Chicken CH25H Exerts Antiviral Activity Against ALV-J Via Catalyzing The Production Of 25-HC

Interferon-stimulated genes(ISGs)are large group of antiviral genes in the host.Cholesterol 25-hydroxylase(CH25H)is an identified ISG,but there are few studies on CH25 H resistance to subgroup J avian leukemia virus(ALV-J).ALV-J has much higher pathogenicity and infectivity than other subgroups in chickens,leading to significant economic losses in the poultry industry.Therefore,it is of great significance and potential application valuable to analyze the mechanism of host virus resistance and to select chicken varieties with disease resistance ability that verified the function of classical ISGs for antiALV-J in chicken.In the present study,we found that in 1 day chicks treated with IFNα before infected ALV-J,the virusemia S/P values were lower than that in chicks directly infected ALV-J.IFNα treatment and ALV-J infection could induce the up-regulation of CH25 H and OAS expression.Besides,in chicken DF-1cells,CH25H(6 h),OAS(6 h,24 h),PKR(6 h,24 h,48 h),ZAP(6 h,24 h,48 h),STAT1(6 h,24 h,48 h),ISG12(6 h,24 h),were up-regulated by IFNα treatment.In order to investigate anti-ALV-J activity of these genes,we overexpressed CH25 H,OAS,PKR,STAT1,ISG12 in DF-1 cells and then made the cells infected with ALV-J.As a result,the overexpression of CH25H(48 h),OAS(24 h,48 h),PKR(48 h),STAT1(48 h),ISG12(24 h,8 h)significantly down-regulated gp85 expression of ALV-J.It suggested that the 5 ISGs have the function of anti-ALV-J.Summarily,CH25 H was inferred as an anti ALV-J ISG.Overexpression of CH25 H remarkably suppressed ALV-J replication,whereas knocking out the endogenous CH25 H by CRISPR/Cas9 significantly promoted ALV-J replication.Treatment with 25-hydroxycholesterol(25HC)pre-infection significantly inhibited ALV-J infection in both DF-1 cells and CH25 H knock down DF-1 cells.In conclusion,CH25 H exerts antiviral activity against ALV-J via catalyzing the production of 25-HC.