Some COVID-19 patients maintain antibodies for long despite mild to moderate symptoms, finds study
In most people, the SARS-CoV-2 specific antibodies gradually declined over the course of three to four months.
The first case of COVID-19 was reported in December last year. Since then, the disease has infected more than 47 million people, out of which, over 34 million have recovered successfully. However, even after all these cases, scientists cannot, with certainty, tell how long recovered patients will remain immune to the disease.
This is partly because the disease is very new and there is much to learn about it still. There have also been cases of reinfections -- most likely from a different strain of the virus but it is a possibility nonetheless.
Evidence from previous coronavirus es has shown that antibodies against this class of viruses do not last for more than six months and start declining quickly after the disease resolves. Those with severe COVID-19 are shown to have a bigger antibody repertoire than those with mild disease.
However, a group of researchers at the Brigham and Women’s hospital, USA stated that they have found a subset of coronavirus patients who develop a strong and lasting antibody response even after getting mild to moderate disease.
The findings of the study are published in the journal Cell.
For the study, Dr Duane Wesemann, an immunologist at the Brigham Division of Allergy and Clinical Immunology and Associate Professor at the Harvard Medical School, and his team enrolled 92 people from the Boston area who had got mild to moderate COVID-19 between March and June 2020. All the patients, except five, were monitored at home.
Blood samples were collected from all the patients every month and antibodies were measured in every sample, especially the IgG antibody -- the one that is seen later in the infection but stays on for long in the body.
Based on the difference in antibody levels, the researchers divided the teams into two parts -- those that maintained virus-specific antibodies for long (the sustainers) and those that did not.
In most people, the SARS-CoV-2 specific antibodies gradually declined over the course of three to four months. However, in 20 percent of people, antibody production stayed persistent and increased during the same time period.
Those who sustained antibodies showed symptoms for a much shorter duration -- 10 days as compared to the 16 days normally. They also had a difference in memory T and B cells. Memory cells are those cells in the immune system that make sure that your body recognises and mounts a quick antibody response should a pathogen attacks your body for the second time.
In a news release by the Brigham and Women’s hospital, Wesemann said, “Figuring out how these individuals are able to support longer-term antibody production is relevant to COVID-19 , and will also have important implications for our understanding of the immune system in general.”
Limitations of the study
In the news release, the authors of the study mentioned that the study had a major limitation in that the majority of volunteers were white women.
So, more diverse studies are needed to confirm the findings of this study and to determine if something similar happens in asymptomatic and severe COVID-19 patients.
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