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in Journal of the American Veterinary Medical Association

Summary

Immunoaffinity-purified bovine respiratory syncytial virus (brsv) fusion (F) protein elicited anti-brsv-specific antibody responses in brsv-seronegative calves. After primary vaccination, all calves seroconverted to brsv as determined by the virus neutralization (vn) test and developed anti-F protein antibodies detectable by protein immunoblot analyses. Subsequent vaccinations induced > twofold increase in vn titer in 3 of 9 (33%) calves, and 1 calf became vn-negative, but still had nonneutralizing antibody detectable by protein immunoblot analysis. This calf remained seronegative after challenge exposure.

Two groups of calves were vaccinated im with immunoaffinity-purified brsv F protein. Each dose was 2 ml containing 20 μg of purified F protein. Freund's adjuvants were used for all vaccinations, with Freund's complete adjuvant used for the primary vaccination and Freund's incomplete adjuvant for subsequent vaccinations. The vaccine was administered to both groups at weeks 0 and 3; the first group received a third vaccination at week 21. Group-1 and -2 vaccinated calves and non-vaccinated contact controls were intranasally aerosol challenge-exposed with low cell culture-passage brsv on weeks 22 and 9, respectively.

Eight of 9 vaccinated calves did not develop a humoral anamnestic response following challenge exposure, as demonstrated by vn test and protein immunoblot analyses. Calf 14 from group 1 which had a 1:2 vn antibody titer prior to vaccination, was the only calf that developed an anamnestic response. This suggests that vaccine-induced antibodies interfered with the immune response or that the challenge virus (and the virus that calf 14 was infected with before challenge exposure) contained different F protein epitopes, compared with the purified F protein immunogen.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To test the hypothesis that feedlot cattle with acute interstitial pneumonia (AIP) have bacterial infection of the lung or liver and concurrent bovine respiratory syncytial virus (BRSV) infection significantly more often than pen mates without AIP.

Animals—39 feedlot cattle with signs consistent with AIP and no history of treatment with antimicrobials and 32 healthy control cattle from the same pens.

Procedure—Lung and liver specimens were obtained postmortem for bacterial or mycoplasmal culture and histologic examination; lung tissue was assessed for BRSV infection immunohistochemically.

Results—Among affected cattle, 26 had AIP confirmed histologically. Lung tissue from 11 cattle with AIP yielded microbial respiratory tract pathogens on culture; tissues from control animals yielded no microbial growth. In 4 cattle with AIP and 2 control animals, liver abscesses were detected; bacteria were isolated from abscessed tissue in 3 and 1 of those animals, respectively. Immunohistochemically, 9 cattle with AIP and no control animals were BRSV-positive. Histologically, 9 AIP-affected cattle had only acute alveolar damage with exudation, and the other 17 had acute exudation with type II pneumocyte hyperplasia. No lesions of AIP were detected in control animals. Only 4 AIP-affected cattle had bacterial infection of the lung with concurrent BRSV infection.

Conclusions and Clinical Relevance—Results indicated that microbial respiratory tract pathogens are more common in cattle with AIP than in healthy pen mates. Control of bacterial pneumonia late in the feeding period may reduce the incidence of AIP at feedlots where AIP is a problem. (Am J Vet Res 2004;65:1525–1532)

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in American Journal of Veterinary Research