Efficacy of Combined Therapy with Liposome-Encapsulated Meglumine Antimoniate and Allopurinol in Treatment of Canine Visceral Leishmaniasis

Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
Antimicrobial Agents and Chemotherapy (Impact Factor: 4.57). 03/2012; 56(6):2858-67. DOI: 10.1128/AAC.00208-12
Source: PubMed

ABSTRACT An innovative liposomal formulation of meglumine antimoniate (LMA) was recently reported to promote both long-term parasite suppression and reduction of infectivity to sand flies in dogs with visceral leishmaniasis. However, 5 months after treatment, parasites were still found in the bone marrow of all treated dogs. In order to improve treatment with LMA, the present study aimed to evaluate its efficacy in combination with allopurinol. Mongrel dogs naturally infected with Leishmania infantum were treated with six doses of LMA (6.5 mg Sb/kg of body weight/dose) given at 4-day intervals, plus allopurinol (20 mg/kg/24 h per os) for 140 days. Comparison was made with groups treated with LMA, allopurinol, empty liposomes plus allopurinol, empty liposomes, and saline. Dogs remained without treatment from day 140 to 200 after the start of treatment. The drug combination promoted both clinical improvement of dogs and significant reduction in the parasitic load in bone marrow and spleen on days 140 and 200 compared to these parameters in the pretreatment period. This is in contrast with the other protocols, which did not result in significant reduction of the bone marrow parasite load on day 200. Strikingly, the combined treatment, in contrast to the other regimens, induced negative quantitative PCR (qPCR) results in the liver of 100% of the dogs. Both xenodiagnosis and skin parasite determination by qPCR indicated that the drug combination was effective in blocking the transmission of skin parasites to sand flies. Based on all of the parasitological tests performed on day 200, 50% of the animals that received the combined treatment were considered cured.

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    ABSTRACT: Objective: Test the hypothesis that pegylated meglumine antimoniate-containing liposomes (LMA) and their mixture with non-pegylated (conven-tional) LMA may be more effective than conventional LMA against visceral leishmaniasis (VL), because of wider drug distribution among different mononuclear phagocyte system (MPS) tissues. Methods: Sb was determined in the blood and MPS tissues after administra-tion of pegylated or conventional LMA intravenously to mongrel dogs naturally infected with Leishmania infantum and Swiss mice. Pegylated and conventional LMA as well as their mixture were evaluated for their antileish-manial efficacy in BALB/c infected with L. infantum through determination of parasite load in liver, spleen and bone marrow. Results: An improved targeting of Sb to the bone marrow of dogs was clearly evidenced, as an important impact of pegylation. In accordance with this data, pegylated LMA significantly reduced parasite load in bone marrow of infected mice, in contrast to conventional LMA. The mixed formulation of conventional and pegylated LMA promoted parasite suppression to a higher extent in both spleen and bone marrow, compared to pegylated or conventional LMA. Conclusions: The present work establishes for the first time the potential of mixed formulations of conventional and pegylated liposomes as a drug delivery strategy for improved treatment of VL.
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    ABSTRACT: Using flow cytometry, we evaluated the frequency of CD4(+) and CD8(+) T cells and Foxp3(+) Treg cells in mononuclear cells in cervical and mesenteric lymph nodes, colon, and jejunum of dogs naturally infected with Leishmania infantum and in uninfected controls. All infected dogs showed chronic lymphadenitis and enteritis. In spite of a persistent parasite load, no erosion or ulcers were evident in the epithelial mucosa. The colon harbored more parasites than the jejunum. Frequency of total CD4(+), total Foxp3 and CD4(+)Foxp3(+) cells were higher in jejunum versus colon. Despite negative ELISA serum results for cytokines, levels of IL-10, IFN-γ, TGB-β, and TNF-α were higher in jejunum than colon of infected dogs. However, IL-4 was higher in colon than jejunum of infected dogs. There was no observed correlation between clinical signs and histopathological changes, or immunological and parasitological findings in the GIT of canines with visceral leishmaniasis. However, distinct segments of the GIT presented different immunological and parasitological responses. Jejunum showed a lower parasite load with increased frequency and expression of CD4, Foxp3, and CD8 receptors and IL-10, TGF-β, IFN-γ, and TNF-α cytokines. Colon showed higher parasite load with increasing expression of IL-4 cytokine. Leishmania infantum infection increased expression of CD4, Foxp3, IL-10, TGF-β, IFN- γ, and TNF-α, and reduced CD8 and IL-4 expression both in jejunum and colon.
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    ABSTRACT: Leishmaniasis has several clinical forms: self-healing or chronic cutaneous leishmaniasis or post-kala-azar dermal leishmaniasis; mucosal leishmaniasis; visceral leishmaniasis (VL), which is fatal if left untreated. The epidemiology and clinical features of VL vary greatly due to the interaction of multiple factors including parasite strains, vectors, host genetics, and the environment. Human immunodeficiency virus infection augments the severity of VL increasing the risk of developing active disease by 100–2320 times. An effective vaccine for humans is not yet available. Resistance to chemotherapy is a growing problem in many regions, and the costs associated with drug identification and development, make com-mercial production for leishmaniasis, unattractive. The toxicity of currently drugs, their long treatment course, and limited efficacy are significant concerns. For cutaneous disease, many studies have shown promising results with immunotherapy/immunochemotherapy, aimed to modulate and activate the immune response to obtain a therapeutic cure. Nowa-days, the focus of many groups centers on treating canine VL by using vaccines and immunomodulators with or without chemotherapy. In human disease, the use of cytokines like interferon-γ associated with pentavalent antimonials demonstrated promising results in patients that did not respond to conventional treatment. In mice, immunomodulation based on monoclonal antibodies to remove endogenous immunosuppressive cytokines (interleukin-10) or block their receptors, antigen-pulsed syngeneic dendritic cells, or biolog-ical products like Pam3Cys (TLR ligand) has already been shown as a prospective treatment of the disease. This review addresses VL treatment, particularly immunotherapy and/or immunochemotherapy as an alternative to conventional drug treatment in experimental models, canine VL, and human disease.
    Frontiers in Immunology 06/2014; 5(272). DOI:10.3389/fimmu.2014.00272
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