Long-term immunity in cats vaccinated with an inactivated trivalent vaccine.

OBJECTIVE: To evaluate duration of immunity in cats vaccinated with an inactivated vaccine of feline panleukopenia virus (FPV), feline herpesvirus (FHV), and feline calicivirus (FCV). ANIMALS: 17 cats. PROCEDURE: Immunity of 9 vaccinated and 8 unvaccinated cats (of an original 15 vaccinated and 17 unvaccinated cats) was challenged 7.5 years after vaccination. Specific-pathogen-free (SPF) cats were vaccinated at 8 and 12 weeks old and housed in isolation facilities. Offspring of vaccinated cats served as unvaccinated contact control cats. Virus neutralization tests were used to determine antibody titers yearly. Clinical responses were recorded, and titers were determined weekly after viral challenge. RESULTS: Control cats remained free of antibodies against FPV, FHV, and FCV and did not have infection before viral challenge. Vaccinated cats had high FPV titers throughout the study and solid protection against virulent FPV 7.5 years after vaccination. Vaccinated cats were seropositive against FHV and FCV for 3 to 4 years after vaccination, with gradually declining titers. Vaccinated cats were protected partially against viral challenge with virulent FHV. Relative efficacy of the vaccine, on the basis of reduction of clinical signs of disease, was 52%. Results were similar after FCV challenge, with relative efficacy of 63%. Vaccination did not prevent local mild infection or shedding of FHV or FCV. CONCLUSIONS: Duration of immunity after vaccination with an inactivated, adjuvanted vaccine was > 7 years. Protection against FPV was better than for FHV and FCV. CLINICAL IMPLICATIONS: Persistence of antibody titers against all 3 viruses for > 3 years supports recommendations that cats may be revaccinated against FPV-FHV-FCV at 3-year intervals.

Levels of interferon in blood serum and toxicity studies of bacteria-derived bovine alpha I1 interferon in dairy calves.

This paper reports information on the levels of interferon (IFN) in the blood serum of dairy calves given 10(6) U of bacteria-derived bovine alpha I1 interferon per kg of body weight by intravenous (i.v.), intramuscular (i.m.), subcutaneous (s.c.), and intranasal (i.n.) routes. Highest levels (10,000 U/ml) in the vesicular stomatitis viral assay system were obtained after i.v. administration and occurred within 30 min of a dose; levels rapidly declined thereafter to a low of 200 to 300 U/ml by 24 h. Serum inhibitory activity against vesicular stomatitis virus in this range is sometimes found in normal dairy calves. Levels after i.m. and s.c. administration were similar: a plateau of 1,000 to 2,000 U/ml between 2 and 8 h after a treatment with a decline to 200 to 300 U/ml by 24 h. Serum IFN was not detected after i.n. dosing or in the control group given physiological buffered saline by the i.m. route. A transitory moderate febrile response, but no other clinical adverse effects, was noted after the first intramuscular dose of IFN, but not after subsequent i.m. doses. No clinical signs were noted after i.v., s.c., or i.n. dosing or in the control calves given physiological buffered saline intramuscularly. After i.v., s.c., and i.m. administration of IFN, leukopenia, neutropenia, and lymphocytopenia were observed; these were most prominent within the first 24 h after the initial dose of IFN.