In vitro binding and survival assays of Leishmania parasites to peripherical blood monocytes and monocyte-derived macrophages isolated from dogs naturally and experimentally infected with Leishmania (Leishmania) chagasi

In the presence of exogenous serum, opsonized Leishmania promastigotes binds better to monocytes/macrophages than without serum. Otherwise, this binding occurs due to the strict correlation between the opsonized biologic particles with the third receptor of the complement (CR3-CD11b/CD18). In fact, our assays with CD11b confirmed the importance of this receptor for canine cells and the L. chagasi experimental system. Moreover, monocytes obtained from naturally infected dogs have shown a higher number of monocytes bounded to promastigotes. The experimental results regarding survival have shown that promastigote forms of opsonized L. chagasi were more infective, because we found higher numbers of promastigotes bound to the different cells. As a consequence, after forty-eight hours of binding, higher numbers of amastigotes appeared inside monocyte-macrophages.These studies have given support to continue comparative studies involving canine monocytes, monocyte-derived macrophages and peritoneal macrophages. Since we have standardized the canine cell culture, we are looking forward to determining the phenotypic properties of these cells before and after L. chagasi infection using flow cytometry.Canine visceral leishmaniasis (CVL) is caused by Leishmania infantum (syn. L. chagasi in America) [1]. This protozoan is transmitted by the bite of the female phlebotomine sand fly of the species Lutzomyia longipalpis (in America) [2]. Protozoa of the genus Leishmania are dimorphic obligate intracellular parasites that reside within mononuclear phagocytes in the mammalian host. In America, dogs infected with L. chagasi constitute the main domestic reservoir of the parasite and play an important role in transmission to humans, in which the parasite causes the visceral disease, characterizing it as a zoonosis.The immune response against Leishmania is highly dependent upon macrophages. Although these are the host cells targeted for infection, they are competent to present antigen and