Oral immunization with recombinant Lactococcus lactis delivering a multi-epitope antigen CTB-UE attenuates Helicobacter pylori infection in mice

Urease is an essential virulence factor and colonization factor for Helicobacter pylori (H.pylori) and is considered as an excellent vaccine candidate antigen. However, conventional technologies for preparing an injectable vaccine require purification of the antigenic protein and preparation of an adjuvant. Lactococcus lactisNZ9000 (L.lactis) could serve as an antigen-delivering vehicle for the development of edible vaccine. In previous study, we constructed a multi-epitope vaccine, designated CTB-UE, which is composed of the mucosal adjuvant cholera toxin B subunit (CTB), three Th cell epitopes and two B-cell epitopes from urease subunits. To develop a novel type of oral vaccine against H.pylori, genetically modified L.lactis strains were established to secrete this epitope vaccine extracellularly in this study. Oral prophylactic immunization with recombinant L.lactis significantly elicited humoral anti-urease antibody responses (P<0.001) and reduced the gastric colonization of H.pylori from 7.14 +/- 0.95 to 4.68 +/- 0.98 log(10) CFUg(-1) stomach. This L.lactis oral vaccine offers a promising vaccine candidate for the control of H.pylori infection.