Disease‐duration based comparison of subsets of immune cells in SARS CoV‐2 infected patients presenting with mild or severe symptoms identifies prognostic markers for severity

INTRODUCTION: Infection with SARS‐CoV‐2 leads to a spectrum of symptoms. Understanding the basis for severity remains crucial for better management and therapy development. So far, older age, associated‐comorbidities, and IL‐6 have been associated with severity/mortality. MATERIALS AND METHODOLOGY: As a primary step, we analyzed the frequency and functional profile of innate immune cells (NK cells/dendritic cells/monocytes) and adaptive immunity‐driving lymphocytes (B cells/T cells/follicular T helper cells) by flow cytometry. Sixty cases of SARS CoV‐2 infection (25 severe, 35 mild) and ten healthy subjects without SARS CoV‐2 IgG were included. Disease‐duration based analysis of immune profile was explored for early events differentiating the two disease forms. Neutralizing antibody titers were determined by PRNT. RESULTS AND CONCLUSION: Disease severity was found to be associated with impaired maturation of mDCs and hyperactivation of NK, follicular T helper cells, and CD8 T cells. Lower IL‐21 receptor expression on memory B cells indicated an imbalance in IL‐21/IL‐21 R ratio. Lower BCMA positive plasmablast cells in severe cases did suggest a probable absence of long‐term humoral immunity. Multivariate analysis revealed a progressive association of PD‐1+CD4 T cells with PRNT(50) titers. Thus, in addition to identifying probable prognostic markers for severity, our study emphasizes the definite need for in‐depth viral antigen‐specific functional analyses in a larger patient cohort and with multiple sampling.