Differences in early antibody evolution can help predict the severity of Covid-19 in patients according to a study published in the Journal Cell .

The study published by Galit Alter, a member of the Ragon Institute of MGH, MIT and Harvard. suggests that Covid-19 outcomes may depend on the quality, not the quantity, of the patients’ antibody development and response.

The team of researchers profiled the antibody response to Covid-19 in 193 patients using Alter’s systems serology approach. These patients include patients with moderate to severe disease and patients who passed away from Covid-19.

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Defective IgG evolution

Though all patients developed an immune response to Covid-19, the way the antibodies developed, or evolved, differed between the three groups. The antibodies was never fully evolved in patients who succumbed to the infection.

“There was a significant defect in the development of IgG antibodies, which may be essential in the early control and elimination of the virus,” Alter said. “Here, we were able to see the global impact of this defective IgG evolution, resulting in a compromised ability to promote essential viral clearing immune functions.”

Antibodies can both block the infection and lead the immune system to kill the infected cells in a mature immune response. In order to direct the immune system to kill infected cells, antibodies attach to the Fc-receptor, a docking site specific to antibodies that are found on all immune cells, as per the report

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Without strongly binding to the Fc-receptor, antibodies be unable to grab and destroy the virus following infection.

Compared to patients who survived the infection, antibodies never fully developed to strongly bind to the Fc-receptors in patients who did not survive the infection.

S2-domain

Alter’s research team led by Tomer Zohar also found that survivors’ immune systems could recognise and target an area of the SARS-CoV-2 spike protein known as the S2-domain.

“The S2 domain is found in other coronaviruses that infect humans, so patients whose antibodies can target it may have pre-existing immunity to the S2 domain because of exposure to other, common coronaviruses,” explained an official release.

Patents may have a preexisting immunity with antibodies that can recognise S2 domains on different coronaviruses. This can generate killer antibodies faster and sooner following infection.

“If we can further understand the importance of cross-coronavirus immunity, researchers may be able to design vaccines able to counteract a much broader range of coronaviruses.” said Zohar