Construction and immunological protection analysis of attenuated Salmonella typhimurium harbouring Helicobacter pylori oipA DNA vaccine / 中国免疫学杂志

ABSTRACT

Objective: To optimize Helicobacter pylori(H.pylori)oipA gene and develop strain of vaccine in Attenuated Salmonella typhimurium SL7207 haxboring recombinant plasmid pVAX1-oipA and pVAX1-optioipA, then to study its protection against H.pylori in C57BL/6 mice.Methods: oipA gene was modified by codon optimization,inserting the Kozak sequence and engineering CpG motifs.The optioipA gene and oipA gene was inserted into the eukaryotic expressing vector pVAX1 respectively to develop recombinant plasmid pVAX1-optioipA and pVAX1-oipA.The AGS cells were transfected by pVAX1-oipA,pVAX1-optioipA and pVAX1 respectively.Then the OipA protein expression was confirmed by Western blot.pVAX1-oipA,and pVAX1-optioipA were converted to LB5000 for methylation and then the modified eukaryoticvector was electrotransfered to final host SL7207 respectively, SL7207/pVAX1-oipA, SL7207/pVAX1-optioipA was identified with PCR and enzyme digestion.Specific serum IgG antibody was detected by indirect ELISA after oral inoculation with vaccine strains.Mice were challenged with live Sydney strain(SS1)three times at 0,2,4 d(5 × 10~8CFU/each mouse).Fonr weeks after challenge, the mice were sacrificed.The colonization of H.pylori in gastric mucosa were detected by rapid urease test and quantitative culture of H.pylori.Results: The AGS cells transfected with pVAX1-oipA and pVAX1-optioipA had expressed corresponding production, moreover, the expression level of pVAX1-optioipA was higher than those of pVAX1-oipA,SL7207/pVAX1-oipA and SL7207/pVAX1-optioipA confirmed with PCR,enzyme digestion;Two weeks after last immunization,immunized mice.were induced to produce anti-OipA IgG antibodies, and the levels of anti-OipA IgG antibody in pVAX1-optioipA group was obviously higher than in pVAX1-oipA group(P＜0.01); After challenged with SS1, the infection rate of pVAX1-oipA and pVAX1-optioipA group was 60%(9/15)and 26.67%(4/15), which was significantly lower than 100%(10/10)in the control group(P＜0.01).Conclusion:Attenuated Salmonella typhimurium SL7207 containing pVAX1-oipA, pVAX1-optioipA is successfully constructed.It can protect mice from H pylori infection and optimizing oipA gene can enhance the protection efficiency.