Calves exposed to a bovine respiratory syncytial virus showed mild clinical signs of respiratory illness and responded serologically. The disease occurred in the presence or absence of circulating antibodies, but there was no evidence of exacerbation of the disease due to preexisting serum antibody. Nasal secretory antibody appeared to protect the calves against the disease. Calves previously exposed to the virus were immune to challenge. The virus was recovered at a high frequency when specimens of nasal secretion (not subjected to freezing and thawing) were inoculated into susceptible cells within 1 hr after collection.
A number of herpesviruses have been isolated from cattle. Members of the bovine herpesvirus group are infectious bovine rhinotraeheitis (IBR), infectious bovine keratoconjunetivitis (IBKC), bovine mammilitis (BM), Allerton and malignant catarrhal fever (MCF) viruses. Recently, IBKC virus has been shown to be the same as IBR virus (3). BA~A et al.(1) isolated a bovine herpesvirus (Movar 33/63) which was reportedly different from IBR, pseudorabies (PR) and MCF viruses, but non-pathogenic to calves. This report describes the isolation of a new bovine herpesvirus and its effect on experimentally infected calves.The bovine herpesvirus designated DIq-599 was isolated from a 1 89 steer with cliniea] symptoms of respiratory disease, l~asal swabs were collected and inoculated into primary bovine embryonic kidney (BEK) cell cultures. The maintenance medium contained Eagle's basal medium with Earle's salts, 2~o fetal calf serum (free of adventitious viral agents) and the usual concentration of antibiotics. Primary isolation of DIq-599 bovine herpesvirus was made after a 9-day incubation at 37 o C, when characteristic cy~opathie effects were evident.The isolate was inhibited in the presence of 5-fluorodeoxyuridine, was acid labile, heat sensitive, and chloroform sensitive. The virions had characteristic herpesvirus structure in negatively stained electron microscopic preparation and measured 150 m~z and 110 m~z with and without envelope, respectively. The virus produced numerous type A intranuclear inclusion bodies 48 hours after infection in BEK cells.A pilot experiment in 7-week-old calves was conducted to study the pathogenicity of the agent. Two calves (caLf 1, female, and calf 2, male) were infected with the virus. Another bull calf (calf 3), was a control. The inoculum had a titer of 104.5 TCIDs0/ml. Each calf received 5 ml of virus suspension intranasally and
Ten virus-specific polypeptides ranging in molecular weight from approximately 200k to 11k were identified in bovine respiratory syncytial virus (BRSV-)infected cells. Time course analysis of the induction of the viral polypeptides indicated that they could be detected as early as 30 min post-infection and their synthesis reached a plateau 12 h after infection. Cell free translation of total infected-cell mRNA in a rabbit reticulocyte system yielded 7 proteins corresponding in size to virus-specific proteins synthesized in BRSV-infected cells. The P protein was highly phosphorylated; G and F were identified as glycoproteins by [3H]glucosamine labeling. Glycosylation of G protein was largely resistant to tunicamycin, suggesting that the majority of the carbohydrate residues are attached via O-glycosidic bonds, whereas the F protein was N-linked glycosylated. Tunicamycin caused a drastic reduction in the yield of infectious virus titer indicating that the carbohydrate moieties serve a critical role in the infectious cycle of BRSV.
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