CXCL13 as a cerebrospinal fluid marker for neurosyphilis in HIV-infected patients with syphilis.

BACKGROUND: Asymptomatic neurosyphilis is more difficult to diagnose in human immunodeficiency virus (HIV)-infected patients because HIV itself can cause cerebrospinal fluid (CSF) pleocytosis. The proportion of CSF lymphocytes that are B cells is elevated in neurosyphilis, suggesting that the CSF concentration of the B cell chemoattractant, chemokine (C-X-C motif) ligand 13 (CXCL13) concentration may also be elevated.
METHODS: CSF and blood were collected from 199 HIV-infected patients with syphilis and neurosyphilis. Serum and CSF CXCL13 concentrations were determined.
RESULTS: Patients with neurosyphilis had higher CSF and serum CXCL13 concentrations compared to patients with syphilis but not neurosyphilis. The odds of having symptomatic neurosyphilis were increased by 2.23-fold for every log increase in CSF CXCL13 concentration and were independent of CSF white blood cell and plasma HIV RNA concentrations, peripheral blood CD4+ T cell count and use of antiretroviral medications. A cut-off of 10 pg/mL CSF CXCL13 had high sensitivity and a cut-off of 250 pg/mL or evidence of intrathecal synthesis of CXCL13 had high specificity for diagnosis of both symptomatic and asymptomatic neurosyphilis. CSF concentrations of CXCL13 declined after treatment for neurosyphilis.
CONCLUSIONS: CSF CXCL13 concentration may be particularly useful for diagnosis of neurosyphilis in HIV-infected patients because it is independent of CSF pleocytosis and markers of HIV disease.