Fig. 3

Humoral and cellular immune responses following Omicron infection among unvaccinated individuals with and without pre-Omicron exposure. Antibody levels (a) and percentage ACE-2 inhibition levels (b) to SARS-CoV-2 variants among secondary (SP + UNV) and primary Omicron-infected (SN + UNV) unvaccinated individuals at D0, 30, and 90 (N = 11 for Secondary Omicron infected; N = 8 for Primary Omicron infected). (c-j) Variant spike-specific B cell and T cell responses elicited by Omicron infection among previously exposed and unexposed unvaccinated individuals. (c) RBD-specific spot-forming antibody-secreting cells (ASCs) expressed as a percentage of total IgG-secreting cells; (d) RBD-specific spot-forming ASCs (e-g) CD4 T cell responses (h, i) CD8 T cell responses following Omicron infection at Day 0, 30, 90 in Secondary Omicron infected (black) and Primary Omicron infected (pink). Spike-specific (e) activation-induced marker-positive (AIM+) CD4 T cells (f). Any one of the three cytokines interferon-γ (IFN-γ)/tumor necrosis factor-α (TNF-α)/interleukin-2 (IL2) + CD4 T cells (g) AIM + CD4 circulating T follicular helper (cTfh) cells (h) AIM + CD8 T cells (i). Any one of the three cytokines IFN-γ/TNF-α/IL2 + CD8 T cells (j) Proportion of polyfunctional CD4 T cells in secondary and primary Omicron-infected, unvaccinated individuals assessed on D0, 30, 90 following Omicron infection. The data are represented as median with interquartile range. Data were analyzed for statistical significance using Mann–Whitney U test. Background subtracted data were analyzed in all cases. P-values are indicated by asterisks as *p < 0.05, **p < 0.01. N = 8 for Secondary Omicron infected (SP + UNV); N = 8 for Primary Omicron infected (SN + UNV) for T and B cell analysis. WT- wild type.