Abstract：Abstract: From 1999-2002, we had isolated 21 H5N1 subtype avian influenza virus in health ducks from South China, We analyzed the biological properties and the heredity evolution of the H5N1 viruses systematically found that A/Duck/FuJian/01/02(DKFJ) and A/Duck/Guangxi/53/02(DKGX) are genetically similar, which were highly pathogenic to chickens but have different pathogenicity obviously in the BALB/c mice that is a useful mammalian model. DKGX is low pathogenic in mice (MLD50>106.5EID50), the reverse genetics system of DKGX had established in our Laboratory, whereas A/duck/FuJi/01/02 (DKFJ) is highly pathogenic (MLD50<100.5EID50). With the purpose of study the Molecular mechanisms of A duck H5N1 subtype avian influenza Pathogenic difference in mice of the two virus, an eight-plasmid reverse genetics system was established of DKFJ and the reassortant virus was rescued from cell transfection. The rescued virus(R-DKFJ) maintained the same biological properties as the wild virus (W-DKFJ MLD50<100.5). Both of the viruses could be recovered from the brain and spleen and kidney and lung of the Balb/c mice 3 days after inoculated intranasally with 106EID50. The successful establishment of the reverse genetics system of DKFJ will play an important role in the studies of the molecular basis of the evolution and the relationship between the structure and function of H5N1 subtype avian influenza viruses.
