Fig. 3: Immunizations with mRNA-1273 and S(2P) protein, delivered with TLR4 agonist, elicit S-specific T_H1-biased T cell responses.

B6C3F1/J mice (n = 10 per group) were immunized at weeks 0 and 3 with 0.01, 0.1 or 1 μg of mRNA-1273 or SARS-CoV-2 S(2P) protein with SAS adjuvant. a–c, Sera were collected two weeks post-boost and assessed by ELISA for SARS-CoV-2 S-specific IgG1, and IgG2a and IgG2c. End-point titres (a, b) and end-point titre ratios of IgG2a plus IgG2c to IgG1 (c) were calculated. Ratios were not calculated for mice for which end-point titres did not reach the lower limit of detection (dotted line; N/A). d–g, Seven weeks post-boost, splenocytes were isolated from five mice per group and restimulated with vehicle or pools of overlapping peptides from SARS-CoV-2 S protein in the presence of a protein transport inhibitor cocktail. After 6 h, intracellular cytokine staining was performed to quantify CD4⁺ and CD8⁺ T cell responses. Cytokine expression in the presence of vehicle only was considered as background and subtracted from the responses measured from the S1 and S2 peptide pools for each individual mouse. d, e, Percentage of CD4⁺ T cells expressing IFN-γ, TNF, IL-2, IL-4 and IL-5 in response to the S1 (d) and S2 (e) peptide pools. f, g, Percentage of CD8⁺ T cells expressing IFN-γ, TNF and IL-2 in response to the S1 (f) and S2 (g) peptide pools.

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