Comparison Of Innate Immune Responses Induced By Duck Hepatitis Virus Type 1 Virulent Strain And Attenuated Vaccine Strain

A series of studies were conducted on the differences between Duck Hepatitis A virus type 1(DHAV-1)virulent infection and attenuated vaccine immunization of ducklings and adult ducks.The results are as follows:1.DHAV-1 virulent infection and attenuated vaccine immunized duck clinical manifestations and microscopic pathological changesThe 7-day-old ducklings and the 160-day-old adult ducks were infected with the DHAV-1 CH strain and the DHAV-1 CH60,respectively.The ducklings died after 24–36 h of infection with DHAV-1 CH strain.The necropsy showed lesions such as hepatomegaly and hemorrhage..Morphological examination revealed liver enlargement,hemorrhage and other lesions.Ducklings and adult ducks were immunized with DHAV-1 CH60 strain and adult ducks infected with DHAV-1 CH strain without any clinical symptoms and necropsy lesions.Ducklings are infected with DHAV-1 CH strain.Histological examination shows obvious hemorrhage in the liver,hepatocyte necrosis and reduction,vacuolatation degeneration;renal tubular epithelial cells swelling and hemorrhage;lymphocytes in the spleen are reduced,inflammatory Cell infiltration.Adult ducks have mild lesions in the liver and spleen after infection with DHAV-1 CH strain.No adult histopathological damage was observed in the liver,spleen and kidney after immunization of DHAV-1 CH60 strain in adult ducks and ducklings.2.Apoptosis and ultrastructural changes of hepatocytes in adult ducks and ducklings induced by DHAV-1Adult ducks and ducklings infected with DHAV-1 CH strain can induce liver cell apoptosis.After 36 hours of DHAV-1 CH infection in ducklings and adult ducks,autophagy and apoptosis-related ultrastructural lesions were observed by electron microscopy.3,DHAV-1 virulent and attenuated vaccine infection / immune adult duck and ducklings tissue organ viral load comparisonIn order to better compare the differences in viral load between virulent and attenuated vaccination/immunized ducklings and adult ducks,this study examined the blood,liver,kidney and spleen of ducklings and adult ducks infected with DHAV-1.Virus proliferation.In the blood,liver,kidney and spleen of ducklings,the virus copy number of DHAV-1 CH strain infection group was significantly higher than that of DHAV-1 CH60 strain immune group,but in adult ducks the viral copy number of the DHAV-1 CH strain infection group and the DHAV-1 CH60 strain immune group were similar.After ducklings and adult ducks were infected with DHAV-1 CH strain and immunized DHAV-1 CH60 strain,the virus copy number in the liver,spleen,kidney and blood of ducklings was higher than that in adult duck liver,spleen,kidney and blood.4.DHAV-1 virulent infection and attenuated vaccine immunized duck liver cytokine expressionPattern recognition receptors(PRRs)mediate innate immune responses by recognizing invading pathogenic microorganisms.The expression levels of TLR-3,TLR-7,RIG-I and MDA5 in ducklings and adult ducks infected with DHAV-1 CH strain and immune DHAV-1 CH60 strain were significantly up-regulated,especially TLR-7.After ducking and adult ducks were immunized with DHAV-1 CH60 strain,both MHC-I and MHC-II were up-regulated,and adult ducks were more up-regulated.Generally,the expression of MHC-I and MHC-II in ducks immunized with DHAV-1 CH60 strain was significantly higher than that of DHAV-1 virulent CH strain.Ducklings infected with DHAV-1 CH strains and immunized against CH60 strains can induce large amounts of transcription of interferons,interleukins and antiviral proteins.The expression of cytokines in duck liver was significantly higher than that in DHAV-1CH60 strain infected with DHAV-1 CH strain,but for adult duck there was no significant difference in the overall expression level of the factors.