DISTRIBUTION OF EQUID HERPESVIRUS-1 (EHV-1) IN RESPIRATORY-TRACT ASSOCIATED LYMPHOID-TISSUE - IMPLICATIONS FOR CELLULAR-IMMUNITY

Twelve adult ponies and 2 conventional foals were exposed intranasally to EHV-1, strain Ab4 (TCID50 10(-6.6) and samples of respiratory trac t associated lymphoid tissues were recovered between 12 h and 13 days after infection. Infectious virus was detected in tissue homogenates u sing susceptible cell monolayers and expression of viral antigens was monitored using indirect immunoperoxidase histochemistry on paraffin s ections. The results showed both infectious EHV-1 and viral antigens i n respiratory tract associated lymph nodes 12 h after exposure. Infect ed leucocytes were identified morphologically as lymphocytes, monocyte s, macrophages and plasma cells. The rapid intracellular localisation of EHV-1 in lymph nodes implies that cell mediated immunity is an impo rtant aspect of the equine response to this virus.