Protection of commercial turkeys following inactivated or recombinant H5 vaccine application against the 2015U.S. H5N2 clade 2.3.4.4 highly pathogenic avian influenza virus

Efficacy of commercial recombinant HVT vaccines against a North American clade 2.3.4.4b H5N1 highly pathogenic avian influenza virus in chickens

The outbreak of clade 2.3.4.4b H5 highly pathogenic avian influenza (HPAI) in North America that started in 2021 has increased interest in applying vaccination as a strategy to help control and prevent the disease in poultry. Two commercially available vaccines based on the recombinant herpes virus of turkeys (rHVT) vector were tested against a recent North American clade 2.3.4.4b H5 HPAI virus isolate: A/turkey/Indiana/22-003707-003/2022 H5N1 in specific pathogen free white leghorn (WL) chickens and commercial broiler chickens. One rHVT-H5 vaccine encodes a hemagglutinin (HA) gene designed by the computationally optimized broadly reactive antigen method (COBRA-HVT vaccine). The other encodes an HA gene of a clade 2.2 virus (2.2-HVT vaccine). There was 100% survival of both chicken types COBRA-HVT vaccinated groups and in the 2.2-HVT vaccinated groups there was 94.8% and 90% survival of the WL and broilers respectively. Compared to the 2.2-HVT vaccinated groups, WL in the COBRA-HVT vaccinated group shed significantly lower mean viral titers by the cloacal route and broilers shed significantly lower titers by the oropharyngeal route than broilers. Virus titers detected in oral and cloacal swabs were otherwise similar among both vaccine groups and chicken types. To assess antibody-based tests to identify birds that have been infected after vaccination (DIVA-VI), sera collected after the challenge were tested with enzyme-linked lectin assay-neuraminidase inhibition (ELLA-NI) for N1 neuraminidase antibody detection and by commercial ELISA for detection of antibodies to the NP protein. As early as 7 days post challenge (DPC) 100% of the chickens were positive by ELLA-NI. ELISA was less sensitive with a maximum of 75% positive at 10DPC in broilers vaccinated with 2.2-HVT. Both vaccines provided protection from challenge to both types of chickens and ELLA-NI was sensitive at identifying antibodies to the challenge virus therefore should be evaluated further for DIVA-VI.

Efficacy of recombinant H5 vaccines delivered in ovo or day of age in commercial broilers against the 2015 U.S. H5N2 clade 2.3.4.4c highly pathogenic avian Influenza virus

BACKGROUND

Avian influenza is a highly contagious, agriculturally relevant disease that can severely affect the poultry industry and food supply. Eurasian-origin H5Nx highly pathogenic avian influenza viruses (HPAIV) (clade 2.3.4.4) have been circulating globally in wild birds with spill over into commercial poultry operations. The negative impact to commercial poultry renewed interest in the development of vaccines against these viruses to control outbreaks in the U.S.

METHODS

The efficacy of three recombinant H5 vaccines delivered in ovo or day of age were evaluated in commercial broilers challenged with the 2015 U.S. H5N2 clade 2.3.4.4c HPAIV. The recombinant vaccines included an alphavirus RNA particle vaccine (RP-H5), an inactivated reverse genetics-derived (RG-H5) and recombinant HVT vaccine (rHVT-AI) expressing H5 hemagglutinin (HA) genes. In the first experiment, in ovo vaccination with RP-H5 or rHVT-AI was tested against HPAI challenge at 3 or 6 weeks of age. In a second experiment, broilers were vaccinated at 1 day of age with a dose of either 107 or 108 RP-H5, or RG-H5 (512 HA units (HAU) per dose).

RESULTS

In experiment one, the RP-H5 provided no protection following in ovo application, and shedding titers were similar to sham vaccinated birds. However, when the RP-H5 was delivered in ovo with a boost at 3 weeks, 95% protection was demonstrated at 6 weeks of age. The rHVT-AI vaccine demonstrated 95 and 100% protection at 3 and 6 weeks of age, respectively, of challenged broilers with reduced virus shedding compared to sham vaccinated birds. Finally, when the RP-H5 and rHVT vaccines were co-administered at one day of age, 95% protection was demonstrated with challenge at either 3 or 6 weeks age. In the second experiment, the highest protection (92%) was observed in the 108 RP-H5 vaccinated group. Significant reductions (p < 0.05) in virus shedding were observed in groups of vaccinated birds that were protected from challenge. The RG-H5 provided 62% protection from challenge. In all groups of surviving birds, antibody titers increased following challenge.

CONCLUSIONS

Overall, these results demonstrated several strategies that could be considered to protected broiler chickens during a H5 HPAI challenge.

Efficacy of inactivated and RNA particle vaccines against a North American Clade 2.3.4.4b H5 highly pathogenic avian influenza virus in chickens

Highly pathogenic avian influenza virus (HPAIV) has caused widespread outbreaks in poultry in the Americas. Because of the duration and extent of these outbreaks, vaccine use may be an additional tool to limit virus spread. Three vaccines were evaluated for efficacy in chickens against a current North American clade 2.3.4.4b H5 HPAIV isolate, A/turkey/Indiana/3703-003/2022 H5N1. The vaccines included: 1) a commercial inactivated reverse genetics (rg) generated H5N1 product with a clade 2.3.4.4c H5 hemagglutinin (HA) (rgH5N1); 2) a commercial alphavirus RNA particle (RP) vaccine with the TK/IN/22 HA; and 3) an in-house inactivated rg produced vaccine with the TK/IN/22 HA and a North American lineage N9 neuraminidase (NA) (SEP-22-N9). Both inactivated vaccines were produced with HA genes that were modified to be low pathogenic and with the remaining genes from the PR8 influenza strain. All vaccines provided 100% protection against mortality and morbidity and all vaccines reduced virus shed by the oropharyngeal and cloacal routes significantly compared to sham vaccinates. However, differences were observed among the vaccines in quantities of virus shed at two- and four-days post challenge (DPC). To determine if infected birds could be identified after vaccination to aid surveillance programs, serum was collected from the RP and SEP-22-N9 vaccine groups at 7, 10, and 14 DPC to detect antibody to the NA and nucleoprotein (NP) of the challenge virus by enzyme linked lectin assay (ELLA) and ELISA. As early as 7DPC ELLA detected antibody in sera from 100% of the chickens in the RP vaccinated group and 70% of the chickens in the SEP-22-N9 vaccinated group. Antibody to the NP was detected by commercial ELISA in more than 50% of the birds in the RP vaccinated group at each time point.

HVT-vectored H7 vaccine protects chickens from lethal infection with the highly pathogenic H7N9 Avian influenza virus

Since mid-2016, the highly pathogenic H7N9 subtype avian influenza virus (AIV) has threatened both public health and the poultry industry. Although a vaccination strategy has been deemed imperative to manage the virus, the most commonly used inactivated vaccines today are susceptible to interference from maternal antibodies and associated with an over-reliance on humoral immunity. In response, we developed a recombination vaccine with the herpesvirus of turkeys (HVT) as the vector to squeeze HPAI H7N9 and assessed its protective efficiency in immunized chickens. By inserting an enhanced green fluorescent protein (EGFP) expression cassette (i.e., MCMV+EGFP+SV40 polyA) into the HVT065 and HVT066 positions, we obtained the recombinant HVT expressing EGFP (i.e., rHVT-EGFP). Electroporation and EGFP tags improved the efficiency of transfection compared with transfection using expression plasmids without any fluorescent labeling and traditional liposomes. Using limiting dilution analysis and ultrasonic cell disruption techniques, we screened and purified a cell-bound herpes virus based on rHVT-EGFP and consequently constructed a recombinant HVT expressing the hemagglutinin (HA) of H7N9 (i.e., rHVT-H7HA), which was able to proliferate similarly to the parental strain, stably pass for at least 15 generations in vitro, and replicate stably in multiple organs in vivo. After chickens were immunized with rHVT-H7HA, the average antibody titers reached up to 3 log2 at 35 d post-vaccination and remained stable. Those results suggest that rHVT-H7HA can protect chickens against H7N9 with a dose-independent immune protection rate of 90% and significantly reduce the lung virus titer 4 d post-challenge.

Comparative analysis of PB2 residue 627E/K/V in H5 subtypes of avian influenza viruses isolated from birds and mammals

Avian influenza viruses (AIVs) are naturally found in wild birds, primarily in migratory waterfowl. Although species barriers exist, many AIVs have demonstrated the ability to jump from bird species to mammalian species. A key contributor to this jump is the adaption of the viral RNA polymerase complex to a new host for efficient replication of its RNA genome. The AIV PB2 gene appears to be essential in this conversion, as key residues have been discovered at amino acid position 627 that interact with the host cellular protein, acidic nuclear phosphoprotein 32 family member A (ANP32A). In particular, the conversion of glutamic acid (E) to lysine (K) is frequently observed at this position following isolation in mammals. The focus of this report was to compare the distribution of PB2 627 residues from different lineages and origins of H5 AIV, determine the prevalence between historical and contemporary sequences, and investigate the ratio of amino acids in avian vs. mammalian AIV sequences. Results demonstrate a low prevalence of E627K in H5 non-Goose/Guangdong/1996-lineage (Gs/GD) AIV samples, with a low number of mammalian sequences in general. In contrast, the H5-Gs/GD lineage sequences had an increased prevalence of the E627K mutation and contained more mammalian sequences. An approximate 40% conversion of E to K was observed in human sequences of H5 AIV, suggesting a non-exclusive requirement. Taken together, these results expand our understanding of the distribution of these residues within different subtypes of AIV and aid in our knowledge of PB2 mutations in different species.

Poultry Vaccine Technology Platforms

The different technology platforms used to make poultry vaccines are reviewed. Vaccines based on classical technologies are either live attenuated or inactivated vaccines. Genetic engineering is applied to design by deletion, mutation, insertion, or chimerization, genetically modified target microorganisms that are used either as live or inactivated vaccines. Other vaccine platforms are based on one or a few genes of the target pathogen agent coding for proteins that can induce a protective immune response ("protective genes"). These genes can be expressed in vitro to produce subunit vaccines. Alternatively, vectors carrying these genes in their genome or nucleic acid-based vaccines will induce protection by in vivo expression of these genes in the vaccinated host. Properties of these different types of vaccines, including advantages and limitations, are reviewed, focusing mainly on vaccines targeting viral diseases and on technologies that succeeded in market authorization.

Prediction of highly pathogenic avian influenza vaccine efficacy in chickens by comparison of in vitro and in vivo data: A meta-analysis and systematic review

Vaccines for avian influenza (AI) can protect poultry against disease, mortality, and virus transmission. Numerous factors, including: vaccine platform, immunogenicity, and relatedness to the field strain, are known to be important to achieving optimal AI vaccine efficacy. To better understand how these factors contribute to vaccine protection, a systematic meta-analysis was conducted to evaluate efficacy data for vaccines in chickens challenged with highly pathogenic (HP) AI. Data from a total of 120 individual trials from 25 publications were selected and evaluated. Two vaccine criteria were evaluated for their effects on two metrics of protection. The vaccine criteria were: 1) the relatedness of the vaccine antigen and challenge strain in the hemagglutinin 1 domain (HA1) protein sequence; 2) vaccine-induced antibody titers to the challenge virus (VIAC). The metrics of protection were: A) survival of vaccinated chickens vs unvaccinated controls; and B) reduction in oral virus-shedding by vaccinated vs unvaccinated controls 2-4 days post challenge. Three vaccine platforms were evaluated: oil-adjuvanted inactivated whole AI virus, recombinant herpes virus of turkeys (rHVT) vectored, and a non-replicating alpha-virus vectored RNA particle (RP) vaccine. Higher VIAC correlated with greater reduction of virus-shed and vaccine efficacy by all vaccine platforms. Both higher HA1 relatedness and higher VIAC using challenge virus as antigen correlated with better survival by inactivated vaccines and rHVT-vectored vaccines. However, rHVT-vectored and RP based vaccines were more tolerant of variation in the HA1; the relatedness of the HA1 of the vaccine and challenge virus did not significantly correlate with survival with rHVT-vectored vaccines. Protection was achieved with the lowest aa similarity for which there was data, 90-93 % for rHVT vaccines and 88 % for the RP vaccine.

Review of Poultry Recombinant Vector Vaccines

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

Identification of Efficacious Vaccines Against Contemporary North American H7 Avian Influenza Viruses

Five vaccines, including four inactivated, whole-virus water-in-oil adjuvanted vaccines and a commercial nonreplicating alphavirus-vectored RNA particle (RP) vaccine were evaluated in chickens for their ability to provide protection against challenge with a recent H7 highly pathogenic avian influenza virus (AIV) from the United States (A/turkey/IN/1403-1/2016 H7N8). One of the inactivated vaccines and the RP vaccine were prepared with A/turkey/IN/16-01571-6/2016 H7N8 low pathogenic AIV (LPAIV; TK/IN/16), which is identical to the challenge virus, except for the proteolytic cleavage site of the hemagglutinin protein. The remaining three inactivated vaccines were prepared with other North American H7 LPAIVs. The hemagglutination inhibition assay was used to evaluate the antigenic relationships among the vaccines and selected recent H7 AIV isolates. All five vaccines provided protection against mortality. The inactivated vaccines reduced virus shedding significantly at 2 and 4 days post challenge compared with sham-vaccinated chickens. In contrast, the RP vaccine did not significantly reduce virus shedding. The inactivated vaccine prepared with TK/IN/16 elicited the highest antibody responses, which suggests it is a strong candidate for use as an antigen for North American H7 AIVs. Antigenic distance calculations showed that the four inactivated vaccine strains and other recent North American H7 isolates are antigenically similar, which suggests that the vaccines evaluated here would be similar enough to provide protection to other North American H7 AIVs. If future H7 outbreaks in poultry warrant vaccination, the field strain can be rapidly evaluated with these antigens and, if adequately related, one of these characterized strains may be used.

Efficacy of Two Licensed Avian Influenza H5 Vaccines Against Challenge with a 2015 U.S. H5N2 clade 2.3.4.4 Highly Pathogenic Avian Influenza Virus in Domestic Ducks

Highly pathogenic avian influenza (HPAI) clade 2.3.4.4 viruses from the H5 goose/Guangdong lineage caused a major outbreak in poultry in the United States in 2015. Although the outbreak was controlled, vaccines were considered as an alternative control method, and new vaccines were approved and purchased by the U.S. Department of Agriculture National Veterinary Stockpile for emergency use. In this study, we evaluated the efficacy of two of these vaccines in protecting Pekin ducks (Anas platyrhynchos var. domestica) against challenge with a H5N2 HPAI poultry isolate. A recombinant alphavirus-based vaccine and an inactivated adjuvanted reverse genetics vaccine, both expressing the hemagglutinin gene of a U.S. H5 clade 2.3.4.4 isolate (A/Gyrfalcon/Washington/41088-6/2014 H5N8), were used to immunize the ducks. The vaccines were given either as single vaccination at 2 days of age or in a prime-boost strategy at 2 and 15 days of age. At 32 days of age, all ducks were challenged with A/turkey/Minnesota/12582/15 H5N2 HPAI virus clade 2.3.4.4. All ducks from the nonvaccinated challenge control group became infected and shed virus; one duck in this group presented mild ataxia, and a second duck died. No mortality or clinical signs were observed in vaccinated and challenged ducks, with the exception of one duck presenting with mild ataxia. Both vaccines, regardless of the vaccination strategy used, were immunogenic in ducks and reduced or prevented virus shedding after challenge. In conclusion, good protection against H5Nx infection was achieved in ducks vaccinated with the vaccines examined, which were homologous to the challenge virus, with prime-boost strategies conferring the best protection against infection.

Development of a Multiplex RT-qPCR for the Detection of Different Clades of Avian Influenza in Poultry

Since the initial detection of H5N1, a highly pathogenic avian influenza (HPAI) virus, in 1996 in China, numerous HPAI H5 lineages have been classified, and they continue to pose a threat to animal and human health. In this study, we developed a novel primer/probe set that can be employed to simultaneously detect pan-H5 HPAI and two clades, 2.3.2.1 and 2.3.4.4, of H5Nx viruses using reverse transcription quantitative polymerase chain reaction (RT-qPCR). The sensitivity and specificity of these primer sets and probes were confirmed with a number of different subtypes of influenza virus and the H5-HA gene plasmid DNA. In particular, the multiplex RT-qPCR assay was successfully applied to the simultaneous detection of H5 HPAI and different virus clades in clinical field samples from a poultry farm. Therefore, this multiplex assay and a novel detection primer set and probes will be useful for the laboratory diagnosis and epidemiological field studies of different circulating H5 HPAI virus clades in poultry and migratory wild birds.

Protection afforded by avian influenza vaccination programmes consisting of a novel RNA particle and an inactivated avian influenza vaccine against a highly pathogenic avian influenza virus challenge in layer chickens up to 18 weeks post-vaccination

The efficacies of an oil adjuvanted-inactivated reverse genetics-derived H5 avian influenza virus (AIV) vaccine and an alphavirus replicon RNA particle (RP) AIV vaccine were evaluated in commercial Leghorn chickens. Challenge utilized A/turkey/MN/12582/2015, an isolate representing the U.S. H5N2 Clade 2.3.4.4 responsible for the 2015 highly pathogenic avian influenza (HPAI) epornitic in commercial poultry the United States. As part of a long-term, 36-week study, chickens were challenged at seven weeks of age after receiving a single vaccination, at 18 weeks of age following a vaccine prime-single boost, and at 36 weeks of age after a prime- double-boost. All vaccine programmes reduced virus oropharyngeal and cloacal shedding and mortality compared to the non-vaccinated control birds; however, chickens receiving at least one administration of the RP vaccine generally had diminished viral shedding especially from the cloacal swabbings. A detectable serum antibody response and protection were observed through 18 weeks post-vaccination. Our data suggest that, in conjunction with a comprehensive eradication, enhanced biosecurity and controlled marketing plan, vaccination programmes of commercial layer chickens with novel RP vaccines may represent an important tool for preventing HPAI-related mortalities and decreasing viral load during a catastrophic influenza outbreak. RESEARCH HIGHLIGHTS Immunization of poultry following a vaccination schedule consisting of inactivated and RNA particle vaccines offered significant protection against lethal disease following HPAIV challenge. Virus shedding was significantly (P < 0.05) reduced in chickens vaccinated with either inactivated and/or recombinant vaccines. Serum antibody titres were not a reliable indicator of protection. An inactivated vaccine containing 384 HAU of the homologous antigen was unable to induce complete protection.

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.

2D-SAR, Topomer CoMFA and molecular docking studies on avian influenza neuraminidase inhibitors

Avian influenza is a serious zoonotic infectious disease with huge negative impacts on local poultry farming, human health and social stability. Therefore, the design of new compounds against avian influenza has been the focus in this field. In this study, computational methods were applied to investigate the compounds with neuraminidase inhibitory activity. First, 2D-SAR model was built to recognize neuraminidase inhibitors (NAIs). As a result, the accuracy of 10 cross-validation and independent tests is 96.84% and 98.97%, respectively. Then, the Topomer CoMFA model was constructed to predict the inhibitory activity and analyses molecular fields. Two models were obtained by changing the cutting methods. The second model is employed to predict the activity (q2 = 0.784 and r2 = 0.982). Molecular docking was also used to further analyze the binding sites between NAIs and neuraminidase from human and avian virus. As a result, it is found that same binding Total Score has some differences, but the binding sites are basically the same. At last, some potential NAIs were screened and some optimal opinions were taken. It is expected that our study can assist to study and develop new types of NAIs.