Study On The Immunological Characteristics Of Vaccine Inoculation Of Chlamydia Abortus In A Mouse Model Of Infection

Chlamydia abortus?C.abortus?infects the placenta of several mammals,which leads to inflammation,tissue damage,abortion and stillbirth in the late pregnancy.C.abortus is also a kind of zoonoses and the people who was contect with infected animals will have an abortus.Normally,the abortion rate of the sheep for the first infection of C.abortus is more than 30%,and will down to 5%-10%for untreated sheep,which cause the huge economy loss in animal husbandry.Vaccine,as one of the tools to prevent pathogens,plays a very important role in animal diseases control.The inactivated vaccine of C.abortus is no exception.However,a very interesting phenomenon we found in clinical field that the abortion from infected yaks would down sharply if the inactivated vaccine was used.It seems that a kind of treatment function exist.In order to confirm the vaccina whether has the ability to inhibit the C.abortus replication in infected animal or not,Balb/c mice were used as animal model.A specific primers were designed according to the conserved sequence of the large cysteine-rich periplasmic protein?envB?of C.abortus and the EnvB-PMD19T positive plasmid was used as the reference described.The qPCR of optimization condition,sensitivity,specificity,repeatability and the bacteria loads of organs from mouse have been done.The results show that the standard curve established with positive plasmid had a liner response from 1×10² copies/?L to 1×10⁶ copies/?L with the correlation coefficient of 97%.The sensitive assay showed that the detection limit of C.abortus was 10copies/?L.The repeatable and stable experiments showed that the coefficients of variation less than2%.In this study,Balb/c mice were infected by C.abortus through intraperitoneal injection and gastrointestinal route.The real-time quantitative PCR was used to detect the C.abortus from different tissues and the results showed that the genome copies of C.abortus in spleen,uterus,liver and duodenum were higher than that of other tissues at 14^th days after infection.The number of genome copies of C.abortus in different tissues has differences at some point.But the pattern of colonization and reproduction of C.abortus in the same tissues was exactly the same.In this experiment,the treatment mechanism of the inactivated vaccine of C.abortus from ewe was evaluated preliminary through Balb/c mice.The infected mice were inoculation with the inactivated vaccine 0?L?C?,50?L?LD?and 100?L?HD?of C.abortus and the genome copies of C.abortus,pathological reactions,immunohistochemistry responses were measured in liver,lung,uterus,spleen besides the antibody titer was detected.The results showed that LD group exhibited less genome copy,lower immunohistochemistry?IHC?positive labelling,and high antibody titer as well as HD group compared to C groups.Cytokines in the first week of testing,the anti-inflammatory cytokine?IL-4?of HD group was decreased gradually,whereas the IL-4 of LD group was higher than that of HD group and C group,and the level of IL-6 and TNF-?of HD group was higher than that of LD group and C group.In addition,the pro-inflammatory cytokine TNF-?was not detected in LD group.According to the results,low dose of inactivated vaccine can inhibit the replication of C.abortus from infected mice again through antibody,cytokine.To sum up,the real-time quantitative PCR method of C.abortus was successfully established in this study.Based on this method,it was proved that Chlamydia inactivated vaccine could inhibit the proliferation of Chlamydia in infected mice.It is better guidance for the inactivated vaccine of C.abortus to be used in clinical field.