Qiang Huang

Background: Systemic inflammatory diseases including rheumatoid arthritis (RA), ankylosing spondylitis (AS), IBD and long covid share convergent multi-organ phenotypes. Long covid provides a tractable model for dissecting gut-driven mechanisms of systemic inflammation, given its defined temporal onset and treatment-naïve postinfectious context. Objective: To characterise a gut-driven mechanism of systemic inflammation in long covid and assess its cross-disease correlates in RA, AS and IBD. Design: Comparative metagenomic analyses across RA, AS, IBD and long covid cohorts. Long covid was established as a paradigm for postdysbiotic inflammatory diseases, single-cell RNA sequencing and functional studies in longitudinal human cohorts and co-infection mouse models (SARS-CoV-2 and Pseudomonas aeruginosa ) were employed to dissect cellular and molecular mechanisms. Genetic and pharmacological interventions targeting the interleukin (IL)-15-arachidonic acid (ARA) axis were validated for therapeutic efficacy. Results: Flagellated bacterial expansion defined a shared intestinal signature across all four diseases. Mechanistic studies in long covid demonstrated that flagellated bacteria activated toll-like receptor 5 (TLR5) on neutrophils, triggering the formation of neutrophil extracellular trap (NET) and IL-15 release. IL-15 subsequently stimulated macrophage ARA production. The co-infection murine model recapitulated multi-organ pathophysiology of long Covid, including pulmonary fibrosis and intestinal lymphoid aggregates. Genetic ablation of macrophage ARA synthesis or neutrophil IL-15 attenuated lung pathology, whereas gut microbiome clearance with gentamicin uniquely suppressed systemic inflammation. Conclusions: We delineate a flagellin-TLR5-IL-15-ARA axis as a candidate mechanism driving systemic inflammation in long covid. These findings position intestinal flagellin as a candidate therapeutic target and ARA as a potential biomarker for long covid, warranting prospective validation across inflammatory disease boundaries.

T cell senescence causes T cell dysfunction in tumors, but its drivers are unclear. Here we found that protein overload in the tumor microenvironment (TME) induces T cell differentiation into effector memory T cells re-expressing CD45RA (TEMRA). TEMRA cells exhibit senescent-like features, including reduced proliferative capacity and expression of senescence-associated markers. Both CD4⁺ and CD8⁺ T cells activated under high protein-to-amino-acid-ratio conditions in vitro or within TME niches underwent enhanced TEMRA differentiation. Single-cell transcriptomics showed that protein overload co-activates terminal effector and senescence programs. Mechanistically, it disrupts proteostasis by inhibiting lysosomal and proteasomal degradation, triggering a maladaptive unfolded protein response (UPR) that drives TEMRA commitment. Exogenous amino acid supplementation prevented UPR activation and TEMRA differentiation. In humanized tumors, intra-tumoral amino-acid administration reduced TEMRA accumulation, boosted T cell proliferation, and improved tumor control. Our work reveals managing proteostatic stress as a strategy to counter TEMRA generation and restore anti-tumor immunity. The online version contains supplementary material available at 10.1007/s43657-025-00309-7.

The high mortality caused by severe COVID-19 poses great challenges to the public health. However, the underlying pathogenesis of severe cases remains unclear. Here, we find that SARS-CoV-2 infection boosts CD147 inducible up-regulation in the lung tissues of virus-infected rhesus macaques coupled with down-regulated membrane-bound ACE2, which conduces to extended virus infection and severe pathological lesions. Specifically, SARS-CoV-2 infection enhances the expression of transcriptional factor aryl hydrocarbon receptor and facilitates its nucleus translocation, which causes CD147 gene transcription and its up-regulation in protein level, thereby leading to virus susceptibility of the hosts and extended virus infection. Meanwhile, SARS-CoV-2 infection triggers immune imbalance of lung tissues by promoting cell death of CD4 + T cells and B cells and mediating abnormal cell-cell communications, especially for M2 macrophages. Meplazumab, a humanized anti-CD147 antibody, effectively inhibits virus entry and cytokine level, and restores immune balance in the lung tissues of virus-infected rhesus macaque model. Importantly, we further present the cryo-EM structure of CD147-spike complex, and identify five pairs of functional residues for their interaction, which could be interrupted by Meplazumab via steric hindrance effect. Our findings provide direct evidence for CD147-SARS-CoV-2 spike interaction and uncover the pathogenesis of severe COVID-19 caused by CD147-mediated extended virus infection.