Central nervous system involvement in experimental infection with Leishmania (Leishmania) amazonensis

We describe the pathologic alterations of the central nervous system (CNS) observed in experimental tegumentary leishmaniasis in BALB/c and Swiss mice. The mice were subcutaneously infected with 10(4) amastigotes of Leishmania (Leishmania) amazonensis. Animals were killed and brains were removed for histologic and immunocytochemical studies. Histologic examination showed that 66.6% of infected mice had a discrete hyperemia and inflammatory infiltrate in the meninges, composed of mononuclear cells and neutrophils with no detectable parasites. However, parasitized macrophages were detected in the cerebral parenchyma, as well as mast cells, lymphocytes, and polymorphonuclear cells. Necrosis in the cerebral parenchyma was also observed. Confocal fluorescence microscopy showed that CD8(+) T lymphocytes are the major component of the inflammatory infiltrate in the CNS. In addition to these cells, CD4(+), CD11b, and dendritic cells are present, in small numbers, in the inflammatory processes of the CNS. Thus, L. amazonensis is able to cross the blood-brain barrier and cause significant pathologic changes in the CNS.