Search Results (116)

Porcine circovirus type 2 (PCV2) is a globally prevalent swine pathogen that induces immunosuppression, predisposing pigs to subclinical infections. In intensive farming systems, PCV2 persistently impairs growth performance and vaccine efficacy, leading to substantial economic losses in the swine industry. Emerging evidence suggests that certain viruses exploit Suppressor of Cytokine Signaling 3 (SOCS3), a key immune checkpoint protein, to subvert host innate immunity by suppressing cytokine signaling. While SOCS3 has been implicated in various viral infections, its regulatory role in PCV2 replication remains undefined. This study aims to elucidate the mechanisms underlying the interplay between SOCS3 and PCV2 during viral pathogenesis. Porcine SOCS3 was amplified using RT-PCR and stably overexpressed in PK-15 cells through lentiviral delivery. Bioinformatics analysis facilitated the design of three siRNA candidates targeting SOCS3. We systematically investigated the effects of SOCS3 overexpression and knockdown on PCV2 replication kinetics and host antiviral responses by quantifying the viral DNA load and the mRNA levels of cytokines. PCV2 infection upregulated SOCS3 expression at both transcriptional and translational levels in PK-15 cells. Functional studies revealed that SOCS3 overexpression markedly enhanced viral replication, whereas its knockdown suppressed viral proliferation. Intriguingly, SOCS3-mediated immune modulation exhibited a divergent regulation of antiviral cytokines: PCV2-infected SOCS3-overexpressing cells showed elevated IFN-β but suppressed TNF-α expressions, whereas SOCS3 silencing conversely downregulated IFN-β while amplifying TNF-α responses. This study unveils a dual role of SOCS3 during subclinical porcine circovirus type 2 (PCV2) infection: it functions as a host-derived pro-viral factor that facilitates viral replication while simultaneously reshaping the cytokine milieu to suppress overt inflammatory responses. These findings provide novel insights into the mechanisms underlying PCV2 immune evasion and persistence and establish a theoretical framework for the development of host-targeted control strategies. Although our results identify SOCS3 as a key host determinant of PCV2 persistence, the precise molecular pathways involved require rigorous experimental validation. Full article

Recent preclinical and clinical studies have confirmed the essential role of interferons in the host’s immune response against malignant cells. Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer strongly associated with Merkel cell polyomavirus (MCPyV). Despite progress in understanding MCC pathogenesis, the role of innate immune signaling, particularly interferon-γ (IFN γ) and its downstream pathways, remains underexplored. This review summarizes recent findings on IFN-γ in MCC, highlighting its dual role in promoting both antitumor immunity and immune evasion. IFN-γ enhances cytotoxic T cell responses, upregulates MHC class I/II expression, and induces tumor cell apoptosis. Transcriptomic studies have shown that IFN-γ treatment upregulates immune-regulatory genes including PD-L1, HLA-A/B/C, and IDO1 by over threefold; it also activates APOBEC3B and 3G, contributing to antiviral defense and tumor editing. Clinically, immune checkpoint inhibitors (ICIs) such as pembrolizumab and avelumab yield objective response rates of 30–56% and two-year overall survival rates exceeding 60% in advanced MCC. However, approximately 50% of patients do not respond, in part due to IFN-γ signaling deficiencies. This review further discusses IFN-γ’s crosstalk with the STAT1/3/5 pathways and emerging combination strategies aimed at restoring immune sensitivity. Understanding these mechanisms may inform personalized immunotherapeutic approaches and guide the development of IFN-γ–based interventions in MCC. Full article

The innate immune response is an important defense against invading pathogens. Stimulator of interferon gene (STING) plays an important role in the cyclic GMP-AMP synthase (cGAS)-mediated activation of type I IFN responses. However, some viruses have evolved the ability to inhibit the function of STING and evade the host antiviral defenses. Understanding both the mechanism of action and the viruses targets of STING effector is important because of their importance to evade the host antiviral defenses. In this study, the STING (IpSTING) of Ictalurus punctatus was first identified and characterized. Subsequently, the yeast two-hybrid system (Y2HS) was used to screen for proteins from channel catfish virus (CCV, Ictalurid herpesvirus 1) that interact with IpSTING. The ORFs of the CCV were cloned into the pGBKT7 vector and expressed in the AH109 yeast strain. The bait protein expression was validated by autoactivation, and toxicity investigation compared with control (AH109 yeast strain transformed with empty pGBKT7 and pGADT7 vector). Two positive candidate proteins, ORF41 and ORF65, were identified through Y2HS screening as interacting with IpSTING. Their interactions were further validated using co-immunoprecipitation (Co-IP). This represented the first identification of interactions between IpSTING and the CCV proteins ORF41 and ORF65. The data advanced our understanding of the functions of ORF41 and ORF65 and suggested that they might contribute to the evasion of host antiviral defenses. However, the interaction mechanism between IpSTING, and CCV proteins ORF41 and ORF65 still needs to be further explored. Full article

Viral infections persistently challenge global health through immune evasion and zoonotic transmission. Dendritic cells (DCs) play a central role in antiviral immunity by detecting viral nucleic acids via conserved pattern recognition receptors, triggering interferon-driven innate responses and cross-presentation-mediated activation of cytotoxic CD8⁺ T cells. This study synthesizes DC-centric defense mechanisms against viral subversion, encompassing divergent nucleic acid sensing pathways for zoonotic DNA and RNA viruses, viral counterstrategies targeting DC maturation and interferon signaling, and functional specialization of DC subsets in immune coordination. Despite advances in DC-based vaccine platforms, clinical translation is hindered by cellular heterogeneity, immunosuppressive microenvironments, and limitations in antigen delivery. Future research should aim to enhance the efficiency of DC-mediated immunity, thereby establishing a robust scientific foundation for the development of next-generation vaccines and antiviral therapies. A more in-depth exploration of DC functions and regulatory mechanisms may unlock novel strategies for antiviral intervention, ultimately paving the way for improved prevention and treatment of viral infections. Full article

African swine fever virus (ASFV) causes global swine outbreaks, but its cellular pathogenesis is poorly understood. Using single-cell RNA data from ASFV-infected pig spleens across four timepoints, we identified macrophages as the primary viral reservoir, with infection driving lymphoid depletion and myeloid expansion. We characterized four functionally distinct macrophage subsets, including a metabolically reprogrammed SusceptibleMac population serving as the major viral niche and an AntiviralMac subset rapidly depleted during infection. Viral gene expression analysis revealed E165R as a central hub in viral replication networks, while host transcriptomics uncovered disruption of Netrin signaling pathways that may facilitate immune evasion. Pseudotime analysis revealed dynamic macrophage state transitions during infection. These findings provide a high-resolution cellular atlas of ASFV pathogenesis, revealing macrophage subset-specific responses that shape disease outcomes and identifying potential targets for therapeutic intervention. Full article

This study focuses on exploring potential inhibitors of the Marburg virus interferon inhibitory domain protein (MARV-VP35), which is responsible for immune evasion and immunosuppression during viral manifestation. A combination of in silico techniques was applied, including structure-based pharmacophore virtual screening, molecular docking, absorption, distribution, metabolism, excretion, and toxicity (ADMET) analysis, molecular dynamics (MD), and molecular stability assessment of the identified hits. The docking scores of the 14 selected ligands ranged between −6.88 kcal/mol and −5.28 kcal/mol, the latter being comparable to the control ligand. ADMET and drug likeness evaluation identified Mol_01 and Mol_09 as the most promising candidates, both demonstrating good predicted antiviral activity against viral targets. Density functional theory (DFT) calculations, along with relevant quantum chemical descriptors, correlated well with the docking score hierarchy, and molecular electrostatic potential (MEP) mapping confirmed favorable electronic distributions supporting the docking orientation. Molecular dynamics simulations further validated complex stability, with consistent root mean square deviation (RMSD), root mean square fluctuation (RMSF), and secondary structure element (SSE) profiles. These findings support Mol_01 and Mol_09 as viable candidates for experimental validation. Full article

African swine fever virus (ASFV), a highly contagious and lethal virus affecting domestic and wild pigs, has raised global concerns due to its continued spread across Europe and Asia. While traditional transmission pathways involve suids and soft ticks, this study investigates the potential role of freshwater gastropods as environmental reservoirs capable of sustaining ASFV. We analysed ASFV survival in ten gastropod species after long-term co-incubation with the virus. Viral transcriptional activity, particularly of the late gene B646L and members of the multigene family MGF505, was evaluated in snail faeces up to nine weeks post-infection. Results revealed that several gastropods, including Melanoides tuberculata, Tarebia granifera, Physa fontinalis, and Pomacea bridgesii, support long-term persistence of ASFV, accompanied by increased MGF505 gene expression. Notably, the simultaneous activation of MGF5052R and MGF50511R significantly correlated with higher B646L expression and extended viral survival, suggesting a functional role in ASFV maintenance. Conversely, antiviral (AV) activity assays showed that some gastropod faeces reduced replication of the unrelated Influenza virus, hinting at induced host defences. A negative correlation was observed between AV activity and the expression of MGF505 2R/11R, implying that ASFV may suppress antiviral responses to facilitate persistence. These findings suggest that certain gastropods may serve as overlooked environmental hosts, contributing to ASFV epidemiology via long term viral shedding. Further research is needed to clarify the mechanisms underlying ASFV–host interactions and to assess the ecological and epidemiological implications of gastropods in ASFV transmission cycles. Full article

Severe dengue is a global health threat, affecting 4 billion people, with nearly 1 million hospitalizations during epidemics and around 25,000 annual deaths. Severe dengue presentations are characterized by vascular leakage, hemorrhagic manifestations, and shock, which can lead to multiorgan failure. Recent studies highlight the crucial role of extracellular vesicles (EVs) in the pathogenesis of dengue, influencing immune response and disease progression. EVs, nanometric structures secreted by cells, mediate viral dissemination, immune modulation, and endothelial dysfunction by transporting biomolecules such as microRNAs (miRNAs) and viral proteins. Infected cell-derived EVs carry viral components, including NS protein and miRNAs like miR-21 and miR-126-5p, which compromise endothelial integrity and activate immune pathways such as Toll-like receptor, NF-κB, and JAK-STAT signaling. This, together with the immune response, leads to the release of pro-inflammatory cytokines, including TNF-α, IL-1β, IL-6, and IFN-γ. EVs also facilitate viral immune evasion by suppressing antiviral responses. Recent analyses of miRNAs within EVs suggest their potential as biomarkers for disease progression. Differentially expressed miRNAs in circulating EVs correlate with severe outcomes, providing tools for risk stratification and therapeutic monitoring. Advanced techniques, such as nanoparticle tracking analysis and flow cytometry, allow precise EV characterization, supporting their integration into clinical applications. Full article

This review explores the mechanisms by which Human Immunodeficiency Virus type 1 (HIV-1) regulatory proteins manipulate host cellular pathways to promote viral replication and immune evasion. Key viral proteins, such as Nef, Vpu, Vif, Vpr, and Env, disrupt immune defenses by downregulating surface molecules such as CD4 (Cluster of Differentiation 4) and Major Histocompatibility Complex (MHC) class I, degrading antiviral enzymes like APOBEC3G (Apolipoprotein B mRNA editing catalytic polypeptide-3G) and SAMHD1 (Sterile Alpha Motif and Histidine Aspartate domain-containing protein 1), and counteracting restriction factors including BST-2 (Bone Marrow Stromal Antigen 2)/Tetherin and SERINC5 (Serin Incorporator 5). These interactions support viral persistence and contribute to the establishment of chronic infection. Emerging therapeutic strategies aim to disrupt these HIV-host interactions to restore innate antiviral responses and enhance immune clearance. Approaches such as stabilizing host restriction factors or blocking viral antagonists offer a promising alternative to conventional antiretroviral therapy. By targeting host-dependent pathways, these interventions may reduce drug resistance, tackle latent reservoirs, and provide a pathway toward sustained viral remission or functional cure. Full article

Adaptor protein (AP) complexes are critical components of the cellular membrane transport machinery. They mediate cargo selection during endocytosis and intracellular vesicular trafficking. Five AP complexes have been characterized (AP1-5), and together their roles extend to diverse cellular processes including the homeostasis of membranous organelles, membrane protein turnover, and immune responses. Human Immunodeficiency Virus type 1 (HIV-1) and other lentiviruses co-opt these complexes to support immune evasion and the assembly of maximally infectious particles. HIV-1 Nef interacts with AP1 and AP2 to manipulate intracellular trafficking and downregulate immune-related proteins such as CD4 and MHC-I. Vpu also co-opts AP1 and AP2, modulating the innate defense protein BST2 (Tetherin) and facilitating the release of virions from infected cells. The envelope glycoprotein (Env) hijacks AP complexes to reduce its expression at the cell surface and potentially support incorporation into virus particles. Some data suggest that Gag co-opts AP3 to drive assembly at intracellular compartments. In principle, targeting the molecular interfaces between HIV-1 proteins and AP complexes is a promising therapeutic approach. Blocking these interactions should impair HIV-1’s ability to produce infectious particles and evade immune defenses, leading to novel antivirals and facilitating a cure. Full article

SARS-CoV-2 nonstructural protein (NSP) 6 is one of the factors affecting viral pathogenicity. Mutations in NSP6 continuously emerge during viral transmission and are closely associated with alterations in viral pathogenicity. This study investigated the structural and functional impacts of NSP6 mutations by analyzing NSP6 proteins from the Wuhan-Hu-1/B (WT) strain and predominant variants Alpha, XBB.1.16, BA.2.86, and JN.1 using bioinformatics, transcriptomics, and cellular experiments. The results demonstrate that the V3593F mutation decreased the β-sheet proportion and modified hydrogen bonding patterns, while the L3829F mutation enhanced structural stability by promoting random coils. The R3821K substitution exposed lysine residues, potentially enhancing molecular interactions. Combined transcriptomic profiling and functional assays revealed that WT-NSP6 significantly inhibited poly (I: C)-induced immune factor transcription and reduced the phosphorylation levels of p-IRF3 and p-STAT1, effects absent in the XBB.1.16 variant. Furthermore, WT-NSP6 markedly activated p-AKT and p-mTOR expression, with JN.1-NSP6 maintaining limited capacity to upregulate p-mTOR. However, p53 inhibitor treatment reversed Alpha-NSP6- and BA.2.86-NSP6-upregulated p-mTOR protein expression in cells. This study demonstrates that a high frequency of NSP6 mutations alters NSP6’s structure, impairing the type I interferon signaling pathway and affecting host antiviral responses through the p53-AKT-mTOR signaling pathway. These findings contribute to the understanding of evolution, immune evasion, and viral pathogenesis mechanisms, with potential implications for the development of antiviral therapies and preventive strategies for this viral infection. Full article

The innate immune response, particularly the interferon-mediated pathway, serves as the first line of defense against viral infections. During virus infection, viral pathogen-associated molecular patterns (PAMPs) are recognized by host pattern recognition receptors (PRRs), triggering downstream signaling pathways. This leads to the activation of transcription factors like IRF3, IRF7, and NF-κB, which translocate to the nucleus and induce the production of type I interferons (IFN-α and IFN-β). Once secreted, type I interferons bind to their receptors (IFNARs) on the surfaces of infected and neighboring cells, activating the JAK-STAT pathway. This results in the formation of the ISGF3 complex (composed of STAT1, STAT2, and IRF9), which translocates to the nucleus and drives the expression of interferon-stimulated genes (ISGs). Some ISGs exert antiviral effects by directly or indirectly blocking infection and replication. Among these ISGs, ISG15 plays a crucial role in the ISGylation process, a ubiquitin-like modification that tags viral and host proteins, regulating immune responses and inhibiting viral replication. However, viruses have evolved counteractive strategies to evade ISG15-mediated immunity and ISGylation. This review first outlines the PAMP-PRR-induced pathways leading to the production of cytokines and ISGs, followed by a summary of ISGylation’s role in antiviral defense and viral evasion mechanisms targeting ISG15 and ISGYlation. Full article

An exhausted antiviral immune response is observed in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and post-SARS-CoV-2 syndrome, also termed long COVID. In this study, potential mechanisms behind this exhaustion were investigated. First, the viral load of Epstein–Barr virus (EBV), human adenovirus (HAdV), human cytomegalovirus (HCMV), human herpesvirus 6 (HHV6), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was determined in sputum samples (n = 29) derived from ME/CFS patients (n = 13), healthy controls (n = 10), elderly healthy controls (n = 4), and immunosuppressed controls (n = 2). Secondly, autoantibodies (autoAbs) to type I interferon (IFN-I) in sputum were analyzed to possibly explain impaired viral immunity. We found that ME/CFS patients released EBV at a significantly higher level compared to controls (p = 0.0256). HHV6 was present in ~50% of all participants at the same level. HAdV was detected in two cases with immunosuppression and severe ME/CFS, respectively. HCMV and SARS-CoV-2 were found only in immunosuppressed controls. Notably, anti-IFN-I autoAbs in ME/CFS and controls did not differ, except in a severe ME/CFS case showing an increased level. We conclude that ME/CFS patients, compared to controls, have a significantly higher load of EBV. IFN-I autoAbs cannot explain IFN-I dysfunction, with the possible exception of severe cases, also reported in severe SARS-CoV-2. We forward that additional mechanisms, such as the viral evasion of IFN-I effect via the degradation of IFN-receptors, may be present in ME/CFS, which demands further studies. Full article

Chronic viral infections like HIV, HBV, and HCV establish persistent interactions with the host immune system, resulting in immune evasion and long-term immune dysfunction. These viruses use a range of strategies to limit host defenses, such as downregulating MHC class I, disrupting interferon signaling, altering apoptosis pathways, and suppressing cytotoxic T-cell activity. Key viral proteins, including HIV Nef, HBV X protein, and HCV NS5A, interfere with antigen presentation and JAK/STAT signaling, thereby reducing antiviral immune responses. Chronic infections induce immune exhaustion due to persistent antigen exposure, which leads to the expression of inhibitory receptors like PD-1 and CTLA-4 on T cells. Viral epigenetic changes, such as N6-methyladenosine modifications and histone deacetylation, enhance immune evasion by modulating gene expression in infected cells. Viruses further manipulate host cytokine networks by promoting an immunosuppressive environment through IL-10 and TGF-β secretion, which suppress inflammatory responses and inhibit T-cell activation. This review examines the molecular/cellular mechanisms that enable chronic viruses to escape host immunity, focusing on antigenic variation, cytokine disruption, and control of apoptotic pathways. It also addresses how host genetic factors, such as HLA polymorphisms, influence disease progression. Lastly, we discuss host-targeted therapies, including immune checkpoint inhibitors, cytokine treatments, and CRISPR. Full article

Background and Objectives: This study explores the immunological landscapes of non-melanoma skin neoplasms (NMSNs), specifically keratoacanthoma (KA), squamous cell carcinoma (SCC), and common warts (VV). Although benign, KA shares histological similarities with low-grade SCC. The tumor microenvironment (TME) plays a key role in tumor progression, affecting angiogenesis, inflammation, and immune evasion. Viral infections, particularly human papillomavirus (HPV), are linked to NMSN development, with various HPV types identified in KA. VV, caused by HPV, serves as a comparative model due to its similar etiopathogenesis. Materials and Methods: This research examines the expression of CTLA4, a critical regulator of T-cell homeostasis, and IFN-γ, a cytokine with immunomodulatory and antiviral effects, in the TME of 41 KA, 37 SCC, and 55 VV samples using multichannel immunofluorescence. Results: The analysis revealed distinct patterns of CTLA4 and IFN-γ expression. SCC exhibited a higher prevalence of CTLA4+IFN-γ+ double-positive lymphocytes, suggesting a more immunosuppressive TME. In contrast, VV showed the highest expression of CTLA4+ cells, while both KA and VV had lower expressions of IFN-γ+ lymphocytes compared to SCC. The increased presence of CTLA4+IFN-γ+ double-positive lymphocytes in SCC suggests that the co-expression of these markers may exert a stronger effect on TME modulation than CTLA4 alone. Conclusions: These findings underscore the potential of immune profiling as a diagnostic tool to differentiate between benign and malignant lesions, such as KA and SCC. Furthermore, the presence of CTLA4+IFN-γ+ lymphocytes, particularly in SCC, may serve as a biomarker for tumor progression and a potential target for future immunotherapy strategies aimed at modulating the immune response in NMSN. Full article