The drug resistance mechanisms in Leishmania donovani are independent of immunosuppression.

The protozoan parasite L. donovani resides inside macrophages as amastigotes and inflicts a potentially lethal disease visceral leishmaniasis (VL). Due to absence of a vaccine, chemotherapy with antimonials, amphotericin B, miltefosine or paromomycin remains the only option for treating VL. Prolonged treatment with a single drug resulted in parasite strains resistant to each of these drugs. As immuno-suppression characterizes the disease, we examined whether eliciting immunosuppressive cytokines is a mechanism of manifestation of drug-resistance. We infected BALB/c mice with the clinical isolates of L. donovani- BHU1066 (sensitive), NS2 (antimony-resistant), BHU1064 (miltefosine-resistant), BHU919 (Amphotericin B-resistant) and BHU1020 (paromomycin-resistant)- from the respective drug-unresponsive patients and assessed splenic parasite load and production of pro-inflammatory and anti-inflammatory cytokines. Although the splenic parasite loads in the drug-resistant L. donovani-infected BALB/c mice were higher than that observed in the drug-sensitive parasites-infected mice, the cytokine profiles were not significantly different between these two sets of mice. The drug-resistance in L. donovani results from innate drug modulation but perhaps not from host immune-suppressive cytokines.