Host-pathogen interactions in filarial worm infections

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications, trials & patents

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 three related components: The first focuses on the interaction of Brugia malayi worms with their mammalian host; the second on the interaction of the worm with its Wolbachia bacterial endosymbiont; and the third on mechanisms of Wolbachia-mediated interference of infectious agents in insect cells. Brugia malayi-host interactions Filarial nematodes are known to interact with their hosts to modulate the immune system to sustain their persistence and to re-structure the lymphatics. This is likely performed primarily by the worm’s excretory and secretory products. According to recent findings, the parasites secrete miRNAs in mammalian host biofluids and therefore could impact pathology via these regulatory molecules. The goal is to dissect their role in parasite-host interactions and in the development of pathology in lymphatic filariasis. In FY25, we submitted for publication a study where we tested specific effects of 2 Brugia miRNAs in vitro with cultures of human lymphatic endothelial cells (hLECs). We obtained transcriptomic data of hLECs treated with miRNA-mimics and controls and revealed that these miRNAs significantly affected the genes associated with the integrity of the lymphatic endothelium. We used molecular and cellular methods including confocal microscopy to validate the effects of miRNAs on hLECs. Functional analyses confirmed that parasite miRNAs can increase leakage of hLECs in vitro. Another ongoing project involves an exciting observation from stage-specific metabolomics analyses where we discovered a few years ago novel acetylcholine analogs in the secretions of male worms. In collaboration with Dirk Trauner (now at UPenn; previously at NYU) we synthesized these acetylcholine analogs and we showed that the synthetic compounds affect motility of female worms and we characterized the full synthetic pathways of how these metabolites are synthesized by the worm. In FY25, we showed that the synthetic compounds inhibit microfilariae release from fertilized females, stimulate the GPCR2 acethylcholine receptor (collaboration with Eric Van Dang, LHMI/NIAID), stimulate the vascular stem cell pathway of hLECs, and impact the mouse hind leg lymphatics and lymph flow (collaboration with Dr. Heather Hickman, LIV/NIAID). Wolbachia-parasite interactions: As an alternative approach to the use of bacteriostatic antibiotics against Wolbachia to kill adult filarial worms, we have been focusing on repurposing compounds, which we hypothesized could disturb various pathways involved in the interdependency between Wolbachia and filarial worms. 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 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. One drug (Shikonin, that targets pyruvate kinase, a parasite glycolytic enzyme that provides pyruvate for the bacteria) was selected for further evaluation in an in vivo model (Litomosoides) in collaboration with Dr. Hubner (Germany). Using the drug we observed a significant reduction of Wolbachia in Litomosoides parasites. In FY25, we continued finding repurposed drugs that target chokepoints by using a computational approach. In this manner we evaluated protein-drug interactions and selected compounds with the most stable characteristics. We identified 26 new compounds (FDA-approved drugs) that we are testing in vitro against Brugia adult worms. Sixteen of the selected drugs target specifically Wolbachia enzymes, while another 10 are Brugia enzymes that are essential for symbiosis. 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. Wolbachia-mediated interference in insect cells: Wolbachia is also an intracellular symbiotic bacterium of arthropods, including mosquitos, which are major vectors of arboviruses, and sandflies (family Phlebotominae) blood-feeding insects that transmit several species of the parasitic protozoan Leishmania. As a bacterial symbiont, Wolbachia can restrict the transmission of a wide range of arboviruses by impacting the mosquito host at multiple levels (population, organism, and cell). In FY25, we continued a study on bacterial proteins that can modulate the cellular processes in mosquito cells that underlie Wolbachia-mediated interference of virus infections. We selected 10 Wolbachia proteins for this study. First, we silenced them in Wolbachia-positive mosquito cells to test suppression of bacterial-mediated interference with Zika virus. We then expressed key bacterial proteins to mimic the bacterial effect on Zika virus in mammalian and human cells. By this screen, we can adopt mRNA-based technology to produce bacterial proteins in human cells and block Zika virus infection. Leishmania transmission and infection intensity are influenced by the sandfly-associated microbial community, but little is known about how the variation in the composition of the microbiome contributes to variation in sand fly fitness and vector competence in the wild or in the laboratory. In collaboration with David Sacks (LPD) and Shaden Kamhawi (LMVR), we are characterizing the microbiomes of multiple generations of sand flies from two species, Lutzomyia longipalpis and Phlebotomus papatasi, originally collected in Brazil and Jordan, respectively, but maintained in laboratory colonies for 10+ years. Initial characterization of the bacterial microbiota revealed that the P. papatasi colony, which historically experienced a reduction in its capacity to transmit experimental infections, contains a sub-population of individuals infected with the widespread arthropod endosymbiont Wolbachia, which produces a very wide range of immunological and fitness effects in different insect hosts. As Wolbachia’s role in sand flies has not been well-characterized, we are assembling its genome, characterizing its effect on host and microbiome transcriptional profiles, and undertaking experiments to evaluate its effect on Leishmania transmission ability.