Study links stronger antibody responses to more severe COVID-19

Sex, age, and severity of disease may be useful in identifying novel coronavirus (COVID-19) survivors who are likely to have high levels of antibodies that can protect against the disease, according to a new study by researchers at Johns Hopkins Bloomberg School of Public Health published in the Journal of Clinical Investigation.

For the study, funded by the National Institutes of Health, the researchers examined samples of plasma from the 126 recovered patients using several tests. These included tests of the plasma's ability in cell cultures to neutralize cell-to-cell infection with SARS-CoV-2, the virus that causes COVID-19, as well as commercial tests for levels of antibodies to the coronavirus's spike protein, the protein that studs the surface of coronavirus particles and allows the virus to attach to and infiltrate human cells.

The study found high variability in their antibody levels and their antibodies' ability to neutralize the COVID-19-causing coronavirus, SARS-CoV-2. Three factors were associated with stronger antibody responses: having been sick enough with COVID-19 to be hospitalized, being older, and being male.

According to the researchers, initial studies of recovered COVID-19 patients revealed a significant variability in their antibody responses to the virus. Some survivors had very weak responses that would likely be ineffective in helping new patients. The researchers in the new study said they looked for factors that might help explain some of that variability and guide clinicians to the patients most likely to have high levels of SARS-CoV-2 neutralizing antibodies.

Consistent with several prior studies, the researchers found considerable variability among the subjects in their spike-protein antibody levels and plasma coronavirus-neutralization potency. On average, the plasma of survivors who had been hospitalized with COVID-19 had markedly more anti-spike protein antibodies and neutralized the virus more effectively, suggesting that disease severity prompts a stronger immune response, the researchers said.

Older age and male sex, which prior studies in both China and Europe have shown are associated with more severe COVID-19, were also associated with stronger antibody responses, though these links were weaker than for hospitalization status, according to the study.

As part of their study, the researchers also tested study participants with commercial test kits and found that recovered COVID-19 patients who have strong neutralizing antibody responses also are very likely to have high levels of coronavirus anti-spike antibodies. This suggests that this type of test kit, which is relatively inexpensive, might be a good tool for identifying suitable plasma donors for clinical trials and treatments.

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