Preliminary study about sublingual administration of bacteria-expressed pandemic H1N1 influenza vaccine in miniature pigs

Sublingual (SL) administration of influenza vaccine would be non-invasive and effective way to give human populations protective immunity against the virus, especially when pandemic influenza outbreaks. In this study, the efficacy of pandemic influenza virus-based subunit vaccines was tested after sublingual (SL) adjuvant administration in pigs. Eight specific pathogen-free Yucatan pigs were divided into 4 groups: nonvaccinated but challenged (A) and vaccinated and challenged (B, C, and D). The vaccinated groups were subdivided by vaccine type and inoculation route: SL subunit vaccine (hemagglutinin antigen 1 HA1] + wild-type cholera toxin wtCT], B); IM subunit vaccine (HA1 + aluminum hydroxide, C); and IM inactivated vaccine (+ aluminum hydroxide, D). The vaccines were administered twice at a 2-week interval. All pigs were challenged with pandemic influenza virus (A/swine/GCVP-KS01/2009 H1N1]) and monitored for clinical signs, serology, viral shedding, and histopathology. After vaccination, hemagglutination inhibition titre was higher in group D (320) than in the other vaccinated groups (40–80) at the time of challenge. The mobility and feed intake were reduced in group C. Both viral shedding and histopathological lesions were reduced in groups B and D. Although this study has limitation due to the limited number of pigs (2 pigs per a group), the preliminary data in this study provided the protective potential of SL administration of bacteria-expressed pandemic H1N1 influenza vaccine in pigs. There should be additional animal studies about effective adjuvant system and vaccine types for the use of SL influenza vaccination.