Identification of Marek's disease virus‐specific antigens in Marek's disease lymphoblastoid cell lines using monoclonal antibody against virus‐specific phosphorylated polypeptides

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Abstract
For identification of the antigens specific to Marek's disease virus (MDV) in virus‐non‐producer lymphoblastoid cell lines established from a tumor of Marek's disease (MD), hybridomas producing monoclonal antibodies (MABs) against the antigens were isolated. Immunogens for preparation of the hybridomas were purified from the lysate of an MD‐lymphoblastoid cell line, MSB I, by affinity chromatography coupled with chicken anti‐MDV serum immunoglobulin G. Three of the MAbs obtained, MB1, MB2 and MB3, were specific to MDV by immunofluorexence test. An immunofluorexence test using MB2 antibody showed that immunofluorexence‐positive cells in non‐producer MD‐lymphoblastoid line cells became detectable when the culture temperature was shifted from 41° C to 33° C or when treatment with 5‐iodo‐2‐deoxyuridine (IUdR) was performed, indicating that the antigen reactive with MB2 antibody is an MDV‐specific early antigen. This temperature shift of IUdR‐treatment did not induce other MDV‐specific antigens, such as late gene products of MDV, detected with MAbs. MB1 and MB2 antibodies immunoprecipitated 4 MDV‐specific phosphorylated polypeptides with molecular weights (MWs) of 43,000 (43kd), 39kd, 36kd and 24kd from chick embryo fibroblasts productively infected with virulent MDV. In the place of 43kd, phosphorylated 44kd polypeptide was precipitated from avirulent MDV‐infected fibroblasts. However, MB3 antibody did not precipitate any MDV‐specific polypeptides from infected fibroblasts. These results suggest that the phosphorylated polypeptides are MDV‐specific polypeptides predominantly expressed in non‐producer MD‐lymphoblastoid cell lines.