PLOS Pathogens

Kaposis Sarcoma Herpesvirus (KSHV), an enveloped double-stranded DNA virus, is the etiological agent of Kaposis sarcoma (KS), an endothelial cell-based tumor. KSHV is a leading cause of infection-related cancers in sub-Saharan Africa and immunocompromised individuals worldwide. Therefore, it is vital to identify the underlying mechanisms of viral infection and transmission to effectively identify specific therapeutic strategies and combat the disease. Here, we demonstrate that KSHV rewires the host cell lipidome during lytic infection. Bulk lipidomic analysis shows significant changes in the abundance of neutral lipids and phospholipids during lytic infection. We further investigated fatty acid-binding proteins (FABPs) to understand the underlying mechanisms that support KSHV pathogenesis. Using the doxycyclin-inducible iSLK.BAC16 cell line, we find that FABP genes are differentially regulated by lytic KSHV infection compared to latent infection. We report that FABP4 is significantly upregulated during lytic infection. Loss of FABP4 during lytic infection does not impact viral gene transcription however, lytic protein translation is reduced. Moreover, our intracellular and extracellular viral titers indicate that FABP4 affects maximal infectious virion production. This study highlights the role of FABP4 and its therapeutic potential as a target that facilitates KSHV infection and pathogenesis.

We previously reported that the oxidative stress sensor Kelch-like ECH-associated protein 1 (Keap1) recognizes hepatitis B virus (HBV) X protein (HBx) to activate the NF-E2-related factor 2 (Nrf2) signaling pathway, thereby inhibiting HBV replication, and that HBx promotes K6-linked polyubiquitylation of Nrf2. However, the molecular mechanism remains unclear. Here, we investigated the role of HECT, UBA, and WWE domain-containing E3 ubiquitin ligase 1 (HUWE1) in HBx-mediated K6-linked polyubiquitylation of Nrf2 and its impact on HBV replication. Cell-based ubiquitylation assays demonstrated that HUWE1 knockdown reduced HBx-mediated K6-linked polyubiquitylation of Nrf2, while overexpression of wild-type HUWE1, but not the catalytically inactive HUWE1(C4341A) mutant, enhanced it, indicating that HUWE1 E3 ligase activity is required. Coimmunoprecipitation and proximity ligation assays demonstrated that HUWE1 interacts with HBx in the cytoplasm and binds Nrf2 only in the presence of HBx, suggesting that HBx bridges HUWE1 and Nrf2 into a ternary complex. Cycloheximide chase assays demonstrated that HUWE1 knockdown destabilized Nrf2 in HBx-expressing cells, supporting a role for HUWE1 in Nrf2 stabilization via K6-linked polyubiquitylation. Furthermore, HUWE1 knockdown or treatment with the HUWE1 inhibitor BI8626 significantly increased HBV RNA and pgRNA levels in HBV-infected cells. Collectively, these results demonstrate that HUWE1 promotes K6-linked polyubiquitylation and stabilization of Nrf2 in an HBx-dependent manner to inhibit HBV replication. IMPORTANCEHepatitis B virus (HBV) chronically infects approximately 254 million people worldwide, yet host mechanisms that restrict viral replication remain incompletely understood. The Kelch-like ECH-associated protein 1 (Keap1)/ NF-E2-related factor 2 (Nrf2) signaling pathway is a central defense against oxidative stress. Under basal conditions, Nrf2 is degraded via Keap1/Cullin3-mediated K48-linked polyubiquitylation. We previously demonstrated HBV infection promotes Nrf2 stability through non-canonical K6-linked polyubiquitylation. Here, we identify the E3 ubiquitin ligase HUWE1 as the enzyme responsible for K6-linked polyubiquitylation of Nrf2. HBV X protein (HBx) recruits HUWE1 to Nrf2, forming a HUWE1/HBx/Nrf2 complex that switches Nrf2 ubiquitylation from K48 to K6, stabilizing Nrf2 and suppressing HBV replication. These findings reveal a novel antiviral mechanism exploiting a non-canonical ubiquitin code and highlight HUWE1 as a potential therapeutic target against chronic HBV infection.

Orientia tsutsugamushi (Ot) is an obligately intracellular bacterium that causes scrub typhus, a potentially severe infectious disease characterized by systemic inflammation and multiorgan dysfunction. We recently reported a protective role for IFN-{gamma} signaling in host defense against Ot infection; however, the underlying mechanisms remain obscure. Inducible nitric oxide synthase (iNOS, encoded by Nos2) is a key antimicrobial effector induced downstream of IFN-{gamma} signaling. Here, we used transgenic mouse models to further investigate the biological functions of iNOS. We first revealed the requirement of iNOS for the restriction of Ot growth in cultured bone marrow-derived macrophages. Using an intradermal mouse model, we found that while tissues of Nos2-/- and wild-type mice exhibited comparable bacterial burdens during acute infection phases, Nos2-/- mice developed eschar-like lesions similar to those observed in Ifngr1-/- mice, indicating a critical role for the IFN-{gamma}/iNOS axis in regulating skin pathology in scrub typhus. Notably, Nos2-/- mice displayed impaired bacterial clearance during the recovery phase (day 42), with persistent bacterial burdens in multiple organs accompanied by sustained immune activation and elevated inflammatory responses. Histopathological and biochemical analyses further revealed increased tissue damage and dysregulated physiological homeostasis in Nos2-/- mice during recovery. Mechanistically, iNOS deficiency resulted in heightened myeloid cell activation and prolonged expression of proinflammatory mediators, suggesting a dual contribution of iNOS in both antimicrobial defense and inflammation resolution. Collectively, these findings provide new insight into IFN-{gamma}-mediated defense mechanisms and imply the distinct roles of iNOS during different stages of scrub typhus. Author summaryScrub typhus is a potentially severe infectious disease caused by the bacterium Orientia tsutsugamushi (Ot), which is transmitted to humans through the bite of infected mites. Despite its global impact and expanding geographic distribution, the immune mechanisms that protect against this infection remain incompletely understood. In this study, we examined the role of inducible nitric oxide synthase (iNOS), an immune effector molecule that helps the host control infection. Using mouse models, we found that iNOS plays dual and stage-specific roles during Ot infection. Mice lacking iNOS developed dysregulated immune homeostasis during acute infection and exhibited skin lesions resembling the eschars observed in some patients with scrub typhus. In addition, these mice showed delayed bacterial clearance, prolonged inflammation, and increased tissue damage during the recovery phase. Our findings indicate that iNOS contributes not only to host antimicrobial defense but also to the control of excessive inflammation following infection. These results provide new insight into host defense mechanisms in scrub typhus and may help inform future therapeutic or preventive strategies.

The ability of the bacterial endosymbiont Wolbachia pipientis to block arboviruses in its mosquito host may be impinged by host genetic variation, leading to reduced efficacy in field releases. Across a large collection of Drosophila lines carrying natural genetic variation, we found that viral replication varied greatly in the absence of Wolbachia. However, the introduction of the symbiont reduced viral load in each background to similar levels, near the limit of detection. Therefore, Wolbachia-mediated viral blocking is seemingly robust against host genetic background. A genome-wide association study harnessing the variation in the viral loads across the Wolbachia-free set identified rhoGAP18B and betaCOP as host factors that contribute to SINV replication; furthermore, the gene products of which seemingly interact with each other in the context of cytoskeletal dynamics. These results shed light on host requirements for SINV replication and suggest possible avenues by which Wolbachia may encroach upon them during blocking.

HIV escapes sterilizing immunity through a variety of mechanisms, including the downregulation of MHC-I expression by HIV Nef and Vpu to counteract CD8+ T cell responses. While reduced MHC-I expression would be expected to support targeting by NK cells, a subpopulation of infected CD4+ T cells consistently resists multiple rounds of NK cell natural and antibody-dependent cytotoxicity. Studies further reveal that the HIV accessory protein Vpr induces expression of TNFRSF10B (TRAIL-R2) in CD4+ T cells, with survivors of NK cell targeting exhibiting relatively higher MHC-I and weaker expression of TRAIL-R2. In fact, reverse TRAIL signaling in NK cells leads to the release of perforin and granzymes, a pathway limited when TRAIL-R2 expression is diminished. Thus, independent of canonical death receptor signaling, TRAIL-R2 serves as an activating ligand that augments NK cell killing. These observations demonstrate that through Vpr, HIV can regulate the TRAIL/TRAIL-R2 axis to control NK cell functionality.

Chronic periapical periodontitis (CAP), highly prevalent worldwide, has long been regarded as non-specific inflammation. Lipophilic Cutibacerium acnes (CA) persistence in host macrophages has emerged as the pathologic background of sarcoidosis and acne vulgaris. Here we report that intracellular persistence of CA in TREM2-macrophages plays a pathologic role in CAP. We observed persistent CA in macrophages in most CAP samples. Our CA clinical isolates persist in the cytosolic space of macrophages, retarding phagolysosomal degradation accompanied by NLRP3-dependent inflammatory response. Subcutaneous injection of those isolates in vivo recapitulates subcutaneous aggregation of CA-laden macrophages. By single cell RNA sequencing analysis of defined CAP samples, we found that CA in TREM2-macrophages drives exuberant lipid droplets formation, indicating that immune cells are potential lipid provider in CAP. Our observations elucidate the mechanistic link whereby TREM2-macrophages and altered lipid metabolism provide a lipid-rich niche for CA, contributing to the pathophysiology of CAP.

The type VI secretion system (T6SS) is a contractile nanoweapon widely employed by Gram-negative bacteria to gain competitive advantages by injecting effector proteins into recipient cells. Although the biochemical activities of T6SS effectors have been well characterized, how recipient factors modulate effector toxicity remains poorly understood. Using Agrobacterium C58 as a model, previous work identified the Escherichia coli ClpAP protease as a recipient susceptibility (RS) factor that enhances T6SS-mediated interbacterial competition. Agrobacterium C58 deploys two DNase effectors, Tde1 and Tde2, as the major antibacterial weapon. Here, we demonstrate that the recipient ClpAP protease and its adaptor ClpS enhanced C58-mediated interbacterial competition in a Tde2-dependent manner in both intra- and interspecies competition. Ectopic expression of Tde2 in E. coli caused growth inhibition and DNA cleavage in the presence of a functional ClpAPS protease complex, but not in any of the clpP, clpA or clpS mutants. Notably, Tde2 accumulated in these mutants but not in wild-type cells, whereas a catalytic variant accumulated regardless of ClpAPS status, suggesting that Tde2 is not directly degraded by ClpAPS. Instead, Tde2 depends on ClpAPS for full toxicity, likely through degradation of inhibitory N-degron substrate(s). Affinity purification of His-tagged Tde2 in a clpP mutant background, followed by mass spectrometry, identified eight N-degron substrate candidates. Tde2-mediated interbacterial competition was significantly reduced by overexpression of three candidates. Among them, the Tde2 DNase domain directly associated with guanosine 5-monophosphate reductase GuaC, supporting a model in which Tde2 toxicity is blocked by binding of GuaC. Collectively, our findings reveal an unanticipated layer of recipient-mediated regulation in T6SS competition and highlight proteolytic control of inhibitory substrates as a determinant of bacterial susceptibility during interbacterial conflict.

The majority of emerging infectious diseases are zoonotic, having their origin in wildlife before spilling over into the human population. While small mammals are recognized as critical reservoirs for these viruses, their viral diversity remains largely uncharacterized across many African countries. We conducted molecular surveillance of synanthropic rodents and shrews in the Kibera informal settlement in Nairobi and the rural Taita Hills region of Kenya to detect and characterize potential zoonotic viruses. Tissue samples from 228 rodents and shrews were screened for six viral families using PCR assays. Rat hepatitis E virus (HEV) (Rocahepevirus ratti), a rodent-associated virus with potential for human spillover, was identified in Mus musculus and Rattus norvegicus from Kibera. NGS was conducted for the HEV positive samples, and we obtained two near-complete HEV genomes from Rattus norvegicus, which clustered within rodent-associated HEV genotypes in the phylogenetic analysis. The two sequences from the Rattus norvegicus cluster together, indicating a close genetic relationship. Paramyxoviruses belonging to the genera Jeilongvirus and Parahenipavirus were detected both from Taita and Kibera in nine different samples from Rattus norvegicus, Mus minutoides, Crocidura sp and Acomys ignitus. One paramyxovirus positive sample (Acomys ignitus) from Taita was selected for further sequencing with NGS, and a complete genome of a new jeilongvirus was assembled. Phylogenetic analysis of the detected viruses confirmed the close relation to previously known rodent-borne jeilongviruses but also revealed potentially novel jeilong- and parahenipavirus species. Our findings highlight the circulation of potentially zoonotic viruses in both urban and rural small mammals in Kenya. It emphasizes the necessity of continued genomic surveillance of zoonotic viruses to mitigate risks of their spillover into human populations. HighlightsO_LISurveillance reveals diverse rodent-borne viruses circulating in Kenya. C_LIO_LIRat-HEV was detected in Rattus norvegicus and Mus musculus from an urban low-income area. C_LIO_LIParamyxoviruses were detected across multiple rodent and shrew species, including novel Acomys ignitus jeilongvirus. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/719784v1_ufig1.gif" ALT="Figure 1"> View larger version (66K): org.highwire.dtl.DTLVardef@194e81eorg.highwire.dtl.DTLVardef@11342cdorg.highwire.dtl.DTLVardef@186ad97org.highwire.dtl.DTLVardef@eeb516_HPS_FORMAT_FIGEXP M_FIG C_FIG

Salmonella Typhimurium is a versatile foodborne pathogen with a broad ecological range, making it an ideal model to better understand pathogen adaptations that allow them to infect multiple hosts and persist across diverse environments. We analyzed 745 genomes of S. Typhimurium isolated from three food animal sources (bovine, swine, and poultry) and two non-food animal sources (wild birds and the environment). We found that S. Typhimurium from food animal sources generally had a more open pangenome and harbored more antimicrobial resistance genes (ARGs) than non-food animal sources. Notably, swine isolates exhibited the most open pangenome and prevalent ARGs, likely as a result of horizontal gene transfer primarily mediated by plasmids. Despite similar core genome sizes, S. Typhimurium from different sources displayed distinct patterns of positive selection in the core genome that varied in both frequency and targeted functional categories. In contrast, although accessory genome sizes varied substantially across sources, the frequency of positive selection remained similar. Using machine learning, we further identified genetic variants (e.g., virulence factors) highly predictive of sources. These findings suggest that gain and loss of accessory genes and positive selection acting on core genes facilitate differential adaptation in S. Typhimurium, contributing to its broad ecological range.

Triatominae bugs are the main vectors of Chagas disease in Latin America and rely on microbial nutritional symbiosis to complement their haematophagous diet with B-vitamins. While Rhodococcus bacteria have been identified as key symbionts, diverse metabarcoding analyses have suggested additional candidates. However, symbiont genomic data and metabolic capabilities remain largely uncharacterized. To address this gap, we generated metagenomic assemblies for 14 Triatominae and captured 15 bacterial genomes belonging to 4 genera (Rhodococcus, Wolbachia, Symbiopectobacterium and Arsenophonus) across 9 triatominae species. We identified five co-infection cases, including one involving two distinct Arsenophonus symbionts, one exhibiting hallmarks of massive genome degradation. Phylogenetic analyses revealed that Triatominae-associated symbionts form monophyletic groups within each genus, suggesting common origins followed by co-evolution with their hosts. Annotation of vitamin B metabolic genes indicates that most symbionts harbour incomplete pathways, with evidence of metabolic complementation between co-infecting symbionts. Additionally, we identified bacterial genes laterally transferred into host insect genomes, interpreted as footprints of present or past symbiotic associations. Nearly all Triatominae genomes displayed transferred genes from all four bacterial genera, including hosts with no detectable symbiont in genome assemblies. Taken together with these discoveries support the existence of a stable and limited network of four possible nutritional symbiont lineages with rare evidence of symbiont turn-overs. Significance statementTriatominae bugs, vectors of Chagas disease, are known to harbor a diverse community of nutritional bacterial symbionts whose genomic and metabolic roles have remained largely unexplored. By reconstructing 15 symbiont genomes that segregate as four bacterial genera, we provide important insight into the origins, the evolution and the metabolic structure of the nutritional symbiosis in triatominae. These findings support a stable, evolutionary conserved network of nutritional symbionts with limited turnover.

In a confirmatory study, we evaluated the immunogenicity and protective efficacy of a heterologous prime-boost vaccination strategy against respiratory syncytial virus (RSV) in non-human primates. Building on prior evidence of protective mucosal immunity induced by intramuscular DNA priming followed by an oropharyngeal adenoviral boost, we conducted a randomized, blinded, dual-centre study across two European primate research facilities. Rhesus macaques received a codon-optimized RSV-F DNA vaccine via electroporation, followed by two mucosal administrations of a recombinant adenovirus serotype 5 vector encoding the same antigen. Control groups included animals vaccinated with irrelevant influenza antigens and a comparator group mimicking natural immunity induced by primary RSV infection. Systemic and mucosal immune responses, including RSV-F-specific antibodies and tissue-resident memory T cells, were monitored longitudinally. Here, we detected robust immune responses, but with some variability between the two centres. However, following experimental RSV challenge performed 22 weeks after the final immunization, RSV-vaccinated animals demonstrated markedly reduced viral replication in both upper and lower respiratory tracts. However, unexpected RSV-specific immunity in the control group at one single study site prevented confirmation of the predefined primary endpoint. Overall, these results support the potential of mucosal adenoviral boosting following DNA priming to induce protective immunity against RSV, while highlighting challenges associated with multi-centre preclinical vaccine studies.

Cerebral malaria is a severe neurological complication of Plasmodium falciparum infection. Damage of the blood-brain barrier (BBB) and endothelial dysfunction are established drivers of the disease pathology, however, whether astrocytes, a major constituent of the BBB, influence the disease outcome remains unclear. Using the murine model of experimental cerebral malaria (ECM), we show that astrocytes decisively regulate the outcome of ECM and the deubiquitinating enzyme OTUD7B in astrocytes fosters the disease. Mice lacking astrocytic OTUD7B showed reduced brain pathology and were protected from ECM compared with wildtype littermate controls. Transcriptomic profiling of ex vivo-isolated astrocytes revealed reduced proinflammatory chemokines and cytokines in the absence of OTUD7B. Plasmodium infection-associated microvesicles triggered a pro-inflammatory response in astrocytes, which was dependent on OTUD7B. Mechanistically, OTUD7B cleaved K48-linked ubiquitin chains from TRAF3 and TRAF6 upon stimulation with microvesicles or activation of TLR3/TLR9 by plasmodial nucleic acids. The OTUD7B-dependent TRAF3 and TRAF6 stabilization led to sustained NF-{kappa}B and p38 MAP kinase signaling and CXCL10 expression. Therapeutic silencing of CNS Otud7b or Cxcl10 expression after disease onset protected mice from ECM, identifying the cerebral OTUD7B-Cxcl10 axis as an attractive therapeutic target.

Major surface antigens in many pathogens are encoded by rapidly diversifying multigene families, generating fitness variation through antigenic and functional differences. These variations align with the niche and absolute fitness axes of Modern Coexistence Theory (MCT). Yet, how such gene families evolve along these axes under competition for hosts and across transmission gradients remains poorly understood, as prior MCT studies have not explicitly accounted for evolutionary dynamics in high dimensions. We use a stochastic computational model of Plasmodium falciparum transmission to examine how transmission intensity and selection shape var multigene family evolution and composition within parasite genomes. Results show that selection alone cannot maintain the observed stable ratio of two gene groups within parasite genomes, indicating that group-based classifications do not clearly reflect transmission strategy or virulence. When a trade-off exists between diversification rates and absolute fitness, strong immune selection under high transmission favors fast-recombining genes while attenuating functional selection on R0-associated traits. In general, stronger immune selection increases the invasion probability of novel antigens and the niche differentiation among parasite genomes, while reducing the variance in gene-level transmissibility and expression duration, and therefore R0. This outcome, combining enhanced niche differentiation and reduced absolute fitness variation, departs from MCT predictions.

Upon infection, arteriviruses, coronaviruses, and other nidoviruses transform endoplasmic reticulum membranes into viral replication organelles. These include large numbers of double-membrane vesicles (DMVs) whose interior is considered the primary site of viral RNA synthesis. Early studies characterized nidovirus DMVs as sealed compartments, leaving it unclear how newly synthesized viral RNA could be exported to the cytosol. The discovery of DMV-spanning pore complexes in coronavirus-infected cells provided a plausible solution for this topological challenge. However, their structural organization, functional features, and evolutionary conservation across the nidovirus order, have remained unclear. Here, we investigated the macromolecular architecture of DMVs induced by two prototypic arteriviruses using cellular cryo-electron tomography. Despite the substantial evolutionary distance separating arteriviruses and coronaviruses, we observed DMV-spanning pore complexes with striking structural similarities to those previously described in coronaviruses. These pores appear to facilitate both export and encapsidation of viral RNA. In the absence of viral RNA synthesis, ectopic expression of the arterivirus transmembrane nonstructural proteins nsp2 and nsp3 sufficed to induce the formation of pore-containing DMVs. Together, our findings reveal the conservation of key structural features of DMV pores across two distantly related nidovirus families and support a central role for these pores in nidovirus replication.

Since 2021, highly pathogenic avian influenza viruses (HPAIVs) belonging to H5N1 clade 2.3.4.4b have circulated widely in North American wild birds and repeatedly spilled over into mammals. In 2025, the first H5N1-associated deaths in humans were recorded in the Western hemisphere, raising questions about how the ongoing evolution of the virus in wild birds impacts spillover risk. Here, our analysis of 21,471 H5N1 genomes identified an evolutionary shift in mid-2024, driven by interhemispheric migration from Asia and reassortment with new antigens. The genotypes that dominated the early years of North Americas H5N1 epizootic traced their ancestry back to Europe, but Asia was the source of new "D1.1" genotype viruses that (a) spread faster, (b) have higher reassortment potential, (c) a broader host range, (d) repeatedly spill over to bovines, and (e) cause severe disease in humans, including non-farm workers.

Acinetobacter baumannii is a high-priority multidrug-resistant pathogen that survives within host cells by hijacking intracellular defense pathways. Here, we identify a previously unrecognized signaling axis linking bacterial invasion to host lysosomal regulation. We show that A. baumannii activates calcium-independent phospholipase A2 (iPLA2), leading to increased lysophosphatidylcholine (LPC) production and calcium influx through the ORAI1 channel, which together drive activation and nuclear translocation of the lysosomal transcription factor EB (TFEB). Pharmacological inhibition or genetic silencing of iPLA2 or ORAI1 markedly impaired TFEB activation and lysosomal biogenesis. Mechanistically, we demonstrate that this pathway is initiated by the outer membrane protein A (OmpA), which promotes bacterial invasion and enhances iPLA2 activity, LPC production, and downstream TFEB signaling. Despite induction of lysosomal biogenesis, A. baumannii persists intracellularly by producing ammonia and alkalinizing the lysosomal environment, thereby counteracting host antibacterial activity. In vivo, infection induces activation of HLH-30, the TFEB ortholog, in Caenorhabditis elegans in an OmpA-dependent manner. Together, our finding define an OmpA-iPLA2-LPC-ORAI1-TFEB signaling axis that coordinates host lipid and calcium signaling with lysosomal responses, while revealing a bacterial counterstrategy that promotes intracellular survival.

Head and neck squamous cell carcinoma (HNSCC) is an aggressive malignancy characterized by local invasion, lymph node metastasis, and therapeutic resistance. Chronic periodontal disease has been linked to HNSCC progression, yet the responsible pathogens and underlying molecular mechanisms remain unclear. Here, we show that the keystone periodontal pathogen Porphyromonas gingivalis promotes HNSCC metastasis and chemoresistance through two internalin proteins that are secreted via the type IX secretion system (T9SS). These internalin proteins specifically bind the EC1 domain of E-cadherin through their curved solenoid-like leucine-rich repeats (LRRs), facilitating bacterial invasion and inducing epithelial-to-mesenchymal transition (EMT). Mechanistically, internalin-E-cadherin engagement drives {beta}-catenin nuclear translocation and activates p38 and JNK1/2 MAP kinase signaling pathways, enhancing tumor cell migration, metastatic dissemination, and resistance to cisplatin-induced apoptosis. Tissue microarrays detect internalin antigens in HNSCC specimens, supporting their in vivo relevance. Together, these findings establish a direct mechanistic link between an oral pathogen and HNSCC progression and extend the paradigm of internalin-E-cadherin interactions from microbial pathogenesis to cancer biology.

AO_SCPLOWBSTRACTC_SCPLOWAphids threaten crop productivity through phloem feeding and the transmission of plant viruses. Aphis gossypii, in particular, is a widespread and damaging pest of worldwide cultivated melon. Resistance to its emerging CUC1 clone in Europe remains poorly characterized. Here, we dissected the genetic architecture of melon resistance to CUC1 using complementary traits that capture multiple stages of the aphid-melon interaction: plant attractiveness to aphids, acceptance, aphid colonization, and multiplication. Genome-wide association studies (GWAS) in a diversity panel of 174 accessions identified a quantitative trait locus (QTL) for attractiveness on chromosome 6, while analyses in a complementary panel of 212 accessions revealed QTLs for plant acceptance by aphids on chromosomes 3, 8, and 12. Colonization and multiplication traits further highlighted resistance QTLs on chromosomes 5 and 12, the latter supported by both SNP-based GWAS and bulk-segregant analysis. Pan-NLRome k-mer- and graph- based GWAS, together with Vat presence/absence association analyses, provided allele-level resolution of the QTL on chromosome 5, corresponding to the Vat region. Leveraging allelic diversity at this locus, we functionally characterized 20 Vat homologs with four R65aa motifs within their leucine-rich repeat (LRR) domain and demonstrated the capacity of R65aa-type Vat alleles to confer clone-specific resistance. Resistance-conferring alleles limited virus multiplication, such as Cucumber mosaic virus (CMV), when transmitted by five A. gossypii clones, including CUC1. Together, our results revealed multiple genetic determinants underlying quantitative resistance to the A. gossypii CUC1 clone in melon and highlighted the central role of Vat homologs in resistance to both A. gossypii and the viruses it vectors. These findings provide strategic targets for pyramiding resistance loci acting at different stages of the pest life cycle to enhance durable protection against these biotic threats.

Background and AimsThe rising incidence of Crohns disease (CD) in Westernized countries has been linked to changes in diet and increased consumption of food additives, yet the mechanisms by which these factors fuel intestinal inflammation remain unclear. Adherent-invasive Escherichia coli (AIEC), a pathobiont involved in CD pathogenesis, lacks a clear genetic hallmark but exhibits intestinal colonization and virulence traits, raising questions about the evolutionary forces promoting its emergence among select individuals. Here, we investigated how chronic exposure to two common dietary emulsifiers, carboxymethylcellulose (CMC) and polysorbate 80 (P80), along with host inflammation, drives AIEC genomic evolution and pathogenic potential. MethodsWild-type and Il10-deficient mice were monocolonized with AIEC and chronically exposed to CMC, P80, or water. Bacterial isolates were collected and analyzed for genomic diversification, mutations, and phenotype both in vitro and in vivo. ResultsEmulsifiers accelerated AIEC genomic diversification and selected for mutations linked to increased motility, invasion, and pro-inflammatory activity. Moreover, dietary emulsifier-evolved strains displayed a marked fitness advantage in vivo, outcompeting their counterparts in murine hosts, with the greatest advantage observed when evolution occurred under inflammatory conditions. Notably, evolutionary pathways and phenotypic outcomes were shaped by both emulsifier and the hosts inflammatory status, highlighting synergy between diet and host genetics in fostering pro-inflammatory pathobionts. ConclusionThese findings provide an evolutionary framework connecting modern dietary habits to the emergence of pathogenic AIEC strains, and underscore the importance of dietary interventions in individuals at risk for inflammatory bowel disease.

COVID-19 disease is associated with thrombosis, but the pathogenic mechanism remains unclear. Here, we investigate how SARS-CoV-2 spike protein causes platelet activation and aggregation. Our three-dimensional ultrastructural analyses showed that invaginated platelet structures, open canalicular system (OCS), expanded upon activation, trapping viral particles in the process. Binding with platelet OCS concealed SAR-CoV-2 spike-coated particles from virion detection in platelet-depleted blood plasma. Both SARS-CoV-2 spike coated-particles and recombinant spikes specifically induced platelet aggregation with nanoscale filipodia extensions, with the terminal sialic acids of the SARS-CoV-2 spike protein-associated sialoglycoconjugates being the key determinant in platelet activation. Our work illustrates that virus-associated sialic acids, not proteins, are functionally responsible for SARS-CoV-2 induced thrombotic events, providing a mechanistic insight on how glycosylation contributes to disease severity in COVID-19. This study lays the foundation for the development of glycan-modified vaccines with reduced risks of thrombosis.