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. 2021 May 27;15(5):e0009374. doi: 10.1371/journal.pntd.0009374

Fig 4. SARS-CoV-2 S DNA vaccine induced long-term humoral immunity and cross-protection against the SARS-CoV-2 with D614G mutation.

Fig 4

BALB/c mice (n = 4 per group) were intramuscularly immunized three times at a 3-week interval with 100 μg of vector, pSARS-S or pSARS2-S, followed by electroporation. Serum samples were collected at the indicated time points after the first immunization. (A) Antibodies against the SARS-CoV-2 full-length spike protein were evaluated by ELISA. (B, C) Vaccine-induced neutralizing activity against SARS-CoV-2 with D614 or G614 genotypes was evaluated by neutralization assay. Antibody titers are presented as the mean ± SEM, and neutralization titers are expressed as the geometric mean with a 95% confidence interval. *p<0.05 by the Mann-Whitney test.