Antibodies are one of the most valuable tools of the immune system to fight foreign invaders. As expected from work with other coronaviruses, several studies have confirmed that, following infection with Sars-CoV-2, the immune system counteracts by producing antibodies against the spike protein, a molecule that the virus uses to dock itself to our cells and infect them. But the question of how long and how robust is that immune response remains to be completely understood.
A report published this week in the journal Science offers evidence that the antibody response against Sars-CoV-2 is indeed robust and appears to last for at least three months.
Infection renders a robust, neutralizing response
Researchers at Mount Sinai, New York City, followed, since March 2020, a group of 72,401 individuals who volunteered as donors to the experimental convalescent plasma therapy. Of those, 30,082 had anti-spike protein antibodies in their serum, in levels that ranged from moderate to high. Even though the majority of the volunteers didn’t have a confirmation of diagnosis by PCR, 95% of the cohort who had a PCR test did have antibodies against Sars-CoV-2.
But the presence of antibodies in the serum gives no warranty for protection. The research group went on to test whether Sars-CoV-2 antibodies were capable of neutralizing the virus. Through a microneutralization assay, the team found a strong correlation between the levels of antibodies in one person’s serum and the neutralization of Sars-CoV-2.
A timely immune response
Antibodies were present in recovered individuals, and they were conferring a protective response against the virus. But for how long? Studies have been giving us what seems like contradictory responses. An article, published this week in Nature Microbiology, for instance, showed that the levels of neutralizing Sars-CoV-2 antibodies start to wane three months after infection. However, it is important to note that a decline in the levels of antibodies after an infection is normal and a sign of a healthy immune system (for more on this topic, read this article by Apoorva Mandavilli).
The report by the Mount Sinai team offers a more optimistic look. Since the group of Mount Sinai volunteers were being accompanied since the beginning of the covid pandemic in New York, this report gives the possibility of analyzing different timepoints. The results seem to be encouraging, showing that antibody titers are stable over three months and show only a modest decline five months after the initial infection with Sars-CoV-2.
Researchers point out, even though this report gives no evidence that spike antibodies confer protection, it is very likely that this happens or, at least, that antibody responses decrease the odds of possible reinfection. Moreover, antibody levels and target proteins are crucial determinants in the robustness and longevity of the response against Sars-CoV-2. This report may have implications for vaccine design and distribution.
- Wajnberg, Ania, et al. “Robust neutralizing antibodies to SARS-CoV-2 infection persist for months.” Science(2020).
- Seow, Jeffrey, et al. “Longitudinal observation and decline of neutralizing antibody responses in the three months following SARS-CoV-2 infection in humans.” Nature Microbiology (2020): 1-10.