Experimental infection of bulls with a genital isolate of bovine herpesvirus-4 and reactivation of latent virus with dexamethasone.
Five 13- to 18-month old Belgian Blue bulls were used in this experiment. Four bulls (Nos. 2, 3, 4 and 5) were inoculated intratesticularly with 10(5) plaque-forming units of bovine herpesvirus-4 (BHV-4) in each testicle (Day 0). The challenge BHV-4 strain was previously isolated from testicle cells of a bull exhibiting orchitis and azoospermia. The fifth bull (No. 1) was used as a control and received the same volume of uninfected cell culture supernatant. For 5 days, beginning on Day 51 post-infection, two bulls (Nos. 4 and 5) and the control bull (No. 1) received 0.1 mg kg-1 of dexamethasone. Unilateral castrations were then performed at regular intervals for viral examination. Treatment with dexamethasone reactivated latent BHV-4, but no clinical signs were observed in treated bulls until the end of the experiment (Day 93). Only Bull 3 showed conjunctivitis and temporary azoospermia. The virus was recovered from various samples showing that: (i) BHV-4 can be present in a latent state in the testicles and mononuclear blood cells; (ii) dexamethasone reactivates the virus; (iii) the virus is excreted by nasal and ocular routes. Each infected bull seroconverted and a booster antibody response appeared after dexamethasone treatment as shown by immunofluorescence. Neutralizing antibodies were detected in each bull by complement-dependent neutralization test with titres higher than those obtained by a classical neutralization test. No booster response of neutralizing antibodies was observed after dexamethasone treatment. The antigenically relevant envelope BHV-4 proteins were identified by Western blotting using sera samples from the animals. DNA restriction endonuclease profiles of viruses reisolated after primary infection and reactivation showed only small differences.
Dubuisson
J
J
Department of Virology-Immunology, Institut de Chimie, Liège, Belgium.
Thiry
E
E
Bublot
M
M
Thomas
I
I
van Bressem
M F
MF
Coignoul
F
F
Pastoret
P P
PP
D000818:Animals; D000914:Antibodies, Viral / Q000032:analysis; D015139:Blotting, Southern; D015153:Blotting, Western; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D003231:Conjunctivitis / Q000382:microbiology / Q000662:veterinary; D004279:DNA, Viral / Q000032:analysis; D003907:Dexamethasone / Q000494:pharmacology*; D005455:Fluorescent Antibody Technique; D006564:Herpesviridae / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D006566:Herpesviridae Infections / Q000382:microbiology / Q000662:veterinary*; D008297:Male; D009920:Orchitis / Q000382:microbiology / Q000662:veterinary; D012008:Recurrence; D015183:Restriction Mapping; D013737:Testis / Q000382:microbiology* / Q000473:pathology; D014759:Viral Envelope Proteins / Q000032:analysis
D000914:Antibodies, Viral; D004279:DNA, Viral; D014759:Viral Envelope Proteins; D003907:Dexamethasone