The antibodies target portions of the SARS-CoV-2 spike protein that resist mutation, potentially leading to better treatments and vaccines
One challenge in the battle against COVID-19 is the emergence of SARS-CoV-2 variants, especially the Delta variant, which may be more resistant to neutralizing antibodies compared with the original coronavirus. But now, scientists led by researchers at the Fred Hutchinson Cancer Research Center (Fred Hutch) in Seattle say they have identified antibodies that could be broadly protective against multiple sarbecoviruses, the subgenus that contains SARS-CoV-2 as well as SARS-CoV-1, the virus responsible for the 2002-2004 severe acute respiratory syndrome (SARS) outbreak.
In “SARS-CoV-2 RBD Antibodies That Maximize Breadth and Resistance to Escape,” the researchers described how they compared 12 antibodies obtained from patients infected with either SARS-CoV-2 or SARS-CoV-1. They pointed to one antibody in particular—S2H97—that could lead to development of new vaccines and therapies against current and future variants. It might even protect against sarbecoviruses that have not yet been identified, they wrote.
Unsaid in the news release about these research findings is the fact that these particular antibodies could eventually become useful biomarkers for clinical laboratory tests designed to help physicians determine which patients have these antibodies—and the protection from infection they represent—and which do not.
So far, however, S2H97 has only been tested in hamsters. But results are promising.
“This antibody, which binds to a previously unknown site on the coronavirus spike protein, appears to neutralize all known sarbecoviruses—the genus of coronaviruses that cause respiratory infections in mammals,” said Jay Nix, PhD, an affiliate in Berkeley Lab’s Biosciences Area and Beamline Director of the Molecular Biology Consortium at Berkeley Lab’s Advanced Light Source (ALS), in a Berkeley Lab news release. “And, due to the unique binding site on mutation-resistant part of the virus, it may well be more difficult for a new strain to escape,” he added.
Scientists have long known that the SARS-CoV-2 virus uses the spike protein to attach to human cells. The federal Centers for Disease Control and Prevention (CDC) notes that the variants have mutations in their spike proteins that make some of them more transmissible.
The Delta variant, the CDC notes, was the predominant variant in the US as of August 28, 2021. It “has been shown to have increased transmissibility, potential reduction in neutralization by some monoclonal antibody treatments, and reduction in neutralization by post-vaccination sera,” the agency states.
The key to S2H97, the researchers wrote, is that it targets a portion of the spike protein that is common among sarbecoviruses, and that is likely to be resistant to mutations.
The researchers used a variety of techniques to analyze how the 12 antibodies bind to the virus. They “compiled a list of thousands of mutations in the binding domains of multiple SARS-CoV-2 variants,” Nature reported. “They also catalogued mutations in the binding domain on dozens of SARS-CoV-2-like coronaviruses that belong to a group called the sarbecoviruses. Finally, they assessed how all these mutations affect the 12 antibodies’ ability to stick to the binding domain.”
William Schaffner, MD (above), Professor of Preventive Medicine in the Department of Health Policy as well as Professor of Medicine in the Division of Infectious Diseases at the Vanderbilt University School of Medicine in Nashville, believes that “people who test positive for SARS-CoV-2 and who are at risk of progressing to severe disease—including those who are over the age of 65 years and those who have weakened immune systems—should talk with a doctor about receiving monoclonal antibody treatment,” Medical News Today reported. “[The monoclonal antibody treatment is] designed to prevent the evolution of the infection from a mild infection into a serious one,” he noted. “In other words, you’ve just [contracted the virus], but we can now give you a medication that will help prevent [you] being hospitalized and getting seriously ill.” (Photo copyright: Vanderbilt University.)
Earlier Antibody Treatment Receives an EUA from the FDA
In issuing the EUA for sotrovimab, the FDA cited “an interim analysis from a phase 1/2/3 randomized, double-blind, placebo-controlled clinical trial in 583 non-hospitalized adults with mild-to-moderate COVID-19 symptoms and a positive SARS-CoV-2 test result. Of these patients, 291 received sotrovimab and 292 received a placebo within five days of onset of COVID-19 symptoms.”
Among these patients, 21 in the placebo group were hospitalized or died compared with three who received the therapy, an 85% reduction.
“While preventive measures, including vaccines, can reduce the total number of cases, sotrovimab is an important treatment option for those who become ill with COVID-19 and are at high risk—allowing them to avoid hospitalization or worse,” stated Adrienne E. Shapiro, MD, PhD, of the Fred Hutchinson Cancer Research Center in a GSK news release. Shapiro was an investigator in the clinical trial.
The EUA allows use of sotrovimab in patients who have tested positive for SARS-CoV-2, have mild-to-moderate symptoms, and “who are at high risk for progression to severe COVID-19, including hospitalization or death. This includes, for example, individuals who are 65 years of age and older or individuals who have certain medical conditions.” It is not authorized for patients who are hospitalized or for those who require oxygen therapy.
The therapy was originally known as VIR-7831. The companies say they have developed a similar treatment, VIR-7832, with modifications designed to enhance T cell function against the disease.
The antibody, they wrote, targets a region of the SARS-CoV-1 spike protein that is “highly conserved” among sarbecoviruses. Clinical laboratory testing, they wrote, also indicated that the therapy was likely to be effective against known SARS-CoV-2 variants.
“Our distinctive scientific approach has led to a single monoclonal antibody that, based on an interim analysis, resulted in an 85% reduction in all-cause hospitalizations or death, and has demonstrated, in vitro, that it retains activity against all known variants of concern, including the emerging variant from India,” stated Vir Biotechnology CEO George Scangos, PhD, in the GSK news release. “I believe that sotrovimab is a critical new treatment option in the fight against the current pandemic and potentially for future coronavirus outbreaks, as well.”
Pathologists and clinical laboratory managers working with rapid molecular tests and antibody tests for COVID-19 will want to monitor the development of monoclonal antibody treatments, as well as further research studies that focus on these specific antibodies.
Might clinical laboratories soon be called on to conduct mass testing to find people who show little or no symptoms even though they are infected with the coronavirus?
Clinical laboratory managers understand that as demand for COVID-19 testing exceeds supplies, what testing is done is generally performed on symptomatic patients. And yet, it is the asymptomatic individuals—those who are shown to be infected with the SARS-CoV-2 coronavirus, but who experience no symptoms of the illness—who may hold the key to creating effective treatments and vaccinations.
So, as the COVID-19 pandemic persists, scientists are asking why some people who are infected remain asymptomatic, while others die. Why do some patients get severely ill and others do not? Researchers at the University of California San Francisco (UCSF) and Stanford University School of Medicine (Stanford Medicine) are attempting to answer these questions as they investigate viral transmission, masking, immunity, and more.
And pressure is increasing on researchers to find the answer. According to Monica Gandhi, MD, MPH, an infectious disease specialist and Professor of Medicine at UCSF, millions of people may be asymptomatic and unknowingly spreading the virus. Gandhi is also Associate Division Chief (Clinical Operations/Education) of the Division of HIV, Infectious Diseases, and Global Medicine at UCSF’s Zuckerberg San Francisco General Hospital and Trauma Center.
“If we did a mass testing campaign on 300 million Americans right now, I think the rate of asymptomatic infection would be somewhere between 50% and 80% of cases,” she told UCSF Magazine.
On a smaller scale, her statement was borne out. In a study conducted in San Francisco’s Mission District during the first six weeks of the city’s shelter-in-place order, UCSF researchers conducted SARS-CoV-2 reverse transcription-PCR and antibody (Abbott ARCHITECT IgG) testing on 3,000 people. Approximately 53% tested positive for COVID-19 but had no symptoms such as fever, cough, and muscle aches, according to data reported by Carina Marquez, MD, UCSF Assistant Professor of Medicine and co-author of the study, in The Mercury News.
Pandemic Control’s Biggest Challenge: Asymptomatic People
In an editorial in the New England Journal of Medicine (NEJM), Gandhi wrote that transmission of the virus by asymptomatic people is the “Achilles heel of COVID-19 pandemic control.”
In her article, Gandhi compared SARS-CoV-2, the coronavirus that causes COVID-19, to SARS-CoV-1, the coronavirus that caused the 2003 SARS epidemic. One difference lies in how the virus sheds. In the case of SARS-CoV-2, that takes place in the upper respiratory tract, but with SARS-CoV-1, it takes place in the lower tract. In the latter, symptoms are more likely to be detected, Gandhi explained. Thus, asymptomatic carriers of the coronavirus may go undetected.
“Viral loads with SARS-CoV-1, which are associated with symptom onset, peak a median of five days later than viral loads with SARS-CoV-2, which makes symptom-based detection of infection more effective in the case of SARS-CoV-1,” Gandhi wrote. “With influenza, persons with asymptomatic disease generally have lower quantitative viral loads in secretions from the upper respiratory tract than from the lower respiratory tract and a shorter duration of viral shedding than persons with symptoms, which decreases the risk of transmission from paucisymptomatic persons.”
Rick Wright (above), an insurance broker in Redwood City, Calif., was infected with the COVID-19 coronavirus while aboard a Diamond Princess Cruise. He underwent 40 days of isolation, and though he consistently tested positive for the coronavirus, he experienced no symptoms of the illness. “I never felt sick. Not a cough, wheezing, headache. Absolutely nothing,” he told Mercury News. (Photo copyright: The Mercury News.)
Stanford Studies Immune Responses in COVID-19 Patients
Meanwhile, scientists at the Stanford University School of Medicine were on their own quest to find out why COVID-19 causes severe disease in some people and mild symptoms in others.
“One of the great mysteries of COVID-19 infections has been that some people develop severe disease, while others seem to recover quickly. Now, we have some insight into why that happens,” Bali Pulendran, PhD, Stanford Professor of Pathology, Microbiology, and Immunology and Senior Author of the study in a Stanford Medicine news release.
The Stanford research suggested that three molecules—EN-RAGE, TNFSF14, and oncostatin-M—“correlated with disease and increased bacterial products in human plasma” of COVID-19 patients.
“Our multiplex analysis of plasma cytokines revealed enhanced levels of several proinflammatory cytokines and a strong association of the inflammatory mediators EN-RAGE, TNFSF14, and OSM with clinical severity of the disease,” the scientists wrote in Science.
Pulendran hypothesized that the molecules originated in patients’ lungs, which was the infection site.
“These findings reveal how the immune system goes awry during coronavirus infections, leading to severe disease and point to potential therapeutic targets,” Pulendran said in the news release, adding, “These three molecules and their receptors could represent attractive therapeutic targets in combating COVID-19.”
Clinical Laboratories May Do More Testing of Asymptomatic People
The research continues. In a televised news conference, President Trump said COVID-19 testing plays an important role in “preventing transmission of the virus.” Clearly this is true and learning why some people who are infected experience little or no symptoms may be key to defeating COVID-19.
Thus, as the nation reopens, clinical laboratories may want to find ways to offer COVID-19 testing beyond hospitalized symptomatic patients and people who show up at independent labs with doctors’ orders. As supplies permit, laboratory managers may want to partner with providers in their communities to identify people who are asymptomatic and appear to be well, but who may be transmitting the coronavirus.
‘Aerosol and Surface Stability’ study shows that the virus can remain infectious in aerosol form for hours and on surfaces for days
By now, clinical laboratory workers, microbiologists, and phlebotomists should be fully aware of the potential for transmission on surfaces of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the novel coronavirus that causes Coronavirus disease 2019 (COVID-19). The CDC’s latest Morbidity and Mortality Weekly Report revealed that the coronavirus “was identified on a variety of surfaces in cabins of both symptomatic and asymptomatic infected passengers up to 17 days after cabins were vacated on the Diamond Princess, but before disinfection procedures had been conducted,” the New York Post reported. That means the virus can survive on surfaces significantly longer than CDC previously believed.
But did you know a recent study published in the New England Journal of Medicine (NEJM) found that SARS-CoV-2 can also survive in the air for many hours, potentially allowing aerosolized transmission of the virus as well?
The NEJM study also showed that the stability of SARS-CoV-2 to survive on surfaces and in aerosolized form mirrors the stability of the SARS coronavirus (SARS-CoV) that caused the severe acute respiratory syndrome (SARS) outbreak of 2003.
This is critically important information for clinical laboratory professionals in open-space laboratories, phlebotomists collecting medical laboratory specimens, and frontline healthcare workers who come in direct contact with potentially infected patients. They should be aware of every potential COVID-19 transmission pathway.
Hospital infection control teams will be particularly
interested in the possibility of airborne transmission, as they often visit
infected patients and are tasked with tracking both the source of the infection
as well as individuals who may be exposed to sick patients.
The NEJM study, titled “Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1” was conducted by scientists at the National Institute of Allergy and Infectious Diseases (NIAID), an agency of the US Department of Health and Human Services (HHS), the Centers for Disease Control and Prevention (CDC), Princeton University, and University of California, Los Angeles. The researchers concluded that SARS-CoV-2 remains in the air “up to three hours post aerosolization.”
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They also found the virus was detectable for up to four
hours on copper and up to 24 hours on cardboard. The scientists concluded SARS-CoV-2
can remain on plastic and stainless-steel surfaces for two to three days,
though the amount of the virus on surfaces decreases over time.
“Our results indicate that aerosol and fomite transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days,” the study states. “These findings echo those with SARS-CoV-1, in which these forms of transmission were associated with nosocomial spread and super-spreading events, and they provide information for pandemic mitigation efforts.”
But Can COVID-19 Be Caught Through Air?
However, as noted in Wired, the researchers did not clearly state that infected persons can spread COVID-19 to others in the same airspace. Some experts have pointed out that there is a difference between a virus that can exist as an aerosol—defined as a liquid or solid suspended in gas under only limited conditions—and the measles virus, for example, which the CDC estimates “can live for up two hours in an airspace where the infected person has coughed or sneezed.”
“While the researchers tested how long the virus can survive
in aerosols suspended in the air, they didn’t actually sample the air around
infected people,” Wired noted. “Instead, they put the virus into a
nebulizer and puffed it into a rotating drum to keep it airborne. Then, they
tested how long the virus could survive in the air inside the drum.”
Neeltje van Doremalen, PhD, a research fellow at National Institutes of Health (NIH) and researcher at the NIAID’s Rocky Mountain Laboratories in Hamilton, Montana, who coauthored the NEJM study, cautioned against an overreaction to this latest research. On Twitter she wrote, “Important: we experimentally generated [COVID-19] aerosols and kept them afloat in a drum. This is not evidence of aerosol transmission.”
Nonetheless, the World House Organization (WHO) took note of the study’s findings and on March 16, 2020, announced it was considering “airborne precautions” for healthcare workers, CNBC reported in its coverage of a virtual press conference on March 16, 2020, led by Maria Van Kerkhove, MS, PhD, Technical Lead for WHO’s Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Task Force.
Van Kerkhove emphasized that health officials were
monitoring results from other studies investigating how environmental
conditions such as humidity, temperature, and ultraviolet light affect
the disease and its ability to live on different surfaces.
“When you do an aerosol-generating procedure like in a medical care facility, you have the possibility to what we call aerosolize these particles, which means they can stay in the air a little bit longer,” said Maria Van Kerkhove, MS, PhD (above), Technical Lead for WHO’s Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Task Force during a virtual press conference, CNBC reported. “It’s very important that healthcare workers take additional precautions when they’re working on patients and doing these procedures,” she added. [Photo copyright: World Health Organization/YouTube.)
To Be or Not to Be an Airborne Pathogen
Stanley Perlman, MD, PhD, Professor of Microbiology and Immunology at the University of Iowa, believes aerosol transmission ultimately will be found not to play a large role in COVID-19 transmission.
“I think the answer will be, aerosolization occurs rarely, but not never,” Perlman told STAT. “You have to distinguish between what’s possible and what’s actually happening.”
In an NEJM editorial, Perlman expanded on those thoughts. “Although specific anti-coronaviral therapies are still in development, we now know much more about how to control such infections in the community and hospitals, which should alleviate some of this fear,” he wrote. “Transmission of [SARS-CoV-2] probably occurs by means of large droplets and contact and less so by means of aerosols and fomites, on the basis of our experience with SARS-CoV and MERS-CoV. Public health measures, including quarantining in the community as well as timely diagnosis and strict adherence to universal precautions in healthcare settings, were critical in controlling SARS and MERS. Institution of similar measures will be important and, it is hoped, successful in reducing the transmission of [SARS-CoV-2].”
An NIH news release announcing the SARS-CoV-2 stability study highlighted two additional observations:
“If the viability of the two coronaviruses is
similar, why is SARS-CoV-2 resulting in more cases? Emerging evidence suggest
that people infected with SARS-CoV-2 might be spreading virus without
recognizing, or prior to recognizing, symptoms. That would make disease control
measures that were effective against SARS-CoV-1 less effective against its
successor.
In contrast to SARS-CoV-1, most secondary cases
of virus transmission of SARS-CoV-2 appear to be occurring in community
settings rather than healthcare settings. However, healthcare settings are also
vulnerable to the introduction and spread of SARS-CoV-2, and the stability of
SARS-CoV-2 in aerosols and on surfaces likely contributes to transmission of
the virus in healthcare settings.”
Clearly, the scientific community has not agreed on
aerosolization as a definite source of infection. Nevertheless, clinical
laboratory workers in settings where potential exposure to SARS-CoV-2 exists
should take precautions against airborne transmission until scientists can
definitively determine whether this latest coronavirus can be acquired through
the airborne transmission.
