A group of researchers, led by Brigham and Women's Hospital in the US, have discovered that humans generate antibodies targeting identical viral regions multiple times, despite being capable of producing a diverse range of antibodies. They believe that this finding may shed light on the numerous reinfection patterns observed during the Covid-19 pandemic.
The team identified "public epitopes" - specific viral protein locations where the antibody repeatedly binds - which suggested that a virus could mutate a single amino acid to infect a population of previously immune individuals.
"Our findings could help inform immune predictions and may change the way people think about immune strategies," said corresponding author Stephen J. Elledge, professor of Genetics at the Brigham.
According to the study published in the journal Science, researchers noted that previous studies had suggested that the immune system did not randomly target epitopes. Instead, they found evidence of recurrent antibody responses across individuals, indicating that people generate antibodies targeting the same epitope.
Antibodies act as "sniffer dogs" for the immune system, identifying and marking foreign invaders.
To conduct the study, the team analysed 569 blood samples from individuals in France, Peru, and the US using VirScan, a tool that can identify thousands of viral epitopes and provide a snapshot of a person's immunological history from a single blood drop.
The human antibody response commonly recognises public epitopes. The researchers identified 376 of these epitopes and discovered that the recognition occurs through germline-encoded amino acid binding (GRAB) motifs.
These motifs are regions of the antibodies that can effectively pick out specific amino acids. Rather than randomly selecting a target, human antibodies tend to concentrate on areas where these amino acids are available for binding, resulting in repeated binding to the same spots.
However, a small number of mutations can enable a virus to evade detection by these shared antibodies, enabling the virus to reinfect populations that were previously immune.
Lead author Ellen L. Shrock of the Elledge lab said that the research found an underlying architecture in the immune system that causes people from around the world to produce essentially the same antibodies that give the virus a limited number of targets to evade to reinfect individuals and evolve.
The team also noted that although it is more probable for people to produce antibodies targeting public epitopes, some individuals produce rarer antibodies that may provide more effective protection against reinfection.
The team believes these findings could have significant implications for the development of Covid-19 treatments, such as monoclonal antibodies, as well as for vaccine design. The study has been published in the journal Science.
(With inputs from PTI)
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