Highly attenuated poxvirus vectors: NYVAC, ALVAC and TROVAC.

Three highly attenuated and efficacious poxvirus-based vectors, NYVAC, ALVAC and TROVAC, are available for targeted applications as recombinant vaccines in both human and veterinary medicine. The attenuated phenotype of the three vectors is consistent with safe use for vaccination purposes, for the vaccinee, for unvaccinated contacts, and for introduction into the environment. The precise deletion of virulence and host range genes in the NYVAC vector precludes reversion to the virulent phenotype by back mutation. Dissemination of recombinant vaccines based on the NYVAC, ALVAC and TROVAC vectors is highly diminished, because of the genetic engineering in NYVAC and the natural attenuated phenotype of ALVAC and TROVAC. Studies have demonstrated that these recombinant vectors are genetically and phenotypically stable after serial passage in vitro as well as in vivo. NYVAC, ALVAC and TROVAC vectors are the only three poxvirus-based vectors that are classified as BSL1 agents.