METHOD VALIDATION OF TWO In Vitro ASSAYS FOR VENEZUELAN EQUINE ENCEPHALITIS IN COMPLIANCE WITH FDA GUIDELINES AND REGULATIONS

Abstract

Venezuelan equine encephalitis virus (VEE) was first identified in 1936 during an equine encephalitis outbreak in Venezuela. Since the initial isolation of VEE, several major epizootics of the disease have occurred in Colombia, Peru, Venezuela, Ecuador, and Trinidad. In the 1943-1944 Trinidad VEE epizootic, several donkeys with signs of encephalitis were sacrificed and virus was isolated from these brain homogenates. The isolated virus was used to generate a live-attenuated vaccine by serial propagation in guinea pig heart cells called VEE (TC-83 strain) virus vaccine, which is still in use today under Investigation New Drug (IND) status. The TC-83 vaccine causes systemic reactions in 23% of vaccine recipients and another 18% do not respond to TC-83 vaccine as a primary immunogen (Pittman, et al., 1996). A second vaccine against VEE, C-84 vaccine, was produced by formalin-inactivation of a second passage in chick embryo cells of the seed production lot of VEE from the TC-83 vaccine. C-84 vaccine is still in use today, also under IND status, as a booster immunization for persons with waning neutralizing antibodies to VEE and for TC-83 vaccine non-responders. A new vaccine candidate, VEE vaccine V3526, has been produced by site-directed mutagenesis of a full- length VEE cDNA clone with a deletion mutation and a second site substitution by another research group. An IND application for the new vaccine candidate will be submitted to the Food and Drug Administration (FDA).