mBio最新文献

{"title":"The <i>Chlamydia trachomatis</i> effector CT226 directly engages LRRFIP1 to recruit a multiprotein complex that limits inclusion size and progeny production.","authors":"Cherilyn A Elwell, Amy Diallo, Barbara S Sixt, Jessica Sherry, Khavong Pha, Raphael H Valdivia, Oren Rosenberg, Kliment Verba, Joanne Engel","doi":"10.1128/mbio.01953-26","DOIUrl":"10.1128/mbio.01953-26","url":null,"abstract":"<p><p><i>Chlamydia</i> species secrete a unique class of effector proteins termed inclusion membrane proteins (Incs) that are translocated into the inclusion membrane and reprogram host cell processes to support intracellular growth. Using affinity purification-mass spectrometry, we previously identified an interaction between the early expressed Inc CT226 and a human multiprotein complex comprising leucine-rich repeat Flightless-I-interacting protein 1 (LRRFIP1), LRRFIP2, Flightless-I (FLII), and tropomodulin 3 (TMOD3). Here, we define the molecular basis and functional consequences of this interaction during <i>Chlamydia trachomatis</i> infection. We show that CT226 is both necessary and sufficient to recruit the LRRFIP1/2:FLII:TMOD3 (LFT) complex to the inclusion membrane. <i>In vitro</i> reconstitution with purified proteins demonstrates that the predicted coiled-coil region of CT226 directly binds the N-terminal helix of LRRFIP1. Using <i>in silico</i> structural modeling with AlphaFold-Multimer coupled with mutational validation, we identify key residues that mediate an electrostatic CT226:LRRFIP1 interaction required for LFT recruitment to the inclusion. Unexpectedly, genetic disruption of CT226 or its interaction with the LFT complex results in modest increases in inclusion size and recovery of infectious progeny late in infection, demonstrating that the CT226:LFT interaction modulates <i>C. trachomatis</i> developmental progression. Together, these findings establish the molecular basis of CT226-mediated recruitment of the LFT complex to the inclusion membrane and uncover a previously unrecognized role for this effector-host interaction at late timepoints of the <i>C. trachomatis</i> intracellular developmental cycle.IMPORTANCE<i>Chlamydia trachomatis</i> is a major cause of sexually transmitted infections and blindness worldwide. This bacterium survives by replicating inside host cells within a membrane-bound compartment, where it deploys specialized proteins to manipulate host processes. These proteins, known as inclusion membrane proteins (Incs), help organize the host-pathogen interface, but the molecular mechanisms by which many Incs engage host factors remain poorly understood. Here, we show that the Inc protein CT226 recruits a host multiprotein complex to the bacterial compartment by directly binding one of its components. Using structural modeling and targeted mutations, we define the molecular interface required for this interaction. Disruption of CT226 or its ability to engage this host complex results in modest increases in inclusion size and production of infectious progeny, suggesting a role for the CT226:host interaction in regulating <i>Chlamydia</i> intracellular development. These findings reveal how a bacterial effector can engage a host protein complex to influence the outcome of infection.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0195326"},"PeriodicalIF":5.4,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148990506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental versus clinical studies capture distinct types of relapse in tuberculosis.","authors":"Christian T Michael, Maral Budak, Philana Ling Lin, Denise Kirschner","doi":"10.1128/mbio.01977-26","DOIUrl":"10.1128/mbio.01977-26","url":null,"abstract":"<p><p>Tuberculosis (TB) remains a global health concern, as <i>Mycobacterium tuberculosis</i> (Mtb) currently infects a quarter of the world's population. Though many TB patients cure infection with short-course treatment, regimens shorter than 4 months risk post-treatment relapse. This is facilitated by the presence of granulomas, spatially heterogeneous immune structures that form during infection that harbor a caseated core that sequesters Mtb in a non-replicating state and pharmacokinetically impedes antibiotics. Typically, clinical relapse is described as TB recurrence <2 years after a misdiagnosis of cure upon treatment completion (MDxC). Comparatively, many experimental models cannot (or do not) screen for cure and examine relapse ~2 months after treatment completion. Understanding how relapse occurs, and whether it is impacted by experimental versus clinical study designs, may improve treatment. Here, we examine two hypothesized mechanisms of relapse: (i) reservoir, where treatment kills all Mtb except those in a non-replicating, diagnostically inaccessible host reservoir; and (ii) threshold, where replicating Mtb remain alive below detectable levels within a test-accessible reservoir. We use our computational model capturing whole-host Mtb infection dynamics, HostSim. Our simulations uncover rates of reported relapse correlating with how studies are performed. Experimentally, relapse is likely driven by incomplete sterilization of replicating bacteria, whereas clinical relapse is most likely driven by gradual expansion of non-replicating Mtb from caseum into granuloma cellular areas. This suggests that TB patients who relapse may best be re-treated with regimens including caseum-penetrating antibiotics, such as rifamycin-class antibiotics, and that experimental animal relapse models better translate to clinical when \"cure\" is established at treatment completion.IMPORTANCEIncomplete treatment of TB leads to risks relapse, which may occur years later. The threat of relapse is the main reason TB treatment takes 4-9 months. Predictors of relapse are not well-defined given variability in technical definitions of relapse and nuances of study designs. Here, we use biologically based computation to simulate both clinical and experimental TB relapse studies, employing multiple diagnostic tests and relapse definitions. We find that two hypothesized types of relapse, each possibly requiring different re-treatment strategies, are simultaneously at play. Simulations suggest that relapse after a \"cure\" diagnosis (most often clinical studies) is caused by reactivation of non-replicating bacteria hidden from treatment within necrotic granuloma tissue or other sites, whereas experimental systems that cannot or do not test for cure post-treatment are likely to report relapse caused by incomplete sterilization of replicating Mtb. Predictions also depend on the currently unclear relationship between bacterial burden and clinical symptoms.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0197726"},"PeriodicalIF":5.4,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148990552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Altered physiology of drug-resistant <i>Mycobacterium tuberculosis</i> restricts adaptation to host-relevant conditions and produces condition-dependent collateral vulnerabilities.","authors":"William J Jowsey, Kate R Harding, Caitlin E Cunniffe, Chen-Yi Cheung, XinYue Wang, Caitlan J Smart, Hannah R Klaus, Amanda L Peterson, Brunda Nijagal, Mark B Hampton, Gregory M Cook, Matthew B McNeil","doi":"10.1128/mbio.00244-26","DOIUrl":"10.1128/mbio.00244-26","url":null,"abstract":"<p><p>Antibiotic resistance mutations often disrupt essential cellular processes; however, the physiological consequences of these mutations under host-relevant conditions remain poorly understood in many bacterial pathogens. Here, we have used a combination of phenotypic growth assays and metabolomics to investigate how drug resistance affects the metabolism of <i>Mycobacterium tuberculosis</i> and its ability to adapt to different host-relevant conditions. This work shows that (i) the fitness costs of antibiotic resistance in <i>M. tuberculosis</i> are highly variable and can be exacerbated or alleviated depending on the media carbon source, (ii) genetically unrelated resistance mutations have overlapping phenotypes and metabolic dysregulation, (iii) the growth of bedaquiline- and rifampicin-resistant mutants was impaired on host-relevant carbon sources, and (iv) resistance mutants have condition-specific collateral antibiotic susceptibilities, with rifampicin-resistant mutants being hypersusceptible to ATP synthase inhibitors when grown under conditions that require propionate metabolism. Collectively, this study highlights how drug resistance impacts bacterial physiology and places metabolic constraints on the ability of <i>M. tuberculosis</i> to adapt to changes in host-relevant conditions. This work has major implications for our understanding of how resistance evolves within the host context and reinforces the importance of how physiological variation in <i>M. tuberculosis</i> might affect the outcomes of new treatment regimens.</p><p><strong>Importance: </strong>Mutations that provide antibiotic resistance in bacterial pathogens often disrupt key cellular processes. The effects of these disruptions on cellular physiology are poorly understood, especially within the context of a host environment. In this article, we investigated how antibiotic resistance mutations affect the ability of <i>Mycobacterium tuberculosis</i>, the causative agent of tuberculosis, to grow under host-relevant conditions. Using techniques that characterize growth and metabolism, we demonstrate that antibiotic-resistant <i>M. tuberculosis</i> can have both increased and decreased growth depending on the media carbon source, highlighting how interactions between drug resistance traits and the environment affect the ability of <i>M. tuberculosis</i> to adapt to changing conditions. We also show that unrelated antibiotic-resistant strains share similar metabolic defects, which can be exploited to improve antimicrobial susceptibility. Overall, this work demonstrates that drug resistance reshapes the physiology of <i>M. tuberculosis</i> in growth-dependent ways, having major implications for our understanding of how drug resistance evolves within the host context and for the design of new treatment strategies against antibiotic-resistant <i>M. tuberculosis</i>.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0024426"},"PeriodicalIF":5.4,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149039612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel adenovirus 19K/IX protein enhances infection by attenuating proteasomal degradation of tyrosine-ubiquitinated capsid protein IX.","authors":"Erik Schubert, Vasileios Rafail Evangelopoulos, Mårten Larsson, Tanel Punga","doi":"10.1128/mbio.01683-26","DOIUrl":"https://doi.org/10.1128/mbio.01683-26","url":null,"abstract":"<p><p>Human adenoviruses (HAdVs) are double-stranded DNA viruses that cause a wide range of diseases, including respiratory, ocular, and gastrointestinal infections. HAdVs rely extensively on alternative splicing to expand their coding capacity and regulate gene expression during infection. Using replication-competent epitope-tagged HAdV-C5 viruses, we investigated the function of a newly identified alternatively spliced viral transcript, 19K/IX, derived from the <i>E1B19K</i> and <i>pIX</i> genes. We show that the 19K/IX protein binds to and stabilizes the minor capsid protein IX (pIX), thereby attenuating its proteasomal degradation and enhancing the production of infectious viral progeny. Mechanistically, we demonstrate that pIX degradation is mediated by non-canonical ubiquitination of the conserved tyrosine residues Y14 and Y49, which confer pIX subnuclear localization and partially mediate its interaction with the PSMC3 subunit of the 26S proteasome. Collectively, our study identifies 19K/IX as a novel regulator of HAdV-C5 infection and suggests that non-canonical tyrosine ubiquitination contributes to the regulation of capsid protein IX stability.</p><p><strong>Importance: </strong>Human adenoviruses (HAdVs) are clinically important pathogens and widely used as therapeutic tools. Because of their compact genomes, HAdVs use their genetic information very efficiently through alternative pre-mRNA processing. Here, we describe and characterize 19K/IX, a novel fusion protein generated by alternative splicing of two viral genes during infection. We demonstrate that 19K/IX stabilizes capsid protein IX by preventing its degradation, revealing a previously unrecognized strategy by which HAdVs ensure efficient production of new virus particles. These findings deepen our understanding of HAdV-C5 gene regulation and protein homeostasis and highlight the functional importance of non-canonical HAdV transcripts.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0168326"},"PeriodicalIF":5.4,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149182874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"HIV-1 hijacks HGF/c-MET signaling to promote viral entry and replication in primary CD4⁺ T cells.","authors":"Shraddha Tripathi, Madeleine M Allen, Li Wu","doi":"10.1128/mbio.02090-26","DOIUrl":"10.1128/mbio.02090-26","url":null,"abstract":"<p><p>The mesenchymal-epithelial transition factor (c-MET) is a receptor tyrosine kinase best known for mediating hepatocyte growth factor (HGF) signaling in cancer, but its role in HIV-1 infection has remained unclear. Here, we identify c-MET as a host factor that promotes HIV-1 replication in CD4⁺ T cells by facilitating viral entry. HIV-1 infection upregulates both c-MET transcript abundance and receptor phosphorylation in primary CD4⁺ T cells. Genetic knockout, knockdown, or pharmacological inhibition of c-MET in CD4⁺ T cells markedly reduced HIV-1 Gag protein expression, viral production, and infectivity. Integrative analyses using RNA sequencing, flow cytometry, and HIV-1 infection and entry assays revealed that c-MET disruption decreased cell-surface expression of the HIV-1 receptor CD4 and the coreceptor CXCR4, thereby limiting viral entry and subsequent infection. In addition, c-MET disruption attenuated activation of NF-κB, STAT1/3, and MAPK signaling pathways, which are critical regulators of HIV-1 gene expression. Together, these findings demonstrate that HIV-1 exploits HGF/c-MET signaling to coordinate entry receptor availability with intracellular signaling programs that support viral replication. Our study identifies a previously unrecognized host pathway required for efficient HIV-1 infection of primary CD4⁺ T cells and highlights HGF/c-MET signaling as a potential target for host-directed anti-HIV-1 therapeutic strategies.IMPORTANCEThe hepatocyte growth factor (HGF)/mesenchymal-epithelial transition factor (c-MET) signaling pathway is a well-established regulator of cell growth, survival, and migration and has been extensively studied as a therapeutic target in cancer. However, its role in HIV-1 infection has remained unknown. In this study, we found that c-MET enhances HIV-1 infection of primary CD4⁺ T cells by facilitating viral entry. We further demonstrate that HIV-1 replication enhances HGF-dependent c-MET phosphorylation, which is required for downstream signaling. Genetic ablation or pharmacologic inhibition of c-MET reduces HIV-1 entry by decreasing expression of viral entry receptors. Moreover, c-MET inhibition or knockout disrupts activation of cellular signaling pathways, including NF-κB, JAK/STAT, and p38 MAPK. These findings reveal a previously unrecognized role for HGF/c-MET signaling in HIV-1 pathogenesis and suggest that targeting c-MET may represent a novel host-directed strategy for HIV-1 intervention.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0209026"},"PeriodicalIF":5.4,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149182884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"HMGB1-targeted anti-inflammatory rBox A gene therapy for viral airway infections and systemic inflammatory disease models.","authors":"Kari Ann Shirey, Daniel Prantner, Lynda Coughlan, Chanhee Park, Lin Zou, Wei Chao, John Joseph, Jorge C G Blanco, Stefanie N Vogel","doi":"10.1128/mbio.01819-26","DOIUrl":"10.1128/mbio.01819-26","url":null,"abstract":"<p><p>High mobility group box 1 (HMGB1) is a host-derived proinflammatory molecule released during cell injury. Elevated extracellular HMGB1 levels have been associated with disease severity. HMGB1 contributes to host influenza responses by stimulating TLR4/MD-2 signaling, amplifying lung inflammation, and tissue damage via cytokine production and leukocyte infiltration. HMGB1 also plays a central role in other inflammatory diseases, including sepsis and liver toxicity, making it both a biomarker of disease severity and a potential therapeutic target. We previously reported development of a non-replicating adenovirus (AdV) vector that carries an inflammation-inducible cassette that remains dormant in the absence of inflammation but produces recombinant HMGB1 Box A, a competitive antagonist of HMGB1, in response to inflammatory stimuli. Therapeutic treatment with AdV.C3-Tat/HIV-Box A mitigated lung and systemic inflammation in response to influenza in mice and cotton rats. Herein, we have optimized vector delivery and expanded its use in multiple models of infectious and non-infectious HMGB1-induced inflammation.</p><p><strong>Importance: </strong>Despite promising preclinical outcomes, clinical translation of high mobility group box 1 (HMGB1) or TLR4/MD-2 antagonists for inflammatory diseases has been limited by challenges of drug synthesis, dosing, delivery, and off-target effects. Recombinant Box A (rBox A) is a competitive inhibitor of HMGB1 that binds to TLR4 and disrupts HMGB1-mediated TLR4/MD-2 signaling. rBox A exhibits broad anti-inflammatory activity across multiple diseases (e.g., endotoxemia, sepsis, neuroimmune disorders, ischemia/reperfusion); however, its therapeutic utility is constrained by the need for high, repeated dosing. We have engineered a non-replicating adenoviral (AdV) vector (AdV.C3-Tat/HIV-Box A) that produces recombinant (r)Box A when \"sensed\" by an inflammation-responsive complement C3 (C3) promoter. Therapeutic administration of AdV.C3-Tat/HIV-Box A resulted in significant protection and reduced inflammation in multiple HMGB1-mediated disease models, advancing a first-in-class, broadly applicable, host-directed gene therapy that selectively disrupts HMGB1-TLR4 signaling and has potential as both a broad-spectrum therapeutic for HMGB1-driven inflammatory diseases and a rapid-response countermeasure against emerging respiratory pathogens.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0181926"},"PeriodicalIF":5.4,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148808801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Purine and pyrimidine analogs differentially regulate cell wall precursor biosynthesis to control β-lactam susceptibility in methicillin-resistant <i>Staphylococcus aureus</i>.","authors":"Aaron C Nolan, Sarah Byrne, Merve S Zeden, James P O'Gara","doi":"10.1128/mbio.01274-26","DOIUrl":"10.1128/mbio.01274-26","url":null,"abstract":"<p><p>Maintaining the efficacy of β-lactam antibiotics against <i>Staphylococcus aureus</i> is a clinical priority given the prevalence of methicillin-resistant <i>S. aureus</i> (MRSA). We previously showed that the pyrimidine analogs 5-fluorouracil (5-FU) and 5-fluorouridine (5-FUrd) synergize with β-lactams. Here, we extended this by evaluating additional nucleotide metabolism-targeting agents. Gemcitabine (Gem) and mitomycin C (Mito), such as 5-FU and 5-FUrd, exhibited intrinsic anti-MRSA activity and potentiated β-lactams, whereas the purine analog 6-thioguanine (6-TG) showed distinct, often antagonistic effects. Transcriptomic analysis revealed that pyrimidine-targeting agents repress lysine and glutamate biosynthesis, while 6-TG induced these pathways, implicating amino acid metabolism in β-lactam potentiation. Consistent with this, pyrimidine analogs also suppressed GlmS expression, potentially limiting UDP-GlcNAc production required for cell wall synthesis, and synergized with fosfomycin. Fluorescence microscopy confirmed that the potentiation of oxacillin activity by pyrimidine-targeting agents, but not 6-TG, was accompanied by impaired peptidoglycan synthesis. Additionally, glutathione-mediated attenuation of killing implicated reactive oxygen species in the bactericidal activity of cloxacillin combinations. Finally, these agents displayed strong antibiofilm activity, further enhanced in combination with daptomycin and rifampicin. Together, these findings highlight the potential of pyrimidine analogs to potentiate cell wall-targeting antibiotics and identify an important role for modulation of cell wall precursor pathways in this anti-MRSA activity.</p><p><strong>Importance: </strong>Drug interactions can complicate the treatment of antimicrobial-resistant infections in patients undergoing treatment for cancer, highlighting the importance of understanding the effects of anticancer drugs on pathogens such as MRSA. Here, we investigated several drugs that target nucleotide metabolism and are used to treat cancer, fungal, and viral infections, both alone and in combination with commonly used penicillin-type antibiotics. We found that pyrimidine analog drugs enhanced the activity of these antibiotics against MRSA, whereas the purine analog 6-thioguanine reduced antibiotic effectiveness. These drugs altered the bacterial cell wall and other metabolic pathways linked to antibiotic susceptibility. Our findings reveal the potential to repurpose certain anticancer drugs to improve treatment of MRSA infections while also cautioning that some drug combinations may interfere with antibiotic therapy.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0127426"},"PeriodicalIF":5.4,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148906753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of the polysaccharide capsule as a novel virulence-associated trait of <i>Stenotrophomonas maltophilia</i> complex bacteria.","authors":"Laurita Klimkaitė, Aleksandras Konovalovas, Jūratė Skerniškytė, Dukas Jurėnas, Asta Mačionienė, Silvija Kiverytė, Julija Armalytė","doi":"10.1128/mbio.01635-26","DOIUrl":"10.1128/mbio.01635-26","url":null,"abstract":"<p><p>The polysaccharide capsule is recognized as a major virulence factor of many bacterial pathogens, playing a significant role in evading host immunity. However, it has not yet been characterized for the bacteria within the emerging multidrug-resistant opportunistic pathogens of the <i>Stenotrophomonas maltophilia</i> complex. In this study, we aimed to evaluate whether bacteria of the <i>S. maltophilia</i> complex form a bona fide polysaccharide capsule and determine its virulence-related functions. We demonstrated that a part of clinical and environmental isolates of the <i>S. maltophilia</i> complex forms a polysaccharide capsule and identified a distinct group IV-like, Wzx/Wzy-dependent capsule-associated locus architecture in these bacteria, with capsule-associated genes organized within one or two loci. Comparison of capsulated clinical isolates and their capsule-deficient mutants showed that the polysaccharide capsule protects bacteria of the <i>S. maltophilia</i> complex from blood plasma-mediated killing, phagocytosis, and desiccation. However, formation of the polysaccharide capsule can also limit biofilm formation and adhesion to epithelial cells in some isolates, suggesting a potential trade-off for the bacteria. Altogether, our results pinpoint the polysaccharide capsule as one of the previously undescribed virulence-associated factors of the <i>S. maltophilia</i> complex, enhancing its ability to escape host innate immunity mechanisms and contributing to pathogenicity.IMPORTANCEThe emerging pathogens employ a variety of diverse virulence strategies, which must be thoroughly investigated to uncover effective ways of preventing and combating their infections. In this work, emerging multidrug-resistant bacterial pathogens belonging to the <i>Stenotrophomonas maltophilia</i> complex were analyzed, with the goal of identifying their mechanisms responsible for evasion of the host immune system. A polysaccharide capsule, a previously uncharacterized virulence-associated trait of <i>S. maltophilia</i> complex bacteria, was identified and characterized in this work, revealing both the genetic factors required for its synthesis and its biological importance to the bacteria. This work expands our understanding of the survival strategies of emerging multidrug-resistant bacteria.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0163526"},"PeriodicalIF":5.4,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148945198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sex and age differences in antibody responses to seasonal influenza vaccination are mediated by estrogenic upregulation of NF-κB and TNF signaling in B cells.","authors":"Han-Sol Park, Anna Yin, Weiqiang Zhou, Eliane F E Wenstedt, Anne Jedlicka, Amanda Dziedzic, Annie Werner, Katherine Z J Fenstermacher, Huifen Li, Patrick J Shea, John S Lee, Patricia Gearhart, Robert W Maul, Sjoerd A A Van Den Berg, Richard E Rothman, Hongkai Ji, Sean X Leng, Andrew Pekosz, Sabra L Klein","doi":"10.1128/mbio.01435-26","DOIUrl":"10.1128/mbio.01435-26","url":null,"abstract":"<p><p>Sex differences in the humoral immune responses to the seasonal quadrivalent influenza vaccine (QIV) in young adults (YA; 18-49 years old) or high-dose QIV in old adults (OA; 75+ years old) were analyzed to determine how age-related changes, including in steroids, impact sex differences in B cells. Among YAs, females had greater H3N2, but not H1N1, neutralizing antibody titers, and greater proportions of hemagglutinin (HA)+ CD19+ B cells and HA+ memory B cells than males through 28 days post-vaccination (DPV), that was not observed among OAs. Machine learning algorithms illustrated that baseline (0 DPV) steroids, including 17-hydroxyprogesterone, estrogens, and testosterone, as well as HA+ CD19+ B cells and HA+ antibody-secreting B cells (ASCs), were major predictors of seroconversion at 28 DPV, particularly in YA. Single-cell RNA sequencing demonstrated that CD19+ B cells from YA females had greater transcriptional activity at 7 DPV than YA males, with upregulation of genes with estrogen-response elements (EREs) along NF-κB-mediated TNF signaling pathways in B-cell subsets, which was mitigated in OA. Estradiol treatment of ASCs from YA females, but not males, increased the number and size of HA+ IgG+ cells and expression of ERE genes along the NF-κB-mediated TNF signaling pathway,that was inhibited by an estrogen receptor antagonist. Pharmacological inhibition of either NF-κB or TNF signaling blocked the ability of E2 to upregulate antibody secretion in cells from YA females. This study provides mechanistic insights into estrogen-mediated increases in influenza vaccine-induced antibody responses among reproductive-aged females and suggests a role for estrogen signaling in the reduction of sex differences in vaccine-induced immunity with old age.</p><p><strong>Importance: </strong>Sex differences in influenza vaccine-induced immune responses become less pronounced with old age, which we hypothesize could be related to changes in circulating gonadal steroids. Our study shows that after receipt of the seasonal influenza vaccine, young adult females, who have elevated estrogenic activity, have more B cells that recognize influenza hemagglutinin; their B cells have greater activity along estrogen signaling and inflammatory pathways, and mount stronger antibody responses than young adult males, with these sex differences being mitigated in old adults. We identify estrogen as a key driver of sex differences in influenza immunity by showing that <i>ex vivo</i> estradiol increases antibody production by B cells through the estrogen receptor and engagement with NF-κB. These findings help explain the biological basis for sex differences in vaccine immunity and suggest that the hormonal environment, not just chronological age, shapes how well a person responds to vaccination.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0143526"},"PeriodicalIF":5.4,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148920255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The E3 ubiquitin ligase IDOL suppresses PRRSV replication by targeting viral Nsp3 for SQSTM1-mediated selective autophagic degradation.","authors":"Jiecong Yan, Yuhan Wu, Huirui Xu, Pengning Lai, Ling Huang, Zhan He, Yongsheng Xie, Chunhe Guo","doi":"10.1128/mbio.01534-26","DOIUrl":"10.1128/mbio.01534-26","url":null,"abstract":"<p><p>Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most devastating pathogens affecting the global swine industry. Autophagy plays an important role in both host defense and PRRSV infection. However, the mechanisms by which the host exploits the autophagy pathway to antagonize PRRSV infection remain largely unknown. Here, we perform transcriptomic analysis of porcine alveolar macrophages isolated from PRRSV-infected piglets and reveal a significant upregulation of the mRNA levels for the E3 ubiquitin ligase IDOL. These findings are further validated by <i>in vitro</i> experiments. Functional studies reveal that IDOL acts as a host restriction factor for PRRSV: ectopic expression of IDOL markedly suppresses viral replication, while knockdown of endogenous IDOL enhances it. Mechanistically, IDOL catalyzes K63-linked polyubiquitination of the viral nonstructural protein 3 (Nsp3) at lysine 101 (K101) and recruits the selective autophagy receptor SQSTM1, thereby targeting Nsp3 for degradation via the autophagy-lysosomal pathway and effectively suppressing viral replication. Notably, the ubiquitin-associated and LC3-interacting region domains of SQSTM1 are essential for this autophagic clearance of Nsp3. Furthermore, using a reverse genetics approach, we generate an Nsp3 K101R mutant virus and confirm that this specific mutation enables the virus to evade IDOL-mediated Nsp3 degradation, thereby restoring its replication competence. In summary, we uncover an autophagy-dependent antiviral mechanism, establish IDOL as an innate immune regulator with a non-canonical function, and define a viral immune evasion strategy, positioning IDOL as a promising therapeutic target for PRRSV control.IMPORTANCEPorcine reproductive and respiratory syndrome virus (PRRSV) represents a major threat to global swine production, inflicting substantial economic damage and endangering food security. Here, we identify the E3 ubiquitin ligase IDOL as a critical host restriction factor that combats PRRSV through a previously unrecognized autophagy-mediated mechanism. We demonstrate that PRRSV infection robustly upregulates the transcription factor ZNF460, which directly drives IDOL expression. During PRRSV infection, IDOL drives the autophagic degradation of Nsp3 by catalyzing its K63-linked ubiquitination at lysine 101 and engaging the selective autophagy receptor SQSTM1, triggering a potent antiviral response. Using reverse genetics, we generate an Nsp3 K101R mutant virus and demonstrate that this mutation enables the virus to escape IDOL-mediated degradation and restore replication competence, providing genetic validation of this antiviral axis. Collectively, our findings establish an autophagy-dependent antiviral mechanism, define IDOL as an intrinsic immune regulator with a previously unrecognized function, and elucidate a precise viral immune evasion strategy, thereby positioning IDOL as a promising therapeutic target for PRRSV intervention.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0153426"},"PeriodicalIF":5.4,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148969976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}