PHENOTYPIC AND FUNCTIONAL CHARACTERIZATION OF PERIPHERAL T CELL POPULATIONS FROM COVID-19 PATIENTS HOSPITALIZED IN HOSPITAL PRIVADO UNIVERSITARIO CÓRDOBA - ARGENTINA.

Congreso; LXIX Sociedad Argentina de Inmunología; 2021

Sociedad Argentina de Inmunología

SARS-CoV-2 infection results in asymptomatic, mild or severe disease. T cells could contribute to these different outcomes, but it remains unclear whether T cell response is dysfunctional or excessive. Here, we evaluated the phenotypic and functional features of 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. All Cpts exhibited a reduced frequency of CD3+T and Tregs cells compare to HC (p< 0.05). When exhaustion was evaluated, SEV Cpts showed 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-ɣ, IL-2 and TNF) were observed, T conv cells from SEV Cpts showed a higher % of GZMB+ and CD107+ cells than MOD Cpts or HC (p<0.05). Circulating CD8+ T cells express different levels of CD8, where CD8lo cells represent highly activated cytotoxic T cells. COVID-19 patients presented a higher % of CD8lo T cells than controls and this increment was even more pronounced in SEV Cpts (p=0.04, MD vs HD; p=0.0012, SD vs HD). CD8lo T cells exhibited impaired cytokine production and CD107a expression compared to CD8hi T cells, although GZMB levels were similar among both CD8+ subsets. CD8lo population from HC showed higher % of naïve T cells than effector memory (EM)(p=0.04) or EMRA (p=0.008) subsets, but this distribution was not seen in MOD or SEV Cpts. Indeed, MOD or SEV Cpts showed higher % of EM cells than HC. Conclusion: the disease severity impacts on the phenotype and functional features of CD4+ and CD8+ T cells, with a pronounced increment in the % of CD8lo T cells as the disease worsens. These cells appear to have dysfunctional phenotype with an impairment of effector cytokines production but maintaining cytotoxic potential. The CD8hi/CD8lo ratio might be a useful parameter to predict the disease outcome.