Preparation of Nam Dinh virus antigen to diagnosis of viral acute encephalitis syndrome, 1998-2004

ABSTRACT

From 2000ml supernatant fluid of infected Aedes albopictus cells clone C6/36, Nam Dinh virus antigen was prepared by ultracentrifuge generating 5ml purified antigen. Protein content of the purified antigen is 4.4 mg/ml and antigen titer stabilizes for two years at - 80oC. The purified antigen was used for detecting IgM against Nam Dinh virus in cerebrospinal fluid from acute encephalitis syndrome patients by indirect IgM-ELISA. The examination of 814 cerebrospinal fluid samples of acute encephalitis syndrome, which were confirmed non-Japanese encephalitis during 1998 - 2004. The positive proportion with Nam Dinh virus antigen has been found to be 6.59 % - 20.06%. Most of positive cases in children were under 15 years old. Acute encephalitis syndrome cases due to Nam Dinh virus mainly occurred in May, June and July, in the same season of Japanese encephalitis in the Northern area of Vietnam.