Characterization of newly emerging Newcastle disease virus isolates from the People's Republic of China and Taiwan

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.

Newcastle disease virus: the past and current situation in Indonesia

The Newcastle disease virus (NDV) outbreak was first reported in Java Island, Indonesia, in 1926, which was then reported further in Newcastle-upon-Tyne, England. Nevertheless, the NDV is still endemic in Indonesia, with outbreaks occurring in free-range and commercial chicken farms. The dynamic evolution of the NDV has led to the further development of vaccines and diagnostic tools for more effective control of this virus. This paper discusses the history of the NDV occurrence, vaccines, the development of diagnostic tools, and the epidemiological condition of the NDV in Indonesia. Indonesia, which has the largest poultry population in the world after China, has challenges in preventing and controlling this virus that causes economic losses to the farmers and has an impact on the welfare of the poultry farming community in Indonesia.

Simultaneous Expression of Chicken Granulocyte Monocyte Colony-Stimulating Factor and the Hemagglutinin-Neuraminidase Epitope of the Virulent Newcastle Disease Virus Genotype VII C22 Strain in a Functional Synthetic Recombinant Adenovirus as a Genotype-Matched Vaccine with Potential Antiviral Activity

When it comes to the prevention of clinical signs and mortality associated with infection of the Newcastle disease virus (NDV), vaccination has been very effective. However, recent evidence has proven that more highly virulent strains are emerging that bypass existing immune protection and pose a serious threat to the global poultry industry. Here, a novel rescued adenovirus 5-coexpressed chicken granulocyte monocyte colony-stimulating factor (ChGM-CSF) bio-adjuvant and C22-hemagglutinin-neuraminidase (HN) boosted chickens' immunological genetic resistance and thus improved the immunological effectiveness of the critical new-generation vaccine in vitro and in vivo. Accordingly, the hemagglutination inhibition (HI) titers (log2) of the recombinant adenovirus (rAdv)-ChGM-CSF-HN-immunized chickens had greater, more persistent, and longer-lasting NDV-specific antibodies than the La Sota and rAdv-HN-inoculated birds. Moreover, humoral and adaptive immunological conditions were shown to be in harmony after rAdv-ChGM-CSF-HN inoculation and uniformly enhanced the expression of alpha interferon (IFN-α), IFN-β, IFN-γ, interleukin-1β (IL-1β), IL-2, IL-16, IL-18, and IL-22. Postchallenge, the control challenge (CC), wild-type adenovirus (wtAdv), and rAdv-ChGM-CSF groups developed unique NDV clinical manifestations, significant viral shedding, high tissue viral loads, gross and microscopic lesions, and 100% mortality within 7 days. The La Sota, rAdv-HN, and rAdv-ChGM-CSF-HN groups were healthy and had 100% survival rates. The rAdv-ChGM-CSF-HN group swiftly regulated and stopped viral shedding and had lower tissue viral loads than all groups at 5 days postchallenge (dpc). Thus, the antiviral activity of ChGM-CSF offered robust immune protection in the face of challenge and reduced viral replication convincingly. Our advance innovation concepts, combining ChGM-CSF with a field-circulating strain epitope, could lead to the development of a safe, genotype-matched, universal transgenic vaccine that could eradicate the disease globally, reducing poverty and food insecurity. IMPORTANCE We studied the biological characterization of the developed functional synthetic recombinant adenoviruses, which showed a high degree of safety, thermostability, and genetic stability for up to 20 passages. It was demonstrated through both in vitro and in vivo testing that the immunogenicity of the proposed vaccine, which uses the T2A peptide from the Thosea asigna virus capsid protein supported by glycine and serine, helps with efficiency to generate a multicistronic vector, enables expression of two functional proteins in rAdv-ChGM-CSF-HN, and is superior to that of comparable vaccines. Additionally, adenovirus can be used to produce vaccines matching the virulent field-circulating strain epitope. Because there is no preexisting human adenoviral immunity detected in animals, the potency of adenoviral vaccines looks promising. Also, it ensures that the living vector does not carry the resistance gene that codes for the kanamycin antibiotic. Accordingly, a human recombinant adenoviral vaccine that has undergone biological improvements is beneficial and important.

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.

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.

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.

Development, Biological Characterization, and Immunological Evaluation of Virosome Vaccine against Newcastle Disease in Pakistan

Newcastle disease (ND) is a highly fatal, infectious, viral disease, and despite immunization with live and inactivated vaccines, the disease is still endemic, causing heavy morbidity and mortality leading to huge economic losses to the poultry industry in Pakistan. Therefore, the present study was aimed for the first time in the country at using novel virosomal technology to develop the ND vaccine using an indigenous highly virulent strain of the virus. ND virosome was prepared using Triton X-100, and SM2 Bio-Beads were used to remove the detergent and reconstitute the viral membrane into virosome. Confirmation was done by transmission electron microscopy and protein analysis by SDS-PAGE. In vitro cell adhesion property was observed by incorporating green fluorescent protein (GFP), producing plasmid into virosome and in vitro cell culture assay. Sterility, safety, and stability of the vaccine were tested before in vivo evaluation of immunogenicity and challenge protection study in commercial broiler. The virosome vaccine was administered (30 μg/bird) at days 7 and 14 through the intranasal route in comparison with commercially available live and inactivated ND vaccines. Results revealed significantly high (p < 0.05) and clinically protective hemagglutination inhibition (HI) antibody titers at 7, 14, 21, and 28 days postimmunization with the virosome vaccine in comparison to the negative control. The GMTs were comparable to live and inactivated vaccines with nonsignificant (p > 0.05) differences throughout the experiment. Antibody levels increased in all vaccinated groups gradually from the 7^th day and were maximum at 28^th-day postvaccination. In the virosome-administered group, GMT was 83.18 and 77.62 at 21^st and 28^th-days postvaccination, respectively. Challenge revealed 100%, 90%, and 80% protection in virosome, live, and inactivated vaccinated groups, respectively. Under given experimental conditions, we can conclude that ND virosome vaccine prepared from the indigenous virus was found to be safe and immunogenic.

Lithium chloride functions as Newcastle disease virus-induced ER-stress modulator and confers anti-viral effect

Newcastle disease is a severe clinical manifestation of avian species caused by Newcastle disease virus (NDV). Although several vaccination strategies are available to protect poultry against NDV infection, even then, outbreaks have been reported in the vaccinated birds. The lack of therapeutics against NDV makes the need for effective anti-viral drugs is of utmost importance. Lithium Chloride (LiCl) is a widely prescribed drug for the treatment of bipolar disorder, acute brain injuries, and chronic neurodegenerative diseases. Also, LiCl has been repurposed as an effective anti-viral drug for some viral infections. In the present work, we have investigated the efficacy of LiCl to inhibit NDV replication using in vitro, in ovo, and in vivo models. Our results collectively showed the modulation of NDV replication after the LiCl treatment. We also demonstrated that NDV induces endoplasmic reticulum stress (ER-stress), and a stress-inducible ER chaperone, glucose-regulating protein 78 (GRP78), was found to be over-expressed after NDV infection. Subsequently, the treatment of NDV infected cells with LiCl significantly reduced the transcript and protein levels of GRP78. Finally, we concluded that LiCl treatment protects the cells from ER-stress induced by the NDV infection.

Evolutionary dynamics and transmission patterns of Newcastle disease virus in China through Bayesian phylogeographical analysis

The Chinese poultry industry has experienced outbreaks of Newcastle disease (ND) dating back to the 1920s. However, the epidemic has exhibited a downtrend in recent years. In this study, both observational and genetic data [fusion (F) and haemagglutinin-neuraminidase genes (HN)] were analyzed, and phylogeographic analysis based on prevalent genotypes of Newcastle disease virus (NDV) was conducted for better understanding of the evolution and spatiotemporal dynamics of ND in China. In line with the observed trend of epidemic outbreaks, the effective population size of F and HN genes of circulating NDV is no longer growing since 2000, which is supported by 95% highest posterior diversity (HPD) intervals. Phylogeographic analysis indicated that the two eastern coastal provinces, Shandong and Jiangsu were the most relevant hubs for NDV migration, and the geographical regions with active NDV diffusion seemed to be constrained to southern and eastern China. The live poultry trade may play an important role in viral spread. Interestingly, no migration links from wild birds to poultry received Bayes factor support (BF > 3), while the migration links from poultry to wild birds accounted for 64% in all effective migrations. This may indicate that the sporadic cases of ND in wild bird likely spillover events from poultry. These findings contribute to predictive models of NDV transmission, and potentially help in the prevention of future outbreaks.

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.

Glycoprotein-C-gene-deleted recombinant infectious laryngotracheitis virus expressing a genotype VII Newcastle disease virus fusion protein protects against virulent infectious laryngotracheitis virus and Newcastle disease virus

To develop an alternative vectored vaccine against both Newcastle disease virus (NDV) and infectious laryngotracheitis virus (ILTV), the glycoprotein C (gC) gene was first deleted from an avirulent ILTV. Based on this gC-deleted ILTV mutant, a recombinant ILTV expressing the fusion protein (F) of a genotype VII NDV (designated ILTV-ΔgC-F) was then constructed. Expression of the NDV F protein in ILTV-ΔgC-F-infected LMH cells was examined with an immunofluorescence assay and western blotting. The F gene was stably maintained in the genome of ILTV-ΔgC-F and the F protein was stably expressed. Compared with the parental virus, ILTV-ΔgC-F demonstrated an increased penetration capacity in vitro, and an increased replication rate in vitro and in vivo. Both the parental virus and ILTV-ΔgC-F were avirulent in chickens. Vaccination of specific-pathogen-free chickens with ILTV-ΔgC-F induced ILTV-specific antibodies, detected with an enzyme-linked immunosorbent assay (ELISA), and provided complete clinical protection against virulent ILTV, although viral shedding and replication were detected in the respiratory tract in the early stage of infection in a very small number of birds. Vaccination with ILTV-ΔgC-F also provided significant protection against challenge with a virulent genotype VII NDV, although the level of NDV-specific antibodies detected with an ELISA was low. Notably, the numbers of birds that were positive for the virulent genotype VII NDV and the replication of the challenge virus NDV in selected target tissues were significantly lower in the ILTV-ΔgC-F-vaccinated chickens than in the control birds. Our results indicate that ILTV-ΔgC-F has potential utility as a bivalent candidate vaccine against both infectious laryngotracheitis and Newcastle disease.

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.

Molecular and biological characterization of some circulating strains of Newcastle disease virus in broiler chickens from Eastern Saudi Arabia in 2012-2014

Background and Aim:

Newcastle disease (ND) is a worldwide poultry disease that is historically known to cause severe losses in the poultry industry. In the present study, attempts were made to characterize ND virus (NDV) recovered from broiler chickens in the Eastern Region of Saudi Arabia from January 2012 to March 2014.

Materials and Methods:

Reverse transcription-polymerase chain reaction was used for the detection of NDV followed by partial sequencing of the fusion (F) gene. The intracerebral pathogenicity index (ICPI), mean death time (MDT), and complete sequencing of the hemagglutinin-neuraminidase (HN) gene were also used for further biological and molecular characterization.

Results:

NDV was detected at a rate of 9.6% (11/115) of the tested flocks, most of which were vaccinated against ND. F gene-based phylogeny and motifs of the fusion protein cleavage site (FPCS) showed segregation of Saudi isolates into two groups. The first group contained 10 isolates and was located in genotype II with the lentogenic motif ¹¹²GRQGRL¹¹⁷ at the FPCS. The second group contained one isolate and was located in genotype VII with velogenic motif ¹¹²RRQKRF¹¹⁷. Further characterization using the ICPI and MDT of two representative isolates showed virulence of both tested isolates. Phylogenetic analysis of the HN gene showed close nucleotide identity between the two isolates. A BLAST search for sequences similar to HN gene sequences showed high identity with isolates from the surrounding region.

Conclusion:

The present findings showed a low detection rate of NDV, possibly due to the wide application of vaccines, and the circulation of at least two NDV genotypes, II and VII, in the Eastern Region of Saudi Arabia. The present Saudi isolates may share common ancestors with isolates from the surrounding region.

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.

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.

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.

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.

Evaluating the efficacy of LaSota vaccination induced protection in chickens upon challenge with a genotype IV strain of Newcastle disease virus

Newcastle disease (ND) is a major risk to the poultry industry which results in severe economic loss throughout the world even with vaccination. The vaccine viruses that are used in many countries include the LaSota and other live viruses that were isolated in the early and late 1950s. Reports from several laboratories including ours indicate a greater variance of the circulating strains and recent classification indicates the existence of XVIII different genotypes of NDV strains. The efficiency of the LaSota vaccination in inducing protective immunity to different heterologous strains has been a question and its efficacy upon exposure to a virulent genotype IV strain has not been reported after 1989 world-wide except for India. Serum antibody negative (SAN) chicks of either sex obtained by hatching specific-pathogen-free (SPF) eggs were vaccinated with increasing doses of the vaccine virus from 10¹ to 10⁷ EID₅₀ per bird delivered through occulo-nasal route and challenged 20 days later with NDV-2K3 (genotype IV) strain of virus isolated in the year 2000 from pigeon in India. The birds were monitored for serum antibody titers and following challenge for morbidity, mortality, viral load in the cloacal swab and different tissues. We could clearly show that a minimum vaccine titre of 10⁴ EID₅₀ could establish protective antibody levels and also prevent viral replication post challenge upon exposure to the virulent genotype IV strain. We conclude based on our results and previous observation that there do exist differences in the levels of the antibody that could limit viral replication and shedding upon exposure to different heterologous genotype of NDV. Developing a strain matched vaccine might less potential to result in better protection by limiting the viral shedding.

Emerging variant of genotype XIII Newcastle disease virus from Northeast India

Northeast India with its rich and diverse avifauna acts as a hotbed for emerging virulent Newcastle disease virus (NDV) strains. The present work describes the molecular and pathogenic characterization of NDV strain isolated from Pandu, Assam, India. Clinicopathological and genetic analysis showed the virulent nature of NDV strain Pandu. On molecular phylogenetic and evolutionary distance analysis, the NDV strain Pandu formed a distinct clade within the genotype XIII of class II NDV, suggesting a new sub-genotype XIIIc. The accumulation of mutations in the NDV strain Pandu makes it divergent enough to be considered as a new sub-genotype. The proposed NDV sub-genotype XIIIc consists of strains recently reported from eastern and northeastern India.

Adenoviral-expressed recombinant granulocyte monocyte colony-stimulating factor (GM-CSF) enhances protective immunity induced by inactivated Newcastle Disease Virus (NDV) vaccine

Although vaccination has been hugely successful in protecting birds against infection by the New castle disease virus (NDV), newly-emerged highly virulent strains have been found to overcome established immune protection and threaten the poultry industry. The need to improve the immunization efficacy is, therefore, urgent. Here, we tested the potential immunostimulatory adjuvant activity of the adenoviral-expressed recombinant chicken granulocyte monocyte colony stimulating factor (rchGM-CSF) in an inactivated Newcastle Disease Virus (NDV) vaccine. 126 commercial layer chicks, divided into six groups, were first vaccinated at day 7, followed by a subsequent boost and later an intramuscular challenge at day 21 and 35 respectively. rchGM-CSF expressed by adenovirus raised NDV-specific hemagglutinin-inhibition (HI) titers from 10 to 12 (log2) and significantly upregulated the production of interferon α/β/γ (IFN-α/β/γ), interleukin-4 (IL-4) and major histocompatibility complex II (MHC-II) in spleens. Crucially, chicks inoculated with the inactivated NDV vaccine plus the rchGM-CSF adjuvant displayed only mild clinical signs, lower tissue viral loads, fewer tissue lesions, and decreased mortality and viral shedding than those in the group immunized with the vaccine alone. Our present work has demonstrated that chicken GM-CSF may act as an enhancer in the orchestration of host immune responses induced by the inactivated NDV vaccine. The molecule, expressed by an adenovirus, has the potential to be used as an immune adjuvant to improve protection by NDV vaccination.

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.

Pathotypic characterization of Newcastle disease virus isolated from vaccinated chicken in West Java, Indonesia

Aim:

This research was conducted to differentiate and characterize eight Newcastle disease virus (NDV) isolates collected from vaccinated chicken at commercial flocks in West Java, Indonesia, in 2011, 2014 and 2015 by pathotype specific primers.

Materials and Methods:

A total of eight NDV isolates collected from clinical outbreaks among commercial vaccinated flocks in West Java, Indonesia, in 2011, 2014, and 2015 were used in this study. Reverse transcription-polymerase chain reaction was used to detect and differentiate virulence of NDV strains, using three sets of primers targeting their M and F gene. First primers were universal primers to detect NDV targeting matrix (M) gene. Other two sets of primers were specific for the fusion (F) gene cleavage site sequence of virulent and avirulent NDV strains.

Results:

Our results showed that three isolates belong to NDV virulent strains, and other five isolates belong to NDV avirulent strains. The nucleotide sequence of the F protein cleavage site showed ¹¹²K/R-R-Q/R-K-R/G-F¹¹⁷ on NDV virulent strains and ¹¹²G-K/R-Q-G-R-L¹¹⁷ on NDV avirulent strain.

Conclusion:

Result from the current study suggested that NDV virulent strain were circulating among vaccinated chickens in West Java, Indonesia; this might possess a risk of causing ND outbreaks and causing economic losses within the poultry industry.

Detection of Inter-Lineage Natural Recombination in Avian Paramyxovirus Serotype 1 Using Simplified Deep Sequencing Platform

Newcastle disease virus (NDV) is a prototype member of avian paramyxovirus serotype 1 (APMV-1), which causes severe and contagious disease in the commercial poultry and wild birds. Despite extensive vaccination programs and other control measures, the disease remains endemic around the globe especially in Asia, Africa, and the Middle East. Being a single serotype, genotype II based vaccines remained most acceptable means of immunization. However, the evidence is emerging on failures of vaccines mainly due to evolving nature of the virus and higher genetic gaps between vaccine and field strains of APMV-1. Most of the epidemiological and genetic characterizations of APMVs are based on conventional methods, which are prone to mask the diverse population of viruses in complex samples. In this study, we report the application of a simple, robust, and less resource-demanding methodology for the whole genome sequencing of NDV, using next-generation sequencing (NGS) on the Illumina MiSeq platform. Using this platform, we sequenced full genomes of five virulent Malaysian NDV strains collected during 2004–2013. All isolates clustered within highly prevalent lineage 5 (specifically in lineage 5a); however, a significantly greater genetic divergence was observed in isolates collected from 2004 to 2011. Interestingly, genetic characterization of one isolate collected in 2013 (IBS025/13) shown natural recombination between lineage 2 and lineage 5. In the event of recombination, the isolate (IBS025/13) carried nucleocapsid protein consist of 55–1801 nucleotides (nts) and near-complete phosphoprotein (1804–3254 nts) genes of lineage 2 whereas surface glycoproteins (fusion, hemagglutinin-neuraminidase) and large polymerase of lineage 5. Additionally, the recombinant virus has a genome size of 15,186 nts which is characteristics for the old genotypes I–IV isolated from 1930 to 1960. Taken together, we report the occurrence of a natural recombination in circulating strains of NDV in commercial poultry using NGS methodology. These findings will not only highlight the potential of RNA viruses to evolve but also to consider the application of NGS in revealing the genetic diversity of these viruses in clinical materials. Factors that drive these evolutionary events and subsequent impact of these divergences on clinical outcome of the disease warrant future investigations.

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.

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.

Genetic characterization and phylogeny of pigeon paramyxovirus isolate (PPMV-1) from Pakistan

Background

Knowing the genome characteristics of circulating Newcastle disease viruses [avian paramyxoviruses (APMV-1) and pigeon paramyxoviruses (PPMV-1)] is important to devise appropriate diagnostics and control strategies. APMVs originating from chicken and wildlife in Pakistan are well-elucidated; nevertheless, molecular characterization for the circulating PPMV-1 is largely unknown.

Findings

Here, we have performed fusion (F) and hemagglutinin (HN) gene based characterization of PPMV-1 isolated from an outbreak in a pigeon flock. With F₀ proteolytic cleavage site (₁₁₂RRQKR↓F₁₁₇), characteristic of velogenic/mesogenic serotype, the complete F and HN gene based sequence analysis of the isolate revealed evolutionary relationship to genotype VI. Further analysis of hyper-variable region of F-gene demonstrated clustering of the study isolate with genotype VIb. The deduced residue analysis for both F and HN protein showed a number of substitution mutations in the functional domains distinct from representative strains of each genotype including the vaccine strains; some of them were found exclusive to the study isolate.

Conclusions

Though limited and preliminary data, the findings enhance our knowledge towards circulating strains of PPMVs in Pakistan. Further studies are needed to ascertain its potential for transmission in the wild birds, commercial and backyard poultry and its subsequent shedding into the environment.

Temporal, geographic, and host distribution of avian paramyxovirus 1 (Newcastle disease virus)

Newcastle disease is caused by virulent forms of avian paramyxovirus of serotype 1 (APMV-1) and has global economic importance. The disease reached panzootic proportions within two decades after first being identified in 1926 in the United Kingdom and Indonesia and still remains endemic in many countries across the world. Here we review information on the host, temporal, and geographic distribution of APMV-1 genetic diversity based on the evolutionary systematics of the complete coding region of the fusion gene. Strains of APMV-1 are phylogenetically separated into two classes (class I and class II) and further classified into genotypes based on genetic differences. Class I viruses are genetically less diverse, generally present in wild waterfowl, and are of low virulence. Class II viruses are genetically and phenotypically more diverse, frequently isolated from poultry with occasional spillovers into wild birds, and exhibit a wider range of virulence. Waterfowl, cormorants, and pigeons are natural reservoirs of all APMV-1 pathotypes, except viscerotropic velogenic viruses for which natural reservoirs have not been identified. Genotypes I and II within class II include isolates of high and low virulence, the latter often being used as vaccines. Viruses of genotypes III and IX that emerged decades ago are now isolated rarely, but may be found in domestic and wild birds in China. Containing only virulent viruses and responsible for the majority of recent outbreaks in poultry and wild birds, viruses from genotypes V, VI, and VII, are highly mobile and have been isolated on different continents. Conversely, virulent viruses of genotypes XI (Madagascar), XIII (mainly Southwest Asia), XVI (North America) and XIV, XVII and XVIII (Africa) appear to have a more limited geographic distribution and have been isolated predominantly from poultry.

Genetic diversity of Newcastle disease viruses isolated from domestic poultry species in Eastern China during 2005-2008

Seventy-nine Newcastle disease viruses (NDV) isolated from clinical specimens of different poultry species including chickens, pigeons (Columba livia), geese and ostriches in Eastern China during 2005-2008 were characterized biologically and phylogenetically. The results showed genetic diversity of these viruses: three class I viruses and one genotype I and 12 genotype II viruses of class II circulating in chickens were avirulent; four genotype VIb viruses isolated from pigeons were moderately virulent; and two genotype III viruses and 57 genotype VIId viruses were highly virulent. The three class I viruses were further classified as genotypes 2 and 3. The very high F protein sequence identity of one genotype I virus with strain Queensland V4 and 12 genotype II viruses with strain La Sota indicated that these viruses originated from the two vaccine strains. Two genotype III viruses shared greater than 99% sequence identity with the moderately virulent vaccine strain Mukteswar but exhibited significantly higher virulence, suggesting that they evolved from the vaccine virus and that the Mukteswar vaccine should be banned in China. Fifty-seven of the 63 virulent NDVs in this study belonged to genotype VIId, indicating its predominance in Eastern China. Genotype VIId viruses could be further classified into two subgroups. Four of the five NDVs isolated from pigeons belonged to genotype VIb, indicating its host-specific preference. Both the genotype VIb and VIId NDVs showed low amino acid similarity to the vaccine strains currently used in China, implying the urgent need to develop better vaccines against the most prevalent NDVs in China.

Observation of risk factors, clinical manifestations and genetic characterization of recent Newcastle Disease Virus outbreak in West Malaysia

Background

Newcastle disease virus remains a constant threat in commercial poultry farms despite intensive vaccination programs. Outbreaks attributed to ND can escalate and spread across farms and states contributing to major economic loss in poultry farms.

Results

Phylogenetic analysis in our study showed that eleven of the samples belonged to genotype VIId. All farms were concurrently positive with two immunosuppressive viruses; Infectious Bursal Disease Virus (IBDV) and Marek’s Disease Virus (MDV). Amino acid sequence analysis confirmed that eleven of the samples had sequence motifs for velogenic/mesogenic strains; three were lentogenic.

Conclusion

In conclusion, no new NDV genotype was isolated from the 2011 NDV outbreak. This study suggests that the presence of other immunosuppressive agents such as IBD and MDV could have contributed to the dysfunction of the immune system of the chickens, causing severe NDV outbreaks in 2011. Risk factors related to biosecurity and farm practices appear to have a significant role in the severity of the disease observed in affected farms.

Characterization of emerging Newcastle disease virus isolates in China

Background

Newcastle disease (ND) is a devastating worldwide disease of poultry characterized by increased respiration, circulatory disturbances, hemorrhagic enteritis, and nervous signs. Sequence analysis shows several amino acid residue substitutions at neutralizing epitopes on the F and HN proteins of recent Shaanxi strains. Both Cross protection and cross serum neutralization tests revealed that the traditional vaccine strains were unable to provide full protection for the flocks.

Methods

To better understand the epidemiology of Newcastle disease outbreak, a portion of the F gene and the full-length HN gene were amplified from Shaanxi isolates by reverse transcription-polymerase chain reaction (RT-PCR) and then conducted sequence and phylogenetic analyzes. In pathogenicity analysis, both high intra-cerebral pathogenicity index (ICPI) and mean death time (MDT) tests of chicken embryo were carried out. Furthermore, a cross-protection experiment in which specific-pathogen-free chickens vaccinated with a LaSota vaccine strain were challenged by the recent Shaanxi strain was also performed.

Results

Nine Newcastle disease (ND) virus (NDV) isolates which were recovered from ND outbreaks in chicken flocks in China were genotypically and pathotypically characterized. Amino acid sequence analysis revealed that all the recent Shaanxi-isolated NDVs have ¹¹²R-R-Q-K-R-F¹¹⁷ for the C-terminus of the F2 protein and exhibit high ICPI and MDT of chicken embryos, suggesting that they were all classified as velogenic type of NDVs. Phylogenetic analysis of these isolates showed that they belong to subgenotype VIId that have been implicated in the recent outbreaks in northwestern China. The percentage of amino acid sequence identity of F protein between recent Shaanxi stains and five vaccine strains was in the range of 81.9 %–88.1 %, while the percentage of amino acid sequence identity of HN protein between recent Shaanxi strains and vaccine strains was in the range of 87.4 %–91.2 %. Furthermore, a number of amino acid residue substitutions at neutralizing epitopes on the F and HN proteins of these isolates were observed, which may lead to the change of antibody recognition and neutralization capacity. A cross-protection experiment indicated that specific-pathogen-free chickens vaccinated with a LaSota vaccine strain was not capable of providing full protection for the flocks that were challenged by the recent Shaanxi strain.

Conclusions

Taken together, our findings reveal that recent Shannxi NDVstrains exhibit antigenic variations that could be responsible for recent outbreaks of NDVs in northwestern China.

Genotypic and pathotypic characterization of Newcastle disease virus isolated from racing pigeons in China

A Newcastle disease virus (NDV) isolated from an outbreak in racing pigeons in China was characterized in this study. Complete gene of the NDV isolate was sequenced and phylogenetic analysis. Pathogenicity experiment was carried out in pigeons, chickens, and ducks. Phylogenetic analysis revealed that the strain clustered with the Class II viruses, has highly phylogenetically similar to NDV strains isolated from pigeons in China, but was distant from the viruses prevalence in chickens and vaccine strains used in China. The deduced amino acid sequence of the cleavage site of the fusion (F) protein confirmed that the isolate contained the virulent motif (112)RRQKRF(117) at the cleavage site, but it caused no appearance disease in chickens and ducks. However, the isolate had virulence in pigeons, resulting in severe nervous signs and highly mortality. Pigeons were considered as a potential source of NDV infection and disease for commercial poultry flocks. Therefore, new vaccines to prevent the NDV infection in the pigeon flocks should be developed as soon as possible, and strict biosecurity measures should be taken to reduce the risk of pigeon Newcastle disease outbreaks.

Characterization of two pigeon paramyxovirus type 1 isolates in China

For over three decades, there has been a continuing panzootic caused by a virulent variant avian paramyxovirus type 1 strain, the so-called pigeon paramyxovirus type 1. It is found primarily in racing pigeons, but it has also spread to wild birds and poultry. In this study, two pigeon paramyxovirus type 1 strains, SD12 and BJ13, obtained from diseased pigeons in China, were characterized. Phylogenetic analysis based on complete sequences allowed characterization of both strains as genotype VI, class II. Further phylogenetic analysis of a 374-nucleotide section of the fusion gene showed that SD12 fell into lineage VIbii-d and BJ13 into VIbii-f. The deduced amino acid sequence of the cleavage site of the fusion protein confirmed that both isolates contained the virulent motif (112)K/RRQKR↓F(117) at the cleavage site. Nevertheless, the values of intracerebral pathogenicity indices showed the SD12 isolate to be a velogenic strain and BJ13 isolate to be a mesogenic strain. The SD12 isolate was further investigated via clinical observation, RNA detection, histopathology and viral serology in experimentally infected 3-week-old chickens. It showed a mild pathological phenotype in chickens, with viral replication restricted to a few tissues. The molecular mechanism for the SD12 isolate to have a virulent motif but low levels of virulence for chickens requires further study.

Atypical velogenic Newcastle disease in a commercial layer flock in Japan

In 2002, a commercial layer flock in Japan was initially diagnosed as being infected with infectious bronchitis (IB) based on clinical signs, virus isolation, and serological analysis but was later found to be atypically infected with velogenic Newcastle disease virus (NDV) following molecular diagnosis. The flock had slightly decreased egg production and an increased occurrence of soft-shelled eggs without significant mortality. IB-like viruses were isolated, which caused dwarfing and curling in 12-day-old chicken embryos. Ten years after this case, retrospective genetic analyses showed that apart from IB virus (IBV), the flock was also infected with NDV. Mean death time (MDT), intracerebral pathogenicity index (ICPI), and deduced amino acid sequence of the cleavage site of the fusion (F)-protein gene revealed that the NDV isolate was velogenic ((112)RRQKR(116)). These results indicate that poultry clinicians should look out for atypical velogenic ND, especially in vaccinated commercial chicken flocks, which may harbor hidden NDV infection.

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

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

Identification of new sub-genotypes of virulent Newcastle disease virus with potential panzootic features

Virulent Newcastle disease virus (NDV) isolates from new sub-genotypes within genotype VII are rapidly spreading through Asia and the Middle East causing outbreaks of Newcastle disease (ND) characterized by significant illness and mortality in poultry, suggesting the existence of a fifth panzootic. These viruses, which belong to the new sub-genotypes VIIh and VIIi, have epizootic characteristics and do not appear to have originated directly from other genotype VII NDV isolates that are currently circulating elsewhere, but are related to the present and past Indonesian NDV viruses isolated from wild birds since the 80s. Viruses from sub-genotype VIIh were isolated in Indonesia (2009-2010), Malaysia (2011), China (2011), and Cambodia (2011-2012) and are closely related to the Indonesian NDV isolated in 2007, APMV1/Chicken/Karangasem, Indonesia (Bali-01)/2007. Since 2011 and during 2012 highly related NDV isolates from sub-genotype VIIi have been isolated from poultry production facilities and occasionally from pet birds, throughout Indonesia, Pakistan and Israel. In Pakistan, the viruses of sub-genotype VIIi have replaced NDV isolates of genotype XIII, which were commonly isolated in 2009-2011, and they have become the predominant sub-genotype causing ND outbreaks since 2012. In a similar fashion, the numbers of viruses of sub-genotype VIIi isolated in Israel increased in 2012, and isolates from this sub-genotype are now found more frequently than viruses from the previously predominant sub-genotypes VIId and VIIb, from 2009 to 2012. All NDV isolates of sub-genotype VIIi are approximately 99% identical to each other and are more closely related to Indonesian viruses isolated from 1983 through 1990 than to those of genotype VII, still circulating in the region. Similarly, in addition to the Pakistani NDV isolates of the original genotype XIII (now called sub-genotype XIIIa), there is an additional sub-genotype (XIIIb) that was initially detected in India and Iran. This sub-genotype also appears to have as an ancestor a NDV strain from an Indian cockatoo isolated in 1982. These data suggest the existence of a new panzootic composed of viruses of subgenotype VIIi and support our previous findings of co-evolution of multiple virulent NDV genotypes in unknown reservoirs, e.g. as recorded with the virulent NDV identified in Dominican Republic in 2008. The co-evolution of at least three different sub-genotypes reported here and the apparent close relationship of some of those genotypes from ND viruses isolated from wild birds, suggests that identifying wild life reservoirs may help predict new panzootics.

Phylogenetic relationships and pathogenicity variation of two Newcastle disease viruses isolated from domestic ducks in Southern China

BACKGROUND

Newcastle disease (ND) is an OIE listed disease caused by virulent avian paramyxovirus type 1 (APMV-1) strains, which is enzootic and causes large economic losses in the poultry sector. Genotype VII and genotype IX NDV viruses were the predominant circulating genotype in China, which may possibly be responsible for disease outbreaks in chicken flocks in recent years. While ducks and geese usually have exhibited inapparent infections.

METHODS

In the present study, we investigate the complete genome sequence, the clinicopathological characterization and transmission of two virulent Newcastle disease viruses, SS-10 and NH-10, isolated from domestic ducks in Southern China in 2010.

RESULTS

F, and the complete gene sequences based on phylogenetic analysis demonstrated that SS-10 (genotype VII) and NH-10 (genotype IX) belongs to class II. The deduced amino acid sequence was (112)R-R-Q-K/R-R-F(117) at the fusion protein cleavage site. Animal experiment results showed that the SS-10 virus isolated from ducks was highly pathogenic for chickens and geese, but low pathogenic for ducks. It could be detected from spleen, lung, kidney, trachea, small intestine, bursa of fabricius, thymus, pancreas and cecal tonsils, oropharyngeal and cloacal swabs, and could transmit to the naive contact birds. Moreover, it could transmit to chickens, ducks and geese by naive contact. However, the NH-10 virus isolated from ducks could infect some chickens, ducks and geese, but only caused chickens to die. Additionally, it could transmit to the naive contact chickens, ducks, and geese.

CONCLUSION

The two NDV isolates exhibited different biological properties with respect to pathogenicity and transmission in chickens, ducks and geese. Therefore, no species-preference exists for chicken, duck or goose viruses and more attention should be paid to the trans-species transmission of VII NDVs between ducks, geese and chickens for the control and eradication of ND.

Molecular and phylogenetic characterization based on the complete genome of a virulent pathotype of Newcastle disease virus isolated in the 1970s in Brazil

Newcastle disease (ND) is caused by the avian paramyxovirus type 1 (APMV-1) or Newcastle disease virus (NDV) that comprises a diverse group of viruses with a single-stranded, negative-sense RNA genome. ND is one of the most important diseases of chickens, because it severely affects poultry production worldwide. In the 1970s, outbreaks of virulent ND were recorded in Brazil, and the strain APMV-1/Chicken/Brazil/SJM/75 (SJM) of NDV was isolated. This strain was characterized as highly pathogenic for chickens but not pathogenic for other bird species. Here we present the complete genome of NDV strain SJM and investigate the phylogenetic relationships of this virus with other NDV strains in terms of genome and proteins composition, as well as characterizing its evolution process. The NDV strain SJM is categorized as a velogenic virus and the complete genome is 15,192 nucleotides in length, consisting of six genes in the order 3'-NP-P-M-F-HN-L-5'. The presence of the major pathogenic determinant of NDV strains ((112)R-R-Q-K-R↓F(117)) was identified in the Fusion protein of the NDV strain SJM. In addition, phylogenetic analysis classified the NDV strain SJM as a member of class II, genotype V, and indicates that this virus help us in the understanding of the evolutionary process of strains belonging to this genotype. This study contributes to the growing interest involving the characterization of NDV isolates to improve our current understanding about the epidemiology, surveillance and evolution of the pathogenic strains.

Complete Genome Sequence of a Newcastle Disease Virus from a Coturnix coturnix japonica (Japanese Quail) Covey in India

The genome of a Newcastle disease virus isolated from a Japanese quail in 2003 is reported here. The genome is 15,192 nucleotides (nt) long, as found in the recent genotypes, and grouped as genotype VIIb, with a 6-nt insertion. This is the first report on the sequence of a genotype VII Newcastle disease virus (NDV) from India.

Detection and characterization of Newcastle disease virus in formalin-fixed, paraffin-embedded tissues from commercial broilers in Egypt

Newcastle disease (ND) is highly contagious and causes severe economic losses to the poultry industry due to high morbidity and mortality. In this report, we describe the detection of Newcastle disease virus (NDV) in formalin-fixed tissues from an outbreak of ND on broiler farms in Egypt. The affected birds experienced respiratory and/or nervous signs and a 75% mortality rate. Tissue samples were collected and placed in 10% neutral buffered formalin followed by embedding in paraffin. RNA was extracted from 80-microm formalin-fixed paraffin-embedded tissue blocks and recovered in 60 microl of elution buffer. All samples were negative for influenza virus by real-time reverse-transcription (RT)-PCR but positive for NDV. These flocks were known to have been vaccinated with a live NDV vaccine (LaSota strain). The nucleic acid sequences of the virus detected in this study were similar to those of a velogenic virus at its cleavage site 111GRRQKR*F117 and clustered with class II genogroup VII lineage of NDV, with a nucleotide sequence identity of 94%-99%. Although extraction and amplification of NDV from paraffin-embedded tissues from experimentally infected birds has been reported previously, this study reports on the use of RT-PCR on formalin-fixed tissues from actual field samples.

Field vaccinated chickens with low antibody titres show equally insufficient protection against matching and non-matching genotypes of virulent Newcastle disease virus

Newcastle disease (ND) is a severe threat to the poultry industry and is caused by virulent strains of Newcastle disease virus (NDV). Many countries maintain a vaccination policy, but NDV is rapidly evolving as shown by the discovery of several new genotypes in the last decades. We tested the efficacy of the currently used classical commercial ND vaccine based on the genotype II strain VG/GA, applied under standard field conditions, against outbreak strains. Field vaccinated broilers were challenged with four different viruses belonging to genotype II, V or VII. A large proportion of field vaccinated broilers showed suboptimal immunity and the protection level against early and recent NDV isolates was dramatically low. Furthermore, there were no significant differences in protection afforded by a genotype II vaccine against a genotype II virus challenge compared to a challenge with viruses belonging to the other genotypes. This study suggests that the susceptibility of vaccinated poultry to NDV infection is not the result of vaccine mismatch, but rather of poor vaccination practices.

Characterization of complete genome sequence of genotype VI and VII velogenic Newcastle disease virus from Japan

The complete genome sequences of three strains of Newcastle disease virus (NDV) isolated from vaccinated commercial layer flocks in Japan in the span of three decades were characterized. All strains had genome lengths of 15,192 nucleotides consisting of six genes in the order of 3'-NP-P/V/W-M-F-HN-L-5'. The general genomic characteristics of the Japanese field strains were consistent with previously characterized class II NDV, except for those belonging to early genotypes (genotype I-IV), which lack the six nucleotide insertion at nucleotide positions 1,648-1,653 of the nucleoprotein (NP) gene. Phylogenetic analysis showed that the Japanese strains could be classified into genotypes VIc and VIIe using the complete genome sequence and the complete coding sequence of the fusion (F) gene according to the unified NDV classification system. Characterization of functional domains and neutralizing epitopes of the F and hemagglutinin-neuraminidase (HN) proteins of Japanese field strains revealed a total of 31 amino acid substitutions, as compared to vaccine strains Ishii and B1, which were widely used in Japan. Although virus neutralization (VN) test showed that poor flock immunity due to vaccination failure or partial and non-uniform immunization maybe the major factors involved in the mechanism of breakthrough infection of the Japanese field strains, approximately two to threefold decrease in the VN titers of the field NDV strains possessing a point mutation (E347K or E347G) at the linear epitope of the HN protein was observed, as compared to vaccine strain B1 and field strain 2440/69, which lack the point mutation. This study may be a useful reference in characterizing future ND outbreaks in vaccinated chickens and as a genetic map for future investigations regarding vaccine designs, reverse genetics systems, and development of molecular diagnostic tools to prevent future ND outbreaks in vaccinated poultry flocks.

Molecular epidemiology of Newcastle disease virus isolates from vaccinated commercial poultry farms in non-epidemic areas of Japan

Background

Newcastle Disease (ND) is a highly contagious and economically devastating disease of poultry. At present, limited molecular epidemiological data are available regarding the causes of ND outbreaks in vaccinated commercial poultry farms. Knowing the genomic characteristics of Newcastle disease virus (NDV) infecting commercial poultry operations in spite of vaccination might give important insights on the infection dynamics of these viruses. In addition, molecular analyses at the subgenotype level and studies on the relationship of Japanese NDVs with other isolates from around the world are lacking. Therefore, in the present study, a molecular epidemiological investigation was conducted to characterize nine NDVs isolated from vaccinated commercial poultry flocks in five different Prefectures in non-epidemic areas of Japan between 1969 and 2002.

Methods

Nucleotide sequencing and phylogenetic studies were performed to characterize the complete fusion (F)-protein gene, 3-prime end of the nucleoprotein (NP)-gene and 5-prime end of the RNA dependent RNA polymerase (L)-gene. Sequence data were compared with 180 NDV strains from GenBank representing different NDV genotypes and subgenotypes from different regions of the world at different time periods. Deduced amino acids were analyzed for homologies, recombination and mutation. Recombination events were estimated using Recombination Detection Program (RDP) version 3.44. Phylogenetic trees were constructed to determine evolutionary relationships among strains.

Results

Mean death time (MDT: 48-56 hr), Intracerebral Pathogenicity Index (ICPI: 1.7-1.9) and deduced amino acid sequences of the F0 proteolytic cleavage site (¹¹²RRQKR¹¹⁶) revealed that all nine field isolates were velogenic. Phylogenetic analysis showed that these isolates could be classified into two genetic lineages and three sublineages namely genotypes VIa (lineage 4a), VId (lineage 4d) and VIId (lineage 5d). No recombination events were observed but a point mutation in one of the neutralizing epitope of the F-protein was identified in the field isolates from Japan.

Conclusions

All field isolates from vaccinated commercial poultry in non-epidemic areas of Japan were part of much bigger outbreaks in provinces and regions and, in some cases, continents. In general, four ND panzootics occurred in Japan and that these outbreaks were mostly characterized by co-circulation of genetically distinct virus lineages due to involvements of infected wild birds. The point mutation identified in the field isolates from Japan may be due to escape from vaccine pressure. The identification of such mutation may be useful for future site-directed mutagenesis to understand the dynamics of NDV infection in vaccinated chickens.

New avian paramyxoviruses type I strains identified in Africa provide new outcomes for phylogeny reconstruction and genotype classification

Newcastle disease (ND) is one of the most lethal diseases of poultry worldwide. It is caused by an avian paramyxovirus 1 that has high genomic diversity. In the framework of an international surveillance program launched in 2007, several thousand samples from domestic and wild birds in Africa were collected and analyzed. ND viruses (NDV) were detected and isolated in apparently healthy fowls and wild birds. However, two thirds of the isolates collected in this study were classified as virulent strains of NDV based on the molecular analysis of the fusion protein and experimental in vivo challenges with two representative isolates. Phylogenetic analysis based on the F and HN genes showed that isolates recovered from poultry in Mali and Ethiopia form new groups, herein proposed as genotypes XIV and sub-genotype VIf with reference to the new nomenclature described by Diel's group. In Madagascar, the circulation of NDV strains of genotype XI, originally reported elsewhere, is also confirmed. Full genome sequencing of five African isolates was generated and an extensive phylogeny reconstruction was carried out based on the nucleotide sequences. The evolutionary distances between groups and the specific amino acid signatures of each cluster allowed us to refine the genotype nomenclature.