Background: Filarial infections causing lymphatic filariasis or onchocerciasis (river blindness) can be treated with antibiotics (e.g. doxycycline) targeting the essential endosymbiotic Wolbachia bacteria. The depletion of Wolbachia inhibits worm development and causes worm death. Available antibiotics have restrictions for use in children and pregnant or breastfeeding women. Therefore, alternative antibiotics are needed that can be given to all members of the population and that are active with a shorter therapy time. Antibiotics of the acyldepsipeptide class have been shown to inhibit the growth of bacteria by overactivating the peptidase ClpP. The novel mode of action of this class of antibiotics could lead to faster killing of intracellular bacteria.
Objectives: To characterize acyldepsipeptide activity against the Wolbachia ClpP.
Methods: The activity of acyldepsipeptides was investigated against Wolbachia in vitro in insect cells and also against worms in culture. In addition, structural effects were investigated by fluorescence microscopy and electron microscopy. The activity of ClpP was also investigated in vitro.
Results: We show that acyldepsipeptides are active against recombinant Wolbachia ClpP and endobacteria resident within insect cells in vitro, and some derivatives were also active against filarial worms in culture. As a consequence of treatment, the worms became immotile and died, the latter confirmed by a viability assay.
Conclusions: The mode of action of the acyldepsipeptides in Wolbachia is the dysregulation of ClpP, causing the uncontrolled degradation of proteins, including the cell division protein FtsZ. Our results demonstrate that wolbachial ClpP is a target for further antifilarial antibiotic discovery.
Keywords: FtsZ; Litomosoides sigmodontis; acyldepsipeptides; filariasis.