Experimental pathogenicity of a presumed monoxenous trypanosomatid isolated from humans in a murine model

Two strains of a presumed lower trypanosomatid isolated from immunocompeten t and HIV-infected humans in French West Indies were investigated in vitro and in vivo in a murine experimental model. The ability of parasites to gro w in vitro in bone marrow-derived macrophages and their virulence in vivo w ere assessed. For in vivo infection, two groups of BALB/c mice were inocula ted either by the subcutaneous or intravenous route with 10(7) promastigote s at day 0. Infection was monitored by measuring parasite load in liver, sp leen, foot pad, popliteal, and mesenteric lymph nodes and brain from day 7 to day 150 post-infection using a microtitration technique. Parasites multi plied in mouse macrophages in vitro. In vivo, both strains proved infective to mice and capable of visceralization and dissemination in the popliteal and mesenteric lymph nodes, liver, spleen, and even brain. Both strains eli cited a strong humoral response against trypanosomatid antigen in mice, whi ch cross-reacted with Leishmania antigen. Contrasting with the straightforw ard dissemination of parasites, the infection was strikingly well tolerated by the murine host with no clinical signs and minimal tissue changes aroun d parasitized macrophage infiltrates.