Pathological analysis and genetic characterization of the first outbreak H5N8 subtype avian influenza virus isolated from wild swan in Shandong, China

Abstract

In January 2021, an outbreak of H5N8 subtype avian influenza was identified from wild mute swans (Cygnus olor) in an overwintering site located within Yellow River Delta Nature Reserve in Shandong, China, for the first time. We sequenced the hemagglutinin (HA) and neuraminidase (NA) genome segments of the virus, named A/mute swan/Shandong/1/2021 (H5N8), and explored the genetic characterization and comparative phylogenetic analysis to track its origin. The wild swans prior to death showed nervous signs accompanied by a twisted neck. The major pathological changes of the heart, lung, trachea, kidney, spleen, and glandular stomach were hemorrhage, and extensive necrotic lesions in the liver and pancreas were also observed. Further analysis of the HA and NA phylogenetic trees generated by H5N8 strains isolated worldwide revealed that the isolate has a close genetic relationship with the H5N8 subtype avian influenza virus (AIV) recently isolated in Korea and Japan from 2020 to 2021, suggesting the potential role of mute swans in the global dissemination of the H5N8 subtype AIVs along the migration routes. Therefore, enhanced active surveillance in wild and domestic birds is required to monitor the introduction and spread of the H5N8 subtype AIV by migratory birds in order to decrease the risk of H5N8 outbreaks.

AddaVax-Adjuvanted H5N8 Inactivated Vaccine Induces Robust Humoral Immune Response against Different Clades of H5 Viruses

“…The whole-virion inactivated influenza vaccine is the main strategy for an avian influenza vaccine design for human use, while the development of a vaccine candidate virus is essential for pandemic preparedness. It has been found that the HA of various avian influenza viruses contains multi-basic cleavage sites that are lethal to chickens, such as arginine (R) and lysine (K) sites in H5Nx and H7Nx [ 7 ], and REKRRKR/GLF in H5N8 [ 8 ]. After deleting the polybasic amino acids at the HA cleavage site of the HPAI parent virus, the new modified HA, along with the NA of the wild virus and the six internal segments of the backbone (such as A/PR/8/1934 H1N1 virus) is frequently used to generate a new low pathogenic virus as a vaccine candidate virus by reverse genetics (RG) [ 9 , 10 ].…”