Ho EL, et al. - Researchers in this work tested the hypothesis that neurosyphilis causes cognitive impairment in HIV by amplifying HIV-related central nervous system (CNS) inflammation. As per findings, they conclude that neurosyphilis could aggravate HIV-associated CNS inflammation, but it seemed not explaining cognitive impairment in HIV-infected individuals with syphilis.

Methods

• In a study of cerebrospinal fluid (CSF) abnormalities in syphilis, HIV-infected participants were enrolled; these participants underwent the mental alternation test (MAT), venipuncture, and lumbar puncture.
• Using commercial assays, researchers determined CSF concentrations of chemokine (C-X-C motif) ligand 10 (CXCL10), chemokine (C-C motif) ligand 2 (CCL2), and neurofilament light (NFL).
• Using flow cytometry, they determined the proportion of peripheral blood mononuclear cells (PBMCs) and of CSF white blood cells (WBCs) that were activated monocytes (CD14+CD16+).
• They defined neurosyphilis as detection of Treponema pallidum 16S RNA in CSF or CSF white blood cells (WBCs) >20/uL or a reactive CSF-Venereal Disease Research Laboratory (VDRL) test.
• In this study, uncomplicated syphilis was defined as undetectable CSF T. pallidum, CSF WBCs ≤5/uL and nonreactive CSF-VDRL.
• For this study, MAT <18 was considered low.

Results

• In neurosyphilis, median proportion of PBMCs that were activated monocytes (16.6 vs. 5.3), and median CSF CXCL10 (10658 vs. 2530 units), CCL2 (519 vs. 337 units) and HIV RNA (727 vs. 50 c/mL) were higher in comparison to uncomplicated syphilis (P ≤ .001 for all comparisons).
• There appeared no relation of neurosyphilis with low MAT scores.
• Participants with low MAT scores indicated higher median CSF CXCL10 (10299 vs. 3650 units, P = .008) and CCL2 (519 vs. 365 units, P = .04) concentrations than those with high MAT scores.