Abstract
The H5 highly pathogenic avian influenza viruses (HPAIVs) in China pose a serious challenge to public health and the poultry industry. In this study, we constructed a replication-competent recombinant influenza A virus of clade 2.3.4.4 Н5N1 expressing the clade 2.3.2.1 H5 HA1 protein from a tricistronic NS segment. We used a truncated NS1 protein of 73 amino acids combined with a heterologous dimerization domain to increase protein stability. H5 HA1 and nuclear export information were fused in frame with a truncated NS1 open reading frame, separated by 2A self-processing sites. The resulting PR8-H5-NS1(73)H5 stably expressed clade 2.3.4.4 H5 HA and clade 2.3.2.1 H5 HA1 proteins and exhibited similar in vitro growth kinetics as the parental PR8-2344H5 virus. PR8-H5-NS1(73)H5 induced specific hemagglutination-inhibition (HI) antibody against clade 2.3.4.4 H5 that was comparable to that of the combination vaccine of PR8-2344H5 and PR8-2321H5. HI antibody titers were significantly lower against clade 2.3.2.1 H5 virus than with the combination vaccine. PR8-H5-NS1(73)H5 completely protected chickens from both clade 2.3.4.4 and clade 2.3.2.1 H5 HPAIVs challenge. Our results suggested that PR8-H5-NS1(73)H5 was highly immunogenic and efficacious against both clade 2.3.4.4 and clade 2.3.2.1 H5 HPAIVs in chickens.
Highlights
H5N1 avian influenza viruses (AIVs) have been detected in more than 60 countries and have caused economic losses for the poultry industry worldwide1
A foot-and-mouth disease virus (FMDV) 2A autoprocessing site was inserted between NS1(1–73)Dmd and HA1, with HA1 separated from nuclear export protein (NEP) by a porcine teschovirus-1 (PTV-1) 2A cleavage site (Fig. 1A)
H5N1 AIVs have become enzootic in poultry and wild birds in China2
Summary
H5N1 avian influenza viruses (AIVs) have been detected in more than 60 countries and have caused economic losses for the poultry industry worldwide. Vaccination is an important strategy to control H5N1 AIVs among poultry in mainland China, Hong Kong SAR, Vietnam, Indonesia, and Egypt. The inactivated H5N1 vaccine produced from vaccine strain Re-8 was generated by reverse genetics and contains the HA and NA genes of a clade 2.3.4.4 virus, A/chicken/Guizhou/4/2013(H5N1). The vaccine has been widely used to control clade 2.3.4.4 AIVs in mainland China and Hong Kong since 20166. А/Puerto Rico/8/34 (H1N1) strain was used as the backbone for obtaining influenza A viral vectors expressing H5N1 mature HA1 sequence as fusion protein with the N-terminal 73 amino acid residues of NS1 and expressing HA and NA proteins of clade 2.3.4.4 H5 that replaced the corresponding proteins of PR8 virus. The immunogenicity and protective efficacy in chickens of a bivalent vaccine against challenge with both clade 2.3.4.4 and clade 2.3.2.1 H5 HPAIVs was evaluated
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