Fig. 4: Vaccine-induced CD8 + T-cell responses to ancestral spike and comparative analysis of antibody and CD8 + T-cell responses in COVISHIELD^TM and COVAXIN® vaccinees.

Whole Blood from COVISHIELD^TM and COVAXIN® individuals at baseline (D0) and 2 weeks post-vaccination (D98 for COVISHIELD^TM and D42 for COVAXIN®) were stimulated with spike peptide pool (1 µg/ml) for 20 h. CD8 + T-cells were analyzed for a intracellular expression of total cytokine+ cells (IFN-γ or IL-2 or TNF-a) obtained from Boolean gating in FlowJo and b for the frequencies of AIM expressing subsets (CD69 + CD137 + ). Participants were classified as either S-N- [n = 7 for COVISHIELD^TM (dark blue); n = 5 for COVAXIN® (dark red)] or S+ and/or N+ [n = 25 for COVISHIELD^TM (teal), n = 25 for COVAXIN® (pink)] at baseline. CD8 + T-cells expressing c effector cytokines and d AIM markers in subjects from the S+ and/or N+ group are further segregated as N- (n = 12 for COVISHIELD^TM and n = 11 for COVAXIN®) and N+ (n = 13 for COVISHIELD^TM and n = 14 for COVAXIN®). Line graphs represent background subtracted CD8 + T-cell frequencies. Statistical analyses was performed using a paired Wilcoxon test. e Correlations between total cytokine+ CD8 + T-cells (IFN-γ or IL-2 or TNF-a) in response to stimulation of whole blood with complete Wuhan spike peptide pool and corresponding neutralizing antibody responses (% inhibition) against SARS-CoV-2 Wuhan Spike at baseline and two weeks post-vaccination. Spearman’s correlation coefficient (r) and significance values (P) are indicated.