SRA

The Leishmaniases are overwhelming neglected tropical diseases, caused by kinetoplastid protozoan parasites belonging to the genus Leishmania. In recent years, the polyene amphotericin B (AmB) has emerged as a treatment of choice against the leishmaniases. The drug acts by binding ergosterol in the parasite membrane, leading to cell lysis. Drug resistance and treatment failure in leishmaniasis has emerged. I have selected L. infantum lines for resistance to AmB. Sterol analysis pointed a loss of ergosterol and increase in 5,7, 24(28)-ergostatrienol. Genome sequence analysis revealed mutations in sterol C22 desaturase?which converts?5,7, 24(28)-ergostatrienol to ergostatetraenol. The mutation comprises a 21 base pair deletion corresponding to a 7 amino-acid hydrophobic patch at the periphery of the enzyme.?Over-expression of this mutant allele in WT parasites also yielded amphotericin B resistance while over-expression of the WT allele in the mutant cell line restored sensitivity. Moreover, the resistant parasites retained virulence in mice and the resistant line was not cleared by amphotericin B whereas WT were in treated mice. The data indicate that amphotericin B resistance in Leishmania infantum can come about through changes to the sterol pathway, as previously indicated in other amphotericin B resistance leishmania lines where mutations to different enzymes in the sterol pathway were noted. Interestingly, the L. infantum AmB resistant line described here is hypersensitise to nitric oxide inducing agents and also to pentamidine, as has been described for other AmB resistant lines, offering a potential route to treatment of resistant cases should their emergence become problematic in the field.?