title: Possible evidence for interference with Venezuelan equine encephalitis virus vaccination of equines by pre-existing antibody to Eastern or Western Equine encephalitis virus, or both.
abstract: During 1971, an epizootic of Venezuelan equine encephalitis (VEE) reached the United States. Laboratory tests were performed on a large number of sick, healthy, unvaccinated, and vaccinated horses. Neutralization (N) tests in cell cultures revealed that 153 of 193 (79.3%) equines outside the state of Texas and 175 of 204 (85.8%) within Texas (82.6% overall) had detectable N antibody to VEE virus a week or more after vaccination. Twenty-six of 40 (65%) non-Texas equines and 18 of 29 (62%) Texas equines which had no detectable antibody against VEE virus a week or more after vaccination had N antibody against Eastern equine encephalitis (EEE) or Western equine encephalitis (WEE) virus or both, whereas only 50 of 153 (32.7%) non-Texas equines and 82 of 175 (46.9%) Texas equines with demonstrable N antibody against VEE also had N antibody against EEE and/or WEE virus. In vaccinated equines, significant negative correlations were found between the occurrence of antibody to VEE and antibody to EEE and/or WEE virus. These findings support the hypothesis that pre-existing antibody to EEE and/or WEE virus may modify or interfere with infection by VEE virus. The epizoologic significance of this possibility is discussed briefly.
mesh_terms: D000818:Animals; D000914:Antibodies, Viral; D003429:Cross Reactions; D004666:Encephalitis Virus, Venezuelan Equine / Q000276:immunology*; D004667:Encephalitis Virus, Western Equine / Q000276:immunology*; D004668:Encephalitis Viruses / Q000276:immunology*; D005189:False Positive Reactions; D006385:Hemagglutination Inhibition Tests; D006736:Horses / Q000276:immunology; D009500:Neutralization Tests; D013223:Statistics as Topic; D013781:Texas; D013997:Time Factors; D014611:Vaccination
chemical_list: D000914:Antibodies, Viral