Replication of equine herpesvirus type 1 in freshly isolated equine peripheral blood mononuclear cells and changes in susceptibility following mitogen stimulation.

In the present study, the outcome of an inoculation of equine peripheral blood mononuclear cells (PBMC) with equine herpesvirus type 1 (EHV-1) was studied in vitro. Cytoplasmic and plasma membrane expression of viral antigens, intra- and extracellular virus titres, and plaque formation in co-culture were determined. EHV-1 replicated in monocytes, although in a highly restricted way. Viral antigens were found at maximum levels (8.7% of the monocytes) at 12 h post-infection. The infection was productive in 0.16% of the monocytes. The virus yield was 10(0.7) TCID(50) per productive cell. In a population of resting lymphocytes, 0.9% of cells were infected and less than 0.05% produced infectious virus. After prestimulation with different mitogens, the number of infected lymphocytes increased four to twelve times. The susceptible lymphocytes were T-lymphocytes. In mitogen-stimulated lymphocytes, clear expression of viral antigens was found on the plasma membrane.