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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. [ABSTRACT FROM AUTHOR]

Abstract: Highly pathogenic (HP) H5N1 avian influenza has become endemic in several countries in Asia and Africa, and vaccination is being widely used as a control tool. However, there is a need for efficacious vaccines preferably utilizing a DIVA (differentiate infected from vaccinated animals) marker strategy to allow for improved surveillance of influenza in vaccinated poultry. Using a reverse genetics approach, we generated Asian rgH5N9 vaccine strain deriving the hemagglutinin gene from A/chicken/Indonesia/7/2003 (H5N1) with modification of the cleavage site to be low pathogenic (LP) and N9 neuraminidase gene from the North American LP A/turkey/Wisconsin/1968 (H5N9) virus. The recombinant rgH5N9, A/turkey/Wisconsin/1968 (H5N9) A/chicken/Hidalgo/232/1994 (H5N2), and wild type HP A/chicken/Indonesia/7/2003 (H5N1) viruses were used to prepare inactivated oil-emulsified whole virus vaccines. Two weeks after vaccination, chickens were challenged with either Asian HP H5N1 viruses, A/chicken/Indonesia/7/2003 (W.H.O. clade 2.1) or A/chicken/Supranburi Thailand/2/2004 (W.H.O. clade 1.0). The H5 HA1 of the North American vaccine strains exhibited 12% amino acid differences including amino acid changes in the major antigenic sites as compared to the Asian HP H5N1 challenge viruses, serologically exhibited substantial antigenic difference, but still provided 100% protection from mortality. However, challenge virus shedding was significantly higher in chickens immunized with antigenically distinct American lineage vaccines as compared to the antigenically matched Asian rgH5N9 and the wild type Asian H5N1 vaccine. The antibody response to the heterologous subtype neuraminidase proteins were discriminated in vaccinated and infected chickens using a rapid fluorescent 2′-(4-methylumbelliferyl)-α-d-N-acetylneuraminic acid sodium salt as substrate for neuraminidase inhibition assay. This study demonstrates the value of using a vaccine containing antigenically matched H5 hemagglutinin for control of HP H5N1 avian influenza in poultry and the potential utility of a heterologous neuraminidase as a DIVA marker. [Copyright &y& Elsevier]

Wild-bird surveillance in North America for avian influenza (AI) viruses with a goal of early identification of the Asian H5N1 highly pathogenic AI virus has identified at least six low-pathogenicity H5N1 AI viruses between 2004 and 2006. The hemagglutinin (HA) and neuraminidase (NA) genes from all 6 H5N1 viruses and an additional 38 North American wild-bird-origin H5 subtype and 28 N1 subtype viruses were sequenced and compared with sequences available in GenBank by phylogenetic analysis. Both HA and NA were phylogenetically distinct from those for viruses from outside of North America and from those for viruses recovered from mammals. Four of the H5N1 AI viruses were characterized as low pathogenicity by standard in vivo pathotyping tests. One of the H5N1 viruses, A/MuteSwan/MI/451072-2/06, was shown to replicate to low titers in chickens, turkeys, and ducks. However, transmission of A/MuteSwan/MI/451072-2/06 was more efficient among ducks than among chickens or turkeys based on virus shed. The 50% chicken infectious dose for A/MuteSwan/MI/451072-2/06 and three other wild-waterfowl-origin H5 viruses were also determined and were between 105.3 and 107.5 50% egg infective doses. Finally, seven H5 viruses representing different phylogenetic clades were evaluated for their antigenic relatedness by hemagglutination inhibition assay, showing that the antigenic relatedness was largely associated with geographic origin. Overall, the data support the conclusion that North American H5 wild-bird-origin AI viruses are low-pathogenicity wild-bird-adapted viruses and are antigenically and genetically distinct from the highly pathogenic Asian H5N1 virus lineage. [ABSTRACT FROM AUTHOR]

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Ltd.)