A new study demonstrates that antibodies generated by the novel coronavirus react to other strains of coronavirus and vice versa, according to research in the journal Cell Reports.

The authors extensively characterize a selection of 10 antibodies covering all of the SARS-CoV structural proteins: spike, membrane, nucleocapsid, and envelope. While nearly all of the examined SARS-CoV antibodies displayed some level of reactivity to SARS-CoV-2, they found only partial cross-neutralization for the spike antibodies. Antibodies are blood proteins that are made by the immune system to protect against infection, in this case by a coronavirus.

The implications of this work are two-fold. Firstly, the authors established a set of antibodies with known reactivity to both SARS-CoV and SARS-CoV-2, which will allow further study of both viruses. Secondly, the authors provide empirical evidence of the high propensity for antibody cross-reactivity between distinct strains of human coronaviruses, critical information for designing diagnostic and vaccine strategies for COVID-19.

"Our finding has some important implications concerning immunity toward different strains of coronavirus infections, especially as these viruses continue to mutate," said senior author.

Given the speed of mutations - estimated at one to two per month - it's not surprising that an antibody generated from a virus 18 years ago provides a meager defense against the new coronavirus. Nonetheless, the author said the findings suggest more work needs to be done to determine the lasting effectiveness of COVID-19 vaccines.

"I don't think there is any one size-fits-all vaccine," theauthor said. "Although the vaccines coming out now may break the momentum of the virus and end the pandemic, they may not be the end game."

The senior author noted that researchers used individual antibody clones to test cross-reactivity, and that a body's normal immune system will generate many antibodies that are more likely to neutralize a wider series of targets on the mutating virus.

"I'm not personally terribly concerned," said lead author. "Emerging mutant viruses may have some propensity to escape certain antibodies raised by previous infection or vaccine.

"Every individual has a different immune system that will make a unique repertoire of different antibodies that bind to different places on the virus, so the chance of any one SARS-CoV-2 variant escaping from all of them is quite low."

The study also suggests that efforts to accurately discern a previous COVID-19 infection, by analyzing antibodies in blood, may be confounded by the presence of antibodies reacting to other strains of coronavirus including the common cold. Although this complicates diagnosis of older infections, researchers say the finding actually expands scientists' ability to study the biology and disease-causing effects of the SARS-CoV-2 virus since they know it reacts to antibodies of multiple strains of coronaviruses.

"It provides more tools to study the biology of this virus because we have very limited reagents available right now for SARS-CoV-2," the senior author said.

https://www.cell.com/cell-reports/fulltext/S2211-1247(21)00050-4

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