Fig. 2: Immunogenicity of HLA-EPs in both HLA-A*02:01/DR1 and HLA-A*11:01/DR1 transgenic mice.

a Schematic diagram of the HLA-EPs mRNA construct. b, c The expression of HLA-EPs in HEK293T cells. The results are shown by the mean fluorescent intensity (MFI) of HLA-EPs positive cells (b) and the representative flow cytometry plots (c) of 3 biological replicates containing 3 technical replicates. d–f The proliferation of epitope-specific splenocytes producing IFN-γ following stimulation with the peptide pool. The proliferation of epitope-specific, IFN-γ producing splenocytes was measured by ELISpot. Each point represents the mean of 3 technical replicates, with a limit of detection (LOD) = 2, and representative dots are shown (d). The frequency of IFN-γ positive CD8⁺ T cells was measured by an ICS (e, f). The representative flow cytometry plots are presented, and symbols represent individual mice. g–j The CD8⁺ T-cell-dependent protection of LNP-HLA-EPs against SARS-CoV-2. Both vaccinated HLA-A*02:01/DR1 and HLA-A*11:01/DR1 transgenic mice with or without CD8⁺ T-cell depletion, were infected with the SARS-CoV-2 B.1.351 variant (1.4 × 10⁵ PFU/mouse). Viral titers in lung tissues of HLA-A*02:01/DR1 and HLA-A*11:01/DR1 transgenic mice, with and without CD8⁺ T-cell depletion after 4 days post-inoculation (n = 5), were determined by a plaque assay with two technical replicates (g, h). The LOD was 10 PFU per gram of tissue. Histopathological changes in the lungs of challenged mice were evaluated by an H&E staining (i, j). Images derived from one representative animal in each group with sites of inflammatory cell infiltration (black arrows), blood clots (blue arrows), and alveolar deformation (red arrows) are presented. Scale bar is 50 μm. All data (b, d–j) are presented as the mean ± S.E.M. from the indicated number of biological repeats, and statistical significance was calculated via one-way ANOVA with Tukey’s multiple comparison post hoc two-sided tests (b, d–f, i, j) or two-way ANOVA with Bonferroni’s multiple comparisons (g, h). P values were adjusted for multiple comparisons. Source data are provided as a Source Data file. Data are representative of one (i, j), two (d–h), or three (a, b) independent experiments with similar results.