Fig. 6: Humoral and cellular responses to the pSARS2-S DNA vaccine in a repeated-dose toxicity study. | npj Vaccines

Fig. 6: Humoral and cellular responses to the pSARS2-S DNA vaccine in a repeated-dose toxicity study.

From: A DNA vaccine candidate delivered by an electroacupuncture machine provides protective immunity against SARS-CoV-2 infection

Fig. 6

Female SD rats (n = 5 per group) were intramuscularly immunized three times at a 2-week interval with placebo, 0.2 and 1 mg of pSARS2-S DNA with electrostimulation (40 Vpp and 120 Hz for 5 s), 2 mg of pSARS2-S DNA without electrostimulation, or 20 μg of recombinant spike protein adjuvanted with 250 μg aluminum hydroxide (rS/Alum). Serum samples were collected at week 6 after the first immunization. a IgG antibodies against spike protein were measured by ELISA. b, c Immunoglobulin G subclasses (IgG2a and IgG2b) in rat serum were detected by ELISA. d Neutralizing activity against wild-type SARS-CoV-2 was evaluated by neutralization assay. The dashed line indicates the initial fold dilution of serum samples. e–g Splenocytes were collected at week 6 after the first immunization, and the levels of secreted IFN-γ, IL-4 and IL-13 were evaluated after restimulation with recombinant spike protein. h The ratio of IFN-γ to IL-13 was calculated. Neutralization titers are expressed as the geometric mean with a 95% confidence interval, and other data are presented as the mean ± SEM. *p < 0.05, **p < 0.01 by the Mann–Whitney test.

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