Effect of temperature on multiplication of Leishmania amastigotes within human monocyte-derived macrophages in vitro.

Leishmania tropica, a cause of cutaneous leishmaniasis, multiplied more rapidly within human macrophages in vitro at 35 degrees C than at 37 degree C, and was almost completely eliminated at 39 degrees C. In contrast, Leishmania donovani, the cause of the visceral leishmaniasis, multiplied equally well at 35 degrees C and at 37 degrees C,, and was only 40% eliminated at 39 degrees C. This in vitro study suggests that the localization of the two strains to cooler and warmer regions of the body, respectively, is at least partially explained by the inherent temperature sensitivity of the parasite-macrophage unit. The striking elimination of this strain of L. tropica within macrophages at 39 degrees C may make this model suitable for predicting the clinical response of cutaneous strains to heat therapy.