Host-pathogen interactions in filarial worm infections

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

Neglected tropical diseases caused by parasitic nematodes such as the filarial parasite Brugia malayi, a causative agent of lymphatic filariasis, also known as elephantiasis, remain a leading cause of morbidity and a significant health burden in the developing world. The continued lack of effective vaccines and the limited outcomes of mass drug administration efforts highlight the need for non-traditional therapeutic approaches. Such approaches require a deeper understanding of the underlying biology of parasitism and a clear definition of the host-parasite interface. This project is divided into two related components: one aspect focuses on the interaction of Brugia malayi worms with their mammalian host, and the other on the interaction of the worm with its Wolbachia bacterial endosymbiont. We have integrated transcriptomic, proteomic, and glycomic platforms to define the stage and sex-specific secretomes, the primary host-parasite interface of B. malayi, and characterized protein glycosylation. We are further analyzing these data to better characterize the glycome potential in immunomodulation. In our current experiments we investigate how male and female worms interact with the host lymphatic system and the immune system. Through global metabolomics studies of B. malayi worms at different life stages and of the secretome from cultured worms, we have identified sex-specific metabolites that are novel short chain fatty acids that appear to be exclusively secreted by male worms. Furthermore, when male worms are cultured with Doxycycline, expression of these metabolites increases by 2-fold. We synthesized branched versions of the identified short chain fatty acid and determined that there are two different molecules being expressed: isovalerylcholine and 2-methylbutyrylcholine. Using an inhibitor of acetyl-choline esterase, we identified by metabolomics the complete pathway that corresponds to the synthesis of these metabolites. We are evaluating the effects of synthesized versions of these metabolites on the transcriptional program of lymphatic epithelial cells, and on the motility of the worms. According to recent findings, parasites secrete their miRNAs in mammalian host biofluids and therefore may cause pathology through these regulatory molecules. We initiated studies where we intend to validate how Brugia miRNAs are involved in causing pathology of lymphatic filariasis in human. This project also evaluates how Wolbachia impact the regulation of host (filarial nematode) genes, how they obtain essential metabolites for their survival, and how they evade the hosts intracellular immune defenses. Wolbachia are common intracellular bacteria found in arthropods and filarial nematodes. The association between filarial worms and their mutualistic and obligatory endosymbionts is different from that of Wolbachia with insects: in worms they appear to provide crucial elements for fitness and survival, whereas the insects are mostly viable without Wolbachia. We are evaluating how Wolbachia change the transcriptional profile of the host cells they infect. We predicted 73 chokepoints, i.e. parasite and Wolbachia enzymes that are essential for symbiosis. We screened 6 drugs that target 4 chokepoints in the in vitro model and one drug (that targets pyruvate kinase, a parasite glycolytic enzyme) was selected for further evaluation in an in vivo model (Litomosoides) in collaboration with Dr. Hubner (Germany). We have identified miRNAs that are differentially regulated in response to Wolbachia disruption in B. malayi worms, and we are testing miRNAs identified as differentially expressed in mosquito cell lines with or without Wolbachia. We have identified chemical compounds that induce autophagy in nematodes, and are testing their ability to eliminate Wolbachia in adult worms in an in vivo model (B. pahangi in gerbils) in collaboration with Dr. Lustigman (NYC, USA). More recently we developed in collaboration with Dr. Giacomello (SciLife Labs) a spatial transcriptomics approach on small tissues such as a section of B. malayi adult female worms. In situ we are able to determine the expression of Brugia genes in different tissues of the worm. Moreover, using a co-expression technique we were able to compare expression of Brugia genes in Wolbachia vs Wolbachia-free worm tissues in situ. It allows to further investigate mechanisms of endosymbiosis between bacteria and worm tissues/cells. Probing the mechanisms of interaction of the filarial worm Brugia malayi with its bacterial symbiont, Wolbachia, and of the worm with its host will give insight into the unique biology of this family of important pathogens. This could better inform novel therapeutic strategies.