Over 140 million people are afflicted with filarial nematode-based diseases with over a billion at risk in over 70 countries. Of the estimated 120 million people afflicted with Lymphatic Filariasis, caused by Wuchereria bancrofti, Brugia malayi, and B. timori, 15 million present with swelling of the soft tissue, with the most extreme case known as Elephantiasis, while 25 million men present with scrotal hydrocele, causing great pain and disability. Another 18 million are afflicted with Onchocerciasis, caused by O. volvulus, which results in the deterioration of skin and eye tissue, with River Blindness being the most severe form. Much of the tissue damage is a result of the patient’s immune reaction against Wolbachia released from the nematodes. In addition to human suffering, these conditions also result in large economic losses to already poor communities.

In each of these diseases, the afflicted carry the long-lived (5-15 years) adult nematodes (macrofilariae), which in turn produce new generations of microfilaria that are released into the blood stream. Microfilariae are then taken up by blood-sucking insects, where they develop into infective larvae. During the next insect feeding on human blood, the larvae are transmitted to new hosts, where they develop into the next adult generation. Importantly, all current anti-filarial medications are only effective against microfilariae and do not destroy the long-lived adults.

Fortunately, it was recently discovered that all human parasitic filarial nematodes but one require the symbiotic bacteria Wolbachia for fertility and adult viability and this has opened up entirely new avenues for drug development. In addition to Wolbachia‘s role in the nematode’s livelihood, these bacteria have also been found to directly contribute to disease symptoms by triggering the victim’s inflammatory immune response. In fact, disease symptoms are frequently aggravated upon medication-induced worm death, due to additional release of Wolbachia from the nematode into the host. Recently, treatment with antibiotics has been shown to increase the efficacy of traditional anthelmintics and to reduce the side effects that are attributed to the release of the symbiotic bacteria.

Despite the biomedical relevance of Wolbachia in filariasis, little is known about the mechanisms of this mutualistic symbiosis. In addition to efforts focused on the development of anti-Wolbachia based therapies, many outstanding questions remain regarding the role of Wolbachia in the filarial immune escape, survival, and fertility. In other words, the interplay between Wolbachia, the filarial nematode, and the mammalian host forming a tripartite system, remains to be better defined.

We will introduce Brugia malayi, a causative agent of human elephantiasis as a model organism, and the technical possibilities and limitations associated with research on filarial nematodes. Using combinations of RNAi and immunofluorescence experiments, our lab is interested in understanding the cell and molecular mechanisms of Wolbachia transmission during the life of Brugia. During embryogenesis, Wolbachia rely on polarity signals to asymetrically segregate into hypodermal precursors. In late larval stages, hypodermal Wolbachia show an ovarian tropism and colonize the female germcells. To better define the basis of the symbiosis, we examined cell defects in Wolbachia-depleted worms. We will report these defects, which include centrosomal and embryonic polarity defects.

Research on genetically manipulated free-living model nematodes has advanced swiftly and has resulted in a wealth of biological knowledge about basic nematode biology.  Research on parasitic worms has progressed at a slower pace due to the intricacies of maintaining complex life cycles and the inherent difficulty in genetic manipulation.  Consequently a divide has formed with little crosstalk between researchers of pathogenic and free-living nematodes.  In 2007 the draft genome of Brugia malayi, a filarial pathogen of humans was published marking the foray of filariasis research into the genomics arena.  By then those studying C. elegans had become so advanced with respect to bioinformatics that they had created their own language, one that parasitologists have difficulty understanding.  The B. malayi genome is now being maintained on the C. elegans resource Wormbase (www.wormbase.org) and now more than ever it is crucial to familiarize the filariasis community with available bioinformatics resources so they can capitalize on the growing amount of genome, transcriptome, and proteome data that is becoming available for filarial worms.  In 2011 the FR3 was charged by its Scientific Advisory Committee to promote use of bioinformatics resources within the filariasis research community.  To that end, we have opened a dialogue between the developers of Wormbase, Nematode.net and Broad Institute to educate the filariasis community on use of their resources.  Long-term solutions such as video tutorials and a formalized Sanger Institute-sponsored workshop are in the planning but will take years to accomplish.  As a short-term solution, representatives from each of these entities put on an introductory bioinformatics workshop that coincided with the 2013 Annual FR3 Minicourse at University of Georgia and was attended by PIs, postdocs, graduate students and industry representatives.   Participants benefitted from the workshop, as did the instructors who gained an appreciation for the intricacies and technical challenges of filarial biology that will help them tailor their resources towards parasitologists.  These are the first steps to accomplishing collaborations that can benefit both parties by promoting real time face-to-face communication.  The bioinformatics workshop was sponsored by New England Biolabs and the Borroughs Wellcome Fund.

Major technical and conceptual problems that C. elegans community might be able to address:

1. Bringing parasitic nematode researchers up to speed on using bioinformatics tools such as Wormbase.
2. Reliable methods of transgenesis in filarial nematodes.
3. Selectable markers for transgenesis in filarial nematodes.

As a group, neglected tropical diseases disproportionately impact impoverished and underserved communities, and particularly women and children. Morbidity associated with these diseases makes up a significant component of their burden, and has far-reaching and long-lasting consequences for those infected, affecting their ability to marry, gain an education, and earn a living. Two such diseases, caused by parasitic nematodes, are lymphatic filariasis and onchocerciasis. Individuals with lymphatic filariasis can suffer lymphedema and debilitating elephantiasis; those with onchocerciasis may experience severe skin disease and blindness. Current control methods for these diseases call for annual or bi-annual mass administration of the antihelminthics ivermectin and/or albendazole. This treatment kills the larval stages responsible for transmission and temporarily sterilizes the female adult parasites, though does not cause death of the long-lived adult stages. As a result, mass drug administration must be maintained for five to seven years in the case of lymphatic filariasis and fourteen to seventeen years in the case of onchocerciasis in order to break the transmission cycle and achieve elimination. Development of a macrofilaricide capable of killing these adult forms is needed, but technical challenges in drug discovery for these parasites have limited progress. A particular example is that the adult forms of the relevant parasite species are not readily cultivated: the difficulty in obtaining these parasites, coupled with their relatively large size, has limited the throughput of compound screening activities, and as a result, restricted the chemical space that has been explored. A broader issue is that the underlying biology related to survival of adult worms is incompletely understood, and the available tools in the native worm species are very limited. As a result, the mechanism-of-action for hits stemming from whole-organism phenotypic screens is difficult to elucidate and target-based drug discovery efforts have been limited. While use of C. elegans purely as a surrogate screening organism for discovery of antihelminthics has been explored in the past with limited success, leveraging the suite of sophisticated genetic and cellular tools and techniques developed for this organism over the past 50 years could significantly open up the biology of parasitic nematodes, as well as new, orthologous approaches for drug discovery sorely needed to accelerate discovery of macrofilaricidal agents.