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.