Abstract: To investigate the mechanism of pathogenesis and immune responses caused by classical swine fever virus (CSFV),pigs were experimentally infected with CSFV strain in this study. Inoculated pigs were studied for their humoral and cell-mediated immunity to the virus,using FACS on cytokine marker strained lymphocytes,blocking ELISA and leukocyte count. Pathogenesis evaluation on various tissues and organs were conducted for the pathogenesis of CSFV. Results showed that percentages of CD3^＋,CD4^＋lymphocytes significantly decreased in the infected group,while there was an increase in the percentage of CD8^＋ lymphocytes in laer period of infection. The level of ELISA antibody of CSFV increased from 7 to 14 days after challenge,but the situation of animals did not get better. Total WBC dropped in the experimentally infected pigs during the experiment. Pathological observations demonstrated various degree lesions,bleeding and necrosis in the most of organs from the infected pigs,such as lung,kidney,tonsil and lymph nodes. Those results indicated that CSFV infection would affect innate and adaptive immune responses and cause pathological lesions in the infected pigs.

Key words: CSFV; humarol immunity; cellular immunity