Characterization and expression of the Marekʹs disease virus serotype 2 glycoprotein E in recombinant baculovirus-infected cells: initial analysis of its DNA sequence and antigenic properties

In Marekʹs disease virus (MDV) serotype 2 (MDV2) genome, a gene equivalent to the glycoprotein E (gE) of other alphaherpesviruses was identified and sequenced. The primary translation product comprises 488 amino acids with a Mr of 54.3 kDa. The predicted amino acid sequence possesses several characteristics typical of membrane glycoproteins, including a N-terminal hydrophobic signal sequence, C-terminal transmembrane and cytoplasmic domains, and extra-cellular region containing four potential N-linked glycosylation sites. Compared with other MDV serotypes, MDV2 gE showed 47.3% identity with MDV1 gE, and 38.9% identity with HVT gE at the amino acid level. In transcriptional analyses, a 2.0 kb mRNA which starts between 65 and 86 bps upstream of the potential translational initiation codon of gE was identified as the gE-specific transcript. By a recombinant baculovirus, this potential gE coding region was expressed as several specific products from 66 to 72 kDa. These products were susceptible to tunicamycin treatment, indicating that they were glycoprotein in nature. Further, the expressed gE reacted with all chicken-antisera raised to each of the three serotypes of MDV (strains GA, SB-1, and FC126), suggesting that gE is expressed by all three serotypes of MDV in infected cells and conserves common antigenic epitope(s) beyond those that are serotype specific.