Latency and reactivation of a glycoprotein E negative bovine herpesvirus type 1 vaccine: influence of virus load and effect of specific maternal antibodies

The effects of the vaccination of neonatal calves with a glycoprotein E (gE )-negative bovine herpesvirus type 1 (BHV-1) were investigated in naive and passively immunised calves either with the recommended dose or a 5-fold co ncentrated one. After inoculation (PI), all calves excreted the virus vacci ne except three passively immunised calves inoculated with the lower titre. No antibody response could be detected in passively immunised calves, what ever the dose used, and they all became BHV-1 seronegative and remained so after dexamethasone treatment (PDT). Nevertheless, as shown by a gamma-inte rferon assay, all calves that excreted the vaccine PI developed a cell-medi ated immune response and a booster response was observed PDT, suggesting vi ral reactivation. The vaccine virus was recovered PDT from nasal secretions in two calves and BHV-1 DNA were detected in trigeminal ganglia from five calves belonging to all inoculated groups. The results show that the BHV-1 gE-negative vaccine can establish latency not only in naive but also in pas sively immunised neonatal calves after a single intranasal inoculation. Mor eover, this study shows for the first time that the gE-negative vaccine, wh en used in passively immunised calves, can lead to seronegative vaccine vir us carriers. (C) 2001 Elsevier Science Ltd. All rights reserved.