Severe lymphocyte dysfunction and impaired cellular immune response as a consequence of COVID-19

ABSTRACT

Introduction: A correct diagnosis of long-term complications in COVID-19 convalescents is of great importance for their therapeutic management. Aim(s) To identify long-term post-COVID-19 damages related to lymphocytes T to search prevention and treatments in future. Material(s) and Method(s) Data from 10 healthy volunteers, 23 patients (moderate/severe) COVID-19 were analysed. Responses of lymphocytes to LPS, ConA, CD3/CD28 mitogens and spike protein were measured in all groups during acute phase, 3- and 6-months post-hospitalization. Main lymphocyte T subpopulations (CD4, CD8) and CD25 expression on the lymphocyte subpopulations were also examined. Result(s) 6 of 13 severe patients were ventilated mechanically. The remaining 6 patients improved after high-flow nasal oxygen therapy and were discharged with normalized respiratory functions, the same as the mild/moderate COVID-19 group. We found that the decrease in total lymphocytes is equally due to the decrease in CD4 and CD8 cells. These changes persist in moderate and severely ill groups over 3 months post-COVID-19. In the case of CD4 lymphocytes, the changes concerned both naive (CD4+/CD25-) and activated (CD4+/CD25+) cells. A significant decrease in the CD8 cells was also observed, but only for the absolute number of naive CD8 lymphocytes (CD8+/CD25-). During the acute COVID-19 a significant impaired responses to ConA and CD3/CD28 were found. No difference in spike protein response was noticed. Conclusion(s) Long-term reductions (3- and 6-months) in the total count of lymphocytes in subpopulations and proliferative responses to mitogens suggest a severe impairment of the cellular immune response.