STUDY OF HOMOLOGOUS AND HETEROLOGOUS ANTIBODY-RESPONSES IN CALIFORNIA HORSES VACCINATED WITH ATTENUATED VENEZUELAN EQUINE ENCEPHALOMYELITIS VACCINE (STRAIN TC-83)

  • 1 January 1978
    • journal article
    • research article
    • Vol. 39  (3) , 371-376
Abstract
Of 359 horses vaccinated with attenuated Venezuelan equine encephalomyelitis (VEE) vaccine (strain TC-83), 87% developed hemagglutination-inhibition (HI) antibodies to VEE virus within 1 mo. Blood from a subsample of 101 of the 359 horses was obtained over a 1 yr period. Within 1 mo. after vaccination, 84% of the 101 horses developed VEE-HI antibodies, 87% developed VEE-neutralizing (Nt) antibodies and 78% developed VEE complement-fixing (CF) antibodies. One year after vaccination, 58% of the horses had VEE HI antibodies and 73% had VEE Nt antibodies. The percentage of horses with VEE CF antibody titers dropped to a low level (46%) within 6 mo. after vaccination, and most horses were seronegative for VEE CF antibodies 1 yr after vaccination. The presence of antibodies to heterologous (western equine or eastern equine encephalomyelitis, or both) alphaviruses suppressed VEE antibody formation in horses vaccinated with TC-83 vaccine. The proportion of horses that developed VEE antibodies exceeded levels that generally were believed adequate to suppress a VEE epizootic in a population. There was an 88% correlation between the HI and Nt tests for VEE antibodies.