Study of parasite kinetics with antileishmanial drugs using real-time quantitative PCR in Indian visceral leishmaniasis.

OBJECTIVES This study describes parasite kinetics in the blood of visceral leishmaniasis patients treated with liposomal amphotericin B (L-AmB) or a preformed fat emulsion of amphotericin B (ApL) using real-time quantitative PCR (qPCR). METHODS Forty-six patients were treated with a single dose (15 mg/kg of body weight) of either L-AmB (n = 13) or ApL (n = 33). qPCR was used to estimate parasite kinetics by detection of Leishmania donovani DNA using kinetoplast DNA-specific primers in peripheral blood samples using an absolute quantification method. RESULTS The mean parasite load decreased from baseline (day 0) values of 894.07 and 980.48 to 71.72 and 211.52 parasite genomes/mL at day 7 in L-AmB and ApL groups, respectively, and at day 30 these further declined to 8.30 and 133.98 parasite genomes/mL, respectively. At day 30 post-treatment evaluation, the decline in parasite load was significantly greater (P = 0.024) with L-AmB compared with ApL. Four of 33 patients in the ApL group failed treatment (1 primary failure and 3 relapses) with the presence of parasites, whereas all patients in the L-AmB group were cured at 6 month follow-up. CONCLUSIONS qPCR can be a tool to measure parasite dynamics accurately and provide a marker to measure the efficacy of various drugs. It can be used as a test of cure, allowing us to do away with invasive and risky methods such as splenic or bone marrow aspiration.