Morphological Studies On Tropism And Impact Of Japanese Encephalitis Virus On Mice Tissue

Japanese encephalitis virus is a genus Flavivirus member of the Flaviviridae. Japanese encephalitis is serious insect-borne viral disease viral encephalitis and neurotropic virus of encephalitis menacing human and animal health. Vaccination is the control of a reliable method. Currently there is no specific therapy for encephalitis, mainly in support of therapy and symptomatic treatment. The pathogenic mechanism of Japanese encephalitis is essential for control of the disease. However, the pathogenesis of Japanese encephalitis still remains unclear. In this study, mice were used as experimental model and the virus distribution of Japanese encephalitis virus was studied and the histopathology in brain, spleen and other organs was studied.This paper studies the following aspects:1. Histopathology of various organs in mice after Japanese encephalitis virus infectionIn this experiment,4 week old female SPF BALB/c mice were used as experimental animals, histopathology changes of mouse tissues and organs structure was detected under the influence of Japanese encephalitis virus. The results show as below:mice have significant pathological changes in the brain after Japanese encephalitis virus infection, and spleen also showed pathological changes. The mouse brain showed obvious symptoms of non-suppurative encephalitis. Histological changes were neuronal necrosis, vascular sleeve, microglia nodules, astrocytes and microglia activation phenomenon. Spleen in the infected group showed change of lymphocytes number. White pulp decreased and red pulp area increased, and the reduction of white pulp and increasement of red pulp showed some regulation with time. From 2th day to 4th day after infection, a large number of blood cells assembled in the red pulp. In the 6th day after infection, there was slight increase of white pulp and small reduction in the red pulp. In the 8-10 days after infection, the white pulp area was significantly increased, and in a large number of lymphocytes proliferated in white pulp, red pulp area was significantly reduced. In normal control, the lymphocytes in mouse spleen did not change significantly. In other organs such as liver, thymus, kidney, lung, skin, stomach, the organizational structure did not show significant abnormalities. The results showed the neural tropism of Japanese encephalitis virus.The results also showed less impact on other organizations. Number change of lymphocytes in spleen showed that lymphocytes may play a role in the walk of Japanese encephalitis virus in the peripheral tissue.2. Immunohistochemical and apoptosis analysis of brain in mice after Japanese encephalitis virus infectionInfluence of the JEV on the brain of mice was studied with immunohistochemical method. In infected group, blood vessels in brain showed congestion and bleeding. There was neuronal necrosis and eosinophilic phenomenon. Phenomenon of neuronal and blood vessels was found. In this study, mice were inoculated subcutaneously at neck virulent Japanese encephalitis virus P3 and immunohistochemistry study in mouse brain was done. The results show that direct infection of brain neurons, mouse brain also showed significant changes in the nerve inflammation, such as the most astrocyte processes elongated and stretched. Astrocytes showed obvious activated, especially in hippocampus. Microglial cell processes extend, and they also showed significant activation. Nerve inflammation, would play a protective role in neurons, however excessive inflammation and nerve will damage them.Apoptosis was in research by TUNEL method, mice infected with virulent strain of JE virus P3 apoptosis after brain was studied. Strong fluorescence signal was found in brain vascular endothelial cells. The result suggest that brain vascular endothelial cells in the Japanese encephalitis virus showed obvious apoptosis under the influence of JE vuris, which explains the way encephalitis virus breakthrough blood-brain barrier to a certain extent.3. Immunohistochemical and apoptosis analysis of spleen in mice after Japanese encephalitis virus infectionImmunohistochemistry analysis appeared that after infection the number of T lymphocytes reduced in 0 days to 3 days, increased in 3 days to 7 days, and fell again in 7 days to 10 days. In addition, the neurological dysfunction appeared in 6 days after infection. These results suggest that spleen has injury after the Japanese encephalitis virus infection. We can deduce that, cellular immunity against Japanese encephalitis virus plays an important role in the first phase of viremia. In addition, the immune response was activated after the first phase of viremia after the activation of immune suppression, and neurological dysfunction occurs in the cell immune activation. Our research showed that the unique immunopathological changes in mice after Japanese encephalitis virus infection, and further enriched the immunopathogenesis of Japanese encephalitis.Apoptosis was in research by TUNEL method, mice infected with Japanese encephalitis virus strain P3 and apoptosis in spleen were studied. Study found that the spleen under the influence of the Japanese encephalitis virus, no obvious apoptosis appeared. This is consistent with the statement that viruses cause apoptosis of lymphocytes in vivo but not to other organizations, such as apoptosis in the brain. The fluctuation pattern of spleen T lymphocytes reflects the regulation of lymphocyte apoptosis upon other organizations. Splenic self-renewal and apoptosis of lymphocytes in the normal group appear in consistent with assume. While, compared with the normal group in infected group the apoptosis of spleen lymphocyte had no significant difference. Therefore we suggest that JEV infection did not cause significant apoptosis in the spleen.