Characterisation of IE and UL5 gene products of equine herpesvirus 1 using DNA inoculation of mice

Summary.  The equine herpesvirus 1 (EHV-1) strain HVS25A regulatory genes IE and UL5, encoding homologues of herpes simplex virus 1 (HSV-1) ICP4 and ICP27 respectively, were cloned into a eukaryotic expression vector and the DNA injected intramuscularly into mice. Antibodies produced in this way detected the IE or UL5 gene products as diffuse material in nuclei of RK13 cells transfected with the individual genes but as discrete punctate or large aggregates in RK13 cells infected with EHV-1. Western blotting on EHV-1 infected RK13 cells showed multiple IE products of 120–200 kDa and a UL5 product of 52 kDa. Inoculation with plasmids expressing EHV-1 IE or UL5 provided limited protection against EHV-1 challenge in mice as determined by increased virus clearance from lungs on day 2 post-challenge and a reduction in severity of lung histopathology. However, this protection was relatively weak compared with that provided by inoculation of DNA encoding EHV-1 glycoprotein D (gD), possibly reflecting the importance of neutralising antibody in this model. Accepted May 19, 2000 Received March 20, 2000