Response of calves to challenge exposure with virulent bovine respiratory syncytial virus following intranasal administration of vaccines formulated for parenteral administration.
OBJECTIVE
To determine whether single-fraction and combination modified-live bovine respiratory syncytial virus (BRSV) vaccines commercially licensed for parenteral administration could stimulate protective immunity in calves after intranasal administration.


METHODS
Randomized controlled trial.


METHODS
39 calves.


METHODS
Calves were separated from dams at birth, fed colostrum with a minimal concentration of antibodies against BRSV, and maintained in isolation. In 2 preliminary experiments, 9-week-old calves received 1 (n = 3) or 2 (3) doses of a single-component, modified-live BRSV vaccine or no vaccine (8 control calves in each experiment), and were challenged with BRSV 21 days after vaccination. In a third experiment, 2-week-old calves received combination modified-live virus (MLV) vaccines with or without BRSV and calves were challenged with BRSV 8 days later. Calves were euthanized, and lung lesions were measured. Immune responses, including serum and nasal antibody and nasal interferon-alpha concentrations, were assessed.


RESULTS
BRSV challenge induced signs of severe clinical respiratory tract disease, including death and pulmonary lesions in unvaccinated calves and in calves that received a combination viral vaccine without BRSV. Pulmonary lesions were significantly less severe in BRSV-challenged calves that received single or combination BRSV vaccines. The proportion of calves that shed virus and the peak virus titer was decreased, compared with control calves. Protection was associated with mucosal IgA antibody responses after challenge.


CONCLUSIONS
Single and combination BRSV vaccines administered intranasally provided clinical protection and sparing of pulmonary tissue similar to that detected in response to parenteral delivery of combination MLV and inactivated BRSV vaccines previously assessed in the same challenge model.
Ellis
John
J
Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.
Gow
Sheryl
S
West
Keith
K
Waldner
Cheryl
C
Rhodes
Carrie
C
Mutwiri
George
G
Rosenberg
Helene
H
D000281:Administration, Intranasal; D000818:Animals; D000831:Animals, Newborn; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000517:prevention & control*; D007263:Infusions, Parenteral / Q000662:veterinary; D008168:Lung / Q000473:pathology; D018357:Respiratory Syncytial Virus Infections / Q000517:prevention & control / Q000662:veterinary*; D022261:Respiratory Syncytial Virus Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D018112:Respiratory Syncytial Virus, Bovine / Q000276:immunology*; D013997:Time Factors; D016896:Treatment Outcome; D014613:Vaccines, Attenuated; D015164:Vaccines, Inactivated
D022261:Respiratory Syncytial Virus Vaccines; D014613:Vaccines, Attenuated; D015164:Vaccines, Inactivated