JAC Advance Access published online on April 16, 2007
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkm079
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A trial of immunotherapy against Leishmania amazonensis infection in vitro and in vivo with Z-100, a polysaccharide obtained from Mycobacterium tuberculosis, alone or combined with meglumine antimoniate
1 Department of Parasitology, Kochi Medical School, Kochi University, Kohasu, Okoh, Nankoku, Kochi 783-8505, Japan 2 Instituto de Patología Experimental, Facultad de Ciencias de la Salud, Universidad Nacional de Salta/Consejo Nacional de Investigaciones Científicas y Técnicas, Salta, Argentina 3 Department of Veterinary Hygiene, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan
* Corresponding author. Tel/Fax: +81-88-880-2415; E-mail: jm-paola{at}kochi-u.ac.jp
Objectives: To determine the efficacy and the immunomodulatory function of Z-100 alone or combined with meglumine antimoniate on Leishmania amazonensis infection.
Methods: The effect of the compounds was evaluated by microscopic counting of intracellular amastigotes in macrophages stained with Giemsa, or axenic promastigotes, and IC50 was determined by linear regression. The antileishmanial effect of the compounds was assessed in infected BALB/c mice by a limiting dilution analysis and the production of gamma interferon (IFN-
), interleukin 10 (IL-10), IL-4, IgG1 and IgG2a was measured by ELISA.
Results: In vitro, Z-100 showed antileishmanial activity against intracellular amastigotes of L. amazonensis with an IC50 of 13 mg/L. Moreover, infected macrophages treated with Z-100 (12 mg/L) showed smaller parasitophorous vacuoles with fewer parasites than the control. In addition, the efficacy of Z-100 plus meglumine antimoniate [14 mg/L pentavalent antimony (Sbv)] was higher (46% inhibition) than either Z-100 or meglumine antimoniate alone. Nevertheless, no effect of Z-100 on axenic promastigotes was observed. Infected BALB/c mice treated with Z-100 (100 µg/kg) alone did not show any antileishmanial effects in comparison with the control group, and IFN-, as well as IL-10 and IL-4, was up-regulated by the treatment. In addition, both IgG1 and IgG2a were also increased by the Z-100 treatment. Although Z-100 plus meglumine antimoniate (14 or 28 mg/kg Sbv) controlled both the parasite load and the footpad swelling in comparison with control mice, no significant differences were found with meglumine antimoniate alone.
Conclusions: In vitro, Z-100 alone or combined with meglumine antimoniate showed an antileishmanial effect on L. amazonensis. However, no effect was observed in infected BALB/c mice treated with Z-100, suggesting that the up-regulation of IL-10 and IL-4 production by the treatment could be interfering with the development of a protective Th1-type response. For further understanding of the effects of Z-100 in vivo, another strain of mice such as C57BL/6 should be tested in future.
Key Words: L. amazonensis , IL-10 , IL-4