The Research Of Tissue Injury And Apoptosis In The Brain Of Chicken Infected With H9N2 Avian Influenza Virus

The H9N2 subtype avian influenza virus is low pathogenic avian influenza virus, and widely distributed around the world. Avian infected with H9N2 subtype avian influenza virus not only show clinical symptoms, including cough, dyspnea, yellowish green stools, egg production dropping, also cause nerve symptoms, such as wryneck and stretch the neck. To the best of our knowledge, the tissue injury in the brain of chicken infected with H9N2 avian influenza virus rarely reported. To clarify the pathogenesis of chicken?s brain damage after H9N2 subtype AIV infection, 10-week old chicken were inoculated with H9N2 subtype of AIV(A/chicken/Shaanxi/11/2012) through combined intra-ocular and intra-nasal routes in the present study. HE staining was used to detect the pathological changes in tissues. TUNEL staining and Caspase-3 enzyme activity detection were used for determing the tissue apoptosis. The results were as follows:This experiment using 10-week old chicken inoculated with H9N2 subtype of AIV(A/chicken/Shaanxi/11/2012) through combined intra-ocular and intra-nasal routes. Birds were randomly divided into two groups. The first group of birds was used as uninfected controls, and birds in the second group were inoculated with H9N2 AIV. At 0, 2, 4, 6, 8, and 15 days post inoculation(p.i.), five chickens were selected at random from each group. The clinical symptoms of infected chicken showed depression, yellowish green stools and eyelid swelling. Some had neurological symptoms. The histological lesions of the infected chicken brain tissue by HE staining showed vasodilation and congestion under the pia mater of cerebrum tissue, neuronal degeneration and necrosis, and multiple microglial cells intrusion can be seen in the cytoplasm of degenerative changes neurons; neurons swelling in purkinje cell layer of the epencephalon, nissl body disappeared, cell vacuoles and the nucleus concentration, solution. There was inflammatory cells infiltration in the infected brain, surrounded by blood vessels, gathered in blood vessels forming vascular cuffing.TUNEL staining showed that infection of H9N2 subtype AIV can caused cellular apoptosis in the chicken brain, and with the increase of infected days, cellular apoptosis were more obvious. At 4 day and 6 day post infection, apoptosis is the most serious. Caspase-3 enzyme activities of each of the experimental groups were higher than that in the control group. Apoptosis detection confirmed that infection of H9N2 subtype AIV can induce cellular apoptosis in the brain of chicken.In conclusion, brain tissue had different degree of pathological damage and cellular apoptosis after infected H9N2 subtype AIV infection in the chicken. The more day post infection, the more serious tissue injury and apoptosis, particularly at 4 day and 6 day post infection, the pathological damages are worst. After that, the crowd slowly recovery, chicken returned to normal at 15 dpi. Collectively, this study confirmed that the infection of H9N2 subtype AIV can cause non-suppurative encephalitis lesions in the chicken brain tissue, which resulting neurological symptoms.