Modifying amphotericin B for the treatment of cutaneous leishmaniasis

Abstract

Cutaneous leishmaniasis (CL) is a neglected tropical disease. It presents as disfiguring and deforming skin lesions. There is an urgent need for a simple, low-cost and non-toxic treatment for use in resource poor countries. As amphotericin B (AmB) has transformed visceral leishmaniasis treatment, I have developed and optimised a poly (methacrylic acid)-AmB drug (AmB-PMA). This involved the use of a commercially available, non-toxic, well-defined narrow molecular weight distribution polymer, poly (methacrylic acid sodium salt) (PMA) associated with AmB to create AmB-PMA. After chemical synthesis optimisation, AmB-PMA was shown to be less toxic than clinical grade AmB, and it was effective against Leishmania spp. promastigotes and amastigotes in vitro. To determine in vivo efficacy, studies were performed using BALB/c mice. They develop progressive non-healing skin lesions and are unable to control parasite growth. Mice were infected subcutaneously with L. major (LV39) promastigotes and treated locally with AmB-PMA. Studies were then conducted to evaluate the optimum route of administration, treatment frequency and dosing schedules. The results showed a reduction in both parasite burden and lesion size of the infected treated footpad with no adverse toxicity. Cytokine production was determined by quantitative real-time PCR for mRNA at the lesion site and the draining lymph node. I found that the AmB-PMA could effectively heal an established lesion and cure a CL infection. This was associated with: - (i) increased IFN-Y and TNF-α production, (ii) reduced IL-10 and MIP-1β production, when compared to infected, untreated lesions. The success of this treatment approach was also evaluated by histological studies. In addition, treated mice with resolved primary cutaneous lesions mounted a delayed type hypersensitivity response 24 h after challenge of the contra-lateral footpad with L. major. My thesis demonstrates the new opportunity for a cost-effective AmB based polymer drug that can be used locally to cure CL.