Abstract
Syphilis is a frequent coinfection with human immunodeficiency virus (HIV). Whereas systemic syphilis infection increases plasma HIV RNA levels (viral load; VL), effects of syphilis on cerebrospinal fluid (CSF) VL are unknown. We hypothesized that intrathecal immune activation in neurosyphilis would selectively increase CSF VL in coinfected patients. In this study, HIV-infected research subjects (N = 225) were categorized into three groups based on serum rapid plasma reagin (RPR), microhemaglutination for Treponema pallidum (MHA-TP) MHA-TP, and CSF VDRL: 23 with neurosyphilis (NS+; reactive serum RPR and MHA-TP and positive CSF VDRL); 42 with systemic syphilis but not neurosyphilis (Syph+; reactive serum RPR and MHA-TP; negative CSF VDRL), and 160 without syphilis (Syph−; nonreactive serum RPR). Plasma and CSF HIV VL were quantified by reverse transcriptase–ploymerase chain reaction (RT-PCR) (Amplicor, Roche) in log10 copies/ml. To adjust for covariates previously shown to influence CSF HIV VL (i.e., plasma VL, CD4, pleocytosis, and highly active antiretroviral therapy [HAART]), multivariable linear regression was used. Lumbar punctures (LP) done for research purposes diagnosed 23 with neurosyphilis; most (83%) of these reported prior syphilis treatment. Among subjects with detectable plasma VL, CSF VL was highest in NS+, followed by Syph+ and Syph− (P =.006). This relationship was independent of the level of plasma VL or CSF pleocytosis. By contrast, among subjects with undetectable plasma HIV VL, CSF VLs were similar in the three syphilis subgroups (P = .50). Neurosyphilis may amplify intrathecal HIV replication, possibly through immune activation that persists even after syphilis treatment. Because elevated CSF VL is associated with subsequent neurocognitive decline, future studies should evaluate the impact of neurosyphilis on the course of central nervous system (CNS) HIV infection.
Acknowledgments
The San Diego HIV Neurobehavioral Research Center (HNRC) group is affiliated with the University of California, San Diego, the Naval Hospital, San Diego, and the Veterans Affairs San Diego Healthcare System, and includes Director: Igor Grant, MD; Co-Directors: J. Hampton Atkinson, MD, Ronald J. Ellis, MD, PhD, and J. Allen McCutchan, MD; Center Manager: Thomas D. Marcotte, PhD; Heather Bentley, CCRA; Melanie Sherman; Naval Hospital San Diego: Braden R. Hale, MD, MPH (P.I.); Neuromedical Component: Ronald J. Ellis, MD, PhD (P.I.), J. Allen McCutchan, MD, Scott Letendre, MD, Edmund Capparelli, PharmD, Rachel Schrier, PhD; Jennifer Marquie-Beck; Terry Alexander, RN; Neurobehavioral Component: Robert K. Heaton, PhD (P.I.), Mariana Cherner, PhD, Steven Paul Woods, PsyD, David J. Moore, PhD; Matthew Dawson; Neuroimaging Component: Terry Jernigan, PhD (P.I.), Christine Fennema-Notestine, PhD, Sarah L. Archibald, MA, John Hesselink, MD, Jacopo Annese, PhD, Michael J. Taylor, PhD, Brian Schweinsburg, PhD; Neurobiology Component: Eliezer Masliah, MD (P.I.), Ian Everall, FRCPsych, FRCPath, PhD, Cristian Achim, MD, PhD; Neurovirology Component: Douglas Richman, MD, (P.I.), David M. Smith, MD; International Component: J. Allen McCutchan, MD, (P.I.); Developmental Component: Ian Everall, FRCPsych, FRCPath, PhD (P.I.), Stuart Lipton, MD, PhD; Clinical Trials Component: J. Allen McCutchan, MD, J. Hampton Atkinson, MD, Ronald J. Ellis, MD, PhD, Scott Letendre, MD; Participant Accrual and Retention Unit: J. Hampton Atkinson, MD (P.I.), Rodney von Jaeger, MPH; Data Management Unit: Anthony C. Gamst, PhD (P.I.), Clint Cushman (Data Systems Manager), Daniel R. Masys, MD (Senior Consultant); Statistics Unit: Ian Abramson, PhD (P.I.), Florin Vaida, PhD, Christopher Ake, PhD.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.