PLOS Pathogens: New Articles

A chemical bactericide dioctyldiethylenetriamine (Xinjunan) exerts a non-lethal effect by inhibiting RpfG activity to regulate the quorum sensing system

2026-06-10T14:00:00Z

by Ling Jin, Xing Chen, Chaoyue Pang, Yongquan Huang, Changshun Ji, Yuanyuan Zhang, Xueqiao Liu, Yang Sun, Yu Chen

Bacterial diseases pose a major threat to global agriculture and food security. Bactericides are highly effective in disease control due to their direct antibacterial effect. However, it causes “life or death” selection pressure on the target bacteria and can lead to bactericide resistance. Quorum sensing inhibitors exert indirect antibacterial effect that weakens their virulence and combined use of bactericides and quorum sensing inhibitors demonstrated more significant disease control than a single agent. In this study, dioctyldiethylenetriamine, a bactericide that has previously been proven to have a direct antibacterial effect, exhibited an indirect antibacterial effect that weakened bacterial virulence. Using transposon sequencing, we found that the quorum sensing system, which is closely related to virulence in Xanthomonas oryzae pv. oryzae (Xoo, PXO99A), was significantly affected by dioctyldiethylenetriamine. It was further found that RpfG, which is responsible for transduction of the quorum sensing signal molecules in PXO99A, was significantly inhibited at both transcriptional and translational levels after dioctyldiethylenetriamine treatment, resulting in impaired phosphodiesterase activity, which in turn caused bacterial quorum quenching (QQ). QQ not only weakened the virulence of the bacteria, but also reduced their motility, which could effectively prevent the bacteria from escaping the direct antibacterial effect of dioctyldiethylenetriamine, thus providing a more effective control effect. Finally, we found that the QQ induced by dioctyldiethylenetriamine appeared to be specific, occurring in a subset of bacteria containing RpfG. The interspecific competitiveness within the same ecological niche also appeared to be weakened, which was accompanied with QQ. These findings have enriched our understanding of the antibacterial mechanism of bactericides and provided a theoretical basis for the scientific and rational use of bactericides as well as the development of “RpfG-based” indirect antibacterial agents with both efficient antibacterial activity and ecological safety.

Understanding the impact of Klebsiella pneumoniae K-Antigen based MAPS vaccine design on the immune response in animal models

2026-06-10T14:00:00Z

by Elena Palmieri, Gianina Florentina Belciug, Francesca Nonne, Luisa Massai, Silvia Valensin, Antonella De Rosa, Francesco Berlanda Scorza, Simona Rondini, Martina Carducci, Omar Rossi, Francesca Micoli, Carlo Giannelli

MAPS technology represents an innovative approach for the development of polysaccharide-based vaccines, relying on the affinity interaction between biotin and rhizavidin (rhavi), with potential for enhanced coverage through the incorporation of pathogen-specific proteins. Due to its flexibility, this platform is particularly attractive for the development of multivalent vaccines, as it is required for Klebsiella pneumoniae, a multidrug-resistant bacterium highlighted as prevalent cause of neonatal sepsis in low- and middle-income countries, against which no vaccines are currently available. In this work MrkA, a potential protective pathogen-specific protein antigen, was combined in a MAPS complex with K2 as model for Klebsiella K-antigen. The impact of sugar chain length, protein to polysaccharide ratio, and MAPS complex size on the immune response elicited in animal models was evaluated. Results showed that longer polysaccharides and higher protein/K-antigen ratios enhanced the immunogenicity in rabbits. Different proteins, i.e., rhavi alone and CP1-rhavi from Streptococcus pneumoniae, were also evaluated as carrier, showing that the protein antigen fused to rhavi can play a significant role on the resulting MAPS polysaccharide specific immunogenicity. Passive transfer of rabbit polyclonal sera from the most immunogenic MAPS complex was able to protect mice from challenge with a K2 clinical isolate. This work supports the rational design of a K-antigen MAPS-based vaccine against Klebsiella pneumoniae.

Downregulation of miR-10b-3p by EBV promotes tumor growth and metastasis via ITGAV in nasopharyngeal carcinoma

2026-06-09T14:00:00Z

by Yu Zhang, Yaoqiang Shi, Yingdong Zou, Li Li, Ziqin Dian, Yuling Chen, Hang Zhao, Jiajun Wang, Yi Sun

Nasopharyngeal carcinoma (NPC) is a malignant epithelial tumor strongly associated with Epstein-Barr virus (EBV) infection. EBV-mediated dysregulation of host microRNAs (miRNAs) contributes to NPC pathogenesis, but the functions of many EBV-regulated host miRNAs remain incompletely defined. miR-10b-3p is markedly downregulated in EBV-positive NPC, yet its biological significance and downstream mechanism remain unclear. Here, we found that miR-10b-3p was reduced in EBV-positive NPC tissues and was further suppressed following EBV infection of non-malignant nasopharyngeal epithelial cells and EBV-negative NPC cell lines. Restoration of miR-10b-3p expression markedly inhibited cell proliferation, colony formation, migration, invasion, and epithelial-mesenchymal transition (EMT) in EBV-positive NPC cells, whereas inhibition of miR-10b-3p in EBV-negative NPC cells produced the opposite effects. In nude mouse xenograft and lung metastasis models, overexpression of miR-10b-3p significantly reduced tumor growth and pulmonary metastasis. Mechanistically, miR-10b-3p directly targeted the 3′-UTR of integrin subunit alpha V (ITGAV), leading to decreased ITGAV expression and subsequent attenuation of STAT5 and ERK1/2 signaling. Forced ITGAV expression partially reversed the suppressive effects of miR-10b-3p on tumor cell proliferation, migration, invasion, and EMT. Moreover, miR-10b-3p levels were inversely correlated with ITGAV expression in NPC tissues. Collectively, these findings identify an EBV-regulated miR-10b-3p/ITGAV/STAT5-ERK1/2 axis in NPC and show that loss of miR-10b-3p promotes tumor growth and metastasis by relieving ITGAV repression, suggesting potential therapeutic targets for EBV-associated NPC.

Correction: Molecular response to the non-lytic peptide bac7 (1–35) triggers disruption of Klebsiella pneumoniae biofilm

2026-06-09T14:00:00Z

by Robert L. Beckman I. V, Berta Victoria, Flor Z. Santiago, Gabriela N. Echeverria, Bruno V. Pinheiro, Marcelo D.T. Torres, Logan Suits, Shantal Garcia, Paeton L. Wantuch, Cesar de la Fuente-Nunez, Prahathees Eswara, David A. Rosen, Renee M. Fleeman

Inhibition of high risk HPV31 E8^E2 repressor activity enables differentiation-independent genome amplification and E4 expression

2026-06-08T14:00:00Z

by Tina Melanie Rehm, Elke Straub, John Doorbar, Adam Grundhoff, Thomas Günther, Patrick Blümke, Thomas Iftner, Frank Stubenrauch

Persistent infections with high-risk human papillomaviruses (HPV) can result in different malignancies. Productive replication of HPV is normally restricted to suprabasal keratinocytes that have entered terminal differentiation and is characterized by vegetative genome amplification, activation of the late promoter, and expression of the viral late E4 protein. Cells undergoing productive replication remain in a prolonged G2 phase and exit the cell cycle without division. The viral E8^E2 protein binds to NCoR/SMRT co-repressor complexes to repress viral transcription and replication in undifferentiated keratinocytes, but the biological rationale for this repression has remained unclear. Recent studies have revealed that Mus musculus PV1 E8^E2 prevents late viral E4 expression in undifferentiated cells to enable tumor formation in vivo. Here, we demonstrate that loss of E8^E2 function in high-risk HPV31 leads to inappropriate activation of genome amplification in undifferentiated keratinocytes, resulting in expression of E4 protein and cell cycle perturbation which explains why HPV31 E8^E2 mutant genomes fail to be maintained as episomes and instead are always found integrated in surviving cell lines. Interestingly, this is independent from E4 expression suggesting that vegetative genome amplification is sufficient to prevent cell division. Remarkably, depletion of NCoR/SMRT complexes in cell lines maintaining HPV31 episomes phenocopies E8^E2 inactivation and induces genome amplification and E4 expression. Notably, most E4-positive cells generated by E8^E2 inactivation or NCoR/SMRT depletion retain basal-like characteristics, indicating that genome amplification and E4 expression can be uncoupled from differentiation when E8^E2 repression is relieved. Interestingly, differentiation diminishes the effects of NCoR/SMRT depletion, suggesting that E8^E2 activity is likely inactivated during differentiation to permit productive replication. Collectively, these findings identify E8^E2 as a critical gatekeeper preventing premature genome amplification and E4 expression in basal keratinocytes and suggest that targeting the E8^E2–NCoR/SMRT interaction may represent a novel antiviral strategy.

Low frequency variants can predetermine antiviral drug resistance development in herpes simplex virus type 1

2026-06-08T14:00:00Z

by Lena Jaki, Florian Full, Udo Gieraths, Valeria Falcone, Zsolt Ruzsics, Hartmut Hengel, Marcus Panning, Jonas Fuchs

Severe HSV-1 disease is treated with potent antiviral drugs, in particular aciclovir (ACV) and its derivatives. However, long-term drug exposure in immunocompromised patients can lead to the emergence of ACV-resistant HSV-1 strains and clinical treatment failure. To understand how phenotypic resistances develop on a genomic level, we analyzed the influence of ACV selection pressure on the viral genome of different HSV-1 virus strains in vitro. Growth kinetics and IC₅₀ determination showed ACV resistance development within a single passage. Next, we performed ultra-deep, non-targeted full-genome Illumina sequencing of the parental and ACV-adapted HSV-1 strains. Interestingly, resistance-conferring mutations rapidly arose in the viral genes UL23 and UL30 and were already present in the parental ACV-naïve strains at extremely low variant frequencies. Based on these findings, we hypothesized that low- frequency mutations develop during continued viral replication. To test this hypothesis, a primary rescued recombinant K17 + strain was repeatedly passaged. Continued passaging indeed increased the proportion of a subset of minor variants and allowed resistance development after, but not before, 10 consecutive passages. In summary, we show that minor variants can facilitate adaptation of HSV-1 populations to selective pressures such as pharmacological inhibition of replication. These findings highlight that deep sequencing might allow early detection of resistance mutations potentially supporting antiviral drug stewardship.

The natural history and evolution of dermatophytosis: Host immunity in acute and chronic infection

2026-06-08T14:00:00Z

by Aditya K. Gupta, Tong Wang, Anuradha Chowdhary, Ditte Marie L. Saunte, Roderick J. Hay, Vincent Piguet

The Legionella pneumophila type IVb secretion system effector BinA subverts amino acid transport to sensitize TORC1 signaling in macrophages

2026-06-08T14:00:00Z

by Magdalena Circu, Reneau Castore, Brian Latimer, Stephanie Shames, Craig R. Roy, Ana-Maria Dragoi, Stanimir S. Ivanov

Legionella pneumophila is an environmental Gram-negative bacterium that parasitizes unicellular protozoa and can cause severe pulmonary infections when aerosolized bacteria are inhaled by humans. One critical aspect of Legionella pathogenesis is the establishment in the cytosol of infected macrophages of a unique ER-derived vacuole, that requires a sustained supply of host lipids during expansion. Subversion of pro-lipogenic pathways downstream of the metabolic checkpoint kinase mTOR (Mechanistic Target of Rapamycin) are critical for niche expansion. In eukaryotic cells, amino acids sufficiency and growth factor sensory signals converge on mTOR to ensure metabolic processes are coupled to nutrients/energy availability. Legionella can trigger mTOR signaling in infected cells by increasing the intracellular abundance of amino acids through inhibition of host translation. Here, we describe a novel mechanism by which Legionella sensitizes mTOR in infected macrophages. A forward genetic screen identified Lpg0393 protein as a putative bacterial mTOR regulator that contains a VPS9-domain typically found in eukaryotic GEFs (Guanine nucleotide exchange factors) for Rab5 GTPase family members (Rab5/Rab21/Rab22). We uncovered that Lpg0393 lowers the activation threshold for mTOR signaling upon stimulation with arginine or leucine by promoting anterograde trafficking of amino acid permeases through subversion of the small GTPases Rab21 and Rab22. Data from cells expressing either a bacterial or a eukaryotic mTOR sensitizing factor uncovered two distinct non-cytosolic Arg/Leu pools that fuel mTOR activation in parallel – one regulated by Rab21/22 and the other by Rab5. Consistent with the role of mTOR in expansion of the Legionella-occupied organelle, deletion of Lpg0393 also resulted in premature vacuolar rupture in a mTOR-dependent manner. All together, we have identified a novel bacterial mTOR regulator and consistent with its reported functions we propose Lpg0393 is named as BinA (Bacterial initiator of TORC1 signaling and an activator of Rab5 family GTPases).

Evaluating beta-tubulin variants as predictors of benzimidazole resistance across Caenorhabditis nematodes

2026-06-05T14:00:00Z

by Amanda O. Shaver, Ryan McKeown, Joyce M. Reyes Otero, J.B. Collins, Daniel W. Hogan, James S. Fraser, Stephen M. Dreyer, Erik J. Ragsdale, Erik C. Andersen

Benzimidazoles, a widely used class of anthelmintic drugs, target beta-tubulin, disrupt microtubule formation, and delay nematode development. In parasitic nematodes, mutations in beta-tubulin genes are predicted to inhibit benzimidazole binding and are associated with resistance. In the free-living nematode Caenorhabditis elegans, loss-of-function mutations in the beta-tubulin gene ben-1 cause benzimidazole resistance. Although several beta-tubulin mutations serve as established markers of resistance, the prediction of the effects of novel variants in different nematode species remains challenging. Here, we identified novel beta-tubulin variants predicted to confer benzimidazole resistance across wild strains in three Caenorhabditis species: C. elegans, Caenorhabditis briggsae, and Caenorhabditis tropicalis. The three Caenorhabditis species are experimentally tractable, have characterized beta-tubulin gene complements, and defined natural niches, which allowed us to identify variants in beta-tubulin genes and test which variants are associated with resistance. We hypothesized that, if these species experienced similar selective pressures, they would evolve resistance to benzimidazoles by mutations in a beta-tubulin gene (tbb-1, tbb-2, mec-7, tbb-4, and ben-1). In the three Caenorhabditis species, we tested all strains harboring variants in the five conserved beta-tubulin genes for benzimidazole resistance. In C. elegans, we found that a heterogeneous set of variants in ben-1 were associated with resistance. By contrast, only two variants in C. briggsae ben-1 (W21stop and Q134H) were associated with resistance, suggesting selection acts differently in C. briggsae than in C. elegans despite overlapping geographic ranges between the two species. C. tropicalis was distinct from the other two species, where no strains with variants in any beta-tubulin gene were resistant. We generated deletions of ben-1 in C. briggsae and C. tropicalis and confirmed that loss of ben-1 confers resistance in both species. Our findings reveal species-specific patterns of beta-tubulin-mediated benzimidazole resistance and emphasize that prediction of variants in beta-tubulin genes alone is not sufficient to predict resistance, especially across diverse Caenorhabditis species.

HIV-1 BG505 SOSIP immunization induced B cell expansion targeting the 465-glycan hole, with neutralizing antibodies exhibiting distinct binding modes and mechanisms of virus inhibition

2026-06-05T14:00:00Z

by August Myers, Monika Chandravanshi, Leanne S. Whitmore, Brendan F. Kohrn, Amina Negash, Dung N. Nguyen, Pooja Ralli-Jain, Kendra Cruickshank, Amit A. Upadhyay, Tysheena Charles, Christopher T. Edwards, Eric Hunter, Rama R. Amara, Marek K. Korzeniowski, Ling Niu, Edwin Pozharski, William D. Tolbert, Steven E. Bosinger, Scott R. Kennedy, Marzena Pazgier, Cynthia A. Derdeyn

High serum neutralization following BG505 SOSIP.664 envelope trimer immunization was associated with protection against BG505.SHIV challenge in rhesus macaques in a previous study. In an animal that developed high titer, durable neutralization against a glycan hole on envelope gp120, high throughput, longitudinal, antigen-specific B cell receptor sequencing was conducted. This analysis of more than 4,700 antigen-specific B cells revealed marked intra-clonal expansion and divergence from germline, including three abundant clonotypes that produced autologous neutralizing monoclonal antibodies. Monoclonal antibodies from the neutralizing clonotypes and two other expanded non-neutralizing clonotypes targeted epitopes in the same glycan hole, with neutralizers also demonstrating different capacities to obstruct CD4 binding. Cryo-electron microscopy structures of four neutralizing monoclonal antibodies revealed that they bound to glycan hole epitopes using distinct binding modes. One neutralizing antibody displaced a glycan in the loop V5 upon binding and its footprint includes the CD4 binding loop. The findings provide insight into how antibody recognition of a prominent glycan hole could facilitate different mechanisms of neutralization while underscoring how intra-clonal expansion and maturation with repeated BG505 SOSIP.664 immunization drove high serum neutralization.

Culture-specific transcriptional drifts limit the fidelity of organoid infection models

2026-06-04T14:00:00Z

by Paula E. Schweizer, Wisal A. Elmagzoub, Sanaa M. Idris, Kamal H. Eltom, Julius B. Okuni, Lonzy Ojok, ElSagad Eltayeb, Ahmad Amanzada, Marianne Quaas, Gabriela Aust, Maxi Harzer, Thomas W. Vahlenkamp, Nico Jehmlich, Marlon R. Schneider, Guntram A. Grassl, Jens Puschhof, Knut Krohn, Ralph Goethe, Uwe Truyen, Jörg Galle, Ahmed Abd El Wahed

Intestinal organoids are powerful tools for modeling host-pathogen interactions, yet culture-induced artifacts remain poorly defined. Here, we performed time-course transcriptomic profiling of patient-derived ileal organoids microinjected with Mycobacterium avium subsp. paratuberculosis (MAP) or treated with the swelling agent forskolin (FSK) and compared expression changes to untreated controls. Our analysis revealed that culture-associated transcriptional drift was the primary driver of gene expression changes over the 48-hour time course, likely obscuring pathogen-specific responses. This drift involved progressive downregulation of metabolic genes accompanied by the upregulation of genes with high GC content. Although FSK treatment improved. microinjection efficiency, it also introduced additional confounding effects, including transient activation of apoptotic pathways and upregulation of inflammatory genes that resolved within two days. While MAP infection did not produce significant single-gene responses, gene set analysis revealed significant infection-associated effects. Spatial transcriptomics further demonstrated that multiple enterocyte gene sets became downregulated during culture, independent of their normal crypt-villus expression pattern. Gene sets typically expressed at the crypt-villus junction showed the greatest downregulation. Notably, MAP infection selectively counteracted these culture-induced changes, preserving gene expression patterns characteristic of the upper villus epithelium. These findings indicate that both metabolic stress and pharmacological interventions can substantially confound organoid-based infection models. More broadly, they underscore the importance of spatially resolved transcriptomics and appropriate temporal controls to distinguish genuine pathogen responses from culture-related artifacts. To our knowledge, no previous studies have used human intestinal organoids to model MAP infection or characterized the epithelial transcriptomic response. This work establishes critical frameworks for investigating MAP’s role in Crohn’s disease pathogenesis.

Feedback coordination of FoxO-mediated antibacterial immunity by PDGF/VEGF signaling establishes hemolymph microbiota homeostasis in shrimp

2026-06-04T14:00:00Z

by Ping-Ping Liu, Meng Zhang, Zhe Wei, Wei-Guang Wang, Jin-Xing Wang, Yuanning Li, Xian-Wei Wang

A balanced immune response is required to limit the microbes without causing damage to the host. The forkhead box O (FoxO)-mediated immunity plays a pivotal role in maintaining microbiota homeostasis by regulating the expression of antimicrobial effectors in non-infected arthropods. However, the mechanism by which FoxO activity is appropriately coordinated remains unclear. In this study, we elucidated a feedback loop that coordinates FoxO-mediated antibacterial response using shrimp as a model. In this feedback loop, the commensal hemolymph microbiota maintains basal activation of FoxO, which determines the expression of antimicrobial effectors, platelet-derived growth factor/vascular endothelial growth factor (PDGF/VEGF)-related factor 1 (Pvf1) and PDGF/VEGF-related receptor 4 (Pvr4). This ligand-receptor system enhances phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB/Akt) activity, limiting the excessive activation of FoxO and expression of antimicrobial effectors. This feedback loop is essential for maintaining the equilibrium of the microbiota, and its strength increases following a pathogenic infection, reducing the incidence of infection-induced mortality and tissue damage. This study revealed a microbiota-initiated feedback loop that balances FoxO-mediated antibacterial immunity for the establishment of microbiota homeostasis, and provides new insights into the functional diversification of PDGF/VEGF signaling.

Distinct prion conformers from brain and peripheral tissues of gene-targeted mice produce convergent CWD strain properties

2026-06-04T14:00:00Z

by Joseph P. DeFranco, Zoe N. Atkinson, Jenna Crowell, Xutong Shi, Sehun Kim, Julianna L. Sun, Sarah J. Kane, Glenn C. Telling

Prions are unique infectious agents because different conformational properties of their constituent proteins are responsible for the manifestation of distinct strains. While prion replication in humans with sporadic Creutzfeldt-Jakob disease and cattle with bovine spongiform encephalopathy is primarily limited to the central nervous system (CNS), a seminal feature of chronic wasting disease (CWD) in cervids is high infectious titers in peripheral tissues, including skeletal muscles and the lymphoreticular system. Although extensive studies have assessed prion properties in the CNS, our understanding of prions in peripheral tissues remains limited. Here, we compared the strain properties of CWD prions in peripheral and CNS tissues of gene-targeted (Gt) mice. Our studies reveal differences in the biochemical and conformational properties of CWD prions, as well as the prion levels, between peripheral and CNS tissues. While this finding suggested that these tissues harbored distinct CWD prions, transmissions of muscle, spleen, and brain homogenates to Gt mice by the intraperitoneal route produced convergent strain properties. Importantly, transmission of these tissues by the intracerebral route resulted in different disease phenotypes than intraperitoneal inoculations. Additionally, while prion infection of CWD-susceptible cells revealed different titers in muscle, spleen, and brain tissues, the conformational properties of the resulting de novo prions were indistinguishable. While our findings support a role for tissue-specific cofactors that affect the biochemical and conformational properties of prions, they also show that these parameters do not solely dictate disease outcomes and that additional factors, particularly the route of inoculation, exert a more pronounced influence on strain outcomes.

Retraction: Androgen receptor transactivates KSHV noncoding RNA PAN to promote lytic replication–mediated oncogenesis: A mechanism of sex disparity in KS

2026-06-04T14:00:00Z

by The PLOS Pathogens Editors

ATAD3 megadalton complex in Plasmodium falciparum is essential for mitochondrial and cellular viability

2026-06-03T14:00:00Z

by Ijeoma C. Okoye, Ian M. Lamb, Yee-Wai Cheung, Joanne M. Morrisey, Manish Sharma, Rajat Kumar, Swati Dass, Anurag Shukla, River S. Rell, Michael W. Mather, Manuel Llinás, Yi-Wei Chang, Akhil B. Vaidya

Malaria remains an urgent threat to global health as the mortality and infection rates keep rising annually and our frontline antimalarials are becoming less effective due to the emergence and spread of resistance-conferring mutations. Although the mitochondrion of P. falciparum parasites is a validated drug target, there remain many uncharacterized mitochondrial proteins. The goal of this study was to investigate the essentiality and functions of a recently identified mitochondrial protein - PF3D7_0707400. Our results show that PF3D7_0707400 is an ATAD3A homolog that is essential to parasite survival and is present in a megadalton complex that is critical for multiple mitochondrial processes such as mitochondrial RNA stability, membrane potential, ultrastructure, and protein import. ATAD3A has been previously studied in multicellular eukaryotes and has been implicated in several childhood mitochondrial diseases, with suggested functions in mitochondrial nucleoid stabilization, mitochondrial RNA translation, and mitochondrial inner membrane integrity. This study is the first characterization, to our knowledge, of ATAD3A in unicellular organisms. Our findings here expand our knowledge on apicomplexan mitochondrial biology and our arsenal of potential antimalarial drug targets.

Fingolimod increases cellular resistance to HIV-1 infection and limits viral reservoir size in peripheral CD4⁺ T-cells

2026-06-03T14:00:00Z

by Elisa Moraga, Núria Climent, Alejandro Sánchez-Molina, Sònia Vicens-Artés, María José Maleno, Gabriel Valero López, Carlos Galera Peñaranda, Juan Ambrosioni, José M. Miró, Josep Mallolas, Helena Albendín-Iglesias, José Alcamí, Sonsoles Sánchez-Palomino

Background

Fingolimod, a treatment for multiple sclerosis (MS), decreases autoreactive lymphocytes by lymph node sequestration. In vitro, fingolimod decreases HIV-1 infection and viral reservoir (VR) through SAMHD1 phosphorylation inhibition and reducing lymphocyte activation and CD4 expression. We identified an exceptional MS patient infected with HIV-1 (HIV+ MS+) while on fingolimod therapy and we have analyzed its impact on HIV-1 infection in vivo and ex vivo.

Methods

The case was the HIV+ MS+ patient. Controls were 20 PWH (HIV+ MS-), five HIV-negative donors (HIV-MS) and three HIV-negative MS patients treated with fingolimod (HIV-MS+), as the case reported. VR was quantified by IPDA and HIV-1 intracellular RNAs (icRNAs) by ddPCR in peripheral blood CD4⁺ T-cells. CD4⁺ T-cells were infected in vitro with an NL4.3-Renilla strain. Immunophenotype, activation markers and phosphorylated SAMHD1 levels were determined by flow cytometry.

Findings

At diagnosis, HIV+ MS+ viral load was nine-fold lower than HIV+ MS- treated at similar Fiebig stage. One year after ART, HIV+ MS+ showed lower intact and defective VR than the HIV+ MS- control group (28-and six-fold decrease respectively). After three years on ART no intact proviruses were detected in HIV+ MS+ . HIV-1 in vitro infection was decreased in HIV+ MS+ and HIV- MS + vs HIV+ MS- and HIV-MS-. CD4⁺ T-cells levels from fingolimod treated patients were lower and showed decreased CD4 expression, lymphocyte activation and SAMHD1 phosphorylation vs HIV- MS-. icRNAs were significantly increased after T-cell activation in the HIV+ MS-, while they were barely detected at resting and activated HIV+ MS+ CD4⁺ T-cells.

Conclusions

We describe a strong restriction to HIV-1 infection and replication in vivo and ex vivo leading to indetectable intact VR in HIV+ MS+ after three years of ART. Potential mechanisms of restriction are CD4 downregulation, T-cell activation inhibition, and SAMHD1 activity enhancement.

Structural basis for conserved and distinct antigen recognition by a lineage of malaria-protective antibodies

2026-06-03T14:00:00Z

by Monika Jain, Fabien Cannac, Sashank Agrawal, Wen-Hsin Lee, Johannes R. Loeffler, Monica L. Fernández-Quintero, Gonzalo E. González-Páez, Re’em Moskovitz, Andrew B. Ward, Ian A. Wilson

Monoclonal antibodies (mAbs) targeting the Plasmodium falciparum circumsporozoite protein (PfCSP) have demonstrated substantial promise in preventing malaria infection and disease. PfCSP is characterized by a central region composed of repetitive NANP motifs, which serve as major targets for protective antibodies. Several potent mAbs targeting this region exhibit homotypic Fab-Fab interactions, which enhance antigen binding and contribute to their neutralization potency. Among these, mAb 399, encoded by the IGHV3-49/IGKV2D-29 (V_H3-49/V_K2D-29) germline lineages, forms head-to-head inter-Fab contacts mediated primarily by germline-encoded residues. Here, we determined X-ray and cryo-EM structures of two additional Fabs, derived from the same germline lineages, 7160 and 7118, in their unliganded forms and with PfCSP-derived peptides or recombinant shortened CSP. Both Fabs bound NANP₆ repeats with high affinity (K_D 6–10 nM). Fab 7160 formed germline-encoded inter-Fab homotypic interactions resembling Fab 399, indicating a conserved and preconfigured mode of antigen recognition. In contrast, Fab 7118 does not form homotypic contacts and adopts a distinct binding mode, which precludes inter-Fab interactions. These findings highlight the structural versatility of V_H3-49/V_K2D-29-derived antibodies and demonstrate that their CDR loop variations can modulate antibody conformation, homotypic Fab-Fab interactions, and epitope engagement. Our study further defines this class of germline-encoded anti-CSP antibodies and provides mechanistic insights into how they achieve high-avidity binding and protective immunity either through or independent of pre-configured Fab-Fab interactions with important implications for germline-targeting malaria vaccine design.

Is heme metabolism a promising drug target in Toxoplasma gondii?

2026-06-02T14:00:00Z

by Zhicheng Dou

Yad fimbriae are triggered by host cues and enhance extraintestinal pathogenic Escherichia coli tissue colonisation during bloodstream infection

2026-06-01T14:00:00Z

by Chloe Ellison, Curtis Cottam, Zheng Jie Lian, Tugce Onur, Burhan A. Choudhry, Yvette Yu Ting Ong, Minh-Duy Phan, Mark A. Schembri, James P. R. Connolly

Bacterial pathogens that infect host sites beyond their native ecological niche must be equipped to cope with unique challenges across distinct environments. This often manifests in the upregulation of virulence factors specifically in response to host cues, which enhance pathogen fitness. Extraintestinal pathogenic Escherichia coli (ExPEC) typically colonise the host-gut asymptomatically but can disseminate to infectious sites such as the bladder, kidneys and bloodstream. The molecular basis of urinary tract colonisation by ExPEC is well established, with adhesion via chaperone-usher fimbriae being a critical determinant. However, mechanisms that promote bloodstream infection are poorly understood. Here, we show that several ExPEC fimbriae are upregulated rapidly in response to human serum, mimicking exposure to the bloodstream environment. Yad fimbriae displayed the most significant induction in response to this host cue in two distinct ExPEC isolates, and we show that the gene cluster is prevalent across the E. coli phylogeny, suggesting a common virulence mechanism. Expression of Yad fimbriae was found to be repressed at the transcriptional level by the histone-like nucleoid structuring protein (H-NS). Furthermore, a prolonged elevation in Yad transcription was sustained throughout many generations of growth in serum, suggesting that cue(s) in the bloodstream counteract H-NS repression, triggering cell-surface expression of Yad fimbriae. Finally, Yad transcription was significantly upregulated within systemic tissue in a murine model of bacteremia and we show that deletion of the yad genes significantly attenuated ExPEC colonisation during infection. These data reveal Yad fimbriae as an important ExPEC virulence factor and support the concept of cellular adhesion as a crucial element of bacterial bloodstream pathogenesis.

A designed peptide disrupting viral protease cleavage restores cGAS-DNA phase separation and type I interferon responses

2026-06-01T14:00:00Z

by Hongyan Yin, Zhenchao Zhao, Haiwei Wang, Xin Li

Seneca Valley Virus (SVV) 3C protease is essential for viral polyprotein processing and virion assembly. Meanwhile, it has evolved to cleave and antagonize the multiple innate immune proteins, enabling viral immune evasion. Inhibitors of 3C protease are therefore powerful antiviral agents. Among these, antiviral peptide inhibitors hold particular promise because of their high specificity, strong efficacy, and broad-spectrum activity, and minimal side effects. Here, we developed a dimerization-dependent red fluorescent protein (ddRFP) biosensor system to screen anti-SVV 3C peptides and identified a substrate-competitive decapeptide (P5) that markedly suppresses 3C protease activity. P5 inhibited 3C-mediated cleavage of multiple key immune proteins, including porcine cGAS (pcGAS), porcine Gasdermin A (pGSDMA) and porcine Pro-IL-1β (sPro-IL-1β). Mechanistically, P5 directly interacted with the catalytic His48 site of 3C protease through hydrogen bonding. Remarkably, P5 restored the formation of cGAS-DNA liquid-liquid phase separation (LLPS) by competitively blocking 3C cleavage activity, thereby enhancing cGAS activity and downstream antiviral interferon signaling. Furthermore, P5 demonstrated favorable cellular permeability, low cytotoxicity, good stability and robust antiviral activity. Our findings establish P5 as a highly promising peptide inhibitor of SVV 3C protease with strong translational potential.

Targeting BRD2 and BRD4 inhibit the growth of KSHV-infected immortalized endothelial cells through suppression of LANA translation

2026-06-01T14:00:00Z

by Jungang Chen, Jiaojiao Fan, Margaret Qin, Zhen Lin, Shengyu Mu, Lu Dai, Zhiqiang Qin

Kaposi’s sarcoma-associated herpesvirus (KSHV) is the etiologic agent of several human cancers, including Kaposi’s sarcoma (KS) and primary effusion lymphoma (PEL), both of which still lack effective treatment options. Members of the bromodomain and extra-terminal domain (BET) family, especially bromodomain-containing protein 4 (BRD4), play important roles in RNA polymerase II–mediated transcriptional regulation and are required for the expression of many tumor-driving oncogenes in various cancer cells. Therefore, BET proteins have become attractive targets for anticancer drug development. Previous studies have demonstrated the high sensitivity of PEL cells to BET inhibitors, and BRD4 silencing effectively blocks tumor cell proliferation. In contrast, KSHV-infected immortalized endothelial cells display strong resistance to BET inhibitors, including (+)-JQ1. To further develop BRD-targeted therapies for KSHV-infected immortalized endothelial cells, we identified MZ-1 and SIM-1, two BRD4 PROTAC degraders, as effective inhibitors of cell growth in these cells. Mechanistically, these inhibitory effects depend on suppression of LANA translation through increased eIF2α phosphorylation in KSHV-infected cells. Similar LANA suppression was also observed following RNAi-mediated silencing of BRD2 or BRD4. Proteomic analysis identified unique protein candidates altered in MZ-1- and SIM-1-treated KSHV-infected immortalized endothelial cells compared with (+)-JQ1-treated cells. In summary, our study develops an effective strategy against KSHV-infected immortalized endothelial cells using selective BRD PROTACs, which may help improve therapeutic outcomes for KSHV-related malignancies in the future.

M-Sec promotes the production of infectious HIV-1 virus through the exocyst complex in macrophages

2026-06-01T14:00:00Z

by Reem M. Mahmoud, Masateru Hiyoshi, Randa A. Abdelnaser, Kazuaki Monde, Nami Monde, Takaaki Koma, Hidenobu Mizuno, Sara A. Habash, Naofumi Takahashi, Yosuke Maeda, Akira Ono, Shinya Suzu

We have demonstrated that the cellular protein M-Sec promotes the transmission of human immunodeficiency virus type 1 (HIV-1) in macrophages. However, the underlying mechanism is not fully understood. Here, we report that M-Sec promotes the production of infectious HIV-1 virus. The major viral structural protein Gag distributed as many puncta in infected cells, which is one of the indicators of viral particle formation. The knockdown of M-Sec hindered the Gag puncta formation and co-localization of Gag with the viral envelope protein Env in cells, and reduced the amount of Env and infectivity of the produced virus. Consistent with these results, the over-expression of M-Sec induced the accumulation of Gag puncta, Gag/Env co-localization, and Env incorporation into virus and viral infectivity. M-Sec is known to bind phosphatidylinositol 4,5-bisphosphate (PIP2) and a small GTPase Ral, both of which were required for the M-Sec-mediated HIV-1 regulation. The exocyst complex, which is the downstream effector of Ral, was also required for the M-Sec-mediated HIV-1 regulation. Because PIP2, Ral and the exocyst complex are important for the M-Sec-mediated formation of the long plasma membrane protrusions, the present study suggests that M-Sec promotes HIV-1 transmission by acting on both cell structures and viral production through these overlapping components.

Positioning HIV SMRTcap within the HIV reservoir toolbox

2026-05-29T14:00:00Z

by Anthony Loddo, Pierre Delobel, Camille Vellas

Uridine cytidine kinases govern molnupiravir bioactivation and anti-SARS-CoV-2 activity

2026-05-29T14:00:00Z

by Huazhang Shu, Julian M. Ludäscher, Sushma Sharma, Seher Alam, Lilian Frank, Emma Scaletti Hutchinson, Marianna Tampere, Chloé Lévêque, André B.P. van Kuilenburg, Nicholas C.K. Valerie, Mikael Altun, Andrei Chabes, Pål Stenmark, Sean G. Rudd, Si Min Zhang

Molnupiravir is a nucleoside analogue antiviral drug against RNA viruses, including its clinical indication SARS-CoV-2. Whilst its mechanism-of-action is well defined, host factors that regulate its therapeutic responses have not been thoroughly deciphered and characterized. Here we show that uridine cytidine kinases (UCKs), key enzymes in pyrimidine salvage, effectively phosphorylate and thereby bioactivate N4-hydroxycytidine (NHC) – the active compound of molnupiravir, thus dictating its anti-SARS-CoV-2 efficacy and furthermore selectivity. In vitro, both isoforms of UCKs (UCK1 and UCK2) effectively phosphorylated NHC, where the structural basis of the catalysis was further deciphered via the first complete substrate bound co-crystal structure of UCK, i.e., UCK1-NHC-AMPPNP. In SARS-CoV-2-infected cells, UCK2 knockdown via siRNA hampered the intracellular accumulation of the tri-phosphorylated antiviral metabolite of NHC, resulting in a 10-fold reduction of the antiviral efficacy, and surprisingly, 2-fold reduction of its selectivity, which were critically recapitulated in a dose-dependent manner using a pan-UCK inhibitor. Altogether, this work underscores UCKs as pivotal players in upholding molnupiravir efficacy and therapeutic window, and furthermore as pharmacologically tractable targets for tailoring the drug response.

Maternal antibody-mediated elimination of a Puumala hantavirus outbreak in a bank vole colony

2026-05-29T14:00:00Z

by Stephan Drewes, Julia Wyszkowska, Ewa Jaromin, Joanna Hajduk, Ilona Onik, Mateusz Konczal, Krystyna Lach, Barbara Bober-Sowa, Katarzyna Baliga-Klimczyk, Edyta T. Sadowska, Rainer G. Ulrich, Paweł Koteja

Bank voles (Myodes glareolus syn. Clethrionomys glareolus) are frequently used as an animal model in ecological and biomedical studies and are an important reservoir of viral and bacterial zoonotic pathogens, e.g., Puumala hantavirus (PUUV). Here we describe an accidental PUUV outbreak in a large bank vole laboratory colony caused by an accidental introduction of infected wild-trapped bank voles, and the successful eradication of the virus. The eradication plan was based on results of previous studies showing that maternal antibodies (MatAb) protect the young from infection for up to 40 days after weaning, four weeks longer than the estimated duration of PUUV infectivity in the environment. After ensuring that most animals were infected, 620 pairs were mated on the same day. Only females that showed PUUV-specific antibodies and produced offspring within 26 days after mating were retained. All individuals of the parental generation were euthanized before the last weaning. The weaned offspring were moved to individually ventilated cages (IVC) and repeatedly tested for the presence of PUUV-specific antibodies and RNA. A few infected or suspect animals were euthanized. The animals were then mated (in IVC) and, after producing grand-offspring generation, euthanized and tested for PUUV RNA in the lungs. No PUUV RNA was detected, and no animals showed PUUV-specific antibodies in subsequent generations. The successful clearance confirmed the protective efficiency of PUUV-specific MatAb. The procedure for PUUV clearance in the bank vole colony may represent a blueprint for similar approaches in valuable colonies of other rodents infected by similar pathogens.

Homotypic interactions between SLAMF1 receptors on innate T cells and neutrophils regulate killing of fungi

2026-05-28T14:00:00Z

by Lindsay Suarez Lau, Sarah Lichtenberger, Cleison Ledesma Taira, Bruce S. Klein, Marcel Wüthrich

Innate lymphocytes and myeloid cells communicate and play an essential part in activating neutrophils and other effector cells to kill fungi. Here, we identified that Signaling Lymphocytic Activation Molecule 1 (SLAMF1) orchestrates a cellular and molecular signaling network that activates phagocytes. We uncovered innate lymphocytes including innate CD4⁺ or TCRγδ⁺ T cells augment neutrophil killing of Blastomyces dermatitidis (Bd) in a SLAMF1 dependent manner. SLAMF1 expression on neutrophils enabled homotypic SLAMF1:SLAMF1 interactions with innate CD4⁺ T cells, which released soluble factors that activated neutrophils to kill fungi. Our work furnishes new mechanistic insight about the role of SLAMF1 in mobilizing innate immune cells to induce phagocyte-driven killing of inhaled fungi.

Correction: Serine protease-driven entry and S2 ′ cleavage flexibility of feline coronavirus during feline enterocyte infections

2026-05-28T14:00:00Z

by Bixia Chen, Luna Vanden Buijs, Nathalie Vanderheijden, Lowiese Desmarets, Jolien Van Cleemput, Hans J. Nauwynck

LuxS/AI-2 regulates phoP/phoQ by a non-canonical mechanism to enhance acid stress survival in Salmonella Typhimurium

2026-05-28T14:00:00Z

by Anmol Singh, Abhilash Vijay Nair, Shashanka Aroli, Suman Das, Subhrajit Karmakar, Raju S. Rajmani, Santanu Mukherjee, Umesh Varshney, Dipshikha Chakravortty

The intestinal milieu is largely characterized by the complex array of chemical compounds produced through the metabolic activity of resident microbiota. Enteric pathogens like Salmonella, which have evolved refined mechanisms to persist within this environment, utilize these microbial metabolites and self-produce quorum molecules as molecular cues to identify ecological niches and modulate their survival and virulence strategies. Salmonella quorum sensing involves producing and detecting universal Autoinducer-2 (AI-2) signaling molecules. Our research reveals that Salmonella Typhimurium enhances AI-2 biosynthesis and transport under acidic conditions, aiding environmental adaptation and facilitating pathogenesis in macrophages. AI-2 signaling regulates the pH-sensing two-component system genes, phoP/phoQ, ensuring cytosolic pH homeostasis, survival, and acid tolerance. It also involves regulating the lysine/cadaverine-mediated acid tolerance response and maintaining bacterial cytosolic pH. Furthermore, we investigated the mechanism of AI-2-mediated gene regulation and demonstrated that, in addition to the lsr promoter, the repressor LsrR binds the phoP promoter via its Y25 and R43 residues, thereby negatively regulating phoP expression. Additionally, this signaling ameliorates the intracellular survival by modulating Salmonella Pathogenicity Island-2 (SPI-2) regulators (ssrA/ssrB) and SPI-2 effector expression via PhoP. Mouse models demonstrate that AI-2 signaling is essential for colonizing the primary and secondary infection sites. Therefore, quorum sensing facilitates survival in hostile host environments by modulating multiple genetic targets through the AI-2/LsrR-mediated feedback loop in pathogenic bacteria.

Genetic analysis of pyrimidine biosynthetic enzymes in Plasmodium falciparum

2026-05-27T14:00:00Z

by Krithika Rajaram, Montana L. Sievert, Rubayet Elahi, James Blauwkamp, Lucas B. Dillard, Sabrina Absalon, Sean T. Prigge

The malaria parasite Plasmodium falciparum depends entirely on de novo pyrimidine synthesis, as it is unable to salvage these essential nucleotides. This reliance makes the pyrimidine biosynthesis pathway a compelling target for antimalarial drugs, with several inhibitors targeting its rate-limiting enzyme, dihydroorotate dehydrogenase (PfDHODH), already in clinical development. In this study, we investigated the roles of three other pathway enzymes: aspartate transcarbamoylase (PfATC), carbamoyl phosphate synthetase II (PfCPSII), and dihydroorotase (PfDHO). PfATC features a unique N-terminal extension predicted to serve as an apicoplast trafficking peptide. However, using antibodies against the native protein and epitope-tagged versions, we found no evidence of apicoplast localization. Knockdown of PfATC expression proved lethal and could not be rescued by an apicoplast metabolic bypass. Complementation assays further revealed that truncation of the N-terminal domain impaired parasite growth, suggesting that this region is important for PfATC function or stability in vivo. PfCPSII, which harbors large Plasmodium-specific insertions between its catalytic domains, was likewise found to be essential for parasite proliferation. To assess the role of PfDHO, we engineered parasites to salvage uracil via heterologous expression of a yeast enzyme. Deletion of PfDHO in this parasite line resulted in uracil auxotrophy, confirming the enzyme’s essential function in pyrimidine synthesis. Together, these findings reveal multiple vulnerable nodes within the pyrimidine biosynthesis pathway.

Correction: CircRNA ARFGEF1 functions as a ceRNA to promote oncogenic KSHV-encoded viral interferon regulatory factor induction of cell invasion and angiogenesis by upregulating glutaredoxin 3

2026-05-27T14:00:00Z

by Shuihong Yao, Xuemei Jia, Fei Wang, Liuxue Sheng, Pengxia Song, Yanhui Cao, Hongjuan Shi, Weifei Fan, Xiangya Ding, Shou-Jiang Gao, Chun Lu

PLOS Pathogens: New Articles

A chemical bactericide dioctyldiethylenetriamine (Xinjunan) exerts a non-lethal effect by inhibiting RpfG activity to regulate the quorum sensing system

Understanding the impact of Klebsiella pneumoniae K-Antigen based MAPS vaccine design on the immune response in animal models

Downregulation of miR-10b-3p by EBV promotes tumor growth and metastasis via ITGAV in nasopharyngeal carcinoma

Correction: Molecular response to the non-lytic peptide bac7 (1–35) triggers disruption of Klebsiella pneumoniae biofilm

Inhibition of high risk HPV31 E8^E2 repressor activity enables differentiation-independent genome amplification and E4 expression

Low frequency variants can predetermine antiviral drug resistance development in herpes simplex virus type 1

The natural history and evolution of dermatophytosis: Host immunity in acute and chronic infection

The Legionella pneumophila type IVb secretion system effector BinA subverts amino acid transport to sensitize TORC1 signaling in macrophages

Evaluating beta-tubulin variants as predictors of benzimidazole resistance across Caenorhabditis nematodes

HIV-1 BG505 SOSIP immunization induced B cell expansion targeting the 465-glycan hole, with neutralizing antibodies exhibiting distinct binding modes and mechanisms of virus inhibition

Culture-specific transcriptional drifts limit the fidelity of organoid infection models

Feedback coordination of FoxO-mediated antibacterial immunity by PDGF/VEGF signaling establishes hemolymph microbiota homeostasis in shrimp

Distinct prion conformers from brain and peripheral tissues of gene-targeted mice produce convergent CWD strain properties

Retraction: Androgen receptor transactivates KSHV noncoding RNA PAN to promote lytic replication–mediated oncogenesis: A mechanism of sex disparity in KS

ATAD3 megadalton complex in Plasmodium falciparum is essential for mitochondrial and cellular viability

Fingolimod increases cellular resistance to HIV-1 infection and limits viral reservoir size in peripheral CD4+ T-cells

Structural basis for conserved and distinct antigen recognition by a lineage of malaria-protective antibodies

Is heme metabolism a promising drug target in Toxoplasma gondii?

Yad fimbriae are triggered by host cues and enhance extraintestinal pathogenic Escherichia coli tissue colonisation during bloodstream infection

A designed peptide disrupting viral protease cleavage restores cGAS-DNA phase separation and type I interferon responses

Targeting BRD2 and BRD4 inhibit the growth of KSHV-infected immortalized endothelial cells through suppression of LANA translation

M-Sec promotes the production of infectious HIV-1 virus through the exocyst complex in macrophages

Positioning HIV SMRTcap within the HIV reservoir toolbox

Uridine cytidine kinases govern molnupiravir bioactivation and anti-SARS-CoV-2 activity

Maternal antibody-mediated elimination of a Puumala hantavirus outbreak in a bank vole colony

Homotypic interactions between SLAMF1 receptors on innate T cells and neutrophils regulate killing of fungi

Correction: Serine protease-driven entry and S2 ′ cleavage flexibility of feline coronavirus during feline enterocyte infections

LuxS/AI-2 regulates phoP/phoQ by a non-canonical mechanism to enhance acid stress survival in Salmonella Typhimurium

Genetic analysis of pyrimidine biosynthetic enzymes in Plasmodium falciparum

Correction: CircRNA ARFGEF1 functions as a ceRNA to promote oncogenic KSHV-encoded viral interferon regulatory factor induction of cell invasion and angiogenesis by upregulating glutaredoxin 3

Fingolimod increases cellular resistance to HIV-1 infection and limits viral reservoir size in peripheral CD4⁺ T-cells