The Preliminary Study On Two DNA Vaccines: PVAXl-based SjTGR And SjTSP2of Schistosoma Japonicum

Objective: Schistosomiasis japonicum, caused by infection with Schistosoma japonicum, is a tropical/subtropical zoonosis, with a wide distribution in developing countries and brings serious dangers.Schistosomes are covered by a living syncytium, called the tegument, which is a key interface betweenparasite and host, and also generally be viewed as the most susceptible target for vaccines and drugs. In thispaper, we chosed two tegument proteins, SjTGR and SjTSP2as vaccine candidates and constructed twoDNA vaccines. Then the immunoprotective efficacy of the two DNA vaccines was estimated in theBALB/c mice model.Methods: Two DNA vaccines were constructed and the recombinant plasmids were transfected into293Tcells using lipofectamine2000. IFA was performed to detect the expression of protein of interest. BALB/cmice were inoculated with two different ways, particle bombardment and needle inoculation to estimateimmune efficacy. Special antibodies were tested by ELISA and cytokines were detected by FCM. AThioredoxin Reductase Assay Kit was used to detect the enzymatic activity of SjTGR.Results: IFA result shows that the two genes express well in293T cells. Mice immunized withpVAX1/SjTSP2were induced both special IgG antibodies and cytokines (IL-4and IFN-γ), which suggestedthat DNA vaccine induced both humoral and cellular immune responses. However, pVAX1/SjTSP2didn’tinduce an ideal protection. BALB/c mice inoculated pVAX1/SjTGR with particle bombardment achieved aprominent reduction of worm burden (27.83%, P<0.05) and liver EPG (40.38%, P<0.05), while animalsimmunized by needle didn’t achieve an ideal protection. Specific IgG antibodies detected by ELISA weresignificantly increased. Meanwhile, mice immunized with gene gun were induced much higher antibodiesthan needle inoculation. The results of another immune protection test show that mice vaccinated withpVAX1/SjTGR achieved a sigmificant reduction of worm burden (38.83%, P<0.05) and liver EPG(44.51%, P<0.05). Enzymatic activation test of SjTGR in vitro implied that SjTGR in the immunized groupexpressed much lower activity than the control groups. Furthermore, anti-SjTGR antibodies can influencethe thioredoxin reductase activity of SjTGR. The results of flow cytometry (FCM) detection show that thepercentages of cells producing IL-4or IFN-γ in the gene gun-vaccinated group increased compared to thecontrol groups.Conclusions: From the results, pVAX1/SjTSP2didn’t induce an ideal protection. But the results suggestedthat pVAX1/SjTGR DNA vaccine can induce significant protection which related to strong humoral andcellular immune responses. It is suggested that SjTGR is a prospective vaccine candidate antigen and ourwork provided useful datas for anti-schistosomiasis vaccine research in future.