Objective—To compare protection against FeLV challenge obtained following administration of 2 doses of an adjuvanted, chemically inactivated, whole FeLV (FeLV-k) vaccine with protection obtained following administration of 1 dose of an FeLV-k vaccine followed by 1 dose of a canarypox virus–vectored recombinant FeLV (rCP-FeLV) vaccine.
Procedure—Cats received 2 doses of the FeLV-k vaccine SC, 21 days apart (n = 11); 1 dose of the FeLV-k vaccine SC and, 21 days later, 1 dose of the rCP-FeLV vaccine transdermally (11); or 2 doses of physiologic saline (0.9% NaCl) solution (control; 10). Four weeks after the second vaccine dose, all cats were challenged with FeLV by means of oronasal administration. Blood samples were collected at weekly intervals beginning 21 days after challenge, and serum was tested for FeLV antigen.
Results—All 10 control cats became persistently infected (ie, FeLV antigen detected in ≥ 3 consecutive serum samples) following FeLV challenge, whereas only 1 of 11 cats that received 2 doses of the FeLV-k vaccine and none of the 11 cats that received 1 dose of the FeLV-k vaccine and 1 dose of the rCP-FeLV vaccine did.
Conclusions and Clinical Relevance—Results suggest that protection against FeLV challenge obtained following SC administration of a single dose of an FeLV-k vaccine followed, 21 days later, by transdermal administration of a single dose of an rCP-FeLV vaccine was similar to that obtained following SC administration of 2 doses of the FeLV-k vaccine 21 days apart.
Objective—To determine whether an inactivated
bovine respiratory syncytial virus (BRSV) vaccine
would protect calves from infection with virulent
Design—Randomized controlled trial.
Animals—27 nine-week-old calves seronegative for
Procedure—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-γ. 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
Conclusions and Clinical Relevance—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. (J Am Vet Med Assoc 2001;218:1973–1980)