West Nile virus immunoglobulin A (WNV IgA) detection in cerebrospinal fluid in relation to WNV IgG and IgM reactivity.

BACKGROUND

Diagnostic criteria for neurologic involvement in WNV infection include WNV IgM detection in CSF; however, WNV IgM can persist in CSF >6 months. CSF IgA characterizes other flavivirus infections, but WNV IgA in CSF has not been evaluated. WNV IgM in CSF correlates with IgM in serum but the presence of WNV IgA in CSF compared to serum is unknown.

OBJECTIVES

Evaluate WNV IgA detection in CSF as a marker of WNV neuroinvasive infection, initially with samples pre-selected based on WNV IgG and IgM reactivity and subsequently with all available CSF samples submitted for WNV antibody testing over an entire WNV season.

STUDY DESIGN

Selected CSF samples and CSF/serum pairs previously tested for WNV IgG and IgM were assayed for WNV IgA. Subsequently, all available CSF samples tested for WNV antibodies during the 2005 season were tested for WNV IgA, including those where paired sera were available and tested for IgA, IgG and IgM.

RESULTS

For most samples, including paired CSF and serum, the IgA result qualitatively agreed with the IgM result, regardless of the IgG result.

CONCLUSION

IgA detection is equivalent to IgM detection as a marker of WNV infection in CSF.