Infection of central nervous system endothelial cells by cell-associated EHV-1

Infection with equine herpesvirus-1 (EHV-1) causes respiratory disease, late-term abortions and equine herpesvirus myeloencephalitis (EHM). Our understanding of EHM pathogenesis is limited except for the knowledge that EHV-1 infected, circulating peripheral blood mononuclear cells (PBMC) transport virus to the central nervous system vasculature causing endothelial cell infection leading to development of EHM. Our objective was to develop a model of CNS endothelial cell infection using EHV-1 infected, autologous PBMC. PBMCs, carotid artery and brain endothelial cells (EC) from 14 horses were harvested and grown to confluency. PBMC or ConA-stimulated PBMCs (ConA-PBMCs) were infected with EHV-1, and sedimented directly onto EC monolayers ('contact'), or placed in inserts on a porous membrane above the EC monolayer ('no contact'). Cells were cultured in medium with or without EHV-1 virus neutralizing antibody. Viral infection of ECs was detected by cytopathic effect. Both brain and carotid artery ECs became infected when cultured with EHV-1 infected PBMCs or ConA-PBMCs, either in direct contact or no contact: infection was higher in carotid artery than in brain ECs, and when using ConA-PBMCs compared to PBMCs. Virus neutralizing antibody eliminated infection of ECs in the no contact model only. This was consistent with cell-to-cell spread of EHV-1 infection from leucocytes to ECs, demonstrating the importance of this mode of infection in the presence of antibody, and the utility of this model for study of cellular interactions in EHV-1 infection of ECs.