Newcastle disease virus-based H5 influenza vaccine protects chickens from lethal challenge with a highly pathogenic H5N2 avian influenza virus

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

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

Rescue of Recombinant Newcastle Disease Virus Expressing Heterologous Genes

Reverse genetics allows for the generation of recombinant infectious viruses from viral sequences or complete viral genomes cloned into plasmids. Using reverse genetics, it is then possible to introduce changes in the genome of infectious viruses for multiple applications.Newcastle disease virus (NDV) is a non-segmented, negative-sense RNA virus that has been amenable to manipulation by reverse genetics for more than two decades. Since then, recombinant NDVs have been extensively used as viral vectors to express heterologous proteins. We describe the key steps required to design and introduce an additional transcription unit in the genome of the Newcastle disease virus for the efficient expression of a heterologous gene.

Negative-Strand RNA Virus-Vectored Vaccines

Vectored RNA vaccines offer a variety of possibilities to engineer targeted vaccines. They are cost-effective and safe, but replication competent, activating the humoral as well as the cellular immune system.This chapter focuses on RNA vaccines derived from negative-strand RNA viruses from the order Mononegavirales with special attention to Newcastle disease virus-based vaccines and their generation. It shall provide an overview on the advantages and disadvantages of certain vector platforms as well as their scopes of application, including an additional section on experimental COVID-19 vaccines.

Vaccination of Poultry Against Influenza

The complexity of influenza A virus (IAV) infections in avian hosts leads to equally complex scenarios for the vaccination of poultry. Vaccination against avian influenza strains can be used to prevent infections from sources with a single strain of IAV. It has been used as a part of outbreak control strategies as well as a way to maintain production for both low and high pathogenicity outbreaks. Unlike other viral pathogens of birds, avian influenza vaccination when used against highly pathogenic avian influenza virus, is tied to international trade and thus is not freely available for use without specific permission.

Viral vectored vaccines: design, development, preventive and therapeutic applications in human diseases

Human diseases, particularly infectious diseases and cancers, pose unprecedented challenges to public health security and the global economy. The development and distribution of novel prophylactic and therapeutic vaccines are the prioritized countermeasures of human disease. Among all vaccine platforms, viral vector vaccines offer distinguished advantages and represent prominent choices for pathogens that have hampered control efforts based on conventional vaccine approaches. Currently, viral vector vaccines remain one of the best strategies for induction of robust humoral and cellular immunity against human diseases. Numerous viruses of different families and origins, including vesicular stomatitis virus, rabies virus, parainfluenza virus, measles virus, Newcastle disease virus, influenza virus, adenovirus and poxvirus, are deemed to be prominent viral vectors that differ in structural characteristics, design strategy, antigen presentation capability, immunogenicity and protective efficacy. This review summarized the overall profile of the design strategies, progress in advance and steps taken to address barriers to the deployment of these viral vector vaccines, simultaneously highlighting their potential for mucosal delivery, therapeutic application in cancer as well as other key aspects concerning the rational application of these viral vector vaccines. Appropriate and accurate technological advances in viral vector vaccines would consolidate their position as a leading approach to accelerate breakthroughs in novel vaccines and facilitate a rapid response to public health emergencies.

Mucosal delivery of RNA vaccines by Newcastle disease virus vectors

The rapid evolution of SARS-CoV-2 since its pandemic outbreak has underscored the need for improved SARS-CoV-2 vaccines that efficiently reduce not only hospitalizations and deaths, but also infections and transmission. This might be achieved by a new generation of intranasally administered SARS-CoV-2 vaccines to stimulate protective mucosal immunity. Among all different approaches, preclinical and clinical information using Newcastle Disease Virus (NDV)-vectors expressing S of SARS-CoV2 as a COVID-19 vaccine show the potential of this vaccine platform as an affordable, highly immunogenic, safe strategy to intranasally vaccinate humans against SARS-CoV-2 and other infectious diseases. These vaccine vectors consist on the use of a harmless avian negative strand RNA virus to deliver intranasally a self-replicating RNA expressing the vaccine antigen in the cells of the respiratory mucosa. The vector also incorporates the antigen in the virus particle used for RNA delivery, thus combining the properties of nanoparticle-based and RNA-based vaccines. Other advantages of NDV-based vectors include the worldwide availability of manufacturing facilities for their production and their stability at non-freezing temperatures. While phase 3 clinical studies to evaluate efficacy are still pending, phase 1 and 2 clinical studies have demonstrated the safety and immunogenicity of NDV-S vaccines against SARS-CoV-2.

Intranasal vaccination of hamsters with a Newcastle disease virus vector expressing the S1 subunit protects animals against SARS-CoV-2 disease

The coronavirus disease-19 (COVID-19) pandemic has already claimed millions of lives and remains one of the major catastrophes in the recorded history. While mitigation and control strategies provide short term solutions, vaccines play critical roles in long term control of the disease. Recent emergence of potentially vaccine-resistant and novel variants necessitated testing and deployment of novel technologies that are safe, effective, stable, easy to administer, and inexpensive to produce. Here we developed three recombinant Newcastle disease virus (rNDV) vectored vaccines and assessed their immunogenicity, safety, and protective efficacy against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in mice and hamsters. Intranasal administration of rNDV-based vaccine candidates elicited high levels of neutralizing antibodies. Importantly, the nasally administrated vaccine prevented lung damage, and significantly reduced viral load in the respiratory tract of vaccinated animal which was compounded by profound humoral immune responses. Taken together, the presented NDV-based vaccine candidates fully protected animals against SARS-CoV-2 challenge and warrants evaluation in a Phase I human clinical trial as a promising tool in the fight against COVID-19.

Development and Scalable Production of Newcastle Disease Virus-Vectored Vaccines for Human and Veterinary Use

The COVID-19 pandemic has highlighted the need for efficient vaccine platforms that can rapidly be developed and manufactured on a large scale to immunize the population against emerging viruses. Viral-vectored vaccines are prominent vaccine platforms that have been approved for use against the Ebola virus and SARS-CoV-2. The Newcastle Disease Virus is a promising viral vector, as an avian paramyxovirus that infects poultry but is safe for use in humans and other animals. NDV has been extensively studied not only as an oncolytic virus but also a vector for human and veterinary vaccines, with currently ongoing clinical trials for use against SARS-CoV-2. However, there is a gap in NDV research when it comes to process development and scalable manufacturing, which are critical for future approved vaccines. In this review, we summarize the advantages of NDV as a viral vector, describe the steps and limitations to generating recombinant NDV constructs, review the advances in human and veterinary vaccine candidates in pre-clinical and clinical tests, and elaborate on production in embryonated chicken eggs and cell culture. Mainly, we discuss the existing data on NDV propagation from a process development perspective and provide prospects for the next steps necessary to potentially achieve large-scale NDV-vectored vaccine manufacturing.

Avian Orthoavulavirus Type-1 as Vaccine Vector against Respiratory Viral Pathogens in Animal and Human

Avian orthoavulaviruses type-1 (AOaV-1) have recently transitioned from animal vaccine vector to a bona fide vaccine delivery vehicle in human. Owing to induction of robust innate and adaptive immune responses in mucus membranes in both birds and mammals, AOaVs offer an attractive vaccine against respiratory pathogens. The unique features of AOaVs include over 50 years of safety profile, stable expression of foreign genes, high infectivity rates in avian and mammalian hosts, broad host spectrum, limited possibility of recombination and lack of pre-existing immunity in humans. Additionally, AOaVs vectors allow the production of economical and high quantities of vaccine antigen in chicken embryonated eggs and several GMP-grade mammalian cell lines. In this review, we describe the biology of AOaVs and define protocols to manipulate AOaVs genomes in effectively designing vaccine vectors. We highlighted the potential and established portfolio of AOaV-based vaccines for multiple respiratory and non-respiratory viruses of veterinary and medical importance. We comment on the limitations of AOaV-based vaccines and propose mitigations strategies. The exploitation of AOaVs vectors is expanding at an exciting pace; thus, we have limited the scope to their use as vaccines against viral pathogens in both animals and humans.

Live Recombinant NDV-Vectored H5 Vaccine Protects Chickens and Domestic Ducks From Lethal Infection of the Highly Pathogenic H5N6 Avian Influenza Virus

The H5 subtype highly pathogenic avian influenza virus (HPAIV) has been introduced to South Korea every 2 or 3 years via wild migratory waterfowls, causing devastating damages to the poultry industry. Although most damages and economic losses by HPAIV are focused on chicken layers, domestic ducks are known to play a major role in the farm-to-farm transmission. However, most HPAIV vaccine studies on poultry have been performed with oil-emulsion inactivated vaccines. In this study, we developed a live recombinant Newcastle disease virus (NDV)-vectored vaccine against H5 HPAIV (rK148/ES2-HA) using a previously established NDV vaccine strain (K148/08) isolated from a wild mallard duck. The efficacy of the vaccine when administered via the oculonasal route or as a spray was evaluated against lethal H5 HPAIV infection in domestic ducks and chickens. Oculonasal inoculation of the rK148/ES2-HA in chickens and ducks elicited antibody titers against HPAIV as early as 1 or 2 week after the single dose of vaccination, whereas spray vaccination in ducks elicited antibodies against HPAIV after the booster vaccination. The chickens and ducks vaccinated with rK148/ES2-HA showed high survival rates and low viral shedding after H5N6 HPAIV challenge. Collectively, vaccination with rK148/ES2-HA prevented lethal infection and decreased viral shedding in both chickens and ducks. The vaccine developed in this study could be useful in suppressing the viral shedding in H5 HPAIV outbreaks, with the ease of vaccine application and fast onset of immunity.

Mathematical modeling of bird flu with vaccination and treatment for the poultry farms

A deterministic six-compartmental model was developed based on the progression of the disease in poultry, the epidemiological status of the individuals, and intervention measures. The Runge-Kutta method is applied to calculate the variables of the system of equations of the proposed model. The evolution of the epidemic provides some results, such as reproduction number, vaccine efficiency, and antiviral treatment. Numerical results show that the outbreak sizes known as the infected curves increase and decrease with the vaccine limitation rate and treatment rate, respectively, for a specific transmission rate. The calculated results of the reproduction number indicate that avian influenza would spread when vaccine efficiency is less than 70%, and the primary reproduction number is greater than 1. Finally, the disease-free equilibrium of the model is found locally and globally asymptotically stable for R₀ < 1.

A Newcastle disease virus expressing a stabilized spike protein of SARS-CoV-2 induces protective immune responses

Rapid development of COVID-19 vaccines has helped mitigating SARS-CoV-2 spread, but more equitable allocation of vaccines is necessary to limit the global impact of the COVID-19 pandemic and the emergence of additional variants of concern. We have developed a COVID-19 vaccine candidate based on Newcastle disease virus (NDV) that can be manufactured at high yields in embryonated eggs. Here, we show that the NDV vector expressing an optimized spike antigen (NDV-HXP-S) is a versatile vaccine inducing protective antibody responses. NDV-HXP-S can be administered intramuscularly as inactivated vaccine or intranasally as live vaccine. We show that NDV-HXP-S GMP-produced in Vietnam, Thailand and Brazil is effective in the hamster model. Furthermore, we show that intramuscular vaccination with NDV-HXP-S reduces replication of tested variants of concerns in mice. The immunity conferred by NDV-HXP-S effectively counteracts SARS-CoV-2 infection in mice and hamsters.

Advances in Development and Application of Influenza Vaccines

Influenza A virus is one of the most important zoonotic pathogens that can cause severe symptoms and has the potential to cause high number of deaths and great economic loss. Vaccination is still the best option to prevent influenza virus infection. Different types of influenza vaccines, including live attenuated virus vaccines, inactivated whole virus vaccines, virosome vaccines, split-virion vaccines and subunit vaccines have been developed. However, they have several limitations, such as the relatively high manufacturing cost and long production time, moderate efficacy of some of the vaccines in certain populations, and lack of cross-reactivity. These are some of the problems that need to be solved. Here, we summarized recent advances in the development and application of different types of influenza vaccines, including the recent development of viral vectored influenza vaccines. We also described the construction of other vaccines that are based on recombinant influenza viruses as viral vectors. Information provided in this review article might lead to the development of safe and highly effective novel influenza vaccines.

Comparative safety and efficacy of two bivalent vaccines containing Newcastle disease LaSota and avian influenza H9N2 Sidrap isolate formulated with different oil adjuvants

Background and Aim:

Newcastle disease (ND) and avian influenza (AI) are two devastating diseases of poultry, which cause great economic losses to the poultry industry and disrupt food security in our country. The use of ND-AI inactive bivalent vaccine is very effective and economical to prevent and control ND and AI disease. Bivalent ND LaSota-AI H9N2 vaccine is not yet available in Indonesia. The inactivated vaccines used in poultry industry often require oil adjuvant to elicit a sufficient immune response. This study aimed to develop the bivalent inactive vaccines containing ND LaSota and AI H9N2 Sidrap isolate which are local isolates as poultry vaccine candidates, and formulated with two different commercial adjuvants, then compared.

Materials and Methods:

Two vaccines bivalent were prepared by emulsifying inactivated Newcastle disease virus (LaSota strain) and AI H9N2 Sidrap isolate viruses with Marcol white mineral oil and Montanide ISA70 adjuvants. Both of bivalent vaccines were tested for safety (physical and histopathological at the injection site) and efficacy in specific-pathogen-free chickens. Parameters used for the evaluation of the efficacy were immunogenicity by hemagglutination inhibition and protection percentage.

Results:

Both bivalent vaccines are safe to use. Post-vaccination (PV) immune response was observed using a hemagglutination inhibition test at 2, 3, 4, 5, 6, 7, and 8 weeks of PV. The bivalent vaccine B gives a better immune response to ND at 2, 3, and 4 weeks of PV (p<0.05) compared to the bivalent vaccine A, but in 5, 6, 7, and 8 weeks, the PV does not show differences in the immune response. The immune response to AI H9N2 showed differences at weeks 2 and 3 PV (p<0.05) with the bivalent vaccine B indicated higher immunity. A single immunization with both bivalent vaccines induces 100% protection in chickens that have been vaccinated against the deadly challenge with the virulent ND virus.

Conclusion:

Both of bivalent vaccines are safe to use and provide good efficacy against virulent ND viruses, but bivalent vaccine B (with Montanide ISA70 adjuvant) shows better immune response than bivalent vaccine A (Marcol white mineral oil adjuvant).

The immune enhancement effects of recombinant NDV expressing chicken granulocyte-macrophage colony-stimulating factor on the different avian influenza vaccine subtypes

Avian influenza is an acute and highly contagious infectious disease that is caused by the influenza virus. Avian influenza has been widely spread all over the world, has caused property loss and has threatened human life and security. In this study, the recombinant plasmid rClone30-chGM-CSF was constructed and rescued to the recombinant virus rClone30-chGM-CSF successfully. After 8 days of immunization with the recombinant virus, the titre of NDV HI (haemagglutination inhibition) antibodies in SPF chickens reached its peak. The average titre of the rClone30-chGM-CSF group reached 6 log2 and was significantly higher than the protection critical value of 4 log2 ; the titres of the rClone30 group and the blank group were 2.86 log2 and 1 log2 , respectively, indicating that the recombinant virus can effectively improve the NDV antibody titre. Then, SPF chickens were co-immunized with the recombinant virus and with three different vaccine subtypes of inactivated avian influenza. The results indicated that the SPF chickens that were immunized with the vaccine plus rClone30-chGM-CSF showed significantly higher avian influenza antibody levels than those in the single vaccine groups. Furthermore, the SPF chickens in the vaccine plus rClone30-chGM-CSF group elicited stronger CD4+ and CD8+ T-cell proliferative responses and also had upregulated transcriptional levels of interleukin-1β (IL-1β), IL-4, IL-6 and IL-17 compared with those in the single vaccine groups. This study has shown that the recombinant virus expressing chicken granulocyte-macrophage colony-stimulating factor (chGM-CSF) can be used not only as an NDV vaccine to effectively improve the titre of NDV antibodies but also as a biological adjuvant to enhance the immune effects of the avian influenza vaccine. Therefore, this recombinant virus can also be used as a biological adjuvant for other poultry vaccines.

Newcastle Disease Virus as a Vaccine Vector for 20 Years: A Focus on Maternally Derived Antibody Interference

It has been 20 years since Newcastle disease virus (NDV) was first used as a vector. The past two decades have witnessed remarkable progress in vaccine generation based on the NDV vector and optimization of the vector. Protective antigens of a variety of pathogens have been expressed in the NDV vector to generate novel vaccines for animals and humans, highlighting a great potential of NDV as a vaccine vector. More importantly, the research work also unveils a major problem restraining the NDV vector vaccines in poultry, i.e., the interference from maternally derived antibody (MDA). Although many efforts have been taken to overcome MDA interference, a lack of understanding of the mechanism of vaccination inhibition by MDA in poultry still hinders vaccine improvement. In this review, we outline the history of NDV as a vaccine vector by highlighting some milestones. The recent advances in the development of NDV-vectored vaccines or therapeutics for animals and humans are discussed. Particularly, we focus on the mechanisms and hypotheses of vaccination inhibition by MDA and the efforts to circumvent MDA interference with the NDV vector vaccines. Perspectives to fill the gap of understanding concerning the mechanism of MDA interference in poultry and to improve the NDV vector vaccines are also proposed.

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.

Innovation in Newcastle Disease Virus Vectored Avian Influenza Vaccines

Highly pathogenic avian influenza (HPAI) and Newcastle disease are economically important avian diseases worldwide. Effective vaccination is critical to control these diseases in poultry. Live attenuated Newcastle disease virus (NDV) vectored vaccines have been developed for bivalent vaccination against HPAI viruses and NDV. These vaccines have been generated by inserting the hemagglutinin (HA) gene of avian influenza virus into NDV genomes. In laboratory settings, several experimental NDV-vectored vaccines have protected specific pathogen-free chickens from mortality, clinical signs, and virus shedding against H5 and H7 HPAI viruses and NDV challenges. NDV-vectored H5 vaccines have been licensed for poultry vaccination in China and Mexico. Recently, an antigenically chimeric NDV vector has been generated to overcome pre-existing immunity to NDV in poultry and to provide early protection of poultry in the field. Prime immunization of one-day-old poults with a chimeric NDV vector followed by boosting with a conventional NDV vector has shown to protect broiler chickens against H5 HPAI viruses and a highly virulent NDV. This novel vaccination approach can provide efficient control of HPAI viruses in the field and facilitate poultry vaccination.

Inactivated H5 Antigens of H5N8 Protect Chickens from Lethal Infections by the Highly Pathogenic H5N8 and H5N6 Avian Influenza Viruses

Introduction

Highly pathogenic Asian H5-subtype avian influenza viruses have been found in poultry and wild birds worldwide since they were first detected in southern China in 1996. Extensive control efforts have not eradicated them. Vaccination prevents such viruses infecting poultry and reduces the number lost to compulsory slaughter. The study showed the efficacy of inactivated H5 vaccine from the H5N8 virus against highly pathogenic H5N8 and H5N6 avian influenza viruses in chickens.

Material and Methods

Reverse genetics constructed an H5 vaccine virus using the HA gene of the 2014 H5N8 avian influenza virus and the rest of the genes from A/PR/8/34 (H1N1). The vaccine viruses were grown in fertilised eggs, partially purified through a sucrose gradient, and inactivated with formalin. Chickens were immunised i.m. with 1 μg of oil-adjuvanted inactivated H5 antigens.

Results

Single dose H5 vaccine recipients were completely protected from lethal infections by homologous H5N8 avian influenza virus and shed no virus from the respiratory or intestinal tracts but were not protected from lethal infections by heterologous H5N6. When chickens were immunised with two doses and challenged with homologous H5N8 or heterologous H5N6, all survived and shed no virus.

Conclusion

Our results indicate that two-dose immunisations of chickens with H5 antigens with oil adjuvant are needed to provide broad protection against different highly pathogenic H5 avian influenza viruses.

A novel recombinant attenuated Newcastle disease virus expressing H9 subtype hemagglutinin protected chickens from challenge by genotype VII virulent Newcastle disease virus and H9N2 avian influenza virus

Newcastle disease virus (NDV) and H9 subtype avian influenza virus (AIV) are two avian pathogens across the globe. Inasmuch as most poultry flocks worldwide are vaccinated with a live low-virulence or attenuated NDV vaccine, we embarked on the development of vaccine prototypes that would have dual specificities and would allow a single immunization against both avian influenza (AI) and Newcastle disease (ND). Therefore, in the present work, a cloned full-length copy of the genome of the lentogenic NDV strain rmNA-1 was selected as a backbone vector to construct three chimeric NDVs that expressed (i) the ORF encoding the HA, (ii) the ectodomain of HA fused with the transmembrane domain and cytoplasmic tail regions derived from the NDV F protein and (iii) the ectodomain of HA fused with a short GS linker and the GCN4 sequences, and designated as rmNA-H9, rmNA-H9F, and rmNA-H9 (ECTO), respectively. rmNA-H9, rmNA-H9F, and rmNA-H9 (ECTO) stably expressed the modified HA gene for 10 egg passages and the three recombinants were found innocuous to chickens. The insertion of the chimeric HA-F, rather than HA-ECTO or ORF of HA, resulted in a recombinant virus with enhanced incorporation of the HA protein into the viral surface. A single immunization of SPF chickens with the three recombinants induced NDV- and AIV H9-specific antibodies, and protected chickens against a challenge with a lethal dose of velogenic NDV or AIV H9N2. Remarkably, non-shedding of influenza virus and higher levels of H9 subtype HI titers were observed 7 days post challenge (dpc) in rmNA-H9F vaccinated chickens, than other recombinants. Furthermore, a prime-boost vaccination of chickens with rmNA-H9F induced higher levels of NDV- and H9- HI and secretory IgA, as well as reduced viral shedding and virus-induced gross lesions, compared with the commercial vaccine. Therefore, the recombinant rmNA-H9F is a promising bivalent vaccine candidate against NDV and H9 subtype AIV in chickens.

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.

Challenges of influenza A viruses in humans and animals and current animal vaccines as an effective control measure

Influenza A viruses (IAVs) are genetically diverse and variable pathogens that share various hosts including human, swine, and domestic poultry. Interspecies and intercontinental viral spreads make the ecology of IAV more complex. Beside endemic IAV infections, human has been exposed to pandemic and zoonotic threats from avian and swine influenza viruses. Animal health also has been threatened by high pathogenic avian influenza viruses (in domestic poultry) and reverse zoonosis (in swine). Considering its dynamic interplay between species, prevention and control against IAV should be conducted effectively in both humans and animal sectors. Vaccination is one of the most efficient tools against IAV. Numerous vaccines against animal IAVs have been developed by a variety of vaccine technologies and some of them are currently commercially available. We summarize several challenges in control of IAVs faced by human and animals and discuss IAV vaccines for animal use with those application in susceptible populations.