The therapeutic effect of sodium stibogluconate in BALB/c mice infected with Leishmania donovani is organ-dependent

Supramolecular assemblies from antimony(V) complexes for the treatment of leishmaniasis

The pentavalent meglumine antimoniate (MA) is still a first-line drug in the treatment of leishmaniasis in several countries. As an attempt to elucidate its mechanism of action and develop new antimonial drugs with improved therapeutic profile, Sb(V) complexes with different ligands, including β-cyclodextrin (β-CD), nucleosides and non-ionic surfactants, have been studied. Interestingly, Sb(V) oxide, MA, its complex with β-CD, Sb(V)-guanosine complex and amphiphilic Sb(V) complexes with N-alkyl-N-methylglucamide, have shown marked tendency to self-assemble in aqueous solutions, forming nanoaggregates, hydrogel or micelle-like nanoparticles. Surprisingly, the resulting assemblies presented in most cases slow dissociation kinetics upon dilution and a strong influence of pH, which impacted on their pharmacokinetic and therapeutic properties against leishmaniasis. To explain this unique property, we raised the hypothesis that multiple pnictogen bonds could contribute to the formation of these assemblies and their kinetic of dissociation. The present article reviews our current knowledge on the structural organization and physicochemical characteristics of Sb-based supramolecular assemblies, as well as their pharmacological properties and potential for treatment of leishmaniasis. This review supports the feasibility of the rational design of new Sb(V) complexes with supramolecular assemblies for the safe and effective treatment of leishmaniasis.

Immunisation with Transgenic L. tarentolae Expressing Gamma Glutamyl Cysteine Synthetase from Pathogenic Leishmania Species Protected against L. major and L. donovani Infection in a Murine Model

Leishmaniasis is a protozoan disease responsible for significant morbidity and mortality. There is no recommended vaccine to protect against infection. In this study, transgenic Leishmania tarentolae expressing gamma glutamyl cysteine synthetase (γGCS) from three pathogenic species were produced and their ability to protect against infection determined using models of cutaneous and visceral leishmaniasis. The ability of IL-2-producing PODS^® to act as an adjuvant was also determined in L. donovani studies. Two doses of the live vaccine caused a significant reduction in L. major (p < 0.001) and L. donovani (p < 0.05) parasite burdens compared to their respective controls. In contrast, immunisation with wild type L. tarentolae, using the same immunisation protocol, had no effect on parasite burdens compared to infection controls. Joint treatment with IL-2-producing PODS^® enhanced the protective effect of the live vaccine in L. donovani studies. Protection was associated with a Th1 response in L. major and a mixed Th1/Th2 response in L. donovani, based on specific IgG1 and IgG2a antibody and cytokine production from in vitro proliferation assays using antigen-stimulated splenocytes. The results of this study provide further proof that γGCS should be considered a candidate vaccine for leishmaniasis.

Emetic Tartar-Loaded Liposomes as a New Strategy for Leishmaniasis Treatment

Emetic tartar (ET), was used in the treatment of leishmaniasis but its use was discontinued due to its low therapeutic index. Liposomes have been shown to be a promising strategy for delivery of bioactive substances in the region of interest, in order to reduce and/or eliminate undesirable effects. In the present study, liposomes containing ET were prepared and characterized to evaluate acute toxicity as well as their leishmanicidal action using BALB/c mice with an inoculum of Leishmania (Leishmania) infantum. Liposomes were composed of egg phosphatidylcholine and 3ß-[N-(N′,N′-dimethylaminoethane)-carbamoyl]cholesterol, with an average diameter of 200 nm, zeta potential of +18 mV, and ET encapsulated into liposomes at a concentration near 2 g/L. Healthy mice were treated with ET or liposome containing ET (Lip-ET) in a single dose of 16 mg/kg of Sb3+ intravenously and observed for 14 days. The death of two animals in the ET-treated group and no deaths in the Lip-ET-treated group was observed. Higher hepatic and cardiac toxicity were observed in animals treated with ET when compared to animals treated with Lip-ET, blank liposomes (Blank-Lip) and PBS. The study of antileishmanial efficacy was conducted by intraperitoneal administration of Lip-ET, for ten consecutive days. It was observed by limiting dilution that treatments with liposomal formulations containing ET, as well as Glucantime®, led to a significant reduction in parasitic load in spleen and liver (p < 0.05) when compared to the untreated control group.

A new oral self-emulsifying drug delivery system improves the antileishmania efficacy of fexinidazole in vivo

The aim of this study was to develop, characterize and evaluate the in vivo oral efficacy of self-emulsifying drug delivery systems (SEDDS) containing fexinidazole (FEX) in the experimental treatment of visceral leishmaniasis (VL). The developed FEX-SEDDS formulation presented as a clear, yellowish liquid, with absence of precipitate. The droplet size, polydispersion index and zeta potential after dilution in water (1:200) was of 91 ± 3 nm, 0.242 ± 0.005 and -16.7 ± 0.2, respectively. In the simulated gastric and intestinal media, the FEX-SEDDS had a size of 97 ± 1 and 106 ± 9 nm, respectively. The FEX retention in droplet after SEDDS dilution in simulated gastrointestinal media was almost 100 %. Antileishmanial efficacy studies showed that FEX-SEDDS was the only treatment able to significantly (p < 0.05) reduce the parasite burden in the liver and spleen of animals experimentally infected with Leishmania infantum. Our intestinal permeability data suggest that FEX-SEDDS showed no evidence of injury to the intestinal mucosa. These findings suggest that FEX-SEDDS can be a promising oral alternative for the treatment of VL caused by L. infantum.

LEISH2b - A phase 2b study to assess the safety, efficacy, and immunogenicity of the Leishmania vaccine ChAd63-KH in post-kala azar dermal leishmaniasis

Background: The leishmaniases are neglected tropical diseases caused by various Leishmania parasite species transmitted by sand flies. They comprise a number of systemic and cutaneous syndromes including kala-azar (visceral leishmaniasis, VL), cutaneous leishmaniasis (CL), and post-kala-azar dermal leishmaniasis (PKDL). The leishmaniases cause significant mortality (estimated 20 - 50,000 deaths annually), morbidity, psychological sequelae, and healthcare and societal costs. Treatment modalities remain difficult. E.g., East African PKDL requires 20 days of intravenous therapy, and frequently relapsing VL is seen in the setting of HIV and immunodeficiency. We developed a new therapeutic vaccine, ChAd63-KH for VL / CL / PKDL and showed it to be safe and immunogenic in a phase 1 trial in the UK, and in a phase 2a trial in PKDL patients in Sudan.    Methods: This is a randomised double-blind placebo-controlled phase 2b trial to assess the therapeutic efficacy and safety of ChAd63-KH in patients with persistent PKDL in Sudan. 100 participants will be randomly assigned 1:1 to receive placebo or ChAd63-KH (7.5 x10 10vp i.m.) at a single time point. Follow up is for 120 days after dosing and we will compare the clinical evolution of PKDL, as well as the humoral and cellular immune responses between the two arms. Discussion: Successful development of a therapeutic vaccine for leishmaniasis would have wide-ranging direct and indirect healthcare benefits that could be realized rapidly. For PKDL patients, an effective therapeutic vaccination used alone   would have very significant clinical value, reducing the need for extensive hospitalization and chemotherapy. Combining vaccine with drug (immuno-chemotherapy) might significantly increase the effective life of new drugs, with lower dose / abbreviated regimens helping to limit the emergence of drug resistance. If therapeutic benefit of ChAd63-KH can be shown in PKDL further evaluation of the vaccine in other forms of leishmaniasis should be considered. Clinicaltrials.gov registration: NCT03969134.

Antileishmanial efficacy and tolerability of combined treatment with non-ionic surfactant vesicle formulations of sodium stibogluconate and paromomycin in dogs

Infection with Leishmania infantum causes the disease visceral leishmaniasis (VL), which is a serious clinical and veterinary problem. The drugs used to treat canine leishmaniasis (CanL) do not cause complete parasite clearance; they can be toxic, and emerging drug resistance in parasite populations limits their clinical utility. Therefore, in this study we have evaluated the toxicity and efficacy of joint treatment with a 1:1 mixture of sodium stibogluconate-NIV (SSG-NIV, 10 mg Sb^v/day) and paromomycin-NIV (PMM-NIV, 10 mg PMM/kg/day), given intravenously daily for seven days from day 270 post-infection, to nine-month-old female beagle dogs (n = 6) experimentally infected with Leishmania infantum. Treatment significantly improved the clinical symptoms of VL infection in all the treated dogs, reduced parasite burdens in lymph nodes and bone marrow, and all symptomatic treated dogs, were asymptomatic at 90 days post-treatment. Treatment was associated with a progressive and significant decrease in specific IgG anti-Leishmania antibodies using parasite soluble antigen (p < 0.01) or rK39 (p < 0.01) as the target antigen. In addition, all dogs were classified as parasite negative based on Leishmania nested PCR and quantitative real time PCR tests and as well as an inability to culture of promastigote parasites from lymph nodes and bone marrow tissue samples taken at day 90 post-treatment. However, treatment did not cure the dogs as parasites were detected at 10 months post-treatment, indicating that a different dosing regimen is required to cause long term cure or prevent relapse.

Can We Harness Immune Responses to Improve Drug Treatment in Leishmaniasis?

Leishmaniasis is a vector-borne parasitic disease that has been neglected in priority for control and eradication of malaria, tuberculosis, and HIV/AIDS. Collectively, over one seventh of the world’s population is at risk of being infected with 0.7–1.2 million new infections reported annually. Clinical manifestations range from self-healing cutaneous lesions to fatal visceral disease. The first anti-leishmanial drugs were introduced in the 1950′s and, despite several shortcomings, remain the mainstay for treatment. Regardless of this and the steady increase in infections over the years, particularly among populations of low economic status, research on leishmaniasis remains under funded. This review looks at the drugs currently in clinical use and how they interact with the host immune response. Employing chemoimmunotherapeutic approaches may be one viable alternative to improve the efficacy of novel/existing drugs and extend their lifespan in clinical use.

Biodistribution of meglumine antimoniate in healthy and Leishmania (Leishmania) infantum chagasi-infected BALB/c mice

Pentavalent antimonials such as meglumine antimoniate (MA) are the primary treatments for leishmaniasis, a complex disease caused by protozoan parasites of the genus Leishmania . Despite over 70 years of clinical use, their mechanisms of action, toxicity and pharmacokinetics have not been fully elucidated. Radiotracer studies performed on animals have the potential to play a major role in pharmaceutical development. The aims of this study were to prepare an antimony radiotracer by neutron irradiation of MA and to determine the biodistribution of MA in healthy and Leishmania (Leishmania) infantum chagasi-infected mice. MA (Glucantime^(r)) was neutron irradiated inside the IEA-R1 nuclear reactor, producing two radioisotopes, 122Sb and 124Sb, with high radionuclidic purity and good specific activity. This irradiated compound presented anti-leishmanial activity similar to that of non-irradiated MA in both in vitro and in vivo evaluations. In the biodistribution studies, healthy mice showed higher uptake of antimony in the liver than infected mice and elimination occurred primarily through biliary excretion, with a small proportion of the drug excreted by the kidneys. The serum kinetic curve was bi-exponential, with two compartments: the central compartment and another compartment associated with drug excretion. Radiotracers, which can be easily produced by neutron irradiation, were demonstrated to be an interesting tool for answering several questions regarding antimonial pharmacokinetics and chemotherapy.

Cationic liposomal sodium stibogluconate (SSG), a potent therapeutic tool for treatment of infection by SSG-sensitive and -resistant Leishmania donovani

Pentavalent antimonials have been the first-line treatment for leishmaniasis for decades. However, the development of resistance to sodium stibogluconate (SSG) has limited its use, especially for treating visceral leishmaniasis (VL). The present work aims to optimize a cationic liposomal formulation of SSG for the treatment of both SSG-sensitive (AG83) and SSG-resistant (GE1F8R and CK1R) Leishmania donovani infections. Parasite killing was determined by the 3-(4,5-dimethylthiazol-2)-2,5-diphenyltetrazolium bromide (MTT) assay and microscopic counting of Giemsa-stained macrophages. Macrophage uptake studies were carried out by confocal microscopic imaging. Parasite-liposome interactions were visualized through transmission electron microscopy. Toxicity tests were performed using assay kits. Organ parasite burdens were determined by microscopic counting and limiting dilution assays. Cytokines were measured by enzyme-linked immunosorbent assays (ELISAs) and flow cytometry. Although all cationic liposomes studied demonstrated leishmanicidal activity, phosphatidylcholine (PC)-dimethyldioctadecylammonium bromide (DDAB) vesicles were most effective, followed by PC-stearylamine (SA) liposomes. Since entrapment of SSG in PC-DDAB liposomes demonstrated enhanced ultrastructural alterations in promastigotes, PC-DDAB-SSG vesicles were further investigated in vitro and in vivo. PC-DDAB-SSG could effectively alleviate SSG-sensitive and SSG-resistant L. donovani infections in the liver, spleen, and bone marrow of BALB/c mice at a dose of SSG (3 mg/kg body weight) not reported previously. The parasiticidal activity of these vesicles was attributed to better interactions with the parasite membranes, resulting in direct killing, and generation of a strong host-protective environment, necessitating a very low dose of SSG for effective cures.

Hepatotoxicity of pentavalent antimonial drug: possible role of residual Sb(III) and protective effect of ascorbic acid

Pentavalent antimonial drugs such as meglumine antimoniate (Glucantime [Glu; Sanofi-Aventis, São Paulo, Brazil]) produce severe side effects, including cardiotoxicity and hepatotoxicity, during the treatment of leishmaniasis. We evaluated the role of residual Sb(III) in the hepatotoxicity of meglumine antimoniate, as well as the protective effect of the antioxidant ascorbic acid (AA) during antimonial chemotherapy in a murine model of visceral leishmaniasis. BALB/c mice infected with Leishmania infantum were treated intraperitoneally at 80 mg of Sb/kg/day with commercial meglumine antimoniate (Glu) or a synthetic meglumine antimoniate with lower Sb(III) level (MA), in association or not with AA (15 mg/kg/day), for a 20-day period. Control groups received saline or saline plus AA. Livers were evaluated for hepatocytes histological alterations, peroxidase activity, and apoptosis. Increased proportions of swollen and apoptotic hepatocytes were observed in animals treated with Glu compared to animals treated with saline or MA. The peroxidase activity was also enhanced in the liver of animals that received Glu. Cotreatment with AA reduced the extent of histological changes, the apoptotic index, and the peroxidase activity to levels corresponding to the control group. Moreover, the association with AA did not affect the hepatic uptake of Sb and the ability of Glu to reduce the liver and spleen parasite loads in infected mice. In conclusion, our data supports the use of pentavalent antimonials with low residue of Sb(III) and the association of pentavalent antimonials with AA, as effective strategies to reduce side effects in antimonial therapy.

Therapeutic vaccination with recombinant adenovirus reduces splenic parasite burden in experimental visceral leishmaniasis

Therapeutic vaccines, when used alone or in combination therapy with antileishmanial drugs, may have an important place in the control of a variety of forms of human leishmaniasis. Here, we describe the development of an adenovirus-based vaccine (Ad5-KH) comprising a synthetic haspb gene linked to a kmp11 gene via a viral 2A sequence. In nonvaccinated Leishmania donovani–infected BALB/c mice, HASPB- and KMP11-specific CD8⁺ T cell responses were undetectable, although IgG1 and IgG2a antibodies were evident. After therapeutic vaccination, antibody responses were boosted, and IFNγ⁺CD8⁺ T cell responses, particularly to HASPB, became apparent. A single vaccination with Ad5-KH inhibited splenic parasite growth by ∼66%, a level of efficacy comparable to that observed in early stage testing of clinically approved antileishmanial drugs in this model. These studies indicate the usefulness of adenoviral vectors to deliver leishmanial antigens in a potent and host protective manner to animals with existing L. donovani infection.

Endogenous IL-13 plays a crucial role in liver granuloma maturation during Leishmania donovani infection, independent of IL-4Rα-responsive macrophages and neutrophils

Previous studies comparing interleukin 4 receptor α (IL-4Rα)^-/- and interleukin 4 (IL-4)^-/- BALB/c mice have indicated that interleukin 13 (IL-13), whose receptor shares the IL-4Rα subunit with IL-4, plays a protective role during visceral leishmaniasis. We demonstrate that IL-13^-/- BALB/c mice were less able to control hepatic growth of Leishmania donovani compared with wild-type mice. This correlated with significantly retarded granuloma maturation in IL-13^-/- mice, defective interferon γ (IFN-γ) production, and elevated IL-4 and interleukin 10 (IL-10) levels. L.donovani–infected IL-13^-/- mice also responded poorly to sodium stibogluconate-mediated chemotherapy compared with wild-type BALB/c mice. Because murine lymphocytes do not have IL-13 receptors, we examined the ability of macrophage/neutrophil-specific IL-4Rα^-/- mice to control primary infection with L. donovani and to respond to chemotherapy. Macrophage/neutrophil-specific IL-4Rα^-/- mice were as resistant to leishmaniasis as wild-type mice, and chemotherapy retained its efficacy. Consequently, in L. donovani infected BALB/c mice, IL-13 promotes hepatic granuloma formation and controls parasite burdens independently of direct effects on macrophages/neutrophils.

Leishmanial antigens in liposomes promote protective immunity and provide immunotherapy against visceral leishmaniasis via polarized Th1 response

Leishmaniasis affects 12 million people, and it is generally agreed that vaccination provides the best long-term strategy for its control. An ideal vaccine should be effective in both preventing and treating leishmaniasis. However, immunological correlates to predict vaccine efficacy and success of treatment in visceral leishmaniasis (VL) remain ill defined. Here, we correlated the vaccine efficacy of soluble leishmanial antigens (SLA) from Leishmania donovani promastigote membrane, entrapped in negative, neutral and positively charged liposomes with the elicited immune responses to predict vaccine success in experimental VL. Production of both IFN-gamma and IL-4 with a dominance of Th1 response following immunization was required for optimum success against L. donovani infection in BALB/c mice. The best vaccine formulation, SLA in positively charged liposomes, was then used for immunotherapy. This vaccine induced more than 90% elimination of parasites from both liver and spleen. The success of immunotherapy exhibited an immune modulation with surge in Th1 cytokines, IFN-gamma and IL-12 with extreme down regulation of disease promoting IL-4 and IL-10. These findings suggest that an immune modulation towards Th1 is effective for both successful vaccination and immunotherapy.

Endogenous interleukin-18 is involved in immunity to Leishmania donovani but its absence does not adversely influence the therapeutic activity of sodium stibogluconate

Immunity to Leishmania donovani is associated with an interleukin (IL)-12 driven T helper 1 (Th1) response. In addition, the ability to respond to chemotherapy with sodium stibogluconate (SSG) requires a fully competent immune response and both Th1 and Th2 responses have been shown to positively influence the outcome of drug treatment. In the present study, the influence of IL-18, which can modulate both interferon (IFN)-gamma and IL-4 production, on the outcome of primary L. donovani infection and SSG therapy following infection was assessed using BALB/c IL-18-deficient and wild type mice. IL-18 deficiency was associated with an increased susceptibility to L. donovani infection, evident by day 40 post infection, resulting in higher parasite burdens in the spleen, liver, and bone marrow compared with wild type control animals. Infected IL-18-deficient mice had significantly lower splenocyte concanavalin A (ConA) induced IFN-gamma production as well as lower serum IL-12 and IFN-gamma levels, indicating a reduced Th1 response. However, drug treatment was equally effective in both mouse strains and restored serum IL-12 and IFN-gamma levels, and IFN-gamma production by ConA stimulated splenocytes of IL-18-deficient mice, to levels equivalent to similarly treated wild type mice.

Resistance of Leishmania donovani to sodium stibogluconate is related to the expression of host and parasite gamma-glutamylcysteine synthetase

Sequencing studies showed that the gamma-glutamylcysteine synthetase (gamma-GCS) heavy chain genes from sodium stibogluconate (SSG)-resistant (SSG-R) and SSG-susceptible (SSG-S) Leishmania donovani strains were identical, indicating that SSG resistance was related to quantitative differences in gamma-GCS expression rather than gene interstrain polymorphisms. In vitro infection of murine macrophages with the SSG-R strain, but not the SSG-S strain, down regulated expression of host gamma-GCS, which would result in a reduction in intramacrophage glutathione (GSH) levels and promote an oxidative intramacrophage environment. This would inhibit, or minimize, the reduction of SSG pentavalent antimony to its more toxic trivalent form. Macrophage studies showed that the SSG-R strain expressed higher levels of gamma-GCS compared to the SSG-S strain, which would result in higher GSH levels, giving increased protection against oxidative stress and facilitating SSG efflux. However a similar differential effect on host and parasite gamma-GCS expression was not obtained when using tissues from infected mice. In this case gamma-GCS expression was organ and strain dependent for both the host and the parasite, indicating that environmental conditions have a profound effect on gamma-GCS expression. Consistent with the proposed mechanism from in vitro studies, increasing tissue GSH levels in the presence of SSG by cotreatment of L. donovani-infected mice with SSG solution and GSH incorporated into nonionic surfactant vesicles was more effective in reducing liver, spleen, and bone marrow parasite burdens than monotherapy with SSG. Together, these results indicate that SSG resistance is associated with manipulation of both host and parasite GSH levels by L. donovani.

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.

Combination therapy using sodium antimony gluconate in stearylamine-bearing liposomes against established and chronic Leishmania donovani infection in BALB/c Mice

In this work we report the activity seen with combination therapy using sodium antimony gluconate in liposomes composed of egg phosphatidyl choline and stearylamine for elimination of Leishmania donovani parasites from the liver and spleen of BALB/c mice with established and chronic infections.

Does the Leishmania major paradigm of pathogenesis and protection hold for New World cutaneous leishmaniases or the visceral disease?

Parasitic protozoa of the genus Leishmania have provided a useful perspective for immunologists in terms of host defense mechanisms critical for the resolution of infection caused by intracellular pathogens. These organisms, which normally reside in a late endosomal, major histocompatibility complex (MHC) class II(+) compartment within host macrophages cells, require CD4(+) T-cell responses for the control of disease. The paradigm for the CD4(+) T-helper 1 (Th1)/Th2 dichotomy is largely based on the curing/non-curing responses, respectively, to Leishmania major infection. However, this genus of parasitic protozoa is evolutionarily diverse, with the cutaneous disease-causing organisms of the Old World (L. major) and New World (Leishmania mexicana/ Leishmania amazonensis) having diverged 40-80 million years ago. Further adaptations to survive within the visceral organs (for Leishmania donovani, Leishmania chagasi, and Leishmania infantum) must have been required. Consequently, significant differences in host-parasite interactions have evolved. Different virulence factors have been identified for distinct Leishmania species, and there are profound differences in the immune mechanisms that mediate susceptibility/resistance to infection and in the pathology associated with disease. These variations not only point to interesting features of the host-pathogen interaction and immunobiology of this genus of parasitic protozoa, but also have important implications for immunotherapy and vaccine development.

Canine Leishmaniasis

Canine leishmaniasis is caused by Leishmania infantum (syn. L. chagasi, in America) and is transmitted by the bite of phlebotomine sand flies. Infected dogs constitute the main domestic reservoir of the parasite and play a key role in transmission to humans, in which the parasite produces visceral leishmaniasis. The increasing awareness that control of the human disease depends on effective control of canine leishmaniasis has promoted, in the last few years, research into leishmanial infection in dogs. Newly available specific reagents and molecular tools have been applied to the detailed investigation of canine leishmaniasis and important advances have been made in elucidating the epidemiology and pathology of the disease. These new findings have led to better understanding of the disease, and have also helped in the development of new diagnostic methods and control measures against the infection, such as insecticide-impregnated collars for dogs, new drugs and treatment protocols, and second generation vaccines, with the hope of not only reducing the heavy burden of the disease among dogs but also reducing the incidence of human visceral leishmaniasis.

Pharmacokinetics, toxicities, and efficacies of sodium stibogluconate formulations after intravenous administration in animals

The pharmacokinetics and toxicities of free sodium stibogluconate (SSG) and two vesicular formulations of this drug (a nonionic surfactant vesicular formulation of SSG [SSG-NIV] and SSG-NIV-dextran) were determined after treatment with a single intravenous dose in healthy dogs and were related to their antileishmanial efficacies in mice. Analysis of the curves of the concentrations in plasma after intravenous administration of SSG and SSG-NIV in dogs showed that both formulations produced similar antimony (Sb) pharmacokinetics. In contrast, treatment with SSG-NIV-dextran significantly modified the pharmacokinetics of the drug. The elimination half-life was four times longer (280 min) than that observed after administration of SSG (71 min) (P = 0.01), and the volume of distribution at steady state (V(SS)) was also increased (V(SS) for SSG, 0.21 liters/kg; V(SS) for SSG-NIV-dextran, 0.34 liters/kg [P = 0.02]), thus indicating that drug encapsulation favors the distribution of Sb into organs and increases its residence time in tissues. This would explain the superior antileishmanial efficacy of this formulation compared to those of the free drug in mice. No signs of toxicity were found in dogs after SSG and SSG-NIV administration. However, SSG-NIV-dextran treatment was associated with short-term toxicity, demonstrated by the development of chills and diarrhea, which cleared by 24 h postdosing, and hepatic dysfunction at 24 h postdosing (P < 0.05). The levels of all the biochemical parameters had returned to normal at 1 month postdosing. No signs of toxicity were observed in mice treated with all three formulations.

The in vivo susceptibility of Leishmania donovani to sodium stibogluconate is drug specific and can be reversed by inhibiting glutathione biosynthesis

Resistance to pentavalent antimonial (Sb(v)) agents such as sodium stibogluconate (SSG) is creating a major problem in the treatment of visceral leishmaniasis. In the present study the in vivo susceptibilities of Leishmania donovani strains, typed as SSG resistant (strain 200011) or SSG sensitive (strain 200016) on the basis of their responses to a single SSG dose of 300 mg of Sb(v)/kg of body weight, to other antileishmanial drugs were determined. In addition, the role of glutathione in SSG resistance was investigated by determining the influence on SSG treatment of concomitant treatment with a nonionic surfactant vesicle formulation of buthionine sulfoximine (BSO), a specific inhibitor of the enzyme gamma-glutamylcysteine synthetase which is involved in glutathione biosynthesis, and SSG, on the efficacy of SSG treatment. L. donovani strains that were SSG resistant (strain 200011) and SSG sensitive (strain 200016) were equally susceptible to in vivo treatment with miltefosine, paromomycin and amphotericin B (Fungizone and AmBisome) formulations. Combined treatment with SSG and vesicular BSO significantly increased the in vivo efficacy of SSG against both the 200011 and the 200016 L. donovani strains. However, joint treatment that included high SSG doses was unexpectedly associated with toxicity. Measurement of glutathione levels in the spleens and livers of treated mice showed that the ability of the combined therapy to inhibit glutathione levels was also dependent on the SSG dose used and that the combined treatment exhibited organ-dependent effects. The SSG resistance exhibited by the L. donovani strains was not associated with cross-resistance to other classes of compounds and could be reversed by treatment with an inhibitor of glutathione biosynthesis, indicating that clinical resistance to antimonial drugs should not affect the antileishmanial efficacies of alternative drugs. In addition, it should be possible to identify a treatment regimen that could reverse antimony resistance.

Evaluation of terbinafine treatment in Leishmania chagasi-infected hamsters (Mesocricetus auratus)

The objective of the present study was to assess the effect of terbinafine treatment in hamsters infected with Leishmania chagasi. Four of five groups of hamsters were infected with 3 x 10(7) L. chagasi promastigotes by the intracardiac route and submitted to different treatments of 30 days duration starting on the 30th day after inoculation. Group 1 was treated with 100mg/kg terbinafine PO, group 2 was treated with 80 mg/kg Glucantime IM, and group 3 was treated with a combination of the same dose of each drug by the same routes. Group 4 (control) received vehicle (Tween 80 [0.1%]+CMC[0.5%]+H(2)O [0.5 ml], PO). Spleen parasite burden and spleen relative weight were determined 3 days after the end of the treatment. The results were analyzed by the Kruskal-Wallis test (P < 0.05). There was no difference between the infected untreated and terbinafine-treated groups in spleen parasite burden (15.81+/-15.81 vs. 13.00+/-12.94, respectively). Terbinafine plus Glucantime (6.11+/-5.90) and Glucantime alone (4.83+/-4.82) significantly reduced spleen parasite burden compared to the infected untreated group (15.81+/-15.81, P<0.01). There was a difference in the relative weight of the spleen between the naïve and the infected untreated groups (2.5+/-0.2 vs. 9.8+/-1.0, respectively) as well as between the naïve and terbinafine groups (2.5+/-0.2 vs. 10.0+/-1.4, respectively). Glucantime alone and Glucantime plus terbinafine (2.5+/-0.2 and 4.2+/-0.6) significantly reduced the weight of the spleen in comparison with the infected untreated group. Even so, the spleen parasite burden was directly related to spleen weight. Terbinafine alone at the dose and schedule used had no effect on spleen parasite burden or relative spleen weight of L. chagasi-infected hamsters.

Efficacies of vesicular and free sodium stibogluconate formulations against clinical isolates of Leishmania donovani

In this study, the in vitro and in vivo efficacies of free sodium stibogluconate (SSG) and a nonionic surfactant vesicular formulation of SSG (SSG-NIV) against a laboratory strain of Leishmania donovani (MHOM/ET/67:LV82) and different clinical isolates of L. donovani were determined. Treatment with SSG-NIV was more effective against intramacrophage amastigotes than treatment with SSG. In vivo murine studies showed that there was interstrain variability in the infectivity of the different L. donovani strains, with two of the strains (20001 and 20003) giving low parasite burdens. In addition, interstrain variability in the antileishmanial efficacy of SSG in a single dose containing 300 mg of Sb(V)/kg of body weight was observed. This dose of free drug either caused a >97% reduction in liver parasite burdens or had no significant effect on parasite burdens compared with the result with the respective control. In some instances, treatment with this free SSG dose also caused a significant reduction in spleen (strain 20006) or bone marrow (strains 20001 and 20009) parasite burdens. Treatment with SSG-NIV was more effective than that with SSG against all of the strains tested. In SSG-responsive strains, the reduction in liver parasite burdens by SSG-NIV treatment was similar to that caused by free SSG. In SSG-nonresponsive strains, SSG-NIV treatment caused at least a 95% reduction in liver parasite burdens. Overall, these results indicate that the use of a vesicular formulation of SSG is likely to increase its clinical efficacy against visceral leishmaniasis.

Immunization with a recombinant stage-regulated surface protein from Leishmania donovani induces protection against visceral leishmaniasis

Vaccination against visceral leishmaniasis has received limited attention compared with cutaneous leishmaniasis, although the need for an effective vaccine against visceral leishmaniasis is pressing. In this study, we demonstrate for the first time that a recombinant stage-specific hydrophilic surface protein of Leishmania donovani, recombinant hydrophilic acylated surface protein B1 (HASPB1), is able to confer protection against experimental challenge. Protection induced by rHASPB1 does not require adjuvant and, unlike soluble Leishmania Ag + IL-12, extends to the control of parasite burden in the spleen, an organ in which parasites usually persist and are refractory to a broad range of immunological and chemotherapeutic interventions. Both immunohistochemistry (for IL-12p40) and enzyme-linked immunospot assay (for IL-12p70) indicate that immunization with rHASPB1 results in IL-12 production by dendritic cells, although an analysis of Ab isotype responses to rHASPB1 suggests that this response is not sufficient in magnitude to induce a polarized Th1 response. Although both vaccinated and control-infected mice have equivalent frequencies of rHASPB1-specific CD4(+) T cells producing IFN-gamma, vaccine-induced protection correlates with the presence of rHASPB1-specific, IFN-gamma-producing CD8(+) T cells. Thus, we have identified a novel vaccine candidate Ag for visceral leishmaniasis, which appears to operate via a mechanism similar to that previously associated with DNA vaccination.

Endogenous IL-4 is necessary for effective drug therapy against visceral leishmaniasis

It is well established that a fully competent immune response is required for the successful drug treatment of visceral leishmaniasis. However, recent studies have cast some doubt as to which elements of the immune response synergize with chemotherapeutic treatment. The role of the Th2 response and IL-4 in particular during visceral leishmaniasis awaits clarification. We, therefore, examined the effectiveness of sodium stibogluconate treatment on Leishmania donovani infection in BALB/c wild-type and IL-4-/- mice. Parasite burdens in L. donovani-infected IL-4+/- and IL-4-/-, as we have previously shown for B6/129 mice, were similar, despite an apparent type 1 antibody response in infected IL-4-/- mice, demonstrated by increased levels of parasite-specific IgG2a and decreased IgG1. Unexpectedly IL-4-/- mice responded poorly to sodium stibogluconate treatment with increased parasite burdens in all tissues examined. Furthermore, drug therapy of IL-4-/- but not IL-4+/+ mice resulted in significant reductions in splenocyte IFN-gamma mRNA transcripts and in serum IFN-gamma levels. These results demonstrate that IL-4 has an important role in effective anti-leishmanial chemotherapy which seems to be related to modulation of IFN-gamma production.

The cured immune phenotype achieved by treatment of visceral leishmaniasis in the BALB/c mouse with a nonionic surfactant vesicular formulation of sodium stibogluconate does not protect against reinfection

Single-dose treatment with sodium stibogluconate solution (SSG) and treatment with a nonionic surfactant vesicular formulation of sodium stibogluconate (SSG-NIV) were compared for the ability to protect BALB/c mice against infection with Leishmania donovani. Prophylactic treatment with SSG-NIV protected against infection, although its effects were time and organ dependent; protection was not obtained with SSG. Protection against reinfection with L. donovani was observed only in mice cured by treatment with SSG-NIV. However, this protective effect was probably due to the presence of residual drug rather than an immune effect, since prophylactic SSG-NIV treatment gave similar results. Transfer of enriched spleen T-cell populations from L. donovani-infected mice or from infected SSG-NIV-treated mice gave no protection against L. donovani infection in the recipients. T cells from infected mice, but not from infected SSG-NIV-treated mice, were infectious to recipients. SSG-NIV treatment was equally effective against visceral leishmaniasis in immunocompetent and SCID mice, whereas SSG treatment was less effective in the latter. The results of this study suggest that the high antileishmanial activity of SSG-NIV is due to favorable modification of SSG delivery and does not require a fully functional immune response. Cure of visceral leishmaniasis by SSG-NIV treatment in the BALB/c mouse did not protect against reinfection.

Comparison of the efficacy of free and non-ionic-surfactant vesicular formulations of paromomycin in a murine model of visceral leishmaniasis

Non-ionic-surfactant vesicular (NIV) formulations of paromomycin have been tested in-vitro and in-vivo for their activity against Leishmania donovani. Production of NIV was dependent both on the surfactant used and on the concentration of paromomycin; only two of the surfactants studied formed vesicles at the highest paromomycin concentration (9 mg mL(-1)). At surfactant-lipid concentrations > or = 1.5 mM, suspensions of NIV (drug- or glucose-loaded) were cytotoxic to macrophages infected with L. donovani; high levels of nitrite were produced in cell supernatants. At surfactant-lipid concentrations < 1.5 mM, drug-loaded NIV were more effective than the same dose of free drug, in terms of the percentage of cells infected and the number of parasites/cell. At surfactant-lipid concentrations < or = 0.15 mM, drug-loaded NIV were ineffective in-vitro. In-vivo, treatment with decaethylene glycol mono n-hexadecyl ether paromomycin NIV was more effective than hexaethylene glycol mono n-hexadecyl ether paromomycin NIV, in terms of suppression of liver and spleen parasite burdens. Against liver parasites, both types of paromomycin-loaded NIV were more effective than free drug. Neither the NIV nor free forms of paromomycin caused significant suppression of bone-marrow parasites. The study shows that entrapment of paromomycin in NIV can be used to increase its antileishmanial activity in-vitro and in-vivo.

Visceral leishmaniasis in the BALB/c mouse: a comparison of the efficacy of a nonionic surfactant formulation of sodium stibogluconate with those of three proprietary formulations of amphotericin B

In this study, treatment efficacies of a nonionic surfactant vesicle formulation of sodium stibogluconate (SSG-NIV) and of several formulations of amphotericin B were compared in a murine model of visceral leishmaniasis. Treatment with multiple doses of AmBisome, Abelcet, and Amphocil (total dose, 12.5 mg of amphotericin B/kg of body weight) resulted in a significant suppression of parasite burdens in liver (P < 0.0005) and spleen (P < 0.0005) compared with those of controls, with Abelcet having the lowest activity. Only AmBisome and Amphocil gave significant suppression of parasites in bone marrow (compared to control values, P < 0.005). In the acute-infection model, single-dose treatments of SSG-NIV (296 mg of SbV/kg), SSG solution (296 mg of SbV/kg), or AmBisome (8 mg of amphotericin B/kg) were equally effective against liver parasites (compared to control values, P < 0.0005). SSG-NIV and AmBisome treatment also significantly suppressed parasites in bone marrow and spleen (P < 0.005), with SSG-NIV treatment being more suppressive (>98% suppression in all three sites). Free-SSG treatment failed to suppress spleen or bone marrow parasites. Infection status influenced treatment outcome. In the chronic-infection model, the AmBisome single-dose treatment was less effective in all three infection sites and the SSG-NIV single-dose treatment was less effective in the spleen. The results of this study suggest that the antileishmanial efficacy of SSG-NIV compares favorably with those of the novel amphotericin B formulations.

New sterically stabilized vesicles based on nonionic surfactant, cholesterol, and poly(ethylene glycol)-cholesterol conjugates

Monomethoxypoly(ethylene glycol) cholesteryl carbonates (M-PEG-Chol) with polymer chain molecular weights of 1000 (M-PEG1000-Chol) and 2000 (M-PEG2000-Chol) have been newly synthesized and characterized. Their aggregation behavior in mixture with diglycerol hexadecyl ether (C16G2) and cholesterol has been examined by cryotransmission electron microscopy, high-performance gel exclusion chromatography, and quasielastic light scattering. Nonaggregated, stable, unilamellar vesicles were obtained at low polymer levels with optimal shape and size homogeneity at cholesteryl conjugate/ lipids ratios of 10 mol% M-PEG1000-Chol or 5 mol% M-PEG2000-Chol, corresponding to the theoretically predicted brush conformational state of the PEG chains. At 20 mol% M-PEG1000-Chol or 10 mol% M-PEG2000-Chol, the saturation threshold of the C16G2/cholesterol membrane in polymer is exceeded, and open disk-shaped aggregates are seen in coexistence with closed vesicles. Higher levels up to 30 mol% lead to the complete solubilization of the vesicles into disk-like structures of decreasing size with increasing PEG content. This study underlines the bivalent role of M-PEG-Chol derivatives: while behaving as solubilizing surfactants, they provide an efficient steric barrier, preventing the vesicles from aggregation and fusion over a period of at least 2 weeks.

Activity of pentamidine-loaded methacrylate nanoparticles against Leishmania infantum in a mouse model

The use of drug delivery systems may reduce the toxicity and improve the activity of antileishmanial compounds. In view of such a strategy, we loaded the antileishmanial agent pentamidine on polymethacrylate nanoparticles. The activity of pentamidine-loaded nanoparticles was compared with that of free pentamidine in a BALB/c mice model of visceral leishmaniasis induced by Leishmania infantum. On day 0, mice were infected intravenously with 10(7) promastigotes and then treated via the tail vein on days 14, 16 and 18 with bound pentamidine, free drug or isotonic saline (control group). On day 21, liver parasite burdens were evaluated using the Stauber method. Livers and spleens were removed and weighed. Effective doses (ED) were determined using the Michaelis-Menten representation relating the percentage of parasite suppression to the dose. The ED50 of bound pentamidine was six times lower than that of free pentamidine (0.17 mg kg-1 vs 1.06 mg kg-1). The ED90 value calculated for bound pentamidine was 1 mg kg-1. It was not possible to obtain the ED90 for free pentamidine because the dose-response curve reached a plateau near 60% of parasite suppression. A significant decrease in liver and spleen weights, probably reflecting the leishmanicidal activity, was observed for treated mice with bound pentamidine. These results showed that bound pentamidine was more potent than the free drug against L. infantum in our BALB/c mice model.

Comparison of the efficacies of various formulations of amphotericin B against murine visceral leishmaniasis

The antileishmanial efficacies of four proprietary amphotericin B (AmB) formulations (Fungizone, AmBisome, Abelcet, and Amphocil) and an experimental nonionic surfactant vesicle (NIV) formulation were compared in a murine model of acute visceral leishmaniasis. By a multiple-dosing regimen, groups of Leishmania donovani-infected BALB/c mice were treated (2.5 mg of AmB per kg of body weight) on days 7 to 11 postinfection with one of the AmB formulations, and parasite burdens were determined on day 18 postinfection. All of the formulations caused significant suppression parasite burdens in spleens (P < 0.01 to 0.0005) and livers (P < 0.0005) compared with those in the spleens and livers of the controls. In addition, a significant suppression of parasite burdens in bone marrow (P < 0.0005) compared to the burdens in the bone marrow of the controls was obtained for all the formulations except Abelcet, which was inactive at this site. On the basis of their overall efficacies (activity against liver, spleen, and bone marrow parasites), the formulations could be ranked as follows: Amphocil = AmBisome > AmB-NIV > Abelcet >> Fungizone. On the basis of spectrophotometric measurements, AmB was shown to exist in a predominantly aggregated state in all of the formulations. Although incubation in 50% serum altered the degree of aggregation, the AmB remained predominantly aggregated, indicating that the AMB-lipid complex in all of the formulations was physically stable. The results of the study showed that antiparasitic efficacy is associated positively with the degree of AmB aggregation in the presence of serum.

Immune responses of Leishmania donovani infected BALB/c mice following treatment with free and vesicular sodium stibogluconate formulations

The anti-parasitic efficacy of free and a non-ionic surfactant vesicular (NIV) sodium stibogluconate (SSG) formulation of the drug, and their effect on the immune responses of Leishmania donovani infected BALB/c mice, was compared. The SSG NIV formulation maintained a significant suppression of splenic, hepatic and bone marrow parasite burdens (P < 0.005) compared to control values throughout the study. Infected controls and drug treated animals had high levels of L. donovani specific antibodies by day 14 of the study and the titre of these antibodies increased throughout the study for infected controls and free SSG treated animals. Initially SSG NIV treated animals had significantly higher specific IgG2a levels (P < 0.01, day 16) compared with infected controls and free SSG treated mice, but by day 31 the levels of this isotype and other antibodies (IgG1, IgG3 and IgM) were significantly lower (P < 0.05) than values for the other two groups. There was no difference in the proliferative responses of spleen cells taken from infected controls and drug treated animals to both specific and non-specific stimulation at day 16 of the study. On day 31, only spleen cells taken from infected mice given SSG NIV displayed a significant proliferative response to parasite antigen preparations and Concanavalin A stimulation (P < 0.01). No IL4 was detected in supernatants from in vitro spleen cells cultures. Significant levels of IFN-gamma was induced by stimulation of cells from vesicular drug treated animals with a frozen parasite preparation compared with medium controls (P < 0.05) on day 49 but not day 16. Similar stimulation did not induce IFN gamma production in spleen cells from infected controls or free drug treated animals. Only SSG NIV treated animals gave a significant positive DTH response to an L. donovani parasite preparation (P < 0.05) given on day 31. The results of this study indicate that there was a formulation dependent qualitative difference in the post-treatment immune responses of L. donovani infected animals, with SSG NIV animals displaying immune responses expected for a cured phenotype.

Therapeutic effect of reference antileishmanial agents in murine visceral leishmaniasis due to Leishmania infantum

A sensitive, culture-based, microtitration technique has recently been developed for determining parasite burdens in organs recovered from Balb/c mice infected with Leishmania infantum. In the present study, this technique was used to examine the efficacy of three, first-line, antileishmanial agents in reducing parasite burdens and eradicating parasites from target organs in mice. Treatment with meglumine antimoniate (50 mg SbV/kg.day) significantly reduced the parasite burdens in the livers and lungs (by about 10-fold and > 100-fold, respectively) but not those in the spleens. Although use of a higher dose of meglumine antimoniate (200 mg SbV/kg.day) resulted in an even more dramatic reduction in the parasite burdens in the livers, it had no significant effect on the burdens in the spleens. Treatment with amphotericin B (0.8 mg/kg every other day) resulted in significant reductions in the parasite burdens in the livers, spleens and lungs of infected mice. Although low doses of aminosidine (20 mg/kg.day) had no effect, high doses (200 mg/kg.day) resulted in undetectable parasite burdens in the livers, for at least 100 days post-treatment, and marked reductions in burdens in the spleens. These results are consistent with previous data from studies using animal models of visceral leishmaniasis. Thanks to the sensitivity of the technique, culture microtitration revealed that none of the drug schedules achieved the elimination of all parasites in all target organs. The murine model used mimics some important features of HIV/Leishmania infantum co-infections in humans.

Skin uptake, distribution, and elimination of antimony following administration of sodium stibogluconate to patients with cutaneous leishmaniasis

We examined in this study the pharmacokinetics of Sb in the affected skin and normal skin of patients treated with sodium stibogluconate for cutaneous leishmaniasis and compared the results with those for the blood. The procedure was fully explained, and a written consent was obtained from each of nine patients. After a dose of sodium stibogluconate equivalent to 600 mg of Sb was administered intramuscularly, small skin biopsies were collected under local anesthesia at different time intervals from the circumferences of the lesions and simultaneously from normal skin. Antimony was measured in these biopsies after suitable ashing and processing by flameless atomic absorption spectrophotometry. The means (with standard errors of the means in parentheses) of the peak concentration, time to peak concentration, area under the curve, half-life, and mean residence time in lesions were 5.02 (1.43) micrograms/g, 2.1 (0.4) h, 32.8 (6.1) micrograms.h/g, 6.88 (0.54) h, and 10.4 (1.2) h, respectively, and those in normal skin were 6.56 (2.01) micrograms/g, 2.6 (0.8) h, 44.0 (15.8) micrograms.h/g, 5.44 (0.83) h, and 8.08 (1.34) h, respectively. There was no significant difference in any of these parameters between lesions and normal skin, whereas the differences in peak concentration, half-life, and mean residence time between lesions and whole blood were significant (P < or = 0.05). The penetration of Sb into skin, either affected or normal, as measured by the skin/blood area under the curve ratio appears to be complete, but the disposition is slow compared with that from the blood.

Visceral leishmaniasis in the BALB/c mouse: a comparison of the in vivo activity of five non-ionic surfactant vesicle preparations of sodium stibogluconate

Five non-ionic surfactants (Surfactants V-IX) were screened for their ability to produce vesicles for the delivery of sodium stibogluconate. Mean vesicle diameter and antimony content were determined prior to in vivo assessment of antiparasitic activity in a mouse model of acute visceral leishmaniasis. V/D suspensions (i.e. stibogluconate loaded vesicles kept in the hydrating drug solution) were more effective against spleen, liver and bone marrow parasites than drug loaded vesicle suspensions that had unentrapped drug removed. A Surfactant IX V/D suspension was the most active antileishmanial preparation causing 74 +/- 10%, 99 +/- 1% and 38 +/- 8% suppression of liver, spleen and bone marrow parasite burdens respectively. Contrary to previous findings, a reduction in splenic and bone marrow parasite burdens was achieved using large vesicles (mean diameter > 800nm). The significance of these results is discussed.

Drug distribution and a pulmonary adverse effect of intraperitoneally administered doxorubicin niosomes in the mouse

Niosomes (non-ionic surfactant vesicles) prepared from C16G2 (a hexadecyl-diglycerol ether), and loaded with doxorubicin, were administered intraperitoneally to male AKR mice at dose levels of 0, 2.5, 5.0, and 10.0 mg kg-1. Free drug was given at 10.0 mg kg-1 by the intraperitoneal route. At a dose level of 10.0 mg kg-1, peak doxorubicin levels in the central compartment were attained faster with the free drug than with the niosome formulation. However, the peak plasma levels were similar for the free drug and the niosome preparation at the 10 mg kg-1 dose level. With doxorubicin administered as the niosome preparation by the intraperitoneal route at 2.5, 5.0, and 10.0 mg kg-1, mean peak plasma concentrations of the drug showed a tendency to be dose-related although the differences were not significant. Over the 24 h period of the experiment, with doxorubicin at 10 mg kg-1, the niosome formulation delivered significantly more drug to the plasma compartment than the free drug (p < 0.05). When doxorubicin was given in niosomes at 2.5, 5.0 and 10.0 mg kg-1 by the intraperitoneal route, the resulting levels of doxorubicin in cardiac tissue were not dose related and the differences not significant and, although the mean peak cardiac-tissue concentration was higher in animals receiving the free drug at 10.0 mg kg-1 intraperitoneally than in mice given intraperitoneal doxorubicin niosomes at this dose level, the differences were again not significant. There were clinical signs of toxicity in mice given doxorubicin-containing niosomes intraperitoneally at 5.0 and 10.0 mg kg-1, and at post-mortem an accumulation of fluid in the pleural cavity was evident. These changes were not seen in mice dosed intraperitoneally with free drug at 10 mg kg-1, or in animals given doxorubicin niosomes intraperitoneally at 2.5 mg kg-1. In mice dosed intraperitoneally with doxorubicin niosomes at 12.0 mg kg-1 and at a dose volume of 0.2-0.4 mL, histological examination of the lungs demonstrated a congestion of the alveolar capillaries, and an increased number of acute inflammatory cells in the alveolar walls. There was no histological evidence of lung toxicity in mice dosed with doxorubicin niosomes at 12.0 mg kg-1 when the formulation was administered with the higher dose volume of 1.8-2.0 mL. Importantly there was no histological evidence of lung toxicity in mice dosed with empty niosomes intraperitoneally or with doxorubicin niosomes given intravenously at 12.0 mg kg-1.

Genetic control of drug-induced recovery from murine visceral leishmaniasis

The influence of host genetic background on the response of Leishmania donovani-infected mice to chemotherapy was studied using the H-2d and H-2b haplotypes on a BALB or a B10 genetic background. Animals were treated with free or liposomal sodium stibogluconate and parasite burdens in the liver, spleen and bone marrow were assessed. In all the mouse strains and their congenic derivatives examined, the liver responded best to therapy regardless of drug formulation, whilst the spleen and the bone marrow respectively were increasingly less responsive to chemotherapy. Treatment with free drug was more effective in congenic mice carrying the H-2b haplotype than in those carrying the H-2d haplotype and in mice carrying the same H-2 haplotype, animals from a BALB background were better responders than those from a B10 genetic background. Liposomal drug was more effective than free drug treatment in all four mouse strains and produced a similar significant suppression (> 99%, P < 0.001) in liver parasite burdens to that obtained using a six times greater free drug dose. This liposomal drug dose was more effective than free drug in reducing bone marrow parasite burdens in all four mouse strains and equally (BALB/c mice) or more effective (P < 0.01, BALB/B, B10 and B10.D2 strains) in reducing spleen parasite numbers. Liposomal dependent influences apparent using free sodium stibogluconate. These results are discussed in relation to the genetic factors which are known to control the course of L. donovani infection in mice.

Passive vectoring of a colloidal carrier system for sodium stibogluconate: preparation, characterization and performance evaluation

The intracellular residence of the Leishmania parasite in the cells of the reticuloendothelial system--predominantly the liver and spleen--prompted the development of a polymeric, particulate, colloidal carrier system for the antileishmanial drug sodium stibogluconate. The system was pharmaceutically characterized for shape, size, structural integrity, electrokinetic properties and in vitro drug release. The relationship between such physical parameters as size, electrophoretic mobility and surface charge and the effectiveness of the system is discussed. Subsequent in vivo studies in rats revealed that the carrier system successfully vectored the drug to the site of infection.

The distribution of free and non-ionic vesicular sodium stibogluconate in the dog

The pharmacokinetics and tissue distribution of antimony after the administration of sodium stibogluconate in a free form or entrapped in vesicles prepared from non-ionic surfactant were studied in the dog. Animals were given either one or two intravenous bolus injection(s) equivalent to 45 mg Sb kg-1 as free drug or 0.625 or 0.685 mg Sb kg-1 as vesicular drug. Blood samples were taken at various times after dosing and antimony levels in various tissues were determined at 3 h, 48 h and 6 days after dosing. After free stibogluconate antimony clearance from the blood occurred in a rapid elimination phase with a blood half-life of 0.58 +/- 0.08 h. This rapid elimination phase did not occur after vesicular drug. Both drug preparations gave similar antimony levels in the spleen, liver and femur and humerus bone marrow at all time points assessed even though the vesicular dose was one-seventieth of the free drug dose. After the free drug there was marked urinary excretion of antimony and, as a result, increased kidney loading at the expense of other tissue. Vesicle-mediated drug delivery suppressed renal excretion and a much greater proportion of the antimony dose was recovered from tissue than was obtained after free drug. A hypothesis is presented to account for the differences in tissue antimony concentrations produced by the two formulations.

Hexadecylphosphocholine: oral treatment of visceral leishmaniasis in mice

Hexadecylphosphocholine (He-PC), a novel phospholipid derivative, was tested against Leishmania donovani and Leishmania infantum, the causative agents of visceral leishmaniasis. In vitro, promastigotes were highly susceptible to He-PC; the 50% inhibitory concentrations were between 0.89 and 2.25 micrograms/ml for the different leishmanial strains. In vivo, a marked antileishmanial activity in infected BALB/c mice could be demonstrated after oral administration of He-PC. Whereas parasite suppression and killing in the liver were comparable after 5 days of treatment with He-PC (10 or 20 mg/kg of body weight per day administered orally) and sodium stibogluconate (120 mg of pentavalent antimonal agent per kg/day administered subcutaneously), a superior reduction in the parasite load in the spleen and bone marrow was observed after oral treatment with He-PC. After a 4-week treatment period, parasite suppression in the spleen was better than that observed with standard sodium stibogluconate therapy by a factor of more than 600.