Cross-reactive IgM responses in patients with dengue or Japanese encephalitis

Background: Dengue and Japanese encephalitis viruses co-circulate in Thailand. IgM-capture enzyme-linked immunosorbent assay (ELISA) has been widely used for confirmation of dengue and Japanese encephalitis (JE). Objectives: To examine the cross-reactivity in IgM responses to dengue and JE viruses in serum and CSF samples from dengue and JE patients. Study design: Two hundred and fifty-eight serum samples from 177 confirmed dengue patients, and 99 serum samples and 37 cerebrospinal fluid (CSF) samples from confirmed JE patients were analyzed. Results: Nine percent of serum samples from dengue patients were positive for anti-JE IgM. Thirteen percent of serum samples and 11% of CSF samples from JE patients were positive for anti-dengue IgM. Levels of cross-reactive IgM were lower than those of specific IgM in all the dengue and JE patients. Conclusions: Only specific IgM is detected in about 90% of dengue and JE patients, but cross-reactive IgM is also detected in the remainder. The presence of cross-reactive IgM responses should to be considered in the serodiagnosis of dengue and JE, especially in areas where dengue and JE viruses co-circulate. (c) 2007 Elsevier B.V. All rights reserved.