Phenotypic and functional characterization of peripheral T cell populations from COVID-19 patients hospitalized in Hospital Privado Universitario Córdoba-Argentina.

ONOFRIO, L.; .....; IRIBARREN, P.; ......

Buenos Aires

Congreso; Reunión de Sociedades de Biociencias (SAI, SAIC, AAFE, NANOMED-AR); 2021

disease. T cells could contribute to these different outcomes, butit remains unclear whether T cell response is dysfunctional or excessive.Here, we evaluated the phenotypic and functional featuresof circulating T cells from a cohort of 40 COVID-19 patients (Cpts)with moderate (MOD) and severe (SEV) clinical disease (aged 21-80 years) and 14 aged matched healthy controls (HC) by FACS. AllCpts exhibited a reduced frequency of CD3+T and Tregs cells compareto HC (p< 0.05). When exhaustion was evaluated, SEV Cptsshowed higher % of PD-1+ and CD39+ in T conv cells (p<0.05),whereas no differences were found in BTLA or TIGIT expression.Even though, no differences in cytokine production (INF-γ, IL-2 andTNF) were observed, T conv cells from SEV Cpts showed a higher% of GZMB+ and CD107+ cells than MOD Cpts or HC (p<0.05). CirculatingCD8+ T cells express different levels of CD8, where CD8locells represent highly activated cytotoxic T cells. COVID-19 patientspresented a higher % of CD8lo T cells than controls and this incrementwas even more pronounced in SEV Cpts (p=0.04, MD vsHD; p=0.0012, SD vs HD). CD8lo T cells exhibited impaired cytokineproduction and CD107a expression compared to CD8hi T cells, althoughGZMB levels were similar among both CD8+ subsets. CD8lopopulation from HC showed higher % of naïve T cells than effectormemory (EM)(p=0.04) or EMRA (p=0.008) subsets, but this distributionwas not seen in MOD or SEV Cpts. Indeed, MOD or SEV Cptsshowed higher % of EM cells than HC.Conclusion: the disease severity impacts on the phenotype andfunctional features of CD4+ and CD8+ T cells, with a pronouncedincrement in the % of CD8lo T cells as the disease worsens. Thesecells appear to have dysfunctional phenotype with an impairmentof effector cytokines production but maintaining cytotoxic potential.The CD8hi/CD8lo ratio might be a useful parameter to predict thedisease outcome.