Abstract
Most filarial parasites in the subfamilies Onchocercinae and Dirofilariinae depend on Wolbachia endobacteria to successfully carry out their life cycle. Recently published data indicate that the few Wolbachia-free species in these subfamilies were infected in the distant past and have subsequently shed their endosymbionts. We used an integrated transcriptomic and proteomic analysis of Onchocerca flexuosa to explore the molecular mechanisms that allow worms of this species to survive without a bacterial partner. Roche/454 sequencing of the adult transcriptome produced 16,814 isogroup and 47,252 singleton sequences that are estimated to represent approximately 41% of the complete gene set. Sequences similar to 97 Wolbachia genes were identified from the transcriptome, some of which appear on the same transcripts as sequences similar to nematode genes. Computationally predicted peptides, including those with similarity to Wolbachia proteins, were classified at the domain and pathway levels in order to assess the metabolic capabilities of O. flexuosa and compare against the Wolbachia-dependent model filaria, Brugia malayi. Transcript data further facilitated a shotgun proteomic analysis of O. flexuosa adult worm lysate, resulting in the identification of 1,803 proteins. Three of the peptides detected by mass spectroscopy map to two ABC transport-related proteins from Wolbachia. Antibodies raised to one of the Wolbachia-like peptides labeled a single 38 kDa band on Western blots of O. flexuosa lysate and stained specific worm tissues by immunohistology. Future studies will be required to determine the exact functions of Wolbachia-like peptides and proteins in O. flexuosa and to assess their roles in worm biology.
Highlights
Filarial nematodes are a family of medically and economically significant parasites that infect all classes of vertebrates except fish [1]
The relationship between Wolbachia and Wolbachia-dependent filarial nematodes has been a topic of keen interest in recent years since Wolbachia was identified as a potential anti-filarial drug target
Most research on this relationship has focused on Wolbachia-dependent filarial parasites of humans and domestic animals
Summary
Filarial nematodes are a family of medically and economically significant parasites that infect all classes of vertebrates except fish [1]. Eight filarial species parasitize humans, but most morbidity is caused by Wuchereria bancrofti, Brugia malayi, and Onchocerca volvulus. The drugs employed in these efforts have limited activity against adult filarial worms [4]. Most filarial parasites of humans and domestic animals contain a bacterial endosymbiont (Wolbachia pipientis) that is required for development and reproduction [5]. Antibiotic treatments that clear Wolbachia cause stunted growth, infertility, and eventual death of adult filarial worms [6,7]. This suggests that the Wolbachia-mediated biochemical pathways or processes required by filarial nematodes could serve as drug targets [8]. The best pathways or processes to target have not been identified
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