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The Role of Autophagy in Anti-Wolbachia Antibiotic Therapy

Yousef, Anfal (2019) The Role of Autophagy in Anti-Wolbachia Antibiotic Therapy, Thesis (Doctoral), Liverpool School of Tropical Medicine.

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Lymphatic filariasis (LF) and onchocerciasis are significant global public health issues with more than 900 million individuals at risk and over 60 million people currently living with symptomatic manifestations caused by filarial diseases. Current drug treatments (albendazole, diethylcarbamazine citrate, ivermectin), which form the mass drug administration (MDA) of the World Health Organisation (WHO), only have a microfilaricidal properties and have a partial or ineffective efficacy against adult worms. The WHO has recognised that its target of achieving LF elimination by 2020 is not currently attainable through current MDA and has highlighted the importance of finding alternative drug regiments. Due to the importance of Wolbachia, an essential mutualistic intracellular bacterium, in the survival of filarial nematodes, anti-Wolbachia therapy has been validated as a safe macrofilaricidal treatment for LF and onchocerciasis. The A-WOL consortium was established with the goals of refining existing (repurposed) anti-Wolbachia antibiotics, as well as developing new drugs in a course of 7 days or less. Autophagy was chosen as a potential target in anti-Wolbachia drug efficacy due to previous research highlighting its role in the regulation of Wolbachia populations. In this study, we investigated the role of autophagy in the mode-of-action and efficacy of the portfolio of anti-Wolbachia drugs. This research has identified a range of concentrations for two autophagy inhibitors, wortmannin and l-asparagine, that suppressed autophagy and did not negatively impact cell growth, viability and toxicity in mosquito C6/36 cells and nematodes. By testing autophagic activity, this work has demonstrated a consistent increase in autophagy in four broad-spectrum anti-Wolbachia antibiotics from different classes (doxycycline, rifampicin, moxifloxacin and sparfloxacin) exposed to two different insect cell lines (C6/36 and SF9 cells) and in B. malayi microfilariae (mf). This activation was also observed for selected-candidates from the A-WOL consortium (TylAMacTM, AWZ1066S and fusidic acid). Antibiotic-induced autophagy was observed in the absence of Wolbachia, indicating its effect independent of the bacteria. In this work, the activation of autophagy was not observed in mammalian cells indicating that autophagy activation by anti-Wolbachia drugs is restricted to insect cells and nematodes. Through concentration-dependency testing of anti-Wolbachia antibiotics, this study has demonstrated that only concentrations that induced autophagy resulted in effective Wolbachia depletion (of >90%), the empirical threshold of delivering the desired macrofilaricidal activity. In this work, the contribution of autophagy in the efficacy of anti-Wolbachia drugs and their ability to reduce bacterial viability was demonstrated in B. malayi mf and adult worms when autophagy was inhibited during anti-Wolbachia drug exposure. Moreover, a partial role for autophagy was observed in the continued decline in Wolbachia post-drug exposure. The findings of this research could be used in developing high-throughput screening of additional drug libraries and in the lead optimisation of existing 'hits' identified by the A-WOL consortium. Autophagy can become an important target for anti-Wolbachia drug research and provide future solutions in drug therapy. The outcomes of the study may help future work in improving the understanding of selective autophagy and the development of treatments against filarial diseases and other infectious diseases.

Item Type: Thesis (Doctoral)
Subjects: QU Biochemistry > Cells and Genetics > QU 375 Cell physiology
QV Pharmacology > Anti-Bacterial Agents. Tissue Extracts > QV 350 Anti-bacterial agents (General or not elsewhere classified)
QW Microbiology and Immunology > Bacteria > QW 150 Proteobacteria. Rickettsiaceae, Wolbachia
QX Parasitology > Helminths. Annelida > QX 203 Nematoda
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 880 Filariasis and related conditions (General)
Faculty: Department: Biological Sciences > Department of Tropical Disease Biology
Depositing User: Lynn Roberts-Maloney
Date Deposited: 18 Oct 2019 15:08
Last Modified: 11 Feb 2020 02:02


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