| Acinetobacter baumannii has become one of the most common "super bacteria" due to its resistance to most antibiotics,it often causes serious diseases such as respiratory tract infection,bacteremia,and meningitis.Therefore,there is urgent for taking solutions to prevent the transmission and infection ofAcinetobacter baumannii,while the development of vaccines is the most effective way.Currently,the inactivated vaccines,DNA vaccines and recombinant subunit vaccines againstAcinetobacter baumannii are under study,but none of them have entered the stage of clinical trials.Moreover,the existing vaccines have a lot of disadvantages such as the long cycle,weak immunogenicity and low safety,so,it need to develop effective vaccines for the prevention ofAcinetobacter baumannii infection.In the previous work of our research group,an attenuated Salmonella vector vaccine χ9241 was developed,which has adjuvant property,and can carry foreign antigens to colonize the immune organs of the body to induce a strong immune response.Therefore,in this study,we developed a vaccine based on χ9241 againstAcinetobacter baumannii infection.In this study,according to the biological characteristics and outer membrane structure ofAcinetobacter baumannii,the outer membrane proteinA(OmpA)was selected as the vaccine antigen,and a protein vaccineAb TompA and a recombinant attenuated Salmonella vector vaccine χ9241-rompA were designed according to the epitope analysis results of OmpA protein.In order to get the stronger immunoprotection,we choose a heterologous prime-boost strategy,combining the χ9241-rompA andAb TompA vaccine,expecting to induce a stronger immune response to protect mice against challenge withAcinetobacter baumannii.The main experimental contents and results of this study are as follows:1.The epitope ofAcinetobacter baumannii OmpA was analyzed by bioinformatics method,and the full-length OmpA protein ofAcinetobacter baumannii(Ab FompA),theAcinetobacter baumannii OmpA protein vaccine(Ab TompA)and the recombinant attenuated Salmonella vector vaccine(χ9241-rompA)were constructed respectively.Notably,Ab FompA was used to immunize rabbit to get positive serum for subsequent protein identification assays.2.χ9241-rompA andAb TompA were combined to immunize BALB/c mice to evaluate the immune response induced by prime-boost strategy in mice.Compared to the χ9241-rompA orAb TompA vaccine,the combined vaccines could induce higher levels of anti-OmpA total Ig G and mucosal IgA,and also induce a more balanced Th1/Th2 immunity.Moreover,the more higher cell proliferation ratio and the production of IFN-γ were observed in mouse splenocytes after theAb FompA stimulation.Meanwhile,all vaccine groups could activate DC,B cells,and increase the ratio of CD4+ T cells and Th17 cells.3.Compared to the χ9241-rompA orAbTompA vaccine,the serum of the combined vaccines could significantly inhibit the biological activities ofAcinetobacter baumannii,including the abilities of adhesion,migration and biofilm formation.4.Acinetobacter baumannii-induced systemic sepsis and pulmonary inflammation models were used to evaluate the effect of the vaccine protection against challenge with standard strains and drug-resistant strains in mice.The results showed that the combined immunization group of χ9241-rompA andAb TompA could improve the survival time of mice,reduce the level of serum cytokine IL-6,and alleviate the pathological damage of lung tissue.Collectly,this study not only provides a variety of candidate vaccines forAcinetobacter baumannii research,but also provides a new experimental basis for the development of recombinant attenuated Salmonella vector and the application of primeboost immunization strategy. |
PDF Full Text Request