Japanese encephalitis is caused by Japanese encephalitis viruses (JEV) with neurotropism. As one of the most important immune organ, spleen is directly involved in immune response against JEV. However, little research about JEV infection process in spleen has been reported. In this study, immunopathological changes in mouse spleen were analyzed every other day after subcutaneous injection of mice with JEV wild-type strain P3 by immunohistochemistry assay. Immunohistochemistry analysis demonstrated that the number of T lymphocytes was reduced from 0 to 3 DPI, increased from 3 to 7 DPI, and reduced again from 7 to 10 DPI. In addition, neurological dysfunction appeared at 6 DPI. These results suggested that spleen of mice suffered incontrovertible damages in influence of JEV infection. It can also be deduced that the cellular immunity took the crucial part in the first phase of transient viremia against JEV. Moreover, immune response was activated after the immune-depressed period in the first phase of viremia and neurological dysfunction appeared when cellular immunity was activated. Taking together, our research showed distinct immunopathological changes in mice after JEV infection, which enriched our understanding of Japanese encephalitis immunopathogenesis.

Key words: Immunohistochemistry; Japanese encephalitis virus; Mice; Spleen; T lymphocytes