Evaluation of the Newcastle disease virus F and HN proteins in protective immunity by using a recombinant avian paramyxovirus type 3 vector in chickens

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.

Efficiency of NHEJ-CRISPR/Cas9 and Cre-LoxP Engineered Recombinant Turkey Herpesvirus Expressing Pasteurella multocida OmpH Protein for Fowl Cholera Prevention in Ducks

Fowl cholera is caused by the bacterium Pasteurella multocida, a highly transmissible avian ailment with significant global implications, leading to substantial economic repercussions. The control of fowl cholera outbreaks primarily relies on vaccination using traditional vaccines that are still in use today despite their many limitations. In this research, we describe the development of a genetically engineered herpesvirus of turkeys (HVT) that carries the OmpH gene from P. multocida integrated into UL 45/46 intergenic region using CRISPR/Cas9-NHEJ and Cre-Lox system editing. The integration and expression of the foreign cassettes were confirmed using polymerase chain reaction (PCR), indirect immunofluorescence assays, and Western blot assays. The novel recombinant virus (rHVT-OmpH) demonstrated stable integration of the OmpH gene even after 15 consecutive in vitro passages, along with similar in vitro growth kinetics as the parent HVT virus. The protective efficacy of the rHVT-OmpH vaccine was evaluated in vaccinated ducks by examining the levels of P. multocida OmpH-specific antibodies in serum samples using ELISA. Groups of ducks that received the rHVT-OmpH vaccine or the rOmpH protein with Montanide™ (SEPPIC, Paris, France) adjuvant exhibited high levels of antibodies, in contrast to the negative control groups that received the parental HVT or PBS. The recombinant rHVT-OmpH vaccine also provided complete protection against exposure to virulent P. multocida X-73 seven days post-vaccination. This outcome not only demonstrates that the HVT vector possesses many characteristics of an ideal recombinant viral vaccine vector for protecting non-chicken hosts, such as ducks, but also represents significant research progress in identifying a modern, effective vaccine candidate for combatting ancient infectious diseases.

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.

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.

Construction of Novel Thermostable Chimeric Vaccine Candidates for Genotype VII Newcastle Disease Virus

Genotype VII Newcastle Disease Virus (NDV) has caused a pandemic in many countries and usually causes fatal consequences in infected chickens. Although current commercial attenuated NDV vaccines can provide an ideal protection against genotype VII NDV, they cannot completely prevent the infection and viral shedding, and the genotype of some vaccine strains cannot match with the prevalent strain. In this study, in order to construct a thermostable and genotype VII-matched live attenuated vaccine, we used a thermostable genotype VIII virulent HR09 strain as the backbone and replaced its F gene with that of the genotype VII DT-2014 strain. Meanwhile, the cleavage site of F gene of DT-2014 was mutated to that of class I F protein and avirulent class II F protein, respectively. The results showed that the two chimeric viruses, designated rcHR09-CI and rcHR09-CII, shared a similar growth kinetics and thermostability with their parental HR09 strain. Mean death time (MDT) and intracerebral pathogenicity index (ICPI) tests showed that the two chimeric viruses were highly attenuated. Though both chimeric NDVs and La Sota vaccine strain could provide complete protection to immunized chickens against the challenge of virulent genotype VII ZJ1 strain, the two chimeric NDVs could induce a higher level of antibody response against ZJ1 strain and could significantly reduce the viral shedding compared with La Sota vaccine strain. In conclusion, our study constructed two chimeric thermostable genotype VII-matched NDV vaccine candidates, which provided complete protection against the challenge of virulent genotype VII NDV.

Assessing the Efficacy of Recombinant Newcastle Disease Virus Vaccines (Double-Insert vHVT-IBD-ND and Single-Insert vHVT-ND) Followed by a Vaccination with a Live Newcastle Disease Vaccine Against a Moroccan Velogenic Newcastle Disease Challenge in Commercial Broilers

The advent of turkey herpesvirus (HVT) vector vaccine technology (vHVT) has made a huge improvement in the prevention and control of several poultry diseases. The objective of this study was to compare, under experimental conditions, the protection conferred by different vaccination programs based on an HVT double-insert (infectious bursal disease {IBD] and Newcastle disease [ND]) vector vaccine (vHVT-IBD-ND) and an HVT single-insert (vHVT-ND) vector vaccine followed by a vaccination with a live ND vaccine at Day 1 only or at Days 1 and 14. Commercial broilers were vaccinated by the recombinant ND virus vaccines subcutaneously at 1 day old, in the hatchery, and challenged at 30 days of age using the Moroccan ND virus velogenic viscerotropic JEL strain. The results showed that the tested vaccine induced 95% to 100% clinical protection against mortality and clinical signs. The humoral immune response to vaccination was detected from 3 wk of age using enzyme-linked immunosorbent assay and hemagglutination inhibition tests. ND challenge virus shedding was significantly reduced in the vaccinated birds as compared to controls. Significant reduction of the cloacal shedding suggests that the vHVT-IBD-ND vaccine stimulates actively the immunity against the tested ND challenge virus. No significant differences were found between the vaccination programs based on vHVT-IBD-ND or on vHVT-ND.

Plant-Derived Recombinant Vaccines against Zoonotic Viruses

Emerging and re-emerging zoonotic diseases cause serious illness with billions of cases, and millions of deaths. The most effective way to restrict the spread of zoonotic viruses among humans and animals and prevent disease is vaccination. Recombinant proteins produced in plants offer an alternative approach for the development of safe, effective, inexpensive candidate vaccines. Current strategies are focused on the production of highly immunogenic structural proteins, which mimic the organizations of the native virion but lack the viral genetic material. These include chimeric viral peptides, subunit virus proteins, and virus-like particles (VLPs). The latter, with their ability to self-assemble and thus resemble the form of virus particles, are gaining traction among plant-based candidate vaccines against many infectious diseases. In this review, we summarized the main zoonotic diseases and followed the progress in using plant expression systems for the production of recombinant proteins and VLPs used in the development of plant-based vaccines against zoonotic viruses.

Review of Poultry Recombinant Vector Vaccines

The control of poultry diseases has relied heavily on the use of many live and inactivated vaccines. However, over the last 30 yr, recombinant DNA technology has been used to generate many novel poultry vaccines. Fowlpox virus and turkey herpesvirus are the two main vectors currently used to construct recombinant vaccines for poultry. With the use of these two vectors, more than 15 recombinant viral vector vaccines against Newcastle disease, infectious laryngotracheitis, infectious bursal disease, avian influenza, and Mycoplasma gallisepticum have been developed and are commercially available. This review focuses on current knowledge about the safety and efficacy of recombinant viral vectored vaccines and the mechanisms by which they facilitate the control of multiple diseases. Additionally, the development of new recombinant vaccines with novel vectors will be briefly discussed.

The construction of recombinant Lactobacillus casei expressing hemagglutinin-neuraminidase protein and its immune response in chickens

Newcastle disease virus (NDV) is one of the most important diseases in poultry. The present study generated recombinant surface-displayed Lactobacillus casei (L. casei) expressing the hemagglutinin-neuraminidase (HN) of NDV (Lc-pPG-HN) and a live pPG vector (Lc-pPG) and evaluated their immunogenicity. A 1670 bp HN gene fragment was successfully amplified and cloned into a prokaryotic protein expression system. Protein expression in the resulting recombinant Lc-pPG-HN (surface displayed) strain was verified using Western blotting and indirect immunofluorescence. A single band was observed on the Western blots, and the molecular weight of the corresponding protein was 63 kDa. A fluorescent signal for Lc-pPG-HN was observed using fluorescence microscopy. A total of 270 healthy chicks were divided into three treatment groups. Five replicates were used for each treatment, while six chicks were used per replicate. The following three treatment groups were used: physiological saline group (Control), Lc-pPG group and recombinant vaccine group (Lc-pPG-HN). The primary immunization and booster immunization of the chicks were performed via oral administration on 1 and 10 days old. Tissue and blood samples were collected from chickens that received oral recombinant L. casei strains on 1, 7, 14 and 21 days post-immunization for immune-related index analyses. Chickens orally immunized with Lc-pPG-HN showed significantly increased body weights and immune organ indices. Oral immunization with Lc-pPG-HN also enhanced the concentrations of serum interleukin-2 (IL-2), interferon-γ (IFN-γ), intestinal lavage fluid secretory immunoglobulin A (SIgA) and histomorphological development of the small intestine. Our results also indicated that recombinant L. casei significantly increased Lactobacillus and Bifidobacterium colonization and decreased the relative abundance of Escherichia coli (E. coli) in the chicken caecum. Similar enhancement effects from hemagglutination inhibition were also observed in the antibody titers. Oral administration of Lc-pPG-HN effectively protected against NDV and alleviated the symptoms of the NDV challenge. In summary, recombinant L. casei had positive impacts on the performance, immunological function, gut development, and microbiota of growing chicks and may be a potential therapeutic candidate against NDV.

Multi-epitope peptide vaccine prediction against Newcastle disease virus using immuno-informatics approaches

Newcastle disease is one of the most critical disease in poultry and wild birds, largely due to its high morbidity and mortality, as well as its worldwide distribution and threat of considerable economic losses to avian industries caused by Newcastle disease virus (NDV). The NDV can cause clinical signs varying from subclinical infections to 100% mortality, depending on the susceptibility of the host and the virulence of the virus. The virus is classified into velogenic (viscerotropic velogenic and neurotropic velogenic), mesogenic and lentogenic. The objectives of this study was to design a peptide vaccine using immunoinformatics approaches. In total, 12 NDV fusion proteins retrieved from NCBI database were aligned to determine the conservancy and candidate epitopes were analysed by predictions tools from Immune Epitope Database. Then the 3D structure of the conserved region was modelled using the Swiss Model and aligned using PyMol software. Two epitopes were predicted as a peptide vaccine for B cell (DKAVNVYTSSQT and NMPKDKEACAKAPLEA). This is a preliminary study of designing an epitope-based peptide vaccine against NDV, and we recommend further study to identify the interaction between these peptides with T cells and antibodies.

Construction and immune protection evaluation of recombinant virus expressing Newcastle disease virus F protein by the largest intergenic region of fowlpox virus NX10

Fowlpox virus (FPV) is used as a vaccine vector to prevent diseases in poultry and mammals. The insertion site is considered as one of the main factors influencing foreign gene expression. Therefore, the identification of insertion sites that can stably and efficiently express foreign genes is crucial for the construction of recombinant vaccines. In this study, we found that the insertion of foreign genes into ORF054 and the ORF161/ORF162 intergenic region of the FPV genome did not affect replication, and that the foreign genes inserted into the intergenic region were more efficiently expressed than when they were inserted into a gene. Based on these results, the recombinant virus rFPVNX10-NDV F-E was constructed and immune protection against virulent FPV and Newcastle disease virus (NDV) was evaluated. Tests for anti-FPV antibodies in the vaccinated chickens were positive within 14 days post-vaccination. After challenge with FPV102, no clinical signs of FP were observed in vaccinated chickens, as compared to that in the control group (unvaccinated), which showed 100% morbidity. Low levels of NDV-specific neutralizing antibodies were detected in vaccinated chickens before challenge. After challenge with NDV ck/CH/LHLJ/01/06, all control chickens died within 4 days post-challenge, whereas 5/15 vaccinated chickens died between 4 and 12 days post-challenge. Vaccination provided an immune protection rate of 66.7%, whereas the control group showed 100% mortality. These results indicate that the ORF161/ORF162 intergenic region of FPVNX10 can be used as a recombination site for foreign gene expression in vivo and in vitro.

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.

A Plant-Produced Recombinant Fusion Protein-Based Newcastle Disease Subunit Vaccine and Rapid Differential Diagnosis Platform

Newcastle disease (ND) is a highly contagious avian disease, causing considerable economic losses to the poultry industry. To obtain a safe, inexpensive, and effective ND vaccine to meet the international trade requirements of differentiating infected from vaccinated animals (DIVA), here we report the production of Oryza sativa recombinant fusion (F) protein in stably transformed transgenic rice seeds via agroinfiltration. The F protein expression level was enhanced 3.6-fold with a genetic background in low glutelin. Inoculation of plant-produced F antigen into Specific Pathogen Free (SPF) chickens markedly elicited neutralizing antibody responses against homologous and heterologous ND virus strains. Two doses of 4.5 μg fully protected chickens from a lethal ND challenge without any clinical symptoms. The mean weight gain of F protein-immunized chickens within 15 days after challenge was significantly higher than that of traditional whole virus vaccine-immunized chickens, thereby obtaining higher economic benefits. Moreover, the sera from the chickens vaccinated with the plant-produced F vaccine did not show reactivity in an immunochromatographic strip targeting the haemagglutinin-neuraminidase protein (HN) protein, and DIVA could be achieved within 10 minutes. Our results demonstrate that the plant-derived F vaccine along with immunochromatographic strips could be useful in the implementation of an NDV eradication program.

A recombinant avian paramyxovirus serotype 3 expressing the hemagglutinin protein protects chickens against H5N1 highly pathogenic avian influenza virus challenge

Highly pathogenic avian influenza (HPAI) is a devastating disease of poultry and a serious threat to public health. Vaccination with inactivated virus vaccines has been applied for several years as one of the major policies to control highly pathogenic avian influenza virus (HPAIV) infections in chickens. Viral-vectored HA protein vaccines are a desirable alternative for inactivated vaccines. However, each viral vector possesses its own advantages and disadvantages for the development of a HA-based vaccine against HPAIV. Recombinant Newcastle disease virus (rNDV) strain LaSota expressing HA protein vaccine has shown promising results against HPAIV; however, its replication is restricted only to the respiratory tract. Therefore, we thought to evaluate avian paramyxovirus serotype 3 (APMV-3) strain Netherlands as a safe vaccine vector against HPAIV, which has high efficiency replication in a greater range of host organs. In this study, we generated rAPMV-3 expressing the HA protein of H5N1 HPAIV using reverse genetics and evaluated the induction of neutralizing antibodies and protection by rAPMV3 and rNDV expressing the HA protein against HPAIV challenge in chickens. Our results showed that immunization of chickens with rAPMV-3 or rNDV expressing HA protein provided complete protection against HPAIV challenge. However, immunization of chickens with rAPMV-3 expressing HA protein induced higher level of neutralizing antibodies compared to that of rNDV expressing HA protein. These results suggest that a rAPMV-3 expressing HA protein might be a better vaccine for mass-vaccination of commercial chickens in field conditions.

Evaluation of Japanese encephalitis virus E and NS1 proteins immunogenicity using a recombinant Newcastle disease virus in mice

Japanese encephalitis (JE) is the most important cause of acute encephalitis syndrome (AES). Japanese encephalitis virus (JEV), the prototype member of the JE serocomplex, belongs to the genus Flavivirus. The immunogenic proteins envelope (E) and non-structural protein 1 (NS1) of JEV are widely explored for the development of vaccines and diagnostics against JEV. However, there are underlying concerns such as the risk of reversion of live-attenuated vaccines to high virulence, the incomplete inactivation of pathogens in inactivated vaccines and partial vaccine coverage. Newcastle disease virus (NDV) is an efficient viral vaccine vector to express several human and animal immunogenic proteins. In the present study, we have developed a recombinant NDV (rNDV), individually expressing the E and NS1 proteins of JEV (rNDV-Ejev and rNDV-NS1jev). The recovered rNDV-Ejev and rNDV-NS1jev were characterized in 9-day-old SPF embryonated chicken eggs and in cell culture. The vaccination of rNDV-Ejev and rNDV-NS1jev showed effective immunity against JEV upon intranasal immunization in BALB/c mice. The rNDVs vaccination produced effective neutralization antibody titers against both NDV and JEV. The cytokine profiling of the vaccinated mice showed an effective Th1 and Th2 mediated immune response. The study also provided an insight that E, when used in combination with NS1 could reduce the efficacy of only E based immunization in mice. Our results suggested rNDV-Ejev to be a promising live viral vectored vaccine against JEV. This study implies an alternative and economical strategy for the development of a recombinant vaccine against JEV.

Evaluation of surface glycoproteins of classical swine fever virus as immunogens and reagents for serological diagnosis of infections in pigs: a recombinant Newcastle disease virus approach

Classical swine fever (CSF) is an important viral disease of domestic pigs and wild boar. The structural proteins E2 and E^rns of classical swine fever virus (CSFV), which participate in the attachment of the virion to the host cell surface and its subsequent entry, are immunogenic. The E2 and E^rns proteins are used for diagnosis and the development of vaccines against CSFV infection in swine. Newcastle disease virus (NDV) has been successfully used as a viral vector to express heterologous proteins. In the present study, the E2 and E^rns proteins of CSFV were expressed in cell culture as well as embryonated chicken eggs, using recombinant NDV (rNDV). Rescued rNDV expressing the E2 and E^rns proteins induced the production of CSFV-neutralizing antibodies upon intranasal vaccination of pigs. Serum samples from vaccinated animals were found to neutralize both homologous and heterologous CSFV strains. Furthermore, rNDV expressing the E2 and E^rns proteins of CSFV was used to develop an indirect ELISA, which was used to measure the the antibody titers of randomly collected serum samples. The results suggested that the ELISA based on rNDV-expressed E2 and E^rns proteins could be used to screen for CSFV infections. This study shows that rNDV-based expression of CSFV antigens is potentially applicable for development of vaccines and diagnostic tests for CSFV infection. This approach could be an economically favorable alternative to the existing vaccine and diagnostics for CSFV in pigs.

Evaluation of a Recombinant Newcastle Disease Virus Expressing Human IL12 against Human Breast Cancer

The Newcastle disease virus (NDV) strain AF2240 is an avian avulavirus that has been demonstrated to possess oncolytic activity against cancer cells. However, to illicit a greater anti-cancer immune response, it is believed that the incorporation of immunostimulatory genes such as IL12 into a recombinant NDV backbone will enhance its oncolytic effect. In this study, a newly developed recombinant NDV that expresses IL12 (rAF-IL12) was tested for its safety, stability and cytotoxicity. The stability of rAF-IL12 was maintained when passaged in specific pathogen free (SPF) chicken eggs from passage 1 to passage 10; with an HA titer of 2⁹. Based on the results obtained from the MTT cytotoxic assay, rAF-IL12 was determined to be safe as it only induced cytotoxic effects against normal chicken cell lines and human breast cancer cells while sparing normal cells. Significant tumor growth inhibition (52%) was observed in the rAF-IL12-treated mice. The in vivo safety profile of rAF-IL12 was confirmed through histological observation and viral load titer assay. The concentration and presence of the expressed IL12 was quantified and verified via ELISA assay. In summary, rAF-IL12 was proven to be safe, selectively replicating in chicken and cancer cells and was able to maintain its stability throughout several passages; thus enhancing its potential as an anti-breast cancer vaccine.

A Recombinant Turkey Herpesvirus Expressing F and HN Genes of Avian Avulavirus-1 (AAvV-1) Genotype VI Confers Cross-Protection against Challenge with Virulent AAvV-1 Genotypes IV and VII in Chickens

Newcastle disease (ND) is responsible for significant economic losses in the poultry industry. The disease is caused by virulent strains of Avian avulavirus 1 (AAvV-1), a species within the family Paramyxoviridae. We developed a recombinant construct based on the herpesvirus of turkeys (HVT) as a vector expressing two genes: F and HN (HVT-NDV-F-HN) derived from the AAvV-1 genotype VI ("pigeon variant" of AAvV-1). This recombinant viral vaccine candidate was used to subcutaneously immunize one group of specific pathogen-free (SPF) chickens and two groups of broiler chickens (20 one-day-old birds/group). Humoral immune response was evaluated by hemagglutination-inhibition test and enzyme-linked immunosorbent assay (ELISA). The efficacy of the immunization was assessed in two separate challenge studies performed at 6 weeks of age with the use of virulent AAvV-1 strains representing heterologous genotypes IV and VII. The developed vaccine candidate elicited complete protection in SPF chickens since none of the birds became sick or died during the 2-week observation period. In the broiler groups, 90% and 100% clinical protection were achieved after challenges with AAvV-1 of IV and VII genotypes, respectively. We found no obvious relationship between antibody levels and protection assessed in broilers in the challenge study. The developed recombinant HVT-NDV-F-HN construct containing genes from a genotype VI AAvV-1 offers promising results as a potential vaccine candidate against ND in chickens.

A Novel Cre Recombinase-Mediated In Vivo Minicircle DNA (CRIM) Vaccine Provides Partial Protection against Newcastle Disease Virus

Minicircle DNA (mcDNA), which contains only the necessary components for eukaryotic expression and is thus smaller than traditional plasmids, has been designed for application in genetic manipulation. In this study, we constructed a novel plasmid containing both the Cre recombinase under the phosphoglycerate kinase (PGK) promoter and recombinant lox66 and lox71 sites located outside the cytomegalovirus (CMV) expression cassette. The strictly controlled synthesis of Cre recombinase in vivo maintained the complete form of the plasmid in vitro, whereas the in vivo production of Cre transformed the parental plasmid to mcDNA after transfection. The newly designed Cre recombinase-mediated in vivo mcDNA platform, named CRIM, significantly increased the nuclear entry of mcDNA, followed by increased production of mRNA and protein, using enhanced green fluorescent protein (EGFP) as a model. Similar results were also observed in chickens when the vaccine was delivered by the regulated-delayed-lysis Salmonella strain χ11218, where significantly increased production of EGFP was observed in chicken livers. Then, we used the HN gene of genotype VII Newcastle disease virus as an antigen model to construct the traditional plasmid pYL43 and the novel mcDNA plasmid pYL47. After immunization, our CRIM vaccine provided significantly increased protection against challenge compared with that of the traditional plasmid, providing us with a novel mcDNA vaccine platform.IMPORTANCE Minicircle DNA (mcDNA) has been considered an attractive alternative to DNA vaccines; however, the relatively high cost and complicated process of purifying mcDNA dramatically restricts the application of mcDNA in the veterinary field. We designed a novel in vivo mcDNA platform in which the complete plasmid could spontaneously transform into mcDNA in vivo In combination with the regulated-delayed-lysis Salmonella strain, the newly designed mcDNA vaccine provides us with an elegant platform for veterinary vaccine development.

Evaluation of a fusion gene-based DNA prime-protein boost vaccination strategy against Newcastle disease virus

The low potency of genetic immunization has to date impeded development of commercial vaccines against major infectious diseases. The aim of this study was to develop and evaluate a fusion gene-based DNA prime-protein boost vaccination strategy to improve the efficacy of both DNA and subunit vaccines against Newcastle disease virus (NDV). The fusion (F) protein, a viral surface glycoprotein, is responsible for the cell membrane fusion and spread, also is one of the major targets for immune response. In this study, groups of chickens were vaccinated twice intramuscularly at 14-day interval either with plasmid DNA encoding F protein gene of NDV or with recombinant F protein alone or with plasmid DNA and boosted with the recombinant F protein and compared with birds that were vaccinated with live NDV vaccine. The immune response was evaluated by indirect ELISA, lymphocyte transformation test, virus neutralization test, cytokine analysis, immunophenotyping of peripheral blood mononuclear cells, and protective efficacy study against virulent NDV challenge virus infection. Chickens in prime-boost group developed a higher level of humoral and cellular immune responses as compared with those immunized with plasmid or protein alone. The DNA prime-protein boost using F protein of NDV yielded 91.6% protection against virulent NDV challenge infection better than immunization with DNA vaccine (66.6%) or rF protein (83.3%) alone. These findings suggest that the "DNA prime-protein boost" approach using full-length F gene could enhance the immune response against NDV in the chickens.

Recombinant duck enteritis viruses expressing the Newcastle disease virus (NDV) F gene protects chickens from lethal NDV challenge

Newcastle disease virus (NDV) is a major threat to poultry worldwide. Virulent Newcastle disease virus infection can cause 100% morbidity and mortality in chickens. Vaccination is the most effective way to prevent and control NDV outbreaks in poultry. Previously, we demonstrated that a duck enteritis virus (DEV) vaccine strain is a promising vector to generate recombinant vaccines in chickens. Here, we constructed two recombinant DEVs expressing the F protein (rDEV-F) or HN protein (rDEV-HN) of NDV. We then evaluated the protective efficacy of these recombinant DEVs in specific-pathogen-free chickens. rDEV-F induced 100% protection of chickens from lethal NDV challenge after a single dose of 10⁴ TCID₅₀, whereas rDEV-HN did not induce effective protection. rDEV-F may therefore serve as a promising vaccine candidate for chickens. This is the first report of a DEV-vectored vaccine providing robust protection against lethal NDV infection in chickens.

Construction of a novel DNA vaccine candidate targeting F gene of genotype VII Newcastle disease virus and chicken IL-18 delivered by Salmonella

AIMS

Genotype VII Newcastle disease (ND) is one of the most epidemic and serious infectious diseases in the poultry industry. A novel vaccine targeting VII Newcastle disease virus (NDV) is still proving elusive.

METHODS AND RESULTS

In this study, we constructed regulated delayed lysis Salmonella strains expressing either a fusion protein (F) alone under an eukaryotic CMV promoter or together with chicken IL-18 (chIL-18) as a molecular adjuvant under prokaryotic P_trc promoter, named pYL1 and pYL23 respectively. Oral immunization with recombinant strains induced NDV-specific serum IgG antibodies in both pYL1- and pYL23-immunized chickens. The presence of chIL-18 significantly increased lymphocyte proliferation in immunized chickens, as well as the percentages of CD3⁺ CD4⁺ and CD3⁺ CD8⁺ T cells in serum, even if a statistically significant difference did not exist. After a virulent challenge, pYL23 immunization provided about 80% protection at day 10 postinfection, compared with 60% of protection offered by pYL1 immunization and 100% protection in the inactivated vaccine group, indicating the enhanced immune response provided by chIL-18, which was also confirmed by histochemical analysis.

CONCLUSIONS

Recombinant lysis Salmonella-vectored DNA vaccine could provide us a novel potential option for controlling NDV infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study took use of a regulated delayed lysis Salmonella vector for the design of an orally administrated vaccine against NDV.

Construction and Immunogenicity of Novel Chimeric Virus-Like Particles Bearing Antigens of Infectious Bronchitis Virus and Newcastle Disease Virus

Infectious bronchitis virus (IBV) and Newcastle disease virus (NDV) are two poultry pathogens seriously affecting the poultry industry. Here, IBV S1 and the ectodomain of NDV F proteins were separately linked with the trans-membrane and carboxy-terminal domain of IBV S protein (S_TMCT), composing rS and rF; thus, a novel chimeric infectious bronchitis-Newcastle disease (IB-ND) virus-like particles (VLPs) vaccine containing the rS, rF, and IBV M protein was constructed. Under the transmission electron microscope (TEM), VLPs possessing similar morphology to natural IBV were observed. To evaluate the immunogenicity of chimeric IB-ND VLPs, specific pathogen-free (SPF) chickens were immunized with three increasing doses (50, 75, and 100 μg protein of VLPs). Results of ELISAs detecting IBV and NDV specific antibodies and IL-4 and IFN-γ T cell cytokines indicated that vaccination with chimeric IB-ND VLPs could efficiently induce humoral and cellular immune responses. In the challenge study, chimeric IB-ND VLPs (100 μg protein) provided 100% protection against IBV or NDV virulent challenge from death, and viral RNA levels in tissues and swabs were greatly reduced. Collectively, chimeric IB-ND VLPs are highly immunogenic and could provide complete protection from an IBV or NDV virulent challenge. Chimeric IB-ND VLPs are an appealing vaccine candidate and a promising vaccine platform bearing multivalent antigens.

A double recombinant herpes virus of turkeys for the protection of chickens against Newcastle, infectious laryngotracheitis and Marek's diseases

A double recombinant strain of herpes virus of turkeys (HVT) was constructed that contains the fusion (F) gene from Newcastle disease virus (NDV) and the gD plus gI genes from infectious laryngotracheitis virus (ILTV) inserted into a non-essential region of the HVT genome. Expression of the F protein was controlled by a human cytomegalovirus promoter, whereas expression of gD plus gI was driven by an ILTV promoter. The double recombinant vaccine virus (HVT-NDV-ILT) was fully stable genetically and phenotypically following extended passage in cell culture and infection of chickens. Safety of the vaccine virus was confirmed by overdose and backpassage studies in specific-pathogen-free chickens. Chickens vaccinated with a single dose of HVT-NDV-ILT administered by the in ovo route were highly protected from challenge with the velogenic NDV (GB Texas), ILTV (LT 96-3) and Marek's disease virus (GA 5) strains (97%, 94% and 97%, respectively). Similarly, chickens vaccinated with a single dose by subcutaneous (SC) route at 1 day of age were highly protected from challenge with the same three viruses (100%, 100%, and 88%, respectively). The protection level of a single dose given by in ovo or SC route against challenge with a virulent Marek's disease virus strain demonstrates that insertion of multiple genes from two different pathogens within the HVT genome had no adverse effect on the capacity of HVT to protect against Marek's disease. These results demonstrate that HVT-NDV-ILT is a safe and efficacious vaccine for simultaneous control of NDV, ILTV and Marek's diseases.

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.

Recombinant-attenuated Salmonella Pullorum strain expressing the hemagglutinin-neuraminidase protein of Newcastle disease virus (NDV) protects chickens against NDV and Salmonella Pullorum challenge

Newcastle disease virus (NDV) and Salmonella Pullorum have significant damaging effects on the poultry industry, but no previous vaccine can protect poultry effectively. In this study, a recombinant-attenuated S. Pullorum strain secreting the NDV hemagglutinin-neuraminidase (HN) protein, C79-13ΔcrpΔasd (pYA-HN), was constructed by using the suicide plasmid pREasd-mediated bacteria homologous recombination method to form a new bivalent vaccine candidate against Newcastle disease (ND) and S. Pullorum disease (PD). The effect of this vaccine candidate was compared with those of the NDV LaSota and C79-13ΔcrpΔasd (pYA) strains. The serum hemagglutination inhibition antibody titers, serum immunoglobulin G (IgG) antibodies, secretory IgA, and stimulation index in lymphocyte proliferation were increased significantly more (p < 0.01) in chickens inoculated with C79-13ΔcrpΔasd (pYA-HN) than with C79-13ΔcrpΔasd (pYA) but were not significantly increased compared with the chickens immunized with the LaSota live vaccine (p > 0.05). Moreover, the novel strain provides 60% and 80% protective efficacy against the NDV virulent strain F48E9 and the S. Pullorum virulent strain C79-13. In summary, in this study, a recombinant-attenuated S. Pullorum strain secreting NDV HN protein was constructed. The generation of the S. Pullorum C79-13ΔcrpΔasd (pYA-HN) strain provides a foundation for the development of an effective living-vector double vaccine against ND and PD.

Diagnostic and Vaccination Approaches for Newcastle Disease Virus in Poultry: The Current and Emerging Perspectives

Newcastle disease (ND) is one of the most devastating diseases that considerably cripple the global poultry industry. Because of its enormous socioeconomic importance and potential to rapidly spread to naïve birds in the vicinity, ND is included among the list of avian diseases that must be notified to the OIE immediately upon recognition. Currently, virus isolation followed by its serological or molecular identification is regarded as the gold standard method of ND diagnosis. However, this method is generally slow and requires specialised laboratory with biosafety containment facilities, making it of little relevance under epidemic situations where rapid diagnosis is seriously needed. Thus, molecular based diagnostics have evolved to overcome some of these difficulties, but the extensive genetic diversity of the virus ensures that isolates with mutations at the primer/probe binding sites escape detection using these assays. This diagnostic dilemma leads to the emergence of cutting-edge technologies such as next-generation sequencing (NGS) which have so far proven to be promising in terms of rapid, sensitive, and accurate recognition of virulent Newcastle disease virus (NDV) isolates even in mixed infections. As regards disease control strategies, conventional ND vaccines have stood the test of time by demonstrating track record of protective efficacy in the last 60 years. However, these vaccines are unable to block the replication and shedding of most of the currently circulating phylogenetically divergent virulent NDV isolates. Hence, rationally designed vaccines targeting the prevailing genotypes, the so-called genotype-matched vaccines, are highly needed to overcome these vaccination related challenges. Among the recently evolving technologies for the development of genotype-matched vaccines, reverse genetics-based live attenuated vaccines obviously appeared to be the most promising candidates. In this review, a comprehensive description of the current and emerging trends in the detection, identification, and control of ND in poultry are provided. The strengths and weaknesses of each of those techniques are also emphasised.

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.

Recombinant Avian Paramyxovirus Serotypes 2, 6, and 10 as Vaccine Vectors for Highly Pathogenic Avian Influenza in Chickens with Antibodies Against Newcastle Disease Virus

Recombinant Newcastle disease virus (rNDV) expressing the hemagglutinin of highly pathogenic avian influenza virus (HPAIV HA) induces protective immunity against HPAIV in chickens. However, the efficacy of rNDV vectors is hampered when chickens are pre-immune to NDV, and most commercial chickens are routinely vaccinated against NDV. We recently showed that avian paramyxovirus serotypes 2, 6, and 10 (APMV-2, APMV-6, and APMV-10), which belong to the same genus as NDV, have low cross-reactivity with anti-NDV antisera. Here, we used reverse genetics to generate recombinant APMV-2, APMV-6, and APMV-10 (rAPMV-2/HA, rAPMV-6/HA, and rAPMV-10/HA) that expressed an HA protein derived of subtype H5N1 HPAIV, A/chicken/Yamaguchi/7/2004. Chickens pre-immunized against NDV (age, 7 wk) were vaccinated with rAPMV/HAs; 14 days after vaccination, chickens were challenged with a lethal dose of HPAIV. Immunization of chickens pre-immunized against NDV with rAPMV-2/HA, rAPMV-6/HA, or rAPMV-10/HA protected 50%, 50%, and 25%, respectively, in groups of chickens given an rAPMV/HA with 106 median embryo infectious dose (EID₅₀) or 50%, 50%, and 90%, respectively, in those with 10⁷ EID₅₀; in contrast, rNDV/HA protected none of the chicken vaccinated with 10⁶ EID₅₀ and induced only partial protection even with 10⁷ EID_50. Therefore, the presence of anti-NDV antibodies did not hamper the efficacy of rAPMV-2/HA, rAPMV-6/HA, or rAPMV-10/HA. These results suggest that rAPMV-2, rAPMV-6, and rAPMV-10 are potential vaccine vectors, especially for commercial chickens, which are routinely vaccinated against NDV.

Quantitative investigation of the direct interaction between Hemagglutinin and fusion proteins of Peste des petits ruminant virus using surface Plasmon resonance

Background

The specific and dynamic interaction between the hemagglutinin (H) and fusion (F) proteins of morbilliviruses is a prerequisite for the conformational rearrangements and membrane fusion during infection process. The two heptad repeat regions (HRA and HRB) of F protein are both important for the triggering of F protein.

Methods

In this study, the direct interactions of Peste des petits ruminants virus (PPRV) H with F, HRA and HRB were quantitatively evaluated using biosensor surface plasmon resonance (SPR).

Results

The binding affinities of immobilized pCMV-HA-H (HA-H) interacted with proteins pCMV-HA-F (HA-F) and pCMV-HA-HRB (HA-HRB) (K_D = 1.91 × 10^− 8 M and 2.60 × 10^− 7 M, respectively) reacted an order of magnitude more strongly than that of pCMV-HA-HRA (HA-HRA) and pCMV-HA-Tp IGFR-LD (HA) (K_D = 1.08 × 10^− 4 M and 1.43 × 10^− 4 M, respectively).

Conclusions

The differences of the binding affinities suggested that HRB is involved in functionally important intermolecular interaction in the fusion process.

Development of a novel Newcastle disease virus (NDV) neutralization test based on recombinant NDV expressing enhanced green fluorescent protein

BACKGROUND

Newcastle disease is one of the most important infectious diseases of poultry, caused by Newcastle disease virus (NDV). This virus is distributed worldwide and it can cause severe economic losses in the poultry industry due to recurring outbreaks in vaccinated and unvaccinated flocks. Protection against NDV in chickens has been associated with development of humoral response. Although hemagglutination inhibition (HI) assay and ELISA do not corroborate the presence of neutralizing antibodies (nAbs); they are used to measure protection and immune response against NDV.

METHODS

In this study, we established a system to recover a recombinant NDV (rLS1) from a cloned cDNA, which is able to accept exogenous genes in desired positions. An enhanced green fluorescent protein (eGFP) gene was engineered in the first position of the NDV genome and we generated a recombinant NDV carrying eGFP. This NDV- eGFP reporter virus was used to develop an eGFP-based neutralization test (eGFP-NT), in which nAbs titers were expressed as the reciprocal of the highest dilution that expressed the eGFP.

RESULTS

The eGFP-NT gave conclusive results in 24 h without using any additional staining procedure. A total of 57 serum samples were assayed by conventional neutralization (NT) and eGFP-NT. Additionally, HI and a commercial ELISA kit were evaluated with the same set of samples. Although HI (R ² = 0.816) and ELISA (R ² = 0.791) showed substantial correlation with conventional NT, eGFP-NT showed higher correlation (R ² = 0.994), indicating that eGFP-NT is more accurate method to quantify nAbs.

CONCLUSIONS

Overall, the neutralization test developed here is a simple, rapid and reliable method for quantitation of NDV specific nAbs. It is suitable for vaccine studies and diagnostics.

Newcastle disease virus (NDV) recombinant expressing the hemagglutinin of H7N9 avian influenza virus protects chickens against NDV and highly pathogenic avian influenza A (H7N9) virus challenges

The emerged highly pathogenic avian influenza A (H7N9) (HPAI) viruses in China pose a dual challenge to public health and poultry industry. Thus H7N9 vaccines are in an urgent need. In this study, we constructed a Newcastle disease virus (NDV)-vectored vaccine (rLXHAF) expressing the hemagglutinin (HA) of H7N9 virus fused with the transmembrane/cytoplasmic tail domain of the NDV fusion protein. rLXHAF stably expressed the HA protein, exhibited similar growth kinetics and pathogenicity as the parental virus. rLXHAF induced positive NDV-specific hemagglutination inhibition (HI), virus neutralization (VN) and total IgY antibodies and completely protected chickens from NDV challenge. Unexpectedly, rLXHAF elicited undetectable HI and VN titers but high overall IgY antibody titers against H7N9 measured by ELISA. The vaccine provided 80% protection against HPAI H7N9 challenge. Virus shedding of NDV and H7N9 challenge strains was reduced. Our results suggest that rLXHAF is immunogenic and efficacious against HPAI H7N9 virus in chickens.

Avian Paramyxovirus Type-3 as a Vaccine Vector: Identification of a Genome Location for High Level Expression of a Foreign Gene

Avian paramyxovirus serotype 3 (APMV-3) causes infection in a wide variety of avian species, but it does not cause apparent diseases in chickens. On the contrary, APMV-1, also known as Newcastle disease virus (NDV), can cause severe disease in chickens. Currently, natural low virulence strains of NDV are used as live-attenuated vaccines throughout the world. NDV is also being evaluated as a vaccine vector against poultry pathogens. However, due to routine vaccination programs, chickens often possess pre-existing antibodies against NDV, which may cause the chickens to be less sensitive to recombinant NDV vaccines expressing antigens of other avian pathogens. Therefore, it may be possible for an APMV-3 vector vaccine to circumvent this issue. In this study, we determined the optimal insertion site in the genome of APMV-3 for high level expression of a foreign gene. We generated recombinant APMV-3 viruses expressing the green fluorescent protein (GFP) by inserting the GFP gene at five different intergenic regions in the genome. The levels of GFP transcription and translation were evaluated. Interestingly, the levels of GFP transcription and translation did not follow the 3′-to-5′ attenuation mechanism of non-segmented, negative-sense RNA viruses. The insertion of GFP gene into the P-M gene junction resulted in higher level of expression of GFP than when the gene was inserted into the upstream N-P gene junction. Unlike NDV, insertion of GFP did not attenuate the growth efficiency of AMPV-3. Thus, APMV-3 could be a more useful vaccine vector for avian pathogens than NDV.

Infection of Goose with Genotype VIId Newcastle Disease Virus of Goose Origin Elicits Strong Immune Responses at Early Stage

Newcastle disease (ND), caused by virulent strains of Newcastle disease virus (NDV), is a highly contagious disease of birds that is responsible for heavy economic losses for the poultry industry worldwide. However, little is known about host-virus interactions in waterfowl, goose. In this study, we aim to characterize the host immune response in goose, based on the previous reports on the host response to NDV in chickens. Here, we evaluated viral replication and mRNA expression of 27 immune-related genes in 10 tissues of geese challenged with a genotype VIId NDV strain of goose origin (go/CH/LHLJ/1/06). The virus showed early replication, especially in digestive and immune tissues. The expression profiles showed up-regulation of Toll-like receptor (TLR)1–3, 5, 7, and 15, avian β-defensin (AvBD) 5–7, 10, 12, and 16, cytokines [interleukin (IL)-8, IL-18, IL-1β, and interferon-γ], inducible NO synthase (iNOS), and MHC class I in some tissues of geese in response to NDV. In contrast, NDV infection suppressed expression of AvBD1 in cecal tonsil of geese. Moreover, we observed a highly positive correlation between viral replication and host mRNA expressions of TLR1-5 and 7, AvBD4-6, 10, and 12, all the cytokines measured, MHC class I, FAS ligand, and iNOS, mainly at 72 h post-infection. Taken together, these results demonstrated that NDV infection induces strong innate immune responses and intense inflammatory responses at early stage in goose which may associate with the viral pathogenesis.

Expression of recombinant Newcastle disease virus F protein in Pichia pastoris and its immunogenicity using flagellin as the adjuvant

Newcastle disease (ND), a highly contagious, acute, and potent infectious disease caused by Newcastle disease virus (NDV), has a considerable impact on the global poultry industry. Although both live attenuated and inactivated vaccines are used to prevent and control the spread of ND among chickens, the increasing number of ND outbreaks in commercial poultry flocks worldwide indicates that routine vaccinations are insufficient to control ND. Hence, efforts are being invested into developing alternative and more effective vaccination strategies. In this study, we focus on F protein, the neutralizing and protective antigen of NDV, and flagellin (FliC), a toll-like receptor 5 (TLR5) agonist that is an effective inducer of innate immune responses. We amplified F gene from velogenic NDV strain F48E8. The recombinant histidine (His)-tagged F protein was efficiently expressed in a Pichia pastoris (P. pastoris) eukaryotic system and verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blotting. The conditions for F protein expression in P. pastoris were optimal. The immunogenicity of F protein with FliC as the adjuvant was evaluated in a C3H/HeJ mouse model. FliC was found to enhance both F-specific and NDV-specific IgG responses and F-specific cellular immune responses following intraperitoneal co-administration with F protein. Thus, the recombinant F protein expressed by P. pastoris when used with flagellin as the adjuvant has potential as a subunit vaccine candidate.

Construction of recombinant baculovirus vaccines for Newcastle disease virus and an assessment of their immunogenicity

Newcastle disease (ND) is a lethal avian infectious disease caused by Newcastle disease virus (NDV) which poses a substantial threat to China's poultry industry. Conventional live vaccines against NDV are available, but they can revert to virulent strains and do not protect against mutant strains of the virus. Therefore, there is a critical unmet need for a novel vaccine that is safe, efficacious, and cost effective. Here, we designed novel recombinant baculovirus vaccines expressing the NDV F or HN genes. To optimize antigen expression, we tested the incorporation of multiple regulatory elements including: (1) truncated vesicular stomatitis virus G protein (VSV-GED), (2) woodchuck hepatitis virus post-transcriptional regulatory element (WPRE), (3) inverted terminal repeats (ITRs) of adeno-associated virus (AAV Serotype II), and (4) the cytomegalovirus (CMV) promoter. To test the in vivo efficacy of the viruses, we vaccinated chickens with each construct and characterized the cellular and humoral immune response to challenge with virulent NDV (F48E9). All of the vaccine constructs provided some level of protection (62.5-100% protection). The F-series of vaccines provided a greater degree of protection (87.5-100%) than the HN-series (62.5-87.5%). While all of the vaccines elicited a robust cellular and humoral response subtle differences in efficacy were observed. The combination of the WPRE and VSV-GED regulatory elements enhanced the immune response and increased antigen expression. The ITRs effectively increased the length of time IFN-γ, IL-2, and IL-4 were expressed in the plasma. The F-series elicited higher titers of neutralizing antibody and NDV-specific IgG. The baculovirus system is a promising platform for NDV vaccine development that combines the immunostimulatory benefits of a recombinant virus vector with the non-replicating benefits of a DNA vaccine.

Recombinant infectious bronchitis virus (IBV) H120 vaccine strain expressing the hemagglutinin-neuraminidase (HN) protein of Newcastle disease virus (NDV) protects chickens against IBV and NDV challenge

Infectious bronchitis (IB) and Newcastle disease (ND) are common viral diseases of chickens, which are caused by infectious bronchitis virus (IBV) and Newcastle disease virus (NDV), respectively. Vaccination with live attenuated strains of IBV-H120 and NDV-LaSota are important for the control of IB and ND. However, conventional live attenuated vaccines are expensive and result in the inability to differentiate between infected and vaccinated chickens. Therefore, there is an urgent need to develop new efficacious vaccines. In this study, using a previously established reverse genetics system, we generated a recombinant IBV virus based on the IBV H120 vaccine strain expressing the haemagglutinin-neuraminidase (HN) protein of NDV. The recombinant virus, R-H120-HN/5a, exhibited growth dynamics, pathogenicity and viral titers that were similar to those of the parental IBV H120, but it had acquired hemagglutination activity from NDV. Vaccination of SPF chickens with the R-H120-HN/5a virus induced a humoral response at a level comparable to that of the LaSota/H120 commercial bivalent vaccine and provided significant protection against challenge with virulent IBV and NDV. In summary, the results of this study indicate that the IBV H120 strain could serve as an effective tool for designing vaccines against IB and other infectious diseases, and the generation of IBV R-H120-HN/5a provides a solid foundation for the development of an effective bivalent vaccine against IBV and NDV.

Comprehensive Analysis and Characterization of Linear Antigenic Domains on HN Protein from Genotype VII Newcastle Disease Virus Using Yeast Surface Display System

Circulation of genotype VII Newcastle disease virus (NDV) has posed a great threat for the poultry industry worldwide. Antibodies against Hemagglutinin-neuraminidase (HN), a membrane protein of NDV with critical roles in NDV infection, have been reported to provide chickens protection from NDV infection. In this study, we comprehensively analyzed the in vivo antibody responses against the linear antigenic domains of the HN protein from genotype VII NDV using a yeast surface display system. The results revealed four distinct regions of HN, P1 (1-52aa), P2 (53-192aa), P3 (193-302aa) and P4 (303-571aa), respectively, according to their antigenic potency. Analysis by FACS and ELISA assay indicated P2 to be the dominant linear antigenic domain, with the immunogenic potency to protect the majority of chickens from NDV challenge. In contrast, the P1, P3 and P4 domains showed weak antigenicity in vivo and could not protect chickens from NDV challenge. These results provide important insight into the characteristic of humoral immune responses elicited by HN of NDV in vivo.

Quantification of rHVT-F genome load in feather follicles by specific real-time qPCR as an indicator of NDV-specific humoral immunity induced by day-old vaccination in SPF chickens

The purpose of this study was to look for a reliable molecular method for confirmation of uptake of recombinant turkey herpesvirus vaccine against Newcastle disease (rHVT-F) and for use as a valuable prediction tool of Newcastle disease virus (NDV)-specific immune response in chickens deprived of maternally derived antibody (MDA). A quantitative real-time polymerase chain reaction (real-time qPCR) specific to rHVT-F was developed. The method was applied to various tissue samples taken from specific pathogen free (SPF) chickens experimentally inoculated at day-old with one dose of rHVT-F vaccine over a 6-week period. Among the tested tissues, the rHVT-F vaccine was detected predominantly in the bursa of Fabricius (BF) and the lung for the first week, followed by a progressive decline from 9 days onwards. Then, an increase of genome load was observed in the feather follicles (FF) with a peak at 2 weeks, rising to a level almost 10(3)-fold greater than in the other tissues. Importantly, the rHVT-F genome load in FF appeared to be strongly correlated to the humoral immunity specific to NDV as evaluated by haemagglutination inhibition (HI) test and NDV-specific IgG, IgM and IgA ELISAs. This is the first report of quantification of rHVT-F vaccine in FF and its correlation with the induction of ND-specific immune response in chickens with no MDA. Our data indicate that the application of this real-time qPCR assay on FF samples taken from chickens in the field may be used to confirm rHVT-F vaccine administration and uptake with the important added benefit of offering a non-disruptive sampling procedure.

The Antiviral Effect of High-Molecular Weight Poly-Gamma-Glutamate against Newcastle Disease Virus on Murine Macrophage Cells

This study demonstrates the capacity of HM-γ-PGA treatment to significantly protect murine macrophage cells (RAW 264.7 cells) against NDV infection. Such protection can be explained by the induction of antiviral state of HM-γ-PGA in RAW 264.7 cells via TLR4-mediated IRF-3, IRF-7, IFN-β, and IFN-related gene induction as shown in time-dependent changes in mRNA expression confirmed by polymerase chain reaction (PCR). Moreover, the present research also showed that HM-γ-PGA can induce proinflammatory cytokine secretion in RAW 264.7 as measured by enzyme-linked immunosorbent assay (ELISA). Therefore, our findings suggest that HM-γ-PGA can be a potential antiviral substance that can inhibit NDV infection through its stimulation of antiviral state on RAW 264.7 cells. These results have been consistent with the previous studies showing that HM-γ-PGA can protect RAW 264.7 cells and mice against influenza infection. However, it should be noted that although murine macrophage cells are susceptible to NDV, they are not the natural host cells of the virus; thus further in vivo and in vitro studies involving chicken and chicken immune cells are needed to fully assess the efficacy and applicability of HM-γ-PGA in the poultry industry.

Species based synonymous codon usage in fusion protein gene of Newcastle disease virus

Newcastle disease is highly pathogenic to poultry and many other avian species. However, the Newcastle disease virus (NDV) has also been reported from many non-avian species. The NDV fusion protein (F) is a major determinant of its pathogenicity and virulence. The functionalities of F gene have been explored for the development of vaccine and diagnostics against NDV. Although the F protein is well studied but the codon usage and its nucleotide composition from NDV isolated from different species have not yet been explored. In present study, we have analyzed the factors responsible for the determination of codon usage in NDV isolated from four major avian host species. The F gene of NDV is analyzed for its base composition and its correlation with the bias in codon usage. Our result showed that random mutational pressure is responsible for codon usage bias in F protein of NDV isolates. Aromaticity, GC3s, and aliphatic index were not found responsible for species based synonymous codon usage bias in F gene of NDV. Moreover, the low amount of codon usage bias and expression level was further confirmed by a low CAI value. The phylogenetic analysis of isolates was found in corroboration with the relatedness of species based on codon usage bias. The relationship between the host species and the NDV isolates from the host does not represent a significant correlation in our study. The present study provides a basic understanding of the mechanism involved in codon usage among species.

Package of NDV-pseudotyped HIV-Luc virus and its application in the neutralization assay for NDV infection

Newcastle disease virus (NDV) is a member of the Paramyxovirinae subfamily and can infect most species of birds. It has been a great threat for the poultry industry all around the world. In this report, we successfully produced infectious pseudotyped pNL4-3-Luc-R⁻E⁻ (HIV-Luc) viruses with the HN and F envelope proteins of NDV. Further investigation revealed the cytoplasmic domains of HN and F, especially HN, plays a significant role in the infection efficiency of these pseudotyped HIV-Luc viruses. Replacement of, or direct fusion to the cytoplasmic domain of the HN protein by that of vesicular stomatitis virus G (VSV-G) could greatly enhance or destroy the infective potential of HN and F-pseudotyped (NDV-pseudotyped) HIV-Luc virus. We further established a novel neutralization assay to evaluate neutralizing antibodies against NDV with the NDV-pseudotyped HIV-Luc viruses. Comparative neutralization data indicate that the results determined by using the NDV-pseudotyped HIV-Luc viruses are as reliable as those by the conventional virus-neutralization assay (VN test) with native NDV. Moreover, the results show that the novel neutralization assay is more sensitive than the VN test.

Newcastle disease virus: current status and our understanding

Newcastle disease (ND) is one of the highly pathogenic viral diseases of avian species. ND is economically significant because of the huge mortality and morbidity associated with it. The disease is endemic in many third world countries where agriculture serves as the primary source of national income. Newcastle disease virus (NDV) belongs to the family Paramyxoviridae and is well characterized member among the avian paramyxovirus serotypes. In recent years, NDV has lured the virologists not only because of its pathogenic potential, but also for its oncolytic activity and its use as a vaccine vector for both humans and animals. The NDV based recombinant vaccine offers a pertinent choice for the construction of live attenuated vaccine due to its modular nature of transcription, minimum recombination frequency, and lack of DNA phase during replication. Our current understanding about the NDV biology is expanding rapidly because of the availability of modern molecular biology tools and high-throughput complete genome sequencing.

Virus-like particle vaccine confers protection against a lethal newcastle disease virus challenge in chickens and allows a strategy of differentiating infected from vaccinated animals

In this study, we developed Newcastle disease virus (NDV) virus-like particles (VLPs) expressing NDV fusion (F) protein along with influenza virus matrix 1 (M1) protein using the insect cell expression system. Specific-pathogen-free chickens were immunized with oil emulsion NDV VLP vaccines containing increasing dosages of VLPs (0.4, 2, 10, or 50 μg of VLPs/0.5-ml dose). Three weeks after immunization, the immunogenicity of the NDV VLP vaccines was determined using a commercial enzyme-linked immunosorbent assay (ELISA) kit, and a lethal challenge using a highly virulent NDV strain was performed to evaluate the protective efficacy of the NDV VLP vaccines. NDV VLP vaccines elicited anti-NDV antibodies and provided protection against a lethal challenge in a dose-dependent manner. Although the VLP vaccines containing 0.4 and 2 μg of VLPs failed to achieve high levels of protection, a single immunization with NDV VLP vaccine containing 10 or 50 μg could fully protect chickens from a lethal challenge and greatly reduced challenge virus shedding. Furthermore, we could easily differentiate infected from vaccinated animals (DIVA) using the hemagglutination inhibition (HI) test. These results strongly suggest that utilization of NDV VLP vaccine in poultry species may be a promising strategy for the better control of NDV.