Single-Cell #Network #Analysis Identifies CLEC4E as a Key Mediator of Proinflammatory mDC Responses in #Influenza #Infection

 

Abstract

The severity of influenza is often driven by an excessive host immune response rather than the virus itself, yet the key molecular drivers within specific immune cells remain poorly understood. While recent single-cell RNA sequencing studies have successfully identified immune populations involved, they have largely not identified the upstream drivers modulating their pro-inflammatory functions. Here we employed an integrated single-cell co-expression network to address this gap. Our analysis identified myeloid dendritic cells (mDCs) as central to pro-inflammatory response during infection. Through a multi-layered key driver analysis, we pinpointed C-type lectin, CLEC4E as a top candidate modulating this pathological inflammatory response. The role of CLEC4E was confirmed in an independent single-cell dataset from influenza-infected patients and further validated in vivo. Pharmacological inhibition of CLEC4E in a murine influenza model significantly reduced disease severity and lower viral titers in the lungs. This study not only clarifies that CLEC4E overexpression in mDCs contributes to pro-inflammatory signaling pathways influencing influenza severity but also shows the power of single-cell network approaches to uncover novel and robust therapeutic targets hidden within complex immune responses.

Competing Interest Statement

The M.S. laboratory has received unrelated funding support in sponsored research agreements from Phio Pharmaceuticals, 7Hills Pharma, ArgenX NV, Ziphius and Moderna.

Funder Information Declared

NIH Common Fund, R21AI149013, R01AI170112, U01AG088351

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.08.21.671587v1

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#Influenza virus #infection in the #lungs leads to #pancytopenia and defective immune cell differentiation program in the #thymus and bone marrow

Abstract

Exaggerated inflammation and cytokine storm are hallmark features of influenza A virus (IAV)-induced respiratory diseases. While previous studies unequivocally demonstrated the pathophysiological consequences (multiorgan failure) of IAV-associated cytokine storm, it remains unknown if IAV-induced systemic inflammation impacts the fitness and differentiation of immune cells from hematopoietic stem cells (HSCs). Our data on lethal IAV-infected C57BL/6 wildtype mice after 10 days of infection indicated reduced monocyte- and lymphocyte- counts in the peripheral blood, and overall cellularity of spleen, thymus and lymph nodes. IAV- infection resulted in increased numbers of myeloid cells, CD8+ T cells, alveolar macrophages (AVMs), CD11b+ dendritic cells (DCs) & plasmacytoid DCs (pDCs), whereas decreased frequencies of CD103+ DCs, in the lungs of IAV-infected mice. Analysis of spleen and draining lymph nodes indicated reduced absolute numbers of B cells, T cells, monocytes and DCs after 10 days of lethal IAV infection. Thymic analysis indicated perturbed T cell differentiation and bone marrow (BM) data revealed impaired DC differentiation following IAV infection. Hematopoietic stem and progenitor cells (HSPCs) studies demonstrated an imbalanced distribution of HSCs, multipotent progenitors (MPPs), myeloid progenitors and DC progenitors within the BM niche. Mechanistic studies exhibited elevated levels of systemic inflammation and altered local pro-inflammatory milieu. Molecular analyses documented elevated levels of intracellular reactive oxygen species (ROS) at all stages of HSPC differentiation and increased mass of active mitochondria in HSPC subsets. In essence, our studies provide novel insights into mechanisms through which lethal IAV-infection induces deficiencies of the innate and adaptive immune system.

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.04.22.650071v1

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The Novel #H10N3 Avian #Influenza Virus Triggers Lethal #Cytokine #Storm by Activating Multiple Forms of Programmed Cell Death in Mammalian #Lungs

Abstract

The novel H10N3 avian influenza virus (AIV) has infected four individuals since 2021 and caused severe respiratory damage, posing a significant threat to public health. However, its pathogenic mechanisms remain poorly understood. Our findings revealed that H10N3 infection induces severe lung damage and causes death in mice, even at low doses. The elevated levels of multiple pro-inflammatory factors in the bronchoalveolar lavage fluid were significantly increased during infection, displaying hallmarks of a cytokine storm. Transcriptome sequencing further revealed systematic activation of inflammation-related pathways, predicting that viral infection induces multiple forms of programmed cell death, including apoptosis, pyroptosis, and necroptosis. Protein-level validation showed that the activation of key cell death markers, including Caspase-3, GSDMD, and MLKL, significantly increased as the infection progressed, with their dynamic changes correlating strongly with the expression pattern of viral proteins. This study elucidates the central role of the synergistic effect between the cytokine storm and multiple cell death pathways in H10N3 pathogenesis. These findings not only advance our understanding of the pathogenic mechanisms of AIVs but also provide a critical theoretical basis for the development of targeted therapeutic strategies.

Source: International Journal of Molecular Sciences, https://www.mdpi.com/1422-0067/26/5/1977

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#Portimine A #toxin causes #skin #inflammation through ZAKα-dependent NLRP1 inflammasome activation

Abstract

In 2020–2021, a “mysterious illness” struck Senegalese fishermen, causing severe acute dermatitis in over one thousand individuals following exposure through drift-net fishing activity. Here, by performing deep analysis of the environmental samples we reveal the presence of the marine dinoflagellate Vulcanodinium rugosum and its associated cyclic imine toxins. Specifically, we show that the toxin PortimineA, strongly enriched in environmental samples, impedes ribosome function in human keratinocytes, which subsequently activates the stress kinases ZAKα and P38 and promotes the nucleation of the human NLRP1 inflammasome, leading to the release of IL-1β/IL-18 pro-inflammatory cytokines and cell death. Furthermore, cell-based models highlight that naturally occurring mutations in the P38-targeted sites of human NLRP1 are unable to respond to PortimineA exposure. Finally, the development and use of human organotypic skins and zebrafish models of PortimineA exposure demonstrate that the ZAKα-NLRP1 axis drives skin necrosis and inflammation. Our results exemplify the threats to human health caused by emerging environmental toxins and identify ZAKα and NRLP1 as important pharmacological targets to mitigate PortimineA toxicity.

Source: EMBO Molecular Medicine, https://www.embopress.org/doi/full/10.1038/s44321-025-00197-4

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Viral #sepsis: #diagnosis, clinical #features, #pathogenesis, and #clinical considerations

Abstract

Sepsis, characterized as life-threatening organ dysfunction resulting from dysregulated host responses to infection, remains a significant challenge in clinical practice. Despite advancements in understanding host-bacterial interactions, molecular responses, and therapeutic approaches, the mortality rate associated with sepsis has consistently ranged between 10 and 16%. This elevated mortality highlights critical gaps in our comprehension of sepsis etiology. Traditionally linked to bacterial and fungal pathogens, recent outbreaks of acute viral infections, including Middle East respiratory syndrome coronavirus (MERS-CoV), influenza virus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), among other regional epidemics, have underscored the role of viral pathogenesis in sepsis, particularly when critically ill patients exhibit classic symptoms indicative of sepsis. However, many cases of viral-induced sepsis are frequently underdiagnosed because standard evaluations typically exclude viral panels. Moreover, these viruses not only activate conventional pattern recognition receptors (PRRs) and retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) but also initiate primary antiviral pathways such as cyclic guanosine monophosphate adenosine monophosphate (GMP-AMP) synthase (cGAS)-stimulator of interferon genes (STING) signaling and interferon response mechanisms. Such activations lead to cellular stress, metabolic disturbances, and extensive cell damage that exacerbate tissue injury while leading to a spectrum of clinical manifestations. This complexity poses substantial challenges for the clinical management of affected cases. In this review, we elucidate the definition and diagnosis criteria for viral sepsis while synthesizing current knowledge regarding its etiology, epidemiology, and pathophysiology, molecular mechanisms involved therein as well as their impact on immune-mediated organ damage. Additionally, we discuss clinical considerations related to both existing therapies and advanced treatment interventions, aiming to enhance the comprehensive understanding surrounding viral sepsis.

Source: Military Medical Research, https://mmrjournal.biomedcentral.com/articles/10.1186/s40779-024-00581-0 

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