[The protective properties in mice of tonate virus and two strains of cabassou virus against neurovirulent everglades Venezuelan encephalitis virus (author's transl)].

Venezuelan encephalitis virus is a constant menace to man and to animals, particularly horses. Two as yet unreported strains have been isolated in French Guyana: Ca An 410d (Tonate) and Ca Ar 508 (Cabassou). They are not neurovirulent after peripheral inoculation into adult mice and guinea pigs. Cabassou is not pathogenic for adult mice after intracerebral inoculation. A third strain, Ca Ar 19007, is antigenically identical by complement-fixation with Cabassou, but appears to cross react with other strains, Tonate, when injected intra-peritoneally or sub-cutaneously, protects adult mice against intra-cerebral or intra-peritoneal challenge with Everglades virus. The Ca Ar 19007 isolate causes total protection against Everglades virus if injected intra-peritoneally, but only partial protection by the sub-cutaneous route. Cabassou, on the other hand, if injected intra-peritoneally will protect against intra-cerebral challenge with Everglades. Tonate and Ca Ar 19007 thus appear to be naturally occurring attenuated variants of the Venezuelan encephalitis virus complex, which can protect mice against intra-cerebral infection with neurovirulent strains.