Detection of Japanese encephalitis virus antigens in the CSF using monoclonal antibodies

Abstract

Background: Antigen detection in the CSF is an invaluable tool in the diagnosis of viral infections of the nervous system, especially in the early phase of the illness. Very little information is available on the use of antigen detection in the diagnosis of Japanese encephalitis (JE). Objectives: Evaluation of two monoclonal antibody-based antigen detection methods in the diagnosis of JE in comparison with the detection of virus-specific IgM antibodies in the CSF. Study design: In this study 115 patients with a clinical diagnosis of JE were investigated. A reverse passive haemagglutination test for the detection of soluble JEV antigens, an immunofluorescent assay for the detection of cell-associated antigen and an IgM capture ELISA for the detection of virus specific IgM antibodies in the CSF were used. Results: Laboratory confirmation of JE was possible in 92/115 patients. Virus-specific IgM was detected in 75/92 and JEV antigen was detected in 52/92 patients. Soluble antigen was detected in 37/52, cell-associated antigen in 30/52. There was no significant difference in the sensitivity of the two antigen detection systems used. Conclusions: Diagnosis by antigen detection could be done less frequently than by demonstration of virus-specific IgM antibodies in the spinal fluid. However, antigen detection proved useful during the first week of illness when IgM antibodies were not detected in the CSF.