Primary and challenge infection of mice with equine herpesvirus 1, strain HSV25A

Clinical signs, haematology, lymphocyte subset analysis, viral clearance, lung histopathology and humoral and cell-mediated (CMI) immune responses were monitored throughout the acute and convalescent phases of infection in groups of BALB/c mice infected intranasally with equine herpesvirus 1 (EHV-1), strain HSV25A. Primary infection caused a leucocytosis due to a neutrophilia during days 1 and 2 post-infection (pi) and a B lymphocytosis at day 1 pi. Serum ELISA antibodies were detected by 7 days pi and neutralising antibodies by 2 weeks pi. Mice infected with EHV-1 were not protected against disease when challenged with EHV-1 12 weeks later. However, viral clearance from lungs was significantly faster and the antibody response was markedly enhanced within the first few days of challenge infection. A CMI response was detected by 5 days after primary infection, but the level of responsiveness was not increased by challenge infection, although the lungs of challenged mice had markedly increased numbers of mononuclear cells around blood vessels and bronchioles. Specific antibodies to glycoprotein (g) B were detected by 2 weeks pi, 4 weeks earlier than the detection of antibodies to gC and 10 weeks before those to gD. The primary response was relatively short-lived with neither ELISA antibody nor lymphocyte proliferation was evident by 6 months pi.