Search Results (170)

Epstein–Barr virus (EBV) lytic reactivation contributes to the pathogenesis of EBV-associated epithelial malignancies, including nasopharyngeal carcinoma and gastric carcinoma, highlighting the need for therapeutic strategies targeting viral reactivation. Capsaicin exhibits anticancer and antiviral activities; however, its effects on EBV lytic reactivation remain unclear. This study investigated the effects of capsaicin on EBV lytic reactivation in EBV-positive epithelial cancer models. Capsaicin significantly suppressed the expression of lytic genes, including BZLF1, BRLF1, BMRF1, and BLLF1, and reduced EBV virion production. Proteomic analysis revealed alterations in host cellular pathways associated with metabolism, chromatin organization, and cytoskeletal regulation, whereas metabolomic profiling demonstrated perturbations in nucleotide, amino acid, and polyamine metabolism processes involved in viral DNA replication and protein synthesis. Protein–protein interaction network analysis identified key host proteins, including HSP90AB1, MYH9, and ANXA2, implicated in metabolic reprogramming, cytoskeletal organization, and stress responses. Moreover, upstream regulators associated with EBV lytic activation, including p65, AP-1, HIF-1α, and SP1, were down-regulated following capsaicin treatment. Collectively, these findings demonstrate a multitarget inhibitory effect of capsaicin on EBV lytic reactivation and support its therapeutic potential against EBV-associated epithelial malignancies. Full article

Leydig cells play a crucial role in male development, fertility, and overall health through hormone production. Brahma-related gene 1 (BRG1), the catalytic subunit of the mammalian SWI/SNF complex, is a key regulator of chromatin accessibility and governs the development and function of diverse tissues. However, its role in Leydig cells remains unclear. In this study, we first characterized the expression pattern of PR-Cre in the testes, as this Cre mouse line has been widely used for gene targeting in the female reproductive system, but its activity in the testis has never been systematically reported. We found that PR-Cre drives recombination in multiple testicular cell types, including stem/progenitor adult Leydig cells (ALCs), peritubular myoid cells, and elongated spermatids. Using PR-Cre to conditionally delete BRG1 in ALCs, we observed no detectable abnormalities in ALC development, spermatogenesis, or male fertility. Similar results were obtained using the Cyp17a1-iCre mouse line and AAV8-iCre viral delivery for BRG1 deletion. Collectively, this work demonstrates that BRG1 is dispensable for ALC development and function, while providing a comprehensive characterization of PR-Cre as a valuable new tool for male reproductive research. Full article

Gammaherpesviruses are oncogenic viruses that reprogram host cell metabolism to support viral production. Among these, murine herpesvirus 68 (MHV-68) serves as a model system for studying lytic gammaherpesvirus infection and associated host cell changes. To characterize host transcriptional alterations induced throughout lytic gammaherpesvirus infection and identify novel host pathways that may be therapeutically targeted, we performed temporal bulk RNA-sequencing of mock- and MHV-68-infected NIH 3T3 cells at various timepoints throughout the lytic cycle. Our analysis revealed widespread and progressive host gene expression changes, including robust innate immune pathways and extensive remodeling of metabolic gene expression. We further identified a strong activation of the pentose phosphate pathway (PPP) genes, accompanied by increased abundance in PPP metabolic intermediates. Pharmacological inhibition of the PPP with 6-aminonicotinamide (6-AN) reduced infectious virus production. Moreover, at the intersection of metabolic and transcriptional reprogramming, we identified infection-associated gene expression changes in chromatin-modulating enzymes, including Tet2, and their metabolite co-factors, such as α-KG. Pharmacological inhibition of Ten-Eleven Translocation (TET) enzymatic activity led to a marked decrease in infectious MHV-68 production. Collectively, these findings define a novel metabolic–epigenetic crosstalk that supports productive gammaherpesvirus replication and identifies host pathways that can be targeted to treat lytic gammaherpesvirus infections. Full article

BK and JC Polyomaviruses (BKPyV and JCPyV) are ubiquitous human pathogens capable of establishing lifelong, asymptomatic persistence in the majority of the global population. While decades of research have focused on their lytic replication cycles and the development of severe diseases, such as polyomavirus-associated nephropathy (PVAN) caused by BKPyV and progressive multifocal leukoencephalopathy (PML) caused by JCPyV, their primary evolutionary strategy is one of persistence rather than pathogenesis. This review shifts the perspective from a replication-centric framework towards an evolutionary persistence model, detailing the multi-layered host and viral determinants that maintain the homeostatic balance. At the cellular level, viral genomes are restricted by chromatinization into minichromosomes and host S-phase licensing. These constraints are reinforced by innate immune sensing and adaptive T-cell and antibody responses that curtail systemic dissemination while permitting periodic, low-level urinary shedding, which is essential for horizontal transmission. In addition to these host barriers, the viruses utilize intrinsic regulatory mechanisms to prevent excessive replication and immune detection, including the stable archetype non-coding control region (NCCR), viral microRNAs that downregulate early gene expression, and the small t antigen (STAg). Finally, we address unresolved questions regarding the full spectrum of cellular reservoirs, the molecular triggers of reactivation, and the ecological factors shaping their transmission routes. Understanding these maintenance mechanisms is crucial for refining clinical interventions and managing the rare, devastating transitions from silent persistence to lytic disease. Full article

Background and objectives: The PWWP domain of lens epithelium-derived growth factor p75 (LEDGF/p75) mediates chromatin engagement through recognition of histone H3 lysine 36 di- and trimethylation (H3K36me2/3) and nucleosomal DNA. LEDGF/p75 plays a role in multiple human diseases. In particular, its interaction with HIV-1 integrase enables viral genome integration. However, the LEDGF PWWP domain remains difficult to target with small molecules as it lacks optimally shaped binding pockets. Here, we report the generation of high-affinity nanobodies (Nbs) to investigate the structure and function of this domain. Methods: Camelids were immunized with recombinant LEDGF PWWP domain, and immune phage display libraries were screened for affinity. Selected Nbs were recombinantly expressed in E. coli and purified. Their interaction with the PWWP domain of LEDGF and its close homolog HRP-2 was characterized using size-exclusion chromatography and surface plasmon resonance. Structural characterization of the Nbs was performed using X-ray crystallography. Functional effects on chromatin engagement were evaluated using an AlphaScreen assay. Results: Nine sequence-distinct Nbs were identified, seven of which were confirmed to bind the LEDGF PWWP domain with nanomolar affinities. Five Nbs also bound the HRP-2 domain, consistent with conserved functional surfaces, while two showed reduced affinity. The crystal structures of two Nbs (NbC03 and NbH10) confirmed there were canonical immunoglobulin folds, while the latter additionally revealed a domain-swapped dimer. Moreover, NbH10 dose-dependently inhibited the interaction between full-length LEDGF/p75 and H3K36me3-modified nucleosomes in vitro. Conclusions: This work establishes a validated panel of Nbs targeting the LEDGF PWWP domain and identifies one Nb capable of functionally disrupting the LEDGF–chromatin interaction. These Nbs serve as valuable tools for functional studies and structure-based drug design. Full article

The block-and-lock strategy aims to achieve a functional cure for human immunodeficiency virus type 1 (HIV-1) infection by enforcing durable, drug-independent silencing of proviral transcription. Several latency-promoting agents have been described that effectively limit viral reactivation in vitro or in animal models. However, most approaches induce only partial or reversible transcriptional repression and have not yet been translated into safe and effective clinical interventions. This review summarizes the molecular mechanisms underlying block-and-lock strategies and critically evaluates the limitations of current candidate compounds. We highlight recent advances in understanding HIV-1 integration site selection, focusing on the roles of lens epithelium-derived growth factor p75 (LEDGF/p75) and cleavage and polyadenylation specificity factor subunit 6 (CPSF6) in directing proviral integration toward gene-dense, transcriptionally active chromatin. Pharmacological disruption of the LEDGF/p75–integrase interaction by LEDGF/p75 inhibitors (LEDGINs) redirects proviral integration toward less transcriptionally active genomic regions that are more resistant to reactivation. Recent tandem knockout experiments, however, demonstrate that CPSF6 plays a dominant role in guiding HIV-1 integration toward gene-dense, transcriptionally active chromatin. LEDGIN treatment has been linked to the preferential targeting of proviruses to heterochromatin-rich regions within the nuclear interior. By contrast, CPSF6 knockout redirects integration toward peripheral heterochromatin, especially lamina-associated domains (LADs), genomic regions typically exhibiting stronger and more stable transcriptional repression than interior heterochromatin. These findings suggest that therapeutic modulation of CPSF6 may exert a more profound and durable effect on proviral silencing within a block-and-lock framework. Nevertheless, complete CPSF6 ablation is associated with severe cellular toxicity. The challenges associated with CPSF6-related adverse effects and potential strategies to overcome these limitations are discussed. Full article

Chandipura virus (CHPV) is a neurotropic rhabdovirus associated with recurrent outbreaks of acute encephalitis in children and a high case fatality rate, particularly in India. Despite its public health relevance, the host molecular processes governing CHPV infection and disease progression remain poorly defined. To address this gap, we conducted a time-resolved transcriptomic analysis to characterize host responses to CHPV infection and to explore host-directed therapeutic opportunities. Human HEK293T cells were infected with CHPV, followed by RNA sequencing (RNA-seq) at 6, 12, 18, and 24 h post infection (hpi). Transcriptome profiling revealed a temporally ordered host response. At 6 hpi, CHPV infection was dominated by strong activation of innate immune and inflammatory pathways, including interferon-stimulated genes and cytokine signaling. Antiviral responses persisted at 12 hpi, accompanied by suppression of metabolic and translational processes, indicating a shift in host cellular priorities. By 18 hpi, metabolic reprogramming—particularly involving lipid and sphingolipid metabolism—was observed alongside altered immune signaling, consistent with viral exploitation of host cellular machinery. At 24 hpi, repression of genes involved in chromatin organization, RNA processing, spliceosome assembly, and ribosome biogenesis reflected a global transcriptional shutdown associated with cytopathic effects. Integration of temporal transcriptomic signatures enabled identification of host pathways amenable to pharmacological targeting. Selected host-directed compounds were evaluated in vitro and exhibited antiviral activity against CHPV in a neuronal cell line. Collectively, this study provides the first time-resolved transcriptomic landscape of CHPV infection in human cells and identifies host-targeted strategies relevant for antiviral development. Full article

Understanding host cell response to viral infection could lead to the identification of molecular targets that can be used for the development of diagnostics and therapeutics. In this study, we investigated human dendritic cell (DC) response to infections with Vaccinia (VAC) virus, a highly immunogenic poxvirus, and Venezuelan Equine Encephalitis (VEE) virus, a single-stranded positive-strand RNA alphavirus, using human gene expression microarrays. Comparative changes in DC mRNA expression resulting from infection by the two viruses at 1, 8, and 12 h post-infection (hpi) revealed distinct temporal dynamics. VAC infection triggered early and robust activation of pathways related to chromatin organization, DNA damage, and antigen presentation, while VEE infection exhibited delayed activation of immune signaling pathways, including interferon signaling and cytokine production. Shared pathways, such as interferon signaling and inflammasome activation, highlight universal antiviral responses and potential therapeutic targets. These findings provide a molecular framework affected by VAC and VEE that need to be validated with additional experiments, such as functional assays or in vivo studies. The specific up- or downregulation of these pathways at different time points likely dictates the overall outcome of the viral infection and could potentially lead to better understanding of the temporal regulatory dynamics of virus host response. Full article

Despite the remarkable success of antiretroviral therapy (ART) in suppressing human immunodeficiency virus type 1 (HIV-1) replication, viral persistence remains a major barrier to cure. This persistence is sustained by heterogeneous cellular reservoirs in which viral expression is tightly regulated by host-dependent molecular mechanisms. Beyond the canonical cluster of differentiation 4 (CD4+) T-cell reservoirs, HIV-1 establishes long-lived infection in myeloid cells, glial populations within the central nervous system (CNS), and additional non-canonical cellular niches, each characterized by distinct transcriptional, epigenetic, and immune environments. In this review, we synthesize recent advances in understanding how HIV-1 expression, latency, and reactivation are shaped across diverse susceptible cell types. We highlight cell-type-specific mechanisms governing viral integration, chromatin organization, transcriptional elongation, innate immune sensing, host restriction factors, and cytoskeletal regulation. Particular emphasis is placed on how host signaling pathways and immune microenvironments contribute to reservoir stability and heterogeneity, complicating eradication strategies. We further discuss immunomodulatory approaches that seek to modulate viral expression without exacerbating immune activation. By integrating molecular, cellular, and immunological perspectives, this review provides a framework for understanding HIV-1 persistence as a context-dependent process and underscores the need for cell-type-tailored strategies in HIV cure research. Full article

We previously demonstrated that human herpesvirus 6A infects papillary thyroid cancer cells (BCPAP), inducing molecular changes compatible with a tumor-promoting phenotype, including increased expression of R273H mutant TP53 (mutp53), upregulation of c-Myc, and enhanced secretion of IL-6. To investigate whether and how epigenetic mechanisms contribute to these virus-induced effects, we examined the histone methyltransferase EZH2, a key regulator of chromatin repression frequently altered in cancer. HHV-6A infection reduced EZH2 expression and global H3K27me3 levels. Pharmacological inhibition of EZH2 using DS-3201 reproduced some of the molecular effects of viral infection, including increased mutp53 stability. Both viral infection and EZH2 inhibition induced delayed upregulation of SIRT1, which mediated deacetylation-dependent stabilization of mutp53 while reducing c-Myc expression. Indeed, the inhibition of SIRT1 with EX-527 reversed mutp53 accumulation but restored c-Myc expression and increased extracellular IL-6 release. This drug also reduced cell survival, suggesting that SIRT1 supports cellular adaptation to oncogenic stress triggered by EZH2 loss. Overall, our findings identify an epigenetic axis in which the HHV-6A-mediated downregulation of EZH2 induces SIRT1, regulating mutp53 stability and c-Myc expression and reshaping inflammatory signaling to maintain cell viability. These results establish a mechanistic link between viral infection, epigenetic remodeling, and oncogenic dependency. They also suggest that targeting IL-6 signaling could represent a therapeutic vulnerability in HHV-6A-associated thyroid cancer, particularly in combination with SIRT1 inhibitors. Full article

Neutrophils are among the early responders of the innate immune system and play a key role in host defense against viral infections. Beyond their classical antimicrobial functions, neutrophils can engage in a specialized defense mechanism by releasing web-like extracellular DNA known as neutrophil extracellular traps (NETs). These extracellular traps are a mesh-like network of chromatin DNA decorated with cellular components, including histones, proteases, and antimicrobial enzymes, that function to contain and limit the spread of pathogens. While NET formation contributes to antiviral immunity, accumulating evidence indicates that excessive or dysregulated NET formation can significantly contribute to immunopathology during viral infections. Thus, depending on the context and outcome, NET formation may be viewed as a double-edged sword. Therefore, understanding the regulatory mechanisms governing NET formation and its harmful effects is critical for developing therapeutic strategies that enhance antiviral defense while minimizing tissue damage. In this review, we provide a comprehensive overview of the molecular mechanisms that drive NET formation and clearance, with a particular focus on how viruses modulate these processes to influence disease outcome. We also discuss the pathways underlying NET formation and subsequent neutrophil cell death (NETosis), including canonical and non-canonical pathways, and highlight key signaling axes involving SYK, MAPKs, and NF-κB. Using SARS-CoV-2 and hepatitis B virus as representative models, we examine how different viral components trigger, exploit, or evade NET targeting and how persistent accumulation of NETs can contribute to hyperinflammation, progressive tissue injury, and post-viral syndromes. We further explore emerging evidence linking impaired NET clearance and neutrophil heterogeneity, particularly low-density neutrophils (LDNs), to chronic inflammation and post-viral sequelae such as long COVID and autoimmune hepatitis. Finally, we summarize current and emerging therapeutic strategies aimed at modulating NET formation or enhancing NET clearance. Altogether, this review underscores the dual nature of NETs in viral infections, highlighting their potential roles in antiviral defense and tissue injury, and provides a framework for the development of targeted interventions to limit virus-induced immunopathology. Full article

Human alpha-herpesvirus 1 (HSV-1) acute infection culminates in life-long latency in sensory neurons in trigeminal ganglia and certain neurons in the central nervous system. Previously, E2F family members and glucocorticoid receptor (GR) were shown to stimulate HSV-1 and bovine herpesvirus 1 (BoHV-1) replication. Consequently, we hypothesized GR and E2F family members activate certain HSV-l promoters. To test this hypothesis, we determined if four HSV-1 ICP0 cis-regulatory modules (CRM) upstream of the ICP0 promoter were activated by E2F. GR and E2F2, but not E2F1, E2F3a, or E2F3b, cooperatively transactivate the ICP0 CRM-C, but not CRM-A, -B, or -D fragments upstream of a minimal promoter in a luciferase reporter construct. CRM-C sequences contain two E2F consensus binding sites, a GC-rich motif that E2F2 can bind, and a consensus ½ GR response element (GRE) adjacent to the consensus E2F #2 binding site. Mutating the ½ GRE or the 3 E2F binding sites significantly reduced GR- and E2F2-mediated transactivation. Chromatin immunoprecipitation studies revealed E2F2 occupied ICP0 CRM-C sequences during productive infection and mutating the E2F binding sites prevented E2F2 binding. These studies reveal GR and E2F2 transactivate ICP0-promoter activity, which may enhance viral replication in certain cell types. Full article

The World Health Organization (WHO) and International Consensus Classification (ICC) systems have classified EBV-positive NK/T-cell neoplasms in adults and EBV-positive T/NK-cell lymphoid lymphoproliferative disorders (LPD) in children. Recent molecular profiling techniques have revealed the pathogenesis of these disorders, showing interactions among EBV-encoded proteins, host immune responses, and genetic alterations. Extranodal NK/T-cell lymphoma (ENKTL) shows molecular diversity, with various subtypes (TSIM, MB, and HEA) identified through a multiomics approach. Aggressive NK-cell leukemia (ANKL) has mutations in JAK/STAT, epigenetic regulators, and TP53 pathways. EBV-positive nodal T- and NK-cell lymphoma (ENTNKL) is a new entity, distinguished by primary nodal presentation and a unique molecular profile. Severe mosquito bite allergy (SMBA), hydroa vacciniforme lymphoproliferative disorder (HVLPD), and systemic chronic active EBV disease (CAEBV) are rare childhood EBV-driven LPDs defined by clinico-pathologic criteria, with largely unexplored genomic landscapes. Studies of CAEBV samples have found ENKTL-like driver mutations, including DDX3X and KMT2D, in EBV-infected NK/T cells, while KMT2D and chromatin modifier mutations were common in HVLPD. Comprehensive molecular sequencing of SMBA and Systemic EBV-positive T-cell lymphoma of childhood remains lacking. These findings suggest all EBV⁺ NK/T-cell LPDs exist on a biological continuum of viral oncogenesis. The integration of clinical, pathological, and molecular information aims to create a more accurate classification system, enabling better risk evaluation and tailored treatment strategies for patients with these complex disorders. Full article

Plant viral diseases cause significant agricultural losses worldwide and are shaped by complex virus-host and virus-virus interactions. Unlike fungal or bacterial pathogens, viruses cannot be directly controlled with chemicals, and their management relies on insect vector control and the development of virus-resistant plant varieties. Plants deploy endogenous epigenetic (DNA/chromatin-based) and epitranscriptomic (RNA-based) mechanisms to limit viral infections. RNA silencing pathways, particularly post-transcriptional gene silencing (PTGS) mediated by small RNAs, restrict viral replication and shape viral populations. Additional layers, including RNA-directed DNA methylation (RdDM), N6-methyladenosine (m⁶A) RNA modifications, histone modifications and chromatin remodeling, further modulate host–virus interactions. DNA methylation can be inherited and may confer resistance to future generations, although its stability is partial and context-dependent. Virus-derived 24-nt small interfering RNAs (siRNAs) act as mobile signals, inducing systemic gene silencing and potentially influencing viral population dynamics. Understanding these epigenetic and epitranscriptomic mechanisms can improve virus diagnosis, pathogenesis studies and disease management, while also providing insights into viral diversity and co-infection dynamics. This review synthesizes current knowledge of these mechanisms and discusses their implications for developing sustainable antiviral strategies. Full article

Bovine leukemia virus (BLV) is a retrovirus infecting several bovid species, notably Bos taurus, where it fulfills Koch’s postulates for pathogenicity. The virus primarily targets B-lymphocytes, establishing lifelong infections that remain mostly asymptomatic but can progress to lymphocytosis or lymphoma. Transmission occurs through live infected cells via blood, milk, or transplacental routes. Despite a robust antiviral immunity, BLV replicates by producing virions (i.e., the infectious cycle) or inducing mitosis of infected cells (i.e., clonal expansion). The immune system effectively controls the infectious cycle but fails to impede clonal expansion, leading to chronic immune activation and immunosuppression. BLV modifies the transcriptome of the host cell by expressing oncogenic factors (Tax), viral microRNAs and antisense RNAs. Leukemogenesis arises from cumulative alterations of the virus (e.g., 5′-end deletions of the integrated provirus and histone modifications of the LTR promoter) and the host cell (e.g., genomic mutations and favorable chromatin integration). This model underscores a unique persistence strategy, linking chronic infection, immune evasion, and slow multistep oncogenesis in the bovine host. Full article