Efficacy of an inactivated respiratory syncytial virus vaccine in calves.
OBJECTIVE
To determine whether an inactivated bovine respiratory syncytial virus (BRSV) vaccine would protect calves from infection with virulent BRSV.


METHODS
Randomized controlled trial.


METHODS
27 nine-week-old calves seronegative for BRSV exposure.


METHODS
Group-1 calves (n = 9) were not vaccinated. Group-2 calves (n = 9) were vaccinated on days 0 and 21 with an inactivated BRSV vaccine containing a minimum immunizing dose of antigen. Group-3 calves (n = 9) were vaccinated on days 0 and 21 with an inactivated BRSV vaccine containing an amount of antigen similar to that in a commercial vaccine. All calves were challenged with virulent BRSV on day 42. Clinical signs and immune responses were monitored for 8 days after challenge. Calves were euthanatized on day 50, and lungs were examined for lesions.


RESULTS
Vaccination elicited increases in BRSV-specific IgG and virus neutralizing antibody titers and in production of interferon-gamma. Virus neutralizing antibody titers were consistently less than IgG titers. Challenge with BRSV resulted in severe respiratory tract disease and extensive pulmonary lesions in control calves, whereas vaccinated calves had less severe signs of clinical disease and less extensive pulmonary lesions. The percentage of vaccinated calves that shed virus in nasal secretions was significantly lower than the percentage of control calves that did, and peak viral titer was lower for vaccinated than for control calves.


CONCLUSIONS
Results suggest that the inactivated BRSV vaccine provided clinical protection from experimental infection with virulent virus and decreased the severity of pulmonary lesions. Efficacy was similar to that reported for modified-live BRSV vaccines.
Ellis
J
J
Department of Veterinary Microbiology, Western Collge of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
West
K
K
Konoby
C
C
Leard
T
T
Gallo
G
G
Conlon
J
J
Fitzgerald
N
N
D000818:Animals; D000831:Animals, Newborn; D000914:Antibodies, Viral / Q000097:blood; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000517:prevention & control*; D005260:Female; D007074:Immunoglobulin G / Q000097:blood; D007371:Interferon-gamma / Q000096:biosynthesis; D008168:Lung / Q000473:pathology; D018357:Respiratory Syncytial Virus Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D022261:Respiratory Syncytial Virus Vaccines / Q000008:administration & dosage / Q000276:immunology / Q000592:standards*; D018112:Respiratory Syncytial Virus, Bovine / Q000276:immunology*; D013997:Time Factors; D016896:Treatment Outcome; D015164:Vaccines, Inactivated; D017201:Virus Shedding
D000914:Antibodies, Viral; D007074:Immunoglobulin G; D022261:Respiratory Syncytial Virus Vaccines; D015164:Vaccines, Inactivated; D007371:Interferon-gamma