OBJECTIVETo prepare purified and concentrated coltivirus high titer antigen in order to further detect antibodies against coltivirus in serum sample of patients.

METHODSThe coltivirus in C6/36 cells was cultured and harvested at different time, and the titer was titrated. The virus was purified and concentrated by polyethylene glycol (PEG), and stored at -20 degrees and 4 degrees, with and without glycerol, respectively, then the titer of coltivirus antigen was tested by indirect ELISA. By using the antigen, coltivirus antibodies in serum samples from both suspected Japanese encephalitis (JE) and viral encephalitis (VE) patients were detected.

RESULTSThe highest titer of coltivirus was found at 3-4 weeks of culturing. The antigen titer could be maintained at least for 6 months, especially antigen with glycerol either at 4 degrees or at -30 degrees even for two years. Totally 1141 serum samples from patients diagnosed clinically as JE and VE were tested. The results showed that 130 samples were coltivirus IgM antibody positive and the average positive rate was 11.4% (130/1141). Among 41 samples of paired-serum from patients in Guangzhou Children's Hospital, 9 samples were positive, the positive rate was 22.0% (9/41) in which 5 samples were diagnosed clinically as VE.

CONCLUSIONSStable and purified coltivirus antigen was obtained in order to test coltivirus antibodies as well as development of kits. Coltivirus probably can cause summer-autumn encephalitis in China.