Sodium stibogluconate resistance in Leishmania donovani correlates with greater tolerance to macrophage antileishmanial responses and trivalent antimony therapy

Co-treatment of mice infected with different strains of Leishmania donovani with a non-ionic surfactant vesicle formulation of buthionine sulfoximine (BSO-NIV), and sodium stibogluconate (SSG), did not alter indicators of Th1 or Th2 responses but did result in a significant strain-independent up-regulation of IL6 and nitrite levels by stimulated splenocytes from treated mice compared to controls. The efficacy of BSO-NIV/SSG treatment was dependent on the host being able to mount a respiratory burst indicating that macrophages are important in controlling the outcome of treatment. In vitro studies showed that SSG resistance was associated with a greater resistance to killing by activated macrophages, treatment with hydrogen peroxide or potassium antimony tartrate. Longitudinal studies showed that a SSG resistant (SSG-R) strain was more virulent than a SSG susceptible (SSG-S) strain, resulting in significantly higher parasite burdens by 4 months post-infection. These results indicate that SSG exposure may favour the emergence of more virulent strains.

Blood monocytes: differing effector role in experimental visceral versus cutaneous leishmaniasis

Irrespective of the tissue infected or the strain involved, all Leishmania species selectively parasitize and replicate within the resident tissue macrophage. Henry Murray here discusses the role of a second mononuclear phagocyte, the blood monocyte, which is also attracted to leishmanial lesions, but which appears to play quite different roles in experimental visceral versus cutaneous infection: in visceral disease, the monocyte is a critical host defense effector cell, in cutaneous disease, it may, paradoxically, serve to perpetuate intracellular infection.

Noninvasive management of Indian visceral leishmaniasis: clinical application of diagnosis by K39 antigen strip testing at a kala-azar referral unit

Firm diagnosis of visceral leishmaniasis (kala-azar) requires organ aspiration and microscopic examination of tissue specimens. To determine the usefulness of noninvasive diagnosis by strip test detection of anti-K39 immunoglobulin (Ig) G antibody in blood specimens obtained by fingerstick, 143 Indian patients with suspected kala-azar (fever, splenomegaly, anemia) were studied. Of 120 strip test-positive subjects (subjects with presumed kala-azar [group A]), amphotericin B treatment induced clinical cure in 119. Of 23 strip test-negative subjects (subjects presumed to have other diseases [group B]), 16 had other disorders diagnosed at entry, 4 responded to empiric antimalarial therapy, 2 were proven to have kala-azar, and 1 died elsewhere after undergoing splenic aspiration. Six months after treatment ended, all 120 patients in group A and the 18 assessable patients in group B were healthy. In a region in India where visceral infection is prevalent, strip test detection of anti-K39 IgG is a clinically promising diagnostic guide in persons with suspected kala-azar.

Immunochromatographic strip-test detection of anti-K39 antibody in Indian visceral leishmaniasis

Stored sera from 429 Indian subjects were assayed to extend the analysis of the accuracy of immunochromatographic strip-test detection of anti-K39 antibody in the non-invasive diagnosis of visceral leishmaniasis (VL). All 225 samples from patients with proven Leishmania infection tested positive [estimated sensitivity = 100%; 95% confidence interval (CI)=98%-100%]. Sera from 99 of the 100 symptomatic patients with other diseases were non-reactive (estimated specificity = 99%; CI = 94%-100%). However, samples from 13 of the 104 apparently healthy controls showed positive strip-test results (estimated specificity = 88%; CI = 79%-93%), yielding an overall specificity of 93% (190/204; CI = 88%-96%). If applied in a practical clinical setting (on symptomatic patients in whom active VL is suspected and other common infections have been excluded), strip testing of serum for anti-K39 antibody should be both sensitive and specific for diagnosing VL in India.

Tissue granuloma structure-function in experimental visceral leishmaniasis

In experimental visceral leishmaniasis in normal mice (BALB/c, C57BL/6) acquired resistance to Leishmania donovani, a protozoan which targets tissue macrophages, depends upon T cells, Th1 cell-type cytokine generation and activated mononuclear phagocytes. In the intact host, initial control and eventual resolution of L. donovani hepatic infection in normal mice is expressed by and accomplished within well-formed, mature tissue granulomas. In the liver, these immunologically active, inflammatory structures are assembled around a core of fused, parasitized resident macrophages (Kupffer cells) which come to be encircled by both cytokine-secreting T cells and influxing leishmanicidal blood monocytes. This pro-host defense granuloma structure-function relationship, in which histologically mature granulomas provide the microenvironment for intracellular L. donovani killing, however, is only one of seven which have been identified through experimental modifications in this model. This report reviews these structure-function relationships and illustrates the broad spectrum of additional possible responses. These responses range from structurally intact granulomas which provide no antileishmanial function (the 'ineffective' granuloma), to enlarged granulomas which show enhanced parasite killing (the 'hypertrophied' granuloma), to effective antileishmanial activity in the absence of any tissue reaction (the 'invisible' granuloma).

Treatment of Indian visceral leishmaniasis with single or daily infusions of low dose liposomal amphotericin B: randomised trial

OBJECTIVE

To test short course, low dose liposomal amphotericin B as single or daily infusion treatment in Indian visceral leishmaniasis (kala-azar).

DESIGN

Randomised, open label study.

SETTING

Inpatient unit for leishmaniasis in Bihar, India.

PARTICIPANTS

91 adults and children with splenic aspirate positive for infection.

INTERVENTIONS

Total dose of 5 mg/kg of liposomal amphotericin B given as a single infusion (n=46) or as once daily infusions of 1 mg/kg for five days (n=45).

MAIN OUTCOME MEASURES

Clinical and parasitological cure assessed 14 days after treatment and long term definitive cure (healthy, no relapse) at six months.

RESULTS

All but one person in each group had an initial apparent cure. During six months of follow up, three patients in the single dose group and two in the five dose group relapsed. Complete response (definitive cure) was therefore achieved in 84 of 91 subjects (92%): 42 of 46 patients in the single dose group (91%, 95% confidence interval 79% to 98%) and 42 of 45 in the five dose group (93%, 82% to 99%). Response rates in the two groups were not significantly different.

CONCLUSION

Low dose liposomal amphotericin B (5 mg/kg), given either as a five day course or as a single infusion, seems to be effective for visceral leishmaniasis and warrants further testing.

Suppression of posttreatment recurrence of experimental visceral Leishmaniasis in T-cell-deficient mice by oral miltefosine

T-cell-deficient nude mice infected with Leishmania donovani were treated with miltefosine and then given either no treatment or intermittent miltefosine. Intracellular visceral infection recurred in untreated mice but was suppressed by once- or twice-weekly oral administration of miltefosine. Miltefosine may be useful as oral maintenance therapy for T-cell-deficient patients with visceral leishmaniasis.

Visceral leishmaniasis in mice devoid of tumor necrosis factor and response to treatment

Tumor necrosis factor (TNF)-deficient mice were challenged with Leishmania donovani to characterize TNF in the response of visceral intracellular infection to antileishmanial chemotherapy. In wild-type controls (i) liver infection peaked at week 2 and resolved, (ii) discrete liver granulomas developed at weeks 2 to 4 and involuted, and (iii) leishmanicidal responses to antimony (Sb), amphotericin B (AmB), and miltefosine were intact. In TNF knockout (KO) mice (i) initial liver infection was unrestrained, plateaued, and then declined somewhat by week 6, (ii) an absent early granulomatous reaction abruptly accelerated with striking tissue inflammation, widespread hepatic necrosis, and 100% mortality by week 10, and (iii) while the initial response to AmB and miltefosine was intact, killing induced by Sb therapy was reduced by >50%. Although initial AmB treatment during weeks 2 to 3 killed 98% of liver parasites, 75% of AmB-treated KO mice subsequently relapsed and died by week 12; however, additional maintenance AmB preserved long-term survival. These results for a model of visceral infection indicate that endogenous TNF is required early on to control intracellular L. donovani, support granuloma development, and mediate optimal initial effects of Sb and prevent relapse after ordinarily curative AmB treatment. A compensatory, TNF-independent antileishmanial mechanism developed in TNF KO mice; however, its effect was uncontrolled fatal inflammation. Chemotherapeutic elimination of the parasite stimulus reversed the hyperinflammatory response and preserved survival.

Mononuclear cell recruitment, granuloma assembly, and response to treatment in experimental visceral leishmaniasis: intracellular adhesion molecule 1-dependent and -independent regulation

In experimental visceral leishmaniasis, acquired resistance to intracellular Leishmania donovani is Th1 cell cytokine dependent and largely mediated by gamma interferon (IFN-gamma); the same response also permits conventional antimony (Sb) chemotherapy to express its leishmanicidal effect. Since the influxing blood monocyte (which utilizes endothelial cell ICAM-1 for adhesion and tissue entry) is a primary effector target cell for this cytokine mechanism, we tested the monocyte's role in host responsiveness to chemotherapy in mice with ICAM-1 gene disruptions. Mutant animals failed to develop any early granulomatous tissue response in the liver, initially supported high-level visceral parasite replication, and showed no killing after Sb treatment; the leishmanicidal response to a directly acting, alternative chemotherapeutic probe, amphotericin B, was intact. However, mutant mice proceeded to express a compensatory, ICAM-1-independent response leading to mononuclear cell influx and granuloma assembly, control over visceral infection, and the capacity to respond to Sb. Together, these results point to the recruitment of emigrant monocytes and mononuclear cell granuloma formation, mediated by ICAM-1-dependent and -independent pathways, as critical determinants of host responsiveness to conventional antileishmanial chemotherapy.

Interleukin-12 regulates the response to chemotherapy in experimental visceral Leishmaniasis

In experimental visceral leishmaniasis, interleukin (IL)-12 initiates control over Leishmania donovani via Th1 cell activation, interferon (IFN)-gamma secretion, and granuloma formation. Because the leishmanicidal effect of conventional therapy, pentavalent antimony (Sb), also requires T cells and endogenous IFN-gamma, we tested IL-12 as a determinant of host responsiveness to chemotherapy. L. donovani-challenged IL-12p35 gene knockout (KO) mice permitted uncontrolled hepatic infection and failed to respond to Sb. In contrast, 96% of liver parasites in KO mice were killed by amphotericin B, which acts independently of immune responses. Exogenous IL-12 combined with Sb was tested in normal mice: low-dose Sb was converted from weakly to strongly leishmanicidal, and a no-effect Sb dose was converted to approximately 100% leishmanistatic. IL-12 plus Sb synergism in normal mice was IFN-gamma dependent; however, IL-12 also increased responsiveness to Sb in IFN-gamma KO mice. Thus, IL-12 regulates host IFN-gamma-dependent and -independent responses that permit and/or enhance the leishmanicidal activity of Sb.

Failure of pentavalent antimony in visceral leishmaniasis in India: report from the center of the Indian epidemic

In India, 320 patients with visceral leishmaniasis (209 in the state of Bihar and 11 in the neighboring state of Uttar Pradesh) received identical pentavalent antimony (Sb) treatment. Sb induced long-term cure in 35% (95% confidence interval [CI], 28%-42%) of those in Bihar versus 86% (95% CI, 79%-93%) of those in Uttar Pradesh. In Bihar, the center of the Indian epidemic, traditional Sb treatment should be abandoned.

Short-course of oral miltefosine for treatment of visceral leishmaniasis

A total of 54 Indian patients with visceral leishmaniasis were treated with oral miltefosine, 50 mg given twice daily, for 14 days (18 patients; group A), 21 days (18; group B), or 28 days (18; group C). Cure was achieved in 89% of group A, 100% of group B, and 100% of group C. Adverse reactions were self-limited and primarily mild. The 21-day miltefosine regimen combines high-level efficacy, convenient dosing, and a relatively short duration.

Short-course, cost-effective treatment with amphotericin B-fat emulsion cures visceral leishmaniasis

Although short-course therapy with new lipid formulations of amphotericin B represents an advance over lengthy traditional treatments in visceral leishmaniasis (kala-azar), high cost has rendered these agents largely irrelevant in developing countries where the disease is endemic. Therefore, we tested standard amphotericin B deoxycholate mixed with a commercial fat emulsion as short-course treatment for Indian visceral leishmaniasis in Bihar in 1997/98. Seventy children and adults with splenic aspirate-documented infection, 23 of whom had failed prior antimony (Sb) therapy, received 5 alternate-day infusions of 2 mg/kg. Apparent cure, which required a parasite-free splenic aspirate smear, was assessed 20 days after treatment (day 30); definitive cure was determined at 6 months. Other than anticipated infusion-related fever and/or chills, treatment was safe and well tolerated. One patient required dose modification because of mild, reversible renal insufficiency. Sixty-nine patients (98.6%, CI 92.3-100%) had apparent cures; during follow-up, there were 4 treatment failures (relapses, 3; unrelated death, 1), yielding definitive cures in 65 of 70 patients (92.9%, CI 84.1-97.6%). Including retreatment costs for patients in Bihar (who now often fail initial Sb therapy), the final per patient cost of the tested regimen (US $260) was 59% and 43% less than treatment with Sb or conventional amphotericin B alone, respectively. Short-course treatment with amphotericin B-fat emulsion is active, cost-effective treatment for patients with visceral leishmaniasis including those with Sb-unresponsive infection.

Visceral leishmanicidal activity of hexadecylphosphocholine (miltefosine) in mice deficient in T cells and activated macrophage microbicidal mechanisms

Hexadecylphosphocholine (miltefosine), a membrane-active alkylphospholipid, may be the first effective oral agent for visceral leishmaniasis, an intracellular protozoal infection of tissue macrophages. In vitro, miltefosine stimulates T cells and macrophages to respond to and secrete activating cytokines, including interferon (IFN)-gamma, and enhances macrophage production of microbicidal reactive nitrogen and oxygen intermediates (RNIs and ROIs, respectively). To determine whether these effects mediate miltefosine's in vivo leishmanicidal efficacy, genetically deficient mice were infected with Leishmania donovani. Intracellular visceral killing was retained in mice lacking or deficient in T cells, endogenous IFN-gamma, and macrophage generation of leishmanicidal RNIs and ROIs. Although mutant mice responded to miltefosine in the absence of tissue granulomas, treatment enhanced granuloma assembly in normal animals. These results suggest that miltefosine's visceral leishmanicidal effect does not require host T cell-dependent or activated macrophage-mediated mechanisms; thus, this agent may potentially be useful in treating T cell-deficient patients with kala-azar.

Roles of endogenous gamma interferon and macrophage microbicidal mechanisms in host response to chemotherapy in experimental visceral leishmaniasis

In experimental visceral leishmaniasis, in which the tissue macrophage is the target, in vivo responsiveness to conventional chemotherapy (pentavalent antimony [Sb]) requires a T-cell-dependent mechanism. To determine if this mechanism involves gamma interferon (IFN-gamma)-induced activation and/or specific IFN-gamma-regulated macrophage leishmanicidal mechanisms (generation of reactive nitrogen or oxygen intermediates, we treated gene-deficient mice infected with Leishmania donovani. In IFN-gamma gene knockout (GKO) mice, Sb inhibited but did not kill intracellular L. donovani (2% killing versus 76% in controls). Sb was active (>94% killing), however, in both inducible nitric oxide synthase (iNOS) knockout (KO) and respiratory burst (phagocyte oxidase)-deficient chronic granulomatous disease (X-CGD) mice. Sb's efficacy was also maintained in doubly deficient animals (X-CGD mice treated with an iNOS inhibitor). In contrast to Sb, amphotericin B (AmB) induced high-level killing in GKO mice; AmB was also fully active in iNOS KO and X-CGD animals. Although resolution of L. donovani infection requires iNOS, residual visceral infection remained largely suppressed in iNOS KO mice treated with Sb or AmB. These results indicate that endogenous IFN-gamma regulates the leishmanicidal response to Sb and achieves this effect via a pathway unrelated to the macrophage's primary microbicidal mechanisms. The role of IFN-gamma is selective, since it is not a cofactor in the response to AmB. Treatment with either Sb or AmB permits an iNOS-independent mechanism to emerge and control residual intracellular L. donovani infection.

Oral treatment of visceral leishmaniasis with miltefosine

In a pilot trial, 28 days of oral treatment with 100-200 mg miltefosine (hexadecylphosphocholine) per day cured 14 of 15 patients with Indian visceral leishmaniasis (VL). To extend the testing of this regimen, 45 additional subjects with VL, of whom 17 had failed previous antimony therapy, were treated with 100 (N = 17), 150 (N = 18) or 200 (N = 10) mg/day. Enrollment at 200 mg/day was stopped after three subjects in this treatment arm developed reversible but serious (grade-3) adverse reactions. The overall clinical and parasitological responses to miltefosine were rapid, with 40 [89%; 95% confidence interval (CI) = 76%-96%] and 44 (98%; CI = 88%-100%) of the patients apparently cured on days 14 and 28, respectively. The one 'treatment failure' recorded on day 28 (and at 6 months) was a subject lost to follow-up. Those apparently cured by day 28 included six patients (one on 100 mg, two on 150 mg and three on 200 mg/day) removed from treatment on days 7-17 because of grade-3 diarrhoea (two cases), vomiting (two cases), diarrhoea and hepatotoxicity (one case) or nephrotoxicity (one case). Transient, mild-moderate vomiting and/or diarrhoea were common during weeks 1-2 and about 25% of the patients also developed primarily mild, self-limited increases in concentrations of aspartate aminotransferase and creatinine and/or blood urea nitrogen. At a 6-month follow-up, all 44 patients apparently cured at day 28 were considered complete responders (definitive cures), including the six treated for only 7-17 days. These results indicate that 100 mg miltefosine/day for 28 days is a promising oral-treatment regimen for VL cases, including those with antimony-unresponsive infections.

Kala-azar as an AIDS-related opportunistic infection

Visceral leishmaniasis (kala-azar) is a worldwide disseminated protozoal infection primarily transmitted by sand flies. Because host defense against this intracellular infection is T-cell-dependent, kala-azar has predictably joined the list of AIDS-related opportunistic infections in endemic areas. The vast majority of patients with AIDS-associated kala-azar are currently found in southern Europe (the Mediterranean basin, especially Spain in injection drug users); future cases will inevitably arise in other endemic regions including India, East Africa and Sudan, and Brazil. In CD4 cell-deficient HIV-infected individuals, kala-azar likely represents recrudescence of previously controlled asymptomatic infection; in drug users, newly acquired infection may result from transmission via shared needles. Coinfected patients are frequently parasitemic and may show atypical clinical presentations, unusual multi-organ involvement, and absent antileishmanial antibodies. Diagnosis is made by microscopic examination or culture of aspirate or biopsy of any involved tissue (primarily bone marrow) or by blood smear or culture. Conventional treatment (pentavalent antimonials) induces initial remission in about 50% of patients; amphotericin B and its new lipid formulations appear more active. If suppressive maintenance therapy is not used, relapse within 1 year is typical. In AIDS patients with a first episode of visceral kala-azar, up to 25% die within 1 month if treatment is stopped. Optimal primary and secondary prophylaxis for AIDS-related kala-azar remain to be determined; life-long maintenance therapy is becoming an accepted approach.

Treatment of idiopathic CD4 T lymphocytopenia with IL-2

Idiopathic CD4 T lymphocytopenia (ICL) is an unusual immune defect in which there is an unexplained deficit of CD4 T cells, leading to fungal, parasitic or other serious opportunistic infections. Current treatment efforts are directed at eliminating infections. Here we describe the use of a novel treatment, subcutaneous polyethylene glycol (PEG)-IL-2 injections, in a woman with this disorder, who had chronic severe mycobacterial disease which led to repeated hospitalizations, and advancing respiratory insufficiency. For this patient, PEG-IL-2, 50 000 U/m2, has been given by weekly subcutaneous injections for 5.5 years. This treatment has resulted in marked (and still continuing) long-term immunological improvement with normalized T cell functions and increased CD4 cell numbers. She has had substantial clinical improvement with clearing of mycobacterial disease, reducing hospitalizations and improved lung functions. The improvement seen in this patient suggests that low-dose IL-2 is a safe and practical therapy, which might be useful in other subjects with this potentially serious immune defect.

Macrophage microbicidal mechanisms in vivo: reactive nitrogen versus oxygen intermediates in the killing of intracellular visceral Leishmania donovani

To determine the relative contributions of respiratory burst-derived reactive oxygen intermediates (ROI) versus reactive nitrogen intermediates (RNI) to macrophage-mediated intracellular host defense, mice genetically deficient in these mechanisms were challenged with Leishmania donovani, a protozoan that selectively parasitizes visceral tissue macrophages. During the early stage of liver infection at wk 2, both respiratory burst-deficient gp91(phox)-/- (X-linked chronic granulomatous disease [X-CGD]) mice and inducible nitric oxide synthase (iNOS) knockout (KO) mice displayed comparably increased susceptibility. Thereafter, infection was unrestrained in mice lacking iNOS but was fully controlled in X-CGD mice. Mononuclear cell influx into infected liver foci in X-CGD and iNOS KO mice was also overtly impaired at wk 2. However, granuloma assembly in parasitized tissue eventually developed in both hosts but with divergent effects: mature granulomas were functionally active (leishmanicidal) in X-CGD mice but inert in iNOS-deficient animals. These results suggest that (a) ROI and RNI probably act together in the early stage of intracellular infection to regulate both tissue recruitment of mononuclear inflammatory cells and the initial extent of microbial replication, (b) RNI alone are necessary and sufficient for eventual control of visceral infection, and (c) although mature granulomas have traditionally been associated with control of such infections, these structures fail to limit intracellular parasite replication in the absence of iNOS.

Amphotericin B lipid complex in the management of antimony unresponsive Indian visceral leishmaniasis

Fifty-eight Indian patients with visceral leishmaniasis who did not respond or relapsed after 30 days of consecutive sodium stibogluconate therapy were randomised to treatment with amphotericin B lipid complex (ABLC) using a total dose of 7.5 or 10 mg/kg. Treatment induced a prompt clinical response in all patients with resolution of fever and regression in spleen size. Fever and chills developed during ABLC infusion, but it diminished with successive infusions. Fourteen days after treatment, 26 of 28 (93%) patients in the 7.5 mg/kg group and all 30 (100%) in the 10 mg/kg group had splenic aspirate parasite density scores of 0 and were considered apparent clinical and parasitologic responders. Four and three patients in the 7.5 and 10 mg/kg groups respectively relapsed during six months of followup; thus, overall 22 of 28 (79%) patients treated with 7.5 mg/kg and 27 of 30 (90%) treated with 10 mg/kg were definitive cures. All initial non-responders and relapses were retreated successfully with higher dose of ABLC. These results confirm the efficacy of short-course ABLC therapy for antimony-unresponsive Indian patients with visceral leishmaniasis. Since treatment with a total dose of 7.5 mg/kg did not appear to increase efficacy (79% vs. 84% induced by 5 mg/kg in a prior study), initial treatment with a total dose of 5 mg/kg followed by retreatment of any non-responders represents a potentially less costly approach in patients who fail antimony therapy. Though high cure rates are achieved with > or = 10 mg/kg total dose of ABLC, treatment using lower doses with retreatment of non-responders or relapses with higher dose can result in considerable savings.

Trial of oral miltefosine for visceral leishmaniasis

BACKGROUND

There is no effective oral treatment for visceral leishmaniasis (kala-azar), a disseminated intracellular protozoal infection that occurs worldwide. Miltefosine, an alkyl phospholipid developed as an oral antineoplastic agent, is active against visceral infection in animal models. We tested safety, tolerance, and efficacy of miltefosine in kala-azar.

METHODS

Oral doses of miltefosine were given to six groups of five Indian men for 28 days: 50 mg every second day (group 1), 100 mg every second day (group 2), 100 mg/day (group 3), 150 mg/day (group 4), 200 mg/day (group 5), and 250 mg/day (group 6). Assessment for apparent cure--taken as an afebrile state with decreased spleen size and a splenic-aspirate parasite-density score of 0--was done on days 14 and 28. Definitive cure at 8 months required a parasite-free bone-marrow aspirate and no clinical evidence of relapse.

FINDINGS

21 of 30 patients were apparently cured on day 14. Transient episodes of vomiting and diarrhoea, were common during weeks 1-2 and were seen in 22 patients. Four other patients in groups 5 and 6 had miltefosine withdrawn after 7-10 days because of vomiting. One patient in group 6 developed renal insufficiency and severe diarrhoea and died on day 21. On day 28, all 29 remaining patients were apparently cured. By 8 months, seven of ten patients in groups 1 and 2 had relapsed; however, 18 of 19 patients treated daily (groups 3-6) appeared to be cured. Among the 21 definitive cures were the four patients treated for 10 days or less and 12 for whom previous therapy with pentavalent antimony had failed.

INTERPRETATION

Treatment with miltefosine at 100-150 mg/day for 4 weeks has promise as an effective oral treatment of visceral leishmaniasis including antimony-resistant infection.

Treatment of antimony-unresponsive Indian visceral leishmaniasis with ultra-short courses of amphotericin-B-lipid complex

High cost is the principal drawback of treating visceral leishmaniasis (VL; kala-azar) with any of the new lipid formulations of amphotericin B. The aim of the present study was to see if the costs of treatment with such drugs could be reduced by using ultra-short courses. Amphotericin-B-lipid complex (ABLC) was given to 77 Indian patients with antimony-unresponsive VL, either as a single infusion of 5 mg/kg (Group A) or two infusions, each of 5 mg/kg, given 5 days apart (Group B) or on consecutive days (Group C). Other than the anticipated higher fever and chills, treatment was well-tolerated. On day 19 after first infusion, 72 patients were considered apparent cures: 24 (89%) of the 27 in Group A; all 24 (100%) in Group B; and 24 (92%) of the 26 patients in Group C. Six months after treatment, 19 (70%) of 27 in Group A, 19 (79%) of 24 in Group B, and 21 (81%) of 26 in Group C were healthy, relapse-free and considered definitive cures. These cure rates were not statistically different. All 18 treatment failures (five initial non-responders and 13 relapses) were cured after treatment with a 5-day course of ABLC at a higher dose (10-15 mg/kg.day). In a related analysis of hospital plus drug costs for treating antimony-unresponsive VL, short-course ABLC (1-5 days) was compared with conventional amphotericin B (0.75-1.0 mg/kg on alternate days over 30-34 days). This analysis, which included the cost of re-treatment, identified one short-course ABLC regimen with an overall estimated expense which was only modestly higher than that of amphotericin B. Together, the present results provide further support for the use of ABLC in the management of VL patients who fail antimony therapy.

Therapeutic effect of interferon-gamma gene transfer in experimental visceral leishmaniasis

Interferon (IFN)-gamma, in both natural endogenous form and administered as exogenous protein, induces control over visceral Leishmania donovani in experimentally infected BALB/c mice. To further characterize the therapeutic role of IFN-gamma in host defense against intracellular L. donovani, the efficacy of IFN-gamma delivered by gene transfer was tested. One week after infection, normal and IFN-gamma gene-disrupted (GKO) BALB/c mice were injected with an IFN-gamma gene-bearing mammalian expression plasmid (pIFN). Plasmid-specific IFN-gamma transcripts were detected in liver and spleen. Whereas liver parasite burdens more than doubled in untreated and mock-treated normal and GKO mice during the subsequent 2 weeks, animals injected with pIFN had controlled visceral infection and reduced parasite burden. These results indicate that, in infected tissues, IFN-gamma delivered by gene transfer enhances control over disseminated intracellular infection.

A cluster of cases of severe cardiotoxicity among kala-azar patients treated with a high-osmolarity lot of sodium antimony gluconate

In India, sodium antimony gluconate is the drug of choice for kala-azar. Due to increasing unresponsiveness to this drug in the current epidemic that began in the early 1970s, daily doses of 20 mg/kg/day for 30 days or more is recommended as opposed to the 10 mg/kg/day dose for 6-10 days used in the past. Of the 130-150 patients treated annually at our center with locally made sodium antimony gluconate, serious cardiotoxicity has occurred in less than 10%. During April 1995 at the University Hospital in Varanasi, we encountered life-threatening cardiotoxicity after 3-28 days of therapy in each of the eight patients being treated with a new lot of this drug made by a different manufacturer. Of the eight patients, six each developed congestive heart failure and/or prolongation of the corrected QT interval (QTc), and three died as a direct consequence of drug-induced toxicities. In three instances, the life-threatening complications occurred with a cumulative dose of less than 300 mg/kg. In patients with prolonged QTc, ventricular premature beats and ventricular tachycardia were recorded; in one patient, the ventricular tachycardia progressed to torsade de pointes, culminating in ventricular fibrillation and death. Since switching to different lots of this drug, we have not seen further clustering of dangerous cardiotoxicity. The antimony content of the implicated drug was comparable with that in lots from other manufacturers that did not show overt toxicity, but the osmolarity was approximately 300 mOsm/L higher. The simple technique of measuring of osmolarity may help identify inappropriately manufactured drug.

Splenic cytokine responses in Indian kala-azar before and after treatment

Cytokine mRNA levels were measured in serial splenic aspirates from 27 patients with visceral leishmaniasis during monotherapy with interferon-gamma (IFN-gamma; n = 9), sodium antimony gluconate (SAG; n = 8), or amphotericin B lipid complex (ABLC; n = 10). At baseline, mRNA for IFN-gamma was detected in 18 (86%) of 21 patients, and mRNA for interleukin (IL)-10 and IL-4 was detected in 21 (100%) and 10 (48%) of 21 patients, respectively. With IFN-gamma treatment alone, levels of IFN-gamma mRNA decreased by day 10 and then returned to baseline levels; IL-10 mRNA levels were high throughout treatment. In the SAG and ABLC groups, levels of IFN-gamma and IL-10 mRNA decreased significantly. Polarized Th2 cell type responses do not appear to develop in Indian kala-azar; instead, there is an initial mixed Th1-Th2 cell picture. With successful treatment and resolution of infection, both components of the immune response appear to involute.

Rapid accurate field diagnosis of Indian visceral leishmaniasis

BACKGROUND

A firm diagnosis of visceral leishmaniasis (kala-azar) requires demonstration of the parasite in organ aspirates or tissue biopsy samples. The aim of this prospective study was to assess the diagnostic usefulness of non-invasive testing for antibody to the leishmanial antigen K39 by means of antigen-impregnated nitrocellulose paper strips adapted for use under field conditions.

METHODS

One drop of peripheral blood is applied to the hitrocellulose strip. Three drops of test buffer (phosphate-buffered saline plus bovine serum albumin) are added to the dried blood. The development of two visible bands indicates presence of IgG anti-K39. 323 consecutive patients with suspected kala-azar referred to two specialist units in India, and 25 healthy controls, provided fingerstick blood samples for the test. Spleen aspirates were taken from 250 patients.

FINDINGS

Kala-azar was confirmed by microscopy of spleen-aspirate smears in 127 patients. The K39 strip test was positive in all 127; the estimated sensitivity was therefore 100% (95% CI 98-100). Four patients had positive strip tests but negative aspirate smears; all four responded to treatment for leishmaniasis. 217 individuals, including the 25 healthy controls, 73 patients with malaria or tuberculosis, and 119 spleen-aspirate-negative patients who had presumed malaria or cirrhosis (79) or no final diagnosis (40), had negative strip-test results. None of the 119 aspirate-negative patients developed evidence of kala-azar during 3-6 months of follow-up. The estimated specificity of the strip test was 98% (95-100; 217/221).

INTERPRETATION

Detection of anti-K39 by immunochromatographic strip testing is a rapid and non-invasive method of diagnosing kala-azar, which has good sensitivity and specificity and is well suited for use in field conditions.

Response to interferon-gamma plus pentavalent antimony in Indian visceral leishmaniasis

One hundred fifty-six previously untreated Indian patients with visceral leishmaniasis were treated with pentavalent antimony (Sb) alone for 30 days (group A), Sb plus interferon-gamma (IFN-gamma) for 30 days (group B), or Sb plus IFN-gamma for 15 days (group C). The purpose was to show that IFN-gamma would increase the response to 30 days of Sb treatment and that short-course (15 days) combination therapy was as effective as 30 days of Sb alone. Six months after treatment, 36% of group A, 49% of group B, and 42% of group C patients were designated as definitively cured. The success rates for long-term responses to Sb alone (36%) and Sb plus IFN-gamma (49%) were unexpectedly low, and responses in groups A, B, and C were not significantly different. These results suggest that the beneficial effects of adjunctive IFN-gamma in visceral leishmaniasis may be limited in regions where this disseminated intracellular infection shows high-level resistance to Sb.

Short-course, low-dose amphotericin B lipid complex therapy for visceral leishmaniasis unresponsive to antimony

BACKGROUND

Visceral leishmaniasis (kala-azar) is a worldwide, disseminated intracellular protozoal infection for which prolonged, conventional therapy with pentavalent antimony has become increasingly less effective.

OBJECTIVE

To determine the efficacy and minimal effective dose of short-course therapy with amphotericin B lipid complex in visceral leishmaniasis.

DESIGN

A randomized, open-label study.

SETTING

Inpatient kala-azar treatment unit in the state of Bihar in northeast India, where visceral leishmaniasis is endemic.

PATIENTS

60 patients with active infection who had not responded to or who had relapse after receiving conventional (> 30 days) treatment with pentavalent antimony.

INTERVENTION

Intravenous amphotericin B lipid complex was given once daily for 5 consecutive days by 2-hour infusion. Patients were randomly assigned to receive 1, 2, or 3 mg/kg of body weight per day (total doses of 5, 10, or 15 mg/kg, respectively).

MEASUREMENTS

Clinical and parasitologic responses (the latter were measured by parasite density score of the splenic aspirate) were determined 14 days after treatment. Definitive responses were assessed 6 months after treatment according to clinical outcomes and findings on examination of bone marrow aspirate.

RESULTS

All 60 patients responded to 5 days of treatment. Fourteen days after therapy, all patients had parasite-free splenic aspirates and were considered to have an apparent clinical and parasitologic response. Six months after therapy, definitive responses were documented in 16 of 19 (84% [95% Cl, 60% to 97%]), 18 of 20 (90% [Cl, 68% to 99%]), and 21 of 21 (100% [Cl, 84% to 100%]) patients who received total doses of 5, 10, and 15 mg/kg, respectively.

CONCLUSION

Short-course therapy with low-dose amphotericin B lipid complex is effective for visceral leishmaniasis and is an important therapeutic alternative in the management of this serious intracellular protozoal infection.

Endogenous interleukin-12 regulates acquired resistance in experimental visceral leishmaniasis

Treatment with interleukin-12 (IL-12) induces leishmanicidal activity in experimental Leishmania donovani infection; therefore, BALB/c mice were injected with anti-IL-12 antibody to define the role of endogenous IL-12 in acquired resistance in this disseminated intracellular infection. Anti-IL-12 administration started 1 day after infection and given for 4 weeks abolished control of visceral parasite replication and in parallel suppressed endogenous interferon-gamma production and tissue granuloma assembly. Early (during week 1 only) and delayed treatment (during weeks 2-4 only) with anti-IL-12 also exacerbated visceral infection at week 4. These results point to a central role for endogenous IL-12 in acquired resistance to intracellular L. donovani and suggest that IL-12 is active in the cell-mediated immune response beyond the initial stage of host-parasite interaction.

Circulating T helper 1 (Th1) cell- and Th2 cell-associated cytokines in Indian patients with visceral leishmaniasis

Sera from 61 Indian patients with visceral leishmaniasis caused by infection with Leishmania donovani were tested for the presence of T helper 1 (Th1) cell-(interferon-gamma [IFN-gamma]) and Th2 cell-associated cytokines (interleukin-4 [IL-4] and IL-10). The IFN-gamma activity was detected in 53%. IL-4 in 84%, and IL-10 in 56% of patient samples. Sera from 10 healthy Indian controls showed detectable IFN-gamma in 90%. IL-4 in 10%, and IL-10 in 20%; corresponding percentages for sera from eight healthy American controls were 100%, 12%, and 0%, respectively. Quantitative data for the 61 patients compared with the 10 Indian controls indicated comparable mean levels of IFN-gamma, but three- and 13-fold increases in IL-10 and IL-4, respectively. Undetectable IFN-gamma activity, observed in 47% of patients, was associated with the presence IL-4 alone or in combination with IL-10 but not with IL-10 alone. In patients who had failed prior therapy (n = 29) compared with previously untreated patients (n = 32). IFN-gamma levels were 67% lower and IL-4 levels were two-fold higher, IL-10 activity was comparable. These results using peripheral blood support the presence of a suppressive Th2 cell-associated immune response in symptomatic Indian kala-azar and point to a possible role for IL-4.

Kala-azar comes to New York

Visceral leishmaniasis (kala-azar) is a disseminated protozoal infection that occurs in areas of the world other than North America. In endemic regions, kala-azar is also an opportunistic infection associated with the acquired immunodeficiency syndrome. We report a case of acquired immunodeficiency syndrome-associated kala-azar acquired abroad that was first expressed in New York City. Human immunodeficiency virus-infected patients who have lived or traveled abroad may present in this country with unusual infections.

Intracellular antimicrobial activity in the absence of interferon-gamma: effect of interleukin-12 in experimental visceral leishmaniasis in interferon-gamma gene-disrupted mice

Despite permitting uncontrolled intracellular visceral infection for 8 wk, interferon-gamma (IFN-gamma) gene knockout (GKO) mice infected with Leishmania donovani proceeded to reduce liver parasite burdens by 50% by week 12. This late-developing IFN-gamma-independent antileishmanial mechanism appeared to be dependent largely on endogenous tumor necrosis factor-alpha (TNF-alpha): L. donovani infection induced TNF-alpha mRNA expression in parasitized GKO livers and neutralization of TNF-alpha reversed control at week 12.7 d of treatment of infected GKO mice with interleukin-12 (IL-12) readily induced leishmanicidal activity and also partially restored the near-absent tissue granulomatous response, observations that for the first time expand the antimicrobial repertoire of IL-12 to include IFN-gamma-independent effects. The action of IL-12 against L. donovani was TNF-alpha dependent and required the activity of inducible nitric oxide synthase. These results point to the presence of an IFN-gamma-independent antimicrobial mechanism, mediated by TNF-alpha, which remains quiescent until activated late in the course of experimental visceral leishmaniasis. However, as judged by the effect of exogenous IL-12 this quiescent mechanism can readily be induced to rapidly yield enhanced intracellular antimicrobial activity.

Behavior of visceral Leishmania donovani in an experimentally induced T helper cell 2 (Th2)-associated response model

Although implicated in the clinical expression of human visceral leishmaniasis, a disease-exacerbating T helper cell 2 (Th2)-associated immune response involving interleukin-4 (IL-4) and/ or IL-10 is not readily detectable in experimental visceral infection. To overcome this obstacle to analyzing visceral Leishmania donovani in this relevant immunopathogenetic environment, we sought a model in which a Th2 response induces noncuring infection. Four initial approaches were tested primarily in BALB/c mice which control intracellular L. donovani via an IL-12- and interferon-gamma (IFN-gamma)-dependent Th1 mechanism: (a) modifying the cytokine milieu when the parasite is first encountered (treatment with exogenous IL-4 or anti-IL-12), (b) providing sustained endogenous exposure to a Th2 cytokine (infection of IL-4 transgenic mice), (c) increasing the parasite challenge inoculum, and (d) injecting heat-killed L. major promastigotes (HKLMP) to induce a cross-reactive Th2 response to live L. donovani. Only the last approach generated a functional Th2-type response that induced disease exacerbation accompanied by inhibition of tissue granuloma assembly. In HKLMP-primed BALB/c mice, prophylaxis with anti-IL-4, anti-IL-10, or exogenous IL-12 (but not IFN-gamma) readily restored resistance. In primed mice with established visceral infection, treatment with either IL-12 or IFN-gamma also successfully induced antileishmanial activity. The results in this model (a) suggest that rather than acting alone, IL-4 and IL-10 may act in concert to prevent acquisition of resistance to L. donovani, (b) reemphasize the capacity of IL-12 to reverse early Th2-related effects, and (c) demonstrate that Th1 cytokines (IL-12, IFN-gamma) have therapeutic action in an established systemic infection despite the presence of a disease-exacerbating Th2-type response.

Delivery of human interferon-gamma via gene transfer in vitro: prolonged expression and induction of macrophage antimicrobial activity

Daily parenteral administration of exogenous interferon-gamma (IFN-gamma) induces or accelerates recovery in experimental and human infections. To develop an alternative delivery system, a replication-defective recombinant adenovirus expressing human IFN-gamma was constructed. The complete coding region of IFN-gamma was amplified by RT-PCR and inserted into an adenovirus cloning vector under the control of a human cytomegalovirus promoter. Recombinant adenovirus containing the IFN-gamma minigene (dAv-IFN-gamma) was isolated from 293 cells co-transfected with the linearized plasmid and an E1 region-deleted fragment of adenovirus genome. Following in vitro infection with dAv-IFN-gamma, dose-dependent and time-dependent expression of IFN-gamma, mRNA and production of soluble protein were demonstrated in human diploid fibroblat and HeLa cell cultures by Northern blot and ELISA, respectively. Extracellular protein secretion persisted for > = 4 weeks following initial transfection, and secreted IFN-gamma induced both antiviral activity (8000-25,000 U/ml) and macrophage activation with killing of intracellular Toxoplasma gondii and leishmania donovani. These results establish that dAv-IFN-gamma generates long-term secretion of biologically active IFN-gamma in vitro and suggest that this vector may be a useful delivery system for cytokine therapy.

Pentavalent antimony-mannan conjugate therapy of experimental visceral leishmaniasis

Pentavalent antimony-mannan (Sb[V]-mannan) was 10-fold more potent than sodium stibogluconate in a murine model of visceral leishmaniasis. Liver antimony concentrations were six-fold higher after Sb[V]-mannan therapy compared with a dose of sodium stibogluconate that was equipotent in reducing liver parasite burdens. Murine toxicity of Sb[V]-mannan was variable, with a 50% lethal dose (LD50) for one preparation that was well above the concentration that killed 90% of the parasites, and for another preparation was only modestly higher than the concentration that killed 90% of the parasites.

Current and future clinical applications of interferon-gamma in host antimicrobial defense

The T cell-derived macrophage-activating lymphokine, interferon-gamma (IFN-gamma), is the most broadly acting antimicrobial-inducing and host defense-enhancing cytokine thus far identified in experimental models of infectious diseases. The activity induced by IFN-gamma encompasses all classes of non-viral pathogens including intracellular and extracellular parasites, fungi and bacteria. In man, treatment with immuno-enhancing doses of IFN-gamma is safe, well-tolerated and stimulates the antimicrobial mechanisms of blood monocytes, circulating neutrophils and tissue macrophages. Aerosol administration activates alveolar macrophages in a compartmentalized fashion. Monocytes from IFN-gamma-treated patients with cancer, leprosy, and AIDS all respond with the activated phenotype, and suppressed monocyte HLA-DR expression in trauma patients can be up-regulated by IFN-gamma therapy. Thus far, IFN-gamma has been recognized as effective in the prophylaxis of chronic granulomatous disease and as adjunctive treatment in at least one systemic intracellular infection, visceral leishmaniasis. Additional trials suggest beneficial effects as prophylaxis in trauma and as treatment in leprosy, cutaneous leishmaniasis, and HIV- and non-HIV-related disseminated atypical mycobacterial infection. IFN-gamma is also being tested as a prophylaxis in patients with burns and advanced HIV infection and as an adjunct in drug-resistant tuberculosis. Future antimicrobial applications for IFN-gamma include: a) long-term prophylaxis in T cell-deficient states, b) short-term prophylaxis in patients with a reversible host defense defect such as granulocytopenia or immune response suppression induced by trauma or burn injury, and c) adjunctive treatment along with conventional antibiotic therapy for i) nosocomial pneumonia (aerosol administration), ii) opportunistic infections in general, iii) infections which typically respond poorly to available treatment and iv) for infections which require prolonged therapy for cure. In the latter, the addition of IFN-gamma may accelerate the response to conventional therapy and permit a clinically important reduction in the duration of treatment while preserving efficacy.

Induction of macrophage antiprotozoal activity by monocyte chemotactic and activating factor

To determine if monocyte chemotactic and activating factor (MCAF) induces intracellular antimicrobial activity, human monocyte-derived macrophages were treated with MCAF and challenged with Toxoplasma gondii and Leishmania donovani. Pretreatment with MCAF induced macrophages to inhibit protozoal replication by approximately 50%. These findings suggest a potential host defense role for MCAF in the inflammatory response to intracellular pathogens.

Models of relapse of experimental visceral leishmaniasis

To establish models for studying recurrence of visceral leishmaniasis, a growing problem in T cell-deficient patients, two approaches were investigated: treatment of euthymic BALB/c mice with quiescent Leishmania donovani infection with T cell-depleting or anti-cytokine antibodies and serial observation of acutely infected nude BALB/c mice after an initial antileishmanial response induced by amphotericin B treatment. In chronically infected euthymic mice, maintenance of acquired immunity and prevention of relapse required CD4 cells and a multicytokine-dependent mechanism involving endogenous interleukin-2, interferon-gamma, and tumor necrosis factor-alpha. Acutely infected nude mice responded to amphotericin B with a > or = 85% reduction in liver parasite burdens; however, after a brief lag, visceral infection readily recurred in the posttreatment period. Both models may be useful for testing experimental interventions designed to reduce relapse of previously controlled visceral leishmaniasis in T cell-deficient hosts.

Activity of oral atovaquone alone and in combination with antimony in experimental visceral leishmaniasis

BALB/c mice with established visceral infection caused by the intracellular protozoan Leishmania donovani were treated with oral atovaquone for 7 days. Treatment with 100 mg/kg of body weight per day was optimal and halted parasite replication in the liver. In mice treated with atovaquone, the effect of a suboptimal dose of pentavalent antimony was converted from partially leishmanistatic to leishmanicidal. These results demonstrate the in vivo antileishmanial effect of atovaquone and suggest a potential role for this oral agent in visceral leishmaniasis as an adjunct to conventional antimony treatment.

Cure of antimony-unresponsive Indian visceral leishmaniasis with amphotericin B lipid complex

Twenty-one Indian patients with visceral leishmaniasis who did not respond to or relapsed after 28-60 days of pentavalent antimony therapy were treated with amphotericin B lipid complex (ABLC). Five infusions (3 mg/kg each) given every second day over 9 days (total dose, 15 mg/kg) resulted in a 100% apparent cure response. In 4 other patients who had not responded to antimony, apparent cure was also induced by ABLC given 3 mg/kg a day 5 consecutive days (total dose, 15 mg/kg). Fever and chills developed routinely during the initial 2-h infusions; these reactions were tolerated and diminished with successive infusions. Six months after treatment, all 25 patients were healthy, had parasite-free bone marrow aspirates, and were considered cured. ABLC is effective short-course therapy for kala-azar patients who do not respond to conventional antimony treatment.

Multiple host defense defects in failure of C57BL/6 ep/ep (pale ear) mice to resolve visceral Leishmania donovani infection

Euthymic C57BL/L ep/ep (pale ear [PE]) mice halt the visceral replication of intracellular Leishmania donovani but fail to properly resolve infection. A previous study identified an isolated defect in tissue granuloma formation in these mice; CD4+ and CD8+ cell number, gamma interferon (IFN-gamma) production, and macrophage antimicrobial activity in vitro were all intact. New in vivo results reported here suggest a considerably more complex immune defect, with evidence indicating (i) enhanced control over L. donovani after transfer of normal C57BL/6 spleen cells, (ii) a partially suppressive Th2 cell-associated response mediated by interleukin-4 (IL-4) but not reversed by CD4+ cell depletion, (iii) absent responses to endogenous Th1 cell lymphokines (IFN-gamma and IL-2) but preserved responsiveness to endogenous tumor necrosis factor alpha, (iv) absent responses to exogenous treatment with recognized antileishmanial cytokines (IFN-gamma, IL-2, IL-12, and granulocyte-macrophage colony-stimulating factor [GM-CSF]) not corrected by transfer of C57BL/6 spleen cells, and (v) a deficient response to antimony chemotherapy. Defective hepatic granuloma formation was not corrected by transfer of C57BL/6 spleen cells or by anti-IL-4 administration. While treatment with IL-2 and GM-CSF modified the tissue reaction and induced selected effector cells to encase tissue macrophages, no antileishmanial activity resulted. Together, these observations suggest that the failure of PE mice to resolve visceral L. donovani infection likely represents expression of multiple suboptimal immune responses and/or partial defects, probably involving a combination of T-cell dysfunction, a Th2 cell response, and target cell (macrophage) hyporesponsiveness.

Effect of treatment with interferon-gamma alone in visceral leishmaniasis

Interferon-gamma (IFN-gamma) enhances the therapeutic response to pentavalent antimony in patients with visceral leishmaniasis. To determine the effect of cytokine immunotherapy alone, 9 patients with kala-azar were treated with IFN-gamma before receiving antimony. After 20 days of IFN-gamma therapy, 4 patients showed no parasitologic response; in the remaining 5 patients, however, splenic aspirate parasite scores declined from 4.2 +/- 0.2 to 1.2 +/- 0.5 (mean +/- SE). These results indicate that treatment with IFN-gamma alone can induce visceral antileishmanial activity. However, the limited efficacy in this uncontrolled pilot trial suggests that the therapeutic role of IFN-gamma in kala-azar is that of an adjunct to conventional antimony treatment.