Fig. 6. LNP-based DNA vaccine-induced potent immune response and protection against SARS-CoV-2 infection and its variants.

A Scheme of immunization. K18-hACE2 mice were immunized with controls and LNP-HPS, and boosted with equivalent doses 3 weeks later. Immunized mice were challenged with lethal 6 × 10⁴ PFU of SARS-CoV-2 variants Gamma lineage (P.1), sera were collected at 24 h before the infection (pre-infection), and 5 days post infection for all immunized groups and the lungs were collected 5 days post infection. Levels of total antigen-specific IgG anti-spike serum of mice at B pre-infection, and C 5 days post infection (n = 4/group). D Levels of total IgA anti-spike in lung homogenate at 5 days post infection (n = 4/group). Levels of neutralizing antibodies in sera of immunized mice at E, F pre-infection, and G, H 5 days post infection against P.1 (n = 5/group). Levels of neutralizing antibodies in sera of immunized mice at I, J pre-infection, and K, L 5 days post infection against Omicron (n = 5/group). Data are presented as mean ± SEM; ns not significant, *p < 0.05. F, H, J, L Kruskal–Wallis followed by Dunn’s multiple comparisons test. Source data are provided as a Source Data file.