SUMMARYA total of 41 antibody-secreting hybridoma cells against the HPRS24 strain of Marek's disease virus (MDV) type 2 (MDV2) have been isolated. Of these monoclonal antibodies (MAbs), 24 were found by immunofluorescence tests to react specifically with MDV2-infected cells, but not MDV type 1 (MDV1)-or herpesvirus of turkeys (HVT)-infected cells, while eight reacted with MDV1-or MDV2-infected cells and nine with MDVI-, MDV2-or HVT-infected cells. By using these MAbs, seven classes of MDV type-specific or cross-reactive polypeptides were characterized by immunoprecipitation followed by SDS-PAGE. Among them, a 28K/32K glycoprotein differed from the previously identified gA and gB. The 28K/32K glycoprotein was found on the surface of MDV2-infected cells and in the cytoplasm by an immunofluorescence test with MAbs. In addition, a cross-reactive polypeptide of 25K/29K was also detected in MDVl-infected cells with MAbs reactive with the 28K/32K glycoprotein of MDV2.

For identifying virus-specific antigens of Marek's disease virus (MDV), monoclonal antibodies (MAbs) against strain Md5 of serotype 1, which is known to be a very virulent MDV (vvMDV), were isolated. Fifty-eight hybridoma clones that secreted MAbs against vvMDV were obtained. Of these MAbs, 36 gave positive reactions in an immunofluorescence (IF) test, and 22 gave positive reactions on enzyme-linked immunosorbent assay (ELISA). None of these MAbs gave positive reactions in both the IF test and ELISA. Of the MAbs that gave positive reactions in the IF test, 33 clones reacted with MDV1-specific epitopes, the other three reacting with MDV1-HVT intertypic epitopes. None of the clones reacted with MDV1-MDV2 intertypic epitopes. Three virus-specific polypeptides were identified by radioimmunoprecipitation and sodium dodecyl sulfate-polyaciylamide gel electrophoresis (SDS-PAGE) or immunoblotting. These polypeptides were recognized by 12 MAbs giving positive reactions by IF, but by none of those giving positive reactions by ELISA. In addition, size heterogeneity of the MDV1-specific phosphorylated polypeptides in the MDV1 strains was shown using the MAbs against Md5.

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The post-translational events leading from the precursor to the processed forms of a glycoprotein with an Mr of 28K to 32K (gp28/32) of Marek's disease virus (MDV) serotype 2 were examined with pulse-chase experiments and treatment with tunicamycin and monensin. Cell-free translation of infected cell mRNA followed by immunoprecipitation analysis suggested that a polypeptide with a size of 22K is the initial precursor. Experiments with endo-fl-N-acetylglucosaminidase H and endo-fl-N-acetylglucosaminidase F indicated that gp28/32 contains mostly N-linked oligosaccharides of the complex type. These studies showed that 22K, the initial product, is then processed through intermediates to the 28K to 32K form.