Potency of a recombinant NDV-H5 vaccine against various HPAI H5N1 virus challenges in SPF chickens

Efficacy of live and inactivated recombinant Newcastle disease virus vaccines expressing clade 2.3.4.4b H5 hemagglutinin against H5N1 highly pathogenic avian influenza in SPF chickens, Broilers, and domestic ducks

A Newcastle disease virus (NDV)-vectored vaccine expressing clade 2.3.4.4b H5 Hemagglutinin was developed and assessed for efficacy against H5N1 highly pathogenic avian influenza (HPAI) in specific pathogen-free (SPF) chickens, broilers, and domestic ducks. In SPF chickens, the live recombinant NDV-vectored vaccine, rK148/22-H5, achieved complete survival against HPAI and NDV challenges and significantly reduced viral shedding. Notably, the live rK148/22-H5 vaccine conferred good clinical protection in broilers despite the presence of maternally derived antibodies. Good clinical protection was observed in domestic ducks, with decreased viral shedding. It demonstrated complete survival and reduced cloacal viral shedding when used as an inactivated vaccine from SPF chickens. The rK148/22-H5 vaccine is potentially a viable and supportive option for biosecurity measure, effectively protecting in chickens against the deadly clade 2.3.4.4b H5 HPAI and NDV infections. Furthermore, it aligns with the strategy of Differentiating Infected from Vaccinated Animals (DIVA).

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.

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.

The Expression of Hemagglutinin by a Recombinant Newcastle Disease Virus Causes Structural Changes and Alters Innate Immune Sensing

Recombinant Newcastle disease viruses (rNDV) have been used as bivalent vectors for vaccination against multiple economically important avian pathogens. NDV-vectored vaccines expressing the immunogenic H5 hemagglutinin (rNDV-H5) are considered attractive candidates to protect poultry from both highly pathogenic avian influenza (HPAI) and Newcastle disease (ND). However, the impact of the insertion of a recombinant protein, such as H5, on the biological characteristics of the parental NDV strain has been little investigated to date. The present study compared a rNDV-H5 vaccine and its parental NDV LaSota strain in terms of their structural and functional characteristics, as well as their recognition by the innate immune sensors. Structural analysis of the rNDV-H5 demonstrated a decreased number of fusion (F) and a higher number of hemagglutinin-neuraminidase (HN) glycoproteins compared to NDV LaSota. These structural differences were accompanied by increased hemagglutinating and neuraminidase activities of rNDV-H5. During in vitro rNDV-H5 infection, increased mRNA expression of TLR3, TLR7, MDA5, and LGP2 was observed, suggesting that the recombinant virus is recognized differently by sensors of innate immunity when compared with the parental NDV LaSota. Given the growing interest in using NDV as a vector against human and animal diseases, these data highlight the importance of thoroughly understanding the recombinant vaccines’ structural organization, functional characteristics, and elicited immune responses.

AIV polyantigen epitope expressed by recombinant baculovirus induces a systemic immune response in chicken and mouse models

BACKGROUND

The protective efficacy of avian influenza virus (AIV) vaccines is unsatisfactory due to the presence of various serotypes generated by genetic reassortment. Thus, immunization with a polyantigen chimeric epitope vaccine may be an effective strategy for protecting poultry from infection with different AIV subtypes.

METHODS

Baculovirus has recently emerged as a novel and attractive gene delivery vehicle for animal cells. In the present study, a recombinant baculovirus BmNPV-CMV/THB-P10/CTLT containing a fused codon-optimized sequence (CTLT) of T lymphocyte epitopes from H1HA, H9HA, and H7HA AIV subtypes, and another fused codon-optimized sequence (THB) of Th and B cell epitopes from H1HA, H9HA, and H7HA AIV subtypes, driven by a baculovirus P10 promoter and cytomegalovirus CMV promoter, respectively, was constructed.

RESULTS

Western blotting and cellular immunofluorescence demonstrated that the CTLT (THB) can be expressed in rBac-CMV/THB-P10/CTLT-infected silkworm cells (mammalian HEK293T cells). Furthermore, the recombinant virus, rBac-CMV-THB-CTLT, was used to immunize both chickens and mice.

CONCLUSIONS

The results of an indirect ELISA, immunohistochemistry, and T lymphocyte proliferation assay indicated that specific humoral and cellular responses were detected in both chicken and mice. These results suggest that rBac-CMV/THB-P10/CTLT can be developed as a potential vaccine against different AIV subtypes.

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.

Structural Insights for Anti-Influenza Vaccine Design

Influenza A virus are a persistent and significant threat to human health, and current vaccines do not provide sufficient protection due to antigenic drift, which allows influenza viruses to easily escape immune surveillance and antiviral drug activity. Influenza hemagglutinin (HA) is a glycoprotein needed for the entry of enveloped influenza viruses into host cells and is a potential target for anti-influenza humoral immune responses. In recent years, a number of broadly neutralizing antibodies (bnAbs) have been isolated, and their relative structural information obtained from the crystallization of influenza antigens in complex with bnAbs has provided some new insights into future influenza vaccine research. Here, we review the current knowledge of the HA-targeted bnAbs and the structure-based mechanisms contributing to neutralization. We also discuss the potential for this structure-based approach to overcome the challenge of obtaining a highly desired "universal" influenza vaccine, especially on small proteins and peptides.

Prime-boost vaccination strategy against avian influenza and Newcastle disease viruses reduces shedding of the challenge viruses

In the present study, we carried-out assessment of efficacy of different immunization strategies using two bivalent vaccine formulations containing antigens of inactivated Newcastle disease virus (NDV-genotype VIId) and reassortant highly pathogenic avian influenza virus (H5N1-HPAIV) mixed with Montanide ISA71 and Montanide Gel02 as adjuvants. The efficacy of the prepared vaccines was evaluated by determining the cellular and humoral immune responses. In addition, protection against H5N1-AIV and NDV-genotype VIId challenge viruses post vaccination was assessed when Montanide-Gel02 based vaccine was inoculated in 10-days-old specific pathogen free chicks intraocularly once, twice or once followed by a boost with the Montanide ISA71 based vaccine. The cytokines profile analysis demonstrated that the prime-boost strategy induced the highest up-regulation in interferon-gamma (11.39-fold change) and interleukin-6 (14.12-fold change) genes expression. Also, enhanced lymphocytes proliferation was recorded beside increased antibody titers with protection levels reaching 50 and 60% against H5N1 and NDV challenge; respectively. Immunization with Montanide ISA71 inactivated vaccine induced 80% protection; however, the prime-boost combination afforded complete protection (100%) in the challenged chickens against mortality, clinical signs and virus shedding. Finally, these results highlight the significance of considering not only different vaccine platforms but also vaccination strategies to maximize protection against AIV and NDV with regards to the longevity of the vaccine-induced immune response.

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

Since December 2014, Eurasian-origin, highly pathogenic avian influenza H5 viruses including H5N1, H5N2, and H5N8 subtypes (called H5Nx viruses), which belong to the H5 clade 2.3.4.4, have been detected in U.S. wild birds. Subsequently, highly pathogenic H5N2 and H5N8 viruses have caused outbreaks in U.S. domestic poultry. Vaccination is one of the most effective ways to control influenza outbreaks and protect animal and public health. Newcastle disease virus (NDV)-based influenza vaccines have been demonstrated to be efficacious and safe in poultry. Herein, we developed an NDV-based H5 vaccine (NDV-H5) that expresses a codon-optimized ectodomain of the hemagglutinin from the A/chicken/Iowa/04-20/2015 (H5N2) virus and evaluated its efficacy in chickens. Results showed that both live and inactivated NDV-H5 vaccines induced hemagglutinin inhibition antibody titers against the H5N2 virus in immunized chickens after prime and booster, and both NDV-H5 vaccines completely protected chickens from lethal challenge with the highly pathogenic H5N2 A/turkey/Minnesota/9845-4/2015 virus. No clinical signs and only minimal virus shedding was observed in both vaccinated groups. In contrast, all mock-vaccinated, H5N2-infected chickens shed virus and died within 5 days post challenge. Furthermore, one dose of the live NDV-H5 vaccine also provided protection of 90% chickens immunized by coarse spraying; after exposure to H5N2 challenge, sera from vaccinated surviving chickens neutralized both highly pathogenic H5N1 and H5N8 viruses. Taken together, our results suggest that the NDV-based H5 vaccine is able to protect chickens against intercontinental highly pathogenic H5Nx viruses and can be used by mass application to protect the poultry industry.

Vaccines based on Newcastle disease virus have proved efficacious in protecting chickens from H5 avian influenza strains. Avian influenza causes significant losses to the agriculture industry, indicating the importance of research into their control. A research collaboration of US and Chinese scientists, led by Kansas State University’s Wenjun Ma, have now produced vaccines based on Newcastle disease virus (NDV) — a platform easily modified to express immunity-stimulating proteins from other pathogens. Chickens vaccinated with the group’s vaccines survived a lethal dose of avian flu strain H5N2 and generated neutralizing antibodies cross-protective against other avian flu subtypes. The vaccine was easily applied by spraying the animals. The authors suggest that their data, in addition to previous studies, indicate that NDV could also be a useful vaccine platform for mammals such as humans.

Stronger Interference of Avian Influenza Virus-Specific Than Newcastle Disease Virus-Specific Maternally Derived Antibodies with a Recombinant NDV-H5 Vaccine

Maternally derived antibodies (MDA) are known to provide early protection from disease but also to interfere with vaccination efficacy of young chicks. This interference phenomenon is well described in the literature for viral diseases such as infectious bursal disease, Newcastle disease (ND), and avian influenza (AI). The goal of this work was to investigate the impact of H5 MDA and/or ND virus (NDV) MDA on the vaccine efficacy of a recombinant NDV-H5-vectored vaccine (rNDV-H5) against two antigenically divergent highly pathogenic AI (HPAI) H5N1 challenges. In chickens with both H5 and NDV MDA, a strong interference was observed with reduced clinical protection when compared to vaccinated specific-pathogen-free (SPF) chickens. In contrast, in chickens from commercial suppliers with NDV MDA only, a beneficial impact on the vaccine efficacy was observed with full protection and reduced viral excretion in comparison with rNDV-H5-vaccinated SPF chickens. To distinguish between the respective effects of the H5 and NDV MDA, an SPF model where passive immunity had been artificially induced by inoculations of H5 and NDV hyperimmunized polysera, respectively, was used. In the presence of H5 artificial MDA, a strong interference reflected by a reduction in vaccine protection was demonstrated whereas no interference and even an enhancing protective effect was confirmed in presence of NDV MDA. The present work suggests that H5 and NDV MDA interact differently with the rNDV-H5 vaccine with different consequences on its efficacy, the mechanisms of which require further investigations.

Newcastle disease vaccines-A solved problem or a continuous challenge?

Newcastle disease (ND) has been defined by the World Organisation for Animal Health as infection of poultry with virulent strains of Newcastle disease virus (NDV). Lesions affecting the neurological, gastrointestinal, respiratory, and reproductive systems are most often observed. The control of ND must include strict biosecurity that prevents virulent NDV from contacting poultry, and also proper administration of efficacious vaccines. When administered correctly to healthy birds, ND vaccines formulated with NDV of low virulence or viral-vectored vaccines that express the NDV fusion protein are able to prevent clinical disease and mortality in chickens upon infection with virulent NDV. Live and inactivated vaccines have been widely used since the 1950's. Recombinant and antigenically matched vaccines have been adopted recently in some countries, and many other vaccine approaches have been only evaluated experimentally. Despite decades of research and development towards formulation of an optimal ND vaccine, improvements are still needed. Impediments to prevent outbreaks include uneven vaccine application when using mass administration techniques in larger commercial settings, the difficulties associated with vaccinating free-roaming, multi-age birds of village flocks, and difficulties maintaining the cold chain to preserve the thermo-labile antigens in the vaccines. Incomplete or improper immunization often results in the disease and death of poultry after infection with virulent NDV. Another cause of decreased vaccine efficacy is the existence of antibodies (including maternal) in birds, which can neutralize the vaccine and thereby reduce the effectiveness of ND vaccines. In this review, a historical perspective, summary of the current situation for ND and NDV strains, and a review of traditional and experimental ND vaccines are presented.

Viral vector-based influenza vaccines

Antigenic drift of seasonal influenza viruses and the occasional introduction of influenza viruses of novel subtypes into the human population complicate the timely production of effective vaccines that antigenically match the virus strains that cause epidemic or pandemic outbreaks. The development of game-changing vaccines that induce broadly protective immunity against a wide variety of influenza viruses is an unmet need, in which recombinant viral vectors may provide. Use of viral vectors allows the delivery of any influenza virus antigen, or derivative thereof, to the immune system, resulting in the optimal induction of virus-specific B- and T-cell responses against this antigen of choice. This systematic review discusses results obtained with vectored influenza virus vaccines and advantages and disadvantages of the currently available viral vectors.

Vaccines against influenza A viruses in poultry and swine: Status and future developments

Influenza A viruses are important pathogens with a very broad host spectrum including domestic poultry and swine. For preventing clinical disease and controlling the spread, vaccination is one of the most efficient tools. Classical influenza vaccines for domestic poultry and swine are conventional inactivated preparations. However, a very broad range of novel vaccine types ranging from (i) nucleic acid-based vaccines, (ii) replicon particles, (iii) subunits and virus-like particles, (iv) vectored vaccines, or (v) live-attenuated vaccines has been described, and some of them are now also used in the field. The different novel approaches for vaccines against avian and swine influenza virus infections are reviewed, and additional features like universal vaccines, novel application approaches and the "differentiating infected from vaccinated animals" (DIVA)-strategy are summarized.

Protection conferred by recombinant turkey herpesvirus avian influenza (rHVT-H5) vaccine in the rearing period in two commercial layer chicken breeds in Egypt

The effectiveness of recombinant turkey herpesvirus avian influenza (A/swan/Hungary/4999/2006(H5N1)) clade 2.2 virus (rHVT-H5) vaccine was evaluated in two layer chicken breeds (White Bovans [WB] and Brown Shaver [BS]). One dose of rHVT-H5 vaccine was administered at day 1 and birds were monitored serologically (haemagglutination inhibition test) and virologically for 19 weeks. Maternally-derived antibody and post-vaccination H5 antibody titres were measured using the Chinese (A/Goose/Guangdong/1/96(H5N1)) HA and the Egyptian (A/chicken/Egypt/128s/2012(H5N1)) HA as antigens. The challenge was conducted at 19 weeks of age and on six experimental groups: Groups I (WB) and II (BS), both vaccinated and challenged; Groups III (WB) and IV (BS), both vaccinated but not challenged; Groups V and VI, unvaccinated specific pathogen free chickens, serving respectively as positive and negative controls. The challenge virus was the clade 2.2.1 highly pathogenic avian influenza H5N1 A/chicken/Egypt/128s/2012 at a dose of 10(6) median embryo infective dose. For both breeds, complete maternally-derived antibody waning occurred at the age of 4 weeks. The immune response to rHVT-H5 vaccination was detected from the sixth week. The seroconversion rates for both breeds reached 85.7 to 100% in the eighth week of age. Protection levels of 73.3%, 60% and 0% were respectively recorded in Groups I, II and V. No mortalities occurred in the unchallenged groups. Group I showed superior results for all measured post-challenge parameters. In conclusion, a single rHVT-H5 hatchery vaccination conferred a high level of protection for a relatively extended period. This vaccine could be an important tool for future A/H5N1 prevention/control in endemic countries. Further studies on persistence of immunity beyond 19 weeks, need for booster with inactivated vaccines, breed susceptibility and vaccinal response, and transmissibility are recommended.

Comparison of single 1-day-old chick vaccination using a Newcastle disease virus vector with a prime/boost vaccination scheme against a highly pathogenic avian influenza H5N1 challenge

Avian influenza (AI) vaccines should be used as part of a whole comprehensive AI control programme. Vectored vaccines based on Newcastle disease virus (NDV) are very promising, but are so far licensed in only a few countries. In the present study, the immunogenicity and protection against a highly pathogenic H5N1 influenza challenge were evaluated after vaccination with an enterotropic NDV vector expressing an H5 haemagglutinin (rNDV-H5) in 1-day-old specific pathogen free chickens inoculated once, twice or once followed by a heterologous boost with an inactivated H5N9 vaccine (iH5N9). The heterologous prime/boost rNDV-H5/iH5N9 combination afforded the best level of protection against the H5N1 challenge performed at 6 weeks of age. Two rNDV-H5 administrations conferred a good level of protection after challenge, although only a cellular H5-specific response could be detected. Interestingly, a single administration of rNDV-H5 gave the same level of protection as the double administration but without any detectable H5-specific immune response. In contrast to AI immunity, a high humoral, mucosal and cellular NDV-specific immunity could be detected up to 6 weeks post vaccination after using the three different vaccination schedules. NDV-specific mucosal and cellular immune responses were slightly higher after double rNDV-H5 vaccination when compared with single inoculation. Finally, the heterologous prime/boost rNDV-H5/iH5N9 combination induced a broader detectable immunity including systemic, mucosal and cellular AI and NDV-specific responses.

Comparative analysis of antibody induction and protection against influenza virus infection by DNA immunization with HA, HAe, and HA1 in mice

Plasmid DNA vaccines are considered alternatives to inactivated influenza virus vaccines to control influenza. Vaccination with a hemagglutinin (HA)-, HA ectodomain (HAe)-, or HA subunit 1 (HA1)-based vaccine can stimulate protective immunity in animals. The aim of this study was to compare their capacity to induce an antibody response and protection against influenza virus infection in mice after DNA vaccination. We constructed three expression vectors encoding full-length HA, HAe, or HA1 of the A/California/07/2009 influenza A virus and designed three animal experiments: (i) BALB/c mice were immunized twice with 30 μg of the HA, HAe, or HA1 DNA vaccine with high-voltage electroporation (100 V), and 3 weeks after boosting, they were challenged with a lethal dose of virus. (ii) Immunization and challenge were as in experiment i, but with low-voltage electroporation (10 V). (iii) Mice were immunized once with 50 μg of DNA and challenged 1 week later. The immunogenic effects of the three DNA vaccines were evaluated in terms of antibody titer, survival rate, bodyweight change, and lung viral titer. In all three experiments, both HA and HAe induced higher antibody and neutralization titers than HA1. Following challenge with a lethal mouse-adapted homologous virus, both HA and HAe reduced the viral titers in lung washes or offered better protection from weight loss than HA1 in experiments ii and iii. Thus, HA1 induces a lower immune response than HA or HAe when used as a DNA vaccination. Our data should be valuable in choosing the optimal candidate vaccine when faced with the threat of pandemic influenza.