Activating autophagy in filarial worms to identify novel macrofilaricides

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More than 120 million of poorest in the world are at high risk of suffering the debilitating effects of the parasitic filarial nematodes⎯ Wuchereria bancrofti, Brugia malayi, and B. timori ⎯ that live in the lymphatic system and cause human lymphatic filariasis, commonly known as elephantiasis, as well as other severe pathologies. Onchocerciasis (river blindness), for one, is caused by Onchocerca volvulus, which resides within subcutaneous nodules and releases the microfilariae (Mf) that are responsible for ocular or dermal pathologies, including blindness. International control programs, which target 1.5 billion people in danger of infection, focus on controlling the transmission of infections. Unfortunately, the treatments used for mass drug administration initiatives (ivermectin) produce only microfilaricidal effects – they block transmission but have no effect on the adult parasites. They also require long-term yearly administration, are contraindicated in areas co-endemic with Loa loa, exempt children and pregnant women, and promote drug resistance in filarial nematodes. Together, these limitations point to a crucial need for the development of new anti-filarial drugs, specifically macrofilaricidal drugs that kill adult worms. Recent data demonstrate the unique potential of using Wolbachia, the mutualistic bacteria of filarial nematodes, as a novel chemotherapeutic target against human filarial infections. Clinical studies showed that the administration of antibiotics (doxycycline) kills endosymbionts and causes macrofilaricidal effects. To explore this potential, we introduce a novel approach: a host(parasite)- oriented treatment that induces a host innate defense and forces filarial nematodes to eliminate their endosymbiont. We intend to take advantage of autophagy, a mechanism of eukaryotic cells to maintain a healthy intracellular environment and protect cells against intracellular invaders (e.g., bacteria, virus es). The process is essential for bacteria-filaria symbiosis and its alteration killed Wolbachia and, consequently, the worm itself. We obtained proof, that niclosamide (autophagy inducer) activates autophagy in parasites, significantly decreases number of bacteria and causes embryostatic effect in adult worms. Our project will determine that the autophagy inducers can be candidate macrofilaricidal drugs. In Aim 1, to prove that autophagy inducers are effective in vivo against filarial parasites and can be used as macrofilaricidal drugs, we will evaluate the efficacy of niclosamide in Brugia infected jirds. In parallel, we will test the other 23 repurposed drugs (known autophagy inducers) on adult Brugia parasites in vitro and compare their effects on the Wolbachia load and adult worm fitness. The in vitro assays in Aim 1 will result in the selection of the best hits (even better than niclosamide). In Aim 2, the best 2 candidates will be validated in our in vivo Brugia/jird model of infection. Our end goal is to identify effective new microfilaricides that interfere with symbiosis. This initiative, we believe, will yield a new class of active compounds and open perspectives for repurposed drugs, for use as alternatives to or in combination with current anti-filarial treatments.