Search Results (1,820)

Avian influenza (AI) significantly threatens poultry health and causes major economic losses in the poultry industry. Vaccination remains crucial for AI prevention and control. The major protective epitopes of influenza viruses are located on hemagglutinin (HA), a surface glycoprotein essential for viral infection. Most influenza vaccines induce neutralizing antibodies against HA to block viral entry. HA maturation requires the HA0 precursor to be proteolytically cleaved at a conserved site by host proteases to yield HA1 and HA2 subunits. A subsequent acidic condition triggers HA conformational changes, enabling viral–host membrane fusion. However, whether HA conformational variations affect immunogenicity remains unclear. In this study, the cleavage site of the HA gene from an H9N2 avian influenza virus was modified to block the proteolytic cleavage of the HA protein. Our results revealed distinct proteolytic patterns of certain mutants, which exhibited either increased or decreased cleavage efficiencies compared to the wild-type (WT) HA. However, none of the mutants exhibited completely abolished HA0 cleavage. To assess the immunogenicity of these variants, BALB/c mice were immunized with DNA vaccines expressing either WT or mutant HA proteins. Strikingly, the mutant HA protein with a 19-amino-acid deletion Dlt5 (P6~P1, P1’~P′13) at the cleavage site exhibited reduced cleavage efficiency and induced significantly higher HI antibody titers compared to the WT. These results offer valuable perspectives for enhancing avian influenza vaccine efficacy through strategic modification of HA cleavage properties. Full article

Parvovirus B19 is a DNA virus. Most parvoviruses infect animals; Parvovirus B19 infects humans. Parvovirus B19 is mainly transmitted through respiratory droplets during close contact, but additional routes such as transmission through contaminated blood products and vertical transmission from mother to fetus have also been documented. Infections occur throughout the year, with a seasonal increase between late winter and early summer. Clinical symptoms depend on age, and on patients’ immune status. Healthy, immunocompetent individuals experience asymptomatic or mild infections including a febrile rash; serious complications rarely appear, such as rheumatoid-like arthritis or acute myocarditis. Clusters of myocarditis cases following Parvovirus B19 infections appeared in a daycare in Thessaloniki in 2024. To molecularly and phylogenetically characterize Parvovirus B19 strains detected during a pediatric outbreak associated with elevated troponin levels and myocarditis in Northern Greece, and to compare these strains with isolates from adult cases with mild symptoms in order to explore potential associations between viral genetic variability and cardiac involvement. MinION sequencing protocol was performed for nine whole blood samples, seven belonging to children with myocarditis, and two to adults presenting mild symptoms. Statistical analysis was performed with QualiMap 2.3 and relevant tools. Phylogenetic analysis identified distinct viral groups originating from the samples investigated. A distinct branch was formed by the reference genome and the ones of the adults’ samples, while samples from children with myocarditis provided discrete branches differing from the reference one. The findings demonstrate a clear association between Parvovirus B19 infection and myocarditis in the pediatric cases analyzed. The detected viral strains, including variants identified in several samples, support the role of Parvovirus B19 as a contributing factor in post-infectious cardiac involvement. Although these results reinforce the clinical relevance of Parvovirus B19 in childhood myocarditis, expanding the sample size would allow for a more robust characterization of circulating strains and confirmation of the observed patterns. Full article

Mouse Mammary Tumor Virus (MMTV) is an established mammary carcinogen in mice, yet the relevance of MMTV-like agents to human breast cancer remains debated. Across cohorts worldwide, PCR-based detection of MMTV-like DNA, in situ RNA localization, and immunohistochemical detection of viral proteins have been reported in a subset of tumors and, in some studies, in pre-invasive lesions; however, results are heterogeneous and vulnerable to methodological confounding, including murine DNA contamination and variable assay design. Here, we synthesize the evidence through a causality-oriented framework that integrates (i) standardized multi-target detection with mandatory contamination controls, (ii) epidemiologic designs that explicitly stratify sporadic versus hereditary/BRCA-driven disease, and (iii) mechanistic endpoints that are demonstrably human-relevant (e.g., in situ viral RNA/protein in tumor cells, integration-site mapping, and functional consequences of viral gene products in human models). Given current evidence, the overall causal plausibility is best considered “possible,” rising to “probable” only for a restricted subset of sporadic tumors, provided that future studies verify bona fide infection in situ using standardized multi-target assays, rigorous murine exclusion controls, and mechanistic evidence linking viral expression and/or integration to tumor cell biology. Without these endpoints, association studies alone are unlikely to resolve causality or enable meaningful clinical translation. Full article

Hepatitis B virus (HBV) remains a major global health threat because covalently closed circular DNA (cccDNA) persists in hepatocytes and limits the efficacy of current antiviral therapies. Effective HBV research and drug screening require culture models that recapitulate the complete viral life cycle and allow for quantitative monitoring of replication. In this study, an 11-amino acid luminescent reporter, HiBiT, was inserted at multiple sites within the preS1 region of a genotype D HBV genome, and the C terminus of preS1 was identified as optimal for maintaining robust replication. We then established HepG2-B4 cells stably replicating HiBiT-HBV with HiBiT at the preS1 C terminus. Extracellular HiBiT activity and supernatant levels of HBV-DNA, HBsAg, and HBcAg increased continuously until day 42 and were reduced by nucleos(t)ide analog treatment, and cccDNA was confirmed by Southern blot analysis. Supernatants from HepG2-B4 cells infected naïve HepG2-NTCP cells and primary human hepatocytes, as shown by extracellular HiBiT activity. Transcriptome analysis revealed distinct gene expression changes in HepG2-B4 cells compared with parental HepG2 cells. These findings indicate that the HepG2-B4 system provides a rapid, quantitative, and scalable platform for HBV replication and infection studies and is suitable for mechanistic investigations and high-throughput antiviral screening. Full article

Plant RNA interference (RNAi) is a fundamental antiviral defense that relies on coordinated activities of DICER-like endonucleases (DCLs), Argonaute proteins (AGOs) and RNA-dependent RNA polymerases (RDRs). Over the past decades, studies using model and crop species have uncovered complex and often redundant roles for DCLs and RDRs in generating and amplifying virus-derived small interfering RNAs (vsiRNAs), in addition to connections with transcriptional gene silencing (TGS) and epigenetic defenses against DNA viruses. Concurrently, plant viruses have evolved diverse counterstrategies—proteinaceous RNA silencing suppressors (RSSs), exoribonuclease (XRN)-resistant noncoding RNAs, and indirect manipulation of host pathways—to evade RNAi. Driven by the co-evolutionary arms race, plants have developed sophisticated counter-countermeasures that modulate or overcome viral anti-RNAi activity. Accumulated evidence suggests that plants encode host factor genes that are activated to degrade or sequester viral components such as RSSs against viral infection. On the other hand, plants have also evolved endogenous host modulators of antiviral RNAi that can either reinforce the antiviral response or be co-opted by viruses to antagonize it, representing a furious dynamic molecular battling mechanism. Here, we review recent advances in the molecular functions of DCLs and RDRs across species, summarize newly discovered viral counter-defenses (including RNA-based suppressors), and discuss host counter-countermeasures. We research key areas—such as the roles of RDRγ-class proteins, RTL1 (RNase three-like 1)-mediated competition with DCLs, and the mechanistic impact of viral noncoding RNAs—and outline translational opportunities for improving virus resistance in crops through breeding, biotechnological approaches, and RNA-based applications. Full article

Hepatocellular carcinoma (HCC) represents the second leading cause of cancer mortality worldwide and is mostly caused by hepatitis B virus (HBV) infection. HBV can induce HCC by an indirect mechanism of continuous necro-inflammation, contributing to hepatocyte damage and promoting cancer, as well as by viral intrinsic factors. Among them, the major contributors to the development of HBV-related HCC are represented by (i) HBV DNA integration in genes modulating cell proliferation, (ii) HBV pro-oncogenic proteins, such as HBx and HBs, and (iii) the accumulation of viral mutations, enhancing the tumorigenic features of HBV proteins. The currently available antiviral treatments, based on the usage of Nucleos(t)ide analogs (NUCs), substantially control HBV replication. However, even a successful NUC treatment does not completely abrogate HCC risk, since it rarely allows achievement of an HBV functional cure, the therapeutic end-point associated with HBsAg loss and more favorable liver outcomes. To date, novel therapeutic strategies based on innovative direct antivirals (nucleic acid polymers, small interfering RNAs, antisense oligonucleotides, covalently closed circular DNA (cccDNA) inhibitors, and capsid assembly modulators) and immune-therapeutics (therapeutic vaccines, checkpoint inhibitors, and Toll-like receptor agonists) are under evaluation in clinical trials. These approaches are showing promising data in terms of an HBV functional cure, thus representing novel strategies that could be beneficial for reducing the burden of HBV-related HCC. Lastly, further efforts in drug development are necessary to identify new compounds that could achieve a sterilizing HBV cure, implying the complete elimination of cccDNA and integrated HBV DNA, the only end-point that completely eradicates HBV and its related oncogenic risk. Full article

Background: Bilateral facial nerve palsy (BFNP) is a rare clinical entity in children and is more often associated with systemic or infectious diseases than unilateral facial palsy. Epstein–Barr virus (EBV) infection is an uncommon but recognized cause of facial nerve palsy and may present with bilateral involvement. Case presentation: We report the case of a 3-year-old boy who presented with progressive bilateral facial weakness following a febrile illness with pharyngitis and cervical lymphadenopathy. Neurological examination revealed complete bilateral facial paralysis (House–Brackmann grade VI). Laboratory investigations showed lymphocytosis and confirmed acute EBV infection through positive viral capsid antigen IgM and detectable EBV DNA in peripheral blood. Cerebrospinal fluid analysis demonstrated mild pleocytosis with negative EBV DNA. Brain magnetic resonance imaging revealed unilateral enhancement of the left facial nerve. Audiologic evaluation supported peripheral facial nerve dysfunction. The patient was treated with systemic corticosteroids, vitamin B complex supplementation, artificial tears, and speech therapy, resulting in gradual and substantial clinical improvement over five months. Discussion: A review of the pediatric literature identified only six previously reported cases of EBV-associated BFNP. The pathogenesis may involve either direct viral neurotropism or a post-infectious immune-mediated mechanism. Diagnostic evaluation is essential to exclude other serious causes of BFNP, particularly Lyme disease and Guillain–Barré syndrome. Conclusions: EBV infection should be considered in the differential diagnosis of BFNP in children. Prognosis is generally favorable, although recovery may be prolonged. Further studies are needed to clarify optimal diagnostic and therapeutic approaches. Full article

Pepino mosaic virus (PepMV) is a significant threat to global tomato production, with symptom severity varying widely among strains and often leading to significant economic losses. Despite extensive studies on aggressive variants, the molecular determinants of mild symptomatology in field isolates, particularly from Korea, remain underexplored. In this study, we characterized a mildly infecting PepMV isolate from asymptomatic tomato plants during a field survey in Jeonju, South Korea. The full-length genome sequence and phylogenetic analysis classified it as a CH2 strain. A full-length cDNA infectious clone of this isolate was constructed and confirmed to induce no mosaic symptoms in tomato plants. To identify symptom determinants, targeted mutagenesis was performed in the coat protein (CP) open reading frame. Substitution mutations at CP position 236 or combined 6/155 substitutions converted the mild isolate into a severe variant, inducing strong mosaic symptoms and significantly higher viral accumulation (up to tenfold). These results demonstrated that specific CP residues act as key regulators of symptom severity in PepMV CH2 strains and provide defined severe mutants as useful tools for screening resistance in tomatoes. Although the mechanism underlying symptom modulation remains unclear, this work advanced our understanding of molecular differences between mild and severe strains and supported targeted strategies for managing this economically important virus. Full article

Mouse models for “definitive” polyomavirus nephropathy with lytic viral replication and end-organ disease (PyVN) do not exist. We aimed at defining a PyVN model in Black-Swiss mice (n = 126) by injecting newborn animals with murine polyomavirus (strain A2; 1 × 10⁵ plaque forming units) that led in all mice to a productive intrarenal infection with genetically stable, episomal MuPyV lacking latency. Animals were monitored and morphologic, immunohistochemical, molecular, genetic, and immunological analyses were conducted. Results: Within 3–6 weeks peak PyVN developed characterized by acute tubular injury, lytic replication in up to 14% of tubules (mainly collecting ducts/distal nephrons), high viral gene coverage (up to 3589 viral DNA reads/cell equivalent) and RNA expression (up to 9317 VP1-RNA reads/10⁷ RNA reads), inflammation, DNAemia, and-uria. MuPyV doubling times were high early post-infection (urine: 0.17 day–1.61 day) followed by steady slow viral clearance post day 28 (urine, half-life: 9.90 days). By 54 weeks PyVN had morphologically cleared (no chronic tissue injury) with only qPCR evidence of residual MuPyV in 17% of kidneys/mice. Infection induced an IgM/IgG response (peak plasma IgG titer at 7–30 weeks 1:20,480; low IgG titers in 92% of mice at end of follow-up after one year). During infection, episomal MuPyV remained genetically stable, without significant alterations that could have modified the course of PyVN. The mouse model resembles “definitive” PyVN in humans. It is suited for research on the pathogenesis of PyVN including virally induced tubular injury and immunologic interactions. It facilitates in vivo studies of therapeutic interventions aimed at blocking lytic intrarenalPyV replication. Full article

Kaposi’s Sarcoma-associated herpesvirus (KSHV) and Epstein–Barr virus (EBV) are oncogenic gammaherpesviruses with high prevalence in sub-Saharan Africa. Both viruses are typically acquired during childhood, establishing lifelong latency. While viral reactivation into the lytic cycle has been mainly studied in adult HIV-infected populations—and more recently in the context of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) co-infection—the dynamics of KSHV and EBV infection in children remain poorly understood. Here, we characterize pediatric patients (n = 175; median age 4.6 years; IQR 2.0–8.3) presenting with inflammatory conditions during the COVID-19 pandemic in South Africa (from July 2020 to February 2024). Including a healthy, non-inflammatory control group, we found widespread exposure to SARS-CoV-2 (70.9% seropositivity), with 72.6% of the children being seropositive for EBV and 19.4% for KSHV. There were no significant differences in seroprevalence between children with inflammatory conditions and healthy controls for any of these viruses, although SARS-CoV-2 antibody titers were significantly higher in the inflammatory group, while EBV immune responses were lower in children presenting with inflammation. Among the KSHV-seropositive children, no active viremia was detected (as determined by the absence of viral DNA in the peripheral blood). In contrast, 34.4% of EBV-seropositive children had detectable EBV viral load, with a modestly higher proportion in the inflammatory group. However, EBV viral load levels were comparable between children diagnosed with Multisystem Inflammatory Syndrome in Children (MIS-C), Kawasaki Disease (KD), and other inflammatory conditions. Logistic regression analyses revealed that increasing age was significantly associated with higher risk of SARS-CoV-2 and EBV seropositivity, but not KSHV. Notably, the risk of EBV DNA detection in the peripheral blood decreased with age. In summary, this study suggests effective immunological control of gammaherpesvirus infections in HIV-negative paediatric patients, even in the presence of inflammatory conditions that might otherwise trigger viral reactivation. Full article

HIV-1 entry into host cells culminates in integration of the reverse transcribed double-stranded viral DNA into host genes. Several lines of evidence suggest that intact, or nearly intact, HIV-1 cores—large, ~60 nm-wide structures—pass through the nuclear pore complex (NPC), and that this passage is associated with pore remodeling. Cryo-electron tomography studies support the dynamic nature of NPCs and their regulation by cytoskeleton and ATP-dependent processes. To explore NPC remodeling, we used super-resolution Stochastic Optical Reconstruction Microscopy (STORM) of U2OS cells endogenously expressing nucleoporin 96 tagged with SNAP. Single-molecule localization imaging and computational averaging resolved 8-fold symmetric nuclear pores with an average radius of ~51 nm. Depletion of cellular ATP using sodium azide or antimycin A, previously reported to reduce the size of yeast NPCs, did not significantly alter the nuclear pore radius in U2OS cells. Similarly, stressing the nuclear envelope by hypotonic or hypertonic conditions failed to induce detectable expansion or contraction of NPCs. These results indicate that the NPCs in U2OS cells do not respond to ATP depletion nor mechanical stresses on changes in pore morphology that can be resolved by STORM. Since these cells are infectable by HIV-1, we surmise that direct multivalent interactions between HIV-1 capsid and phenylalanine-glycine nucleoporins lining the pore’s interior drive the core penetration into the nucleus and the associated changes in the pore structure. Full article

Vietnam faces a hyperendemic burden of hepatitis B virus (HBV) infection, but the prevalence of occult HBV infection (OBI) and its underlying molecular mechanisms in healthy populations remain poorly understood. This study aimed to characterize the serological and molecular HBV profile of a healthy Vietnamese adult cohort in Southern Vietnam. We assessed the prevalence of occult HBV infection (OBI) and HBsAg-positivity (serving as a proxy for probable chronic infection). In this cross-sectional study, 397 healthy adults from Southern Vietnam underwent serological screening for HBsAg, anti-HBs, and anti-HBc. All participants were screened for HBV DNA using a high-sensitivity PCR assay (LOD ≥ 5 IU/mL). For all viremic cases, the full Pre-S/S region was sequenced to determine genotype and characterize escape mutations. We uncovered a high prevalence of both HBsAg-positivity (17.6%) and OBI (9.3% HBsAg-negative, HBV DNA-positive). Serological analysis revealed a massive, age-dependent reservoir of past exposure (63.7% anti-HBc) characterized by a high and increasing prevalence of the anti-HBc only profile (31.5%), a key serological marker for OBI. This trend contrasted sharply with a steep age-related decline in protective anti-HBs. The viral landscape was dominated by genotypes B (73.8%) and C (26.2%), with sub-genotypes B4 and C1 being the most prevalent. Critically, individuals with OBI carried a significantly higher burden of S gene escape mutations compared to those with HBsAg-positivity (p < 0.001). Canonical escape variants, including sG145R (21.6%), sK141R/T/E/Q (24.3%), and sT116N/A/I/S (18.9%), were exclusively or highly enriched in the OBI group. A LASSO-logistic model based on this mutational profile successfully predicted occult infection with high accuracy (AUC = 0.83). A substantial hidden reservoir of occult HBV infection exists within the healthy adult population of Vietnam, driven by a high burden of S gene escape mutations. These findings highlight the significant limitations of conventional HBsAg-only screening. They also underscore the need for comprehensive molecular surveillance to address the true scope of HBV viremia, hopefully enabling a reduction in hidden transmission of clinically significant viral variants. Full article

Introduction: The health care burden of chronic hepatitis B virus (CHB) infection can be reduced by appropriate workup, treatment, and monitoring. Methods: As a primary objective, we determined whether adequate initial hepatitis B virus (HBV) laboratory workup in CHB patients is associated with improved CHB complications risk. Secondary outcomes assessed included: mortality, hospitalization, emergency department, and liver specialist visits. We conducted a retrospective cohort study from 1 January 2012 to 31 December 2018. Participants were followed from 12 months post index event until outcome occurrence, death, loss of eligibility, or 31 March 2023. Health administrative data from Ontario, Canada was utilized. The study cohort included individuals with at least one positive result of either hepatitis B surface antigen, hepatitis B e antigen, or HBV DNA viral load documented during the study window. The exposure of interest was defined as adequate laboratory workup, defined as having subsequent quantitative HBV DNA, and alanine aminotransferase testing completed within 12 months of the index event. CHB-related complications were assessed using previously validated diagnostic codes. Modified Poisson regression modelling was used to estimate relative risks. Results: The study cohort consisted of 30,794 CHB patients, with a mean age 45.7 years. The majority were male (53.5%) and within the lowest two income quintiles (50.2%). In total, 68.0% underwent adequate workup. Individuals with adequate workup were more likely to be older, male, urban based, and of the highest racialized and newcomer populations quintile. The risk for CHB complications was 1.50 (95% CI 1.36–1.65) times greater among those with adequate workup. By multivariable analysis, adequate workup was associated with a lower risk of mortality (RR 0.78; 95% CI 0.69–0.87), all-cause hospitalizations (RR 0.77; 95% CI 0.74–0.80), all-cause (RR 0.77; 95% CI 0.75–0.78), and liver-related (RR 0.67; 95% CI 0.60–0.75) ED visits. Conclusions: Adequate CHB clinical workup is associated with improved patient outcomes. Our findings advocate for the comprehensive evaluation of CHB patients using key laboratory tests to optimize clinical management and improve long-term health outcomes. We identified gaps in the workup of young adults, females, and those residing in rural settings, which should be addressed to ensure equity of HBV care. Full article

Background: Congenital cytomegalovirus (cCMV) infection is a leading cause of neonatal morbidity. This retrospective study aimed to evaluate the efficacy of valacyclovir in reducing vertical transmission after primary maternal CMV infection and to assess the diagnostic performance of amniocentesis and prenatal imaging. Methods: Eighty-two pregnant women with confirmed primary CMV infection were included. Maternal CMV serology and viral DNA were assessed in blood and urine, with standardized prenatal care including serial ultrasound examinations and fetal MRI when indicated. Amniocentesis was offered to confirm fetal infection. Valacyclovir (8 g/day) was administered before 24 weeks’ gestation, and neonatal infection was diagnosed by CMV DNA detection in urine at birth. Statistical analyses were performed using SPSS version 27.0. Results: Most infections (62.2%) were diagnosed in the first trimester. Valacyclovir was administered in 97.6% of cases, and amniocentesis was performed in 81.7%, with CMV DNA detected in 19.4%. Among 74 live births, 23% of neonates were CMV-positive and 6.8% symptomatic. Seven infected neonates had negative amniocentesis (false-negative rate, 13.2%). Prenatal ultrasound and MRI failed to detect abnormalities in symptomatic cases. Conclusions: Valacyclovir may reduce, but does not eliminate, the risk of cCMV transmission. Negative amniocentesis does not fully exclude fetal infection, highlighting postnatal follow-up. Full article

Torque Teno Virus (TTV), a common and genetically diverse component of the human virome, is not linked to any known disease but reflects immune status. Its plasma viral load has shown clinical relevance in solid organ transplant recipients, correlating it with immunosuppression when present at high levels. However, the clinical significance of TTV viral load in hematopoietic stem cell transplantation (HSCT) recipients is less understood. This systematic review aims to evaluate whether plasma TTV DNA load directly correlates with the degree of T-cell immune reconstitution after HSCT, supporting its potential role as a biomarker for immune competence. The study protocol was registered in the PROSPERO International Prospective Register of Systematic Reviews (CRD420251116208) and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Twenty-one studies were included. The results showed concordant data about TTV kinetics with peak levels reaching approximately between +90 to +120 days after transplantation. Contradictory results have instead been found for the association of TTV load with immune parameters (lymphocyte counts, viral opportunistic infection, and development of acute graft versus host diseases). Even if a low-risk bias assessment was classified in most studies (67%), it was possible to identify important clinical and methodological differences between them, which might account for the different findings observed. Therefore, future larger studies with standardized protocols are needed to assess whether TTV viral load can serve as a reliable tool for guiding clinical decisions in the context of HSCT. Full article