Leishmanicidal activity of stearylamine-bearing liposomes in vitro

Liposomes consisting of stearylamine (SA) and egg yolk phosphatidylcholine (PC) were studied for their cytotoxic activity against freshly transformed promastigotes and intracellular amastigotes of Leishmania donovani, the cau sative agent of visceral leishmaniasis. More than 99% of the parasites of s train AG83 were killed within 60 min by treatment with 22 mol% SA-PC liposo mes (132 mug/ml total lipids). This was further confirmed by incubating the liposome-treated promastigotes at 22 C for 96 hr. The killing activity of the liposomes progressively decreased with lowering lipid concentration. Ho wever, weak cytotoxic activity was still detected at 6.6 mug/ml lipids. Lei shmanicidal activity of the liposomes became stronger with increasing SA co ntent but was reduced with the incorporation of cholesterol in the liposome s. A similar cytotoxic effect was observed on other Indian strains of L. do novani, for example PKDL and DD8, as well as on species such as Leishmania donovani S1, Leishmania donovani infantum, Leishmania tropica, Leishmania a mazonensis, and Leishmania mexicana. However, freshly transformed promastig otes appeared to be more susceptible than the ones subcultures. The strong leishmanicidal activity of SA-PC liposomes was also demonstrated toward int racellular L. donovani amastigotes. The SA-bearing vesicles could effective ly inhibit the growth and multiplication of the parasites within the macrop hages. The cytolytic activity of these liposomes on leishmanial parasites a nd low toxicity on host macrophages may, thus, find application in the ther apy of leishmaniasis.