Fig. 4

The specific humoral immune response elicited by mRNA vaccines with various signal sequence modifications against different SARS-CoV-2 variants. (A) The arrangement of the mouse experiment was diagrammed. (B) Pseudovirus neutralization assays for the WT, Delta, and Omicron B.1.1.529 variants were conducted on day 42. (C-E) Serum ELISA quantified RBD^WT, RBD^Delta and RBD^Omicron-specific IgG titers on day 28. Additionally, ELISA assessed the variants’ RBD-specific IgG titers in serum at day (F) 42 and (G) 84 following administration of RBD^WT mRNA vaccines with different signal sequences. (H) Representative flow cytometry diagrams and (I) quantification of S protein-specific memory B cells in spleen lymphocytes were provided for day 84 (n = 4). The gating strategy was depicted in Figure S3. The data were shown as mean ± SEM, n = 4. ^*P < 0.05, ^**P < 0.01, ^***P < 0.001