Effective humoral and cellular immunoprotective responses in Li ESAp-MDP vaccinated protected dogs

Cell-mediated and humoral immunity were explored in LiESAp-MDP vaccinated protected dogs versus susceptible placebo dogs 2 months and 8 months post-vaccination. As previously described, a strong and long-lasting cell-mediated immunity, critical for protection against Leishmania infantum was exclusively revealed in vaccinated dogs as confirmed by a positive response to the intradermal inoculation of leishmanin and by a significant higher anti-leishmanial activity of canine monocytes-derived macrophages. Moreover, our results support the view that cooperation of humoral antibody with cell-mediated immunity might be important in developing protective immunity in LiESAp-MDP vaccinated dogs. Anti-LiESAp serum samples were found functionally active in vitro, promoting (i) early killing of pretreated promastigotes and amastigotes, (ii) strong inhibitory effect on the in vitro growth of both parasitic developmental stages of L. infantum and (iii) most importantly, a significant inhibition of pretreated promastigotes in vitro infectivity in canine macrophages. However, anti-LiESAp antibody response was not implicated in the promastigotes-amastigotes differentiation process. In these experiments, we have added additional support to the concept that antibodies to Leishmania may be important in developing protective immunity.