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01 Jun 2021

Understanding the immune response in COVID-19 recovery

Researchers have found that antibodies in people who have recovered from COVID-19 could contribute to protection from re-infection by activating white blood cells and mediating a variety of effector functions.

The research team write in Cell Reports Medicine that the capacity of antibodies to engage with immune cells via the Fc region is important in preventing and controlling many infectious diseases. The evolution of such antibodies during recovery from COVID-19 is largely unknown.

“Antibodies can mediate a myriad of potentially protective functions through the activation of surrounding white blood cells, called Fc-effector functions, which could help protect from re-infection. These functions are what we concentrated on in this study,” said Dr Wen Shi Lee, a postdoctoral researcher in the Kent Laboratory at the Doherty Institute.

“While Fc-effector functions can decline up to four to five months post COVID-19 infection, they are detectable longer post-infection when compared to neutralising antibodies,” said Samantha Davis, a PhD student in the Chung Laboratory at the Doherty Institute.

“That is, Fc-effector functions have a longer half-life compared to neutralising antibodies. Half-life refers to the time it takes for antibody functions to decline to 50 per cent of their maximal response. Thus, the longer the half-life, the more durable the response.”

The research team measured a number of different functions mediated by SARS-CoV-2 specific antibodies, including antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADP).

ADCC is a function where antibodies mediate the killing of infected cells and could play a role in stopping the spread of infection.

ADP is a key function where white blood cells (phagocytes) engulf and destroy viral particles and could play a role in clearing infectious virus from the lungs.
These findings offer a greater understanding of COVID-19 immunity and could potentially help infer how long immunity will last, either natural or vaccine induced.

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