A deletion in the gI and gE genes of equine herpesvirus type 4 reduces viral virulence in the natural host and affects virus transmission during cell-to-cell spread

In order to identify the role of the equine herpesvirus type 4 (EHV-4) glyc oprotein I (gI) and E (gE) genes in determining viral virulence and their a ffect on the infection cycle, we constructed an EHV-4 recombinant strain co ntaining a deletion in both gI and gE genes and its revertant. The recombin ant was assayed in vitro in order to compare its growth kinetics with the p arent and revertant viruses. Our results indicated that a deletion in the g enes encoding gI and gE affected cell-to-cell spread of the virus in vitro. In order to assess the pathogenicity and vaccine efficacy of the recombina nt in a natural host, colostrum-deprived foals were inoculated intranasally with the recombinant. Clinical signs obtained in foals upon the inoculatio n with the recombinant were milder than that for the revertant. This sugges ts that intact gI and/or gE genes are important factors in the expression o f virulence in EHV-4 as in seen in the case of other herpesviruses. In addi tion, full protection against challenge infection was observed in foals, wh ich had undergone a previous inoculation of the recombinant. (C) 2000 Publi shed by Elsevier Science B.V. All rights reserved.