The virus cannot change that spot without breaking itself
SARS2-38 binds a conserved RBD epitope near the receptor-binding motif, enabling neutralization of variants carrying escape mutations that defeat other antibodies. Most neutralizing antibodies target mutable RBD or NTD regions, allowing variants to escape; SARS2-38's conserved epitope approach addresses this evolutionary pressure.
- SARS2-38 neutralized all tested variants of concern
- Binds conserved epitope near receptor-binding motif at positions K444 and G446
- Protected transgenic mice against B.1.351 variant in vivo
- Did not readily select for escape mutants in laboratory testing
- Research posted to bioRxiv preprint server, not yet peer-reviewed
Researchers identified a potent monoclonal antibody (SARS2-38) that neutralizes all tested SARS-CoV-2 variants of concern by binding a conserved epitope, offering potential therapeutic strategy against viral escape mutations.
A team of American researchers has identified a monoclonal antibody that appears to hold its ground against the evolving forms of SARS-CoV-2 that have been circulating globally. The finding, posted to the bioRxiv preprint server in late April 2021, describes work led by Dr. Laura VanBlargan at Washington University School of Medicine, who and her colleagues engineered a collection of antibodies designed to neutralize the virus by blocking its ability to attach to human cells.
The challenge the researchers were trying to solve is straightforward but urgent. Most of the monoclonal antibodies that have proven effective against COVID-19 bind to regions of the virus's spike protein that mutate easily—particularly the receptor-binding domain and the N-terminal domain. As the virus spreads and replicates, natural selection favors mutations in these exact spots, allowing new variants to slip past antibodies that once stopped them cold. Two monoclonal antibody treatments had already been authorized for emergency use against COVID-19, but their effectiveness against emerging variants was uncertain. The researchers wanted to find an antibody that could hit a target the virus couldn't easily change.
VanBlargan's team tested their panel of antibodies against both historical strains of SARS-CoV-2 and the variants of concern that were beginning to dominate in early 2021. They used laboratory techniques including focus-reduction neutralization tests and structural analysis with cryo-electron microscopy to understand exactly where each antibody attached to the virus and how well it worked. Two antibodies in particular showed promise: SARS2-02 and SARS2-38.
But the results diverged sharply. SARS2-02 bound to a region that included two specific amino acid positions—E484 and L452—that were mutating in circulating variants. When those mutations appeared, SARS2-02 lost much of its potency. SARS2-38, by contrast, bound to a different part of the spike protein, centered on positions K444 and G446. Crucially, this epitope—the specific region where the antibody makes contact—turned out to be conserved across all the variants the team tested. SARS2-38 neutralized them all.
The structural work revealed why. SARS2-38 recognizes an epitope positioned near the receptor-binding motif, a region that the virus cannot easily alter without losing its ability to infect cells in the first place. The antibody essentially targets a part of the virus that evolution has locked in place. In animal studies using transgenic mice, SARS2-38 retained its protective effect even against a virus carrying mutations from the B.1.351 variant, one of the most concerning strains at the time.
The researchers also found that SARS2-38 did not readily select for escape mutants when tested against authentic SARS-CoV-2 in the laboratory—meaning the virus did not quickly evolve resistance to it. This is a critical distinction. Some antibodies, even potent ones, can drive the emergence of resistant variants through the sheer pressure of selection. SARS2-38 appeared to avoid that trap.
The work points toward a new strategy for both vaccines and therapeutics: rather than targeting the most variable regions of the spike protein, developers could focus on conserved epitopes that the virus cannot change without sacrificing its own fitness. The researchers note that other human monoclonal antibodies in their panel also recognized this same conserved region, suggesting the target is robust and potentially exploitable across multiple therapeutic approaches.
It is important to note that this research has not yet been peer-reviewed. The findings are preliminary, posted to a preprint server where scientists share work before formal publication. The results are promising enough to warrant attention, but they remain unvetted by the broader scientific community. Still, the discovery offers a potential path forward in what has become an arms race between vaccine and therapeutic development on one side and viral evolution on the other.
Notable Quotes
SARS2-38 potently neutralized viruses encoding any of the above mutations, did not readily select for escape mutations with authentic SARS-CoV-2 strains and retained therapeutic activity in vivo against a virus containing substitutions of one of the key variants of concern— Study authors in bioRxiv paper
The Hearth Conversation Another angle on the story
Why does it matter that SARS2-38 binds to a conserved epitope rather than a mutable one?
Because the virus can't change that spot without breaking itself. Most antibodies target regions the virus can mutate away from. SARS2-38 targets a place the virus needs to keep intact to infect cells. It's like hitting a load-bearing wall instead of the wallpaper.
So the virus is trapped—it can't escape without losing function?
Exactly. The virus faces a choice: mutate and survive the antibody, or stay intact and get neutralized. With other antibodies, it just mutates. With SARS2-38, both paths lead to failure.
The researchers tested this in mice. Did the antibody actually prevent infection?
Yes. In transgenic mice, SARS2-38 protected against infection even from a virus carrying mutations from the B.1.351 variant, which was one of the most worrying strains at the time.
What about the other antibody they tested, SARS2-02?
It bound to a region with two positions that were already mutating in circulating variants. When those mutations appeared, the antibody lost potency. It's the cautionary tale in the study—proof that targeting mutable sites doesn't work long-term.
Is this ready to use as a treatment?
Not yet. This is preprint research, not peer-reviewed. But it suggests a direction: look for conserved epitopes, not the obvious variable ones. That could reshape how we design both vaccines and monoclonal antibody therapies going forward.
And if other antibodies also recognize this same conserved region?
Then it's not a one-off discovery. It's a principle. Multiple therapeutic approaches could target the same vulnerability, which makes the strategy more robust.