Complete genome sequence and molecular characterization of thermostable Newcastle disease virus strain TS09-C

Spray vaccination with a Newcastle disease virus (NDV)-vectored infectious laryngotracheitis (ILT) vaccine protects commercial chickens from ILT in the presence of maternally-derived antibodies

Infectious laryngotracheitis (ILT) poses a significant threat to the poultry industry, and vaccines play an important role in protection. However, due to the increasing scale of poultry production, there is an urgent need to develop vaccines that are suitable for convenient immunization methods such as spraying. Previous studies have shown that Newcastle disease virus (NDV)-ILT vaccines administered via intranasal and intraocular routes to commercial chickens carrying maternally-derived antibodies (MDAs) are still protective against ILT. In this study, a recombinant NDV (rNDV) was generated to express infectious laryngotracheitis virus (ILTV) glycoprotein B (gB), named rLS-gB, based on a full-length cDNA clone of the LaSota strain. The protective effect of different doses of rLS-gB administered by spray vaccination to commercial chickens at 1 d of age (doa) was evaluated. The chickens were exposed to 160-μm aerosol particles for 10 min for spray vaccination, and no adverse reactions were observed after vaccination. Despite the presence of anti-NDV MDAs and anti-ILTV MDAs in chickens, the ILTV- and NDV-specific antibody titres were significantly greater in the vaccinated groups than in the unvaccinated group. After challenge with a virulent ILTV strain, no clinical signs were observed in the 107 EID50/ml group compared to the other groups. Furthermore, vaccination with 107 EID50/ml rLS-gB significantly reduced the ILTV viral load and ameliorated gross and microscopic lesions in the trachea of chickens. Overall, these results suggested that rLS-gB is a safe and efficient candidate spray vaccine for ILT and is especially suitable for scaled chicken farms.

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.

C-terminal truncation of the hemagglutinin-neuraminidase (HN) protein enhances the virulence and immunogenicity of Newcastle disease virus (NDV) vaccine strain V4

The hemagglutinin-neuraminidase (HN) protein of Newcastle disease virus (NDV) is a multifunctional protein with receptor recognition ability that plays an important role in the infection of cells by NDV. An alignment of NDV HN protein sequences of different genotypes showed that vaccine strains of NDV, such as the LaSota strain, generally have an HN protein of 577 amino acids. In comparison, the HN protein of the V4 strain has 616 amino acids, with 39 more amino acids at the C-terminus. In this study, we generated a recombinant NDV (rNDV) with a 39-amino-acid truncation at the HN C-terminus based on the full-length cDNA clone of the V4 strain. This rNDV, named rV4-HN-tr, displayed thermostability similar to that of the parental V4 strain. However, growth kinetics and pathogenicity analysis suggested that rV4-HN-tr is more virulent than the V4 strain. Notably, the C-terminus of HN affected the ability of the virus to adsorb onto cells. Structural predictions further suggested that the C-terminus of HN may obstruct the sialic acid binding site. Immunization of chickens with rV4-HN-tr induced a 3.5-fold higher level of NDV-specific antibodies than that obtained with the V4 strain and provided 100% immune protection against NDV challenge. Our study suggests that rV4-HN-tr is a thermostable, safe, and highly efficient vaccine candidate against Newcastle disease.

Characterization of a Recombinant Thermostable Newcastle Disease Virus (NDV) Expressing Glycoprotein gB of Infectious Laryngotracheitis Virus (ILTV) Protects Chickens against ILTV Challenge

Infectious laryngotracheitis (ILT) and Newcastle disease (ND) are two important avian diseases that have caused huge economic losses to the poultry industry worldwide. Newcastle disease virus (NDV) has been used as a vector in the development of vaccines and gene delivery. In the present study, we generated a thermostable recombinant NDV (rNDV) expressing the glycoprotein gB (gB) of infectious laryngotracheitis virus (ITLV) based on the full-length cDNA clone of the thermostable TS09-C strain. This thermostable rNDV, named rTS-gB, displayed similar thermostability, growth kinetics, and pathogenicity compared with the parental TS09-C virus. The immunization data showed that rTS-gB induced effective ILTV- and NDV-specific antibody responses and conferred immunization protection against ILTV challenge in chickens. The efficacy of rTS-gB in alleviating clinical signs was similar to that of the commercial attenuated ILTV K317 strain. Furthermore, rTS-gB could significantly reduce viral shedding in cloacal and tracheal samples. Our study suggested that the rNDV strain rTS-gB is a thermostable, safe, and highly efficient vaccine candidate against ILT and ND.

Quantitative regulation of the thermal stability of enveloped virus vaccines by surface charge engineering to prevent the self-aggregation of attachment glycoproteins

The development of thermostable vaccines can relieve the bottleneck of existing vaccines caused by thermal instability and subsequent poor efficacy, which is one of the predominant reasons for the millions of deaths caused by vaccine-preventable diseases. Research into the mechanism of viral thermostability may provide strategies for developing thermostable vaccines. Using Newcastle disease virus (NDV) as model, we identified the negative surface charge of attachment glycoprotein as a novel determinant of viral thermostability. It prevented the temperature-induced aggregation of glycoprotein and subsequent detachment from virion surface. Then structural stability of virion surface was improved and virus could bind to and infect cells efficiently after heat-treatment. Employing the approach of surface charge engineering, thermal stability of NDV and influenza A virus (IAV) vaccines was successfully improved. The increase in the level of vaccine thermal stability was determined by the value-added in the negative surface charge of the attachment glycoprotein. The engineered live and inactivated vaccines could be used efficiently after storage at 37°C for at least 10 and 60 days, respectively. Thus, our results revealed a novel surface-charge-mediated link between HN protein and NDV thermostability, which could be used to design thermal stable NDV and IAV vaccines rationally.

Fusion Protein Cleavage Site Containing Three Basic Amino Acids Attenuates Newcastle Disease Virus in Chicken Embryos: Use as an in ovo Vaccine

In ovo vaccination is an attractive immunization strategy for the poultry industry. However, although most live Newcastle disease virus (NDV) vaccine strains, such as LaSota and V4, can be used after hatching, they are pathogenic to chicken embryos when administered in ovo. We have previously reported that NDV strain TS09-C is a safe in ovo vaccine in specific-pathogen-free and commercial chicken embryos because it is attenuated in chicken embryos. However, the molecular basis of its attenuation is poorly understood. In this study, we firstly evaluated the safety of chimeric NDV strains after exchanging genes between strains TS09-C and LaSota as in ovo vaccines, and demonstrated that the attenuation of NDV in chicken embryos was dependent upon the origin of the fusion (F) protein. Next, by comparing the F protein sequences of TS09-C strain with those of LaSota and V4 strain, the R115 in cleavage site and F379 were found to be unique to TS09-C strain. The mutant viruses were generated by substituting one or two amino acids at position 115 and 379 in the F protein, and their safety as in ovo vaccine was evaluated. Mutation in residue 379 did not affect the viral embryonic pathogenicity. While the mutant virus rTS-2B (R115G mutation based on the backbone of TS09-C strain) with two basic amino acids in F cleavage site, was pathogenic to chicken embryos and similar with rLaSota in its tissue tropism, differing markedly from rTS09-C with three basic amino acids in F cleavage site. Together, these findings indicate that the F protein cleavage site containing three basic amino acids is the crucial determinant of the attenuation of TS09-C in chicken embryos. This study extends our understanding of the pathogenicity of NDV in chicken embryos and should expedite the development of in ovo vaccines against NDV.

Characterization of chicken IFI35 and its antiviral activity against Newcastle disease virus

Interferon-induced protein-35 kDa (IFI35) was an antiviral protein induced by interferon (IFN)-γ, which plays an important role in the IFN-mediated antiviral signaling pathway. Here, we cloned and identified IFI35 in the chicken for the first time. Chicken IFI35 (chIFI35) contains an open reading frame (ORF) of 1,152 bp encoding a protein of 384 amino acids containing two conserved Nmi/IFI35 domain (NID) motifs. Tissue distribution analysis of chIFI35 in healthy and Newcastle disease (ND) virus-infected chickens indicated a positive correlation between chIFI35 mRNA transcription and ND viral loads in various tissues. The role of chIFI35 in regulation NDV replication were further assessed by up- or down-regulated chIFI35 expression in DF-1 cells transfected with plasmid harboring chIFI35, pCMV-3HA-chIFI35 or shRNA targeting chIFI35, pshRNA-chIFI35 plasmids. NDV replications in DF-1 cells were significantly reduced or slightly increased by over- or under-expression of the chIFI35 protein, respectively, indicating the role of chIFI35 in anti-NDV infection. Moreover, chIFI35 also involved in regulation of viral gene transcription and IFNs expression. The collected data were meaningful for research of chicken antiviral immunity and shed light on the pleiotropic antiviral effect of chIFI35 during NDV infection.

Vaccine Quality Is a Key Factor to Determine Thermal Stability of Commercial Newcastle Disease (ND)Vaccines

Vaccination against Newcastle disease (ND), a devastating viral disease of chickens, is often hampered by thermal inactivation of the live vaccines, in particular in tropical and hot climate conditions. In the past, “thermostable” vaccine strains (I-2) were proposed to overcome this problem but previous comparative studies did not include formulation-specific factors of commercial vaccines. In the current study, we aimed to verify the superior thermal stability of commercially formulated I-2 strains by comparing six commercially available ND vaccines. Subjected to 37 °C as lyophilized preparations, two vaccines containing I-2 strains were more sensitive to inactivation than a third I-2 vaccine or compared to three other vaccines based on different ND strains. However, reconstitution strains proved to have a comparable tenacity. Interestingly, all vaccines still retained a sufficient virus dose for protection (10⁶ EID₅₀) after 1 day at 37 °C. These results suggest that there are specific factors that influence thermal stability beyond the strain-specific characteristics. Exposing ND vaccines to elevated temperatures of 51 and 61 °C demonstrated that inactivation of all dissolved vaccines including I-2 vaccine strains occurred within 2 to 4 h. The results revealed important differences among the vaccines and emphasize the importance of the quality of a certain vaccine preparation rather than the strain it contains. These data highlight that regardless of the ND strain used for vaccine preparation, the appropriate cold chain is mandatory for keeping live ND vaccines efficiency in hot climates.

Development of a Recombinant Thermostable Newcastle Disease Virus (NDV) Vaccine Express Infectious Bronchitis Virus (IBV) Multiple Epitopes for Protecting against IBV and NDV Challenges

Newcastle disease (ND) and infectious bronchitis (IB) are two highly contagious diseases that severely threaten the poultry industry. The goal of this study is to prevent these two diseases and reduce the vaccine costs during storage and transportation. In this study, we design a thermostable recombinant Newcastle disease virus (NDV) candidate live vaccine strain designated as rLS-T-HN-T/B, which expresses the multiple epitope cassette of the identified infectious bronchitis virus (IBV) (S-T/B). The rLS-T-HN-T/B strain was found to possess similar growth kinetics, passage stability, morphological characteristics, and virulence to the parental LaSota strain. After incubation at 56 °C at the indicated time points, the rLS-T-HN-T/B strain was determined by the hemagglutination (HA), and 50% embryo infectious dose (EID₅₀) assays demonstrated that it accords with the criteria for thermostability. The thermostable rLS-T-HN-T/B and parental LaSota vaccines were stored at 25 °C for 16 days prior to immunizing the one-day-old specific pathogen-free (SPF) chicks. Three weeks postimmunization, the virus challenge results suggested that the chicks vaccinated with the rLS-T-HN-T/B vaccine were protected by 100% and 90% against a lethal dose of NDV and IBV, respectively. Furthermore, the trachea ciliary activity assay indicated that the mean ciliostasis score of the chicks vaccinated with thermostable rLS-T-HN-T/B vaccine was significantly superior to that of the LaSota and PBS groups (p < 0.05). The rLS-T-HN-T/B vaccine stored at 25 °C for 16 days remained capable of eliciting the immune responses and protecting against IBV and NDV challenges. However, the same storage conditions had a great impact on the parental LaSota strain vaccinated chicks, and the NDV challenge protection ratio was only 20%. We conclude that the thermostable rLS-T-HN-T/B strain is a hopeful bivalent candidate vaccine to control both IB and ND and provides an alternative strategy for the development of cost-effective vaccines for village chickens, especially in the rural areas of developing countries.

Characterization of thermostable Newcastle disease virus recombinants expressing the hemagglutinin of H5N1 avian influenza virus as bivalent vaccine candidates

Newcastle disease virus (NDV) has been used as a vector in the development of vaccines and gene delivery. In the present study, we generated the thermostable recombinant NDV (rNDV) expressing the different forms of hemagglutinin (HA) of highly pathogenic avian influenza virus (HPAIV) H5N1 based on the full-length cDNA clone of thermostable TS09-C strain. The recombinant thermostable Newcastle disease viruses, rTS-HA, rTS-HA1 and rTS-tPAs/HA1, expressed the HA, HA1 or modified HA1 protein with the tissue plasminogen activator signal sequence (tPAs), respectively. The rNDVs displayed similar thermostability, growth kinetics and pathogenicity compared with the parental TS09-C virus. The tPAs facilitated the expression and secretion of HA1 protein in cells infected with rNDV. Animal studies demonstrated that immunization with rNDVs elicited effective H5N1- and NDV-specific antibody responses and conferred immune protection against lethal H5N1 and NDV challenges in chickens and mice. Importantly, vaccination of rTS-tPAs/HA1 resulted in enhanced protective immunity in chickens and mice. Our study thus provides a novel thermostable NDV-vectored vaccine candidate expressing a soluble form of a heterologous viral protein, which will greatly aid the poultry industry in developing countries.

Genome Sequence of a Thermostable Avirulent Newcastle Disease Virus Isolated from Domestic Ducks in China

Newcastle disease virus strain D4 was isolated from healthy ducks in Hubei, China. The D4 isolate has a genome length of 15,186 nucleotides and is classified as genotype I of class II. Thermostability and pathogenicity tests demonstrate that D4 is a thermostable avirulent strain.

Newcastle disease virus strain D4 was isolated from healthy ducks in Hubei, China. The D4 isolate has a genome length of 15,186 nucleotides and is classified as genotype I of class II. Thermostability and pathogenicity tests demonstrate that D4 is a thermostable avirulent strain.

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.

Evaluation of a thermostable Newcastle disease virus strain TS09-C as an in-ovo vaccine for chickens

In-ovo vaccination is an attractive immunization approach for poultry industry. However, most of the Newcastle disease virus (NDV) vaccine strains used after hatch are unsafe, as in-ovo vaccines, due to their high pathogenicity for chicken embryos. In this study, we evaluated the safety and immunogenicity of a thermostable NDV strain TS09-C, derived from V4 strain, as in-ovo vaccine. Chickens in-ovo vaccinated with the parental V4 strain displayed greatly reduced hatchability and severe histopathological lesions in both trachea and intestine tissues, while the hatchability was not affected by in-ovo vaccination withTS09-C strain. The safe dose that infected all chicken embryos without obviously histopathological lesions was 10^3.0 EID₅₀ per bird. In-ovo vaccination of chickens with TS09-C virus conferred complete protection against virulent NDV challenge. Results suggest that the thermostable NDV strain TS09-C is a safe and immunogenic in-ovo vaccine candidate that can be delivered quickly and uniformly, and induce earlier immune response.

Molecular basis for the thermostability of Newcastle disease virus

Thermostable Newcastle disease virus (NDV) vaccines have been used widely to protect village chickens against Newcastle disease, due to their decreased dependence on cold chain for transport and storage. However, the genetic basis underlying the NDV thermostability is poorly understood. In this study, we generated chimeric viruses by exchanging viral genes between the thermostable TS09-C strain and thermolabile LaSota strain using reverse genetics technology. Evaluations of these chimeric NDVs demonstrated that the thermostability of NDV was dependent on the origin of HN protein. Chimeras bearing the HN protein derived from thermostable virus exhibited a thermostable phenotype, and vice versa. Both hemagglutinin and neuraminidase activities of viruses bearing the TS09-C HN protein were more thermostable than those containing LaSota HN protein. Furthermore, the newly developed thermostable virus rLS-T-HN, encoding the TS09-C HN protein in LaSota backbone, induced significantly higher antibody response than the TS09-C virus, and conferred complete protection against virulent NDV challenge. Taken together, the data suggest that the HN protein of NDV is a crucial determinant of thermostability, and the HN gene from a thermostable NDV could be engineered into a thermolabile NDV vaccine strain for developing novel thermostable NDV vaccine.

Genetic characterization and evolutionary analysis of Newcastle disease virus isolated from domestic duck in South Korea

Domestic ducks are considered a potential reservoir of Newcastle disease virus. In the study, a Newcastle disease virus (NDV) isolated from a domestic duck during surveillance in South Korea was characterized. The complete genome of the NDV isolate was sequenced, and the phylogenetic relationship to reference strains was studied. Phylogenetic analysis revealed that the strain clustered in genotype I of Class II ND viruses, has highly phylogenetic similarity to NDV strains isolated from waterfowl in China, but was distant from the viruses isolated in chickens and vaccine strains used in South Korea. Pathogenicity experiment in chickens revealed it to be a lentogenic virus. The deduced amino acid sequence of the cleavage site of the fusion (F) protein confirmed that the isolate contained the avirulent motif (112)GKQGRL(117) at the cleavage site and caused no apparent disease in chickens and ducks. With phylogeographic analysis based on fusion gene, we estimate the origin of an ancestral virus of the isolate and its sister strain located in China around 1998. It highlights the need of continuous surveillance to enhance current understanding of the molecular epidemiology and evolution of the pathogenic strains.