The Qinghai-tibet Plateau Yak Abortion Chlamydia Isolates Immunogenicity And Immune Protection Experiment

Chlamydia are obligate intracellular parasites,blindly causing a variety of infections to human beings and animals worldwide.There are three Chlamydia that infect yaks,the Chlamydia abortus(C.abortus),the Chlamydia psittaci(C.psittaci)and the Chlmydia pecorum(C.pecorum).Among which,C.abortus can induce abortion or reproductive disorders to yaks.Chlamydial abortion was seriously hindered the yak production industry,caused enormous economic losses to people living pasturing area.Therefore,prevention and control of chlamydiosis have great significance to public health and economic growth.This study has investigated the epidemiology of Chlamydia infections in yaks.Serum samples of yaks were collected from several counties in Qinghai province,and subjected to Indirect Hemagglutination Assay(IHA)and PCR detection.Results showed the Chlamydia infection in yaks was extremely serious,that in 2014,the positive rate of IHA and PCR for Chlamydia infection were 24.02% and 23.8%,respectively.While in 2015,the IHA and PCR were 55.76% and 41.67%,respectively.The research examined the samples from abortion yaks,and six strains of Chlamydia were isolated from Guinan county(GN)and Haiyan county(HY)through inoculating the samples into the SPF chick embryo yolk sac.The following PCR-RFLP analysis indicated the strain GN-1,GN-4,GN-6 and HY-1 was consistent with the standard C.abortus strain SX5 and were confirmed as C.abortus.And interestingly,the other two strains,the virulence of the isolate reached 10-10 and appeared virulence stable.Evaluation of a killed C.abortus vaccine was tested in BALB/c mice.Briefly,a Chlamydia strain(GN-6)isolated from Guinan county was inactivated with formaldehyde,and “206” was taken as adjuvant.Vaccination on BALB/c showed the IgGs was mainly IgG1 with light ? chain.Compared with the control group,IFN-? was up-regulated in serum and in the supernatant of cultured lymphocytes from the vaccinated mice.DTH examination indicated a thicker foot pad and a higher lymphocyte proliferation index.These results proved the Th1 type cell immune response was triggered in the vaccinated mice,which greatly contributed to the elimination of Chlamydia infection.The antibody neutralization tests prompt that protective antibody was raised in the vaccinated mice.Meanwhile,the vaccinated mice was protected during the challenge test.The above results safely made the conclusion that the immunized mice was successfully induced specific cellular immune response and humoral immune response.The killed C.abortus vaccine was also tested on yaks.The results showed the inactivated vaccine was proved safe and reliable,with 1 ml for calves 2 for adult yak were sufficient to induce strong protection.The results of immune duration showed the titer of the specific IgGs for the killed C.abortus vaccine was as high as 1:856 at 210 days after immunization.The conservation of the vaccine was in progress,which was kept at 2 to 4 °C for one year,and the immunization was carried out since Aug,2016,and the immune antibody titer,the immune effect is better.In summary,this study investigated the prevalence of yak chlamydiosis,and obtained four chlamydia strain.The killed vaccine tested was proved effective and laid a foundation for prevention and control of chlamydiosis.