Strong innate immune response and cell death in chicken splenocytes infected with genotype VIId Newcastle disease virus

Newcastle Disease Virus Induces Profound Lymphoid Depletion with Different Patterns of Necroptosis, Necrosis, and Oxidative DNA Damage in Bursa, Spleen, and Other Lymphoid Tissues

This study delves into the pathogenesis of virulent genotype VII strains of the Newcastle disease virus (NDV), focusing on experimentally infected birds. Predominant and consistent lesions observed include bursal atrophy and extensive depletion of all lymphoid tissues. Immunohistochemistry (IHC) analysis, targeting apoptosis (Caspase-3), necroptosis (MLKL), and NDV markers, indicates that bursal atrophy is linked to a non-apoptotic programmed cell death pathway known as "necroptosis". Repair assisted damage detection (RADD) of the bursa reveal oxidative DNA damage patterns consistent with programmed cell death, aligning with MLKL expression. Contrastingly, in the spleen, our findings suggest that necrosis (non-programmed cell death) predominantly contributes to lymphoid depletion. This conclusion is supported by evidence of karyorrhexis, fibrinous inflammation, RADD analyses, and IHC. Moreover, in addition to being pathogenic in its own right, NDV caused extensive and rapid lymphoid depletion that should be expected to contribute to profound immunosuppression. The elucidation of necroptosis in NDV-infected chickens provides a good rationale to investigate this mechanism in other paramyxoviral diseases such as human measles.

The NP protein of Newcastle disease virus dictates its oncolytic activity by regulating viral mRNA translation efficiency

Newcastle disease virus (NDV) has been extensively studied as a promising oncolytic virus for killing tumor cells in vitro and in vivo in clinical trials. However, the viral components that regulate the oncolytic activity of NDV remain incompletely understood. In this study, we systematically compared the replication ability of different NDV genotypes in various tumor cells and identified NP protein determines the oncolytic activity of NDV. On the one hand, NDV strains with phenylalanine (F) at the 450th amino acid position of the NP protein (450th-F-NP) exhibit a loss of oncolytic activity. This phenotype is predominantly associated with genotype VII NDVs. In contrast, the NP protein with a leucine amino acid at this site in other genotypes (450th-L-NP) can facilitate the loading of viral mRNA onto ribosomes more effectively than 450th-F-NP. On the other hand, the NP protein from NDV strains that exhibit strong oncogenicity interacts with eIF4A1 within its 366-489 amino acid region, leading to the inhibition of cellular mRNA translation with a complex 5' UTR structure. Our study provide mechanistic insights into how highly oncolytic NDV strains selectively promote the translation of viral mRNA and will also facilitate the screening of oncolytic strains for oncolytic therapy.

Effect of Different Levels of Maternally Derived Genotype VII Newcastle Disease Virus-Specific Hemagglutination Inhibition Antibodies on Protection against Virulent Challenge in Chicks

Newcastle disease (ND), caused by the virulent Newcastle disease virus (NDV), is an acute, highly contagious, and economically significant avian disease worldwide. Vaccination is the most effective measure for controlling ND. In recent years, vaccines matched with the prevalent strains of genotype VII have been developed and are now commercially available. These vaccines can provide full protection for chickens against clinical disease and mortality after challenges with genotype VII viruses and significantly decrease virus shedding compared to conventional vaccines belonging to genotypes I and II. Vaccinated hens can transfer antibodies to their offspring through the egg yolk. Maternally derived antibodies can provide passive protection against diseases but can also interfere with vaccination efficacy early in life. This study was conducted on chicks hatched from hens vaccinated with a commercial genotype VII NDV-matched vaccine to investigate the correlation between hemagglutination inhibition (HI) antibody levels in chicks and hens and the decaying pattern of maternally derived HI antibodies, and to evaluate the protective efficacy of different levels of maternally derived HI antibodies against challenge with a virulent NDV strain of genotype VII based on survivability and virus shedding. The HI antibody titers in chicks at hatching were about 1.3 log2 lower than those in hens, indicating an antibody transfer rate of approximately 41.52%. The estimated half-life of these antibodies was about 3.2 days. The protective efficacy of maternally derived HI antibodies was positively correlated with the titer. These antibodies could effectively protect chicks against mortality when the titer was 7 log2 or higher, but they were unable to prevent virus shedding or infection even at a high titer of 11 log2. The obtained results will greatly assist producers in determining the immune status of chicks and formulating appropriate vaccination schedules against ND.

Pathologic Mechanisms of the Newcastle Disease Virus

Newcastle disease (ND) has been a consistent risk factor to the poultry industry worldwide. Its pathogen, Newcastle disease virus (NDV), is also a promising antitumor treatment candidate. The pathogenic mechanism has intrigued the great curiosity of researchers, and advances in the last two decades have been summarized in this paper. The NDV’s pathogenic ability is highly related to the basic protein structure of the virus, which is described in the Introduction of this review. The overall clinical signs and recent findings pertaining to NDV-related lymph tissue damage are then described. Given the involvement of cytokines in the overall virulence of NDV, cytokines, particularly IL6 and IFN expressed during infection, are reviewed. On the other hand, the host also has its way of antagonizing the virus, which starts with the detection of the pathogen. Thus, advances in NDV’s physiological cell mechanism and the subsequent IFN response, autophagy, and apoptosis are summarized to provide a whole picture of the NDV infection process.

In Vivo Production of HN Protein Increases the Protection Rates of a Minicircle DNA Vaccine against Genotype VII Newcastle Disease Virus

The Cre-recombinase mediated in vivo minicircle DNA vaccine platform (CRIM) provided a novel option to replace a traditional DNA vaccine. To further improve the immune response of our CRIM vaccine, we designed a dual promoter expression plasmid named pYL87 which could synthesize short HN protein under a prokaryotic in vivo promoter P_pagC and full length HN protein of genotype VII Newcastle disease virus (NDV) under the previous eukaryotic CMV promoter at the same time. Making use of the self-lysed Salmonella strain as a delivery vesicle, chickens immunized with the pYL87 construction showed an increased serum haemagglutination inhibition antibody response, as well as an increased cell proliferation level and cellular IL-4 and IL-18 cytokines, compared with the previous CRIM vector pYL47. After the virus challenge, the pYL87 vector could provide 80% protection compared to 50% protection against genotype VII NDV in pYL47 immunized chickens, indicating a promising dual promoter strategy used in vaccine design.

Efficacy of a Turkey Herpesvirus Vectored Newcastle Disease Vaccine against Genotype VII.1.1 Virus: Challenge Route Affects Shedding Pattern

The control of Newcastle disease (ND) highly relies on vaccination. Immunity provided by a ND vaccine can be characterized by measuring the level of clinical protection and reduction in challenge virus shedding. The extent of shedding depends a lot on the characteristics of vaccine used and the quality of vaccination, but influenced also by the genotype of the challenge virus. We demonstrated that vaccination of SPF chicks with recombinant herpesvirus of turkey expressing the F-gene of genotype I ND virus (rHVT-ND) provided complete clinical protection against heterologous genotype VII.1.1 ND virus strain and reduced challenge virus shedding significantly. 100% of clinical protection was achieved already by 3 weeks of age, irrespective of the challenge route (intra-muscular or intra-nasal) and vaccination blocked cloacal shedding almost completely. Interestingly, oro-nasal shedding was different in the two challenge routes: less efficiently controlled following intra-nasal than intra-muscular challenge. Differences in the shedding pattern between the two challenge routes indicate that rHVT-ND vaccine induces strong systemic immunity, that is capable to control challenge virus dissemination in the body (no cloacal shedding), even when it is a heterologous strain, but less efficiently, although highly significantly (p < 0.001) suppresses the local replication of the challenge virus in the upper respiratory mucosa and consequent oro-nasal shedding.

Improvements to the live-attenuated Newcastle disease virus vaccine using Carbopol® 940 as a stabilizer

Background and Aim:

One strategy that can be used to stabilize vaccines is to convert them into a dry powder. This can protect the integrity of the active ingredients as well as vaccine antigenicity during manufacture, storage, and transport. This study highlights the potent adjuvant activity of Carbopo^l® when used alone to stabilize live-attenuated Newcastle disease virus (NDV) vaccines or when used in a formulation together with skimmed milk. Tolerability and potency of these formulations were compared with those obtained from other local live NDV vaccines produced locally by the Veterinary Serum and Vaccine Research Institute.

Materials and Methods:

We evaluated the cellular and humoral immune responses to a locally prepared, live-attenuated LaSota virus vaccine. Vaccine formulations were stabilized with Carbopol^® 940 alone or in combination with skimmed milk.

Results:

Our results indicate that the use of Carbopol^® 940 alone to stabilize a live-attenuated LaSota vaccine resulted in enhanced cellular and humoral immunity. The antibody titer was prolonged through the 6^th week post-vaccination (5.0 log₂). Full (100%) protection was observed in response to challenge with very virulent NDV at day 21 after vaccination; there were no clinical signs or lesions on examination. Addition of Carbopol^® 940 to the live-attenuated vaccine formulation resulted in a more compact, stable, and high-quality lyophilized cake after freeze-dried lyophilization compared with that produced by stabilization with skimmed milk alone.

Conclusion:

Our data suggest that Carbopol^® 940 may improve clinical responses to live-attenuated vaccines.

Genotypes II and VIId-based inactivated Newcastle disease vaccine reduces virus shedding

In Egypt, recent outbreaks were reported in NDV-vaccinated flocks. The isolated strain was characterized as class II velogenic genotype VIId of Newcastle disease virus (NDV). In this study, three inactivated NDV vaccine formulations were prepared, the first one is LaSota (genotype II), the second one is genotype VIId and the third one is combined Lasota and genotype VIId at a proportion of 1:1. The challenge trials were conducted in SPF chicks to evaluate the efficacy of the prepared vaccines using 10⁶ EID₅₀/0.5 ml of the Egyptian genotype VIId strain of Newcastle disease virus (NDV-B7-RLQP-CH-EG-12). Our results revealed that all three prepared vaccine formulations conferred 100% protection in the vaccinated chicks. However, the combined vaccine induced the highest haemagglutination inhibition (HI) titers and neutralization indices with significant reduction in virus shedding compared to other vaccine formulations. Histopathology examination of different organs collected from vaccinated chicks post challenge indicated the protective efficacy in vaccinated groups compared to the positive control group where a score of severe lesions was shown. This study reports the efficacy of combined inactivated Lasota and genotype VIId vaccine in reducing virus shedding which is very important in controlling NDV infection in chicken.

Cytokine expression in chicken embryo fibroblasts in response to infection with virulent or lentogenic avian avulavirus 1 (AAvV-1)

To investigate cytokine expression in chicken embryo fibroblast (CEF) cells, a virulent avian avulavirus 1 (AAvV-1) strain called SG10 that rapidly causes 100% mortality in its host, and a vaccine strain (La Sota) were characterized. Real-time quantitative PCR was performed on RNA samples from CEF cells, which were collected at 0, 24, 48 and 72 h post-infection. The dynamic expression patterns of ten cytokines (TNF-α, IFN-α, IFN-β, IL-1β, IL-2, IL-6, IL-10, IL-13, IL-15 and IL-18) were investigated. The results showed that infection with lentogenic La Sota induced significantly higher levels of the antiviral cytokines IFN-α and IFN-β, proinflammatory cytokines IL-2, IL-15 and IL-18, and the anti-inflammatory cytokine IL-10, than did infection with virulent SG10. Furthermore, the SG10 strain induced dramatically higher levels of the inflammatory cytokine IL-6 than those observed in cells infected with La Sota. However, the expression patterns of the other cytokines that were tested did not show any obvious trends or statistically significant differences between cells infected with the virulent and avirulent strains. These data show that infection with lentogenic La Sota induced more effective immune responses and anti-viral effects than did infection with virulent SG10 in CEFs. Our data provide distinct expression patterns of IFNs and proinflammatory and anti-inflammatory cytokines to AAvV-1 by virulence in CEF cells.

Conserved, breed-dependent, and subline-dependent innate immune responses of Fayoumi and Leghorn chicken embryos to Newcastle disease virus infection

Newcastle disease virus (NDV) is a threat to the global poultry industry, but particularly for smallholder farmers in low- and middle-income countries. Previous reports suggest that some breeds of chickens are less susceptible to NDV infection, however, the mechanisms contributing to this are unknown. We here examined the comparative transcriptional responses of innate immune genes to NDV infection in inbred sublines of the Fayoumi and Leghorn breeds known to differ in their relative susceptibility to infection as well as at the microchromosome bearing the major histocompatability complex (MHC) locus. The analysis identified a set of five core genes, Mx1, IRF1, IRF7, STAT1, and SOCS1, that are up-regulated regardless of subline. Several genes were differentially expressed in a breed- or subline-dependent manner. The breed-dependent response involved TLR3, NOS2, LITAF, and IFIH1 in the Fayoumi versus IL8, CAMP, and CCL4 in the Leghorn. Further analysis identified subline-dependent differences in the pro-inflammatory response within the Fayoumi breed that are likely influenced by the MHC. These results have identified conserved, breed-dependent, and subline-dependent innate immune responses to NDV infection in chickens, and provide a strong framework for the future characterization of the specific roles of genes and pathways that influence the susceptibility of chickens to NDV infection.

The Ntail region of nucleocapsid protein is associated with the pathogenicity of pigeon paramyxovirus type 1 in chickens

The nucleoprotein (NP) of pigeon paramyxovirus type 1 (PPMV-1) and other paramyxoviruses plays an important role in virus proliferation. A previous study found that NP is associated with the low pathogenicity of PPMV-1 strains in chickens. Here, we investigated which domain of NP is responsible for regulating the pathogenicity of PPMV-1. We found that the Ntail sequences were more diverse for different viral genotypes compared to Ncore sequences. The chimeric rBJ-SG10Ntail strain caused more severe clinical symptoms than the parental rBJ strain, increased the viral copy number in sampled tissues and induced higher IFN-γ gene expression. This demonstrated that the Ntail sequence plays a role in regulating viral virulence. These findings increase our understanding of the Ntail of NP protein and the virulence factors associated with PPMV-1.

Differential expression of type I interferon mRNA and protein levels induced by virulent Marek's disease virus infection in chickens

Marek's disease virus (MDV), an α-herpesvirus targeting avian species, causes fatal Marek's disease (MD) in chickens. The host interferon (IFN) responses play a key role in resisting viral infection. However, host IFN responses following MDV infection in the chicken central immune organs (thymus and bursa of Fabricius), which contain numerous MDV target cells, is poorly understood. In this study, we performed animal experiments in specific pathogen-free chickens infected with two virulent MDV strains (BS/15 and Md5) or without infection as negative controls. Specifically, the type I IFN (IFN-α and IFN-β) transcriptional and proteomic expression levels at 7, 10, 14, 17, and 21 days post infection (dpi) were detected and analyzed. Our results indicated that the mRNA and protein expression levels of IFN-α and IFN-β in the thymus and bursa of Fabricius were mainly downregulated in cytolytic infection (such as 10 dpi) and reactivation (such as 17 dpi) stages, but not the latent (such as 14 dpi) stage of MDV infection, which was determined by comprehensively analyzing the MDV viral load and immune organ damage caused by MDV infection. These data suggest that MDV could inhibit the expression of host type I IFNs, which may be involved in the MDV-induced host immunosuppression and contribute to the immune escape of MDV from host immunity. Furthermore, we found that the downregulated expression of the host type I IFNs induced by BS/15 and Md5 infection was significantly different, which we speculated may be related to the diverse virulence and pathogenicity of MDV strains. In conclusion, our study demonstrated that MDV mostly inhibited the expression of type I IFNs in infected hosts, which may be associated to its pathogenesis.

Host immune responses of pigeons infected with Newcastle disease viruses isolated from pigeons

Newcastle disease (ND), affecting over 250 bird species, is caused by the Newcastle disease virus (NDV). ND is one of the leading causes of morbidity and mortality in pigeons. Most studies investigating NDV in pigeons have focused on the epidemiology and pathogenicity of the virus. However, the host immune responses in pigeons infected with NDVs remains largely unclear. In this study, we investigated the host immune responses in pigeons infected with two NDV stains, a pigeon paramyxovirus type 1(PPMV-1) strain, GZH14, and a genotype II virus, KP08. Although no mortality was observed upon infection with either virus, obvious neurological effects were observed in the GZH14-infected pigeons but not in the KP08-infected pigeons. Both viruses could replicate in the examined tissues, namely brain, lung, spleen, trachea, kidney, and bursa of Fabricius. The expression level of RIG-I, IL-6, IL-1β, CCL5, and IL-8 were up-regulated by both viruses in the brain, lung and spleen at 3 and 7 days post-infection. Notably, these proinflammatory cytokines and chemokines showed more intense expression in the brain, when induced by the GZH14 strain than with the KP08 strain. These results indicate that the intense inflammatory responses induced by PPMV-1 in the brain may be a critical determinant of neurological symptoms in pigeons infected with PPMV-1. Our study provides new insight into the pathogenicity of PPMV-1 in pigeons attributable to the host immune responses.

Comparative analysis of early immune responses induced by two strains of Newcastle disease virus in chickens

Newcastle disease, caused by virulent strain of Newcastle disease virus (NDV), is an acute, highly contagious disease that is prevalent worldwide and is responsible for serious economic losses to the poultry industry. In the current study, we compared the early immune responses in chickens infected with two strains of velogenic NDV, a duck origin, named GD strain (Md/CH/LGD/1/2005, genotype VIId), and an chicken origin, F48E9 strain (genotype IX). The viral RNA level of GD strain was significantly higher than those of F48E9 in most tissues of chicken. Furthermore, the high level of viral RNA of the GD strain was associated with a stronger immune response compared to that of F48E9, characterized by upregulated expression of some of avian β‐defensins and cytokines, most of toll‐like receptors, and some of the other immune‐related genes investigated. This study thus demonstrated differences in host early immune responses to the two NDV strains. Further studies are needed to characterize the basic molecular mechanisms involved in the host responses in chickens infected by the two NDV strains.

Deep Sequencing-Based Transcriptome Profiling Reveals Avian Interferon-Stimulated Genes and Provides Comprehensive Insight into Newcastle Disease Virus-Induced Host Responses

Newcastle disease virus (NDV) is an avian paramyxovirus that causes significant economic losses to the poultry industry worldwide, with variations in NDV pathogenicity due to the differences in virulence between strains. However, there is limited knowledge regarding the avian innate immune response to NDV infection. In this study, transcriptional profiles were obtained from chick embryo fibroblasts (CEFs) that were infected with the highly virulent NDV Herts/33 strain or the nonvirulent LaSota strain using RNA-seq. This yielded 8433 transcripts that were associated with NDV infection. This list of candidate genes was then further examined using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. It showed a high enrichment in the areas of cellular components and metabolic processes, with the cellular components possibly being associated with NDV pathogenicity. Among these 8433 transcripts, 3616 transcripts associated with interferon-stimulated genes (ISGs) were obtained; these transcripts are involved in metabolic processes, including protein phosphorylation and protein modification. These results provide further insight into the identification of genes that are involved in NDV infection. The global survey of changes in gene expression performed herein provides new insights into the complicated molecular mechanisms underlying virus and host interactions and will enable the use of new strategies to protect chickens against this virus.

Immune responses of mature chicken bone-marrow-derived dendritic cells infected with Newcastle disease virus strains with differing pathogenicity

Infection of chickens with virulent Newcastle disease virus (NDV) is associated with severe pathology and increased morbidity and mortality. The innate immune response contributes to the pathogenicity of NDV. As professional antigen-presenting cells, dendritic cells (DCs) play a unique role in innate immunity. However, the contribution of DCs to NDV infection has not been investigated in chickens. In this study, we selected two representative NDV strains, i.e., the velogenic NDV strain Chicken/Guangdong/GM/2014 (GM) and the lentogenic NDV strain La Sota, to investigate whether NDVs could infect LPS-activated chicken bone-derived marrow DCs (mature chicken BM-DCs). We compared the viral titres and innate immune responses in mature chicken BM-DCs following infection with those strains. Both NDV strains could infect mature chicken BM-DC, but the GM strain showed stronger replication capacity than the La Sota strain in mature chicken BM-DCs. Gene expression profiling showed that MDA5, LGP2, TLR3, TLR7, IFN-α, IFN-β, IFN-γ, IL-1β, IL-6, IL-18, IL-8, CCL5, IL-10, IL-12, MHC-I, and MHC-II levels were altered in mature DCs after infection with NDVs at all evaluated times postinfection. Notably, the GM strain triggered stronger innate immune responses than the La Sota strain in chicken BM-DCs. However, both strains were able to suppress the expression of some cytokines, such as IL-6 and IFN-α, in mature chicken DCs at 24 hpi. These data provide a foundation for further investigation of the role of chicken DCs in NDV infection.

Transcriptome Analysis in Spleen Reveals Differential Regulation of Response to Newcastle Disease Virus in Two Chicken Lines

Enhancing genetic resistance of chickens to Newcastle Disease Virus (NDV) provides a promising way to improve poultry health, and to alleviate poverty and food insecurity in developing countries. In this study, two inbred chicken lines with different responses to NDV, Fayoumi and Leghorn, were challenged with LaSota NDV strain at 21 days of age. Through transcriptome analysis, gene expression in spleen at 2 and 6 days post-inoculation was compared between NDV-infected and control groups, as well as between chicken lines. At a false discovery rate <0.05, Fayoumi chickens, which are relatively more resistant to NDV, showed fewer differentially expressed genes (DEGs) than Leghorn chickens. Several interferon-stimulated genes were identified as important DEGs regulating immune response to NDV in chicken. Pathways predicted by IPA analysis, such as "EIF-signaling", "actin cytoskeleton organization nitric oxide production" and "coagulation system" may contribute to resistance to NDV in Fayoumi chickens. The identified DEGs and predicted pathways may contribute to differential responses to NDV between the two chicken lines and provide potential targets for breeding chickens that are more resistant to NDV.

Novel Mechanisms Revealed in the Trachea Transcriptome of Resistant and Susceptible Chicken Lines following Infection with Newcastle Disease Virus

Newcastle disease virus (NDV) has a devastating impact on poultry production in developing countries. This study examined the transcriptome of tracheal epithelial cells from two inbred chicken lines that differ in NDV susceptibility after challenge with a high-titer inoculum of lentogenic NDV. The Fayoumi line had a significantly lower NDV load postchallenge than the Leghorn line, demonstrating the Fayoumi line's classification as a relatively NDV-resistant breed. Examination of the trachea transcriptome showed a large increase in immune cell infiltration in the trachea in both lines at all times postinfection. The pathways conserved across lines and at all three time points postinfection included iCOS-iCOSL signaling in T helper cells, NF-κB signaling, the role of nuclear factor of activated T cells in the regulation of the immune response, calcium-induced T lymphocyte apoptosis, phospholipase C signaling, and CD28 signaling in T helper cells. Although shared pathways were seen in the Fayoumi and Leghorn lines, each line showed unique responses as well. The downregulation of collagen and the activation of eukaryotic translation initiation factor 2 signaling in the Fayoumis relative to the Leghorns at 2 days postinfection may contribute to the resistance phenotype seen in the Fayoumis. This study provides a further understanding of host-pathogen interactions which could improve vaccine efficacy and, in combination with genome-wide association studies, has the potential to advance strategies for breeding chickens with enhanced resistance to NDV.

Roles of the Polymerase-Associated Protein Genes in Newcastle Disease Virus Virulence

The virulence of Newcastle disease virus varies greatly and is determined by multiple genetic factors. In this study, we systematically evaluated the roles of the polymerase-associated (NP, P and L) protein genes in genotype VII NDV virulence after confirming the envelope-associated (F and HN) proteins contributed greatly to NDV virulence. The results revealed that the polymerase-associated protein genes individually had certain effect on virulence, while transfer of these three genes in combination significantly affected the chimeric virus virulence, especially when the L gene was involved. These results indicated that the L protein was a major contributor to NDV virulence when combined with the homologous NP and P proteins. We also investigated viral RNA synthesis using NDV minigenome systems to assess the interaction between the NP, P, and L proteins, which showed that the activity of the polymerase-associated proteins were directly related to viral RNA transcription and replication.

Preparation of mucosal nanoparticles and polymer-based inactivated vaccine for Newcastle disease and H9N2 AI viruses

AIM

To develop a mucosal inactivated vaccines for Newcastle disease (ND) and H9N2 viruses to protect against these viruses at sites of infections through mucosal immunity.

MATERIALS AND METHODS

In this study, we prepared two new formulations for mucosal bivalent inactivated vaccine formulations for Newcastle and Avian Influenza (H9N2) based on the use of nanoparticles and polymer adjuvants. The prepared vaccines were delivered via intranasal and spray routes of administration in specific pathogen-free chickens. Cell-mediated and humoral immune response was measured as well as challenge trial was carried out. In addition, ISA71 water in oil was also evaluated.

RESULTS

Our results showed that the use of spray route as vaccination delivery method of polymer and nanoparticles Montanide™ adjuvants revealed that it enhanced the cell mediated immune response as indicated by phagocytic activity, gamma interferon and interleukin 6 responses and induced protection against challenge with Newcastle and Avian Influenza (H9N2) viruses.

CONCLUSION

The results of this study demonstrate the potentiality of polymer compared to nanoparticles adjuvantes when used via spray route. Mass application of such vaccines will add value to improve the vaccination strategies against ND virus and Avian influenza viruses.

Strong inflammatory responses and apoptosis in the oviducts of egg-laying hens caused by genotype VIId Newcastle disease virus

Background

Newcastle disease virus (NDV) can cause serious damage to the reproductive tracts of egg-laying hens and leads to egg production and quality reduction. However, the mechanism of severe pathological damage in the oviducts of egg-laying hens after NDV infection has not been fully elucidated. In this study, the correlation between the primary pathological lesions and viral load in the oviducts of egg-laying hens infected with the velogenic genotype VIId NDV strain was evaluated by pathological observation and virus detection. Subsequently, apoptosis, the expression of immune-related genes and lymphocyte infiltration into the infected oviducts were determined to explore the potential causes of the pathological changes.

Results

A higher viral load and severe tissue lesions and apoptotic bodies were observed in the oviduct of NDV-infected hens compared with the control. Immune-related genes, including TLR3/7/21, MDA5, IL-2/6/1β, IFN-β, CXCLi1/2, and CCR5, were significantly upregulated in the magnum and uterus. IL-2 presented the highest mRNA level change (137-fold) at 5 days post infection (dpi) in the magnum. Infection led to CD3⁺CD4⁺ and CD3⁺CD8α⁺ lymphocyte infiltration into the magnum of the oviduct. A higher viral load was found to be associated with pathological changes and the elevated expression of proinflammatory cytokines in the NDV-infected hens.

Conclusions

Our results indicate that the severe lesions and apoptosis in the oviducts of egg-laying hens caused by genotype VIId NDV strains are associated with the excessive release of inflammatory cytokines, chemokines and lymphocyte infiltration, which contribute to the dysfunction of the oviducts and the decrease of egg production in hens.

Pathogenicity and tissue tropism of infectious bronchitis virus is associated with elevated apoptosis and innate immune responses

To establish a characteristic host response to predict the pathogenicity and tissue tropism of infectious bronchitis viruses (IBV), we investigated innate immune responses (IIR) and apoptosis in chicken embryo kidney cells (CEKC) and tracheal organ cultures (TOC) infected with three IBV strains. Results showed nephropathogenic IBV strains 885 and QX induced greater apoptosis in CEKC than M41, which induced greater apoptosis in TOCs compared to 885 and QX. Elevated IIR is associated with tissue tropism of different IBV strains. Compared to M41, 885 and QX caused greater induction of toll like receptor 3 (TLR3), melanoma differentiation associated protein 5 (MDA5) and interferon beta (IFN-β) in CEKC. In contrast, M41 infection caused greater expression of these genes than 885 or QX in TOCs. In summary, greater levels of apoptosis and elevated levels of TLR3, MDA5 and IFN-β expression are associated with increased pathogenicity of IBV strains in renal and tracheal tissues.

Host Innate Immune Responses of Ducks Infected with Newcastle Disease Viruses of Different Pathogenicities

Though previous studies have identified two strains of duck-origin Newcastle disease virus (NDV) with varying levels of pathogenicity, the relationship between the early-phase host innate immune response, and pathogenesis of ducks infected with these strains in the lungs and thymuses remains unclear. In this study, we compared the viral distribution and mRNA expression of immune-related genes in ducks following infection with two NDV strains, Duck/CH/GD/SS/10 (SS-10) and Duck/CH/GD/NH/10 (NH-10). Both NDV strains replicated systemically in tested tissues (i.e., small intestine, cecal tonsils, brain, lung, bursa of Fabricius, thymus, and spleen) and exhibited different biological properties in duck pathogenicity. Real-time quantitative polymerase chain reaction showed that the expression of TLR3, TLR7, RIG-I, MDA5, IL-1β, IL-2, IL-6, IL-8, IFN-alpha, IFN-beta, IFN-gamma in the lungs was significantly greater than in the respective thymus genes during the early post infection stage. However, in the lungs, the expression of TLR3, TLR7, IL-1β, IL-2, IL-8, IFN-alpha, IFN-gamma, and MHC II induced by SS-10 at 72 h post-inoculation (hpi) was less than with NH-10. Furthermore, the expression of IL-6 and IFN-beta in the lungs and thymuses following infection with SS-10 was greater than that with NH-10 at 24 and 48 hpi. These results highlight important differences in host innate immune responses, courses of infection, and pathogenesis following NDV infection. Further studies should work to expand understandings of the molecular mechanisms related to NDV infection.

The M, F and HN genes of genotype VIId Newcastle disease virus are associated with the severe pathological changes in the spleen of chickens

BACKGROUND

The strains of the genotype VIId Newcastle disease virus (NDV) induce more severe tissue damage in lymphoid organs than other virulent strains. The underlying molecular mechanisms are poorly understood.

METHODS

Genotype IV NDV Herts/33 and genotype VIId NDV JS5/05 have a distinctive pathological profile in the spleen. These two strains of viruses were selected as parental viruses to generate a panel of chimeric viruses by replacing the M, F and HN genes of Herts/33 individually or in combination with the corresponding genes of JS5/05 using reverse genetic. Virulence and in vitro characteristics of the recombinant viruses were assessed. In addition, pathological changes, virus load, and transcriptional cytokine response in the spleen of chickens infected with these recombinant viruses were also analyzed.

RESULTS

Pathogenicity test showed that all chimeric viruses are virulent. In vitro characterization revealed that gene replacement did not change growth kinetics and HN expression on cell surface of the recombinant viruses. However, replacement of the M, F and HN genes resulted in apparent changes in the fusion activity. Moreover, pathological studies revealed that only inclusion of the homologous M, F and HN genes of JS5/05 in Herts/33 backbone resulted in severe pathological changes characterized by extensive necrosis in the spleen, similar to that induced by JS5/05. In addition, this gene replacement significantly increased virus replication and the levels of transcriptional cytokine response, compared to Herts/33. Conversely, inclusion of the M, F and HN genes of Herts/33 into JS5/05 backbone resulted in Herts/33-specific pathological changes and significantly decreased virus load and the expression levels of cytokine genes, compared to JS5/05.

CONCLUSIONS

The M, F and HN genes are related to the severe pathological changes in the spleen of chickens infected with genotype VIId NDV.

Expression of chicken interleukin-2 by a highly virulent strain of Newcastle disease virus leads to decreased systemic viral load but does not significantly affect mortality in chickens

BACKGROUND

In mammals, interleukin 2 (IL-2) has been shown to decrease replication or attenuate pathogenicity of numerous viral pathogens (herpes simplex virus, vaccinia virus, human respiratory syncytial virus, human immunodeficiency virus) by activating natural killer cells (NK), cytotoxic T lymphocytes and expanding subsets of memory cells. In chickens, IL-2 has been shown to activate T cells, and as such it might have the potential to affect replication and pathogenesis of Newcastle disease virus (NDV).

METHODS

To assess the effect of IL-2 during NDV infection in chickens, we produced a recombinant virulent NDV strain expressing chicken IL-2 (rZJ1-IL2). The effects of IL-2 expression were investigated in vivo using the intracerebral pathogenicity index (ICPI) in day-old chicks and pathogenesis experiments in 4-week-old chickens. In these studies, rZJ1-IL2 was compared to a control virus expressing the green fluorescent protein (rZJ1-GFP). Assessed parameters included survival curves, detailed histological and immunohistochemical grading of lesions in multiple organs, and virus isolation in blood, spleen and mucosal secretions of infected birds.

RESULTS

At the site of infection (eyelid), expression of IL-2 was demonstrated in areas of rZJ-IL2 replication, confirming IL-2 production in vivo. Compared to rZJ1-GFP strain, rZJ1-IL2 caused milder lesions and displayed decreased viral load in blood, spleen and mucosal secretions of infected birds. In the rZJ1-IL2-infected group, virus level in the blood peaked at day 4 post-infection (pi) (10(3.46) EID50 /0.1 ml) and drastically decreased at day 5 pi (10(0.9) EID50/0.1 ml), while in the rZJ1-GFP-infected group virus levels in the blood reached 10(5.35) EID50/0.1 ml at day 5. However, rZJ1-IL2-infected groups presented survival curves similar to control birds infected with rZJ1-GFP, with comparable clinical signs and 100 % mortality. Further, expression of IL-2 did not significantly affect the ICPI scores, compared to rZJ1-GFP strain.

CONCLUSIONS

Increased expression of chicken IL-2 during virulent NDV replication in naïve chickens decreased viral titers in blood, spleens, oral and cloacal secretions on day 4-5 post infection. This is consistent with the previously described role of IL-2 in enhancing the clearance of viruses in mammals, such as human respiratory syncytial virus.

Patho-epidemiological study on Genotype-XIII Newcastle disease virus infection in commercial vaccinated layer farms

Aim:

The present research work was carried out to study the patho-epidemiological aspects of Genotype-XIII Newcastle disease virus (NDV) infection in commercial layer in and around Anand, Gujarat. As the outbreaks have reported in vaccinated flocks, it was felt necessary to study the disease with respect to its changing pathogenicity and relevant aspects.

Materials and Methods:

The study comprised of patho-epidemiology of Newcastle disease (ND) by information collected from different layer farms suffering from the disease in relation to incidence pattern and mortality, duration of mortality, susceptible age, and loss due to production performance. Clinical signs were recorded based on observations. During post-mortem, gross lesions were also recorded. For histopathological examination visceral organs according to lesions were collected in 10% formalin and processed slide stained by hematoxylin and eosin for microscopic examination. Cultivation of virus was done in embryonated specific pathogen-free (SPF) eggs of 9-11 days and isolation of virus was done for haemagglutination (HA) and haemagglutination inhibition (HI) test and to identify pathotype of virus by intracerebral pathogenicity index (ICPI) test to determine the virulence of virus. The Genotype-XIII NDV was confirmed by F gene sequence and whole genome sequence.

Results:

During the study mortality due to ND was recorded in 13 layer flocks in spite of routine vaccination, which usually contain Genotype-II strain of virus. The mortality was observed as high as above 50% with an average of 21.21%. The susceptible age for disease was found to be 6-14 weeks. The duration of mortality observed was 23 days. The disease resulted in a significant reduction in body weight, feed intake and drop in egg production. Majority of the outbreaks appeared during extremely hot months of April to June. Greenish diarrhoea was frequently seen in birds that survived early in infection. Mortality continued for 2-3 weeks and reduced with appearance of torticollis. Gross lesions were characterized by multifocal to diffuse hemorrhages around proventricular glands, necrotic (diphtheritic) haemorrhagic ulcers throughout the intestine, disseminated multiple foci of necrosis and pin-point hemorrhages in the spleen parenchyma. The microscopic lesions include focal to diffuse hemorrhages, diffuse infiltration of mononuclear cells, necrosis, and degeneration in visceral organs. All the 13 farm samples (n=13) resulted in death of all the embryos following incubation up to 72 h post-inoculation. All the 13 allantois fluids from field samples along with F and R2B vaccine sample were found positive for HA activity, which was further confirmed by HI using known NDV serum. The values of ICPI were 2.0 which were indicative of velogenic nature of the field NDV strain.

Conclusion:

The study indicated that presently available live and attenuated vaccines which include Genotype-II NDV have failed in protecting the flocks against Genotype-XIII and resulted in outbreaks with mortality above 50%. ICPI score of 2.0 confirmed that the present outbreaks were due to Genotype-XIII NDV, which is velogenic in nature.

High levels of virus replication and an intense inflammatory response contribute to the severe pathology in lymphoid tissues caused by Newcastle disease virus genotype VIId

Some strains of Newcastle disease virus (NDV) genotype VIId cause more-severe tissue damage in lymphoid organs compared to other virulent strains. In this study, we aim to define the mechanism of this distinct pathological manifestation of genotype VII viruses. Pathology, virus replication, and the innate immune response in lymphoid tissues of chickens infected with two genotype VIId NDV strains (JS5/05 and JS3/05), genotype IX NDV F48E8 and genotype IV NDV Herts/33, were compared. Histopathologic examination showed that JS5/05 and JS3/05 produced more-severe lesions in the spleen and thymus, but these four virulent strains caused comparable mild lesions in the bursa. In addition, JS3/05 and JS5/05 replicated at significantly higher levels in the lymphatic organs than F48E8 and Herts/33. A microarray assay performed on the spleens of chickens infected with JS5/05 or Herts/33 revealed that JS5/05 elicited a more potent inflammatory response by increasing the number and expression levels of activated genes. Moreover, cytokine gene expression profiling showed that JS5/05 and JS3/05 induced a stronger cytokine response in lymphoid tissues compared to F48E8 and Herts/33. Taken together, our results indicate that the severe pathology in immune organs caused by genotype VIId NDV strains is associated with high levels of virus replication and an intense inflammatory response.

Molecular characterization of chicken-derived genotype VIId Newcastle disease virus isolates in China during 2005-2012 reveals a new length in hemagglutinin-neuraminidase

Newcastle disease (ND) is one of the most important diseases of poultry, and causes severe economic losses in the global poultry industry. Although all Newcastle disease virus (NDV) isolates belong to a single serotype, significant genetic diversity has been described between different NDV isolates. Here, we report the molecular characterization of 23 virulent genotype VIId NDV isolates of class II circulating in China. Phylogenetic construction and analysis revealed the existence of distinctly genomic and amino acid differences that clearly distinguished these isolates from other typical NDV genotypes and vaccine strains. We also report a new 582-amino-acid hemagglutinin-neuraminidase in genotype VII NDV strains. This is believed to be the first study to investigate systematically the most predominant NDV strains, and provides more information on the genetic nature of genotype VIId NDV of class II circulating in China.