Fig. 3.

Induction of humoral and mucosal responses by JOL2818 (conserved) and JOL2819 (variable). Balb/c mice were immunized orally with two doses of 1 × 10⁷. Specific antibody responses in mice (N = 4) at week 3 post-immunization were assessed for NTD, RBD, HR, N and RdRp antigens. (A) IgG, IgG1 and IgG2a response in serum and lung of mice was determined by ELISA. The bars indicate the means of the titres from four biologically independent mice per group. (B) IgA response in sera of immunized mice at sera dilution of 1:50, sIgA response in the intestinal lavage at a sample dilution of 1:100 and IgA response in lung homogenates at 1:10 sample dilution. (C) Serum neutralizing antibody titre (NAb) from mice quantified by CPE and IFA analysis against SARS-CoV-2 Delta variant. Error bars denote SEM. Data were analysed by independent-samples T-test and ANOVA. ∗p < 0.05, ∗∗p < 0.01 and ∗∗∗p < 0.001.