Fig. 6: NLRP3 inflammasome activation is not required for Matrix-M adjuvanticity in vivo.

C57BL/6 (WT) and Nlrp3 KO mice (n = 10/group) were immunized with 0.1 µg SARS-CoV-2 rS (rS) alone or adjuvanted with 5 μg Matrix-M, Matrix-A, or Matrix-C. Serum samples obtained 13, 20, and 28 days after the primary immunization were evaluated by ELISA for IgG1 (A) and IgG2c (B) antibody titers against rS protein and for hACE2 receptor-inhibiting antibody titers (C). At day 28, splenocytes from individual mice were isolated and the number of cells producing IFN-γ, IL-2, or IL-4 in response to rS protein restimulation was determined by FluoroSpot assay (D). Individual titers (ELISA) or spot forming units (SPU)/10⁶ splenocytes are shown as individual symbols, with horizontal bars representing geometric mean values, and error bars represent their 95% confidence intervals. Additionally, splenocytes were analyzed by flow cytometry (intracellular staining) to access frequencies of rS-specific CD4⁺ and CD8⁺ T cells producing IFN-γ and IL-4 (E). Data for each individual mouse response are shown with symbols and group means are represented by horizontal bars. The data (A–D) were log-transformed before being analyzed. The data (A–E) were analyzed for differences between WT and and Nlrp3 KO mice within each adjuvanted group by one-way ANOVA with Šidák’s multiple comparisons test (*for p < 0.05, ** for p < 0.01).