A group from National Institute of Immunology, New Delhi, etc. has reported on immune memory (CD4+T-cell reaction) in mild COVID-19 patients and cross-reactivity of CD4+T-cells against SARS-CoV-2 in unexposed donors
https://www.frontiersin.org/articles/10.3389/fimmu.2021.636768/full
In mild COVID-19 patients, it was reported that the immune memory (i.e, CD4+T-cell reactions to SARS-CoV-2) continues for about 5 months (median about 3 months). On the other hand, in SARS-CoV-2 unexposed donors, there was no immune reaction to SARS-CoV-2 spike protein, but the CD4+ T-cells specific to SARS-CoV-2 N protein were observed in 66% of the donors. In SARS-CoV-2 exposed patients, the CD4+ T-cells targeted SARS-CoV-2 spike protein rather than SARS-CoV-2 N protein.
Whether the cross-reactive CD4+ T cells are contributing to suppressing SARS-CoV-2 infection and further less severe outcome needs to be addressed in the prospective cohort before and after COVID-19.
