Oral immunization of mice using Bifidobacterium longum expressing VP1 protein from enterovirus 71

Bifidobacterium longum is an attractive candidate for delivering biologically active proteins by the mucosal route due to its non-pathogenic and colonizing properties. Enterovirus 71 (EV71) has aroused widespread attention recently due to several epidemics, and great attention should be paid to the fact that there are currently no effective antiviral drugs or vaccines against EV71 infection. In this report, we described a recombinant B. longum that could be used to develop an oral vaccine against EV71 infection. A VP1 expression vector (pBBADs-VP1) was constructed by amplifying the EV71 VP1 gene and inserting it into the E. coli-Bifidobacterium shuttle expression vector pBBAD/Xs. Then, the expression of VP1 protein in pBBADs-VP1-transformed bacteria was demonstrated by western blot. In vivo studies indicated that oral immunization of BALB/c mice with pBBADs-VP1-transformed bacteria induced potent immune responses against EV71 infection, including virus-neutralising titers, anti-EV71-VP1 antibody and the induction of Th1 immune responses in the spleen and Peyer's patches. Importantly, immunization of mother mice with this recombinant VP1-expressing B. longum conferred protection to neonatal mice. These results demonstrate that the novel oral vaccine utilizing B. longum expressing the VP1 protein might successfully elicit a specific immune response against EV71 infection.