Search Results (135)

Viral infections remain a major threat to poultry health and production worldwide, highlighting the need for novel antiviral strategies. This study evaluated the in vitro antiviral and virucidal activities of six Thai medicinal plant extracts against herpesvirus of turkey (HVT), a non-oncogenic avian herpesvirus widely used as a live vaccine vector and employed here as a preliminary in vitro screening model. Cytotoxicity, total phenolic content (TPC), and antioxidant capacity were assessed using the MTT, Folin–Ciocalteu, DPPH, ABTS, and FRAP assays. Among the tested extracts, Caesalpinia sappan (CS) and Persicaria odorata (PO) exhibited the highest TPC and antioxidant activities and were selected for further antiviral evaluation. Both extracts significantly reduced HVT infectivity, infectious viral titers, and intracellular viral DNA levels in DF-1 cells (p < 0.01). CS produced lower infectious viral titers (1.995 × 10⁴ TCID₅₀/mL) than PO (8.24 × 10⁴ TCID₅₀/mL); however, both extracts significantly reduced viral titers compared with the untreated control (1.78 × 10⁶ TCID₅₀/mL). In the virucidal assay, pre-incubation of HVT with CS and PO significantly reduced infectious virus titers to 4.64 × 10⁴ and 2.15 × 10⁴ TCID₅₀/mL, respectively, compared with the untreated control (1.47 × 10⁶ TCID₅₀/mL) (p < 0.01). These findings identify C. sappan and P. odorata as promising sources of plant-derived compounds for future investigation as antiviral agents against avian herpesviruses. However, additional studies using virulent MDV-1, independent biological replicates, and in vivo models are required before their potential application to Marek’s disease control can be established. Full article

The increasing virulence of field strains of Marek’s disease virus (MDV), which can overcome the immunity conferred by the widely used CVI988 vaccine, underscores the need for more effective alternatives. The SC9-1 vaccine strain has demonstrated superior protective efficacy and is being increasingly adopted in China. Importantly, it harbors a unique recombinant REV-LTR insertion junction that is absent from all other MDV strains. Targeting this strain-exclusive genomic locus, this study established an SYBR Green I-based quantitative real-time PCR assay for specific detection and quantification of SC9-1 to support clinical vaccine surveillance. We designed specific primers and systematically optimized the qPCR reaction conditions. The resulting assay demonstrated high specificity, showing no cross-reactivity with other MDV strains or common avian pathogens. It achieved a sensitivity of 1.0 × 10¹ copies/μL, and reproducibility was excellent, with both intra- and inter-assay coefficients of variation below 1.0%. Furthermore, the LOD of this assay for commercial SC9-1 vaccine samples was determined to be 1.22 PFU per 200 μL sample. In conclusion, this SYBR Green I-based qPCR assay provides a specific, sensitive, and reproducible tool for the rapid quantification of the SC9-1 vaccine virus. It is fully validated for routine vaccine quality control, while exhibiting promising potential for subsequent field surveillance within MD vaccination programs. Full article

Animal infectious diseases impose severe economic burdens on livestock industries, threaten wildlife populations, and compromise food security. Although vaccination remains the cornerstone of disease prevention, conventional vaccine platforms are often constrained by safety, efficacy, or manufacturing scalability. This narrative review provides a comprehensive analysis of the state of the art in herpesvirus-vectored vaccines for veterinary applications, focusing on five well-characterized alphaherpesviruses: Bovine herpesvirus type 1 (BoHV-1), Pseudorabies virus (PRV), Marek’s disease virus (MDV), Equine herpesvirus type 1 (EHV-1), and Duck enteritis virus (DEV). The intrinsic characteristics of herpesviruses, including large, stable genomes; the capacity for foreign gene insertion; broad host tropism; and the ability to elicit robust humoral and cellular immunity, are examined, and their performance is compared with that of traditional vaccine platforms. Key advances in vectored vaccine development are highlighted, from proof-of-concept studies to the creation of advanced multivalent constructs. These approaches demonstrate protective efficacy against a range of significant animal pathogens, including foot-and-mouth disease virus, porcine reproductive and respiratory syndrome virus, avian influenza virus, infectious bursal disease virus, and West Nile virus. The literature was identified through systematic searches of PubMed, Google Scholar, and Web of Science (1990–2026), followed by title/abstract screening and reference chaining. Future directions in vector engineering, mucosal delivery, and synthetic biology approaches are considered. Herpesvirus-vectored vaccines represent a versatile platform for enhancing animal health, supporting sustainable agriculture, and mitigating zoonotic risks. Full article

The oncogenic Marek’s disease virus (MDV) triggers Marek’s disease (MD), which is a substantial threat to poultry as it transforms infected T cells into tumors. Our research identified that long non-coding RNA 9802 (lncRNA-9802) exhibits increased expression in the chicken spleen following MDV infection, with its expression being strongly associated with the expression of tumor p53-binding protein 1 (TP53BP1). The function of lncRNA-9802 in T cells transformed by MDV remains unclear. Consequently, the expression levels of lncRNA-9802 were either over-expressed or knocked down in MDV-transformed T cells, MDCC-MSB1, through lentivirus-mediated over-expression and knock down experiments. Our findings demonstrate that lncRNA-9802 induces proliferation disturbances in MDCC-MSB1 cells by causing arrest in the S phase, which is accompanied by increased expression levels of TP53BP1, p53, and p21. Activation of the p53 pathway results in elevated levels of Cyclin E and Cyclin-dependent kinase 2 (CDK2), thereby facilitating the entry of MDCC-MSB1 cells into the S phase. Concurrently, the reduced levels of Cyclin A inhibit the exit of MDCC-MSB1 cells from the S phase. By modulating the TP53BP1/p53/p21 pathway, lncRNA-9802 induces S phase arrest in MDCC-MSB1 cells, characterized by upregulation of Cyclin E and CDK2 and downregulation of Cyclin A. This research enhances the understanding of the pathogenic mechanisms of MDV and provides a foundation for identifying potential targets for antiviral drug development. Full article

Marek’s disease (MD), caused by pathogenic Marek’s disease virus serotype 1 (MDV-1), is one of the most important avian immunosuppressive and neoplastic diseases and has led to huge economic losses to the poultry industry worldwide. Rapid and accurate clinical diagnosis is of great significance for efficient control of the disease. Herein, we have established a multiplex PCR (mPCR) method to simply differentiate all of the three types of MDV, using five specific primers targeting to MDV-1 oncogene meq or MDV-2 and MDV-3/HVT gB genes. Simultaneously, it can detect any type of virulent or vaccine MDV strains in one PCR reaction, with amplicons of the short (S) and long (L)-meq of MDV-1 strains, and the gB of MDV-2 and HVT vaccine strains. Non-specific amplifications of avian leukosis virus (ALV), reticuloendotheliosis virus (REV), or fowl adenovirus virus 4 (FAdV-4) were not observed, indicating a good specificity of this method. A total of 522 clinical samples of tumor-bearing or suspected diseased birds collected from 30 poultry farms were detected. The results demonstrated that the newly developed mPCR method accurately detected and differentiated epidemic MDV-1 infections and vaccine strains, and provided nearly 100% consistency for detecting clinical wild-type infections compared with conventional PCR amplification of the meq gene. Collectively, our data has provided a highly efficient method for early differential diagnosis of MD clinical cases, virus identification and future evaluation of vaccination efficacy in healthy chicken flocks, which would be meaningful for efficient control of the disease. Full article

Background/Objectives: Long non-coding RNAs (lncRNAs) are integral to the regulation of viral tumorigenesis. We have previously identified that the chicken lncRNA-803, which responds to Marek’s disease virus (MDV), inhibits apoptosis in the chicken embryonic fibroblast cell line DF-1, accompanied by changes in the expression of the p53 protein. Nonetheless, the molecular mechanism of lncRNA-803 in apoptosis has yet to be elucidated. Methods: In this study, through lentivirus-mediated overexpression and knockdown experiments, we determined that the overexpression of lncRNA-803 induces elevated expression levels of murine double minute 2 (MDM2), murine double minute 4 (MDM4), tumor protein p53 (p53), and tumor protein p53 binding protein 1 (TP53BP1) within the p53 signaling pathway. Results: This modulation subsequently leads to an upregulation of B-cell lymphoma-2 (Bcl-2) expression, while concurrently resulting in the downregulation of cysteinyl aspartate specific proteinase 8 (Caspase-8), cysteinyl aspartate specific proteinase 9 (Caspase-9), Bcl-2 associated protein X (Bax), and cysteinyl aspartate specific proteinase 9 (Caspase-3) in the apoptosis pathway. In terms of its mechanism, lncRNA-803 functions as a molecular sponge for miR-6555-3p. lncRNA-803 engages in competitive binding with miR-6555-3p, thereby diminishing its inhibitory effect on MDM4. Conclusions: These results elucidate that lncRNA-803 modulates apoptosis in DF-1 cells through a novel competing endogenous RNA mechanism involving the miR-6555-3p/MDM4/p53 axis. These findings provide new insights into the molecular pathogenesis of MDV. Full article

Marek’s disease (MD), caused by the oncogenic Marek’s disease virus (MDV), is a highly contagious avian infection that induces lymphoproliferative tumors. The RNA-binding protein ELAVL1 is known to regulate tumor cell proliferation and apoptosis, but its role in MDV-induced oncogenesis remains unclear. This study investigated whether ELAVL1 modulates proliferation and apoptosis in the MDV-transformed MSB1 cell line and whether its effects involve the cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) pathway. MSB1 cells were transiently transfected with ELAVL1-overexpressing plasmids (pEGFP-C-ELAVL1) or ELAVL1-specific siRNA, with expression confirmed by real-time PCR (qRT-PCR). Cell proliferation was assessed using the CCK-8 assay, while cell cycle distribution and apoptosis rates were analyzed by flow cytometry. COX-2 and PGE2 expression levels were determined by qRT-PCR, Western blotting, and ELISA. Overexpression of ELAVL1 significantly promoted the proliferation of MSB1 cells, decreased transition into the G1 phase, increased the proportions of S and G2 phase cells, and suppressed apoptosis. Correspondingly, both mRNA and protein levels of COX-2 and PGE2 were significantly elevated. Conversely, ELAVL1 knockdown significantly inhibited proliferation, induced G1 phase arrest, decreased S phase cells, and significantly decreased COX-2 and PGE2 expression. These findings indicate that ELAVL1 promotes proliferation and inhibits apoptosis in MDV-transformed MSB1 cells, potentially via the COX-2/PGE2 signaling pathway. Full article

The avian immunosuppressive and neoplastic diseases are great threats to the poultry industry, causing huge economic losses worldwide. Most recently, the emerging hypervirulent variants of Marek’s disease virus (HV-MDV), partially co-infected with avian leukosis virus (ALV) and/or reticuloendotheliosis virus (REV), have been identified as the key driver of tumour outbreaks in vaccinated chicken flocks, but the role of chicken infectious anemia virus (CIAV) remains unclear. Herein, we have investigated the prevalence and co-infection of CIAV in 71 clinical tumour-bearing flocks collected from central China during 2021–2023, which has shown a CIAV positivity rate of 59.2% (42/71). Notably, the incidence of CIAV mono-infection increased significantly from 0% (0/29) in 2021 to 23.7% (9/38) in 2023, whereas CIAV + MDV co-infection decreased from 65.5% (19/29) to 31.6% (12/38). A total of 20 viral genomes of epidemic CIAV isolates from diverse sources were obtained, and the phylogenetic analysis, including 91 reference isolates were clustered into four major lineages (A–D), with clade C further subdivided into subclades C1 and C2. Clade C1 consisted predominantly of Asian isolates, with 88.5% (46/52) of the isolates originating from mainland China. Among the 20 new isolates, 17 were clustered in subclade C1, two in C2, and one in B. The VP1 gene phylogeny showed a topology largely consistent with that of the whole-genome analysis. Moreover, all newly characterized isolates contained glutamine (Q) at VP1 residue 394, a molecular marker associated with high pathogenicity. Collectively, our data suggest that prevalent HV-MDV variants together with CIAV co-infections are the primary drivers of the ongoing tumour outbreaks in Chinese poultry flocks. Notably, the significantly increased CIAV mono-infections, possibly resulting from an independently evolving lineage among circulating Chinese strains, are likely to pose a new challenge for future control of disease. Full article

Herpesvirus infections, including herpes simplex virus (HSV), Epstein–Barr virus (EBV), and cytomegalovirus (CMV), present significant challenges in diagnosis, treatment, and transmission control. Despite advances in medical technology, managing these infections remains complex due to the viruses’ ability to establish latency and their widespread prevalence. Artificial Intelligence (AI) has emerged as a transformative tool in biomedical science, enhancing our ability to understand, predict, and manage infectious diseases. In veterinary virology, AI applications offer considerable potential for improving diagnostics, forecasting outbreaks, and implementing targeted control strategies. This review explores the growing role of AI in advancing our understanding of herpesvirus infection, particularly those caused by MDV, through improved detection, transmission modeling, treatment strategies, and predictive tools. Employing AI technologies such as machine learning (ML), deep learning (DL), and natural language processing (NLP), researchers have made significant progress in addressing diagnostic limitations, modeling transmission dynamics, and identifying potential therapeutics. Furthermore, AI holds the potential to revolutionize personalized medicine, predictive analytics, and vaccine development for herpesvirus-related diseases. The review concludes by discussing ethical considerations, implementation challenges, and future research directions necessary to fully integrate AI into clinical and veterinary practice. Full article

Marek’s disease (MD), induced by the highly contagious Marek’s disease virus (MDV), remains a significant challenge to global poultry health despite extensive vaccination efforts. This study employed integrated transcriptomic and metabolomic analyses to investigate liver responses in naturally MDV-infected Wenchang chickens during late infection stages. RNA sequencing identified 959 differentially expressed genes (DEGs) between the infected and uninfected groups. Functional enrichment analysis demonstrated that these DEGs were primarily associated with canonical pathways related to metabolism and cellular processes, including lipid, carbohydrate, and amino acid metabolism, as well as the p53 signaling pathway, cell cycle, and apoptosis. Ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) detected 561 differentially expressed metabolites (DEMs), showing near-significant enrichment (p = 0.069) in phenylalanine metabolism. Integrated analysis of transcriptomics and metabolomics data highlighted that critical gene–metabolite pairs such as SGPL1-palmitaldehyde–sphinganine-1-phosphate and ME1-NADP+–malic acid potentially mediate functional crosstalk between sphingolipid metabolism and cellular redox homeostasis during viral oncogenesis. This comprehensive mapping of regulatory networks provides insights into host–virus interactions during MDV pathogenesis, offering potential applications in immunomodulation approaches, targeted therapeutic strategies, and vaccine adjuvant development. Full article

Marek’s Disease Virus (MDV) is a highly contagious pathogen in chickens, resulting in immunosuppression and T-cell lymphomas. Understanding the role of host cytokines in MDV pathogenesis is crucial for developing effective interventions. This study investigated the in vivo effects of overexpressing avian interleukin-17 (IL-17) in Marek’s disease virus infection model and its impact on T-cell populations. We utilized a recombinant pCDNA3.1 plasmid that expresses IL-17 at days 4 and 10 post-MDV infection in chickens. Our findings demonstrate that IL-17 overexpression significantly enhanced MDV replication. However, treatment with the plasmid expressing IL-17 led to a reduction in MD disease severity. Additionally, IL-17 treatment markedly altered the frequency of CD4+ and CD8α+ αβ T-cells. Specifically, at 21-dpi, there was an increase in CD3+ CD8α+ αβ T cells and a decrease in CD3+ CD4+ αβ T-cells within the spleen of chickens treated with the plasmid expressing IL-17. These modulatory effects suggest a possible mechanism by which IL-17 facilitates immune system cell activation and enhances viral persistence. This study underscores the pivotal role of IL-17 in MDV infection dynamics and offers. Full article

Background/Objectives: More than 33 billion chickens are industrially raised for meat and egg production globally and vaccinated against Marek’s disease virus (MDV). The antigenically related herpesvirus of turkey (HVT) is used as a live-attenuated vaccine, commonly provided as a recombinant vector to protect chickens against additional unrelated pathogens. Because HVT replicates in a strictly cell-associated fashion to low levels of infectious units, adherent primary chicken or duck embryo fibroblasts are infected, dislodged from the cultivation surface and distributed as cryocultures in liquid nitrogen to the site of application. Although viable cells are complex products, application of infected cells in ovo confers protection even in presence of maternal antibodies. Methods/Results: The aim of our study was to determine whether a continuous cell line in a scalable cultivation format can be used for production of HVT-based vaccines. The AGE1.CR cell line (from Muscovy duck) was found to be highly permissive in adherent cultures. Propagation in suspension, however, initially gave very low yields. The induction of cell-to-cell contacts in carrier-independent suspensions and a metabolic shock improved titers to levels suitable for vaccine production (>10⁵ infectious units/mL after infection with multiplicity of 0.001). Conclusions: Production of HVT is challenging to scale to large volumes and the reliance on embryonated eggs from biosecure facilities is complex. We demonstrate that a cell-associated HVT vector can be propagated in a carrier-independent suspension culture of AGE1.CR cells in chemically defined medium. The fed-batch production is independent of primary cells and animal-derived material and can be scaled to large volumes. Full article

Marek’s disease virus (MDV) is the etiological agent of Marek’s disease (MD), a lymphoproliferative disorder in chickens. Polymorphisms in the MDV-encoded oncoprotein Meq are shared among field strains and correlate with their virulence. The attenuated vaccine strain CVI988 harbors unique amino acid polymorphisms in Meq, particularly at positions 71, 77, and 326. In this study, we investigated the impact of these polymorphisms on Meq protein function and MDV virulence. Reporter assays revealed that the substitutions, particularly A71S and K77E, markedly impaired the transcriptional regulatory activity of Meq. To evaluate their effect on virulence, we generated a recombinant MDV based on the very virulent RB-1B strain, encoding Meq with A71S and K77E substitutions (rRB-1B_Meq71/77). Chickens infected with rRB-1B_Meq71/77 developed neither clinical signs nor lymphomas. Flow cytometry revealed no expansion of infected cells in this group, but a marked increase in CD8⁺ T and γδ T cells during early infection. Histopathological analysis also confirmed the absence of MD-associated lesions. These findings demonstrate that the polymorphisms at positions 71 and 77 in the CVI988 strain are sufficient to abolish MDV virulence. This study provides insight into the molecular basis of MDV virulence and informs the strategy for the design of more effective vaccines. Full article

Mortality from Marek’s disease virus (MDV) infection results in economic loss for the poultry industry. It is controlled by vaccination, but the virus mutates and becomes more virulent. Variation within the MHC is well known to impact the outcomes following MDV infection from research performed utilizing the White Leghorn breed, with laboratory strains of the virus. The effect of the MHC haplotype following MDV challenge was determined from six lines of commercial elite (White Plymouth Rock (two), White Leghorn (three), and Rhode Island Red (one)) egg layer lines, challenged with vv+ virus. Mortality was recorded as sire daughter averages at 16–18 weeks of age from 19 generations of data. Sires were genotyped using a set of MHC-specific SNPs, encompassing 210,000 bp. Across all lines, there was a total of 23 unique MHC haplotypes, of which 15 were found at a frequency greater than 5% and used for further analysis. A significant impact on mortality was found for 16 of the haplotypes, with 9 haplotypes associated with decreased mortality and 7 haplotypes with increased mortality. There were three haplotypes identified in more than one line, allowing cross-line comparisons. The effect of these common haplotypes was consistent (either negative, positive or neutral) between lines. Full article

The glycoprotein C (gC) of gallid alphaherpesvirus 2—better known as Marek’s disease (MD) virus (MDV)—and gallid alphaherpesvirus 3 is required for horizontal transmission in chickens. Since gC is conserved within the Alphaherpesvirinae subfamily, we hypothesized that gC was also essential for the horizontal transmission of meleagrid alphaherpesvirus 1 (MeAHV1) or turkey herpesvirus (HVT). To test this hypothesis, we generated a fluorescent protein-tagged clone of recombinant (r)HVT (vHVT47G), removed the open reading frame of HVT gC from the genome (vHΔgC), and rescued the deletion by inserting an HA-epitope tagged HVT gC (vHΔgC-R) to test their ability to transmit in chickens and turkeys. We also tested whether MDV gC could compensate for HVT gC during transmission, where HVT gC was replaced with MDV gC (vH-MDVgC). Although all viruses replicated in chickens, none spread from chicken to chicken. However, when tested in turkeys, all viruses except vHΔgC transmitted from turkey to turkey. Importantly, the rescuent virus (vHΔgC-R) and HVT expressing MDV gC (vH-MDVgC) rescued transmission, showing that HVT gC is required and MDV gC can compensate for HVT gC for turkey-to-turkey transmission. These data confirm the host-specific transmission of HVT in turkeys and suggest that the essential function of alphaherpesvirus gC proteins is conserved. This information can be exploited while generating future vaccines against MD that will affect the poultry industry worldwide. Full article