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

ONOFRIO L; JEREMIAS DUTTO J; BOSSIO S; BAIGORRI E; BRUGO MB; ALMADA L; MARIN CONSTANZA; RUIZ MORENO F; VOLPINI X; ALMEIDA M; OLIVERA C; PONCE N; QUIROZ JM; SILVERA RUIZ S; BOFELLI LUCIA; ACOSTA RODRÍGUEZ E; AMEZCUA VESELY C; ARROYO D; CERBÁN F; CERVI L; LAURA FOZZATTI L; ICELY P; IRIBARREN P; MALETTO B; MORÓN G; RODRÍGUEZ GALÁN C; STEMPIN C; BERTONE M; ABIEGA A; ESCUDERO D; KAHN A; CAEIRO JP; MACCIONI M; MOTRÁN M; CHIAPELLO L; MONTES C; GRUPPI A; SOTOMAYOR C

Congreso; Reunión Conjunta SAIC, SAI, AAFE, NANOMED.AR 2021; 2021

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 hospitalized patients with moderate (MD) and severe clinical disease (SD) and 14 aged matched healthy donors (HD) by FACS.All patients exhibited a reduced frequency of CD3+T and Tregs cells compare to HD (p< 0.05). When exhaustion was evaluated, SD patients 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 SD patients showed a higher % of GZMB+ and CD107+ cells than MD patients or HD (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 SD patients (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 HD patients 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 MD or SD patients. Indeed, MD and SD showed higher % of EM cells than HD patients.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.