Effect Of TAP Haplotye Specific Pathogen-Free Ducks On Duck Plague Infection

The transporter associated with antigen processing（TAP）plays a key role in the major histocompatibility complex（MHC）class I molecule antigen presenting pathway.The polymorphism of Tap is associated with disease specific susceptibility.In this study,a Tap genotypic test PCR method was established based on HBK-SPF breed ducks reserved at National Laboratory Animal Resource of Poultry,and used to detect the genetic stability of the present B2,B3 and B4 duck lines of F3 generation.The results showed that the genetics characterictics of Line B2 and B4were completely identical to the F0 generation,but there appeared 2 genotypes in the Line B3 population,indicating that once genetic contamination might occur during the previous breeding process.The recombinant protein containing Line B2 duck TAP peptide binding domain expressed by E.coli was used to prepare TAP specific monoclonal antibody,named as 1A6.The antigenic epitope against 1A6 was identified roughly at ²⁹⁷NARHQMLQQAVLDATAGTGMVVQEAI³2222 by trimmed expressed fusion protein of TAP.Duck peripheral blood lymphocytes was tested positive by 1A6 in indirect immunofluorescence assay.Duodenum of SPF white Leghorn chicken,mallard duck,SPF Landrace pig,coturnix and goose were detected with immunohistochemistry assay by 1A6,and the specific strong signals were only detected in both chicken and duck.Specific immune gold particles could be observed by immuno-electron microscope at the nuclear membrane in duck intestine cells from one duck plaque vaccine immuned-virus challenged duck.Seven-day-old B2,B3,and B4 and one closed breed population of SPF Jinding duck（JD）were challenged with duck enteritis virus（DEV）standard virulent strain of CSC.B3 ducks died on 2 dpi,48 h earlier than JD ducks.The DEV UL6 gene copies in dead ducks’cecal were the highest among challenged groups;the transcriptional level of MHC class I molecule heavy chain-coding genes,IFN-α,IFN-βand IFN-γin B3duodenum was higher than the other three strains.The content of IgA was highest in the Harder’s glands of B3.Seven day-old B2,B3,and B4 and JD ducklings were inoculated with DEV attenuated vaccine（K-CKCE strain）.TAP was detected in the intestinal mucosa of B2,B3 and B4 ducks on 0 and 14d by immunohistochemistry assay with 1A6,but not for JD duck until 14 dpi.DEV copies in the cecum of B3 duck was the lowest on 14 and 28 d,and JD was the highest.The IgA level was higher in the B2 ducks on 14 dpi and28 dpi than that in other groups.The transcription levels of MHC I,IFN-α,IFN-βand IFN-γand IgA in B2ducks decreased first,then increased fastest.The study suggested that Tap haplotype HBK-SPF ducks and JD-SPF ducks responsed differently to virulent duck plague virus and weak vaccination,and B3 line is susceptible to virulent DEV infection,while B2 line is more responsive to vaccination virus.This study will provide a basis for selecting disease-susceptible SPF ducks.