Identification of the gene encoding Marek's disease herpesvirus A antigen

The gene encoding the glycoprotein Marek's disease herpesvirus A antigen (MDHV-A) precursor polypeptide pr47 was delineated by using Northern blot (RNA blot) analysis and hybrid selection of its mRNA with cloned MDHV DNA, cell-free translation of the mRNA, and immunoprecipitation of the polypeptide. The resulting piece of DNA with strongly positive hybrid selection results was a 2.2-kilobase-pair (kbp) PvuII-EcoRI restriction fragment localized to the center of the 18.3-kbp MDHV BamHI B fragment of the total virus genome. The localization was specific since no other small restriction subfragment of the larger BamHI B fragment was able to hybrid select significant MDHV-A mRNA and the gene mapped only in the BamHI B fragment of the total virus genome. Northern blot analysis confirmed the localization of the MDHV-A gene on the 2.2-kbp fragment and detected its mRNA as a 1.8-kilobase species, a size consistent with encoding a 47-kilodalton polypeptide. This is the first report of an MDHV gene being mapped to the MDHV viral genome. This opens the way for the use of recombinant DNA technology to study the nature of the gene encoding a secreted virus-specific glycoprotein that could possibly be involved in immunoprevention, immunosuppression, or immunoevasion, immune phenomena known or speculated to be involved in this oncogenic herpesvirus system.