Interferon as a Mucosal Adjuvant for an Influenza Vaccine in Pigs

Interferon, a natural protein that is produced by a variety of cells during viral infection, activates the transcription of multiple functional genes in cells, regulates synergy among various signaling pathways, and mediates many biological functions such as antiviral activity, immune regulation, and cell growth. However, clinical research on interferon in livestock is lacking. In this study, recombinant porcine interferon (PoIFN) was used as an adjuvant, in combination with inactivated influenza virus, to vaccinate 6-week-old pigs via nasal infusion. The transcription of target genes was then monitored and the functions of PoIFN were determined with respect to the activation of mucosal immunity. We found that a combination of low-dose PoIFN and inactivated influenza virus could significantly up-regulate the expression of immunoregulatory cytokines such as IL-2, IL-18, IFN-, IL-6, and IL-10 by real-time PCR, suggesting the induction of a strong mucosal innate immune response after administration. In addition, low-dose PoIFN can significant enhancing the transcription of genes encoding homing factors including CCR9 and CCR10 (P<0.001), thereby resulting in the induction of higher levels of HA-specific antibodies (P<0.05), which can be determined by ELISA and IFA. Post-immunization challenges with H1N1 virus demonstrated that PoIFN, combined with inactivated influenza virus, could alleviate clinical signs in pigs during the early stages of viral infection. These studies reveal low-dose PoIFN as a potential mucosal adjuvant for influenza virus in pigs.