SAFETY AND EFFICACY STUDIES OF LIVE-FELINE AND KILLED-FELINE LEUKEMIA-VIRUS VACCINES

  • 1 January 1979
    • journal article
    • research article
    • Vol. 40  (8) , 1120-1126
Abstract
The safety and the efficacy of several feline leukemia virus (FeLV) vaccines for 16 wk old kittens were determined. Vaccines were derived from an FL74 lymphoblastoid cell line that was in continuous tissue culture passage for about 4 yr. The vaccines were made from living virus, formaldehyde-inactivated whole FL74 cells and formaldehyde-inactivated whole virus. The efficacy of each produced vaccine was determined by challenge exposure of vaccinated cats with virulent FeLV. The 2 formaldehyde-inactivated vaccines were safe for use in kittens. Neither vaccine produce a significant feline oncornavirus-associated cell membrane antigen [Ag] or virus-neutralizing antibody response nor did they prevent infection with virulent FeLV. The inactivated whole-virus vaccine did substantially decrease the proportion of kittens infected with virulent FeLV that became persistently viremic. The whole FL74 cell vaccine did not reduce the number of infected kittens that became persistently viremic. The live virus vaccine was safe and efficacious. About a half of the kittens vaccinated with live virus had transient bone marrow infection that lasted from 2-4 wk. Viral Ag was not detected in peripheral blood and infective virus was not shed in saliva, urine or feces during the period that the vaccinal virus could be recovered from the bone marrow. There was not horizontal spread of vaccinal virus from vaccinated to non-vaccinated cagemates. Within several weeks, vaccinated kittens demonstrated no clinical or hematologic abnormalities and had high serum levels of feline oncornavirus-associated cell membrane Ag and virus-neutralizing antibody. Kittens vaccinated with living FeLV were resistant to infection with virulent virus.

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