Protection of chickens against overt clinical disease and determination of viral shedding following vaccination with commercially available Newcastle disease virus vaccines upon challenge with highly virulent virus from the California 2002 exotic Newcastle disease outbreak

Prior exposure to pathogens augments host heterogeneity in susceptibility and has key epidemiological consequences

Pathogen epidemics are key threats to human and wildlife health. Across systems, host protection from pathogens following initial exposure is often incomplete, resulting in recurrent epidemics through partially-immune hosts. Variation in population-level protection has important consequences for epidemic dynamics, but how acquired protection influences inter-individual heterogeneity in susceptibility and its epidemiological consequences remains understudied. We experimentally investigated whether prior exposure (none, low-dose, or high-dose) to a bacterial pathogen alters host heterogeneity in susceptibility among songbirds. Hosts with no prior pathogen exposure had little variation in protection, but heterogeneity in susceptibility was significantly augmented by prior pathogen exposure, with the highest variability detected in hosts given high-dose prior exposure. An epidemiological model parameterized with experimental data found that heterogeneity in susceptibility from prior exposure more than halved epidemic sizes compared with a homogeneous population with identical mean protection. However, because infection-induced mortality was also greatly reduced in hosts with prior pathogen exposure, reductions in epidemic size were smaller than expected in hosts with prior exposure. These results highlight the importance of variable protection from prior exposure and/or vaccination in driving population-level heterogeneity and epidemiological dynamics.

Nucleotide sequence characterization, amino acid variations and 3D structural analysis of HN protein of the NDV VIId genotype

BACKGROUND

Haemagglutinin-neuraminidase (HN) is one of the membrane proteins of Newcastle disease virus (NDV) that plays a significant role during host viral infection. Therefore, antibodies against HN are vital for the host's ability to protect itself against NDV infection due to their critical functions in viral infection. As a result, HN has been a candidate protein in vaccine development against the Newcastle disease virus.

METHODS

This report used the full-length sequence of the HN protein of NDV isolated in Iran (VIId subgenotype). We characterize and identify amino acid substitutions in comparison to other more prevalent NDV genotypes, VII subgenotypes and vaccine strains. Furthermore, bioinformatics tools were applied to determine the three-dimensional structure, molecular dynamics simulation and prediction of B-cell antigenic epitopes.

RESULTS

The results showed that the antigenic regions of our isolate are quite comparable to the other VII subgenotypes of NDV isolated from different geographical places. Moreover, by employing the final 3D structure of our HN protein, the amino acid residues are proposed as a B-cell epitope by epitope prediction servers, which leads to the introduction of linear and conformational antigenic sites.

CONCLUSIONS

Immunoinformatic vaccine design principles currently exhibit tremendous potential for developing a new generation of candidate vaccines quickly and economically to eradicate infectious viruses, including the NDV. In order to accomplish this, focus is directed on residues that might be considered antigenic.

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.

In vivo challenge studies on vaccinated chickens indicate a virus genotype mismatched vaccine still offers significant protection against NDV

Although commercial vaccines against Newcastle Disease have been available for decades, outbreaks still occur in the face of vaccination Further vaccination may accelerate viral evolution resulting in a further reduction in vaccine efficacy. A key question is whether genotype-matched vaccines can confer better protection against contemporary type 1 Avian Paramyxoviruses. To assess this, an in vivo vaccine-challenge study was undertaken to assess protection afforded by 'genotype-matched' and commercial vaccine formulations. Groups of chickens were vaccinated twice (prime-boost) with an inactivated preparation of either La Sota Clone 30, AV632-chicken-Cyprus-13 (genotype VII.2), or mock vaccine, and later challenged with virulent AV632-chicken-Cyprus-13. Post vaccinal serological responses differed, although both vaccination/challenge groups showed similar levels of clinical protection compared to the unvaccinated group, where 100 % mortality was observed. Shedding was significantly reduced in the vaccinated groups compared to the unvaccinated group. Virus dissemination in the tissues of vaccinated birds was comparable, but onset of infection was delayed. Two mutations were observed in the HN gene of the heterologous vaccine group; H199N and I192M, the latter thought to be associated with increased fusogenic potential. These data demonstrate that existing vaccine formulations confer similar levels of clinical protection to contemporary strains and that the antigenic heterogeneity of circulating strains does not impact upon shedding profiles in immunised birds. In conclusion, the ability of virulent APMV-1 to cause disease in vaccinated flocks is unlikely to be the result of antigenic mismatch alone, and other factors likely contribute to vaccination failure and breakthrough.

Newcastle disease virus (NDV) recombinant expressing Marek's disease virus (MDV) glycoprotein B significantly protects chickens against MDV and NDV challenges

Marek's disease (MD) is a highly contagious viral neoplastic disease of chickens caused by Marek's disease virus (MDV), resulting in significant economic losses to the poultry industry worldwide. The commonly used live and/or vectored MDV vaccines are expensive to produce and difficult to handle due to the requirement of liquid nitrogen for manufacturing and delivering frozen infected cells that are viable. In this study, we aimed to develop a Newcastle disease virus (NDV) vectored MDV vaccine that can be lyophilized, stored, and transported at 4 °C. Four NDV LaSota (LS) vaccine strain-based recombinant viruses expressing MDV glycoproteins gB, gC, gE, or gI were generated using reverse genetics technology. The biological assessments showed that these recombinant viruses were slightly attenuated in vivo yet retained similar growth kinetics and virus titers in vitro compared to the parental LaSota virus. Vaccination of leghorn chickens (Lines 15I5x71 F1 cross) with these recombinant viruses via intranasal and intraocular routes conferred different levels of protection against virulent MDV challenge. The recombinant expressing the MDV gB protein, rLS/MDV-gB, protected vaccinated birds significantly against MDV-induced tumor formation when challenged at 14 days post-vaccination (DPV) but moderately at 5 DPV. Whereas the other three recombinants provided little protection against the MDV challenge. All four recombinants conferred complete protection against the velogenic NDV challenge. These results demonstrated that the rLS/MDV-gB virus is a safe and efficacious dual vaccine candidate that can be lyophilized and potentially mass-administered via aerosol or drinking water to large chicken populations at a meager cost.

Effect of Different Levels of Maternally Derived Genotype VII Newcastle Disease Virus-Specific Hemagglutination Inhibition Antibodies on Protection against Virulent Challenge in Chicks

Newcastle disease (ND), caused by the virulent Newcastle disease virus (NDV), is an acute, highly contagious, and economically significant avian disease worldwide. Vaccination is the most effective measure for controlling ND. In recent years, vaccines matched with the prevalent strains of genotype VII have been developed and are now commercially available. These vaccines can provide full protection for chickens against clinical disease and mortality after challenges with genotype VII viruses and significantly decrease virus shedding compared to conventional vaccines belonging to genotypes I and II. Vaccinated hens can transfer antibodies to their offspring through the egg yolk. Maternally derived antibodies can provide passive protection against diseases but can also interfere with vaccination efficacy early in life. This study was conducted on chicks hatched from hens vaccinated with a commercial genotype VII NDV-matched vaccine to investigate the correlation between hemagglutination inhibition (HI) antibody levels in chicks and hens and the decaying pattern of maternally derived HI antibodies, and to evaluate the protective efficacy of different levels of maternally derived HI antibodies against challenge with a virulent NDV strain of genotype VII based on survivability and virus shedding. The HI antibody titers in chicks at hatching were about 1.3 log2 lower than those in hens, indicating an antibody transfer rate of approximately 41.52%. The estimated half-life of these antibodies was about 3.2 days. The protective efficacy of maternally derived HI antibodies was positively correlated with the titer. These antibodies could effectively protect chicks against mortality when the titer was 7 log2 or higher, but they were unable to prevent virus shedding or infection even at a high titer of 11 log2. The obtained results will greatly assist producers in determining the immune status of chicks and formulating appropriate vaccination schedules against ND.

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

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

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.

Current situation and future direction of Newcastle disease vaccines

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

Epidemiological surveillance of Newcastle disease virus in Egypt - a 6-year cohort study

Newcastle disease (ND) is one of the most important poultry diseases worldwide and can lead to annual losses of up to 80% of backyard chickens in Africa. A retrospective cohort of 6 years was planned to screen the NDV in intensive chicken and turkey flocks. The existence of velogenic NDV strain was screened in different poultry flocks showing suspected signs of NDV using real-time RT-PCR targeting the F gene of the velogenic strain. A total of 843 poultry flocks were screened during the cohort. Samples were classified based on the month and year as well as the poultry type. All flocks should be negative for avian influenza virus as an inclusion criterion of the study. The F gene of a randomly selected positive sample from each year as well as an archival sample from 2005 was sequenced. An overall of 52.4% (443/842) of the tested farms showed positive results for the velogenic NDV. The cumulative percentage of positive flocks to the total positive flocks per month ranged from 5.9 to 11.8%. The results revealed that NDV is circulating across all months annually without evidence of seasonal tendency of the disease. Most of the strains belong to genotype VII.1.1, with only two strains related to XXI.1.1 and XXI.2. All VII.1.1 strains possess arginine at 27 position while XXI.1.1 and XXI.2 strains showed cysteine at 27 and amino acid substitutions in the signal peptide, cleavage site, and neutralizing epitopes. In conclusion, the current molecular epidemiological surveillance confirms the enzootic nature of NDV. It circulates all year round with no evidence of seasonal incidence. Genotype VII is the most predominant NDV genotype in Egypt.

A pigeon paramyxovirus type 1 isolated from racing pigeon as an inactivated vaccine candidate provides effective protection

Pigeon paramyxovirus type 1 (PPMV-1), a variant of Newcastle disease virus (NDV), causes severe Newcastle disease (ND) in pigeons. However, there is no PPMV-1 vaccine available worldwide. In this study, a strain of PPMV-1 was isolated from outbreaks in a vaccinated racing pigeon (Columbia livia) loft in China, namely, PPMV-1/pigeon/Gansu/China/02/2020 (GS02). Experimental infection with GS02 showed mortality rates of 100% and 87.50% in 4- and 12-week-old pigeons, respectively, suggesting that GS02 is virulent and more sensitive to young pigeons. The whole genome of GS02 determined the fusion (F) protein possessing virulence cleavage site ¹¹²RRQKRF¹¹⁷. Phylogenetic analysis indicated that GS02 was a subgenotype VI.2.1.1.2.2 (VIk) of Class II NDV and more closely related to the JS/06/20/Pi (MW271791) strain, but it was far from the genetic distance from the commercial vaccine chicken-origin La Sota strain. Using inactivated GS02 as a vaccine candidate and inactivated vaccine La Sota to immunize the pigeons, both of them provided complete protection against GS02 challenge. The GS02 vaccine candidate induced higher antibody titers than the La Sota vaccine, and cross-reactivity testing showed antigenically slight differences between GS02 and La Sota. These results indicated that the GS02 candidate could be a potential pigeon-derived vaccine for the prevention and control of PPMV-1 in pigeons.

Performance comparison of homologous and heterologous Newcastle disease virus in vaccines and antibody tests

Antigenic differences between commercial Newcastle Disease Virus (NDV) vaccine and circulating field virus reduce vaccine efficacy. Fifty-layer chickens were divided into five groups: three vaccinated chicken groups using killed LaSota (Genotype II/GII), Mega, or VD (Genotype VII/GVII) viral strains, negative, and positive control groups. On day 28, Hemagglutination Inhibition (HI) serology of vaccinated chickens was performed using whole virus antigens of RIVS, LaSota, Mega, and VD strains. Sera were also tested with an alternative antigen, using an ELISA to detect antibody for the cleavage site F protein peptide from GII and GVII NDV strains. Vaccinated and unvaccinated positive control birds underwent infectious challenges using VD and Mega strains. HI testing showed that antibody titers were higher when tested using homologous antigens than heterologous antigens. ELISA performed with alternative antigens did not perform as well as the established HI test using homologous strains. Viral shedding was reduced by vaccination that was homologous to the infectious challenge in comparison with vaccination using the LaSota strain virus. We conclude that superior results are obtained when serological testing, vaccinations, and vaccine challenge experiments all use circulating strains of ND virus. Implementation of this recommendation would likely reduce viral shedding by vaccinated chickens and be more effective in preventing outbreaks of virulent NDV.

Root-preferential expression of Newcastle virus glycoproteins driven by NtREL1 promoter in tobacco hairy roots and evaluation of oral delivery in mice

Newcastle disease virus (NDV) is a lethal virus in avian species with a disastrous effect on the poultry industry. NDV is enveloped by a host-derived membrane with two glycosylated haemagglutinin-neuraminidase (HN) and Fusion (F) proteins. NDV infection usually leads to death within 2-6 days, so the preexisting antibodies provide the most critical protection for this infection. The HN and F glycoproteins are considered the main targets of the immune system. In the present study, two constructs harboring the HN or F epitopes are sub-cloned separately under the control of a root-specific promoter NtREL1 or CaMV35S (35S Cauliflower Mosaic Virus promoter) as a constitutive promoter. The recombinant vectors were transformed into the Agrobacterium tumefaciens strain LBA4404 and then introduced to tobacco (Nicotiana tabacum L.) leaf disk explants. PCR with specific primers was performed to confirm the presence of the hn and f genes in the genome of the regenerated plants. Then, the positive lines were transformed via non-recombinant A. rhizogenes (strain ATCC15834) to develop hairy roots.HN and F were expressed at 0.37% and 0.33% of TSP using the CaMV35S promoter and at 0.75% and 0.54% of TSP using the NtREL1 promoter, respectively. Furthermore, the mice fed transgenic hairy roots showed a high level of antibody responses (IgG and IgA) against rHN and rF proteins.

Thermoresistant Newcastle disease vaccine effectively protects SPF, native, and commercial chickens in challenge with virulent virus

Background

Due to the more stability and a better homogenecity in immune response, the use of thermoresistant vaccines in different chicken types has been increased.

Objective

This study aimed to evaluate the efficacy of a newly developed Newcastle disease vaccine (ND.TR.IR) originating from I‐2 strain in specific pathogen‐free (SPF) and native and broiler chickens.

Methods

Following determination of pathogenicity indices on the candidate seed, three efficacy examinations were conducted. In the first experiment, 120 1‐day‐old SPF chickens were randomly allocated to six groups and either vaccinated with ND.TR.IR via eye drop at 1, 7, and 21 days of age (V₁, V₇, and V₂₁), or considered as non‐vaccinated control groups (C₁, C₇, and C₂₁). At 20th post‐vaccination day, sera hemagglutination inhibition (HI) antibody titres against ND virus (NDV) were measured and then the chickens were challenged by virulent NDV (vNDV). In the second and third experiments, the efficacy of ND.TR.IR vaccine was compared to routine vaccination program (B1 and LaSota) in native and broiler chickens that were vaccinated at 10 and 20 days of age, respectively. The HI antibody titres were measured on 10, 20, 30, and 40 days of age, and also challenge efficacy test with vNDV was conducted on 30 days of age.

Results

The studied virus, as a vaccinal seed, complied with the pathogenicity indices of avirulent NDV and molecular identity of I‐2 strain. In the efficacy evaluation trials, the vaccinated chickens had higher HI antibody titres against NDV compared with their corresponding control chickens (p < 0.05). Results of the challenge tests indicated 95% and 100% protection against vNDV in native, SPF, and broiler‐vaccinated chickens, respectively.

Conclusions

The present findings indicated that administration of ND.TR.IR induced appropriate HI antibody titres against NDV in SPF, native, and broiler chickens associated with good protection in efficacy test.

Response of three local chicken ecotypes of Ghana to lentogenic and velogenic Newcastle disease virus challenge

This study was carried out to assess the response of three Ghanaian local chicken ecotypes to LaSota (lentogenic) and virulent field strains of Newcastle disease virus (NDV). Local chickens sampled from the Interior Savannah (IS), Forest (FO) and Coastal Savannah (CS) agro-ecological zones were bred and their offspring were challenged with LaSota NDV at 4 weeks of age. The LaSota challenge was replicated four times with different chicken groups. A total of 1438 chicks comprising 509 Coastal Savannah, 518 Forest and 411 Interior Savannah ecotypes were used. Pre- and post-challenge anti-NDV antibody titre levels were determined via ELISA assays. A second trial was conducted by introducing sick birds infected with virulent NDV to a flock of immunologically naïve chickens at 4 weeks old. Body weights were measured pre- and post-infection. Sex of the chickens was determined using a molecular method. In both trials, there was no significant difference among ecotypes in body weight and growth rate. In the LaSota trial, anti-NDV antibody titre did not differ by ecotype or sex. However, there was a positive linear relationship between body weight and antibody titre. In the velogenic NDV trial, survivability and lesion scores were similar among the three ecotypes. This study confirms that a relatively high dose of LaSota (NDV) challenge has no undesirable effect on Ghanaian local chicken ecotypes. All three Ghanaian local chicken ecotypes were susceptible to velogenic NDV challenge. Resistance to NDV by Ghanaian local chickens appears to be determined more by the individual's genetic makeup than by their ecotype.

Detection of Newcastle disease virus and assessment of associated relative risk in backyard and commercial poultry in Kerala, India

Background

Newcastle disease (ND) is an economically important viral disease affecting the poultry industry. In Kerala, a state in South India, incidences of ND in commercial and backyard poultry have been reported. But a systematic statewide study on the prevalence of the disease has not been carried out.

Objectives

A cross‐sectional survey was performed to detect the presence of Newcastle disease virus (NDV) in suspect cases and among apparently healthy commercial flocks and backyard poultry, in the state and to identify risk factors for NDV infection.

Methods

Real‐time reverse transcription‐PCR (RT‐PCR) was used to detect the M gene of NDV in choanal swabs and tissue samples collected from live and dead birds, respectively and the results were statistically analysed.

Results

The predominant clinical signs of the examined birds included mild respiratory signs, huddling together and greenish diarrhoea. Nervous signs in the form of torticollis were noticed in birds in some of the affected flocks. On necropsy, many birds had haemorrhages in the proventriculus and caecal tonsils which were suggestive of ND. Of the 2079 samples tested, 167 (8.0%) were positive for the NDV M‐gene by RT‐PCR. Among 893 samples collected from diseased flocks, 129 (14.5%), were positive for M gene with pairwise relative risk (RR) of 15.6 as compared to apparently healthy flocks where 6 out of 650 (0.9%) samples were positive. All positive samples were from poultry; none of the ducks, pigeons, turkey and wild birds were positive. Commercial broilers were at higher risk of infection than commercial layers (RR: 4.5) and backyard poultry (RR: 4.9). Similarly, birds reared under intensive housing conditions were at a higher risk of being infected as compared to those reared under semi‐intensive (RR: 6.7) or backyard housing (RR: 2.1). Multivariable analysis indicated that significantly higher risk of infection exists during migratory season and during ND outbreaks occurring nearby. Further, lower risk was observed with flock vaccination and backyard or semi‐intensive housing when compared to intensive housing. When the M gene positive samples were tested by RT‐PCR to determine whether the detected NDV were mesogenic/velogenic, 7 (4.2%) were positive.

Conclusions

In Kerala, NDV is endemic in poultry with birds reared commercially under intensive rearing systems being affected the most. The outcome of this study also provides a link between epidemiologic knowledge and the development of successful disease control measures. Statistical analysis suggests that wild bird migration season and presence of migratory birds influences the prevalence of the virus in the State. Further studies are needed to genotype and sub‐genotype the detected viruses and to generate baseline data on the prevalence of NDV strains, design better detection strategies, and determine patterns of NDV transmission across domestic poultry and wild bird populations in Kerala.

A study was carried out to detect Newcastle disease virus in commercial and backyard chicken in Kerala, India, by employing real time RT‐PCR. The overall percentage positivity obtained was 8%. Risk analysis revealed significantly higher risk for broiler birds and intensive type of housing. The risk was also higher for birds housed in facilities in areas with a history of occurrence of the disease, if migratory birds were present in the area, and during bird migration season. It was also observed that vaccination had a protective effect as indicated by lower relative risk values.

Pathology of Komarov vaccine in Hitchner B1 vaccinated and unvaccinated broilers

Newcastle disease (ND) is a major problem of poultry production worldwide. Control is by biosecurity and vaccination. In this project, we studied the pathology of Komarov vaccine which is commonly used in many countries of Africa on the Hitchner B1 (HBI) vaccinated and unvaccinated broilers. Seventy-five Arbor Acres broilers were obtained at 1 day old. Twenty-five of the broilers were given HB1 vaccine at the hatchery and Komarov vaccine at 5 weeks of age (group HK). A second group of 25 broilers were given only Komarov vaccine at 5 weeks of age (group K). The third group remained as unvaccinated (UU). All the groups were observed for clinical signs and lesions. Depression, sneezing, coughing and noisy respiration were observed in group K broilers from day 2 post Komarov vaccination (PKV). Leg paralysis occurred in 6 broilers on day 8 PKV. The clinical signs were milder in the HK broilers. Only one broiler showed leg paralysis in this group on day 18 PKV. No mortality occurred in the three groups. The bursa, spleen and thymus showed mild to moderate enlargement, atrophy and depletion of lymphocytes on days 3, 5, 8 and 14 PKV in HK and K groups. The trachea and lungs were congested. The haemagglutination inhibition (HI) antibody titres in the K group were higher than those of HK and UU groups on days 7, 24 and 21 PKV. The above observations show that Komarov vaccine may cause no mortality in vaccinated and unvaccinated broilers and higher HI antibodies are produced in broilers that have not been vaccinated earlier.

Infectious Bronchitis Virus (Gammacoronavirus) in Poultry Farming: Vaccination, Immune Response and Measures for Mitigation

Infectious bronchitis virus (IBV) poses significant financial and biosecurity challenges to the commercial poultry farming industry. IBV is the causative agent of multi-systemic infection in the respiratory, reproductive and renal systems, which is similar to the symptoms of various viral and bacterial diseases reported in chickens. The avian immune system manifests the ability to respond to subsequent exposure with an antigen by stimulating mucosal, humoral and cell-mediated immunity. However, the immune response against IBV presents a dilemma due to the similarities between the different serotypes that infect poultry. Currently, the live attenuated and killed vaccines are applied for the control of IBV infection; however, the continual emergence of IB variants with rapidly evolving genetic variants increases the risk of outbreaks in intensive poultry farms. This review aims to focus on IBV challenge-infection, route and delivery of vaccines and vaccine-induced immune responses to IBV. Various commercial vaccines currently have been developed against IBV protection for accurate evaluation depending on the local situation. This review also highlights and updates the limitations in controlling IBV infection in poultry with issues pertaining to antiviral therapy and good biosecurity practices, which may aid in establishing good biorisk management protocols for its control and which will, in turn, result in a reduction in economic losses attributed to IBV infection.

Novel Recombinant Newcastle Disease Virus-Based In Ovo Vaccines Bypass Maternal Immunity to Provide Full Protection from Early Virulent Challenge

Newcastle disease (ND) is one of the most economically important poultry diseases. Despite intensive efforts with current vaccination programs, this disease still occurs worldwide, causing significant mortality even in vaccinated flocks. This has been partially attributed to a gap in immunity during the post-hatch period due to the presence of maternal antibodies that negatively impact the replication of the commonly used live vaccines. In ovo vaccines have multiple advantages and present an opportunity to address this problem. Currently employed in ovo ND vaccines are recombinant herpesvirus of turkeys (HVT)-vectored vaccines expressing Newcastle disease virus (NDV) antigens. Although proven efficient, these vaccines have some limitations, such as delayed immunogenicity and the inability to administer a second HVT vaccine post-hatch. The use of live ND vaccines for in ovo vaccination is currently not applicable, as these are associated with high embryo mortality. In this study, recombinant NDV-vectored experimental vaccines containing an antisense sequence of avian interleukin 4 (IL4R) and their backbones were administered in ovo at different doses in 18-day-old commercial eggs possessing high maternal antibodies titers. The hatched birds were challenged with virulent NDV at 2 weeks-of-age. Post-hatch vaccine shedding, post-challenge survival, challenge virus shedding, and humoral immune responses were evaluated at multiple timepoints. Recombinant NDV (rNDV) vaccinated birds had significantly reduced post-hatch mortality compared with the wild-type LaSota vaccine. All rNDV vaccines were able to penetrate maternal immunity and induce a strong early humoral immune response. Further, the rNDV vaccines provided protection from clinical disease and significantly decreased virus shedding after early virulent NDV challenge at two weeks post-hatch. The post-challenge hemagglutination-inhibition antibody titers in the vaccinated groups remained comparable with the pre-challenge titers, suggesting the capacity of the studied vaccines to prevent efficient replication of the challenge virus. Post-hatch survival after vaccination with the rNDV-IL4R vaccines was dose-dependent, with an increase in survival as the dose decreased. This improved survival and the dose-dependency data suggest that novel attenuated in ovo rNDV-based vaccines that are able to penetrate maternal immunity to elicit a strong immune response as early as 14 days post-hatch, resulting in high or full protection from virulent challenge, show promise as a contributor to the control of Newcastle disease.

Efficacy of Vaccination against Infection with Velogenic Newcastle Disease Virus Genotypes VI and VII 1.1 Strains in Japanese Quails

Newcastle disease virus (NDV), a major pathogen of poultry worldwide, causes significant economic losses in the poultry industry. To characterize the ability of recently isolated virulent strains of NDV genotypes VI and VII to cause disease in quails, and to evaluate the efficacy of two NDV vaccines against such strains, Japanese quails were experimentally inoculated with either NDV genotype VI (Pigeon F-VI strain) or VII 1.1 (GHB-328 strain) with or without vaccination with inactivated NDV vaccine of genotype II (La Sota strain) or VII (KBNP strain). Mild to severe neurological signs developed in quails inoculated with the Pigeon F-VI strain from 3 to 14 days post infection (PI) and from 4 to 10 days PI in birds infected with the GHB-328 strain. The mortality rates were 46% and 33% for birds inoculated with NDV VI and NDV VII 1.1, respectively. The severity of histopathological changes depended on the viral isolates used. Vaccination with the La Sota or KBNP vaccine strain successfully protected quails against NDV-induced mortality and decreased the severity of clinical signs, pathological changes and cloacal viral shedding. This study showed that these virulent NDV isolates had mild to moderate pathogenicity in quails and that both vaccines protected against challenge with both virus strains. NDV vaccine genotype VII improved the level of protection against challenge with the VII 1.1 genotype compared with the classic vaccine, but failed to protect quails against challenge with the VI genotype.

Comparison of tracheal and choanal cleft swabs and poultry dust samples for detection of Newcastle disease virus and infectious bronchitis virus genome in vaccinated meat chicken flocks

This study assessed different methods (tracheal and choanal cleft swabs from individual birds, and poultry dust as a population level measure) to evaluate the shedding kinetics of infectious bronchitis virus (IBV) and Newcastle disease virus (NDV) genome in meat chicken flocks after spray vaccination at hatchery. Dust samples and tracheal and choanal cleft swabs were collected from four meat chicken flocks at 10, 14, 21 and 31 days post vaccination (dpv) and tested for IBV and NDV genome copies (GC) by reverse transcriptase (RT)-PCR. IBV and NDV GC were detected in all sample types throughout the study period. Detection rates for choanal cleft and tracheal swabs were comparable, with moderate and fair agreement between sample types for IBV (McNemar's = 0.27, kappa = 0.44) and NDV (McNemar's = 0.09; kappa = 0.31) GC respectively. There was no significant association for IBV GC in swabs and dust samples (R2 = 0.15, P = 0.13) but NDV detection rates and viral load in swabs were strongly associated with NDV GC in dust samples (R2 = 0.86 and R2 = 0.90, P<0.001). There was no difference in IBV and NDV GC in dust samples collected from different locations within a poultry house. In conclusion, dust samples collected from any location within poultry house show promise for monitoring IBV and NDV GC in meat chickens at a population level and choanal cleft swabs can be used for detection of IBV and NDV GC instead of tracheal swabs in individual birds.

Efficacy of a Turkey Herpesvirus Vectored Newcastle Disease Vaccine against Genotype VII.1.1 Virus: Challenge Route Affects Shedding Pattern

The control of Newcastle disease (ND) highly relies on vaccination. Immunity provided by a ND vaccine can be characterized by measuring the level of clinical protection and reduction in challenge virus shedding. The extent of shedding depends a lot on the characteristics of vaccine used and the quality of vaccination, but influenced also by the genotype of the challenge virus. We demonstrated that vaccination of SPF chicks with recombinant herpesvirus of turkey expressing the F-gene of genotype I ND virus (rHVT-ND) provided complete clinical protection against heterologous genotype VII.1.1 ND virus strain and reduced challenge virus shedding significantly. 100% of clinical protection was achieved already by 3 weeks of age, irrespective of the challenge route (intra-muscular or intra-nasal) and vaccination blocked cloacal shedding almost completely. Interestingly, oro-nasal shedding was different in the two challenge routes: less efficiently controlled following intra-nasal than intra-muscular challenge. Differences in the shedding pattern between the two challenge routes indicate that rHVT-ND vaccine induces strong systemic immunity, that is capable to control challenge virus dissemination in the body (no cloacal shedding), even when it is a heterologous strain, but less efficiently, although highly significantly (p < 0.001) suppresses the local replication of the challenge virus in the upper respiratory mucosa and consequent oro-nasal shedding.

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

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

Protective efficacy of inactivated Newcastle disease virus vaccines prepared in two different oil-based adjuvants

Despite the availability of Newcastle disease (ND) vaccines for more than six decades, disease outbreaks continue to occur with huge economic consequences to the global poultry industry. The aim of this study is to develop a safe and effective inactivated vaccine based on a recently isolated Newcastle disease virus (NDV) strain IBS025/13 and evaluate its protective efficacy in chicken following challenge with a highly virulent genotype VII isolate. Firstly, high titre of IBS025/13 was exposed to various concentrations of binary ethylenimine (BEI) to determine the optimal conditions for complete inactivation of the virus. The inactivated virus was then prepared in form of a stable water-in-oil emulsion of black seed oil (BSO) or Freund’s incomplete adjuvant (FIA) and used as vaccines in specific pathogen-free chicken. Efficacy of various vaccine preparations was also evaluated based on the ability of the vaccine to protect against clinical disease, mortality and virus shedding following challenge with highly virulent genotype\VII NDV isolate. The results indicate that exposure of NDV IBS025/13 to 10 mM of BEI for 21 h at 37 °C could completely inactivate the virus without tempering with the structural integrity of the viral hemagglutin-neuraminidase protein. More so, the inactivated vaccines adjuvanted with either BSO- or FIA-induced high hemagglutination inhibition antibody titre that protected the vaccinated birds against clinical disease and in some cases virus shedding, especially when used together with live attenuated vaccines. Thus, genotype VII-based NDV-inactivated vaccines formulated in BSO could substantially improve poultry disease control particularly when combined with live attenuated vaccines.

The 3D8 single chain variable fragment protein suppresses Newcastle disease virus transmission in transgenic chickens

Background

The 3D8 single chain variable fragment (scFv) is a mini-antibody sequence that exhibits independent nuclease activity against all types of nucleic acids. In this research, crossing a 3D8 scFv G1 transgenic rooster with wild-type hens produced 3D8 scFv G₂ transgenic chickens to evaluate suppression of viral transmission.

Result

The transgenic chickens were identified using genomic PCR and immunohistochemistry. To evaluate Newcastle disease virus (NDV) protection conferred by 3D8 scFv expression, transgenic, non-transgenic, and specific pathogen-free (SPF) chickens were challenged with virulent NDV by direct injection or aerosol exposure. The three groups of chickens showed no significant differences (p < 0.05) in mean death time after being directly challenged with NDV; however, in contrast to chickens in the non-transgenic and SPF groups, chickens in the transgenic group survived after aerosol exposure. Although the transgenic chickens did not survive after direct challenge, we found that the chickens expressing the 3D8 scFv survived aerosol exposure to NDV.

Conclusions

Our finding suggest that the 3D8 scFv could be a useful tool to prevent chickens from spreading NDV and control virus transmission.

Identification of optimal sample collection devices and sampling locations for the detection of environmental viral contamination in wire poultry cages

Environmental testing of poultry premises after an outbreak of an infectious disease like avian influenza (AI) or Newcastle disease is essential to promptly verify virus‐free status and subsequently return to normal operations. In an attempt to establish an optimized sampling protocol, a laboratory study simulating an AI virus‐contaminated poultry house with wire layer cages was conducted. Three sample collection devices, pre‐moistened cotton gauze, dry cotton gauze and a foam swab, were evaluated with each of four sample locations within a cage and when sampling all four locations with one device. Virus was detected with quantitative real‐time RT‐PCR utilizing a standard curve of a quantified homologous isolate of AI virus to determine titre equivalents of virus. The pre‐moistened gauze detected the most virus RNA (100% positive, geometric mean titre [GMT): 3.2 log₁₀ 50% embryo infectious doses [EID₅₀] equivalents per 25 cm²) in all four sample locations compared to dry gauze (93% positive, GMT: 2.6 EID₅₀ equivalents per 25 cm²) and foam swabs (95% positive, GMT: 2.8 log10 EID₅₀ equivalents per 25 cm²). The highest viral RNA loads were observed from the cage floor, and when the four locations were sampled with the same device. Overall, the pre‐moistened gauze performed the best, and sampling multiple locations within a cage with the same device would likely optimize detection of residual virus.

Protection conferred by commercial NDV live attenuated and double recombinant HVT vaccines against virulent California 2018 Newcastle disease virus (NDV) in chickens

Vaccines against virulent Newcastle disease virus (NDV) are widely available and can be protective, but improved vaccination protocols are needed to prevent clinical disease and reduce virus circulation. The present study evaluated the efficacy of two commercial vaccines alone or in combination: a live attenuated NDV vaccine (LV) and a recombinant herpesvirus of turkeys vector expressing the fusion protein of NDV and the virus protein 2 of infectious bursal disease virus (rHVT-ND-IBD). Chickens were vaccinated with one of four vaccination protocols: live vaccine (LV) at 1 and 11 days of age (DOA), rHVT ND-IBD and LV at 1 DOA, rHVT ND-IBD at 1 DOA boosted with an LV at 11 DOA, and rHVT ND-IBD at 1 DOA. The vaccinated birds were challenged at different time points (3 or 4 weeks of age) with the California 2018 virus. The mortality, clinical signs, mean death time (MDT), humoral response before and after vaccination, and virus shedding after challenge were evaluated. All vaccination protocols were able to prevent mortality, reduce virus shedding, and induce antibody levels before the challenge at 3 and 4 weeks-old. Overall, the antibody levels before the challenge at 4 weeks were significantly higher in all groups vaccinated with the rHVT ND-IBD when compared to levels in 3 week old birds. The combination of recombinant rHVT ND-IBD with a live vaccine at one-day-old seems to be a better combination, due to the absence of clinical signs, higher antibody levels pre and post-challenge, and reduced virus shedding at any time point after the challenge at 3 or 4 weeks of age with the California 2018 virus.

Development of an Effective and Stable Genotype-Matched Live Attenuated Newcastle Disease Virus Vaccine Based on a Novel Naturally Recombinant Malaysian Isolate Using Reverse Genetics

Genotype VII Newcastle disease viruses are associated with huge economic losses in the global poultry industry. Despite the intensive applications of vaccines, disease outbreaks caused by those viruses continue to occur frequently even among the vaccinated poultry farms. An important factor in the suboptimal protective efficacy of the current vaccines is the genetic mismatch between the prevalent strains and the vaccine strains. Therefore, in the present study, an effective and stable genotype-matched live attenuated Newcastle disease virus (NDV) vaccine was developed using reverse genetics, based on a recently isolated virulent naturally recombinant NDV IBS025/13 Malaysian strain. First of all, the sequence encoding the fusion protein (F) cleavage site of the virus was modified in silico from virulent polybasic (RRQKRF) to avirulent monobasic (GRQGRL) motif. The entire modified sequence was then chemically synthesized and inserted into pOLTV5 transcription vector for virus rescue. A recombinant virus termed mIBS025 was successfully recovered and shown to be highly attenuated based on OIE recommended pathogenicity assessment indices. Furthermore, the virus was shown to remain stably attenuated and retain the avirulent monobasic F cleavage site after 15 consecutive passages in specific-pathogen-free embryonated eggs and 12 passages in one-day-old chicks. More so, the recombinant virus induced a significantly higher hemagglutination inhibition antibody titre than LaSota although both vaccines fully protected chicken against genotype VII NDV induced mortality and morbidity. Finally, mIBS025 was shown to significantly reduce both the duration and quantity of cloacal and oropharyngeal shedding of the challenged genotype VII virus compared to the LaSota vaccine. These findings collectively indicate that mIBS025 provides a better protective efficacy than LaSota and therefore can be used as a promising vaccine candidate against genotype VII NDV strains.

Reverse Genetics Assembly of Newcastle Disease Virus Genome Template Using Asis-Sal-Pac BioBrick Strategy

Background

The BioBrick construction as an approach in synthetic biology provides the ability to assemble various gene fragments. To date, different BioBrick strategies have been exploited for assembly and cloning of a variety of gene fragments. We present a new BioBrick strategy, here referred as Asis-Sal-Pac BioBrick, which we used for the assembly of NDV as a candidate for single-stranded non-segmented, negative-sense RNA genome viruses.

Results

In the present study, we isolated three NDVs from clinical samples which were classified into the VIId genotype based on their pathogenicity and phylogenetic analyses. Then, SalI, AsisI, and PacI enzymes were used to design and develop a novel BioBrick strategy, which enabled us to assemble the NDV genome, adopting the “rule of six”. In this method, in each assembly step, the restriction sites in the newly formed destination plasmid are reproduced, which will be used for the next insertion. In this study using two overlapping PCRs, the cleavage site of the F gene was also modified from ¹¹²RRQKRF¹¹⁷to ¹¹²GRQGRL¹¹⁷ in order to generate the attenuated recombinant NDV. Finally, in order to construct the recombinant NDV viruses, the plasmids harboring the assembled full-length genome of the NDV and the helper plasmids were co-transfected into T7-BHK cells. The rescue of the recombinant NDVwas confirmed by RT-PCR and HA tests.

Conclusions

These findings suggest that the combination of reverse genetic technology and BioBrick assembly have the potential to be applied for the development of novel vaccine candidates. This promising strategy provides an effective and reliable approach to make genotype-matched vaccines against specific NDV strains or any other virus.

Generation and evaluation of a vaccine candidate of attenuated and heat-resistant genotype VIII Newcastle disease virus

Newcastle disease, which is a highly contagious and fatal disease caused by the Newcastle disease virus (NDV), has harmed the poultry industry for decades. The administration of effective vaccines can control most outbreaks and epidemics of Newcastle disease in the world. However, vaccination failures of live attenuated vaccines becasue of storage and transportation problems have been reported. Hence, thermostable live vaccine strains, such as V4 and I-2 strains, are being used and welcomed in tropical regions such as Africa and Southeast Asia. In this study, a thermostable, attenuated vaccine candidate strain NDV/rHR09 was generated using the genotype VIII heat-resistant virulent NDV strain HR09 by the reverse genetics system. The results of the determination of the mean death time and intracerebral pathogenicity index indicated that NDV/rHR09 is lentogenic even after 15 serial passages in embryonated chicken eggs. The thermostability assessment showed that the NDV/rHR09 strain exhibited hemagglutination activity and infectivity when exposed to 56°C for 60 min. Compared with the commercially available La Sota and V4 vaccines, the NDV/rHR09 induced higher antibody titers in specific pathogen-free chickens. In addition, NDV/rHR09 conferred complete protection against virulent genotype VII NDV challenge and virus shedding from vaccinated chickens. These results suggest that NDV/rHR09 is a promising thermostable vaccine candidate strain.

Comparison of the Impact of Different Administration Routes on the Efficacy of a Thermoresistant Newcastle Disease Vaccine in Chickens

Route of vaccine administration has a great impact on immunization and protection outcomes in chickens. This study was conducted to compare the effect of different administration routes on the efficacy of a thermoresistant Newcastle disease (ND) vaccine (ND.TR.IR) in chickens. A total of 100 one-day-old specific pathogen-free chicks were divided into five groups (n = 20 chicks per group) and vaccinated through different routes at 10 and 20 days of age. Treatments included no vaccination (control [C]), 1 dose inoculation through eye drop (ED), 1 dose inoculation through drinking water (DW), 1 dose inoculation through feed (FV₁), and 10 doses inoculation through feed (FV₁₀). At 20 and 34 days of age, antibody titers were measured against ND virus (NDV) in all the chickens by hemagglutination inhibition (HI) test. Chicks immunized with ND.TR.IR vaccine through different routes of administration also were intramuscularly challenged with a local virulent NDV (vNDV) (Ck/ir/Beh/2011) 14 days after booster vaccination (at 34 days of age). Our results showed that in comparison with the FVs groups, the immunized chicks through ED induced a higher HI antibody titers at 20 days of age (p < 0.05). Meanwhile, vaccination through ED induced higher HI antibody titers at day 34 of age compared with all other groups (p > 0.05). The percentages of the protective HI antibody titers (≥log₂³) detected in ED and DW groups at 20 days of age were higher than those detected in the FV₁ group (p < 0.05). However, routes of vaccination had no significant effect on the rate of protective titers at day 34 of age (100%, 90%, 75%, and 85% for ED, DW, FV₁, and FV₁₀, respectively). The percentage of post-NDV challenge survived chickens was not affected by the route of vaccination (p > 0.05), but immunization of chicks with ND.TR.IR in FV₁ group provided relatively poorer protection when compared with the other groups (90% vs. 100%, respectively). Altogether, immunization of chicks with ND.TR.IR vaccine through different routes of administration induced protective NDV antibody HI titers, and provided protection against vNDV. However, when the vaccine was administrated through feed, a higher dose of vaccine is recommended.

Preparation of the inactivated Newcastle disease vaccine by plasma activated water and evaluation of its protection efficacy

Vaccination has been regarded as the most effective way to reduce death and morbidity caused by infectious diseases in the livestock industry. In this study, plasma activated water (PAW) was introduced to prepare the inactivated Newcastle disease vaccine. Humoral immune response was tested by hemagglutination inhibition (HI) assay and enzyme-linked immunosorbent assay (ELISA). In addition, cell-mediated immune response was evaluated by lymphocyte proliferation assay and flow cytometry. The results demonstrated that the vaccine prepared by PAW at appropriate volume ratio could induce similar antibody titers in specific pathogen-free (SPF) chickens compared with the formaldehyde-inactivated vaccine. The challenge experiment further confirmed that the vaccine prepared by PAW conferred solid protection against virulent NDV. Moreover, it was found that the vaccine could promote the proliferation of lymphocytes and stimulate cell-mediated immunity of SPF chickens. Furthermore, analysis of electron spin resonance (ESR) spectroscopy and physicochemical properties of PAW suggested reactive oxygen and nitrogen species (RONS) played an essential role in the virus inactivation. Therefore, this study indicated that NDV treated by PAW in an appropriate ratio retained immunogenicity on the premise of virus inactivation. PAW as a promising strategy could be used to prepare inactivated vaccine for Newcastle disease.

Molecular and biological characterization of the immunological potency of Newcastle disease virus oil emulsion-inactivated vaccines prepared from field isolate obtained from vaccinated chickens outbreak

This study was conducted to characterize the immunological parameters of chickens vaccinated with two formulated inactivated vaccines, water in oil (WO) and water in oil in water (WOW), prepared from velogenic Newcastle disease virus (vNDV) genotype VIIj isolated from outbreak among vaccinated chickens. Six groups (G1-G6) of commercial broiler chickens were established (n = 20). The G1-G3 were received homologous (WO and WOW) and heterologous (LaSota) inactivated vaccines, respectively. The G4 was vaccinated with live heterologous (LaSota) vaccine, while G5 and G6 were kept as control positive and control negative non-vaccinated groups. The antibody titers were measured against vNDV and LaSota antigens using hemagglutination inhibition (HI) test, the cytokine gene expressions of IFNγ, IL1β, IL4, IL6, IL8, and IL18 were quantified using real-time RT-PCR, and the virus shedding was titrated on chicken embryo fibroblast cells after challenging by vNDV. The classical clinical signs and 100% mortality were observed only in G5 after vNDV challenging. The highest HI titers were detected in G1, G2, and G3 using NDV/168 antigen with no significant differences among them. These groups showed higher HI titer than G4 (2-4log2). Cytokine gene expression of IFNγ, IL1, IL6, IL8, and IL18 were significantly downregulated in vaccinated chickens with upregulation of IL4 than non-vaccinated challenge group. Viral shedding titers were significantly (0.0001, p ≤ 0.001) reduced in all samples form vaccinated chickens. In conclusion, the prepared vaccines produced highly efficient immunological responses and could be used for controlling the NDV infection.

Serological, clinical, and risk factors of the Newcastle disease on broilers flocks in Algeria

Aim:

The work aimed at studying the serological and clinical factors, as well as the risk factors of the Newcastle disease (ND) on broilers herds in Algeria.

Materials and Methods:

A sample of 1248 birds was randomly selected from 52 broiler flocks. We took blood samples from each bird at the level of the wing vein area where an indirect enzyme-linked immunosorbent assay technique was carried out through the use of an IDvet kit.

Results:

The flocks showed 82.69% of seroprevalence. Clinically speaking, the most common symptoms were sneezing, rale, greenish diarrhea, torticollis, and motor discords. Most commonly observed postmortem lesions were the proventriculitis, tracheitis, and enteritis. Especially, the caeca are hemorrhagic. The scores show the effect of risk factors. There was a significant effect on the mortality, the hygiene and vaccination groups on antibody titers in time 2. The antibody titers were elevated in the herd that recorded a high mortality (more than 10%) compared with those which recorded a low mortality (<10%) (p=0.002). Therefore, the antibody titers were elevated in herds with bad hygiene, compared with the ones with good hygiene (p=0.04). At last, when broiler chicken were not boosted by ND vaccine, flocks appeared to be more seropositive (p=0.02).

Conclusion:

The serological survey conducted in this study provided an important scope for ND as a dominant viral disease in broilers. Many factors are responsible for the onset of these diseases; correct biosecurity measures are needed to reduce the impact of this pathology in poultry farms.

Impact of single and mixed infections with Escherichia coli and Mycoplasma gallisepticum on Newcastle disease virus vaccine performance in broiler chickens: an in vivo perspective

AIMS

This study was designed to investigate, in an in vivo setting, the effects of single and combined infections with either Mycoplasma gallisepticum (MG) and/or Escherichia coli on the chicken immune response induced by Newcastle disease virus (NDV) vaccine.

METHODS AND RESULTS

Humoral immunity was measured through detection of NDV antibody and anti-NDV IgG titres using haemagglutination-inhibition test and enzyme-linked immunosorbent assay, respectively. In addition, the expression levels of pro-inflammatory cytokines' genes (interleukin (IL) 6, IL4 and interferon (IFN) γ) were analysed using quantitative reverse transcription PCR. Significant (P < 0·05) results in all immunological parameters were detected in the vaccinated noninfected chicken group in comparison with those in groups exposed to bacterial infections. Bacterial infection along with vaccination hampered the NDV antibodies production and reduced the vaccine upregulated cytokine genes. The vaccinated mixed infection group reported lower antibody titres and cytokines expression levels compared to those in the single infection groups. All the previously enhanced immunological parameters reflected the maximum protection post challenge with velogenic viscerotropic NDV in the vaccinated noninfected chicken group.

CONCLUSIONS

These findings provide novel insights into the immunosuppression activities of MG and E. coli infection in chickens vaccinated against NDV.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study hopes to provide a better insight to the immunosuppressive action of bacterial pathogens in chickens. This will help to improve biosecurity strategies during NDV vaccination in the future.

The enhanced immunological activity of Paulownia tomentosa flower polysaccharide on Newcastle disease vaccine in chicken

The extracts of Paulownia tomentosa (P. tomentosa) exhibit multiple pharmacological activities. In the present study, P. tomentosa flower polysaccharides (PTFP) were extracted by water decoction and ethanol precipitation, and the immunologic modulations of PTFP against Newcastle disease (ND) vaccine was investigated in chickens. The results showed that in a certain range of concentrations, PTFP treatment can dose-dependently enhance lymphocyte proliferation. Then, 280 14-days-old chickens were randomly divided into seven groups, and vaccinated with ND vaccine except blank control (BC) group. At the first vaccination, chickens were orally administrated with PTFP at concentration ranging from 0 to 50 mg/kg once a day for 3 successive days, and the BC group was treated with physiological saline. The lymphocyte proliferation rate, serum antibody titer, and levels of interferon-γ (IFN-γ) were respectively measured on 7, 14, 21, and 28 days after the first vaccination. The results showed that PTFP at the suitable doses could significantly promote lymphocyte proliferation, enhance serum antibody titer, and improve serum IFN-γ concentrations. Taken together, these data indicated that PTFP could improve the immune efficacy against ND vaccine in chickens, and could be as the candidate of a new-type immune adjuvant.

Pathogenicity and transmission of virulent Newcastle disease virus from the 2018-2019 California outbreak and related viruses in young and adult chickens

In May of 2018, virulent Newcastle disease virus was detected in sick, backyard, exhibition chickens in southern California. Since, the virus has affected 401 backyard and four commercial flocks, and one live bird market in California, and one backyard flock in Utah. The pathogenesis and transmission potential of this virus, along with two genetically related and widely studied viruses, chicken/California/2002 and chicken/Belize/2008, were evaluated in both 3-week- and 62-week-old chickens given a low, medium, or high challenge dose. All three viruses were highly virulent causing clinical signs, killing all the chickens in the medium and high dose groups, and efficiently transmitting to contacts. The three viruses also replicated in the reproductive tract of the adult hens. Virus shedding for all viruses was detected 24 hours after challenge, peaking with high titers at day 4 post challenge. Although not genetically identical, the studied isolates were shown to be phenotypically very similar, which allows the utilization of the available literature in the control of the current outbreak.

Epidemiology, control, and prevention of Newcastle disease in endemic regions: Latin America

Newcastle disease (ND) infects wild birds and poultry species worldwide, severely impacting the economics of the poultry industry. ND is especially problematic in Latin America (Mexico, Colombia, Venezuela, and Peru) where it is either endemic or re-emerging. The disease is caused by infections with one of the different strains of virulent avian Newcastle disease virus (NDV), recently renamed Avian avulavirus 1. Here, we describe the molecular epidemiology of Latin American NDVs, current control and prevention methods, including vaccines and vaccination protocols, as well as future strategies for control of ND. Because the productive, cultural, economic, social, and ecological conditions that facilitate poultry endemicity in South America are similar to those in the developing world, most of the problems and control strategies described here are applicable to other continents.

Establishment of xMAP for the simultaneous detection of antibodies to Newcastle disease virus and avian influenza virus

Using Luminex xMAP (x = analyte, MAP = multi-analyte profiling) technology, a serological method for the simultaneous detection of antibodies to Newcastle disease virus (NDV) and avian influenza virus (AIV) was established. Nano-magnetic beads coated with purified NDV protein and AIV nucleoprotein were incubated with serum samples. Using biotinylated rabbit anti-chicken IgY and streptavidin-R-phycoerythrin, the optical signals measured by a Luminex 200 detection system indicated the quantification of NDV or AIV antibodies in the serum. Specific pathogen-free (SPF) chicken serum was used as a negative control. The Luminex xMAP assay developed in this study demonstrated high specificity as there was no cross-reaction with antibodies to infectious laryngotracheitis virus, infectious bronchitis virus, infectious bursal disease virus, avian leukosis virus, and Marek's disease virus. The results from reproducibility experiments showed that intra-coefficients of variation were 3.36 and 9.23% and inter-coefficients of variation were 6.50 and 7.66% for NDV and AIV, respectively. The results also indicated that the Luminex xMAP assay was 16 times more sensitive for NDV antibody detection and 1,024 times more sensitive for AIV antibody detection compared to the enzyme-linked immunosorbent assay (ELISA). A total of 300 chicken serum samples were subjected to both Luminex xMAP assay and ELISA, showing the coincidence rates of 98.67 and 98% for NDV and AIV antibody detection, respectively. This study provides a new method for the simultaneous detection NDV and AIV antibodies in the serum with high specificity and sensitivity.

Truncated chicken MDA5 enhances the immune response to inactivated NDV vaccine

Melanoma Differentiation-Associated protein 5 (MDA5) is a cytoplasmic sensor for viral invasion and plays an important role in regulation of the immune response against Newcastle disease virus (NDV) in chickens. MDA5 was used as an adjuvant to enhance the humoral immune response against influenza virus. In the current study, truncated chicken MDA5 [1-483 aa, chMDA5(483aa)] expressed by recombinant adenovirus was administered to specific-pathogen-free (SPF) chickens to improve the immune response induced by inactivated NDV vaccine. A total of 156 SPF chickens were divided into six groups, and after two rounds of immunization, the humoral immune response, cell-mediated immune (CMI) response and the protective efficacy of the vaccines against NDV challenge were evaluated. The results showed that co-administration of chMDA5(483aa) expressed by adenovirus increased the NDV-specific antibody response by 1.7 times and chickens received chMDA5(483aa) also gained a higher level of CMI response. Consistently, the protective efficacy of the inactivated NDV vaccine against virulent NDV (vNDV) challenge was improved by co-administrate with chMDA5(483aa), as indicated by the reduced morbidity and pathological lesions, lower levels of viral load in organs and reduced virus shedding. Our study demonstrated that chMDA5(433aa) expressed by adenovirus could enhance the immune efficacy of inactivated NDV vaccine in chickens and could be a potential adjuvant candidate in developing chicken NDV vaccines.

Maternal antibody inhibition of recombinant Newcastle disease virus vectored vaccine in a primary or booster avian influenza vaccination program of broiler chickens

Maternally-derived antibodies (MDA) provide early protection from disease, but may interfere with active immunity in young chicks. In highly pathogenic avian influenza virus (HPAIV)-enzootic countries, broiler chickens typically have MDA to Newcastle disease virus (NDV) and H5 HPAIV, and their impact on active immunity from recombinant vectored vaccines is unclear. We assessed the effectiveness of a spray-applied recombinant NDV vaccine with H5 AIV insert (rNDV-H5) and a recombinant turkey herpesvirus (HVT) vaccine with H5 AIV insert (rHVT-H5) in commercial broilers with MDA to NDV alone (MDA:AIV^-NDV⁺) or to NDV plus AIV (MDA:AIV⁺NDV⁺) to provide protection against homologous HPAIV challenge. In Experiment 1, chicks were spray-vaccinated with rNDV-H5 at 3 weeks (3w) and challenged at 5 weeks (5w). All sham-vaccinated progeny lacked AIV antibodies and died following challenge. In rNDV-H5 vaccine groups, AIV and NDV MDA had completely declined to non-detectable levels by vaccination, enabling rNDV-H5 spray vaccine to elicit a protective AIV antibody response by 5w, with 70-78% survival and significant reduction of virus shedding compared to shams. In Experiment 2, progeny were vaccinated with rHVT-H5 and rNDV-H5 at 1 day (1d) or 3w and challenged at 5w. All sham-vaccinated progeny lacked AIV antibodies and died following challenge. In rHVT-H5(1d) vaccine groups, irrespective of rNDV-H5(3w) boost, AIV antibodies reached protective levels pre-challenge, as all progeny survived and virus shedding significantly decreased compared to shams. In contrast, rNDV-H5-vaccinated progeny had AIV and/or NDV MDA at the time of vaccination (1d and/or 3w) and failed to develop a protective immune response by 5w, resulting in 100% mortality after challenge. Our results demonstrate that MDA to AIV had minimal impact on the effectiveness of rHVT-H5, but MDA to AIV and/or NDV at the time of vaccination can prevent development of protective immunity from a primary or booster rNDV-H5 vaccine.

Preparing for a Foreign Animal Disease Outbreak Using a Novel Tabletop Exercise

IntroductionForeign animal disease (FAD) outbreaks can have devastating impacts, but they occur infrequently in any specific sector anywhere in the United States (US). Training to proactively discuss implementation of control and prevention strategies are beneficial in that they provide stakeholders with the practical information and educational experience they will need to respond effectively to an FAD. Such proactive approaches are the mission of the Secure Food System (SFS; University of Minnesota; St. Paul, Minnesota USA).

METHODS

The SFS exercises were designed as educational activities based on avian influenza (AI) outbreaks in commercial poultry scenarios. These scenarios were created by subject matter experts and were based on epidemiology reports, risk pathway analyses, local industry practices, and site-specific circumstances. Target audiences of an exercise were the groups involved in FAD control: animal agriculture industry members; animal health regulators; and diagnosticians. Groups of industry participants seated together at tables represented fictional poultry premises and were guided by a moderator to respond to an on-farm situation within a simulated outbreak. The impact of SFS exercises was evaluated through interviews with randomized industry participants and selected table moderators. Descriptive statistics and qualitative analyses were performed on interview feedback.

RESULTS

Eleven SFS exercises occurred from December 2016 through October 2017 in multiple regions of the US. Exercises were conducted as company-wide, state-wide, or regional trainings. Nine were based on highly pathogenic avian influenza (HPAI) outbreaks and two focused on outbreaks of co-circulating HPAI and low pathogenicity avian influenza (LPAI). Poultry industry participants interviewed generally found attending an SFS exercise to be useful. The most commonly identified benefits of participation were its value to people without prior outbreak experience and knowledge gained about Continuity of Business (COB)-permitted movement. After completing an exercise, most participants evaluated their preparedness to respond to an outbreak as somewhat to very ready, and more than one-half reported their respective company or farms had discussions or changed actions due to participation.

CONCLUSION

Evaluation feedback suggests the SFS exercises were an effective training method to supplement preparedness efforts for an AI outbreak. The concept of using multi-faceted scenarios and multiple education strategies during a tabletop exercise may be translatable to other emergency preparedness needs. LinskensEJ, NeuAE, WalzEJ, St. CharlesKM, CulhaneMR, SsematimbaA, GoldsmithTJ, HalvorsonDA, CardonaCJ. Preparing for a foreign animal disease outbreak using a novel tabletop exercise. Prehosp Disaster Med. 2018;33(6):640-646.

Newcastle Disease Virus-Based Vectored Vaccine against Poliomyelitis

The poliovirus eradication initiative has spawned global immunization infrastructure and dramatically decreased the prevalence of the disease, yet the original virus eradication goal has not been met. The suboptimal properties of the existing vaccines are among the major reasons why the program has repeatedly missed eradication deadlines. Oral live poliovirus vaccine (OPV), while affordable and effective, occasionally causes the disease in the primary recipients, and the attenuated viruses rapidly regain virulence and can cause poliomyelitis outbreaks. Inactivated poliovirus vaccine (IPV) is safe but expensive and does not induce the mucosal immunity necessary to interrupt virus transmission. While the need for a better vaccine is widely recognized, current efforts are focused largely on improvements to the OPV or IPV, which are still beset by the fundamental drawbacks of the original products. Here we demonstrate a different design of an antipoliovirus vaccine based on in situ production of virus-like particles (VLPs). The poliovirus capsid protein precursor, together with a protease required for its processing, are expressed from a Newcastle disease virus (NDV) vector, a negative-strand RNA virus with mucosal tropism. In this system, poliovirus VLPs are produced in the cells of vaccine recipients and are presented to their immune systems in the context of active replication of NDV, which serves as a natural adjuvant. Intranasal administration of the vectored vaccine to guinea pigs induced strong neutralizing systemic and mucosal antibody responses. Thus, the vectored poliovirus vaccine combines the affordability and efficiency of a live vaccine with absolute safety, since no full-length poliovirus genome is present at any stage of the vaccine life cycle.IMPORTANCE A new, safe, and effective vaccine against poliovirus is urgently needed not only to complete the eradication of the virus but also to be used in the future to prevent possible virus reemergence in a postpolio world. Currently, new formulations of the oral vaccine, as well as improvements to the inactivated vaccine, are being explored. In this study, we designed a viral vector with mucosal tropism that expresses poliovirus capsid proteins. Thus, poliovirus VLPs are produced in vivo, in the cells of a vaccine recipient, and are presented to the immune system in the context of vector virus replication, stimulating the development of systemic and mucosal immune responses. Such an approach allows the development of an affordable and safe vaccine that does not rely on the full-length poliovirus genome at any stage.