Scientists detect new ‘variant-proof’ Sars-CoV-2 antibody
Scientists broadly consider Covid-19 to be endemic across the world, behaving much like the flu, but they have also raised caution over Long Covid.
Researchers have identified a highly effective antibody that can neutralise a broad range of Sars-CoV-2 variants as well as related coronaviruses, offering hope for improved treatments and vaccines against Covid-19 and potential future pandemics.
Scientists broadly consider Covid-19 to be endemic across the world, behaving much like the flu, but they have also raised caution over the Long Covid conditions that infections continue to trigger and the permanent cloud that a dangerous mutation may yet be around the corner – making the latest discovery of significant value for public health.
The study, published in the journal Cell Reports Medicine, was led by researchers at the University of Texas at Austin and the University of North Carolina at Chapel Hill reports an antibody named SC27, which appears to plug the gap between vaccine-derived immunity and what is known as hybrid immunity. The latter is when people who have recovered from a natural infection and have also had a shot – and they tend to have the strongest protection.
While vaccine-induced antibodies typically targeted a small portion of the spike protein of the virus (which directly attaches to human cells), antibodies in those with hybrid immunity tended to target that spike protein more broadly.
SC27, to put it simply, is one of those antibodies that targets the virus more broadly, thus becoming better able to neutralise the pathogen even if it mutates.
“We found these antibodies are painting the entire spike, both the arc and the stalk of the spike protein, which looks a bit like an umbrella,” said co-corresponding author Greg Ippolito, who is a research associate professor in UT Austin’s department of Molecular Biosciences and one of the authors, according to a release by the university. “The immune system sees the entire spike and tries to neutralize it.”
The antibody was isolated from the blood of a person who had received an mRNA Covid-19 vaccine and later experienced a breakthrough infection. In laboratory tests, SC27 confirmed the hypothesis that it could neutralise variants at large: it potently neutralised all major Sars-CoV-2 variants, including recent Omicron strains that have largely evaded existing antibody treatments.
It even neutralised the original Sars virus from 2003 and several bat and pangolin coronaviruses that could potentially spark future outbreaks.
The implication
Last month, the World Health Organization said in a release that even though it has been more than 12 months since Covid-19 was declared to no longer be a public health emergency, the virus has remained in circulation all-year-round and triggered a summer wave in Europe, with “the percentage of patients with respiratory illness who have Sars-CoV-2 in primary care increasing 5-fold in the last 8 weeks, and the percentage of patients hospitalised with Covid-19 having increased as well”.
“Getting an updated Covid-19 vaccine remains an extremely effective tool to reduce both hospitalisations and deaths in high-risk individuals, which includes people who are older or immune-compromised, those with multiple underlying medical conditions, pregnant women, and health personnel who may be easily exposed,” the UN health body said in a statement on August 8, and added that this also offers greater protection against Long Covid --- a set of long-term health effects like brain fog and cardiovascular issues long before the coronavirus has been cleared from the body.
The researcher in the latest paper also note that the continuing emergence of Sars-CoV-2 variants, coupled with abundant zoonotic reservoirs — or animals that host the virus and let it evolve --- of preemergent sarbecoviruses (the larger family of coronaviruses to which Sars-CoV-2 belongs) highlights the need for a deep understanding of how such pathogens can be wholly targeted.
The mechanism
SC27’s wide potential comes from being able to target the specific region on the spike protein that has remained largely unchanged as Sars-CoV-2 has evolved, the study reported.
The researchers used advanced imaging techniques to visualise exactly how SC27 attaches to the virus. They found it binds in a way that forms an unusually stable connection, which may explain its high potency.
Notably, SC27 exhibited an extremely strong binding affinity to the spike protein, surpassing that of all other known human antibodies against Sars-CoV-2, including those previously approved for clinical use.
When given to mice before infection with Sars-CoV-2, SC27 prevented the virus from replicating in the lungs.
The discovery of SC27 sheds new light on how hybrid immunity -- resulting from both vaccination and infection -- can produce exceptionally broad and potent antibodies against coronaviruses.
Over 60% of the antibody response in people with hybrid immunity originated from the initial exposure, the study found, whether from vaccination or infection. This “imprinting” effect helps explain why hybrid immunity often provides enhanced protection.
The team suggests that future vaccine strategies could potentially be designed to elicit SC27-like antibodies, which might offer broader protection against Sars-CoV-2 variants and related coronaviruses.
While the results are promising, the researchers caution that further studies are needed to determine if SC27 or similar antibodies could be developed into effective treatments or used to guide vaccine design.