Cerebrospinal fluid IgM cross-reactivity among arboviruses in Japanese encephalitis patients from southern India.

BACKGROUND

In regions where multiple arboviruses co-circulate, serological diagnosis of neuroinvasive infections is complicated by antibody cross-reactivity. IgM detection in cerebrospinal fluid (CSF) is often considered evidence of etiologic infection.

METHODS

We retrospectively screened CSF samples positive for Japanese encephalitis virus (JEV) IgM for IgM antibodies against dengue virus (DENV), chikungunya virus (CHIKV), and West Nile virus (WNV). Clinical, laboratory, and radiological data were analyzed for a subset of confirmed cases.

RESULTS

Among 60 JEV IgM-positive CSF samples, cross-reactive IgM antibodies were detected against DENV (46.7%), CHIKV (10%), and WNV (23%). Cross-reactive IgM levels were consistently lower than JEV-specific IgM. Poor clinical outcomes were associated with higher CSF leukocyte counts, protein, and lactate levels.

CONCLUSIONS

CSF IgM cross-reactivity among arboviruses is frequent in Japanese encephalitis and may confound etiological diagnosis. Integrated diagnostic algorithms are required in endemic settings.