Functional SARS-CoV-2-specific immune memory persists after mild COVID-19

Rodda, L. B.; Netland, J.; Shehata, L.; Pruner, K. B.; Morawski, P. M.; Thouvenel, C.; Takehara, K. K.; Eggenberger, J.; Hemann, E.; Waterman, H. R.; Fahning, M. L.; Chen, Y.; Rathe, J.; Stokes, C.; Wrenn, S.; Fiala, B.; Carter, L. P.; Hamerman, J. A.; King, N. P.; Gale, M.; Campbell, D. J.; Rawlings, D.; Pepper, M.

The recently emerged SARS-CoV-2 virus is currently causing a global pandemic and cases continue to rise. The majority of infected individuals experience mildly symptomatic coronavirus disease 2019 (COVID-19), but it is unknown whether this can induce persistent immune memory that might contribute to herd immunity. Thus, we performed a longitudinal assessment of individuals recovered from mildly symptomatic COVID-19 to determine if they develop and sustain immunological memory against the virus. We found that recovered individuals developed SARS-CoV-2-specific IgG antibody and neutralizing plasma, as well as virus-specific memory B and T cells that not only persisted, but in some cases increased numerically over three months following symptom onset. Furthermore, the SARS-CoV-2-specific memory lymphocytes exhibited characteristics associated with potent antiviral immunity: memory T cells secreted IFN-{gamma} and expanded upon antigen re-encounter, while memory B cells expressed receptors capable of neutralizing virus when expressed as antibodies. These findings demonstrate that mild COVID-19 elicits memory lymphocytes that persist and display functional hallmarks associated with antiviral protective immunity.