RESUMO
Since 2012, H7N3 highly pathogenic avian influenza (HPAI) has produced negative economic and animal welfare impacts on poultry in central Mexico. In the present study, chickens were vaccinated with two different recombinant fowlpox virus vaccines (rFPV-H7/3002 with 2015 H7 hemagglutinin [HA] gene insert, and rFPV-H7/2155 with 2002 H7 HA gene insert), and were then challenged three weeks later with H7N3 HPAI virus (A/chicken/Jalisco/CPA-37905/2015). The rFPV-H7/3002 vaccine conferred 100% protection against mortality and morbidity, and significantly reduced virus shed titers from the respiratory and gastrointestinal tracts. In contrast, 100% of sham and rFPV-H7/2155 vaccinated birds shed virus at higher titers and died within 4â¯days. Pre- (15/20) and post- (20/20) challenge serum of birds vaccinated with rFPV-H7/3002 had antibodies detectable by hemagglutination inhibition (HI) assay using challenge virus antigen. However, only a few birds (3/20) in the rFPV-H7/2155 vaccinated group had antibodies that reacted against the challenge strain but all birds had antibodies that reacted against the homologous vaccine antigen (A/turkey/Virginia/SEP-66/2002) (20/20). One possible explanation for differences in vaccines efficacy is the antigenic drift between circulating viruses and vaccines. Molecular analysis demonstrated that the Mexican H7N3 strains have continued to rapidly evolve since 2012. In addition, we identified in silico three potential new N-glycosylation sites on the globular head of the H7 HA of A/chicken/Jalisco/CPA-37905/2015 challenge virus, which were absent in 2012 H7N3 outbreak virus. Our results suggested that mutations in the HA antigenic sites including increased glycosylation sites, accumulated in the new circulating Mexican H7 HPAIV strains, altered the recognition of neutralizing antibodies from the older vaccine strain rFPV-H7/2155. Therefore, the protective efficacy of novel rFPV-H7/3002 against recent outbreak Mexican H7N3 HPAIV confirms the importance of frequent updating of vaccines seed strains for long-term effective control of H7 HPAI virus.
Assuntos
Varíola Aviária/prevenção & controle , Vírus da Influenza A Subtipo H7N3/imunologia , Vacinas contra Influenza/imunologia , Vacinas de DNA/imunologia , Animais , Anticorpos Antivirais/imunologia , Varíola Aviária/imunologia , Varíola Aviária/mortalidade , Varíola Aviária/virologia , Glicoproteínas de Hemaglutininação de Vírus da Influenza/química , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Glicoproteínas de Hemaglutininação de Vírus da Influenza/imunologia , Vírus da Influenza A Subtipo H7N3/classificação , Vírus da Influenza A Subtipo H7N3/genética , Vacinas contra Influenza/administração & dosagem , México , Filogenia , Vacinas de DNA/administração & dosagem , Eliminação de Partículas ViraisRESUMO
In the spring of 2012 an outbreak of H7N3 highly pathogenic (HP) avian influenza virus (AIV) occurred in poultry in Mexico. Vaccination was implemented as a control measure, along with increased biosecurity and surveillance. At that time there was no commercially available H7 AIV vaccine in North America; therefore, a recent H7N3 wild bird isolate of low pathogenicity from Mexico (A/cinnamon teal/Mexico/2817/2006 H7N3) was selected and utilized as the vaccine seed strain. In these studies, the potency and efficacy of this vaccine strain was evaluated in chickens against challenge with the 2012 Jalisco H7N3 HPAIV. Although vaccine doses of 256 and 102 hemagglutinating units (HAU) per bird decreased morbidity and mortality significantly compared to sham vaccinates, a dose of 512 HAU per bird was required to prevent mortality and morbidity completely. Additionally, the efficacy of 11 other H7 AIV vaccines and an antigenic map of hemagglutination inhibition assay data with all the vaccines and challenge viruses were evaluated, both to identify other potential vaccine strains and to characterize the relationship between genetic and antigenic distance with protection against this HPAIV. Several other isolates provided adequate protection against the 2012 Jalisco H7N3 lineage, but antigenic and genetic differences were not clear indicators of protection because the immunogenicity of the vaccine seed strain was also a critical factor.
Assuntos
Vírus da Influenza A Subtipo H7N3/imunologia , Vacinas contra Influenza/imunologia , Influenza Aviária/imunologia , Doenças das Aves Domésticas/imunologia , Animais , Anticorpos Antivirais/imunologia , Galinhas , Mapeamento de Epitopos , Testes de Inibição da Hemaglutinação , Glicoproteínas de Hemaglutininação de Vírus da Influenza/administração & dosagem , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Glicoproteínas de Hemaglutininação de Vírus da Influenza/imunologia , Vírus da Influenza A Subtipo H7N3/genética , Vírus da Influenza A Subtipo H7N3/fisiologia , Vacinas contra Influenza/administração & dosagem , Vacinas contra Influenza/genética , Influenza Aviária/prevenção & controle , Influenza Aviária/virologia , México , Doenças das Aves Domésticas/prevenção & controle , Doenças das Aves Domésticas/virologia , VacinaçãoRESUMO
In June of 2012, an H7N3 highly pathogenic avian influenza (HPAI) virus was identified as the cause of a severe disease outbreak in commercial laying chicken farms in Mexico. The purpose of this study was to characterize the Mexican 2012 H7N3 HPAI virus (A/chicken/Jalisco/CPA1/2012) and determine the protection against the virus conferred by different H7 inactivated vaccines in chickens. Both adult and young chickens intranasally inoculated with the virus became infected and died at between 2 and 4 days postinoculation (p.i.). High virus titers and viral replication in many tissues were demonstrated at 2 days p.i. in infected birds. The virus from Jalisco, Mexico, had high sequence similarity of greater than 97% to the sequences of wild bird viruses from North America in all eight gene segments. The hemagglutinin gene of the virus contained a 24-nucleotide insert at the hemagglutinin cleavage site which had 100% sequence identity to chicken 28S rRNA, suggesting that the insert was the result of nonhomologous recombination with the host genome. For vaccine protection studies, both U.S. H7 low-pathogenic avian influenza (LPAI) viruses and a 2006 Mexican H7 LPAI virus were tested as antigens in experimental oil emulsion vaccines and injected into chickens 3 weeks prior to challenge. All H7 vaccines tested provided ≥90% protection against clinical disease after challenge and decreased the number of birds shedding virus and the titers of virus shed. This study demonstrates the pathological consequences of the infection of chickens with the 2012 Mexican lineage H7N3 HPAI virus and provides support for effective programs of vaccination against this virus in poultry.
Assuntos
Surtos de Doenças , Vírus da Influenza A Subtipo H7N3/patogenicidade , Vacinas contra Influenza/imunologia , Influenza Aviária/epidemiologia , Influenza Aviária/virologia , Estruturas Animais/virologia , Animais , Animais Domésticos , Aves , Galinhas , Análise por Conglomerados , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Vírus da Influenza A Subtipo H7N3/imunologia , Vírus da Influenza A Subtipo H7N3/isolamento & purificação , Vacinas contra Influenza/administração & dosagem , Vacinas contra Influenza/isolamento & purificação , Influenza Aviária/patologia , Influenza Aviária/prevenção & controle , México/epidemiologia , Filogenia , RNA Ribossômico 28S/genética , RNA Viral/genética , Recombinação Genética , Homologia de Sequência , Análise de Sobrevida , Vacinas de Produtos Inativados/administração & dosagem , Vacinas de Produtos Inativados/imunologia , Vacinas de Produtos Inativados/isolamento & purificação , Carga Viral , Eliminação de Partículas ViraisRESUMO
Beginning on June 2012, an H7N3 highly pathogenic avian influenza (HPAI) epizootic was reported in the State of Jalisco (Mexico), with some 22.4 million chickens that died, were slaughtered on affected farms or were preemptively culled on neighboring farms. In the current study, layer chickens were vaccinated with a recombinant fowlpox virus vaccine containing a low pathogenic AI (LPAI) H7 gene insert (rFPV-H7-AIV) and an inactivated oil-emulsified H7N3 AIV vaccine, and subsequently challenged against the Jalisco H7N3 HPAIV. All vaccine combinations provided similar and significant protection against mortality, morbidity, and shedding of challenge virus from the respiratory and gastrointestinal tracts. Serological data also suggested analogous protection from HPAIV among immunized birds. Control of the recent Jalisco AIV infection could be achieved by using various combinations of the two vaccines tested. Even though a single dose of rFPV-H7-AIV vaccine at 1-day-of-age would be the most pragmatic option, optimal protection may require a second dose of vaccine administered in the field.