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 bl ood mononuclear cells (PBMC) with equine herpesvirus type 1 (EHV-1) was stu died 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 restr icted way. Viral antigens were found at maximum levels (8.7 % of the monocy tes) at 12 h post-infection. The infection was productive in 0.16% of the m onocytes. The virus yield was 10(0.7) TCID50 per productive cell. In a popu lation 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 su sceptible lymphocytes were T-lymphocytes. In mitogen-stimulated lymphocytes , clear expression of viral antigens was found on the plasma membrane.