Expression Of Helicobacter Pylori NapA Gene In Lactococcus Lactis And Its Immunogenicity Analysis

Helicobacter pylori is a Gram-negative microaerophilic bacillus that infects the stomachs of more than half of the global population.It has been confirmed that H.pylori is the main cause of chronic gastritis and peptic ulcer disease,and has a close relation to gastric mucosa-associated lymphoid tissue(MALT) lymphoma and gastric adenocarcinoma.The World Health Organization defined it as a class 1 carcinogen. Vaccine will be an effective and economic approach to prevent infection diseases of mass population.H.pylori neutropphil-activating protein(HP-NAP) is localized in the bacterial cytosol and is released upon autolysis.It can bind to the external surface of the outer membrane and mediate the binding of H.pylori to the cell surface.NAP has also been shown to be chemotactic for neutrophils and monocytes,which contribute to H. pylori-induced gastritis.It is able to bind and even condense DNA at slightly acid pH values to protect DNA against damage.NAP is a virulence facter important for the survival,colonization and inflammation of H.pylori.Lactococcus lactis is a Gram-Positive food-grade bacterium and has a long history of widespread use in the food industry for the production of fermented milk products. And it can stimulate a mucosal immune response as a adjuvant in the intestinal tract. Lactococcus lactis is approximately the same size as biodegradable microparticles that are known to be taken up by M cells and have been shown to be capable of acting as effective oral vaccine vehicles.In this study,the napA gene was amplified and clone into the prokaryotic expressive vector pNICE:sec.The recombinant vector was transformated into Lactococcus lactis strain NZ9000.The fusion protein(17kDa) was expressed in L.lactis by the induction of the nisin.The quantity of expression accounted for 9.5%of the total bacterial protein.Western bolt analysis confirmed that fusion protein could be recognized specifically by the serum of anti-H.pylori.The recombinant L.lactis expressing NAP protein was used to vaccinate mice and the specifical IgA and IgG was elicited. These results suggest that the recombinant L.lactis can elicit the local mucosal and the systemic immune response delivered through oral route.This may be useful for the precaution and eradication of the infection of H.pylori.So this recombinant L.lactis may be a good vaccine in the future.These results would be helpful for the development of oral vaccine against H.pylori.