Biology subjects

Hayek, I.

Publications and source records attributed to Hayek, I..

4 recordsLinked to original sources

bioRxiv2026

Preserved Type 2 Immune Cell Plasticity in Human Obesity and Differential Immune Reconstitution After Bariatric Surgery

BackgroundObesity disrupts type 2 immune cell populations in white adipose tissue, replacing the homeostatic network of group 2 innate lymphoid cells (ILC2s), eosinophils, T helper 2 (Th2) cells, and alternatively activated macrophages (AAMs) with pro-inflammatory type 1 populations. Whether this remodelling reflects permanent immune impairment or a reversible shift in cellular equilibrium, and to what extent bariatric surgery restores type 2 immunity, remain incompletely understood. MethodsWe performed comprehensive immunophenotyping of visceral white adipose tissue (WAT) and peripheral blood from persons with severe obesity (people with obesity, PWO) scheduled for or having undergone bariatric surgery (sleeve gastrectomy, gastric bypass), combined with lean controls. Using flow cytometry, quantitative PCR, and in vitro polarization assays, we assessed immune cell frequencies, transcription factor expression, cytokine profiles, and functional polarization capacity across lean, pre-operative, and post-operative states. ResultsObesity was associated with decreased eosinophil and CD8+ T cells frequencies in WAT, accompanied by an increase in CD4+ frequency and a shift from Th2 toward Th1 predominance, as well as elevated PD-1 expression on T cell subsets. Bariatric surgery partially normalised peripheral immune cell composition, reducing CD8+ T cell frequencies while increasing CD4+ T cells. Macrophage polarization capacity, dampened in pre-operative PWO, recovered after surgery. Conversely, Th2 polarization capacity and IL-13 production were reduced in post-operative T cells despite preserved function pre-operatively, indicating divergent trajectories of innate and adaptive immune reconstitution. ConclusionType 2 immune cells retain functional plasticity in human obesity despite reduced frequency. Bariatric surgery differentially reconstitutes immune function, restoring macrophage plasticity while paradoxically reducing Th2 polarization capacity, arguing against uniform immune normalisation after weight loss. FundingGerman Federal Ministry of Research, Technology and Space (BMFTR, FKZ 01KI2109), Interdisciplinary Center for Clinical Research (IZKF, Faculty of Medicine, Friedrich-Alexander Universitat (FAU) Erlangen-Nurnberg).

immunology↗

bioRxiv2026

Obesity selectively disrupts long-lasting type 2 immune cell depots in white adipose tissue

White adipose tissue (WAT) has emerged as a tissue-resident niche for immunological memory, but whether this depot function extends to type 2 immune memory and how it is modulated by metabolic disease remains incompletely understood. Here, we show that Nippostrongylus brasiliensis infection, in which the parasite transits and damages the lung, establishes a long-lasting immune cell depot in distal abdominal WAT comprising eosinophils, group 2 innate lymphoid cells (ILC2s), and memory T cells that persists after parasite clearance. Intranasal papain administration recapitulates this depot phenotype, demonstrating that depot formation is a general feature of pulmonary type 2 inflammation rather than a response restricted to live infection. Adoptive transfer of OT-II T cells together with ovalbumin-coated N. brasiliensis larvae confirms that WAT accumulates bona fide antigen-experienced T cells. Diet-induced obesity selectively disrupts depot establishment, while leaving acute lung-stage immune cell recruitment, parasite clearance, and the intrinsic competence of cells that do accumulate largely intact. Despite preserved early lung recruitment, obese mice show exacerbated peri-alveolar tissue damage, consistent with an uncoupling of immune cell infiltration from productive type 2-dependent wound repair. Together, these findings establish WAT as a broadly competent type 2 immunological memory niche, identify obesity as a selective disruptor of depot formation rather than effector function, and provide a cellular framework for the impaired vaccine and infection responses associated with obesity.

immunology↗

bioRxiv2025

Coxiella burnetii establishes a small cell variant (SCV)-like persistent form to survive adverse intracellular conditions

Coxiella burnetii is an obligate intracellular zoonotic bacterium that causes Q fever. Infections can be either acute or chronic. Of note, chronic Q fever develops months or years after primary infection without clinical symptoms, suggesting bacterial persistence. Yet, information about the induction, regulation and/or location of C. burnetii persistence is rare. We have shown that during infection of primary macrophages, hypoxia-induced citrate limitation results in inhibition of C. burnetii replication without affecting viability. Here, primary murine macrophages were infected with C. burnetii under normoxic (21% O2) and hypoxic (0.5% O2) conditions to clarify how C. burnetii survives this environmental stress condition. Our data suggests that under hypoxic conditions C. burnetii does not undergo stringent response, but instead enters a SCV-like form, which is smaller in size and possesses condensed chromatin material and a thicker cell wall. These changes have functional consequences, as the SCV-like persistent form of C. burnetii is more infectious, more tolerant to antibiotics and less sensitive to clearance by IFN{gamma} activated macrophages. Hence, the development of the SCV-like persistent form of C. burnetii prevents elimination of the pathogen, which in turn allows the pathogen to thrive once the conditions again change in its favor.

microbiology↗

bioRxiv2022

Macrophages inhibit Coxiella burnetii by the ACOD1-itaconate pathway for containment of Q fever

Infection with the intracellular bacterium Coxiella (C.) burnetii can cause chronic Q fever with severe complications and limited treatment options. Here, we identify the enzyme cis- aconitate decarboxylase 1 (ACOD1 or IRG1) and its product itaconate as protective host immune pathway in Q fever. Infection of mice with C. burnetii induced expression of several anti-microbial candidate genes, including Acod1. In macrophages, Acod1 was essential for restricting C. burnetii replication, while other antimicrobial pathways were dispensable. Intratracheal or intraperitoneal infection of Acod1-/- mice caused increased C. burnetii burden, significant weight loss and stronger inflammatory gene expression. Exogenously added itaconate restored pathogen control in Acod1-/- mouse macrophages and blocked replication in human macrophages. In axenic cultures, itaconate directly inhibited growth of C. burnetii. Finally, treatment of infected Acod1-/-mice with itaconate efficiently reduced the tissue pathogen load. Thus, ACOD1-derived itaconate is a key factor in the macrophage-mediated defense against C. burnetii and may be exploited for novel therapeutic approaches in chronic Q fever.

immunology↗