Infection of endothelial cells with equine herpesvirus-1 (EHV-1) occurs where there is activation of putative adhesion molecules: a mechanism for transfer of virus.

Evidence is presented to show that activation of endothelial and leucoyte adhesion molecules is a key step in transferring virus from infected leucocytes; and determines the restricted tissue tropism. A range of tissues from 2 experimentally infected mares in late pregnancy at 4 and 8 days after infection with EHV-1 were compared with those from normal pregnant and nonpregnant mares. Rabbit antisera to equine activated endothelial cell molecules were used to identify which tissues expressed these molecules in normal nongravid and gravid mares, and to investigate whether the range of tissues was altered in pregnant mares as a consequence of infection. The results indicated that the endothelium of the pregnant reproductive tract did express these molecules. In the 2 pregnant mares infected with EHV-1, the endothelial cells in the nasal mucosa also expressed these activated endothelial cell molecules. Therefore, the sites expressing these molecules closely correlated with those where virus infection of endothelial cells has been described and is consistent with experimental in vitro data, indicating that expression of these molecules is an essential stage in the transference of virus from leucocytes to endothelial cells.