Genomic analysis of Newcastle disease virus strain NA-1 isolated from geese in China

Protective effects of a novel chimeric virus-like particle vaccine against virulent NDV and IBDV challenge

Newcastle disease (ND) and infectious bursal disease (IBD) pose significant threats to the chicken industry, causing substantial economic losses. Currently, immunization through vaccination is the most effective strategy to prevent ND and IBD but currently used traditional vaccines, including inactivated or attenuated vaccines, face challenges in achieving a balance between immunogenicity and safety. To develop a green and efficient novel vaccine for ND and IBD, we developed a bivalent chimeric virus-like particle vaccine (ND-IBD cVLPs) displaying the ND virus (NDV) HN protein and the IBD virus (IBDV) VP2 protein based on the ND VLPs carrier platform and insect baculovirus expression system. This study aimed to evaluate the immunogenicity and protective efficacy of ND-IBD cVLPs in specific pathogen-free chickens. Chickens were immunized with 50 µg of purified ND-IBD cVLPs at 7 days old, boosted at 21 days old, and challenged at 42 days old. The results demonstrated that ND-IBD cVLPs stimulated highly effective hemagglutination inhibition antibody levels against NDV HN protein and enzyme-linked immunosorbent assay antibody levels against the IBDV VP2 protein. Furthermore, ND-IBD cVLPs provided complete protection against virulent NDV and IBDV challenges and mitigated pathological damage to the lung caused by NDV infection and the bursa of Fabricius caused by IBDV infection. These findings suggest that ND-IBD cVLPs hold promise as a safe and efficient novel vaccine candidate for the effective prevention of ND and IBD, extending the development of a foreign protein delivery platform of ND VLPs.

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.

Intense Innate Immune Responses and Severe Metabolic Disorders in Chicken Embryonic Visceral Tissues Caused by Infection with Highly Virulent Newcastle Disease Virus Compared to the Avirulent Virus: A Bioinformatics Analysis

The highly virulent Newcastle disease virus (NDV) isolates typically result in severe systemic pathological changes and high mortality in Newcastle disease (ND) illness, whereas avirulent or low-virulence NDV strains can cause subclinical disease with no morbidity and even asymptomatic infections in birds. However, understanding the host’s innate immune responses to infection with either a highly virulent strain or an avirulent strain, and how this response may contribute to severe pathological damages and even mortality upon infection with the highly virulent strain, remain limited. Therefore, the differences in epigenetic and pathogenesis mechanisms between the highly virulent and avirulent strains were explored, by transcriptional profiling of chicken embryonic visceral tissues (CEVT), infected with either the highly virulent NA-1 strain or the avirulent vaccine LaSota strain using RNA-seq. In our current paper, severe systemic pathological changes and high mortality were only observed in chicken embryos infected with the highly virulent NA-1 strains, although the propagation of viruses exhibited no differences between NA-1 and LaSota. Furthermore, virulent NA-1 infection caused intense innate immune responses and severe metabolic disorders in chicken EVT at 36 h post-infection (hpi), instead of 24 hpi, based on the bioinformatics analysis results for the differentially expressed genes (DEGs) between NA-1 and LaSota groups. Notably, an acute hyperinflammatory response, characterized by upregulated inflammatory cytokines, an uncontrolled host immune defense with dysregulated innate immune response-related signaling pathways, as well as severe metabolic disorders with the reorganization of host–cell metabolism were involved in the host defense response to the CEVT infected with the highly virulent NA-1 strain compared to the avirulent vaccine LaSota strain. Taken together, these results indicate that not only the host’s uncontrolled immune response itself, but also the metabolic disorders with viruses hijacking host cell metabolism, may contribute to the pathogenesis of the highly virulent strain in ovo.

Chimeric Newcastle Disease Virus-like Particles Containing DC-Binding Peptide-Fused Haemagglutinin Protect Chickens from Virulent Newcastle Disease Virus and H9N2 Avian Influenza Virus Challenge

Newcastle disease virus (NDV) and H9N2 subtype Avian influenza virus (AIV) are two notorious avian respiratory pathogens that cause great losses in the poultry industry. Current inactivated commercial vaccines against NDV and AIV have the disadvantages of inadequate mucosal responses, while an attenuated live vaccine bears the risk of mutation. Dendritic cell (DC) targeting strategies are attractive for their potent mucosal and adaptive immune-stimulating ability against respiratory pathogens. In this study, DC-binding peptide (DCpep)-decorated chimeric virus-like particles (cVLPs), containing NDV haemagglutinin-neuraminidase (HN) and AIV haemagglutinin (HA), were developed as a DC-targeting mucosal vaccine candidate. DCpep-decorated cVLPs activated DCs in vitro, and induced potent immune stimulation in chickens, with enhanced secretory immunoglobulin A (sIgA) secretion and splenic T cell differentiation. 40 μg cVLPs can provide full protection against the challenge with homologous, heterologous NDV strains, and AIV H9N2. In addition, DCpep-decorated cVLPs could induce a better immune response when administered intranasally than intramuscularly, as indicated by robust sIgA secretion and a reduced virus shedding period. Taken together, this chimeric VLPs are a promising vaccine candidate to control NDV and AIV H9N2 and a useful platform bearing multivalent antigens.

Evaluation of the safety and protection efficacy of an attenuated genotype vii newcastle disease virus strain as a candidate vaccine

Newcastle disease (ND) is a serious avian infectious disease, causing severe economic loss worldwide. Its prevention depends on comprehensive vaccination scheme against Newcastle disease virus (NDV). However, current vaccine strains are of different genotypes with prevalent circulating strains (genotype VII), with significant genetic distance. Our team previously generated a genotype matched attenuated NDV strain (rmNA-1). In this study, its safety and immunization efficacy were evaluated. Its lentogenic characteristic was stable for 25 generations in embryonated chicken eggs and for six generations in SPF chickens. Overdosed administration did not cause any clinical signs or pathogenic changes in chickens. As to its immunization effect, rmNA-1 stimulated a comparable serum NDV specific antibody level to a LaSota (genotype II) strain based commercial vaccine, and provided full protection against virulent genotype VII strain challenge, with significantly reduced virus shedding period.

A genotype VII Newcastle disease virus-like particles confer full protection with reduced virus load and decreased virus shedding

Newcastle disease (ND) is one of the most severe avian infectious disease inflicting a great loss on poultry industry worldwide. The control of ND relies on proper vaccination strategies. The vaccine strains of Newcastle disease virus (NDV) mainly belong to genotype I, II or III, which cannot fully prohibit virus shedding against the prevalent genotype VII virulent strain attack. To develop a safe, genotype matched vaccine candidate, we employed a bac-to-bac expression system and constructed a genotype VII NDV strain based virus-like particles (NDV VLPs). It was constructed with NDV M protein as the skeleton, and protective antigen F and HN proteins displayed on the surface. The NDV VLPs exhibited a similar appearance to the live NDV particles, but with denser F and HN proteins displayed on the surface. The immunization assay indicated that NDV VLPs stimulated a longer protection period, less tissue virus loading and shorter virus shedding period than the commercialized LaSota-formulated vaccine when challenged with genotype VII NDV strain. These results proposed the potential role of NDV VLPs as an alternative to current live genotype unmatched vaccine for the control and eliminate NDV in the avian flocks.

The virulence of NDV NA-1 strain regulated by the 3' leader or 5' trailer sequences

The 3' and 5' terminal regions of Newcastle disease virus (NDV) genome are cis-acting regulatory elements involved in replication, transcription, and packaging of genomic and anti-genomic viral RNA. There are 6 different nucleotides (nts) at the 3' and 34 different nts at the 5' end of genome in the velogenic NA-1 strain and lentogenic LaSota strain, sharing 90.00% and 70.18% identity, respectively. We investigated the roles of 3' and 5' terminus in the NA-1 strain in viral replication, virulence and pathogenicity. Three NA-1 strain-based recombinant viruses (rNA-L, rNA-T, and rNA-LT) were generated using reverse genetics by either replacing the 3' leader or 5' trailer sequence of NA-1 strain or both with the corresponding sequences of the LaSota strain. Viral replication kinetics and pathogenicity of rNA-L and rNA-T were indistinguishable to that of the parental NA-1 strain, demonstrating that individual replacement or 3' or 5' terminal sequences had little influence. However, the synchronal replacement of both 3' and 5' terminal sequences resulted in decreased viral plaque size, reduced virulence and weaker pathogenicity in 2-week-old chickens. Therefore, our results suggest that the 3' and 5' terminal sequences of NDV genome could only influence the viral virulence when worked collaboratively, while separate replacement would not alter its biological characteristics.

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.

Enhanced Replication of Virulent Newcastle Disease Virus in Chicken Macrophages Is due to Polarized Activation of Cells by Inhibition of TLR7

Newcastle disease (ND), caused by infections with virulent strains of Newcastle disease virus (NDV), is one of the most important infectious disease affecting wild, peridomestic, and domestic birds worldwide. Vaccines constructed from live, low-virulence (lentogenic) viruses are the most accepted prevention and control strategies for combating ND in poultry across the globe. Avian macrophages are one of the first cell lines of defense against microbial infection, responding to signals in the microenvironment. Although macrophages are considered to be one of the main target cells for NDV infection in vivo, very little is known about the ability of NDV to infect chicken macrophages, and virulence mechanisms of NDV as well as the polarized activation patterns of macrophages and correlation with viral infection and replication. In the present study, a cell culture model (chicken bone marrow macrophage cell line HD11) and three different virulence and genotypes of NDV (including class II virulent NA-1, class II lentogenic LaSota, and class I lentogenic F55) were used to solve the above underlying questions. Our data indicated that all three NDV strains had similar replication rates during the early stages of infection. Virulent NDV titers were shown to increase compared to the other lentogenic strains, and this growth was associated with a strong upregulation of both pro-inflammatory M1-like markers/cytokines and anti-inflammatory M2-like markers/cytokines in chicken macrophages. Virulent NDV was found to block toll-like receptor (TLR) 7 expression, inducing higher expression of type I interferons in chicken macrophages at the late stage of viral infection. Only virulent NDV replication can be inhibited by pretreatment with TLR7 ligand. Overall, this study demonstrated that virulent NDV activates a M1-/M2-like mixed polarized activation of chicken macrophages by inhibition of TLR7, resulting in enhanced replication compared to lentogenic viruses.

Generation and evaluation of a recombinant genotype VII Newcastle disease virus expressing VP3 protein of Goose parvovirus as a bivalent vaccine in goslings

Newcastle disease virus (NDV) and Goose parvovirus (GPV) are considered to be two of the most important and widespread viruses infecting geese. In this study, we generated a recombinant rmNA-VP3, expressing GPV VP3 using a modified goose-origin NDV NA-1 by changing the multi-basic cleavage site motif RRQKR↓F of the F protein to the dibasic motif GRQGR↓L as that of the avirulent strain LaSota as a vaccine vector. Expression of the VP3 protein in rmNA-VP3 infected cells was detected by immunofluorescence and Western blot assay. The genetic stability was examined by serially passaging 10 times in 10-day-old embryonated SPF chicken eggs. Goslings were inoculated with rmNA-VP3 showed no apparent signs of disease and developed a strong GPV and NDV neutralizing antibodies response. This is the first study demonstrating that recombinant NDV has the potential to serve as bivalent live vaccine against Goose parvovirus and Newcastle disease virus infection in birds.

The deletion of an extra six nucleotides in the 5' -untranslated region of the nucleoprotein gene of Newcastle disease virus NA-1 decreases virulence

Background

The virulent Newcastle disease virus (NDV) strain NA-1 (genotype VII) was isolated from an epizootic involving a flock of geese in Jilin Province, Northeast China, in 1999. Compared with the classical NDV strains, which have a genome size of 15,186 bp, the more recently isolated NDV strains, including that involved in the goose outbreak, have an extra six nucleotides in the 5′-untranslated region (UTR) of the nucleoprotein (NP) gene. This extra sequence, TCCCAC, is highly conserved and has been found in multiple NDV strains, including ZJ-1, WF00G, JSG0210, and NA-1. In the current study, an infectious clone from strain NA-1 was isolated and designated rNA-1. Subsequently, strain rNA-1 was mutated to delete the six-nucleotide insertion, producing strain rNA-1(−). Virulence of the recombinant virus was then assayed in chickens and geese.

Results

The recombinant virus rNA-1(−) showed similar biological characteristics to the parental NA-1 strain in DF-1 chicken fibroblast cells. However, the virulence of rNA-1(−) in 9-day-old embryonated chicken eggs and 1-day-old specific pathogen-free (SPF) chickens was decreased compared with the rNA-1 control. Furthermore, the virulence of the recombinant strain was slightly decreased in 1-day-old SPF chickens when compared with that in 1-day-old geese.

Conclusion

Following deletion of six nucleotides in the 5′-UTR of the NP gene of NDV strain NA-1, the virulence of the rNA-1(−) recombinant strain was decreased in both chickens and geese. However, rNA-1(−) was more virulent in chickens than geese, as seen by the higher intracerebral pathogenicity index value.

Molecular characterization and phylogenetic study of velogenic Newcastle disease virus isolates in Iran

The pathogenicity and genetic characterizations of six Newcastle disease virus (NDV) isolates obtained from chicken farms in six different regions in Iran were carried out using conventional and molecular techniques. Based on the pathogenicity indices (MDT, ICPI, and IVPI), all of these isolates were found to be velogenic (highly virulent) strains. A sequence analysis of the full-length mRNA encoding the fusion glycoprotein precursor (F0) of the NDV's fusion proteins F1 and F2 in these six isolates showed the presence of point mutations in form of nucleic acid substitutions at positions 82((C→T)), 83((T→C)), 736((A→G)), and 1,633((G→A)). However, the nucleic acid residues at positions 330-347 of the precursor F0 gene, corresponding to the cleavage site of the F0 protein, were found to have remained conserved among the six NDV isolates. A phylogenetic comparison between the six Iranian isolates and the NDVs whose F0 gene sequences were previously deposited in GenBank Database showed that all of the newly characterized Iranian NDV isolates belonged to genotype VII.

Lack of detection of host associated differences in Newcastle disease viruses of genotype VIId isolated from chickens and geese

Background

The goose is usually considered to be resistant even to strains of Newcastle disease virus (NDV) that are markedly virulent for chickens. However, ND outbreaks have been frequently reported in goose flocks in China since the late 1990s with the concurrent emergence of genotype VIId NDV in chickens. Although the NDVs isolated from both chickens and geese in the past 15 years have been predominantly VIId viruses, published data comparing goose- and chicken-originated ND viruses are scarce and controversial.

Results

In this paper, we compared genotype VIId NDVs originated from geese and chickens genetically and pathologically. Ten entire genomic sequences and 329 complete coding sequences of individual genes from genotype VIId NDVs of both goose- and chicken-origin were analyzed. We then randomly selected two goose-originated and two chicken-originated VIId NDVs and compared their pathobiology in both geese and chickens in vivo and in vitro with genotype IV virus Herts/33 as a reference. The results showed that all the VIId NDVs either from geese or from chickens shared high sequence homology and characteristic amino acid substitutions and clustered together in phylogenetic trees. In addition, geese and chickens infected by goose or chicken VIId viruses manifested very similar pathological features distinct from those of birds infected with Herts/33.

Conclusions

There is no genetic or phenotypic difference between genotype VIId NDVs originated from geese and chickens. Therefore, no species-preference exists for either goose or chicken viruses and more attention should be paid to the trans-species transmission of VIId NDVs between geese and chickens for the control and eradication of ND.

Genomic sequence of an avian paramyxovirus type 1 strain isolated from Muscovy duck (Cairina moschata) in China

The complete sequence of an avian paramyxovirus type 1 (APMV-1) strain, FP1/02, isolated from Muscovy duck in China, was determined. Sequence analysis indicated that the complete genome of strain FP1/02 contained 15,192 nucleotides (nt), following the rule of six. The genome contained an extra 6-nt insertion in the non-coding region of the NP gene when compared with other APMV-1 strains, such as strains La Sota and Beaudette C. The cleavage site of the F protein was (112)R-R-Q-K-R↓F(117), indicating that the FP1/02 strain was virulent, but the morbidity and mortality varied with the species of duck. Genotypic analysis based on the F gene revealed that APMV-1 FP1/02 was a member of genotype VII. Phylogenetic analysis showed that the FP1/02 strain shared high identity with other APMV-1 strains such as ZJ1, SF02 and NA-1 isolated from geese.

Newcastle disease virus in Madagascar: identification of an original genotype possibly deriving from a died out ancestor of genotype IV

In Madagascar, Newcastle disease (ND) has become enzootic after the first documented epizootics in 1946, with recurrent annual outbreaks causing mortality up to 40%. Four ND viruses recently isolated in Madagascar were genotypically and pathotypically characterised. By phylogenetic inference based on the F and HN genes, and also full-genome sequence analyses, the NDV Malagasy isolates form a cluster distant enough to constitute a new genotype hereby proposed as genotype XI. This new genotype is presumably deriving from an ancestor close to genotype IV introduced in the island probably more than 50 years ago. Our data show also that all the previously described neutralising epitopes are conserved between Malagasy and vaccine strains. However, the potential implication in vaccination failures of specific amino acid substitutions predominantly found on surface-exposed epitopes of F and HN proteins is discussed.

Inhibition of Newcastle disease virus replication by RNA interference targeting the matrix protein gene in chicken embryo fibroblasts

Newcastle disease (ND) is an infectious viral disease of birds caused by the Newcastle disease virus (NDV), also known as avian paramyxovirus type 1 (AMPV-1), which leads to severe economic losses in the poultry industry worldwide. In this study, the application of RNA interference (RNAi) for inhibiting the replication of NDV in cell culture by targeting the viral matrix protein gene (M) is described. Two M-specific shRNA-expressing plasmid constructs, named pS(M641) and pS(M827), were evaluated for antiviral activity against the NDV strain NA-1 by cytopathic effects (CPE), virus titration and real-time RT-PCR. After 36h of infection, both pS(M641) and pS(M827) reduced virus titers by 79.4- and 31.6-fold, respectively, and they down-regulated mRNA expression levels of the matrix protein gene M by 94.6% and 84.8%, respectively, in chicken embryo fibroblast (CEF) cells, while only pS(M641) significantly decreased CPE, compared to the control group. These results indicated that the M gene 641 and 827 sites represent potential antiviral therapy targets, and RNAi targeting of the M gene could not only represent an effective treatment in Newcastle disease but also aid as a method for studying the replication of NDV.

Selection characterization on overlapping reading frame of multiple-protein-encoding P gene in Newcastle disease virus

The aim of this study was to characterize the molecular evolution of P and V protein genes of the Newcastle disease virus (NDV). The P gene sequences of 55 NDV isolates, representing different chronological and geographic origins, were obtained from GenBank. In this paper, the evolution of the specific regions of the NDV P gene, encoding the P and V proteins, was analyzed. The nucleotides from the shared P/V region encoded the co-amino terminus of the two proteins, while the P-V/V-P region was respectively encoded by the nucleotides within the P ORF or the V ORF in the common sequence (after the mRNA editing site). As well, the P-cut region exclusively encoded the P protein. Finally, the P-V and V-P regions were further broken down into P1 and P2 fragments with the corresponding V1 and V2 fragments. In the P gene, the P-cut portion corresponding to the C-terminal of the P protein was the most highly conserved, while the P-V region was the most variable. This was interpreted as a lower constraint for function in the common sequence than in the unique P sequence that is known to contain an important function. Interestingly, in the common P-V/V-P function, variability of V1 was compensated by a higher conservation of the corresponding P1, and conversely for the P2/V2, which suggested that the flexibility of one ORF with less function served the purpose of allowing positive selection in the other overlapping ORF that exhibited more function.