well understood.

That may soon change. Scientists at the University of North Carolina (UNC) School of Medicine have developed an imaging method that could provide new insights into how proteins alter their shapes within living cells. And those insights may lead to the development of new therapies and medical treatments.

Dubbed “binder-tag” by the UNC scientists, their new technique “allows researchers to pinpoint and track proteins that are in a desired shape or ‘conformation,’ and to do so in real time inside living cells,” according to a UNC Health news release.

Two labs in the UNC School of Medicine’s Department of Pharmacology collaborated to develop the binder-tag technique:

The scientists published their findings in the journal Cell, titled, “Biosensors Based on Peptide Exposure Show Single Molecule Conformations in Live Cells.”

Klaus Hahn PhD
 
“No one has been able to develop a method that can do, in such a generalizable way, what this method does. So, I think it could have a very big impact,” said lead author of the UNC study Klaus Hahn PhD (above), in the news release. “With this method we can see, for example, how microenvironmental differences across a cell affect, often profoundly, what a protein is doing,” he added. This research may enlarge scientists’ understanding of how the human proteome works and could lead to new medical laboratory tests and therapeutic drugs. (Photo copyright: UNC School of Medicine.)
 

How Binder-Tag Works

During their study, the UNC scientists developed binder-tag “movies” that allow viewers to see how the binder-tag technique enables the tracking of active molecules in living cells.

According to Cosmos:

  • The technique involves two parts: a fluorescent binder and a molecular tag that is attached to the proteins of interest.
  • When inactive, the tag is hidden inside the protein, but when the protein is ready for action it changes shape and exposes the tag.
  • The binder then joins with the exposed tag and fluoresces. This new fluorescence can easily be tracked within the cell.
  • Nothing else in the cell can bind to the binder or tag, so they only light up when in contact on the active protein.
  • This type of visualization will help researchers understand the dynamics of a protein in a cell.

“The method is compatible with a wide range of beacons, including much more efficient ones than the interacting beacon pairs required for ordinary FRET [fluorescence resonance energy transfer]. Binder-tag can even be used to build FRET sensors more easily. Moreover, the binder-tag molecules were chosen so that nothing in cells can react with them and interfere with their imaging role,” Hahn said in the news release.

“Only upon exposure can the peptide specifically interact with a reporter protein (the binder). Thus, simple fluorescence localization reflects protein conformation. Through direct excitation of bright dyes, the trajectory and conformation of individual proteins can be followed,” the UNC researchers wrote in Cell. “The simplicity of binder-tag can provide access to diverse proteins.”  

The UNC researchers’ binder-tag technique is a way to overcome the dire challenge of seeing tiny and hard-working proteins, Cosmos noted. Typical light microscopy does not enable a view of molecules at work. This paves the way for the new binder-tag technique, UNC pointed out.

“With this method, we can see, for example, how microenvironmental differences across a cell affect—and often profoundly—what a protein is doing,” Hahn said. “For a lot of protein-related diseases, scientists haven’t been able to understand why proteins start to do the wrong thing. The tools for obtaining that understanding just haven’t been available.”

More Proteins to Study

More research is needed before the binder-tag method can be used in diagnostics. Meanwhile, the UNC scientists intend to show how binder-tag can be applied to other protein structures and functions. 

“The human proteome has between 80,000 and 400,000 proteins, but not all at one time. They are expressed by 20,000 to 25,000 human genes. So, the human proteome has great promise for use in diagnostics, understanding disease, and developing therapies,” said Robert Michel, Editor-in-Chief of Dark Daily and its sister publication The Dark Report.

Medical scientists and diagnostics professionals will want to stay tuned to discover more about the tiny—though mighty—protein’s contributions to understanding diseases and patient treatment.     

—Donna Marie Pocius

Related Information:

Biosensors Based on Peptide Exposure Show Single Molecule Conformations in Live Cells

Powerful Technique Allows Scientists to Study How Proteins Change Shape Inside Cells

Watching Proteins Dance

Binder-Tag: A Versatile Approach to Probe and Control the Conformational Changes of Individual Molecules in Living Cells

Thomas Jefferson University Study Finds Critical Weakness in Commercially Manufactured Exome-Capture Test Kits Used by Some Medical Laboratories

Aug 22, 2014 | Digital Pathology, Instruments & Equipment, Laboratory Instruments & Laboratory Equipment, Laboratory News, Laboratory Operations, Laboratory Pathology, Laboratory Testing

The four exome test kits examined as part of this study failed to deliver quality results, particularly because they often missed some disease-causing mutations altogether

Human exome sequencing is gaining favor among medical laboratories wanting to use this information for clinical purposes. However, the accuracy of some exome-capture test kits available on the market today has come under question.

A team from the Thomas Jefferson University in Philadelphia surveyed the potential false-negative rate of mutations in 56 disease-causing genes produced by four different commercially available human exome-capture test kits. The researchers found that these test kits failed to deliver quality results, sometimes missing mutations altogether, noted a report published by Medical Daily. (more…)

Researchers at Stanford University and Intel Develop Silicon Microarray Chip Capable of Producing Clinical Pathology Laboratory Test Results in Minutes

Jan 16, 2013 | Instruments & Equipment, Laboratory Hiring & Human Resources, Laboratory Instruments & Laboratory Equipment, Laboratory Management and Operations, Laboratory News, Laboratory Operations, Laboratory Pathology, Management & Operations, Uncategorized

Pathologists and clinical laboratory managers take note—this peptide chip microarray may have a role in point-of-care testing

At the heart of a new point-of-care technology is a prototype silicon chip that contains up to 9,000 peptides and allows real-time analysis in just minutes. Researchers say this technology can significantly reduce the time-to-answer when compared to existing clinical laboratory testing technologies.

This new prototype silicon chip is an on silico peptide microarray. It could help researchers better understand how proteins interact in the body. In turn, that will lead to improved diagnoses of numerous diseases. (more…)

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