SARS-CoV-2-specific serological and functional T-cell Immune responses during acute and early COVID-19 convalescence in Solid Organ Transplant patients.

The description of protective humoral and T-cell immune responses specific against SARS-CoV-2 has been reported among immunocompetent (IC) individuals developing COVID-19 infection. However, its characterization and determinants of poorer outcomes among the at-risk Solid Organ Transplant (SOT) patient population has not been thoroughly investigated. Cytokine-producing T-cell responses such as IFN-I³, IL-2, IFN-I³/IL-2, IL-6, IL-21 and IL-5 against main immunogenic SARS-CoV-2 antigens and IgM/IgG serological immunity were tracked in SOT (n=28) during acute infection and at 2 consecutive time-points over the following 40 days of convalescence and were compared to matched IC (n=16) patients admitted with similar moderate/severe COVID-19. We describe the development of a robust serological and functional T-cell immune responses against SARS-CoV-2 among SOT patients, similarly to IC patients during early convalescence. However, at the infection onset, SOT displayed lower IgG seroconversion rates (77% vs 100%; p=0.044), despite no differences on IgG titters, and a trend towards decreased SARS-CoV-2-reactive T-cell frequencies, especially against the membrane protein (7[0-34] vs 113[15-45] p=0.011, 2[0-9] vs 45[5-74], p=0.009 and 0[0-2] vs 13[1-24], p=0.020, IFN-I³, IL-2 and IFN-I³/IL-2 spots, respectively). In summary, our data suggest that despite a certain initial delay, SOT achieve comparable functional immune responses than the general population after moderate/severe COVID-19.