Most people mount a strong antibody response to SARS-CoV-2 that does not decline rapidly
The vast majority of individuals infected with mild-to-moderate COVID 19 mount a robust antibody response that is relatively stable for at least five months, according to research conducted at the Icahn School of Medicine at Mount Sinai and published in the journal Science, reported Mount Sinai.
Additionally, the research team found that this antibody response correlates with the body's ability to neutralize (kill) SARS-CoV-2, the virus that causes COVID-19.
"While some reports have come out saying antibodies to this virus go away quickly, we have found just the opposite - that more than 90 percent of people who were mildly or moderately ill produce an antibody response strong enough to neutralize the virus, and the response is maintained for many months," said Florian Krammer, PhD, Professor of Vaccinology at the Icahn School of Medicine at Mount Sinai and a senior author of the paper. "Uncovering the robustness of the antibody response to SARS-CoV-2, including its longevity and neutralizing effects, is critically important to enabling us to effectively monitor seroprevalence in communities and to determining the duration and levels of antibody that protect us from reinfection. This is essential for effective vaccine development."
Study findings are based on a dataset of 30,082 individuals, who were screened within the Mount Sinai Health System between March and October 2020. The antibody test used in this research--an enzyme-linked immunosorbent assay (ELISA)--is based on the virus's telltale spike protein that contains the machinery that enables it to attach and gain entry into our cells. The ELISA assay was developed, validated, and launched at Mount Sinai by a team of internationally renowned researchers and clinicians.
The Mount Sinai antibody test detects the presence or absence of antibodies to SARS-CoV-2 and, importantly, is capable of measuring the titer (level) of antibodies an individual has. The high sensitivity and specificity of this test--meaning that a false negative or false positive is highly unlikely--allowed it to be among the first to receive emergency use authorization from New York State and the U.S. Food and Drug Administration.
"Our microbiology colleagues generated great science and tools that were brought from the research lab into the clinical laboratory, where we were able to implement robust and compliant diagnostic tests at an unprecedented pace," said Carlos Cordon-Cardo, MD, PhD, Irene Heinz Given and John LaPorte Given Professor and Chair of Pathology, Molecular and Cell-Based Medicine and last author of the paper. "The tireless efforts of so many have enabled us to uncover knowledge that can help inform COVID-19 policy and aid in vaccine development."
Determining the neutralizing effects of SARS-CoV-2 is critical to understanding the possible protective effects of the immune response. Another important and outstanding question in the scientific community is the longevity of the antibody response to the spike protein. To answer that question, the team recalled 121 plasma donors at a variety of titer levels for repeat antibody testing at approximately three months and five months post-symptom onset. When comparing overall titers, they saw a slight drop from a geometric mean titer (GMT) of 764 to a GMT of 690 from the first to second testing time point and another drop to a GMT of 404 for the last testing time point, indicating that a moderate level of antibody is retained by most people 5 months after symptom-onset. In the higher titer range, they observed a slow decline in titer over time. Interestingly, they saw an initial increase in titer for individuals who had originally tested as having low to moderate titer levels. This is in agreement with earlier observations from their study group that indicate seroconversion in mild COVID-19 cases might take a longer time to mount.
"The serum antibody titer we measured in individuals initially were likely produced by plasmablasts, cells that act as first responders to an invading virus and come together to produce initial bouts of antibodies whose strength soon wanes," said Ania Wajnberg, MD, Director of Clinical Antibody Testing at the Mount Sinai Hospital and first author of the paper. "The sustained antibody levels that we subsequently observed are likely produced by long-lived plasma cells in the bone marrow. This is similar to what we see in other viruses and likely means they are here to stay. We will continue to follow this group over time to see if these levels remain stable as we suspect and hope they will."