ABSTRACT
Background: Immunocompromised patients are considered high-risk and prioritized for vaccination against COVID-19 (1). Furthermore, vaccination-induced CD4 and CD8 T-cell responses have been suggested to have a protective role in COVID-19 (2). If T-cell responses are diminished after vaccination in immuno-compromised individuals is not known to date. Objectives: To investigate cellular immunity following mRNA vaccination against COVID-19 in healthy individuals and patients undergoing B-cell depletion therapy. Methods: In this interim analysis of the CoVVac study (NCT04858607), we analyzed T-cell responses in autoimmune patients treated with B-cell depleting therapy (BD, n=41) and age-matched healthy controls (HCs, n=50) 3-4 weeks after the second dose of mRNA vaccination against COVID-19. Therefore, we isolated PBMCs and stimulated them with a peptide pool covering the spike protein in vitro. Reactive CD4 and CD8 T-cells were determined by staining for IFNg, TNFa, IL-2 and GzmB by fow cytometry. Anti-SARS-CoV-2 antibody assays targeting the receptor-binding domain (RBD) or trimeric S protein (TSP) were performed to elucidate concomitant B-cell responses. Results: We observed signifcant alterations in anti-SARS-CoV-2 antibody responses in our cohort, the frequency of IFNg+ and IL-2+ CD4 and CD8 T-cells was similar in BD patients and controls. On the other hand, TNFa+ CD4 T-cells were signifcantly enriched in healthy controls versus BD patients (p=0.017) and correlated signifcantly with antibody titres (p=0.003). Similarly, GzmB+ CD8 T-cells were signifcantly diminished in our patient cohort (p<0.001) and also showed a signifcant correlation with antibody titres (p<0.001). Overall, the frequency of GzmB+ CD8 T-cells correlated very well with reactivity of T-cell subsets for other cytokines. This effect, however, is lost in the BD cohort. No difference was observed in the frequency of TNFa+ CD8 T-cells between the groups. Only 21 (42%) healthy individuals and 14 (34%) patients showed reactive T-cells for all the cytokines tested. This observation is mainly explained by a lack of cytokine production of CD8 T-cells in 26 (52%) HCs and 27 (66%) BD patients. In turn, 22 (44%) HCs and 17 (42%) patients didn't show any IL-2 producing CD8 cells. Of note, only 2 (4%) of HCs showed no GzmB+ CD8 T-cells whereas the number increased to 15 (37%) of BD individuals (p<0.001). In contrast, 42 (84%) HCs as well as 32 (78%) of patients showed production of all IFNg, TNFa and IL-2 in CD4 T-cells. Conclusion: Our data suggest that most patients with B-cell depleting therapy are able to mount T-cell responses similar to those of healthy individuals while a minority of these patients did not show complete immunity against SARS CoV-2. Further analyses are needed to better understand a possible link of B-cell depletion therapy and CD8 T-cell responses.