Identification and Characterization of a Bovine Herpesvirus-1 (BHV-1) Glycoprotein gL Which Is Required for Proper Antigenicity, Processing, and Transport of BHV-1 Glycoprotein gH

DNA sequence analysis of the bovine herpesvirus-1 (BHV-1) genome revealed the presence of an open reading frame named UL1 which exhibited limited homology to glycoprotein gL of herpes simplex virus-1 (S. K. Khattar, S. van Drunen Littel-van den Hurk, L. A. Babiuk, and S. K. Tikoo,Virology213, 28–37). To identify the BHV-1 UL1 protein, rabbit antisera were prepared against two synthetic peptides that were predicted by computer analysis to encompass antigenic epitopes. Sera against both peptides immunoprecipitated a 16- to 17-kDa protein fromin vitrotranslatedin vitrotranscribed mRNA, BHV-1-infected MDBK cells, and purified virions. Enzymatic deglycosylation and lectin binding assays confirmed that the BHV-1 UL1 protein contains only O-linked oligosaccharides and was named glycoprotein gL. Sera against UL22 protein immunoprecipitated a protein of 108 kDa from BHV-1-infected MDBK cells and purified virions, which was modified only by N-linked oligosaccharides and was named glycoprotein gH. Glycoprotein gL expressed by recombinant vaccinia virus was properly processed and secreted into the medium. In contrast glycoprotein gH expressed by recombinant vaccinia virus was found to be retained in the rough endoplasmic reticulum. However, gH coexpressed with gL by recombinant vaccinia viruses was properly processed and transported to the cell surface, suggesting that complex formation between gH and gL is necessary for the proper processing and transport of gH but not gL. In addition gH–gL complex formation is also required for induction of neutralizing antibody response and anchoring of gL to the plasma membrane.