Immunoglobulin A Plays a Key Role in Neutralising COVID-19

Immunoglobulin A (IgA) contributed to the neutralizing antibody response of wild-type COVID-19 virus, according to a study published in the Clinical and Translational Immunology journal.

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Conducted by researchers from Australia's Peter Doherty Institute for Infection and Immunity (Doherty Institute), the University of Melbourne and Walter and Eliza Hall Institute of Medical Research, the study published on Sunday compared different antibody responses to the virus in blood serum from 41 people who had recovered from COVID-19.

"In simple terms, we've deconstructed blood in our lab to measure its ability to smother the virus and to activate immune cells to kill SARS-CoV-2," said Samantha Davis, lead author and PhD researcher at the Doherty Institute.

"While we knew that IgG (Immunoglobulin G) is very important in the antibody response to clear the virus, we discovered that IgA also plays a key role in neutralizing it in most people," Davis noted.

Following COVID-19 infection, virus-specific antibodies are generated, which can both neutralize the virus and clear the infection. While much has been said about the importance of IgG antibodies for protection and control of the COVID-19 virus, the role of IgA antibodies has been relatively neglected throughout the pandemic.

Amy Chung, co-author and laboratory head of the Doherty Institute, said the new study opened door to new approaches for the development of future vaccines against COVID-19.

"Our findings are particularly important as IgA is the most abundant antibody present in the mucosa of our respiratory tract, which is the main route of virus infection," said Chung.

"This means if we're able to specifically make these antibodies at these vulnerable sites, we now know that we can induce a robust immune response to protect against the virus."

Researchers also pointed out that the convalescent IgA neutralizing response is highly heterogenous between individuals. Dissecting the IgA response in the context of vaccination and to variants of concern is essential to further understanding the antibody in a protective polyclonal antibody response.