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| ABSTRACT |
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| INTRODUCTION |
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Miltefosine is an alkylphosphocholine, initially developed as an anticancer agent, that also shows selective activity against Leishmania.2 Miltefosine has undergone successful clinical trials for anthroponotic VL in Bihar state, India, with 94% cure rate, including antimony-resistant cases,3 and is currently in Phase IV trials in India and Nepal. This oral drug has demonstrated some activity in the treatment of zoonotic CL in South America4,5 where it is currently in Phase III clinical trials.6 There are more than 17 species of Leishmania that cause leishmaniasis in human populations; these species have been shown to vary in sensitivity to a range of anti-leishmanial drugs7 including miltefosine.8 The current study is the first to evaluate the in vitro anti-leishmanial activity of miltefosine against recently isolated, typed Leishmania spp. from patients in the Old and New Worlds.
| MATERIALS AND METHODS |
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Cutaneous leishmaniasis patients were recruited at the Instituto Alexander von Humbolt, Lima, Peru, with geographical location noted in the patient data (Table 1
). Pregnant women were excluded from the study. Patients presenting with an ulcerated or nodular lesion were considered. Infection by Leishmania was confirmed by direct examination of punch biopsy material with confirmation by parasite culture or PCR. Patients received 20 mg SbV kg1 day1 intravenously for 20 days, except for PER069 who received treatment of 30 days. Unresponsive patients received a repeat course of antimonials. If this was again unsuccessful, patients received intravenous amphotericin B (amphotericin B deoxycholate).
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Late stage promastigotes were used to infect primary isolated mouse peritoneal macrophages at a ratio of 7 promastigotes to 1 macrophage in Labtek 16-well tissue culture well slides (VWR Ltd, Poole, UK), in quadruplicate. Infected cultures were maintained in RPMI 1640 medium (Sigma, Gillingham, UK) with 10% heat-inactivated fetal calf serum (Harlan SeraLab, Loughborough, UK) at 37°C (VL strains) or 34° C (CL strains) in a 5% CO2/95% air mixture. Twenty-four hours after infection, one slide was methanol-fixed and Giemsa-stained to determine the initial level of infection. Cultures were then exposed to miltefosine (hexadecylphosphocholine, HPC; A G Scientific, San Diego, CA) over a dose range of 30, 10, 3, and 1 µg/mL, in quadruplicate at each concentration. Higher concentrations were not tested due toxicity to macrophage host cells: at concentrations above 30 µg/mL, macrophages infected are destroyed and the slide cannot be evaluated. After 5 days, all slides were methanol-fixed and Giemsa-stained. The percent of infected macrophages in each well was determined by microscopy. From a comparison of counts from treated with untreated cultures, the percent inhibition was calculated by sigmoidal regression analysis (MS xlfit) and ED50 (ED90) values determined. Leishmania (V.) braziliensis MHOM/BR/75/M2903 was the reference strain used for Peruvian isolates. L. (L.) donovani MHOM/ET/67/HU3 was used as the reference strains for Nepalese isolates. Both strains are known as WHO reference strains, as typed by isoenzyme analysis, and are sensitive to the standard antimonials, sodium stibogluconate and meglumine antimoniate.
Leishmania species typing. In Antwerp, Leishmania species typing was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of cysteine proteinase b (cpb) and gp63 genes for Nepalese strains and by multi-locus PCR-RFLP for Peruvian strains. Briefly, DNA was extracted from cultivated promastigotes with the QIAmp DNA mini Kit (Qiagen, Hilden, Germany), amplified and digested as reported elsewhere.1214 Restriction patterns were resolved by capillary electrophoresis (2100 Bioanalyzer system, Agilent Technologies, Karlsruhe, Germany) in a micro-chip device (LabChip 1500, Caliper Technologies, Mountain View, CA) and compared with those of reference strains. Standard strains were also re-typed and confirmed to be L. (L.) donovani and L. (V.) braziliensis.
| RESULTS |
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The activity of miltefosine against VL isolates from Nepal is shown in Table 2
with ED50 values ranging from less than 0.04 µg/mL to 8 µg/mL. Results were similar in repeated experiments. Although the strains were identified as two L. (L.) donovani types (I and II, based on restriction pattern differences),12,14,15 there was no significant difference in sensitivity to miltefosine between them. The differences seen in the RFLP pattern are useful when tracing the genetic relationships among the strains. L. (L.) donovani HU3 is an Ethiopian strain of VL maintained in passage animals. An Indian reference strain would perhaps have been a more appropriate comparator but was not available to us at the time of this study.
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| DISCUSSION |
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As with in vitro sensitivity to antimonials and other anti-leishmanial drugs, there appears to be intrinsic variation in species sensitivity to miltefosine. If this is reflected in vivo this has important implications for the evaluation of clinical trials of the drug in Latin America. A dosing regimen of miltefosine at 2.5 mg kg1 day1 (150 mg of drug) for 28 days was required to have a significant effect against Colombian L. (V.) panamensis but was not as effective against Guatemalan L. (V.) braziliensis.5 It should be noted that the species were identified by historical data in these studies. The evidence suggests that miltefosine may be a useful drug for the treatment of South American CL, however, species identification should perhaps be a priority before treatment to give the best chance of efficacy and to reduce the possibility of either encouraging resistance to develop, a potential problem when considering anthroponotic transmission, or by re-enforcing intrinsic drug insensitivity, as may be the case in zoonotic foci. Resistance mechanisms to miltefosine been identified in laboratory-induced Leishmania.16,17 It would be interesting to see if these were present in unresponsive "wild-type" parasites.
The utility of the in vitro test when assessing isolate drug sensitivity could be improved by testing parasites pre- and post-treatment, but, to date, the number of samples where this is possible is not significant. Finally, the relevance of in vitro data to clinical outcome must also be considered as the two parameters may not necessarily correlateconfounding factors such as host immunity are absent from these tests.18 The data serve to emphasize the extremely complex clinical picture of leishmaniasis.
Received June 29, 2004. Accepted for publication February 11, 2005.
Financial support: This study was funded by the European Commission, LEISHNATDRUG-R ICA4-2000-10109.
* Address correspondence to Vanessa Yardley, ITD, LSHTM, Keppel Street, London WC1E 7HT, United Kingdom. E-mail: Vanessa. Yardley{at}lshtm.ac.uk; scroft{at}dndi.org ![]()
Authors addresses: Vanessa Yardley and Simon Croft, London School of Hygiene & Tropical Medicine (University of London), Department of Infectious and Tropical Diseases, Keppel Street, London WC1E 7HT, UK. Telephone: +44 (0)20 7927-2462, Fax: +44 (0)20 7927-2807, E-mail: vanessa.yardley{at}lshtm.ac.uk, simon.croft{at}lshtm.ac.uk. Simonne de Doncker and Jean-Claude Dujardin, ITMA, Protozoology Unit, Nationalestraat 155, B-2000 Antwerpen, Belgium. Telephone: +32 3 2476358, Fax: +32 3 2476359, E-mail: SDoncker{at}proto.itg.be, jcdujard{at}itg.be. Cesar Miranda and Alejandro Llanos-Cuentas, Universidad Peruana Cayetano Heredia, Insituto de Medicine Tropical "Alexander von Humbolt," P.O. Box 4214, Lima 100, Peru. Telephone: +511 4827739, Fax: +511 3820338, E-mail: cesar.miranda{at}mail.mcgill.ca, allanos{at}upch.edu.pe. Siddhartha Koirala and Suman Rijal, BP Koirala Institute of Health Sciences, Dharan, Nepal. Telephone: +977 25 25555 ext 2052, Fax: +977 25 20251, E-mail: siddharthakoirala2001{at}yahoo.com, sumanrijal2{at}yahoo.com. Francois Chappuis, Travel & Migration Medicine Unit, Geneva University Hospital, 24 Micheli-du-Crest, 1211 Geneva-14, Switzerland. Telephone: +41 22 3729620, Fax: +41 22 3729626, E-mail: francois.chappuis{at}hcuge.ch.
Reprint requests: Vanessa Yardley, ITD, LSHTM, Keppel Street, London WC1E 7HT, UK. Fax: +44 (0)20 7927 2807, E-mail: vanessa.yardley{at}lshtm.ac.uk.
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