Search Results (752)

Human metapneumovirus (hMPV) is an important respiratory pathogen and a major cause of respiratory tract infections, particularly among vulnerable populations. Although hMPV was identified in 2001, it remains less extensively studied than other major respiratory viruses, such as influenza virus and respiratory syncytial virus (RSV), hindering the development of effective preventive and therapeutic strategies. This review examines the primary mechanisms by which hMPV evades host immune responses. The virus disrupts early innate immune signaling pathways, particularly those involved in the induction and signaling of antiviral interferons (IFNs) and modulates inflammatory responses. At the level of adaptive immunity, hMPV impairs T-cell activation and the development of long-lasting immunological memory, which may contribute to susceptibility to reinfection. The virus also alters the functions of several immune and structural cell types, including macrophages, dendritic cells, and respiratory epithelial cells. In addition, hMPV may modulate host microRNA expression to promote immune evasion and prolong infection. The recurrent nature of hMPV infections highlights the need to further investigate the immune-evasion mechanisms. Such research is essential for developing safer and more effective vaccines, antiviral agents, and immunomodulatory therapies. Full article

In recent years, advancements in gene therapy have highlighted the important role of adeno-associated viruses (AAVs) due to their favorable characteristics, such as low immunogenicity compared to other viral vectors, e.g., lentivirus and HSV, and the ability to maintain gene expression in a variety of tissues. However, the production of recombinant AAVs in biological systems can lead to variability in the biophysical properties of viral capsid proteins, primarily due to post-translational modifications (PTMs) and cleavage events during downstream processing and storage. A critical quality attribute of AAV capsids is charge variant heterogeneity, which is significantly influenced by PTMs like deamidation, phosphorylation, acetylation and glycosylation. These modifications can impact the safety and efficacy of the viral vectors. The traditional imaged capillary isoelectric focusing (iCIEF) method, which uses absorbance or fluorescence detection, has been the primary choice for characterizing charge variants. However, it often lacks the sensitivity and resolution needed for AAVs’ charge variants. We introduce an optimized, highly sensitive capillary-based Western method to measure the apparent isoelectric point (pI) and detect charge heterogeneity at the individual VP protein level under reduced denatured conditions. This approach involves generating and purifying polyclonal antibodies to detect charge variants specific to the VP1, VP2, and VP3 proteins across different AAV serotypes, including AAV1, AAV8, and AAV5. This method is a valuable tool for the characterization of AAV capsids and can be utilized for the stability assessment and analysis of in-process and purified samples during process optimization from a charge heterogeneity perspective. Full article

Stop codon readthrough is a noncanonical translation strategy employed by certain RNA viruses, in which a viral termination codon is either decoded by host near-cognate tRNAs or canonically recognized by the class I release factor (RF, eRF1 in eukaryotes). Ribosomal A-site competition between near-cognate tRNAs and eRF can shift decoding toward near-cognate tRNAs, thereby promoting non-canonical decoding events by transiently pausing termination and favoring readthrough. This review focuses on two viral cis-elements that modulate readthrough across four viral genera in which this decoding event has been experimentally validated: (i) primary sequences surrounding the stop codon (stop codon context), and (ii) downstream RNA structures. Effects of stop codon context have been observed more broadly in cellular genes, including nonsense suppression in bacteria, with mechanisms including inefficient RF association or tRNA interactions at adjacent sense codons. In eukaryotic systems, interactions with the ribosomal mRNA entry channel have been suggested. Diverse downstream structures, including gammaretroviral pseudoknots and specific structures in alpha- and coltiviruses, further stimulate readthrough in a location- and structure-sensitive manner. This effect has not been consistently observed in chikungunya and triatoviral structures, suggesting a strong dependence on local sequence and structural context. Compared with the larger number of cellular readthrough occurrences that can be detected at low efficiency by ribosome profiling, viral readthrough in mammalian systems is consistently high (>2%). Understanding the interplay between viral RNA elements and host translational machinery, including potential kinetic trapping at the termination codon, provides insights into this unusual elongation mechanism. These findings may have implications for antiviral strategies targeting these RNA elements. Full article

Antiretroviral therapy (ART) has proven effective in suppressing HIV-1 replication, but further development of HIV-1 inhibitors is continually driven by the challenge of drug resistance and viral adaptation. The HIV-1 capsid is a promising target for treatment due to its high sequence conservation as well as its crucial role in the viral life cycle. Recently, we have developed a novel capsid-targeting biologic that prevents HIV-1 replication by efficient degradation of newly synthesized capsid. Here, we have investigated the sensitivity to viral escape as well as the breadth of this biologic against HIV-1 subtypes. The capsid-targeting biologic efficiently blocked replication of different primary HIV-1 isolates, and continuous exposure of these viruses to the biologic resulted in viral breakthrough of two out of ten primary HIV-1 isolates tested. Notably, the breakthrough variants did not have amino acid changes in the nanobody epitope but primarily in the matrix region. The breakthrough variants remained sensitive to the biologic albeit to a lesser extent. In the absence of the biologic, breakthrough variants showed increased replication kinetics when compared to their parental virus, suggesting that adaption to the biologic is likely due to the increased viral production and that the target area of the biologic is too conserved for actual escape. This is further underscored by the broad specificity of the biologic as importantly the biologic blocked infection of different HIV-1 subtypes that occur worldwide (A, B, C, D, CRF01_AE, CRF02_AG). These results demonstrate the broad neutralization potential of anti-capsid biologics with a high barrier to resistance, making capsid-targeting inhibitors important for novel antiretroviral drug strategies worldwide. Full article

The human placenta is a temporary organ structured to optimize exchange between the maternal and fetal circulatory systems. Its fetal component consists of highly branched chorionic villi, which are anchored to the maternal uterine wall and project into the intervillous space. The outer surface of these villi is lined by a multinucleated, continuous layer called the syncytiotrophoblast, which is supported by an underlying layer of proliferative cytotrophoblast cells and the invasive extravillous trophoblast (EVT). This cellular bilayer forms a selective barrier that directly bathes in maternal blood, allowing for the efficient transfer of oxygen and nutrients while structurally preventing the direct mixing of maternal and fetal blood cells. Human placental studies have been stymied by ethical and accessibility constraints. Stem cell biology has now revolutionized the capacity to model human placental development, in particular with the derivation of human trophoblast stem cells (hTSCs) and organoids. Authentic, self-renewing human trophoblast stem cells (hTSCs) were first derived not from pluripotent stem cells but from primary tissue—first-trimester villous cytotrophoblasts and blastocysts. Derivation from human pluripotent stem cells (PSCs) followed only subsequently, along two principal routes: conversion of naive PSCs, which retain extraembryonic competence, and induction from primed PSCs, as well as by direct reprogramming of somatic cells to induced hTSCs. An important advance underlying these improvements is the mapping of a global reprogramming roadmap. Multi-omic and lineage-tracing experiments have mapped the stepwise transcriptional and epigenetic conversions of fibroblasts to hTSCs, including sequential chromatin reconfiguration, trophoblast gene network activation, and repression of somatic signatures. These results identify major regulatory bottlenecks and intermediate states, improving reprogramming fidelity. The derivation of stem-cell-based trophoblast organoids now enables complex modeling of placental architecture, function, and disease susceptibility in vitro. These organoids accurately recapitulate placental barrier functions and immunological features, allowing for examinations of maternal–fetal health, pregnancy disorders, and placental infection response to viruses like cytomegalovirus and SARS-CoV-2. Looking ahead, the integration of reprogramming and organoid technologies will propel patient-specific and tailor-made models for personalized diagnostics, drug screening, and mechanism studies. As we unravel the molecular ballet of trophoblast induction, such discoveries have the potential to bridge basic translational gaps in reproductive biology and maternal–fetal medicine. Full article

Members of the Genus Avipoxvirus have been reported in more than 374 avian species worldwide. Generally, poxviruses are considered to have a limited host range; however, canarypox-like viruses appear to infect a broader host range. In 2024, four juvenile common swifts in an age of 30 to 35 days from three different breeding sites of Lower Saxony, Germany, showed nodular, verrucous and crusted skin lesions of the wings, especially of the dorsal surface of the elbow and forearm region and the skin between the outer primary flight feathers. The skin on the head or the feet as well as the mucous membrane of the oral cavity was not affected. Two swifts of these cases had to be euthanized due to pox-related alterations of feather follicles of the primary flight feathers and associated feather growth disorders and loos. The other two swifts were released into the wild after recovery and successful hand-rearing. The diagnosis of a poxvirus infection is based in our cases on a combination of clinical examination, histology, transmission electron microscopy, and molecular biological investigations. The histological examination of skin lesions displayed severe heterophilic and histiocytic dermatitis with severe epithelial hyperplasia, mild orthokeratotic hyperkeratosis and cytoplasmic eosinophilic inclusion bodies (Bollinger’s inclusion bodies) within frequently swollen keratinocytes (ballooning degeneration). Using transmission electron microscopy, virions showing typical brick-shaped poxvirus morphology were visualized. Avipoxvirus-specific DNA was detected by PCR. The sequence analysis of the 176 bp amplicon revealed 100% identity to a canarypox virus and a shearwaterpox virus 2 strain. Herpesvirus- or papillomavirus-specific DNA was not detected by PCR. To our knowledge, this is the first report of an avipoxvirus infection in a swift species. Notably, in all swift cases, the disease was limited to the skin of the wings. The origin of the virus and its transmission to swifts are unknown. However, transmission from other wild birds via biting insects appears to be possible, as has been described for canarypox-like viruses. Full article

Most patients with solid tumors do not respond to immune checkpoint blockade, and inadequate T cell infiltration of the tumor parenchyma is the dominant mechanism of primary resistance. Oncolytic viruses address this problem by a distinct route: they replicate selectively within tumor cells, produce immunogenic cell death, and convert infected cells into local sources of any encoded transgene. Most armed designs to date have carried cytokine or checkpoint-antibody payloads, and chemokines have attracted comparatively little attention despite bearing directly on the trafficking bottleneck. This review synthesizes the preclinical literature on chemokine-armed oncolytic viruses across three receptor axes: CXCR3 (CXCL9, CXCL10, CXCL11), CCR5 (CCL5/RANTES), and CCR7 (CCL19). The accumulated evidence indicates that therapeutic outcome depends less on the chemokine payload itself than on the interaction between payload and viral backbone. CXCL11 outperforms its sister CXCR3 ligands not through intrinsic potency but because it is non-redundant with the endogenous chemokines induced by vesicular stomatitis virus and vaccinia, and because it largely escapes proteolytic cleavage by dipeptidyl peptidase 4 (DPP4). CCL5 has shown the most consistent activity in dual-payload designs that pair chemotaxis with a T cell survival cytokine such as IL-15. CCL19, which addresses lymphoid organization rather than effector recruitment, rests on a single published construct. One evidence gap is central: no head-to-head comparison of chemokine payloads within a single viral platform has been published. We therefore propose a translational decision framework that aligns chemokine selection with the immune contexture of the target tumor. Full article

Mammarenaviruses are enveloped, ambisense, single-stranded RNA viruses capable of causing fatal hemorrhagic fevers and severe neurological disorders in humans. Although muroid rodents have historically been recognized as the primary reservoirs for major pathogens like Lassa virus, recent surveillance has revealed a significant expansion of their host range. This review aims to synthesize current global data regarding the epidemiology of mammarenaviruses in conventional reservoirs and the emergence of novel arenaviruses in non-traditional mammalian hosts. To achieve this, we comprehensively analyzed recent molecular and metagenomic surveillance data, evolutionary studies, and epidemiological reports published worldwide. Key discoveries include Wenzhou virus in Asian house shrews, Plateau Pika virus in plateau pikas, and an independent, geographically clustered of hedgehog-associated arenaviruses across Europe. Ultimately, this review underscores the global distribution of these pathogens and the critical need for continued, multi-host surveillance worldwide. Full article

Platelets are anucleated cell fragments representing the second most abundant blood element in circulation, with approximately 100 billion new platelets released from the bone marrow daily in a healthy individual. For over a century, their hemostatic role was considered their primary function; however, the past few decades of research have revealed significant immunological functions in both innate and adaptive immunity. Through the release of mediators stored in platelet granules and the expression and realignment of a diverse array of surface receptors, platelets influence immune cells while simultaneously recognizing, reacting to, and phagocytosing offending pathogens such as viruses and bacteria. Their activation initiates signaling cascades that either amplify platelet responses or drive the activation, recruitment, migration, and maturation of immune cells to sites of infection. This narrative review synthesizes platelet biology, receptor signaling, granule physiology, and platelet interactions with innate and adaptive immune cells to provide an integrated perspective on platelet immunologic function. We examine platelets as frontline immune sentinels and evaluate their capacity to regulate both innate and adaptive immune responses, detailing specific receptors and granule contents as the mechanistic foundation for their immunologic roles. We further explore the molecular mechanisms by which platelets interact with pathogens and immune cells to drive pathogen clearance, inflammation modulation, and the interplay between thrombosis and immunity, including their contributions to chronic inflammatory disease and tumorigenesis. Full article

Mechanisms for the maintenance of chronic viruses are poorly understood, particularly for archaeal viruses. Here, we identify the product of Sulfolobus spindle-shaped virus 1 (SSV1) ORF a291 as a putative virally encoded toxin required for growth inhibition but dispensable for viral replication and virion production. Viruses lacking ORF a291 replicated their genomes and formed morphologically normal spindle-shaped particles, yet failed to inhibit the growth of uninfected Saccharolobus solfataricus. Substitution of residues at a predicted N-terminal signal peptide cleavage site abolished growth suppression without affecting replication, suggesting that secretion is essential for toxin function. Despite primary sequence divergence among fusellovirus toxin candidates, analysis of protein structure predictions revealed a conserved hydrolase-like fold across SSV1, SSV9 and SSV10 toxins. These findings demonstrate functional separation of viral replication and host growth suppression and support a model in which chronic archaeal viruses modulate host competition through antagonistic factors. This work expands the known diversity of putative viral toxins and suggests that fuselloviruses employ conserved strategies to promote persistence in extreme environments. Full article

Background/Objectives: Pandemic influenza remains a persistent global threat, and while vaccination is the primary preventive measure, conventional vaccines often induce narrow, strain-specific immunity. This study evaluated the immunogenicity, protective efficacy, and cross-protective potential of a CpG-adjuvanted trivalent inactivated influenza vaccine (CpG-TIV) administered intramuscularly at high and low doses in ferrets. Methods: Groups of influenza-seronegative ferrets received two intramuscular injections, 3 weeks apart, of high- or low-dose CpG-TIV or a commercial non-adjuvanted trivalent vaccine. Three weeks after the second immunization (Day 42), serum was obtained, and the ferrets were subsequently challenged intranasally with homologous H1N1 and influenza B viruses, as well as a heterologous drifted H3N2 strain. Clinical signs, body weight, nasal viral load, and lung histopathology were monitored following the viral challenge. Results: CpG-TIV induced significantly higher dose-dependent HI and IgG antibodies than the commercial unadjuvanted vaccine. High-dose CpG-TIV markedly reduced weight loss, clinical symptoms, nasal viral load (by up to 99%), and lung pathological damage. Notably, high-dose CpG-TIV provided significant cross-protection against heterologous H3N2, whereas the commercial vaccine showed no protective effect. At Day 42, HI GMTs in the high-dose group reached 500, 254, and 594 against H1N1, H3N2, and B strains, respectively, with a maximal 2.58 log10 reduction in H1N1 viral load. Conclusions: High-dose CpG-TIV demonstrates strong immunogenicity and robust dose-dependent homologous and heterologous cross-protection in ferrets. The combination of a CpG adjuvant and high-dose antigen broadens protection against drifted influenza viruses, overcoming the narrow coverage of conventional vaccines. These data support further clinical development of this broad-spectrum influenza vaccine candidate. Full article

Wild waterfowl constitute the primary natural reservoir of influenza A viruses, and wetlands at the convergence of major migratory flyways serve as critical hubs for viral genetic exchange. Baikal Siberia, situated at the intersection of the East African–West Asian, Central Asian, and East Asian–Australasian flyways, represents a unique yet understudied region in this context. Here we report the results of long-term virological surveillance of wild birds in the Lake Baikal basin conducted between 2018 and 2024. A total of 1036 cloacal swab samples from 28 bird species were screened, yielding 42 influenza A virus isolates belonging to 12 HA/NA subtype combinations: H1N1, H3N1, H3N2, H3N5, H3N6, H3N8, H4N6, H6N1, H6N2, H6N3, H6N8, and H12N5. Among the detected subtypes, H6 viruses—identified with four distinct neuraminidase combinations (N1, N2, N3, N8)—are of particular public health relevance owing to their documented capacity for dual-receptor binding and potential for zoonotic transmission to mammals, including humans. Full-genome sequencing followed by cluster analysis of internal gene segments identified 16 distinct segment constellations, indicating extensive reassortment. BLAST searches against the GISAID database revealed closest genetic relatives in Mongolia, South Korea, Japan, China, and Western Siberia, with more distant links to Bangladesh, Europe, and a possible intercontinental connection via the Pacific flyway. Maximum-likelihood phylogenetic analysis of the HA and NA segments confirmed that all isolates belong to the Eurasian genetic lineage, yet they are distributed across multiple clades rather than forming a single monophyletic group, reflecting the role of Buryatia as a mixing zone for genetically diverse viral populations. These findings substantially expand the understanding of influenza A virus ecology in the Lake Baikal basin and underscore the importance of continued surveillance at this key migratory crossroads in Northern Asia. Full article

Flaviviruses, encompassing notable pathogens, like Dengue, Zika, West Nile, and tick-borne encephalitis viruses, elicit complex cellular stress responses, involving pathways such as the unfolded protein response (UPR), integrated stress response (ISR), apoptosis, autophagy, and the antiviral immune response. These pathways regulate cell fate by either promoting survival to counteract virus-induced damage or triggering cell death programs under prolonged and irreparable stress. Therefore, the primary aim of flavivirus-induced cellular responses is to protect cells and hinder viral propagation. Despite cellular defenses, flaviviruses have evolved various subversion strategies, mainly involving viral proteins, which enable successful infections even when cellular responses are activated. While these cellular pathways were previously perceived as separate entities, recent studies suggest interplay and dynamic shifts among these stress response pathways, underscoring the need for further investigation in this area. In this review, we explore the key pathways activated during flavivirus infections, examine mechanisms of viral subversion, and delve into the synergy of these pathways, thereby elucidating the impact on the progression of infection. A deeper understanding of these interactions will guide future efforts to define how cellular stress responses shape flavivirus infection and leverage this knowledge toward the development of targeted antiviral strategies. Full article

Cutaneous Melanoma is a biologically heterogeneous malignancy. Although recent therapeutic advances have improved survival, durable remissions remain elusive for many patients. Surgical excision with stage-appropriate margins and selective nodal staging remains the cornerstone of curative-intent management. In contrast, conventional cytotoxic chemotherapy now plays a limited, largely palliative role given its modest efficacy and substantial toxicity. Targeted therapy with BRAF/MEK inhibitors has improved outcomes in patients with BRAF V600-mutant melanoma, resulting in rapid tumor regression and meaningful survival benefits. However, long-term disease control is frequently compromised by adaptive resistance, commonly driven by MAPK pathway reactivation or compensatory PI3K/AKT signaling. In parallel, immune checkpoint inhibitors targeting PD-1, CTLA-4, and emerging pathways have reshaped treatment across disease stages, enabling deep and sometimes durable responses. Despite this progress, primary and acquired resistance, as well as acute and chronic immune-related toxicities, continue to pose significant clinical challenges. Current therapeutic strategies focus on rational combinations of targeted therapy, checkpoint blockade, IL-2-based approaches, oncolytic viruses, and adoptive cell therapies such as tumor-infiltrating lymphocytes to enhance response depth and durability. However, these intensified regimens carry increased toxicity risks, highlighting the need for improved patient selection and monitoring. Overall, emerging evidence supports a paradigm shift toward optimized treatment sequencing, response-adapted surgical strategies, and biomarker-guided personalization to maximize clinical benefit while minimizing toxicity. Full article

Begomoviruses are among the most destructive plant viruses, causing substantial yield losses across diverse cropping systems. Their epidemiological success is driven by high genetic plasticity, broad host range, and efficient transmission by the whitefly vector Bemisia tabaci. Traditional epidemiological models based on the classical disease triangle (virus–host–vector) fail to fully capture the ecological and evolutionary complexity of begomovirus pathosystems. Increasing evidence highlights the critical role of non-cultivated plants, particularly weeds, as persistent reservoirs that maintain viral populations during off seasons, facilitate recombination, and act as primary inoculum sources for subsequent outbreaks. Here, we propose the Begomovirus Disease Tetrahedron, an integrative framework that expands the disease triangle by incorporating weeds as a fourth essential component. We synthesize current knowledge on begomovirus adaptive evolution, including genome plasticity, noncanonical protein functions, and virus–vector mutualism, alongside key ecological drivers such as seasonal dynamics, agricultural intensification, and landscape connectivity. By integrating molecular, ecological, and epidemiological perspectives, this framework provides a comprehensive understanding of begomovirus emergence and persistence, offering new insights for the development of sustainable and ecologically informed disease management strategies. Full article