Researchers found that follicular helper T-cells respond in different ways to structural proteins in COVID-19. They have been studying how the response happens over time.
Several studies report the observance of helper T-cell responses to the virus that causes COVID-19, SARS-CoV-2, in over 80% of individuals recovering from COVID-19. Besides helping in developing cytotoxic T cells, helper T cells stimulate B cells to produce antibodies. Therefore, T cells may help in the development of neutralizing antibodies against SARS-CoV-2.
T follicular helper cells are crucial in the process of neutralizing antibody development. They are specialized helpers to B cells that are important for B-cell affinity maturation and the development of high-affinity antibodies and memory B cells. Although it is challenging to directly study human lymph tissue, peripheral T follicular helper (pTfh) cells can be sampled from the blood. A study was conducted to determine the helper T-cell responses to a selection of SARS-CoV-2 proteins in patients recovering from COVID-19.
Patient peripheral blood mononuclear cell samples were obtained from a COVID-19 repository. The researchers used two types of flow cytometry-based assays to measure the level of pTfh cells in samples. SARS-CoV-2-specific antibodies were measured in patient plasma samples, and antibody neutralization assays were conducted. The results indicate a correlation between SARS-CoV-2-specific pTfh frequencies and neutralizing antibody responses. Also interesting is that the pTfh cell responses to SARS-CoV-2 are delayed, increasing as time passes. For instance, the results of one assay type showed responses in 57% of the patients in the first visit, but 62% of the patients at the time of the second visit.
Overall, the pTfh cell response was low during earlier recovery from COVID-19 but increased over time with a strong response observed by a month after the symptoms began. This is not the typical scenario seen with immune responses to other viral infections (early maximum responses that decrease over time). The data generated from the study suggests that pTfh responses are necessary for the formation of SARS-CoV-2-specific neutralizing antibodies and increases the understanding of T cells’ role in COVID-19 immunity.
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Lakshmi Supriya, P. (2020). Research identifies antigen-specific peripheral T follicular helper cells in COVID-19 infected patients. Retrieved 11 November 2020, from https://www.news-medical.net/news/20201014/Research-identifies-antigen-specific-peripheral-T-follicular-helper-cells-in-COVID-19-infected-patients.aspx