Characterization of monoclonal antibodies against duck hepatitis type 1 virus VP1 protein

The VP1 protein of duck hepatitis type 1 virus (DHV-1), one of the major structural proteins, is able to induce neutralizing antibody in ducks, but a monoclonal antibody (mAb) against VP1 protein has never been characterized. Four hybridoma cell lines secreting anti DHV-1A VP1 mAbs were prepared and designated 2D9, 2D10, 5F7, and 3E8. Immunoglobulin subclass tests differentiated them as IgG1 (2D9 and 2D10) and IgG2b (5F7 and 3E8). Dot blot and western blotting assays showed that mAbs reacted with His-VP1 protein in a conformation-independent manner. Competitive binding assays indicated that mAbs delineated three epitopes, namely A, B and C, of VP1. Immunofluorescence assays indicated that mAbs could specifically bind to duck embryo fibroblast (DEF) cells infected with DHV-1A. mAbs 2D9, 2D10, and 5F7 had universal reactivity to heterologous DHV-1As tested in an antigen-capture ELISA, suggesting that they are highly conserved among DHV-1As. An antigen-capture ELISA could detect DHV-1A protein VP1 with a clear difference in absorbance values between the liver samples of DHV-1A- and mock-infected birds, indicating that the mAb capture ELISA is a useful method for the detection of DHV-1A infections.