Immune response against Leishmania antigens in dogs naturally and experimentally infected with Leishmania infantum

Cell-mediated and humoral immune response in naturally and experimentally i nfected dogs was studied using crude and pure antigens. Both types of infec tions induced severe signs of visceral disease, but the symptoms observed i n natural infections were more pronounced than in experimental infections. In addition, asymptomatic infections were not observed in experimentally in fected animals. Disease evolution in laboratory infections was rapid and an increase in antibody titer to crude parasite antigen was correlated with t he appearance and aggravation of clinical symptoms. Peripheral blood lympho cyte proliferation to crude antigen and pure gp63 was observed early follow ing experimental infection, but was abolished once the infected dogs began to exhibit clinical signs. A similar pattern was observed in naturally infe cted dogs. Serum from all patent dogs showed high antibody titers to rK39 i n enzyme-linked immunosorbent assays (ELISA), and reacted by western blotti ng with several antigens, 12 to 120 KDa, including gp63 and gp70. In the ca se of asymptomatic dogs, antibody titers to crude antigen were low and only a few antigens were identified by western blotting. None of the pure prote ins examined, gp63, gp70, and rK39 were recognized by western blotting or E LISA. However, asymptomatic dogs exhibited specific lymphocyte proliferatio n to both crude antigen and the potential vaccine candidate gp63. (C) 1999 Elsevier Science B.V. All rights reserved.