In mild cases of SARS-CoV-2, understanding how strong the antibody response is – including longevity and functionality – to determine if re-infection is possible. Previous research on common human coronaviruses suggested that infection induces neutralizing antibodies that can last for years to protect against re-infection. In addition, the transfer of convalescent serum or the neutralization of monoclonal antibodies to naive animals can be protective and significantly reduce virus replication.
In the present work, multidisciplinary research teams from the Mount Sinai health system in New York City have set themselves the goal of clarifying and characterizing aspects of the humoral immune response to SARS-CoV-2.
The researchers used an assay to characterize the antibody response based on the trimerized, stabilized ectodomain of the SARS-CoV-2 spike protein. In this study, an ELISA (Enzyme-Linked Immunosorbent Assay) developed by Mount Sinai researchers was used to characterize the antibody response to SARS-CoV-2. The test was one of the first to receive emergency approval from the U.S. Food and Drug Administration.
The Mount Sinai team began screening people for antibodies to SARS-CoV-2 in March 2020. By the beginning of October, the group had examined over 72,000 people with a total of just over 30,000 people who tested positive. Of these positive samples, about 7% had low titers (1:80 or 1: 160), 22% had moderate titers (1: 320) and about 70% had high titers (1: 960 and 1: 2880). Therefore, the number of people who did not seroconvert (develop an antibody response) after SARS-CoV-2 infection was low.
In order to determine the protective effect of the neutralization of SARS-CoV-2 spike antibodies, the researchers carried out a quantitative microneutralization test based on authentic SARS-CoV-2 with 120 samples of known ELISA titers ranging from “negative” to a titer of 1 through: 2880. They found that about 50% of the low-titer samples had neutralizing activity, 90% of the medium-titered samples had neutralizing activity, and 100% of the high-titer samples had neutralizing activity.
“Our microbiology colleagues have developed great scientific knowledge and tools that have been brought from the research laboratory to the clinical laboratory, where we have been able to run robust and compliant diagnostic tests at an unprecedented rate,” said the author’s chairman, Dr. Carlos Cordon-Cardo of pathology at the Icahn School of Medicine on Mount Sinai, in a statement. “The tireless efforts of so many have enabled us to uncover knowledge that can help educate COVID-19 policy and aid vaccine development.”
To test the longevity of the antibody response, they tested 121 plasma donors at various titre levels that were originally screened for two additional time points on about the 30th day after symptoms appeared. The initial measurement was collected between 33 and 67 days after the start, the second between 52 and 104 days after the start, and the third between 113 and 186 days after the start.
The researchers observed a slight decrease in the titer level from the first to the second point in time and another to the last. In the higher titer samples, the decrease in titer level over time was slow. Overall, most of the antibody titers were stable for a period of at least three months, with only a slight decrease by the time point of five months.
“The serum antibody titer we initially measured in individuals was likely produced by plasmablasts, cells that act as first responders to an invading virus and come together to produce initial bouts of antibodies that will soon weaken,” said Dr. Ania Wajnberg, first author and director of clinical antibody tests at Mount Sinai Hospital. “The sustained levels of antibodies that we later observed are likely produced by long-lived plasma cells in the bone marrow. This is similar to what we see with other viruses and likely means that they will stay here. We will continue to follow this group. ”Time to see if these levels remain stable as we suspect and hope they do. ”
The researchers plan to follow this group of patients for longer periods of time. While their results cannot provide conclusive evidence that these antibody responses protect against re-infection with SARS-CoV-2, the team believes that it is very likely that the antibodies will reduce the likelihood of re-infection and the disease in the In the event of a breakthrough infection.
“While there have been some reports that antibodies to this virus are disappearing quickly, we’ve found just the opposite: more than 90% of people who have had mild or moderate illness produce an antibody response strong enough to do that Virus and neutralize the virus. “The response is sustained for many months,” said author Florian Krammer, PhD, professor of vaccination science at the Icahn School of Medicine on Mount Sinai. “Uncovering the robustness of the antibody response to SARS-CoV-2, including its longevity and neutralizing effects, is critical so that we can effectively monitor seroprevalence in communities and determine the duration and levels of antibodies that may present us before recurrence Protecting infection is essential to effective vaccine development. ”
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