Researchers have recently discovered antibodies that can neutralize a range of SARS-CoV-2 variants and other coronaviruses.
They hope that their work, which appears in the journal Nature, may help with developing treatments for the current COVID-19 crisis, as well as potential future pandemics.
Antibodies are the human body’s defense mechanism against unfamiliar substances such as bacteria and viruses in the blood. Once generated, antibodies bind to the foreign substances, which are called antigens. The binding process triggers the body’s immune response and mobilizes other cells to fight the invading antigen.
Scientists can also make antibodies in a laboratory setting. Three monoclonal antibody-based therapies, which are designed to block the SARS-CoV-2 attachment to human cells, are currently available through emergency use authorization by the Food and Drug Administration (FDA). These are:
One of these, casirivimab plus imdevimab, has also received approval for use in the United Kingdom.
According to Dr. William Schaffner, 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.
Dr. Schaffner — who is a professor of medicine in the Division of Infectious Diseases at the Vanderbilt University School of Medicine in Nashville, TN — was not involved in the Nature study.
“[The monoclonal antibody treatment is] designed to prevent the evolution of the infection from a mild infection into a serious one,” he told Medical News Today during an interview. “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.”
However, some monoclonal antibodies lose their effectiveness as viruses mutate. On August 27, 2021, the FDA changed its authorization for one monoclonal antibody combination: bamlanivimab and etesevimab.
The FDA ruled that it may only be used in states, territories, and jurisdictions where data show that the combined frequency of variants resistant to it is less than or equal to 5%.
Antibodies with efficacy and breadth
Now, a large team of researchers working collaboratively has recognized that:
- SARS-CoV-2 will likely continue to evolve, enabling the virus to escape the grasp of antibody treatment.
- Other human coronaviruses will continue to evolve.
- Viruses can occasionally move from one species to another.
For those reasons, they write in their study, they wanted to work toward developing antibodies and vaccines “that are robust to viral evolution.”
To do that, the researchers studied a dozen anti-SARS-CoV-2 antibodies isolated from individuals who had previously contracted SARS-CoV-2 or severe acute respiratory syndrome (SARS-CoV). They looked for any that may be resistant to losing their effectiveness as viruses mutate and that work against a variety of respiratory viruses.
The researchers used deep mutational scanning. This is a cutting-edge technique that allows scientists to assess thousands of possible genetic variants. They also employed pan-sarbecovirus binding assays, in vitro selection of viral escape, and biochemical and structural analyses.
As they worked, the researchers looked for antibodies that latch onto a viral protein fragment called the receptor-binding domain (RBD). With SARS-CoV-2, the RBD is located on the coronavirus’s trademark spike protein that binds to receptors in the host cells. Antibodies that block the RBD can prevent the virus from entering cells.
SARS-CoV-2 gains entry to cells using a receptor called angiotensin-converting enzyme 2 (ACE2). The researchers explain that antibodies that target the ACE2 receptor-binding motif (RBM) typically have poor breadth across sarbecoviruses and are readily escaped by mutations.
However, the researchers did identify an RBM antibody called S2E12 that demonstrated breadth and that may be a high barrier to viral escape.
Another of the antibodies the researchers studied, called S2H97, bound well with all respiratory viruses and prevented SARS-CoV-2 infections in Syrian hamsters when the animals received it prophylactically 2 days before exposure to the virus.
Interviewed in an article in Nature about the study, co-first study author Tyler Starr — a biochemist at the Fred Hutchinson Cancer Research Center in Seattle — said: “That’s the coolest antibody that we described.”
Republished with permission[/vc_message]
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