The establishment of H9N2 avian influenza virus model in BALB/c mice

Objective To establish H9N2 avian influenza virus model in BALB/c mice.Methods An H9N2 avian influenza virus strain (A/Chicken/Jiangsu/07/2002) was isolated from a farm in Jiangsu Province of China. The HA and NA gene of H9N2 were identified and sequenced by RT-PCR. H9N2 was subjected to three cycles of monoclonal purification. Each cycle consisted of infecting the Madin-Darby canine kidney cells (MDCK) monolayer. BALB/c mice were infected the purified virus by lung-to lung passages. The confirmation of model in mice was evaluated by lethal rate, the loss of weight and the median lethal dose ( LD50). Results H9N2 avian influenza virus can adapt to BALB/c mice by lung-to lung passages, the toxicity of virus in mice was higher as passages, after four passages, it caused the deaths of mice, after ten passages, the LD50 of viruses were 10-2.17. Conclusion H9N2 avian influenza virus can infect mammals by experiment. It can be established a model of studying the avian influenza virus in BALB/c mice.