Efficacy of novel recombinant fowlpox vaccine against recent Mexican H7N3 highly pathogenic avian influenza virus

Miria Ferreira Criado,Kateri Bertran,Dong-Hun Lee,Lindsay Killmaster,Christopher B Stephens,Erica Spackman,Mariana Sa E Silva,Emily Atkins,Teshome Mebatsion,Justin Widener,Nikki Pritchard,Hallie King,David E Swayne

doi:10.1016/j.vaccine.2019.03.009

Miria Ferreira Criado, Kateri Bertran + Show 11 more

Open Access

https://doi.org/10.1016/j.vaccine.2019.03.009

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Abstract

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 4 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.

Highlights

The H5 and H7 highly pathogenic (HP) avian influenza (AI) viruses (HPAIV) have been one of the most frequent causes of severe poultry outbreaks around the world [1,2]
Previous studies have characterized the pathobiology of H7N3 HPAIV, and effectiveness of different vaccine seeds strains on protection [4,5,6]
Morbidity and mortality in specific pathogen free (SPF) White Leghorn chickens challenged with HPAIV H7N3 natized for humane reasons

Summary

Introduction

The H5 and H7 highly pathogenic (HP) avian influenza (AI) viruses (HPAIV) have been one of the most frequent causes of severe poultry outbreaks around the world [1,2]. First reported in June 2012, the H7N3 HPAI has affected over 22 million chickens in Jalisco State, Mexico’s most important table egg producing area [2,3]. An immunization campaign using H7 inactivated virus [A/cinnamon teal/Mexico/2817/2006 (H7N3) vaccine strain], and several measures were established to control the disease including quarantine of affected premises, depopulation of infected poultry, and enhanced surveillance for infection in birds [3]. The initial vaccine seed strain (A/cinnamon teal/Mexico/2817/2006 [H7N3] vaccine strain) was protective against the June 2012 outbreak virus (A/chicken/Jalisco/ CPA-12283/2012 [H7N3], Jalisco/12283/2012) [4,5,6]. Since 2013, additional H7N3 HPAIV outbreaks have occurred and affected primarily layers, and some broilers, breeders, and backyard poultry in the Mexico States of Jalisco, Aguascalientes, Guanajuato and Puebla [2]. Outbreaks of H7N3 HPAI in vaccinated flocks have been reported in Mexico since 2016 [8]

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