Modulation of the catalytic activity of cruzipain, the major cysteine proteinase from Trypanosoma cruzi, by temperature and pH

Cysteine proteinases are relevant to several aspects of the parasite life cycle and of parasite-host relationships. Here, a quantitative investigation of the effect of temperature and pH on the total substrate inhibition of cruzipain, the major papain-like cysteine proteinase from Trypanosoma cruzi, is reported. Values of the apparent catalytic and inhibition parameters Km, Vmax, Vmax/Km, and K(i) for the cruzipain-catalysed hydrolysis of N-alpha-benzyloxycarbonyl-L-phenylalanyl-L-arginine-(7-amino-4-methylcoumarin) (Z-Phe-Arg-AMC) and azocasein were determined between 10.0 degrees C and 40.0 degrees C and between pH 4.5 and 8.5. Values of Km were independent of temperature and pH, whereas values of Vmax, Vmax/Km, and K(i) were temperature-dependent and pH-dependent. Over the whole pH range explored, values of logVmax, log(Vmax/Km), and logK(i) increased linearly with respect to T(-1). Values of Vmax and Vmax/Km were affected by the acid-base equilibrium of one temperature-independent ionizing group (i.e. pK(unl)' = pK(lig)' = 5.7 +/- 0.1, at 25.0 degrees C). Moreover, values of K(i) were affected by the alkaline pK shift of one ionizing group of active cruzipain (from pK(unl)" = 5.7 +/- 0.1 to pK(lig)" = 6.1 +/- 0.1, at 25.0 degrees C) upon Z-Phe-Arg-AMC binding. Values of logK(unl)', logK(lig)', and logK(lig)" were temperature-independent. Conversely, values of logK(unl)" were linearly dependent on T(-1). As a whole, total substrate inhibition of cruzipain decreased with increasing temperature and pH. These data suggest that both synthetic and protein substrates can bind to the unique active centre of cruzipain either productively or following a binding mode which results in enzyme inhibition. However, allosteric effect(s) cannot be excluded.

NO donors inhibit Leishmania infantum cysteine proteinase activity

Nitric oxide (NO) releasing drugs (e.g., glyceryl trinitrate) were successfully used in the treatment of cutaneous leishmaniasis in man. In the present study, the effect of NO donors on the catalytic activity of the cysteine proteinase from promastigotes of Leishmania infantum, an agent of Old World visceral and cutaneous leishmaniases, is reported. In particular, one equivalent of NO, released by the NO donors S-nitrosoglutathione, glyceryl trinitrate, (+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide, 3-morpholinosydnonimine, S-nitrosoacetylpenicillamine and sodium nitroprusside, inhibited one equivalent of the parasite cysteine proteinase. As expected, NO-deprived compounds did not affect the catalytic activity of the parasite cysteine proteinase. Furthermore, the absorption spectrum of the (+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide-treated inactive L. infantum enzyme displayed a maximum in the 330-350 nm wavelength range. The reducing agents dithiothreitol and L-ascorbic acid completely prevented parasite cysteine proteinase inhibition by NO, fully restored the catalytic activity, and reversed the NO-induced absorption spectrum of the inactive enzyme. Moreover, S-nitrosoacetylpenicillamine displayed a leishmanicidal effect, inhibiting the cysteine proteinase activity in vivo. As expected, the NO-deprived compound N-acetylpenicillamine did not affect significantly the parasite viability and the enzyme activity in vivo. These data suggest that the L. infantum cysteine proteinase undergoes NO-mediated S-nitrosylation, thereby representing a possible mechanism of antiparasitic host defence.

[A Pediatric case of lupoid leishmaniasis diagnosed by PCR]

The purpose of this paper is to describe the clinical features of lupoid leishmaniasis in a child and to underline the use of PRC as a necessary and reliable tool in controversial diagnosis. Lupoid leishmaniasis, also known as chronic or relapsing leishmaniasis, is mainly widespread in the Middle East, where it represents up to 5% of all cutaneous Leishmaniasis. It strongly resembles Lupus Vulgaris, both clinically and histologically, and is therefore not usually diagnosed immediately but after a certain period of time. The amastigotic forms are rare or absent. The cutaneous nodules or plaques can slowly enlarge over the years. The case of an eleven-year-old albanian child living in Durazzo (Albania), suffering since three years with a plaque formed by apple-jelly nodules and scars on his right cheek, is presented. Using PCR, the presence of Leishmania infantum DNA led to a diagnosis of lupoid leishmaniasis. The therapeutic strategy of a combination of oral itraconazole and infiltration of metilglucamina antimoniate has been carried out, with good result, as checked through "telemedicine".

[Concordance of leishmaniasis cutaneous tests in Tunisia]

A cross sectional study aimed to evaluate the effect of antigenic preparation (Leishmania infantum versus Leishmania major) and dose of leishmania antigens (5 x 10(6) versus 2.5 x 10(6) parasites in the same volume) on the reproducibility of delayed type hypersensitivity leishmania skin test. Results showed that among 34 individuals involved from visceral leishmaniasis endemic area. 26 (76.5%) had a positif Leishmania infantum leishmania (L-L. infantum) test and 27 (79.4%) to Leishmania major leishmania (L-L. major). Mean size of cutaneous reaction was 5.94 +/- 2.86 mm for L-L. infantum and 5.41 +/- 3.23 mm for L-L. major, with a significant positive linear association (p < 10-3). Intra-class correlation coefficient was 0.80 (CI95% = [0.64-0.93]) and concordance Kappa (kappa) was 0.57 (CI95% = [0.40-0.74]). Among 153 individuals from zoonotic cutaneous leishmaniasis. 92.9% revealed a positive test for both types of leishmanin (L-L. major full dose versus L-L. major half dose). Mean size of cutaneous reaction was 12.61 +/- 4.65 mm for the reference test and 11.30 +/- 3.95 mm for diluted one, with a positive linear association (p < 10-3). Intra-class correlation coefficient was 0.78 (IC95% = [0.71-0.84]) and concordance Kappa (kappa) was 0.82 (IC95% = [0.73-0.91]). These results demonstrate a limited effect of leishmania antigenic variation and antigen dose on the reproducibility of delayed type hypersensitivity induced by the leishmanin test.

Chemiluminescence activity in whole blood phagocytes of dogs naturally infected with Leishmania infantum

Dogs are the domestic reservoir of Leishmania infantum, a vector-borne intracellular protozoan agent of human visceral leishmaniasis. The role of polymorphonuclear leukocytes (PMNs) in the immune defence against this parasite has been poorly studied. We have investigated the function of peripheral blood PMNs in naive beagle dogs that have been naturally exposed to phlebotomine vectors in an area highly endemic for canine leishmaniasis, and found infected by Leishmania at the end of the transmission season. Whole blood phagocyte oxidative metabolism was assessed by a rapid method that determines a luminol-amplified chemiluminescence (CL) emission. This was evaluated using either a soluble stimulant, phorbol mirystate acetate (PMA), or phagocytic stimuli, such as zymosan unopsonized (ZYM) or opsonized with autologous serum (OPZ). In blood samples taken 2 months after exposure to Leishmania transmission, data on CL emission revealed a significant decrease of reactive oxygen intermediates (ROI) production in the presence of both PMA and ZYM, compared with blood samples obtained from dogs before exposure. On the contrary, no variations in CL emission were detected in presence of OPZ. Our data indicate that immunological changes occur early in canine leishmaniasis and confirm that the role of PMNs and their products need to be clarified.

Nitric oxide inhibits cruzipain, the major papain-like cysteine proteinase from Trypanosoma cruzi

Nitric oxide (NO) is a pluripotent regulatory molecule showing, among others, an antiparasitic activity. Moreover, NO inhibits cysteine proteinase action by nitrosylating the Cys catalytic residue. In the present study, the inhibitory effect of the substrate N-alpha-benzyloxycarbonyl-L-phenylalanyl-L-arginine-(7-amino-4-methyl coumarin) and of NO on the catalytic activity of cruzipain, the major papain-like cysteine proteinase from Trypanosoma cruzi (the hemoflagellate protozoan parasite which causes the American trypanosomiasis), is reported. In particular, NO-donors S-nitroso-glutathione (GSNO), (+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (NOR-3), 3-morpholinosydnonimine (SIN-1), S-nitroso-acetyl-penicillamine (SNAP), and sodium nitroprusside (SNP) dose-dependently inhibited cruzipain, this effect being likely attributable to the S-nitrosylation of the Cys25 catalytic residue. These results were analyzed in parallel with those concerning the inhibitory effect of the substrate and of NO on the catalytic activity of falcipain, the cruzipain-homologous cysteine proteinase from Plasmodium falciparum. The modulation of the cruzipain and falcipain activity by NO may be relevant in developing new strategies against T. cruzi and P. falciparum in human host. As a whole, the NO-mediated S-nitrosylation of pathogenic viral, bacterial, fungal, and parasitic cysteine proteinases may represent a general mechanism of antimicrobial and antiparasitic host defences.

Decreased lipid fluidity of the erythrocyte membrane in dogs with leishmaniasis-associated anaemia

In both man and the dog, anaemia resulting from natural leishmaniasis is often severe and mainly associated with a shortened life span of erythrocytes. Lipid fluidity of erythrocyte membranes from 17 dogs with anaemia caused by visceral leishmaniasis was investigated by means of fluorescence polarization. Results were compared with those from three groups of control animals (10 healthy dogs, seven dogs with visceral leishmaniasis but no anaemia, and 10 dogs with anaemia unrelated to leishmaniasis). Fluorescence polarization values recorded for animals with leishmaniasis-associated anaemia were elevated-indicating reduced erythrocyte membrane fluidity-and significantly higher than in the control groups. Mechanical sequestration by the spleen due to increased cell rigidity, or alterations in receptor/ligand erythrocyte cytoadherence mechanisms, or both, may result from decreased membrane fluidity and hence contribute to the anaemia of Leishmania -infected dogs.

Nitric oxide inhibits falcipain, the Plasmodium falciparum trophozoite cysteine protease

Nitric oxide (NO) is a pluripotent regulatory molecule possessing, among others, an antiparasitic activity. In the present study, the inhibitory effect of NO on the catalytic activity of falcipain, the papain-like cysteine protease involved in Plasmodium falciparum trophozoite hemoglobin degradation, is reported. In particular, NO donors S-nitrosoglutathione (GSNO), (+/-)-(E)-p6ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenami de (NOR-3), 3-morpholinosydnonimine (SIN-1), and sodium nitroprusside (SNP) inhibit dose-dependently the falcipain activity present in the P. falciparum trophozoite extract, this effect likely attributable to S-nitrosylation of the Cys25 catalytic residue. The results represent a new insight into the modulation mechanism of falcipain activity, thereby being relevant in developing new strategies for inhibition of the P. falciparum life cycle.

Early suppression of lymphoproliferative response in dogs with natural infection by Leishmania infantum

Dogs are the domestic reservoirs of zoonotic visceral leishmaniasis caused by Leishmania infantum. Early detection of canine infections evolving to clinically patent disease may be important to leishmaniasis control. In this study we firstly investigated the peripheral blood mononuclear cell (PBMC) response to leishmanial antigens and to polyclonal activators concanavalin A, phytohemagglutinin and pokeweed mitogen, of mixed-breed dogs with natural L. infantum infection, either in presymptomatic or in patent disease condition, compared to healthy animals. Leishmania antigens did not induce a clear proliferative response in any of the animals examined. Furthermore, mitogen-induced lymphocyte proliferation was found strongly reduced not only in symptomatic, but also in presymptomatic dogs suggesting that the cell-mediated immunity is suppressed in progressive canine leishmaniasis. To test this finding, naive Beagle dogs were exposed to natural L. infantum infection in a highly endemic area of southern Italy. Two to 10 months after exposure all dogs were found to be infected by Leishmania, and on month 2 of exposure they all showed a significant reduction in PBMC activation by mitogens. Our results indicate that suppression of the lymphoproliferative response is a common occurrence in dogs already at the beginning of an established leishmanial infection.

A cloned antigen (recombinant K39) of Leishmania chagasi diagnostic for visceral leishmaniasis in human immunodeficiency virus type 1 patients and a prognostic indicator for monitoring patients undergoing drug therapy

Serologic assays using crude antigens for the diagnosis of visceral leishmaniasis in human immunodeficiency virus type 1 (HIV)-seropositive patients have been shown to lack sensitivity and specificity, particularly in AIDS patients. Antibodies to a cloned antigen, recombinant (r) K39, of Leishmania chagasi are specific for members of the Leishmania donovani complex and have been shown to indicate active disease in immunocompetent persons. This study demonstrated that antibodies to rK39 were also detectable in HIV-seropositive patients coinfected with Leishmania infantum. Furthermore, the rK39 ELISA was more sensitive than an IFA for detecting L. infantum infections in patients with AIDS. In addition, antibody titers to rK39 in HIV-negative patients infected with L. infantum or L. chagasi declined during treatment with meglumine antimoniate or liposomal amphotericin B. In contrast, most patients who clinically relapsed showed increased antibody titers to rK39. These data demonstrate the diagnostic and prognostic utility of rK39 in detecting active visceral leishmaniasis.

Comparative efficacy of meglumine antimoniate and aminosidine sulphate, alone or in combination, in canine leishmaniasis

Thirty-two domestic dogs naturally infected with Leishmania infantum and showing viscero-cutaneous signs of canine leishmaniasis were treated with aminosidine sulphate (11 dogs) meglumine antimoniate (10 dogs) or with a combination of the two drugs (11 dogs) for 21 consecutive days. Clinical and laboratory assessments, made on day 21 and at 2, 4 and 6 months after initiation of treatment, showed that the drug combination gave the best score in terms of clinical efficacy, incidences of early clinical relapse, any clinical relapse or apparent parasitological cure, and reduction in parasite densities in bone-marrow and lymphnode aspirates (even though a lower dose of antimonial was used in the combination than for antimonial monotherapy). For each of the above parameters, however, the higher efficacy of the drug combination was not statistically significant, probably because of the large variations caused by using naturally infected animals of various ages and breeds.

Diffuse necrotic hepatic lesions due to visceral leishmaniasis in AIDS

A rare case of an AIDS patient who developed scattered necrotic involvement of the liver caused by Leishmania infantum is described. Of interest, marked splenomegaly, hypergammaglobulinemia and serum anti-Leishmania antibodies were absent and an incomplete response to therapy was observed. Diagnosis of visceral leishmaniasis (VL) was achieved by the demonstration of numerous amastigotes in both hepatocytes and macrophages on liver biopsy. Hepatic necrotic lesions, which when extensive could lead to acute hepatic failure, possibly reflect an atypical manifestation of liver involvement caused by L. infantum and depend on the immunological impairment which characterizes AIDS patients, thus preventing the formation of granulomas. Our observation confirms that VL can manifest atypical aspects in HIV-positive patients depending on the degree of the immunodeficiency. The frequency and severity of this pathology accounts for the need to list VL among AIDS-defining conditions.

A retrospective clinical study of canine leishmaniasis in 150 dogs naturally infected by Leishmania infantum

The clinical and laboratory findings observed in 150 dogs naturally infected by Leishmania infantum, from a large endemic area of southern Italy, are described. There was a gradual onset of clinical signs and the course of the disease was progressive in almost all the cases. The majority of the dogs were mongrels (43.3 per cent), male (64.7 per cent), of medium size (50.6 per cent), three to seven years old (64.7 per cent), and living outdoors (60 per cent). They showed generalised (56.7 per cent) or symmetrical (32 per cent) lymphadenomegaly; the mucous membranes of 87 of the dogs (58 per cent) were pale and moderate or severe splenomegaly was diagnosed in 80 dogs (53.3 per cent); weight loss was observed in 32 per cent of the animals. Skin abnormalities were very common, and included dry exfoliative dermatitis (56 per cent), ulcers (40 per cent) periorbital alopecia ('lunettes') (18 per cent), diffuse alopecia (14 per cent) and onychogryphosis (24 per cent). Ocular signs were observed in 24 dogs (16 per cent) including 16 cases of keratoconjunctivitis (three with keratoconjunctivitis sicca), six cases of moderate uveitis and two cases of panophthalmitis. The acute form of the disease was diagnosed in only six dogs and was characterised by fever and generalised lymphadenomegaly, and by the absence of skin lesions. Another six dogs had severe renal failure without systemic clinical signs of leishmaniasis. The most important laboratory findings were a severe or moderate increase in gammaglobulins, hypoalbuminaemia, hyperproteinemia and anaemia. Cultures or cytology tests for L infantum parasites were positive in 134 of the dogs. Following the standard procedures developed for human lymph node and bone marrow cytology tests, the leishmania density in the dogs varied from 1+ to 2+. Leishmania antibody titres were high (> 1:160) in almost all the dogs. Immunological tests for autoantibodies were positive in 25 of 53 dogs tested in the antinuclear antibody (ANA) test, in 15 of 43 dogs tested in the latex test and in five of 24 dogs tested in the Coombs test.

Treatment of visceral leishmaniasis in children with liposomal amphotericin B

We used liposomal amphotericin B as first-choice treatment of visceral leishmaniasis in 106 immunocompetent children who acquired the infection in a temperate region of southern Europe (Italy) where Leishmania infantum visceral leishmaniasis is endemic. The aim of the study was to identify the minimum total dose of liposomal amphotericin B needed to cure the infection in children and reduce the period of hospitalization. We conclude that the optimal regimen in immunocompetent children with L. infantum visceral leishmaniasis to be a total dose of 18 mg/kg of liposomal amphotericin B (3 mg/kg per day for 5 days, followed by 3 mg/kg administered as an outpatient regimen on day 10).

Epidemiologic surveillance of visceral leishmaniasis in Sicily, Italy

Visceral leishmaniasis (VL) is endemic in Sicily. Although it is a notifiable disease, there is evidence that the actual number of cases is higher than that reported. In 1987, a regional reference center for active surveillance of VL was established and it recorded a total of 284 cases through 1995, a mean of 31.5 cases/year and about four-fold more than previously reported. Of the 284 cases, 150 (53%) were children (< or = 14 years of age), and of the 134 adults, 39 (29%) were coinfected with human immunodeficiency virus (HIV). The commonest viscerotropic zymodeme of Leishmania infantum, MON 1, was identified in 40 (93%) of 43 HIV-negative and eight (57%) of 14 HIV-positive patients. Among 280 patients evaluated (i.e., all HIV-negative and 35 of 39 HIV-positive subjects), 254 (91%) were treated with meglumine antimoniate alone or in combination with other drugs; 23 (8%) received allopurinol or amphotericin B, either conventional or in liposomal form; and three terminally ill patients were not treated. Among the 245 HIV-negative patients, 236 (96%) were successfully cured, while nine (4%) (seven adults) died during the course of antimonial treatment. None of the 35 HIV-positive patients was definitively cured, although mortality was apparently associated with other opportunistic infections.

[Eco-epidemiological study of Phlebotomus perniciosus in foci of visceral leishmaniasis in Campania]

An entomological survey was carried out during the sandfly season (June-October) of 1993 in three of the main visceral leishmaniasis (VL) foci of the Campania region of Italy. During the period 1989-1993, 39 VL cases were recorded in the three foci: 19 in Maddaloni, 14 in Ercolano and 6 in Ischia. For each focus, collecting stations representative of sandfly habitats (domestic, peri-domestic and sylvatic) located in urban, peri-urban and rural areas were selected for the sandfly investigation. Three monthly captures by means of sticky traps (20 x 20 cm) were carried out in each station. A total of 2,773 sandfly specimens were caught and identified as belonging to 4 species: Phlebotomus perniciosus (66.2%). P. mascittii (0.4%). P. papatasi (0.2%) and Sergentomyia minuta (33.2%). P. perniciosus, the proven vector of VL in Italy, showed the highest prevalence in all foci studied, Maddaloni (61.0%). Ercolano (62.5%) and Ischia (88.2%); the absolute density of the species (number of specimens/m2 of sticky trap) was not so high in all areas and habitats sampled, the values observed being between 0.14 and 22.05/m2. The relationship between the eco-epidemiological aspects and the distribution of P. perniciosus in the foci investigated is discussed.

Short-course treatment of visceral leishmaniasis with liposomal amphotericin B (AmBisome)

We evaluated liposomal amphotericin B (AmBisome; Vestar, San Dimas, CA) administered to 88 immunocompetent patients (56 children) with visceral leishmaniasis (VL) caused by Leishmania infantum. Thirteen patients received 4 mg/kg on days 1-5 and 10 (total dose, 24 mg/kg), and all were cured; 42 received 3 mg/kg on days 1-5 and 10 (18 mg/kg), and 41 were cured; 32 received 3 mg/kg on days 1-4 and 10 (15 mg/kg), and 29 were cured (amastigotes were not cleared from 1 child, and 2 relapsed). One adult was cured with a total dose of 12mg/kg. The four children who were not cured received 3 mg/kg for 10 days; none had further relapses. There were no significant adverse events. For VL due to L. infantum, we recommended a total dose of AmBisome of > or = 20 mg/kg, given in > or = 5 doses of 3-4 mg/kg over > or = 10 days.

Epidemiological surveillance of leishmaniasis in HIV-1-infected individuals in Italy

OBJECTIVE

To actively detect leishmaniasis in HIV-1-infected individuals in Italy, to describe the epidemiological features of the disease in these patients, and to compare them with epidemiological features of leishmaniasis in HIV-negative patients.

DESIGN

Retrospective and prospective surveillance study.

PATIENTS

Italian patients with HIV-1 infection and leishmaniasis diagnosed between 1985 and 1994.

RESULTS

We recorded 116 leishmaniasis cases (115 visceral leishmaniasis), of which 94 (81%) were diagnosed over the last 4 years. Seventy-eight patients (67%) fulfilled the 1993 Centers for Disease Control and Prevention AIDS criteria. Leishmaniasis was passively reported in only 18% of cases. Leishmania incidence estimated among approximately 2700 AIDS patients living in leishmaniasis endemic areas averaged 1.6%, with a maximum of 4.9% in Sicily. These rates were up to 500-fold higher than among HIV-negative individuals living in the same areas, and were similar to those of ubiquitous opportunistic agents indicative of AIDS condition. Data from two major endemic regions indicated that overlap of HIV-1 and Leishmania infections has focal characteristics. The occurrence of small case clusters would suggest occasional modes of Leishmania transmission different from the insect vector. The isoenzyme characterization of 38 Leishmania stocks showed a zymodeme spectrum qualitatively and quantitatively different from that of the parasitic agent of visceral leishmaniasis in HIV-negative adults.

CONCLUSIONS

Active surveillance provided reliable evaluation on the occurrence of HIV-Leishmania coinfections in Italy, although it was limited to hospital-based cases in this study due to general under-reporting of cases. Biological and epidemiological spectrum of the disease suggests that visceral leishmaniasis should be included among AIDS-defining pathologies.

Early efficacy of liposomal amphotericin B in the treatment of visceral leishmaniasis

The rapidity and efficacy of a short course of liposomal amphotericin B was evaluated in 29 children affected by visceral leishmaniasis (Leishmania infantum). Their overall health status was assessed using the prognostic inflammatory and nutritional index (PINI), and their haematological status by the reticulocyte count and haemoglobin blood levels. All these quantities were measured on day 0, and 3 and 10 d after starting therapy. A significant decrease of inflammatory signs, associated with an improved reticulocyte count, was recorded after 3 d of therapy. A significant increase of haemoglobin levels was also observed 10 d after the start of treatment. The early reduction of inflammatory signs and the improvement of bone marrow function in most patients confirmed the validity of amphotericin B therapy. The PINI score is helpful in assessing the severity of visceral leishmaniasis and the follow-up of its treatment.

Visceral leishmaniasis in HIV infected patients: treatment with high dose liposomal amphotericin B (AmBisome)

Visceral leishmaniasis (VL) in patients coinfected with human immunodeficiency virus (HIV) is often atypical, and characteristically relapses after treatment. We treated 10 HIV infected patients (9 men) with parasitologically confirmed VL with liposomal amphotericin B ("AmBisome': L-AMB) at a dose of 4 mg/kg/day on days 1, 2, 3, 4, 5, 10, 17, 24, 31, and 38. Patients were hospitalized for the first 5 days, and were monitored during, and 1 week and 1, 3 and 6 months after, L-AMB therapy. There were no serious adverse events, and L-AMB was well tolerated. 9/10 patients completed therapy, one patient defaulted at day 24. Clinical improvement was seen in all nine patients and the bone marrow aspirate was cleared of visible/culturable parasites in 8/9 patients. During follow-up, one patient defaulted. The seven remaining patients relapsed at 2, 3, 3, 5, 5, 6 and 7 months. Re-treatment with a variety of antileishmanial drugs was unsatisfactory. The time from first diagnosis of VL to death in six patients was 5-40 months (mean 18.8 months). Only one patient remained alive 26 months after treatment. L-AMB is safe and provides a good initial clinical response. Intermittent dosing enables a short period of hospitalization. However, relapse is probably inevitable.