Comparison of mucosal immune responses to African swine fever virus antigens intranasally delivered with two different viral vectors

Transmission of African swine fever virus (ASFV) in domestic swine occurs mainly via contact with mucosal surfaces. In this study, we constructed a pseudotyped surface-displaying BacMam-F1 vector expressing ASFV CD2v-p30-p54 fusion antigen, and compared its mucosal responses in pigs with that of rAd-F1 vector expressing the same antigen. From day 21 after intranasal immunization, the antigen-specific IgG and intranasal secretory IgA (S-IgA) antibody responses induced by BacMam-F1 were significantly stronger than that by rAd-F1. The significantly different S-IgA antibody responses were also detected in their tracheal washes and lung lavages. After stimulation with ASFV antigens, 4/6 S-IgA-promoting cytokine responses in porcine alveolar macrophages (PAMs) from BacMam-F1-immunized pigs were significantly stronger than that from rAd-F1-immunized pigs. The similar expression patterns of S-IgA-promoting cytokines were also detected in their lung lavages. After pretreating ASFV with different samples from immunized pigs, significant inhibitory effects were detected in tracheal washes, lung lavages and PAM cultures, but not serum samples with slight inter-group difference. These data suggest that the pseudotyped surface-displaying BacMam vector is more suitable for swine mucosal immunization.