Oral immunization with live Lactococcus lactis expressing rotavirus VP8* subunit induces specific immune response in mice

Rotaviruses are the major cause of worldwide infectious diarrhea in children and vaccination is considered to be the most effective way to control these infections. The development of a mucosal live vaccine using the food-grade lactic acid bacteria Lactococcus lactis as antigen vehicle is an attractive and safe vaccination strategy against rotavirus. In this study, the construction of recombinant L. lactis strains able to produce the rotavirus spike-protein subunit VP8* in cytoplasmic, secreted and cell wall-anchored forms is reported. Evaluation of the immune response generated after immunization was conducted in a mouse model. The present study shows that animals inoculated orally with the L. lactis strain producing the cytoplasmic form of VP8* (LL1) developed significant levels of intestinal IgA antibodies while animals receiving L. lactis producing the cell wall-anchored VP8* form (LL3) exhibited anti-VP8* antibodies at both intestinal and systemic levels. Furthermore, it was observed that intestinal antibodies of the LL1-treated group and serum antibodies of the LL3-treated group were able to block rotavirus infection by 50% and 100%, respectively. These encouraging results represent a step towards the development of a new and safe mucosal vaccine against rotavirus.