de Souza Ferreira, L. C. | Search bioRxiv

bioRxiv2025

Escherichia coli-induced gut IL-33 release inhibits lung type 2 allergic responses

BackgroundThe incidence of lung allergies is reduced in countries with higher prevalence of infection and environmental exposure to microbes. However, enteric bacterial infections do not always correlate with lower incidence of allergic disorders and how lung immunity to allergens can be regulated by gut exposure to pathogens and their toxins is not fully understood. ObjectiveWe used mouse models of enterotoxigenic Escherichia coli (ETEC) infection and lung allergy to examine how gut exposure to bacteria, or their related toxins, affects allergic lung inflammation. MethodsNaive C57BL/6 mice were infected with enterotoxigenic Escherichia coli (ETEC) or orally treated with the ETEC LT toxin, to mimic enteric bacterial infections. After two weeks, these mice were treated intranasally with Ovalbumin (OVA) and Papain or IL-33, followed by challenge with OVA, to induce allergic lung inflammation that was assessed using multiple readouts. ResultsGut exposure to ETEC significantly inhibited allergic lung inflammation in a LT-dependent manner, as demonstrated by reduced tissue inflammation, less accumulation of type 2 cytokines, and reduced lung numbers of type 2 immune cells such as type 2 innate lymphoid cells (ILC2) and eosinophils. The anti-allergic capacity of LT was associated with reduced ability of lung ILC2s to recognize IL-33. Counterintuitively, deletion of either IL-33 or ILC2s significantly reverted the LT protective effect, suggesting the LT-mediated protection may occur through gut release and local sensing of IL-33. ConclusionsExposure to ETEC protects hosts against allergic lung inflammation through a negative feedback loop regulated by gut IL-33 release and sensing, suggesting a possible new immunological mechanism for reduced lung allergy incidence observed in areas with enteric bacterial infections. Key Messages- Enteric exposure to enterotoxigenic E. coli (ETEC) bacteria or its toxin LT significantly protects hosts against lung type 2 allergic inflammation. - ETEC and LT downregulate the capacity of lung ILC2s to respond to allergen-induced IL-33. - Deletion of IL-33 or ILC2s significantly impairs the protective effect of ETEC and LT, suggesting the presence of a negative feedback loop driven by toxin-induced gut IL-33 release.

immunology↗

bioRxiv2022

TLR2 axis on peripheral blood mononuclear cells regulates inflammatory responses to circulating, non-infectious immature dengue virus particles

Severe dengue virus (DENV) infection is characterized by exacerbated inflammatory responses that lead to endothelial dysfunction and plasma leakage. We have recently demonstrated that Toll-like receptor 2 (TLR2) on blood monocytes senses DENV infection leading to endothelial activation. Here, we report that non-infectious immature DENV particles, which are released in large numbers by DENV-infected cells, drive endothelial activation via the TLR2 axis. We show that fully immature DENV particles induce a rapid, within 6 hours post-infection, inflammatory response in PBMCs. Furthermore, pharmacological blocking of TLR2/TLR6/CD14 and/or NF-kB prior to exposure of PBMCs to immature DENV reduces the initial production of inter alia TNF- and IL-1{beta} by monocytes and prevents endothelial activation. However, prolonged TLR2 block induces TNF- production and leads to exacerbated endothelial activation, indicating that TLR2-mediated responses play an important role not only in the initiation but also the resolution of inflammation. Altogether, these data indicate that the maturation status of the virus has the potential to influence the kinetics and extent of inflammatory responses during DENV infection. Author SummarySevere dengue virus (DENV) infection is characterized by endothelial dysfunction leading to vascular permeability and plasma leakage. This is thought to be mediated by the exacerbated production of inflammatory mediators from cells of the innate immune system. We have previously demonstrated that Toll-like receptor 2 (TLR2), a pattern recognition receptor present on the surface of human monocytes, can sense DENV infection leading to the activation of the endothelium. Importantly, a large proportion of DENV particles is immature and are not readily infectious. Here we aimed to elucidate if and how these non-infectious immature DENV particles contribute to systemic inflammation. We evaluated if monocytes sense immature DENV and found that sensing of immature DENV induced early inflammatory responses in PBMCs. Pharmacological inhibition of TLR2/TLR6/CD14 and/or NF-{kappa}B prior to exposure to immature DENV demonstrates that this is the pathway leading to the early production inflammatory mediators and endothelial activation. However, prolonged inhibition of TLR2 induced the production of TNF- and the subsequent activation of the endothelium, suggesting that TLR2-mediated responses play an important tole during both, initiation and resolution of inflammation. We propose that the maturation status of DENV in the human host can influence the extent and kinetics of the inflammatory responses during DENV infection.

immunology↗