The study by Sekine et al. presents a thorough characterization of SARS-CoV-2-specific T cell responses by using an extensive FACS panel, peptide stimulations, tetramer staining and IFN-γ ELISpot analysis in a cohort of 200 individuals. Virus-specific T-cells were detected in a declining frequency from convalescent individuals experiencing severe COVID-19 to patients with milder symptoms, exposed family members, and blood donors. A significant fraction of those individuals showing virus-specific T cells had no detectable IgG antibodies towards the S1, S2, N, or E protein. Whether these T memory cells confer protective immunity in the absence of antibodies will only more longitudinal studies be able to unravel. Altogether, these findings underline that T cells deserve thorough investigations to solve the puzzle on immunity against COVID-19.
The research by Gallais et al. shows that most family members of eight index patients developed a specific T-cell response towards SARS-CoV-2 in the absence of seroconversion. These specific T-cell responses were measured with an IFN-γ ELISpot after stimulation with scanning peptide pools representing several viral antigens. Interestingly, the index patients showed T-cells responses to more viral antigens than their contact persons. All index patients elicited T-cell responses to the main viral antigens S1, S2, N, and M. In conclusion, exposure studies solely relying on SARS-CoV-2 antibodies assessment may lead to an underestimation of prior virus infections.
Mabtech products used