Rory Doolan

Macrophage polarization by type-2 cytokines is central to anti-helminth immunity and tissue repair. While some hallmark changes in macrophages are well-characterized and associated with protection against helminths, it is still unclear how macrophages exert their anti-helminth effects. In this context, we investigated arachidonate 15-lipoxygenase (LOX) (Alox15), a LOX well known for its role in macrophage polarization in the context of metabolic diseases, and a hallmark of type-2 macrophage (M2) human polarization. We show that in the absence of Alox15, M2 cannot trap and kill helminths. Surprisingly, expression of M2 markers was normal despite a loss of function. Instead, we found a concomitant increase in pro-inflammatory responses due to an uncontrolled activation of glycolysis. We further show that activation of Peroxisome proliferator-activated receptor-delta (PPAR-δ) by lipids downstream of docosapentaenoic acid (DPA) can restore normal glycolysis control, highlighting a novel role of lipids in the fine-tuning of the metabolic support required for optimal macrophage polarization.

Schistosomiasis remains a major global health burden, with praziquantel as the only available treatment despite limitations such as reduced efficacy against juvenile stages. Aryl hydantoins such as Ro 13-3978 (AR02) and its derivative AR102, exhibit potent in vivo activity against all major human schistosome species, yet lack direct in vitro efficacy, suggesting a host-directed mechanism. Here, we identify neutrophils as critical mediators of aryl hydantoin activity. In a murine model of Schistosoma mansoni infection, neutrophil depletion or enzymatic degradation of extracellular DNA significantly impaired drug efficacy. Using human neutrophil co-cultures, we show that schistosomes suppress extracellular trap formation (NETosis), but aryl hydantoins restore this response without directly inducing NETs. Proteomics revealed compound-dependent modulation of neutrophil activation pathways, including chromatin remodeling and degranulation, specifically in the presence of parasite-derived products. Compound effects were limited to PMA-induced NETosis, implicating a pathway downstream of ROS production. While the precise molecular target remains elusive, our findings provide key mechanistic insight into a unique host-directed anthelmintic strategy, highlighting a neutrophil-dependent mode of action that restores NETosis suppressed by schistosomes -offering a promising pathway for immunomodulatory anti-parasitic therapies.

Hookworm infections cause a neglected tropical disease (NTD) affecting ~740 million people worldwide, principally those living in disadvantaged communities. Infections can cause high morbidity due to their impact on nutrient uptake and their need to feed on host blood, resulting in a loss of iron and protein, which can lead to severe anaemia and impaired cognitive development in children. Currently, only one drug, albendazole is efficient to treat hookworm infection and the scientific community fears the rise of resistant strains. As part of on-going efforts to control hookworm infections and its associated morbidities, new drugs are urgently needed. We focused on targeting the blood-feeding pathway, which is essential to the parasite survival and reproduction, using the laboratory hookworm model Nippostrongylus brasiliensis (a nematode of rodents with a similar life cycle to hookworms). We established an in vitro-drug screening assay based on a fluorescent-based measurement of parasite viability during blood-feeding to identify novel therapeutic targets. A first screen of a library of 2654 natural compounds identified four that caused decreased worm viability in a blood-feeding-dependent manner. This new screening assay has significant potential to accelerate the discovery of new drugs against hookworms.

In Hookworm infection, neutrophils have long had the image of the villain, being recruited to the site of larval migration because of damage but participating themselves in tissue injury. With recent developments in neutrophil biology, there is an increasing body of evidence for the role of neutrophils as effector cells in hookworm immunity. In particular, their ability to release extracellular traps, or neutrophil extracellular traps (NETs), confer neutrophils a larvicidal activity. Here, we review recent evidence in this nascent field and discuss the avenue for future research on NETs/hookworm interactions.

Helminth parasites are adept manipulators of the immune system, using multiple strategies to evade the host type 2 response. In the intestinal niche, the epithelium is crucial for initiating type 2 immunity via tuft cells, which together with goblet cells expand dramatically in response to the type 2 cytokines IL-4 and IL-13. However, it is not known whether helminths modulate these epithelial cell populations. In vitro, using small intestinal organoids, we found that excretory/secretory products (HpES) from Heligmosomoides polygyrus blocked the effects of IL-4/13, inhibiting tuft and goblet cell gene expression and expansion, and inducing spheroid growth characteristic of fetal epithelium and homeostatic repair. Similar outcomes were seen in organoids exposed to parasite larvae. In vivo, H. polygyrus infection inhibited tuft cell responses to heterologous Nippostrongylus brasiliensis infection or succinate, and HpES also reduced succinate-stimulated tuft cell expansion. Our results demonstrate that helminth parasites reshape their intestinal environment in a novel strategy for undermining the host protective response.