REACTIVATION OF LATENT BOVINE HERPESVIRUS-1 IN CATTLE SERONEGATIVE TOGLYCOPROTEINS GB AND GE

Six heifers were vaccinated intranasally with the live bovine herpesvi rus 1 (BHV1) temperature-sensitive (ts) vaccine strain RBL106 within 3 weeks of birth. These calves most likely still had maternal antibodie s against BHV1. Thereafter, these heifers were vaccinated several time s with an experimental BHV1 glycoprotein-D (gD) subunit vaccine. At th e age of 3 years these 6 heifers were seronegative in the BHV1 gB and gE blocking ELISAs, but had neutralizing antibodies against BHV1, prob ably induced by the vaccinations with the go subunit vaccine. Five of these 6 heifers excreted BHV1 after treatment with dexamethasone. Rest riction enzyme analysis of the genome of the excreted Viruses revealed that all 5 isolates had a BHV1.1 genotype and that isolates of 3 heif ers were not obviously different from the ts-vaccine strain. The restr iction enzyme fragment pattern of the isolate of I heifer was clearly different from the pattern of the ts-vaccine strain, it is concluded t hat cattle can be seronegative against BHV1 gB and gE but can still ca rry BHV1 in a latent form. This finding strongly suggests that there a re completely BHV1 seronegative cattle that are latently infected with BHV1. The impact of this finding on BHV1 eradication programmes is di scussed. (C) 1998 Elsevier Science B.V.