Generation of humoral immune responses in C57BL/6 mice following immunization with different vaccine constructs. (a) Outline for vaccine construct and immunization protocol using groups of C57BL/6 mice vaccinated with 3 doses of pQAC-CoV (I.N) or pQAC-CoV (I.M) with 3-week interval. Another group of C57BL/5 mice were vaccinated with pQAC-CoV (I.N) at week-0 followed by boost with MVA-CoV (I.N) at week-6. (b) ELISA titers of SARS-CoV-2 S-specific IgG in mice sera, (c) ELISA titers of SARS-CoV-2 spike receptor-binding domain (RBD)-specific IgG in mice serum and (d) ELISA titers of SARS-CoV-2 S-specific IgA in bronchoalveolar lavage (BAL), significance (*, p < 0.05, ****, p < 0.0001) was determined by two-way ANOVA. Data show mean  SEM.
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