Pathotypical characterization and molecular epidemiology of Newcastle disease virus isolates from different hosts in China from 1996 to 2005

Genetic Characterization, Pathogenicity, and Epidemiology Analysis of Three Sub-Genotype Pigeon Newcastle Disease Virus Strains in China

Pigeon Newcastle disease (ND) is a serious infectious illness caused by the pigeon Newcastle disease virus (NDV) or Paramyxovirus type 1 (PPMV-1). Genotype VI NDV is a primary factor in ND among Columbiformes (such as pigeons and doves). In a recent study, eight pigeon NDV strains were discovered in various provinces in China. These viruses exhibited mesogenic characteristics based on their MDT and ICPI values. The complete genome sequences of these eight strains showed a 90.40% to 99.19% identity match with reference strains of genotype VI, and a 77.86% to 80.45% identity match with the genotype II vaccine strain. Additionally, analysis of the F gene sequence revealed that these NDV strains were closely associated with sub-genotypes VI.2.2.2, VI.2.1.1.2.1, and VI.2.1.1.2.2. The amino acid sequence at the cleavage site of the F protein indicated virulent characteristics, with the sequences 112KRQKRF117 and 112RRQKRF117 observed. Pigeons infected with these sub-genotype strains had a low survival rate of only 20% to 30%, along with lesions in multiple tissues, highlighting the strong spread and high pathogenicity of these pigeon NDV strains. Molecular epidemiology data from the GenBank database revealed that sub-genotype VI.2.1.1.2.2 strains have been prevalent since 2011. In summary, the findings demonstrate that the prevalence of genotype VI NDV is due to strains from diverse sub-genotypes, with the sub-genotype VI.2.1.1.2.2 strain emerging as the current epidemic strain, highlighting the significance of monitoring pigeon NDV in China.

Detection of Avian Orthoavulavirus-1 genotypes VI.2.1 and VII.1.1 with neuro-viscerotropic tropism in some backyard pigeons (Columbidae) in Eastern Saudi Arabia

Introduction

Avian orthoavulavirus-1 (AOAV1) has a wide host range, including domestic and wild birds. The present study aimed to identify the currently circulating AOAV1 strains from some outbreaks in some backyard pigeons in the eastern region of Saudi Arabia (ERSA).

Methods

Tracheal/cloacal swabs and tissue specimens were collected from eight backyards in Al-Ahsa, ERSA, between January 2021 and March 2023. Samples were tested for the presence of AOAV1 using commercial real-time RT-PCR. Part of the fusion gene was also amplified by gel-based RT-PCR, and the obtained amplicons were sequenced.

Results and discussion

AOAV1 was detected in samples from the eight flocks. The retrieved sequences from samples of 6/8 pigeon backyards are reported. Phylogenetic analysis based on the obtained sequences from these backyard pigeons showed the segregation of the obtained sequences in AOAV1 genotypes VI.2.1 and VII.1.1. Clinically, nervous manifestations were dominant in pigeons infected with both genotypes. Respiratory manifestations and significantly higher overall mortality rate were induced by genotype VI.2.1. The deduced amino acid sequences of the fusion protein cleavage site (FPCS) showed that all the detected isolates belong to velogenic strains. Differences in clinical profiles induced by the natural infection of pigeons with AOAV1 genotypes VI.2.1 and VII.1.1 were reported. The present findings highlight the potential roles of some backyard pigeons in the long-distance spread and cross-species transmission of the reported AOAVI genotypes. Further research is required to perform biotyping and pathotyping of the reported strains.

Comparative protective efficacy of a newly generated live recombinant thermostable highly attenuated vaccine rK148/GVII-F using a single regimen against lethal NDV GVII.1.1

RESEARCH HIGHLIGHTS

A thermostable, safe, and effective NDV GVII recombinant vaccine was generated.Fusion gene replacement with GVII did not affect GI K148/08 virus thermostability.Strain rK148/GVII-F provided adequate protection against a lethal NDV challenge.Oropharyngeal shedding was significantly reduced on post-challenge days 5 and 7.

Molecular characterization of a novel variant of infectious bronchitis virus from field outbreaks in backyard chicken population of North East India

Infectious bronchitis virus (IBV) causes considerable economic impacts on global poultry production. Since its emergence in early 1930, IBV continues to evolve and now exists in a wide range of antigenically and genetically distinct variants, that makes the prevention and the control of the disease both complex and challenging. Although IBV has been reported regularly from different corner of India, information about the molecular epidemiology of circulating strain in relation to clinical form of the disease is not available. We have studied the clinico-pathology and confirmed eight distinct field outbreaks of the disease from poultry population of Mizoram, India. The clinical disease in affected birds resulted sever pathological lesions involving respiratory, gastrointestinal, and urinary system together. The complete S1 nucleotide sequences and protein analyses have revealed a distinct variant of genotype I-IBV (GI), designated as GI-24 circulating in India. The S1 protein of the field strains displayed unique additional eighteen amino acids at C terminal end when compared with M41strain. Comparison of the S1 protein among all the 27 lineages of GI revealed five mutations that are exclusive to only the Indian strains. All the field strains have also possessed the amino acid mutations at highly variable region 2 (HVR2) of S1 receptor-binding domain (RBD) that are considered characteristic of nephropathogenic strains. The circulating GI-24 strains displayed potency for a wide range of tropism from respiratory epithelium to GIT and urinary system. This study provides insight on recently emerging IBV outbreaks in NER, India, which might be causing huge economic losses to the poultry farmers in the region.

Evaluating the effect of Spirulina platensis on the immune response of broiler chickens to various vaccines and virulent Newcastle disease virus challenge

This study investigated the efficacy of co-administration of Spirulina platensis (SP) with vaccines on the immune response to Avian influenza (AI), Infectious bronchitis (IB), and Newcastle disease (ND), along with I/M challenging by virulent ND virus (vNDV) genotype VII. 126 one-day-old broiler chicks were allocated into six groups (21 birds/group with three replicates): G1: negative control; G2: positive control; G3: vaccinated, non-SP-supplemented; G4: vaccinated, SP-supplemented (0.1%); G5: vaccinated, SP-supplemented (0.3%); and G6: vaccinated, SP-supplemented (0.5%). G2-6 were challenged with a velogenic NDV genotype VII virus. Dietary SP administration prevented the ND-induced mortality compared to G2 (52.4%) and G3 (14.3%), in addition to alleviating the clinical disease. G3-6 showed significant improvement in body weight loss% and FCR during two weeks post vNDV challenge (pc), and the overall FCR (2.64 ± 0.28, 1.56 ± 0.03, 1.60 ± 0.05, 1.53 ± 0.04, and 1.54 ± 0.03 for G2, 3, 4, 5 and 6, respectively) (P<0.05). On the challenging day, the ND-HI titer (log2) of G3 (5.44 ± 0.24) was numerically higher than G6 (4.20 ± 0.55) and lower than G4 (6.10 ± 0.34) and G5 (6.00 ± 0.28). On the 10th day pc, ND-HI titer in G4-6 was numerically lower in a dose-dependent manner than that of G3, suggesting an antiviral efficacy of SP. G4-6 had lower viral shedding titer than G2 and G3 (P<0.05). In G3-6, viral shedding was reduced by 15, 27, 24, and 33.6%, respectively. In addition, the histopathological lesions in the trachea, lung, and spleen were severe in G2, moderately reduced in G3, and more relieved in G4-6. At three weeks after vaccination, the HI antibody titer of AIH5 was significantly higher after SP administration, especially at the 0.3% level, compared to the vaccine alone (P<0.05), demonstrating an immune-stimulating effect. In conclusion, dietary administration of SP, particularly a dose of 0.3%, for vaccinated chickens against NDV exerted an antiinflammatory and antiviral effects by preventing deaths, alleviating clinical disease and weight loss, and decreasing viral shedding post heterologous NDV challenge.

Detection and molecular characterization of virulent Newcastle disease virus (subgenotype VII.2) in broiler chickens in Northern Vietnam

Background and Aim

Newcastle disease (ND) is a major viral disease of poultry worldwide. However, data on the molecular characterization of Newcastle disease virus (NDV) in Vietnam are limited. This study aimed to identify the molecular characteristics of NDV strains from the vaccinated chickens farmed in Northern Vietnam.

Materials and Methods

We used reverse-transcription polymerase chain reaction (PCR), sequencing and phylogenetic analysis to characterize NDV strains from vaccinated chicken farms in Northern Vietnam.

Results

Seven out of 72 (9.7%) chicken tissue samples collected from seven chicken farms in the four cities/provinces in northern Vietnam were positive for the NDV genome by PCR method. The complete sequences of the fusion (F) and hemagglutinin-neuraminidase (HN) genes of NDVs isolated in the North of Vietnam from 2021 to 2022 were further evaluated. The results indicated that all seven Vietnamese isolates obtained were reported as virulent NDV strains with the amino acid (AA) sequence of the F0 protein proteolytic cleavage site motif (112RRRKRF117). Phylogenetic analysis revealed that they were grouped with other NDV class II from subgenotype VII.2, including the two previous Vietnamese NDV (2015), the Chinese (2017), and Southern African (2013) NDV strains. In addition, some AA substitutions were observed in the neutralizing epitopes of the F and HN proteins of the current Vietnamese NDV strains.

Conclusion

The present findings provide useful information for future studies of the evolution of NDVs and improve strategies for ND-controlling programs in Vietnam.

Emergence of a novel genotype of class II New Castle Disease virus in North Eastern States of India

Outbreaks of New Castle Disease from three north eastern states of India were confirmed by clinico-pathological examination followed by reverse transcription-PCR detection of F gene of ND Virus (NDV). Irrespective of vaccination, the outbreaks resulted 90-100% mortality in the affected flocks. The analysis of fusion protein sequences from ten field isolates revealed them as the velogenic or highly virulent strain. Phylogenetic analyses based on the complete F gene nucleotide sequences of the isolates have characterized only one of the isolate (OK149201) in the genotype XIII.2.2. The rest of the nine isolates are depicted in a distinct monophyletic group with average nucleotide distances from the other 20 genotypes ranged from 10.90 - 20.70. The nine isolates were further divided into two sub branches with the bootstrap support value of 100% at the nodes that define the two subgroups with an average evolutionary nucleotide distance of 6.00between the isolates in the two subgroups. As per the recommendation put forth in recently updated unified phylogenetic classification system for NDV, our findings clearly indicates emergence of a novel genotype of class II NDV in the biodiversity hot spot region of NER, India. The isolates in the newly identified genotype is designated with next available Roman numerals XXII. Further, the two subgroups within the genotype are designated as XXII.1 and XXII.2.

Phylogeny and Pathogenicity of Subtype XIIb NDVs from Francolins in Southwestern China and Effective Protection by an Inactivated Vaccine

Most genotype XII newcastle disease viruses (NDVs) were isolated from poultry, chickens, or geese, with the exception of one subtype, XIIa NDV, which was isolated from a peacock. Here, two subtype XIIb NDVs, francolin/China/GX01/2017 and francolin/China/GX02/2017 (GX01 and GX02 hereafter), were isolated from francolins, which are resident birds in southern China. GX01 and GX02 were characterized as velogenic NDVs. Based on the weaker pathogenicity of these viruses in chickens, the amino acid sequences of seven proteins from genotype XII NDVs were compared, which revealed 17, 40, 15, 7, 32, 25, and 31 variations in the NP, P, M, F, HN, L, and V proteins, respectively, some of which could be responsible for this decreased pathogenicity. Epidemiological and phylogenetic analyses suggest that subtype XIIb NDVs have multiple transmission chains, and that resident birds may be involved in this process as intermediate hosts in which viruses keep evolving. Because of the increased pathogenicity of subtype XIIb NDVs, the protective efficacy of GX01 as an inactivated vaccine was evaluated and compared with that of two commercial inactivated vaccines in chickens. The results showed that the subtype XIIb NDVs could be candidate genotype-matched vaccine strains against genotype XII NDVs.

Efficacy of Newcastle disease LaSota vaccine-induced hemagglutination inhibition antibodies against challenges with heterologous virulent strains of genotypes VII and IX

Newcastle disease (ND), caused by virulent Newcastle disease virus (NDV), still remains one of the most important avian diseases affecting the poultry industry worldwide, despite intensive vaccination programs have been implemented in many countries. All NDV isolates characterized to date are of one serotype and classified into classes I and II, with class II being further divided into twenty-one genotypes. Antigenic and genetic diversity is observed among the different genotypes. Current commercially available vaccines belonging to genotypes I and II are genetically divergent from strains that caused ND outbreaks worldwide in the last two decades. Reports of vaccination failures on their insufficient ability to inhibit infection or virus shedding have created renewed interest in developing vaccines homologous to virulent NDV circulating in the field. In this study, after vaccination with the most widely used LaSota vaccine (genotype II), chickens with different hemagglutination inhibition (HI) antibody levels were challenged with heterologous virulent NDV strains of genotypes VII and IX to evaluate how antibody levels relate to clinical protection and infection or virus shedding. Under the experimental condition, LaSota vaccine could fully protect birds from morbidity and mortality, but higher antibody levels were required to inhibit virus shedding. The number of birds shedding virus generally tended to decrease as the HI antibody titers increase in vaccinated birds. When the HI antibody titers reached ≥ 13 log₂ and ≥ 10 log₂, the virus shedding from JSC0804 strain (genotype VII) and F48E8 strain (genotype IX) could be completely inhibited, respectively, but it may be difficult to ensure that all individuals reach and maintain those levels in chicken flocks vaccinated according to routine procedure. Furthermore, the virus shedding in vaccinated birds was correlated with the amino acid similarity between the vaccine and challenge strains; more similarity, less virus shedding. The results obtained highlight that stringent biosecurity measures combined with vaccination are crucial for chicken farms to maintain a virulent NDV-free status.

Game Birds Can Act as Intermediaries of Virulent Genotype VII Avian Orthoavulavirus-1 between Wild Birds and Domestic Poultry

Newcastle Disease (ND), caused by virulent forms of Avian orthoavulavirus serotype-1 (AOAV-1) is an economically important avian disease worldwide. The past two incursions of ND into the United Kingdom occurred in game bird populations during 2005 and 2006. The nature of the game bird semi-feral rearing system, which can bring these birds into close contact with both wild birds and commercial or backyard poultry, has been hypothesized to act as a bridge between these two environments. As such, the risk that AOAV-1-infected game birds may pose to the UK poultry industry was investigated. Pheasants, partridges and chickens were experimentally infected with the virulent strain APMV-1/Chicken/Bulgaria/112/13, a genotype VII.2 virus associated with ND outbreaks in Eastern Europe. The study demonstrated that both chickens and pheasants are susceptible to infection with APMV-1/Chicken/Bulgaria/112/13, which results in high mortality and onward transmission. Partridges by contrast are susceptible to infection, but mortality was reduced, as was onward transmission. However, the data indicated that both pheasants and partridges may serve as intermediate hosts of AOAV-1 and may bridge the wild bird-domestic poultry interface enabling transmission into an economically damaging environment where morbidity and mortality may be high.

Multiple potential recombination events among Newcastle disease virus genomes in China between 1946 and 2020

Introduction

Newcastle Disease Virus (NDV) is a highly adaptable virus with large genetic diversity that has been widely studied for its oncolytic activities and potential as a vector vaccine. This study investigated the molecular characteristics of 517 complete NDV strains collected from 26 provinces across China between 1946-2020.

Methods

Herein, phylogenetic, phylogeographic network, recombination, and amino acid variability analyses were performed to reveal the evolutionary characteristics of NDV in China.

Results and discussions

Phylogenetic analysis revealed the existence of two major groups: GI, which comprises a single genotype Ib, and GII group encompassing eight genotypes (I, II, III, VI. VII. VIII, IX and XII). The Ib genotype is found to dominate China (34%), particularly South and East China, followed by VII (24%) and VI (22%). NDV strains from the two identified groups exhibited great dissimilarities at the nucleotide level of phosphoprotein (P), matrix protein (M), fusion protein (F), and haemagglutinin-neuraminidase (HN) genes. Consistently, the phylogeographic network analysis revealed two main Network Clusters linked to a possible ancestral node from Hunan (strain MH289846.1). Importantly, we identified 34 potential recombination events that involved mostly strains from VII and Ib genotypes. A recombinant of genotype XII isolated in 2019 seems to emerge newly in Southern China. Further, the vaccine strains are found to be highly involved in potential recombination. Therefore, since the influence of recombination on NDV virulence cannot be predicted, this report's findings need to be considered for the security of NDV oncolytic application and the safety of NDV live attenuated vaccines.

Current situation and future direction of Newcastle disease vaccines

Newcastle disease (ND) is one of the most economically devastating infectious diseases affecting the poultry industry. Virulent Newcastle disease virus (NDV) can cause high mortality and severe tissue lesions in the respiratory, gastrointestinal, neurological, reproductive and immune systems of poultry. Tremendous progress has been made in preventing morbidity and mortality caused by ND based on strict biosecurity and wide vaccine application. In recent decades, the continual evolution of NDV has resulted in a total of twenty genotypes, and genetic variation may be associated with disease outbreaks in vaccinated chickens. In some countries, the administration of genotype-matched novel vaccines in poultry successfully suppresses the circulation of virulent NDV strains in the field. However, virulent NDV is still endemic in many regions of the world, especially in low- and middle-income countries, impacting the livelihood of millions of people dependent on poultry for food. In ND-endemic countries, although vaccination is implemented for disease control, the lack of genotype-matched vaccines that can reduce virus infection and transmission as well as the inadequate administration of vaccines in the field undermines the effectiveness of vaccination. Dissection of the profiles of existing ND vaccines is fundamental for establishing proper vaccination regimes and developing next-generation vaccines. Therefore, in this article, we provide a broad review of commercial and experimental ND vaccines and promising new platforms for the development of next-generation vaccines.

Newcastle Disease Genotype VII Prevalence in Poultry and Wild Birds in Egypt

Newcastle Disease Virus (NDV) genotype VII is a highly pathogenic Orthoavulavirus that has caused multiple outbreaks among poultry in Egypt since 2011. This study aimed to observe the prevalence and genetic diversity of NDV prevailing in domestic and wild birds in Egyptian governorates. A total of 37 oropharyngeal swabs from wild birds and 101 swabs from domestic bird flocks including chickens, ducks, turkeys, and pelicans, were collected from different geographic regions within 13 governorates during 2019–2020. Virus isolation and propagation via embryonated eggs revealed 91 swab samples produced allantoic fluid containing haemagglutination activity, suggestive of virus presence. The use of RT-PCR targeted to the F gene successfully detected NDV in 85 samples. The geographical prevalence of NDV was isolated in 12 governorates in domestic birds, migratory, and non-migratory wild birds. Following whole genome sequencing, we assembled six NDV genome sequences (70–99% of genome coverage), including five full F gene sequences. All NDV strains carried high virulence, with phylogenetic analysis revealing that the strains belonged to class II within genotype VII.1.1. The genetically similar yet geographically distinct virulent NDV isolates in poultry and a wild bird may allude to an external role contributing to the dissemination of NDV in poultry populations across Egypt. One such contribution may be the migratory behaviour of wild birds; however further investigation must be implemented to support the findings of this study. Additionally, continued genomic surveillance in both wild birds and poultry would be necessary for monitoring NDV dissemination and genetic diversification across Egypt, with the aim of controlling the disease and protecting poultry production.

Epidemiology of Newcastle disease in chickens of Ethiopia: a systematic review and meta-analysis

The objective of this systematic review was to estimate the overall pooled prevalence of Newcastle disease in chickens in Ethiopia and identify the sources of heterogeneity among and within studies. The seroprevalence of Newcastle disease was estimated using a single-group meta-analysis. Attempts were also made to identify study-level variables that could explain the heterogeneity in the apparent seroprevalence of the Newcastle disease. The findings were based on 16 published articles and 33 district-level reports and were limited to studies performed during 2005-2017. Due to the presence of heterogeneity, pooled analysis from different districts was conducted using random-effects meta-analysis. The single-group summary of Newcastle disease seroprevalence in chickens was estimated to be 21.47% (19.54-23.4%) with a 95% confidence interval. Our results indicated high inter-study variability (Cochran's Q statistic = 196.2, true variance (τ²) = 0.36, inverse variance index (I²) = 90.0%, p < 0.001). Of all variables analysed, diagnostic techniques and regions were the most significant predictors (p ˂ 0.05) of heterogeneity. According to the diagnostic technique-based meta-analysis of random pooled prevalence, the haemagglutination inhibition test had the highest prevalence, followed by the enzyme-linked immunosorbent assay. In conclusion, the high-pooled prevalence estimates of the disease, combined with the scarcity of published data for the entire country of Ethiopia, indicate a significant data gap on the distribution of Newcastle disease in the country. While the high pooled prevalence tells the need for intervention to control the disease, there is also a need to assess the disease prevalence in all other parts of the country.

Screening and identification of nucleocapsid protein-nanobodies that inhibited Newcastle disease virus replication in DF-1 cells

Newcastle disease (ND) is an acute and highly contagious infectious disease found in poultry. Although commercial ND virus (NDV) vaccines are universally used, some case reports persistently documented vaccination failure. Therefore, novel strategies are still required to control the occurrence of the disease in chickens. Recently, nanobodies (Nbs), which have the advantages of small molecular weight and low production costs, have been shown to be promising therapeutics against viral infection. In the present study, a total of 16 Nbs against NDV nucleocapsid protein (NP) were screened from two libraries against NDV using phage display technology. Of the 16 screened Nbs, eight were prevented from binding to NDV NP protein through administering positive chicken sera for anti-NDV antibodies, indicating that the epitopes recognized by these eight Nbs were able to induce the immune response after the chickens were infected with NDV stock. Subsequently, transfection assay, construction of recombinant DF-1 cells capable of expressing different nanobodies and viral inhibition assay were used to screen the nanobodies inhibiting NDV replication. The results demonstrated that Nb18, Nb30, and Nb88 significantly inhibited the replication of Class I and different genotypes of Class II NDV strains in DF-1 cells when they were expressed in the cytoplasm. Collectively, these nanobodies provided new tools for researching the functions of NDV NP protein and may be used as a novel strategy for designing drugs against NDV infection in chickens.

Isolation, Identification, and Molecular Characterization of Newcastle Disease Virus from Field Outbreaks in Chickens in Afghanistan

Newcastle disease viruses (NDVs) in Afghanistan were isolated from three chicken farms and identified using a hemagglutination test and reverse transcription-polymerase chain reaction assay. Three isolates from each farm were sequenced to characterize the part of their fusion protein gene around the cleavage site. The characteristics of the fusion protein genes of the three isolates shown by phylogenic analysis indicated that the isolates were velogenic, belonged to the class II subgenotype VII 1.1, and were closely related to an identified Chinese NDV isolate. To our knowledge, this is the first time that NDV isolates from Afghanistan have been partially sequenced.

Genetic characterization and distribution of the virus in chicken embryo tissues infected with Newcastle disease virus isolated from commercial and native chickens in Indonesia

Background and Aim:

Newcastle disease (ND) is a viral infectious disease that affects commercial and native chickens, resulting in economic losses to the poultry industry. This study aimed to examine the viral strains circulating in commercial and native chickens by genetic characterization and observe the distribution of Newcastle disease virus (NDV) in chicken embryonic tissue.

Materials and Methods:

ND was detected using a quantitative reverse transcription-polymerase chain reaction. Genetic characterization of the fusion (F) and hemagglutinin-neuraminidase (HN) genes from the eight NDVs was performed using specific primers. The sequence was compared with that of other NDVs from GenBank and analyzed using the MEGA-X software. The distribution of NDV in chicken embryos was analyzed based on lesions and the immunopositivity in immunohistochemistry staining.

Results:

Based on F gene characterization, velogenic NDV strains circulating in commercial and native chickens that showed varying clinical symptoms belonged to genotype VII.2. Lentogenic strains found in chickens without clinical symptoms were grouped into genotype II (unvaccinated native chickens) and genotype I (vaccinated commercial chickens). Amino acid variations in the HN gene, namely, the neutralization epitope and antigenic sites at positions 263 and 494, respectively, occurred in lentogenic strains. The NDV reaches the digestive and respiratory organs, but in lentogenic NDV does not cause significant damage, and hence embryo death does not occur.

Conclusion:

This study showed that velogenic and lentogenic NDV strains circulated in both commercial and native chickens with varying genotypes. The virus was distributed in almost all organs, especially digestive and respiratory. Organ damage in lentogenic infection is not as severe as in velogenic NDV. Further research is needed to observe the distribution of NDV with varying pathogenicity in chickens.

Alteration in the Population of Intraepithelial Lymphocytes and Virus Shedding in Specific-Pathogen-Free Chickens Following Inoculation with Lentogenic and Velogenic Newcastle Disease Virus Strains

Intraepithelial lymphocytes (IELs) provide the first line of immunological defense after the invasion of the intestine by a pathogen. To understand the changes of IEL response in chickens, we measured the population of different subsets of avian IELs at different time points after primary inoculation of Newcastle disease virus (NDV) lentogenic strain (LaSota) and subsequent challenge with NDV velogenic strain- genotypes VII and VIII. Furthermore, NDV shed after each treatment was quantified. Specific-pathogen-free chickens were randomly divided into six groups of chickens, one to six, inoculated with phosphate buffered saline; NDV lentogenic strain (LaSota); genotype VII (GVII); LaSota and challenged with GVII (LSGVII); genotype VIII (GVIII); and group of LaSota and challenged with GVIII (LSGVIII). The chickens were euthanized at 12, 36, and 60 h postchallenge. Immunophenotyping of CD25⁺ IEL, CD3⁺ cells, CD4⁺ cells, and CD8⁺ cells was conducted using flow cytometer. Furthermore, virus shedding was measured using reverse transcriptase-quantitative polymerase chain reaction. Data were analyzed using a two-way analysis of variance (ANOVA). The results showed that the percentage population of IEL subsets was generally lower in the chickens inoculated with GVII or GVIII when compared with LaSota, LSGVII and LSGVIII inoculated groups. The NDV copy number was significantly higher in chickens challenged with NDV GVII or GVIII when compared with chickens inoculated with LaSota, LSGVII or LSGVIII. Taking together, NDV velogenic strain caused decrease in the population of subsets of chickens' IEL. However, inoculation of NDV LaSota may increase the population of avian IEL subsets and decrease shedding of virulent NDV.

Effective improvements to the live-attenuated Newcastle disease virus vaccine by polyethylenimine-based biomimetic silicification

Live and killed vaccines impart a significant role in preventing of Newcastle disease (ND) in China. Vaccine efficacy could be ameliorated by improving vaccine-induced cellular immunity and antibody persistency. Previous studies substantiated the potency of silicon dioxide (SiO₂) in the control-release of drugs and as a vaccine adjuvant, and polyethylenimine (PEI) merits as a mucosal adjuvanticity with electro-positivity. The present study employed SiO₂ and PEI to prepare biomimetic silicon mineralized nanoparticle G7M@SiO₂-PEI and microparticle (SiO₂ + PEI)@G7M vaccines of G7M, a candidate for live attenuated vaccine of genotype VII Newcastle disease virus (NDV). The zeta potential experiment confirmed the significant increase in the average zeta potential of the nanoparticle G7M@SiO₂-PEI and microparticle (SiO₂ + PEI)@G7M relative to G7M before mineralization. The results of RT-qPCR revealed more than 99% mineralization efficiency of the G7M@SiO₂-PEI and (SiO₂ + PEI)@G7M. The morphology detected by transmission electron microscopy reported that the diameters of G7M@SiO₂-PEI were similar to those of G7M, while for (SiO₂ + PEI)@G7M, it was about five times larger than that of G7M. Silicon was detected on the surface of both mineralization particles, except for G7M, as observed from the elemental distribution detected by elemental mapping and energy dispersive X-ray spectrogram. Indirect immunofluorescence assays validated that mineralization virus have replicated ability in BHK-21F cells. In vivo experiments revealed higher than 5.50 log₂ of antibody in nanoparticles G7M@SiO₂-PEI group until 10-week post-vaccination, and significant proliferation of antigen-specific CD3⁺CD4⁺ in nanoparticles G7M@SiO₂-PEI immunized group corroborated improved cellular immune responses. Vaccines provided full protection to the immunized chickens, whereas all the chickens receiving mock immunizations succumbed to the disease. Overall, our study concluded the efficacy of biomimetic mineralization of live attenuated vaccine in nanoparticles to improve humoral and cellular immune responses.

Protection of chicks from Newcastle disease by combined vaccination with a plasmid DNA and the pre-fusion protein of the virulent genotype VII of Newcastle disease virus

In this study, four codon optimized plasmids (designated as pCAG-optiF-1, 2, -3, and -4) containing modified F genes from the epidemic and virulent NDV genotype VII strain isolated in China that is expected to express the pre-fusion conformation of the F protein were constructed. The expression of these F variants in chicken-derived cells was detected by an indirect immunofluorescence assay and western blot analysis. Two soluble F variants (roptiF-1 and 2) potentially with the pre-fusion conformation were expressed and purified from suspended cells. Vaccination with each of the plasmids as a DNA vaccine conferred partial clinical protection to chicks against NDV. Comparatively, the plasmid pCAG-optiF-2 encoded a soluble protein with a mutant cleavage site and the potential pre-fusion conformation provided better protection than the other plasmids. Further investigation of the combined vaccinations with the plasmid DNA pCAG-optiF-2 prime + protein roptiF-2 boost vaccination strategy elicited more robust immunity, as confirmed by the detection of antibodies against NDV using enzyme-linked immunosorbent assay and virus neutralization assay, as compared to those vaccinated with only the plasmid pCAG-optiF-2 or protein roptiF-2. More importantly, the DNA prime + protein boost vaccination provided more efficacious protection against virulent NDV challenge, as evidenced by the complete clinical protection, reduced viral shedding, and limited virus replication in tissues of the challenge chicks. These results indicated that the pre-fusion conformation of the F protein could be considered as the target immunogen for the development of novel NDV vaccines.

Molecular characterization of full genome sequences of Newcastle disease viruses circulating among vaccinated chickens in Egypt during 2011-2013

Although intensive vaccination programs have been implemented, Newcastle disease (ND) outbreaks, accompanied by severe economic losses, are still reported in Egypt. The genetic characterization of ND virus (NDV) strains isolated from ND-vaccinated chicken flocks provides essential information for improving ND control strategies. Therefore, here, 38 NDV strains were isolated and identified from outbreaks among vaccinated flocks of broiler chickens located in the provinces of Qena, Luxor, and Aswan of Upper Egypt during 2011–2013. The investigated broiler chicken flocks (aged 28 to 40 days) had high mortality rates of up to 80%. All NDV isolates were genetically analyzed using next-generation DNA sequencing. From these isolates, 10 representative NDV strains were selected for further genetic analyses. Phylogenetic analysis of full-length coding genes revealed that the Egyptian NDV isolates belonged to a single sub-genotype, VII.1.1. These isolates were phylogenetically distant from the vaccine strains, including La Sota or Clone 30 (genotype II), which have been commonly used to vaccinate chicken flocks. Amino acid substitution K78R was observed in the neutralizing epitopes of the F proteins; whereas several mutations were found in the neutralizing epitopes of the hemagglutinin-neuraminidase proteins, notably, E347K. Overall, our results suggested that the occurrence of neutralizing epitope variants may be one of potential reasons for ND outbreaks. Further studies are needed to determine the protective effect of current vaccines against circulating virulent NDV strains.

Clinical, molecular and cytopathological characterization of a Newcastle disease virus from an outbreak in Baghdad, Iraq

BACKGROUND

The frequent outbreaks of Newcastle disease virus (NDV) in Iraq pose a constant threat to commercial poultry, despite the introduction of routine vaccination programmes. Several factors, particularly stress factors and coinfections, might play a role in increasing NDV outbreaks in poultry species.

OBJECTIVES

The current study was aimed to characterize an NDV isolate from an outbreak in North Baghdad, Iraq.

METHODS

Clinical pathogenicity of the isolate was determined experimentally in chickens. In vitro studies included cytopathological examination, as well as molecular and phylogenetic analyses.

RESULTS

Based on the clinical studies and pathogenicity indices (mean death time and intracerebral and intravenous pathogenicity indices), the isolate was characterized as velogenic (highly virulent). Reverse transcriptase polymerase chain reaction targeting the partial fusion protein gene of the NDV genome confirmed the detection. Partial sequencing of the hypervariable region of the fusion gene identified the presence of an avirulent (lentogenic) fusion protein motif (GRQGRL). Phylogenetic analysis of the new isolate along with previously known regional isolates revealed that the new isolate was related to genotype II strains. Additionally, sequence analysis indicated a distinct genetic lineage of the new isolate, which was related to some of the lineages identified in previous outbreaks in the Middle East.

CONCLUSION

The current study offers essential information on the epidemiology, characteristics and diagnosis of NDV for disease control in Iraq. The isolate was found to belong to genotype II and possess an avirulent fusion protein motif.

Protective efficacy of the Newcastle disease virus genotype VII-matched vaccine in commercial layers

Newcastle disease virus (NDV) is a major threat to the poultry industry worldwide, with a diversity of genotypes associated with severe economic losses in all poultry sectors. Class II genotype VII NDV are predominant in the Middle East and Asia, despite intensive vaccination programs using conventional live and inactivated NDV vaccines. In Egypt, the disease is continuously spreading, causing severe economical losses in the poultry industry. In this study; the protective efficacy of a commercial, inactivated recombinant genotype VII NDV–matched vaccine (KBNP-C4152R2L strain) against challenge with the velogenic NDV strain (Chicken/USC/Egypt/2015) was evaluated in commercial layers. Two vaccination regimes were used; live NDV genotype II (LaSota) vaccine on days 10, 18, and 120, with either the inactivated NDV genotype II regime or inactivated NDV genotype VII–matched vaccine regime on days 14, 42, and 120. The 2 regimes were challenged at the peak of egg production on week 26. Protection by the 2 regimes was evaluated after experimental infection, based on mortality rate, clinical signs, gross lesions, virus shedding, seroconversion, and egg production schedule. The results show that these 2 vaccination regimes protected commercial layer chickens against mortality, but some birds showed mild clinical signs and reduced egg production temporarily. However, the combination of live NDV genotype II and recombinant inactivated genotype VII vaccines provided better protection against virus shedding (20% and 0% vs. 60% and 40%) as assessed in tracheal swabs and (20% and 0% vs. 20% and 20%) in cloacal swabs collected at 3 and 5 D post challenge (dpc), respectively. In addition, egg production levels in birds receiving the inactivated NDV genotype VII–matched vaccine regime and in those given inactivated genotype II vaccines were 76.6, 79, 82, and 87.4% and 77.7, 72.5, 69, and 82.5% at 7, 14, 21, and 28 dpc, respectively. The results of this study indicate that recombinant genotype-matched inactivated vaccine along with a live attenuated vaccine can reduce virus shedding and improve egg production in commercial layers challenged with a velogenic genotype VII virus under field conditions. This regime may ensure a proper control strategy in layers.

Genetic Characterization of Infectious Bursal Disease Viruses from Field Outbreaks of the North East Region of India

In recent years, acute severe outbreaks of infectious bursal disease (IBD) are frequently observed in commercial chicken populations of the North East Region (NER) of India, resulting in huge economic loses to poultry farmers. Field outbreaks of IBD in 30 different poultry farms in the NER were confirmed by clinicopathologic examination and reverse transcriptase PCR. A total of 10 isolates of IBD virus (IBDV) from these outbreaks were characterized by the genetic analysis of VP1 and the hypervariable region of the VP2 gene. Nucleotide sequences, deduced amino acid sequences, and phylogenetic analysis of both VP2 and VP1 genes revealed two genetically diverse strains of very virulent IBDV (vvIBDV) and one intermediate strain circulating in the NER. These isolates differ at nucleotide and amino acid levels from vvIBDV isolates of mainland India and are clustered in distinctly separate groups in the phylogenetic tree. Six of the isolates revealed a unique combination of vvIBDV amino acid signatures in the VP2 gene (A222, I256, I294), while bearing the non-vvIBDV amino acid signatures of the VP1 gene (146E, 147G, 242D), but they are clearly classified as vvIBDV in a phylogenetic analysis of both genes. Interestingly, one of the isolates showed 99% sequence homology with attenuated vaccine strains in the VP2 gene and clustered together. This study demonstrates the diversity of IBDVs in India and document for the first time the possible involvement of attenuated vaccine strains in the epidemiology of IBD in India.

Phylogeny, pathogenicity and transmissibility of a genotype XII Newcastle disease virus in chicken and goose

Although Newcastle disease virus (NDV) has a worldwide distribution, some NDV genotypes have more regional geographical ranges within continents. In this study, we isolated a subgenotype XIIb NDV strain, Goose/CH/GD/E115/2017 (E115), from geese in Guangdong province, Southern China, in 2017. Phylogenetic analysis showed that E115 and six other NDVs from geese in China were grouped under subgenotype XIIb and were distinct from subgenotype XIIa, isolated from chickens in South Africa, and subgenotype XIId, isolated from chickens in Vietnam. To better understand the pathogenicity and transmission of the subgenotype XIIb NDVs from geese in Guangdong province, we inoculated chickens and geese with 10⁶ EID₅₀ of the E115 virus. Eight hours after inoculation, three naïve chickens and three naïve geese were co-housed with the infected chickens or geese to assess intraspecific and interspecific horizontal transmission of the E115 virus. The E115 virus induced significant clinical signs without mortality in chickens, while it was not pathogenic to geese. Intraspecific and interspecific horizontal transmission of the E115 virus was observed among chickens and geese via direct contact. Furthermore, although the current vaccines provided complete protection against disease in chickens after challenging them with the E115 virus, the virus could also be transmitted from vaccinated chickens to naïve contact chickens. Collectively, our findings highlight the need for avoiding the mixing of different bird species to reduce cross-species transmission and for surveillance of NDV in waterfowl.

Gga-miR-19b-3p Inhibits Newcastle Disease Virus Replication by Suppressing Inflammatory Response via Targeting RNF11 and ZMYND11

Newcastle disease (ND), an acute and highly contagious avian disease caused by virulent Newcastle disease virus (NDV), often results in severe economic losses worldwide every year. Although it is clear that microRNAs (miRNAs) are implicated in modulating innate immune response to invading microbial pathogens, their role in host defense against NDV infection remains largely unknown. Our prior study indicates that gga-miR-19b-3p is up-regulated in NDV-infected DF-1 cells (a chicken embryo fibroblast cell line) and functions to suppress NDV replication. Here we report that overexpression of gga-miR-19b-3p promoted the production of NDV-induced inflammatory cytokines and suppressed NDV replication, whereas inhibition of endogenous gga-miR-19b-3p expression had an opposite effect. Dual-luciferase and gene expression array analyses revealed that gga-miR-19b-3p directly targets the mRNAs of ring finger protein 11 (RNF11) and zinc-finger protein, MYND-type containing 11 (ZMYND11), two negative regulators of nuclear factor kappa B (NF-κB) signaling, in DF-1 cells. RNF11 and ZMYND11 silencing by small interfering RNA (siRNA) induced NF-κB activity and inflammatory cytokine production, and suppressed NDV replication; whereas ectopic expression of these two proteins exhibited an opposite effect. Our study provides evidence that gga-miR-19b-3p activates NF-κB signaling by targeting RNF11 and ZMYND11, and that enhanced inflammatory cytokine production is likely responsible for the suppression of NDV replication.

Role of Pigeons in the Transmission of Avian Avulavirus (Newcastle Disease-Genotype VIId) to Chickens

Simple Summary

Newcastle disease is an acute fatal disease of poultry. All broiler chickens and 8/15 pigeons were killed when infected intramuscularly (IM), while 7/10 chickens and only 1/15 pigeons were killed when infected intranasally (IN) with the virus in an experimental setting. Chickens in contact with infected pigeons developed severe respiratory, digestive and nervous signs. The mortality rates in chickens in contact with IM and IN infected pigeons were 2/5 and 3/5, respectively. Chickens in contact with IM infected pigeons had higher viral shedding titres than those in contact with IN infected pigeons. Free-range pigeons are considered an efficient carrier and transmitter of NDV-VIId to commercial broiler chickens raised in open houses.

Abstract

Newcastle disease is an acute fatal disease of poultry. The aim of this study was to determine the dynamics of the transmission of avian avulavirus (velogenic viscerotropic Newcastle disease-genotype VIId) from either intramuscularly (IM)- or intranasally (IN) infected 8-week-old Egyptian Baladi pigeons in contact with commercial Arbor Acres broiler chickens (4 weeks of age). The mortality of IM infected chickens and pigeons was 10/10 for chickens and 8/15 for pigeons, while the mortality of IN infected chickens and pigeons was 7/10 for chickens and only 1/15 for pigeons. The concentration of viral shedding in the oropharynx was higher than that in the cloaca for both IN and IM infected pigeons. Pigeons infected IN continued shedding the virus from the oropharynx from the 4th day post-infection (dpi) up to the 16th dpi, while IM infected pigeons stopped oropharyngeal shedding at the 11th dpi. Chickens in contact with infected pigeons developed severe respiratory, digestive and nervous signs. The mortality rates in chickens in contact with IM and IN infected pigeons were 2/5 and 3/5, respectively. Chickens in contact with IM infected pigeons showed higher viral shedding titres in both the oropharynx and cloaca than chickens in contact with pigeons infected IN. In conclusion, free-range pigeons are considered an efficient carrier and transmitter of NDV-VIId compared to commercial broiler chickens raised in open houses.

Molecular characterization, pathogenicity, and protection efficacy analysis of 2 wild-type lentogenic class I Newcastle disease viruses from chickens in China

In this study, 2 wild-type Newcastle disease viruses (NDVs), designated as CK/GX/65/15 and CK/GX/26/15, were isolated from asymptomatic chickens in Guangxi province, China. They were identified as lentogenic NDV with mean death time (MDT) above 90 and intracerebral pathogenicity index (ICPI) below 0.7. The results of complete genome sequence analysis show that the 2 NDV strains are members of class I genotype 3 with the length 15,198 nt, which followed the "rule of six" and the order 3'-NP-P-M-F-HN-L-5'. In addition, 8 amino acid substitutions were identified in the functional domains of fusion protein (F) of CK/GX/65/15 and 9 in CK/GX/26/15, whose amino acid sequences of F protein cleavage site are 112E-R-Q-E-R-L117. The isolates were found to be apathogenic in specific pathogen free (SPF) chickens and ducks without morbidity or mortality. Furthermore, the protection study shows that isolates can provide the same effective protection against a major NDV virulent strain in China (class II genotype VII) as the commercial vaccine LaSota. Moreover, vaccination with isolates reduced number of chickens shedding virus compared to those vaccinated with LaSota. In conclusion, 2 wild-type NDV strains exhibited fine protection efficacy against genotype VII NDV in poultry and can be considered as candidate vaccines against NDV.

Recombinant Newcastle disease virus (NDV) La Sota expressing the haemagglutinin-neuraminidase protein of genotype VII NDV shows improved protection efficacy against NDV challenge

Intensive vaccination strategies against Newcastle disease (ND) have been implemented in many countries for a long time, but ND outbreaks still occur frequently, with most isolates belonging to genotype VII of Newcastle disease virus (NDV). Many researchers have revealed that vaccines closely matched to epidemic viruses provide better protection. Therefore, using a previously established reverse genetics system, we generated a recombinant NDV vaccine strain (rLa Sota-HN) based on the La Sota vaccine strain expressing the haemagglutinin-neuraminidase (HN) protein of genotype VII NDV. The pathogenicity of the recombinant virus was confirmed by the mean death time in 9-day-old specific-pathogen-free embryonated chicken eggs and the intracerebral pathogenicity index in 1-day-old specific-pathogen-free chickens. Subsequently, 1-day-old chickens were immunized with commercial vaccine La Sota and recombinant virus rLa Sota-HN and then challenged with virulent genotype VII NDV strain. The results indicated that recombinant virus rLa Sota-HN provided increased protection of vaccinated chickens from morbidity and mortality, and inhibited the shedding of virulent virus after challenging with genotype VII virus, compared with the conventional vaccine La Sota. Our findings indicated that rLa Sota-HN is a promising vaccine candidate to improve the protection efficiency against ND in chickens, thereby preventing frequent outbreaks of this disease.

A novel recombinant attenuated Newcastle disease virus expressing H9 subtype hemagglutinin protected chickens from challenge by genotype VII virulent Newcastle disease virus and H9N2 avian influenza virus

Newcastle disease virus (NDV) and H9 subtype avian influenza virus (AIV) are two avian pathogens across the globe. Inasmuch as most poultry flocks worldwide are vaccinated with a live low-virulence or attenuated NDV vaccine, we embarked on the development of vaccine prototypes that would have dual specificities and would allow a single immunization against both avian influenza (AI) and Newcastle disease (ND). Therefore, in the present work, a cloned full-length copy of the genome of the lentogenic NDV strain rmNA-1 was selected as a backbone vector to construct three chimeric NDVs that expressed (i) the ORF encoding the HA, (ii) the ectodomain of HA fused with the transmembrane domain and cytoplasmic tail regions derived from the NDV F protein and (iii) the ectodomain of HA fused with a short GS linker and the GCN4 sequences, and designated as rmNA-H9, rmNA-H9F, and rmNA-H9 (ECTO), respectively. rmNA-H9, rmNA-H9F, and rmNA-H9 (ECTO) stably expressed the modified HA gene for 10 egg passages and the three recombinants were found innocuous to chickens. The insertion of the chimeric HA-F, rather than HA-ECTO or ORF of HA, resulted in a recombinant virus with enhanced incorporation of the HA protein into the viral surface. A single immunization of SPF chickens with the three recombinants induced NDV- and AIV H9-specific antibodies, and protected chickens against a challenge with a lethal dose of velogenic NDV or AIV H9N2. Remarkably, non-shedding of influenza virus and higher levels of H9 subtype HI titers were observed 7 days post challenge (dpc) in rmNA-H9F vaccinated chickens, than other recombinants. Furthermore, a prime-boost vaccination of chickens with rmNA-H9F induced higher levels of NDV- and H9- HI and secretory IgA, as well as reduced viral shedding and virus-induced gross lesions, compared with the commercial vaccine. Therefore, the recombinant rmNA-H9F is a promising bivalent vaccine candidate against NDV and H9 subtype AIV in chickens.

Recombinant infectious laryngotracheitis virus expressing Newcastle disease virus F protein protects chickens against infectious laryngotracheitis virus and Newcastle disease virus challenge

In this study, we isolated and identified an infectious laryngotracheitis virus (ILTV) that was naturally avirulent in specific pathogen-free (SPF) chickens, with the aim of developing a more efficacious vaccine against ILTV and Newcastle disease virus (NDV). We constructed a US9-deleted ILTV mutant based on this avirulent ILTV, and then constructed a recombinant ILTV (designated ILTV-ΔUS9-F) expressing the fusion protein (F) of the genotype VII NDV based on the US9-deleted ILTV mutant. Expression of the F protein in ILTV-ΔUS9-F-infected cells was confirmed by indirect immunofluorescence assay and western blotting. The inserted F gene was stably expressed in ILTV-ΔUS9-F. The growth kinetics of ILTV-ΔUS9-F were comparable to those of the wild-type ILTV strain. Vaccination of SPF chickens with ILTV-ΔUS9-F produced no clinical signs but did induce low levels of NDV-specific enzyme-linked immunosorbent assay and neutralizing antibodies. A single vaccination with 10⁴ plaque-forming units (PFU) of ILTV-ΔUS9-F provided good protection against both genotype VII and IX NDVs based on clinical signs, similar to the protection provided by the commercial live La Sota vaccine. Notably, ILTV-ΔUS9-F limited the replication and shedding of genotype VII NDV from oropharyngeal swabs more efficiently than the La Sota vaccine. In addition, vaccination with lower doses (10³ and 10² PFU) of ILTV-ΔUS9-F also provided sufficient clinical protection. These results indicated that ILTV-ΔUS9-F may be a bivalent vaccine candidate against both ILTV and NDV.

Pathobiology of Avian avulavirus 1: special focus on waterfowl

Avian avulaviruses serotype 1 (abbreviated as APMV-1 for the historical name avian paramyxovirus 1) are capable of infecting a wide spectrum of avian species with variable clinical symptoms and outcomes. Ease of transmission has allowed the virus to spread worldwide with varying degrees of virulence depending upon the virus strain and host species. The emergence of new virulent genotypes from global epizootics, and the year-to-year genomic changes in low and high virulence APMV-1 imply that distinct genotypes of APMV-1 are simultaneously evolving at different geographic locations across the globe. This vast genomic diversity may be favoured by large variety of avian species susceptibility to APMV-1 infection, and by the availability of highly mobile wild birds. It has long been considered that waterfowls are not sensitive to APMV-1 and are unable to show any clinical signs, however, outbreaks from the 90's contradict these concepts. The APMV-1 isolates are increasingly reported from the waterfowl. Waterfowl have strong innate immune responses, which minimize the impact of virus infection, however, are unable to prevent the viral shedding. Numerous APMV-1 are carried by domestic waterfowl intermingling with terrestrial poultry. Therefore, commercial ducks and geese should be vaccinated against APMV-1 to minimize the virus shedding and for the prevention the transmission. Genetic diversity within APMV-1 demonstrates the need for continual monitoring of viral evolution and periodic updates of vaccine seed-strains to achieve efficient control and eradication of APMV-1 in waterfowls.

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.

Molecular characterization of full fusion protein (F) of Newcastle disease virus genotype VIId isolated from Egypt during 2012-2016

Aim:

The aim of this work was to study the full F gene sequence of Newcastle disease virus (NDV) in regard to pathotyping and genotyping and to study the evolution of this NDV in Egypt.

Materials and Methods:

The present study was conducted using samples from seven suspected NDV flocks of vaccinated chickens during 2012-2016 from six governorates in Egypt. The NDV was successfully isolated from pathological specimens through inoculation in specific pathogen-free embryonated chicken eggs.

Results:

Pathogenicity of the NDV isolates has been estimated through intracerebral pathogenicity index and ranged from 1.66 to 1.73 which indicates the velogenic type of NDV isolates. Pathotyping and genotyping of these isolates were done through sequencing of full-length F gene. Results indicated that the seven NDV isolates showed characteristic cleavage site motif (112RRQKRF117) for the velogenic strains of NDV. Phylogenetic analysis of the F gene clustered these isolates within Group I of genotype VIId within Israeli strains NDV/IS/2015, NDV-Ch/SD883, and most of the Middle East strains. Six of seven sequenced isolates have six potential N-linked glycosylation sites. The neutralization epitope on the five antigenic sites of fusion is conserved in all Egyptian strains of this study except NDV-KFR-B7-2012 which has a substitution at D 170 N in epitope A4. In all our strains, 10 cysteine residues are recorded, except one loss of cysteine at residue 370 in both NDV-EG-35-2014 and NDV-GHB-328F-2016.

Conclusion:

All viruses in this study have 52 amino acid substitutions within fusion gene in compared with Lasota strain that reveals importance for its antigenic and structural function. The present work highlights the important need to sequence F gene of NDV genotype VIId to investigate the evolution of this NDV in Egypt.

Newcastle disease virus: is an updated attenuated vaccine needed?

Newcastle disease virus (NDV) is a major cause of infectious mortality and morbidity in poultry worldwide. It is an enveloped virus with two outer-membrane proteins-haemagglutinin-neuraminidase (HN) and fusion protein (F)-that induce neutralizing antibodies. All NDV strains belong to one serotype. Yet, NDV vaccines, derived from genotype II, do not fully prevent infection or shedding of viruses from other genotypes. The aim of this study was to test if an updated vaccine is required. For this purpose, NDVs isolated from infected, albeit heavily vaccinated, flocks were genetically and immunologically characterized. Amino acid differences in F and HN protein sequences were identified between the vaccine strain and each of the isolates, some specifically at the neutralization sites. Whereas all tested isolates showed similar haemagglutination-inhibition (HI) titres, 100-100,000 times higher antibody-to-virus ratios were needed to neutralize viral propagation in embryos by the field isolates versus the vaccine strain. As a result, a model and an equation were developed to explain the phenomenon of escape in one-serotype viruses and to calculate the HI values needed for protection, depending on variation rate at key positions. In conclusion, to confer full protection against NDVs that differ from the vaccine strain at the neutralizing epitopes, very high levels of antibodies should be raised and maintained to compensate for the reduction in the number of effective epitopes; alternatively, an adjusted attenuated vaccine should be developed-a task made possible in the current era of reverse vaccinology.

Saponin-adjuvanted vaccine protects chickens against velogenic Newcastle disease virus

Despite extensive vaccination campaigns, Newcastle disease virus (NDV) remains endemic in many countries worldwide, and factors that contribute to this failure include mismatched vaccines, partial immunization, and poor husbandry practices. In order to overcome the problem of genetic divergence between circulating field strains and vaccine strains, we saponin-adjuvanted an Egyptian field strain and assessed its safety and immunogenicity in chickens. Immunization of chickens with the vaccine followed by challenge with a velogenic reference strain revealed the potential of the saponin-adjuvanted vaccine to induce a strong immune response that resulted in complete protection of chickens. Importantly, in vaccinated chickens, virus shedding was abolished, providing an added advantage over the currently available commercial live-attenuated and inactivated vaccines, which are unable to prevent shedding. A histopathological investigation demonstrated that the vaccinated chickens had less-severe lesions than challenged unvaccinated and mock-vaccinated chickens. We propose using this formulation as an alternative and improved NDV vaccine platform that can be exploited to control disease not only in Egypt but also in other disease-endemic countries.

Recombinant Newcastle disease virus (NDV) expressing Duck Tembusu virus (DTMUV) pre-membrane and envelope proteins protects ducks against DTMUV and NDV challenge

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Firstly generated a NDV-vectored Duck Tembusu Virus (DTMUV) bivalent vaccine that expressing the pre-membrane and envelope proteins of DTMUV.

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Evaluated the efficacy of the NDV-vectored Duck Tembusu Virus bivalent vaccine.

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Provided a new method for NDV and DTMUV controlling in waterfowl.

The newly emerged Duck Tembusu virus (DTMUV) is responsible for considerable economic loss in waterfowl-raising areas in China since 2010. Meanwhile, the virulent Newcastle disease virus (NDV) has also caused sporadic outbreaks in waterfowl. The individual vaccines against both diseases are available, however, there is no bivalent or combined vaccine for either disease. Here, we constructed a recombinant NDV-vectored vaccine candidate that expresses the pre-membrane (prM) and envelope (E) genes from DTMUV, designated as aGM/prM + E. The foreign prM and E proteins were stably expressed in aGM/prM + E and exhibited similar pathogenicity but higher growth kinetics than those of the parental virus. The aGM/prM + E carries a fusion cleavage site in accordance with avirulent viruses that have been frequently isolated from waterfowl, and induced remarkably (p < 0.001) higher NDV-specific hemagglutination inhibition (HI) titers than commercially available live NDV vaccines (LaSota strain). The aGM/prM + E also elicited significantly higher (p < 0.05) virus neutralization (VN) titers than commercially available DTMUV inactivated vaccines (HB strain). The aGM/prM + E not only provided complete protection against NDV challenge but also reduced the gross lesions on ovarian folliculi and provided 80% protection against DTMUV in ducks. We note that the aGM/prM + E vaccine can prevent challenged ducks from shedding of NDV and DTMUV. Our results suggest that the candidate vaccine aGM/prM + E would help decrease NDV and DTMUV transmissions in waterfowl raising areas in China.

A novel genotype VII Newcastle disease virus vaccine candidate generated by mutation in the L and F genes confers improved protection in chickens

Administration of vaccines combined with the good management and strict biosecurity is an effective way for Newcastle disease (ND) control. However, vaccine failure is continuously reported in some countries mainly because the antigenic difference between the used vaccine and field strains even they are of one serotype. Therefore, development of antigen-matched ND vaccines is needed to improve the vaccine efficacy in birds. In this study, we introduced four site mutations, K1756A, D1881A, K1917A and E1954Q, respectively, into the large protein gene of the virulent genotype VII Newcastle disease virus (NDV) G7 strain using reverse genetics technology. Four rescued NDVs were sharply attenuated for the pathogenicity in chickens. One of these mutants, E1954Q, was further manipulated by replacing the F cleavage site sequence of typical velogenic strains with that of the LaSota vaccine, resulting in a new mutant, G7M. Biological characterization showed that G7M was safe and genetically stable after serial passages in embryos and chickens. Vaccination of chickens with G7M induced a progressive elevation of the homologous antibodies and markedly higher CD8⁺ T cell percentage, T cell proliferation and IFN-γ than LaSota. G7M conferred full protection against genotype VII NDV challenge, and more importantly, it effectively reduced the challenge virus replication and shedding in chickens. Together, our data suggest that G7M is a promising genotype VII vaccine candidate, and the novel attenuation approach designed in this study could be used to develop new antigen-matched NDV vaccines.

Molecular evolution and epidemiological links study of Newcastle disease virus isolates from 1995 to 2016 in Iran

In the case of Newcastle disease virus, multiple factors such as host adaptation, immune response evasion, and selective pressures have been suggested to result in evolution of viruses and the emergence of genetic variants. Multiple studies on virus classification and global epidemiological links have yielded consistent data. Here, we have performed a molecular analysis study of circulating Newcastle disease viruses in Iran (1995-2016). According to evolutionary divergences, subgenotype VIg, VIj, VIIj, VIId, XIIIa and XIIId isolates have been circulating in the country during a 21-year period. Based on data analysis, VIg isolates shared highest sequence identity with Russian and Polish isolates of the VIg subgenotype, while VIj subgenotype isolates (2012) were most similar to a virus isolated in 2015 in India. Analysis of the evolutionary divergence of subgenotype VIIj suggests that Chinese and Ukrainian viruses may have played a crucial role in the emergence of VIIj isolates. Evolutionary difference studies also indicated that XIIIa isolates circulating in Iran may have caused the emergence of adapted variants of subgenotype XIIId. Therefore, we propose that the evolutionary and epidemiological study of virulent Newcastle disease viruses could help to provide accurate molecular data about variants circulating in the region, thus aiding in the design of more efficient recombinant vaccines.

Genetic, antigenic, and pathogenic characteristics of Newcastle disease viruses isolated from geese in China

Four Newcastle disease virus (NDV) strains were isolated from domestic, commercial geese that showed clinical signs that were believed to be the result of NDV infections. The genetic, antigenic, and pathogenic characteristics of the 4 NDVs were compared with those of NDV strains that were isolated from chickens. The complete genomes of 2 of the NDV strains contained 15,186 nucleotides (nt); the other 2 contained 15,192 nt, and exhibited the typical genomic organization of genotype II NDV and molecular characteristics of VIId NDVs. Phylogenetic analysis confirmed that the genotype II and VIId NDVs that were isolated from geese belonged to the same clusters as the corresponding genotypes of the chicken isolates. A serologic assay demonstrated that the antigenic relatedness among the NDVs was associated with their genotypes, rather than their hosts, and that amino acid substitutions in the F and/or HN proteins may contribute to the antigenic differences among these NDV genotypes. Geese infected with genotype VIId NDVs that were isolated from geese and chickens showed similar pathologic characteristics. NDVs that were isolated from geese did not differ in genetic, serologic, and pathogenic characteristics from those isolated from chickens, indicating that these NDVs were derived from chicken NDVs. Given the significance of geese in NDV epidemiology, effective biosecurity measures should be adopted to prevent the interspecies transmission of NDVs.

Evaluation of fusion protein cleavage site sequences of Newcastle disease virus in genotype matched vaccines

Newcastle disease virus (NDV) causes a devastating poultry disease worldwide. Frequent outbreaks of NDV in chickens vaccinated with conventional live vaccines suggest a need to develop new vaccines that are genetically matched against circulating NDV strains, such as the genotype V virulent strains currently circulating in Mexico and Central America. In this study, a reverse genetics system was developed for the virulent NDV strain Mexico/01/10 strain and used to generate highly attenuated vaccine candidates by individually modifying the cleavage site sequence of fusion (F) protein. The cleavage site sequence of parental virus was individually changed to those of the avirulent NDV strain LaSota and other serotypes of avian paramyxoviruses (APMV serotype-2, -3, -4, -6, -7, -8, and -9). In general, these mutations affected cell-to-cell fusion activity in vitro and the efficiency of the F protein cleavage and made recombinant Mexico/01/10 (rMex) virus highly attenuated in chickens. When chickens were immunized with the rMex mutant viruses and challenged with the virulent parent virus, there was reduced challenge virus shedding compared to birds immunized with the heterologous vaccine strain LaSota. Among the vaccine candidates, rMex containing the cleavage site sequence of APMV-2 induced the highest neutralizing antibody titer and completely protected chickens from challenge virus shedding. These results show the role of the F protein cleavage site sequence of each APMV type in generating genotype V-matched vaccines and the efficacy of matched vaccine strains to provide better protection against NDV strains currently circulating in Mexico.

Efficacy of an inactivated bivalent vaccine against the prevalent strains of Newcastle disease and H9N2 avian influenza

Background

Newcastle disease (ND) and avian influenza subtype H9N2 (H9N2 AI) are two of the most important diseases of poultry, causing severe economic losses in the global poultry industry. Vaccination is an effective way to prevent and control the spread of ND virus (NDV) and H9N2 AI virus (AIV), but the antigenic differences between the current circulating strains and the vaccine strains might account for recent ND and H9N2 AI outbreaks in vaccinated poultry flocks.

Methods

We developed an inactivated bivalent H9N2 and NDV vaccine based on the current prevalent strains of H9N2 AIV and NDV in China and evaluated its efficacy in chickens in this study.

Results

The results indicated that the inactivated bivalent vaccine could induce a fast antibody response in vaccinated chickens. The hemagglutination inhibition (HI) titer in the sera increased rapidly, and the highest HI titer was observed at 4 weeks post-vaccination (wpv) with a mean titre of 8.6 log₂ for NDV and 9.5 log₂ for H9N2. Up until 15 wpv, HI titers were still detectable at a high level of over 6 log₂. The immunized chickens showed no signs of disease after challenge at 3 wpv with the prevalent strains of NDV and H9N2 AIV isolated in 2012–2014. Moreover, viral shedding was completely inhibited in vaccinated chickens after challenge with H9N2 AIV and inhibited by at least 90% with NDV compared to the controls at 5dpc.

Conclusions

Our findings suggest that the inactivated NDV and H9N2 vaccine induces a fast and strong antibody response in vaccinated chickens and is efficacious in poultry against NDVs and H9N2 AIVs.

Genome Sequence of a Virulent Genotype III Newcastle Disease Virus Isolated from Laying Ducks in China

Here, we report the complete genome sequence of a virulent Newcastle disease virus (NDV) strain HN1007, isolated from diseased duck flocks in Henan, China, in 2010. The isolate has a genome length of 15,186 nucleotides, and was classified as a member of genotype III of class II.

Deterioration of eggshell quality is related to calbindin in laying hens infected with velogenic genotype VIId Newcastle disease virus

The aim of this study was to determine the mechanism by which Newcastle disease virus (NDV) affects eggshell quality. Thirty-week-old specific pathogen free (SPF) egg-laying hens were inoculated with the velogenic genotype VIId NDV strain (infected group) or with inoculating media without virus (control group) by combined intraocular and intranasal routes. The levels of CaBP-D28k mRNA expression in the uterus, a gene related to eggshell quality, were examined by quantitative reverse transcriptase polymerase chain reaction (RT-PCR). The quality of eggshells was analyzed by scanning electron microscopy (SEM). The infected group showed a marked decline in egg production when compared to the control group. The NDV antigen was found more abundantly in the glandular epithelium of the infected hens' uteri from 1 to 15 d post-inoculation (dpi). The levels of CaBP-D28k mRNA expression in the uteri of infected hens were significantly lower than in the control hens from 3 to 15 dpi (P < 0.05). The changes in the Ca concentrations in the eggshells were consistent with the expression of CaBP-D28k mRNA in the infected hens. Ultrastructural examination of eggshells showed significantly reduced shell thickness in the infected hens from 1 to 15 dpi (P < 0.05). Furthermore, obvious changes in the structure of the external shell surface and shell membrane were detected in the infected hens compared with the control hens. In conclusion, the current study confirmed that velogenic genotype VIId NDV infection is associated with the deterioration of the eggshell quality of the laying hens.

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.

Co-circulation of genetically distinct groups of avian paramyxovirus type 1 in pigeon Newcastle disease in Iran

Pigeons are considered as one of the major natural reservoirs in the epidemiology of Newcastle disease (ND). In this study, the partial sequence of fusion protein gene of 17 pigeon-origin ND viruses (NDVs) isolated during 2012-2013 in Iran was analysed. Since the studied isolates showed F0 protein cleavage sites compatible with velogenic NDVs, all were considered as virulent NDVs. Two isolates carried 112RRQKRF117 as the cleavage site motif, whereas the rest demonstrated 112KRQKRF117 motif which just recently has been reported among Iranian virulent NDVs. Phylogenetic analysis divided all these diverse isolates in two distinct clusters within class II genotype VI. Based on the partial fusion protein gene sequence, 15 out of 17 isolates showed the highest genetic identity to subgenotype VIb/2 and the other two isolates were placed in a distinct genetic group of genotype VI. Based on recent findings, at least two different sublineages of genotype VI are causing the ND outbreaks in the pigeon population and are circulating simultaneously along with virulent NDVs of genotype VII in various species in Iran. The continuing circulation of a diverse group of virulent NDVs as an enzootic in widespread species such as pigeon can cause outbreaks in commercial poultry flocks and also failure in controlling programmes. Therefore, the constant monitoring and awareness of the virus characteristics should be considered in controlling programmes against ND in Iran.

Generation and evaluation of a genetically attenuated Newcastle disease virus rGM-VIIm as a genotype-matched vaccine

Despite intensive vaccination campaigns, outbreaks of Newcastle disease (ND) have been frequently reported in China, especially of genotype VII that first emerged in the late 1990s. Given the dire need for vaccines against the circulating genotype VII virus, we developed an alternative method to recover a highly virulent recombinant GM (rGM) virus that involves a T7 system with a hammerhead ribozyme sequence introduced downstream of the T7 promoter. By changing the F₀ polybasic cleavage site RRQKR↓F to the monobasic GRQGR↓L, we generated a mutant virus (rGM-VIIm) that was found to be highly attenuated in chickens. The rGM-VIIm virus not only produced fourfold higher hemagglutination assay (HA) titers than the parental virus, but also exhibited genetic stability after 15 continuous passages in specific-pathogen-free (SPF) embryonated eggs. Whether live or inactivated, rGM-VIIm and LaSota vaccines can protect vaccinated birds from GM challenge infection. However, live and inactivated rGM-VIIm vaccines reduced virus shedding of the homologous challenge virus significantly better than the LaSota virus vaccine did. Altogether, our results suggest that rGM-VIIm vaccines could aid in the control of ND in China.

Presence of Vaccine-Derived Newcastle Disease Viruses in Wild Birds

Our study demonstrates the repeated isolation of vaccine-derived Newcastle disease viruses from different species of wild birds across four continents from 1997 through 2014. The data indicate that at least 17 species from ten avian orders occupying different habitats excrete vaccine-derived Newcastle disease viruses. The most frequently reported isolates were detected among individuals in the order Columbiformes (n = 23), followed in frequency by the order Anseriformes (n = 13). Samples were isolated from both free-ranging (n = 47) and wild birds kept in captivity (n = 7). The number of recovered vaccine-derived viruses corresponded with the most widely utilized vaccines, LaSota (n = 28) and Hitchner B1 (n = 19). Other detected vaccine-derived viruses resembled the PHY-LMV2 and V4 vaccines, with five and two cases, respectively. These results and the ubiquitous and synanthropic nature of wild pigeons highlight their potential role as indicator species for the presence of Newcastle disease virus of low virulence in the environment. The reverse spillover of live agents from domestic animals to wildlife as a result of the expansion of livestock industries employing massive amounts of live virus vaccines represent an underappreciated and poorly studied effect of human activity on wildlife.