Effect Of Duck Hepatitis A Virus Type 3 On The Expression Of Costimulatory Molecule CD80/86 And Th1/2 Immune Response

In recent years,duck viral hepatitis(DVH)caused by duck hepatitis A virus(DHAV-3)is widely spread in China,causing huge losses for the breeding industry.During viral infection,costimulatory molecules and Th1/2 immune response participate in the antiviral process of the body and provide immune protection for the body.In this study,the effects of DHAV-3 on the costimulatory molecules CD80/86 and its mediated Th1/2 immune response in ducks were studied in vitro and in vivo,and the following results were obtained1.Effects of DHAV-3 on the expression of costimulatory molecules CD80/86 and Th1/2 immune response in cultured duck cellsAfter Poly(I:C)stimulation of peripheral blood mononuclear cells(PBMC)of duck for 48 h and 72 h,transcription levels of costimulatory molecules CD80/86 and Th1 cytokine IFN? and Th2 cytokine IL-4 was detected by qRT-PCR.Then the CD80 and CD86 antibodies were used to block costimulatory signal separately,the results showed that the transcription levels of IFN?and IL-4 were significantly decreased after blocking the costimulatory signal.It was proved that CD80 and CD86 were involved in the activation of Th1/2 type immune response.Then the PBMC was infected with DHAV-3 virulent strain,the results indicated that DHAV-3 virulent strain significantly stimulated the expression of CD80/86,and the transcription of IL-4 and IFN? were significantly up-regulated at 48 h.This suggests that DHAV-3 can induce the expression of CD80/86 and activate Th1/2 immune response.2.Effects of DHAV-3 on the expression of CD80/86 and Th1/2 immune response in ducklingsIn this study,the virulent and attenuated strain of DHAV-3 were used to infect ducklings respectively.The results of qRT-PCR and immunohistochemistry showed that although the expression of costimulatory molecules CD80/86 and the transcription of Th1/2 cytokines in the liver of virulent strain group were up-regulated before 48 h,the level of up-regulation was relatively low,and there was significant upregulation at 72~120 h.In the spleen,the expression of CD80/86 were significantly up-regulated at 36 h and induced Th1/2 immune response.Histopathological results showed that the liver and spleen lesions were more serious at 24~48 h,and gradually reduced after 48 h.However,in the liver and spleen of the ducklings in attenuated strain group,the expression of CD80/86 and the transcription of Th1/2 cytokines were significantly up-regulated at the early stage(before 48 h),and the upregulated levels was higher than that in virulent strain group except IFN?.The transcription level of IFN? in the spleen was lower than that in virulent strain group.Histopathological results showed that no lesion was found in the liver and spleen of the ducklings in attenuated strain group.The above results show that the costimulatory molecules CD80/86 is involved in the activation of the Th1/2 type immune response.DHAV-3 can induce the expression of CD80/86 in PBMC and activate the Th1/2 immune response.DHAV-3 attenuated strain can induce higher up-regulation levels of costimulatory molecules CD80/86 and Th1/2 cytokine in the liver than those of virulent strain,which may be the reason DHAV-3 attenuated strain can produce immune protection to the body.