Epitopes on glycoprotein E and on the glycoprotein E/glycoprotein I complex of bovine herpesvirus 1 are expressed by all of 222 isolates and 11 vaccine strains

Glycoprotein E (gE) of bovine herpesvirus 1 (BHV1) forms a complex with gly coprotein I (gI) and plays an important role in cell-to-cell spread mechani sms of the virus, but is not essential for propagation of the virus. To stu dy the antigenic variability of BHV1 glycoprotein E, a set of six well char acterised monoclonal antibodies (MAbs) was established using BHV1 gE and gI deletion mutants, eukaryotically expressed gE and gI and pepscan analysis. Two of these MAbs reacted with a linear gE epitope (MAbs 3 and 52), two re acted with a more conformation dependent gE epitope (MAbs 61 and 81) and tw o reacted with epitopes formed by a complex formed between gE and glycoprot ein I (MAbs 67 and 75). With these six MAbs the gE expression of 222 BHV1 i solates and 1 1 BHV1 modified-live vaccine strains was studied in vitro, us ing an immunoperoxidase monolayer assay. All 222 BHV1 isolates and II vacci ne strains were found to react with MAbs 61, 81 and 75. Three of the 222 is olates failed to react with MAb 67 and two of the vaccines reacted very wea kly with MAbs 3 and 52. Analysis of the gE genes of these five aberrant iso lates and the gE glycoproteins they expressed, did not show obvious size di fferences compared to wild-type BHV1. We conclude that the tested gE epitop es are highly conserved, including the epitopes formed by the gI/gE complex .