Immunization of BALB/c mice with DNA encoding equine herpesvirus 1 (EHV- 1) glycoprotein D affords partial protection in a model of EHV-1-induced abortion

DNA-mediated immunization was assessed in a murine model of equine herpesvirus 1 (EHV-1) abortion. Whilst there are differences between the model and natural infection in the horse, literature suggests that EHV-1 infection of pregnant mice can be used to assess the potential ability of vaccine candidates to protect against abortion. Female BALB/c mice were inoculated twice, 4 weeks apart, with an expression vector encoding EHV-1 glycoprotein D (gD DNA). They were mated 15 days after the second inoculation, challenged at day 15 of pregnancy and killed 3 days later. The gD DNA-inoculated mice had fewer foetuses which were damaged or had died in utero (6% in gD DNA, 21% vector DNA and 28% in nil inoculated groups challenged with EHV-1), a reduction in the stunting effect of EHV-1 infection on foetuses (gD DNA: 0.40 g ± 0.06, vector DNA: 0.34 g ± 0.10), reduced placental and herpesvirus-specific lung histopathology and a lower titre of virus (TCID₅₀ ± SEM/lung) in maternal lung than control groups (gD DNA 4.7 ± 0.3, vector 5.3 ± 0.2, nil 5.6 ± 0.2). Maternal antibody to EHV-1 gD was demonstrated in pups born to a dam inoculated 123 days earlier with gD DNA. Although protection from abortion was incomplete, immunization of mice with gD DNA demonstrated encouragingly the potential of this vaccine strategy. (C) 2000 Elsevier Science B.V.