Abstract
Vietnam is one of the countries most affected worldwide by the highly pathogenic avian influenza (HPAI) virus, which caused enormous economic loss and posed threats to public health. Over nearly two decades, with the antigenic changes in the diversified H5Ny viruses, the limited protective efficacy of the available vaccines was encountered. Therefore, it is necessary to approach a technology platform for the country to accelerate vaccine production that enables quick response to new influenza subtypes. This study utilized a powerful reverse genetics technique to successfully generate a recombinant H5N1 vaccine strain (designated as IBT-RG02) containing two surface proteins (haemagglutinin (HA) and neuraminidase (NA)) from the HPAI H5N1 (A/duck/Vietnam/HT2/2014(H5N1)) of the dominant clade 2.3.2.1c in Vietnam during 2012–2014. Importantly, the IBT-RG02 vaccine candidate has elicited high antibody titres in chickens (geometric mean titre (GMT) of 6.42 and 6.92, log2 on day 14 and day 28 p.i., respectively). To test the efficacy, immunized chickens were challenged with the circulating virulent strains. As results, there was a high protection rate of 91.6% chickens against the virulent A/DK/VN/Bacninh/NCVD-17A384/2017 of the same clade and a cross-protection of 83.3% against A/duck/TG/NAVET(3)/2013 virus of clade 1.1. Our promising results showed that we can independently master the reverse genetics technology for generation of highly immunogenic vaccine candidates, and henceforth, it is a timely manner to reformulate avian influenza virus vaccines against variable H5 clade HPAI viruses in Vietnam.
Highlights
Since the first appearance of the H5N1 epidemic in 2003, this highly pathogenic avian influenza (HPAI) virus has circulated annually in Asia under different subtypes
Sequencing data from all eight gene segments of IBT-RG02 showed that this strain had 100% genetic identity compared to the original DNA
Protection was observed but with a slightly lower percentage (83.3%) compared to 91.6% protection by NAVET-Vifluvac (Table 3). These results showed that IBT-RG02 has a strong ability to protect chicken from H5N1 of at least the two clades tested in the study and could potentially be used as a local avian vaccine candidate
Summary
Since the first appearance of the H5N1 epidemic in 2003, this highly pathogenic avian influenza (HPAI) virus has circulated annually in Asia under different subtypes. Vietnam is among the countries that have suffered the most serious economic losses from H5N1 worldwide, with the destruction of approximately 50 million poultry from more than 3000 outbreaks being reported between 2003. Vaccines 2020, 8, 159 and 2019, causing a yearly loss of 0.5–1.8% of gross domestic product [1,2,3]. Vietnam is the country with the third highest number of infected (127) and fatal (64) cases in humans [4]. Due to traditional poultry-raising practices on a small scale, free trade in poultry between neighbouring countries, and direct exposure to poultry in live bird markets, there is a significantly high risk of viral transmission. Influenza management strategies are necessary to reduce detrimental effects to both humans and poultry. Vaccination has been the best method for protecting poultry from influenza A infection
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