Cytotoxic T lymphocyte antigen 4 (CTLA-4) is an inhibitory T cell receptor predominately expressed on activated T cells and plays an important role in regulation of specific T cell responses to viral infection. The woodchuck model is an informative animal model for hepatitis B virus (HBV) infection. In this study, the extracellular region of woodchuck CTLA-4 (wCTLA-4) was cloned and the fusion protein of GST-wCTLA-4 was expressed and purified. Polyclonal antibody against GST-wCTLA-4 (anti-GST-wCTLA-4) was prepared. The full length wCTLA-4 protein expressed in transfected baby hamster kidney cells was detected by anti-GST-wCTLA-4 in western blot analysis and immunofluorescence staining. Anti-GST-wCTLA-4 provides a useful tool to study the role of CTLA-4 in T-cell response in the woodchuck model. Further, the blocking of CTLA-4 with anti-GST-wCTLA-4, as a novel therapy approach for chronic hepatitis B virus infection, could be studied in woodchuck model now. (C) 2011 Elsevier Inc. All rights reserved.