Inhibition of intracellular proliferation of Leishmania parasites in vitro and suppression of skin lesion development in BALB/c mice by a novel lipid A analog (ONO-4007).

A synthetic lipid A analog (ONO-4007) exhibits antileishmanial activity by activating Leishmania-infected macrophages in experimental leishmaniasis. In the present in vitro study, ONO-4007 at concentrations between 0.01 and 1.00 mg/mL markedly inhibited the proliferation of Leishmania major and L. amazonensis promastigotes. Ultrastructurally, L. major-infected macrophages showed degenerated intracellular amastigotes after exposure to ONO-4007. Leishmania-infected macrophages treated with ONO-4007 showed poorly developed parasitophorous vacuoles. High levels of tumor necrosis factor-alpha were induced by ONO-4007 in Leishmania-infected macrophages. In this in vivo study, L. amazonensis-infected BALB/c mice were treated with a dose of 30 mg/kg of ONO-4007 by perilesional and peritoneal injections. The skin lesion size was assessed before treatment with ONO-4007 and at eight weeks after injection. The lesion size was significantly suppressed in mice perilesionally injected with ONO-4007 (P < 0.01) compared with the controls. The data from our present in vitro and in vivo studies indicate that ONO-4007 has an antileishmanial effect.