A high body mass index (BMI) would affect the immune response of the body exposed to the Sars-CoV-2 virus of Covid-19.
The people in overweight could be more likely to be infected (and reinfected) with the Covid-19 virus. This is shown by a study carried out by researchers at the University of Queensland (Australia) and published in the journal Clinical & Translational Immunology on December 3. The objective was to understand how a high Body Mass Index (BMI), i.e. higher than normal weight (BMI of 25kg/m2 or more) affects the body’s immune response after being infected with Sars-CoV-2, the Covid virus. “We have already shown that being overweight, and not just obese, increases the severity of Sars-CoV-2. But this work shows that excess weight creates an alteration in the antibody response to infection” said Marcus Tong, molecular biology researcher and co-author of the study in a communicated.
Less effective antibodies
To carry out their study, the Australian researchers took blood samples:
- of people who have recovered from Covid-19 infection for 3 to 13 months (these people have not been exposed to Sars-CoV-2 nor vaccinated in the meantime).
- of people, 5 months after the second dose of vaccination against Covid-19 (the majority of whom have not had previous infection with Sars-CoV-2)
They then measured their humoral (immune) responses to the Covid virus, by grouping individuals based on a BMI greater than or less than 25 kg/m2. Result: people with a higher BMI had a weaker antibody response after being infected with the Covid virus. Concretely :
► 3 months after infection, high BMI was associated with reduction in antibody titers
► 13 months after infectionpeople with a higher BMI had poorer quality of antibodies and a lower percentage of B cells (a type of immune cell) capable of recognizing the spike protein of the Covid virus. Gold, “generation of memory B cells is essential for an effective humoral immune response and protection against CoV-2 reinfection” we can read in the study.
The researchers suggest that this could be due to a overproduction of leptin, a hormone produced by fatty tissues which could disrupt the proper functioning of the immune system.
Not the same effect after vaccination
“If the infection is associated with a increased risk of serious illness and to a impaired immune response For people who are overweight, this group is at potentially increased risk of reinfection” said Dr Kirsty Short, specialist in molecular chemistry and biosciences and lead author of the study. In contrast, a high BMI did not have a no effect on the immune response linked to vaccination against Covid-19 approximately 6 months after administration of the second vaccine. For Dr. Short “it is more important than ever for this group to ensure they are vaccinated.”