Vaccinia Virus-Derived Vectors in Leishmaniases Vaccine Development

Due to an increase in the incidence of leishmaniases worldwide, the development of new strategies such as prophylactic vaccines to prevent infection and decrease the diseases has become a high priority. The development of vaccines against the various species of pathogenic Leishmania to humans has been hampered, in part, by the inefficient stimulation of the protective cellular immunity promoted by the administration of purified or recombinant antigens, indicating the need for new approaches. Viral vectors represent an attractive way to deliver and present vaccine antigens that may offer advantages over traditional platforms. Among the most attractive and efficient viral vectors in inducing a cellular immune response, vaccinia virus has been the most used in leishmaniases vaccine trials. The first report of the use of recombinant vaccinia virus (VACV) in the induction of protection against Leishmania infection was made in 1993. Since then, several Leishmania spp . antigenic subunits were cloned into recombinant VACV. Although highly attenuated poxviral vectors are capable of inducing protective immunity against Leishmania spp., their limitation in replicative capacity reduces their potential as compared to replicative vectors. In order to achieve a balance between safety and replication, several VACV strains with intermediate phenotype have been developed.