Cerebrospinal fluid and plasma viral load in HIV-1-infected patients with various anti-retroviral treatment regimens

Changes in Cerebrospinal Fluid Proteins across the Spectrum of Untreated and Treated Chronic HIV-1 Infection

Using the Olink Explore 1536 platform, we measured 1,463 unique proteins in 303 cerebrospinal fluid (CSF) specimens from four clinical centers that included uninfected controls and 12 groups of people living with HIV-1 infection representing the spectrum of progressive untreated and treated chronic infection. We present three initial analyses of these measurements: an overview of the CSF protein features of the sample; correlations of the CSF proteins with CSF HIV-1 RNA and neurofilament light chain protein (NfL) concentrations; and comparison of the CSF proteins in HIV-associated dementia ( HAD ) and neurosymptomatic CSF escape ( NSE ). These reveal a complex but coherent picture of CSF protein changes that includes highest concentrations of many proteins during CNS injury in the HAD and NSE groups and variable protein changes across the course of neuroasymptomatic systemic HIV-1 progression, including two common patterns, designated as lymphoid and myeloid patterns, related to the principal involvement of their underlying inflammatory cell lineages. Antiretroviral therapy reduced CSF protein perturbations, though not always to control levels. The dataset of these CSF protein measurements, along with background clinical information, is posted online. Extended studies of this unique dataset will provide more detailed characterization of the dynamic impact of HIV-1 infection on the CSF proteome across the spectrum of HIV-1 infection, and further the mechanistic understanding of HIV-1-related CNS pathobiology.

Cohort profile: a longitudinal study of HIV infection in the central nervous system with focus on cerebrospinal fluid - the Gothenburg HIV CSF Study Cohort

PURPOSE

In order to enable long-term follow-up of the natural course of HIV infection in the central nervous system, a longitudinal cohort study with repeated cerebrospinal fluid (CSF) analyses at intervals over time was initiated in 1985. When antiretrovirals against HIV were introduced in the late 1980s, short-term and long-term effects of various antiretroviral treatment (ART) regimens were added to the study.

PARTICIPANTS

All adult people living with HIV (PLWH) who were diagnosed at or referred to the Department of Infectious Diseases, Sahlgrenska University Hospital, Gothenburg, Sweden were asked to participate in the Gothenburg HIV CSF Study Cohort. PLWH with neurological symptoms or other clinical symptoms of HIV, as well as those with no symptoms of HIV infection, were included. Most participants were asymptomatic, which distinguishes this cohort from most other international HIV CSF studies. In addition, HIV-negative controls were recruited. These included people on HIV pre-exposure prophylaxis who served as lifestyle-matched controls to HIV-infected men who have sex with men. Since lumbar puncture (LP) is an invasive procedure, some PLHW only consented to participate in one examination. Furthermore, at the beginning of the study, several participants were lost to follow-up having died from AIDS. Of 662 PLWH where an initial LP was done, 415 agreed to continue with follow-up. Among the 415, 56 only gave permission to be followed with LP for less than 1 year, mainly to analyse the short-term effect of ART. The remaining 359 PLWH were followed up with repeated LP for periods ranging from >1 to 30 years. This group was defined as the 'longitudinal cohort'. So far, on 7 April 2022, 2650 LP and samplings of paired CSF/blood had been performed, providing a unique biobank.

FINDINGS TO DATE

A general finding during the 37-year study period was that HIV infection in the central nervous system, as mirrored by CSF findings, appears early in the infectious course of the disease and progresses slowly in the vast majority of untreated PLWH. Combination ART has been highly effective in reducing CSF viral counts, inflammation and markers of neural damage. Minor CSF signs of long-term sequels or residual inflammatory activity and CSF escape (viral CSF blips) have been observed during follow-up. The future course of these changes and their clinical impact require further studies.

FUTURE PLANS

PLWH today have a life expectancy close to that of non-infected people. Therefore, our cohort provides a unique opportunity to study the long-term effects of HIV infection in the central nervous system and the impact of ART and is an ongoing study.

Compartmentalization of cerebrospinal fluid inflammation across the spectrum of untreated HIV-1 infection, central nervous system injury and viral suppression

OBJECTIVE

To characterize the evolution of central nervous system (CNS) inflammation in HIV-1 infection applying a panel of cerebrospinal fluid (CSF) inflammatory biomarkers to grouped subjects representing a broad spectrum of systemic HIV-1 immune suppression, CNS injury and viral control.

METHODS

This is a cross-sectional analysis of archived CSF and blood samples, assessing concentrations of 10 functionally diverse soluble inflammatory biomarkers by immunoassays in 143 HIV-1-infected subjects divided into 8 groups: untreated primary HIV-1 infection (PHI); four untreated groups defined by their blood CD4+ T lymphocyte counts; untreated patients presenting with subacute HIV-associated dementia (HAD); antiretroviral-treated subjects with ≥1 years of plasma viral suppression; and untreated elite controllers. Twenty HIV-1-uninfected controls were included for comparison. Background biomarkers included blood CD4+ and CD8+ T lymphocytes, CSF and blood HIV-1 RNA, CSF white blood cell (WBC) count, CSF/blood albumin ratio, CSF neurofilament light chain (NfL), and CSF t-tau.

FINDINGS

HIV-1 infection was associated with a broad compartmentalized CSF inflammatory response that developed early in its course and changed with systemic disease progression, development of neurological injury, and viral suppression. CSF inflammation in untreated individuals without overt HAD exhibited at least two overall patterns of inflammation as blood CD4+ T lymphocytes decreased: one that peaked at 200-350 blood CD4+ T cells/μL and associated with lymphocytic CSF inflammation and HIV-1 RNA concentrations; and a second that steadily increased through the full range of CD4+ T cell decline and associated with macrophage responses and increasing CNS injury. Subacute HAD was distinguished by a third inflammatory profile with increased blood-brain barrier permeability and robust combined lymphocytic and macrophage CSF inflammation. Suppression of CSF and blood HIV-1 infections by antiretroviral treatment and elite viral control were associated with reduced CSF inflammation, though not fully to levels found in HIV-1 seronegative controls.

Herpes zoster in HIV-1 infection: The role of CSF pleocytosis in secondary CSF escape and discordance

HIV cerebrospinal fluid (CSF) escape is defined by a concentration of HIV-1 RNA in CSF above the lower limit of quantification of the employed assay and equal to or greater than the plasma HIV-1 RNA level in the presence of treatment-related plasma viral suppression, while CSF discordance is similarly defined by equal or higher CSF than plasma HIV-1 RNA in untreated individuals. During secondary CSF escape or discordance, disproportionate CSF HIV-1 RNA develops in relation to another infection in addition to HIV-1. We performed a retrospective review of people living with HIV receiving clinical care at Sahlgrenska Infectious Diseases Clinic in Gothenburg, Sweden who developed uncomplicated herpes zoster (HZ) and underwent a research lumbar puncture (LP) within the ensuing 150 days. Based on treatment status and the relationship between CSF and plasma HIV-1 RNA concentrations, they were divided into 4 groups: i) antiretroviral treated with CSF escape (N = 4), ii) treated without CSF escape (N = 5), iii) untreated with CSF discordance (N = 8), and iv) untreated without CSF discordance (N = 8). We augmented these with two additional cases of secondary CSF escape related to neuroborreliosis and HSV-2 encephalitis and analyzed these two non-HZ cases for factors contributing to CSF HIV-1 RNA concentrations. HIV-1 CSF escape and discordance were associated with higher CSF white blood cell (WBC) counts than their non-escape (P = 0.0087) and non-discordant (P = 0.0017) counterparts, and the CSF WBC counts correlated with the CSF HIV-1 RNA levels in both the treated (P = 0.0047) and untreated (P = 0.002) group pairs. Moreover, the CSF WBC counts correlated with the CSF:plasma HIV-1 RNA ratios of the entire group of 27 subjects (P = <0.0001) indicating a strong effect of the CSF WBC count on the relation of the CSF to plasma HIV-1 RNA concentrations across the entire sample set. The inflammatory response to HZ and its augmenting effect on CSF HIV-1 RNA was found up to 5 months after the HZ outbreak in the cross-sectional sample and, was present for one year after HZ in one individual followed longitudinally. We suggest that HZ provides a ‘model’ of secondary CSF escape and discordance. Likely, the inflammatory response to HZ pathology provoked local HIV-1 production by enhanced trafficking or activation of HIV-1-infected CD4+ T lymphocytes. Whereas treatment and other systemic factors determined the plasma HIV-1 RNA concentrations, in this setting the CSF WBC counts established the relation of the CSF HIV-1 RNA levels to this plasma set-point.

Interactions between prostaglandins, leukotrienes and HIV-1: possible implications for the central nervous system

In HIV-1-infected individuals, there is often discordance between viremia in peripheral blood and viral load found in the central nervous system (CNS). Although the viral burden is often lower in the CNS compartment than in the plasma, neuroinflammation is present in most infected individuals, albeit attenuated by the current combined antiretroviral therapy. The HIV-1-associated neurological complications are thought to result not only from direct viral replication, but also from the subsequent neuroinflammatory processes. The eicosanoids - prostanoids and leukotrienes - are known as potent inflammatory lipid mediators. They are often present in neuroinflammatory diseases, notably HIV-1 infection. Their exact modulatory role in HIV-1 infection is, however, still poorly understood, especially in the CNS compartment. Nonetheless, a handful of studies have provided evidence as to how these lipid mediators can modulate HIV-1 infection. This review summarizes findings indicating how eicosanoids may influence the progression of neuroAIDS.

Impact of short-term combined antiretroviral therapy on brain virus burden in simian immunodeficiency virus-infected and CD8+ lymphocyte-depleted rhesus macaques

Antiretroviral drugs suppress virus burden in the cerebrospinal fluid of HIV-infected individuals; however, the direct effect of antiretrovirals on virus replication in brain parenchyma is poorly understood. We investigated the effect of short-term combined antiretroviral therapy (CART) on brain virus burden in rhesus monkeys using the CD8-depletion model of accelerated simian immunodeficiency virus (SIV) encephalitis. Four monkeys received CART (consisting of the nonpenetrating agents PMPA and RCV) for four weeks, beginning 28 days after SIV inoculation. Lower virus burdens were measured by real-time RT-PCR in four of four regions of brain from monkeys that received CART as compared with four SIV-infected, untreated controls; however, the difference was only significant for the frontal cortex (P < 0.05). In contrast, significantly lower virus burdens were measured in plasma and four of five lymphoid compartments from animals that received CART. Surprisingly, despite normalization of neuronal function in treated animals, the numbers of activated macrophages/microglia and the magnitude of TNF-alpha mRNA expression in brain were similar between treated animals and controls. These results suggest that short-term therapy with antiretrovirals that fail to penetrate the blood-cerebrospinal fluid barrier can reduce brain virus burden provided systemic virus burden is suppressed; however, longer treatment may be required to completely resolve encephalitic lesions and microglial activation, which may reflect the longer half-life of the principal target cells of HIV/SIV in the brain (macrophages) versus lymphoid tissues (T lymphocytes).

Amyloid and tau cerebrospinal fluid biomarkers in HIV infection

Background

Because of the emerging intersections of HIV infection and Alzheimer's disease, we examined cerebrospinal fluid (CSF) biomarkers related of amyloid and tau metabolism in HIV-infected patients.

Methods

In this cross-sectional study we measured soluble amyloid precursor proteins alpha and beta (sAPPα and sAPPβ), amyloid beta fragment 1-42 (Aβ_1-42), and total and hyperphosphorylated tau (t-tau and p-tau) in CSF of 86 HIV-infected (HIV+) subjects, including 21 with AIDS dementia complex (ADC), 25 with central nervous system (CNS) opportunistic infections and 40 without neurological symptoms and signs. We also measured these CSF biomarkers in 64 uninfected (HIV-) subjects, including 21 with Alzheimer's disease, and both younger and older controls without neurological disease.

Results

CSF sAPPα and sAPPβ concentrations were highly correlated and reduced in patients with ADC and opportunistic infections compared to the other groups. The opportunistic infection group but not the ADC patients had lower CSF Aβ_1-42 in comparison to the other HIV+ subjects. CSF t-tau levels were high in some ADC patients, but did not differ significantly from the HIV+ neuroasymptomatic group, while CSF p-tau was not increased in any of the HIV+ groups. Together, CSF amyloid and tau markers segregated the ADC patients from both HIV+ and HIV- neuroasymptomatics and from Alzheimer's disease patients, but not from those with opportunistic infections.

Conclusions

Parallel reductions of CSF sAPPα and sAPPβ in ADC and CNS opportunistic infections suggest an effect of CNS immune activation or inflammation on neuronal amyloid synthesis or processing. Elevation of CSF t-tau in some ADC and CNS infection patients without concomitant increase in p-tau indicates neural injury without preferential accumulation of hyperphosphorylated tau as found in Alzheimer's disease. These biomarker changes define pathogenetic pathways to brain injury in ADC that differ from those of Alzheimer's disease.

Darunavir concentrations in cerebrospinal fluid and blood in HIV-1-infected individuals

Darunavir is the most recently licensed protease inhibitor currently used in treatment-experienced HIV-infected individuals. Our objective was to determine darunavir concentrations in cerebrospinal fluid (CSF) and plasma in subjects receiving antiretroviral treatment regimens containing ritonavir-boosted darunavir. Darunavir concentrations were determined by liquid chromatography tandem mass spectrometry in 14 paired CSF and plasma samples from eight HIV-1-infected individuals. The lower limit of quantification was 5.0 ng/ml. All of the 14 CSF samples had detectable darunavir concentrations with a median darunavir concentration of 34.2 ng/ml (range 15.9-212.0 ng/ml). The median (range) plasma darunavir concentration was 3930 (1800-12900) ng/ml. All CSF samples had detectable darunavir concentrations. Most of them exceeded or were in the same range as levels needed to inhibit replication of wild type virus, making it probable that darunavir, at least to some extent, contributes to the suppression of HIV replication in the central nervous system.

Persistent intrathecal immune activation in HIV-1-infected individuals on antiretroviral therapy

BACKGROUND

Neopterin is a well-established marker of macrophage activation. The cerebrospinal fluid (CSF) neopterin levels are elevated in most HIV-1-infected individuals and decrease significantly after initiation of antiretroviral therapy (ART). Unexpectedly, CSF concentrations often remain mildly abnormal even in patients treated for a long time with suppressive ART. The aims of this study were to analyze if persistently elevated CSF neopterin levels were associated with the type of antiretroviral regimen or with low-level CSF HIV-1 concentrations and to evaluate if plasma HIV-1 RNA levels correlated to lingering CSF neopterin concentrations in patients with effective ART.

METHODS

One hundred fifty-seven chronically HIV-1-infected patients with stable ART for > or =6 months and no neurologic symptoms were included, and 193 HIV-1-infected patients without ART served as controls. Neopterin was analyzed with a radioimmunoassay or an enzyme-linked immunosorbent assay. HIV-1 RNA quantification was performed with the Roche Amplicor assay (version 1.5; Hoffman-La Roche, Basel, Switzerland). Two quantitative HIV-1 RNA assays with sensitivities < or =2.5 copies/mL were used in 40 samples.

RESULTS

As anticipated, HIV-1 RNA and CSF neopterin levels were markedly lower in patients on ART compared with untreated controls. No significant difference in CSF neopterin concentrations was found between those treated with protease inhibitor- and nonnucleoside reverse transcriptase inhibitor-based regimens in combination with 2 nucleoside analogues. Subjects with CSF HIV-1 RNA loads <2.5 copies/mL had the lowest CSF neopterin levels. Plasma viral load had no impact on intrathecal immune activation in cases with CSF viral loads <50 copies/mL.

CONCLUSION

The persistent intrathecal cell-mediated immune response was associated with CSF viral load but not with treatment regimen in individuals on ART.

Factors influencing cerebrospinal fluid and plasma HIV-1 RNA detection rate in patients with and without opportunistic neurological disease during the HAART era

Background

In the central nervous system, HIV replication can occur relatively independent of systemic infection, and intrathecal replication of HIV-1 has been observed in patients with HIV-related and opportunistic neurological diseases. The clinical usefulness of HIV-1 RNA detection in the cerebrospinal fluid (CSF) of patients with opportunistic neurological diseases, or the effect of opportunistic diseases on CSF HIV levels in patients under HAART has not been well defined. We quantified CSF and plasma viral load in HIV-infected patients with and without different active opportunistic neurological diseases, determined the characteristics that led to a higher detection rate of HIV RNA in CSF, and compared these two compartments.

Methods

A prospective study was conducted on 90 HIV-infected patients submitted to lumbar puncture as part of a work-up for suspected neurological disease. Seventy-one patients had active neurological diseases while the remaining 19 did not.

Results

HIV-1 RNA was quantified in 90 CSF and 70 plasma samples. The HIV-1 RNA detection rate in CSF was higher in patients with neurological diseases, in those with a CD4 count lower than 200 cells/mm³, and in those not receiving antiretroviral therapy, as well as in patients with detectable plasma HIV-1 RNA. Median viral load was lower in CSF than in plasma in the total population, in patients without neurological diseases, and in patients with toxoplasmic encephalitis, while no significant difference between the two compartments was observed for patients with cryptococcal meningitis and HIV-associated dementia. CSF viral load was lower in patients with cryptococcal meningitis and neurotoxoplasmosis under HAART than in those not receiving HAART.

Conclusion

Detection of HIV-1 RNA in CSF was more frequent in patients with neurological disease, a CD4 count lower than 200 cells/mm³ and detectable plasma HIV-1. Median HIV-1 RNA levels were generally lower in CSF than in plasma but some patients showed higher CSF levels, and no difference between these two compartments was observed in patients with cryptococcal meningitis and HIV-associated dementia, suggesting the presence of intrathecal viral replication in these patients. HAART played a role in the control of CSF HIV levels even in patients with cryptococcal meningitis and neurotoxoplasmosis in whom viral replication is potentially higher.

Cerebrospinal fluid HIV-1 RNA, intrathecal immunoactivation, and drug concentrations after treatment with a combination of saquinavir, nelfinavir, and two nucleoside analogues: the M61022 study

BACKGROUND

The way various antiretroviral drugs and drug combinations affect HIV-1 infection in the central nervous system is still largely unknown. The aim of this study was to determine the cerebrospinal fluid (CSF) steady-state concentrations of saquinavir and nelfinavir in relation to plasma concentrations, and to study their effect in combination with two nucleoside reverse transcriptase inhibitors (NRTIs) on CSF viral loads, intrathecal immunoactivation, and blood-brain barrier integrity.

METHODS

Paired CSF and plasma samples from 8 antiretroviral-naïve HIV-1 infected patients starting combination therapy with saquinavir, nelfinavir, and two nucleoside analogues were collected prior to treatment, and again after approximately 12 and 48 weeks of antiretroviral therapy. Additional plasma samples were taken at weeks 2, 4, 8, 24, and 36. The concentrations of protease inhibitors were analysed, as were levels of HIV-1 RNA, CD4+ T-cell count, beta2-microglobulin, neopterin, albumin ratio, IgG index, and monocytic cell count.

RESULTS

None of the patients in the study presented with HIV-1 RNA < 50 copies/mL in CSF or plasma prior to treatment, compared to 5/7 at the end of the study. Signs of cell-mediated intrathecal immunoactivation, measured by neopterin and beta2-microglobulin, decreased significantly in both CSF and serum, although only 1/7 reached normal CSF neopterin levels after 48 weeks of treatment. There was no significant reduction of albumin ratio, IgG index or CSF monocytic cell count. Saquinavir median (range) concentrations were < 2.5 (< 2.5-96.0) nM unbound in plasma, and < 2.5 (< 2.5-9.0) nM total in CSF. Nelfinavir median (range) concentrations were 10.0 (< 2.0-31.0) nM unbound in plasma, and < 2.0 (< 2.0-23.0) nM total in CSF. Saquinavir and nelfinavir were detectable in 7/15 and 9/15 CSF samples, respectively.

CONCLUSION

Saquinavir and nelfinavir, in combination with two NRTIs, decrease the CSF viral load and, to a lesser extent, intrathecal immunoactivation. We found reasonably high CSF concentrations of nelfinavir, but suboptimal concentrations of saquinavir.

Cerebrospinal Fluid HIV-1 Infection Usually Responds Well to Antiretroviral Treatment

The primary objective of this retrospective study was to determine how many patients in routine practice who were treated with combination antiretroviral treatment reached HIV-1 RNA levels below 50–400 copies/ml in cerebrospinal fluid (CSF). Seventy-four antiretroviral-naive HIV-1-infected patients from five different centres in Germany, Italy, Sweden and the USA were included. Thirty-nine percent of the patients had a HIV-1-associated neurological disease and 53% of the patients had AIDS. HIV-1 RNA in CSF and plasma were quantified before and after approximately 3 months of treatment. At baseline, the median value of HIV-1 RNA in CSF was 4.12 log copies/ml (interquartile range (IQR): 3.28–4.85) and it decreased to <1.70 log copies/ml (IQR: <1.70–2.48; P<0.001) after in median 3 months of treatment. Seventy-six percent of the patients had HIV-1 RNA levels below the limits of detection in CSF at follow-up, and 85% reached below 400 copies/ml. In plasma, 45% of the patients had levels of HIV-1 RNA below the limits of detection at follow-up and 80% reached below 400 copies/ml. The group of patients with a neurological disease had a significantly higher CSF viral load both at baseline and at follow-up compared with the neurologically asymptomatic patients. We conclude that the central nervous system (CNS) is usually not a ‘sanctuary site’, difficult to reach with combination anti-retroviral treatment.

Suppression of cerebrospinal fluid HIV burden in antiretroviral naive patients on a potent four-drug antiretroviral regimen

OBJECTIVE

To determine the longitudinal response of HIV in the cerebrospinal fluid (CSF) to highly active antiretroviral therapy (HAART) and to investigate the levels of indinavir penetrating into the CSF.

DESIGN

Open study of HIV-infected subjects naive to therapy with protease inhibitors.

SETTING

Tertiary care referral center.

SUBJECTS

Twenty-five participants were begun on indinavir, nevirapine, zidovudine, and lamivudine.

INTERVENTIONS

Lumbar punctures were performed prior to therapy and 2 and 6 months after beginning therapy. Plasma and CSF were assayed for routine cell counts, chemistries, HIV load and indinavir levels.

RESULTS

Twenty-two subjects had CSF HIV RNA level data available at all three time points, three others at baseline and 2 months. At month 2 of therapy, nine of 25 (36%) subjects had CSF HIV RNA levels > 50 HIV RNA copies/ml. By 6 months, all 22 subjects had CSF HIV RNA levels < 50 HIV RNA copies/ml. CSF white blood cell counts fell from a baseline mean of 5.3 x 10(6)/l to 1.9 x 10(6)/l (P = 0.013) at 6 months. Plasma indinavir levels declined rapidly while CSF levels remained stable throughout the 8-h dosing interval. The median CSF indinavir level was 71 ng/ml, approximating the upper limit of the 95% inhibitory concentration for indinavir against HIV-1.

CONCLUSIONS

CSF HIV RNA levels cannot be expected to fall below 50 HIV RNA copies/ml even after 2 months of therapy on HAART. Prolonged therapy may be required to suppress HIV levels within the central nervous system.

Persistent Brain Abnormalities in Antiretroviral-Naive HIV Patients 3 Months after Haart

Background

Proton magnetic resonance spectroscopy (1H-MRS) and neuropsychological tests may be useful for monitoring the effectiveness of highly active antiretroviral therapy (HAART) in HIV-associated brain injury. We aimed to evaluate whether brain abnormalities will improve 3 months after HAART.

Method

Thirty-three HIV patients naive to antiretroviral medications were evaluated before and 3 months after HAART using 1H-MRS and neuropsychological tests; results were compared with those of 26 seronegative control subjects.

Results

Despite significant improvement in CD4 counts, and suppression of plasma and cerebrospinal fluid (CSF) viral loads, elevated brain metabolites (choline compounds and myoinositol in the frontal lobes) and neuropsychological tests abnormalities (including the computerized tests [CalCAP®]) persisted after 3 months of HAART. In the basal ganglia, choline and myoinositol became elevated only after treatment. No interaction effect was observed between the number of CSF-penetrating drugs (one vs two) and changes (baseline vs 3 months) in any of the brain metabolites, cognitive performance or CSF viral load.

Conclusions

The persistent brain abnormalities suggest ongoing repair or reactive inflammatory processes in the brain after 3 months of HAART. Regimens with two CSF-penetrating antiretroviral medications do not appear to be more effective than those with one CSF-penetrating drug in treating HIV brain injury at 3 months.

Clinical applications of new cerebrospinal fluid analytic techniques for the diagnosis and treatment of central nervous system infections

Advances in molecular biology and immunology provide new, highly sensitive and specific techniques that can be applied to analysis of cerebrospinal fluid to enhance the diagnosis and treatment of central nervous system (CNS) infections. In addition to improved accuracy and speed of diagnosis, these modalities may offer improved means of monitoring treatment efficacy, establishing prognosis, detecting organism resistance, and tracking epidemic sources. This brief review discusses a number of recent papers applying these methods, in order to illustrate their value and significance for clinical neurologic practice. Some of these applications are commonly available, whereas others are likely to enter the physician's armamentarium in the near future. As they do, they can be expected to improve the treatment of CNS infections.

Antiretroviral treatment of central nervous system HIV-1 infection: a review

HIV-1 infects the central nervous system (CNS) and it has been feared that the CNS may be a sanctuary site where HIV-1 could hide and continue to replicate despite otherwise effective antiretroviral treatment. Neurological HIV-1 related symptoms, cerebrospinal fluid (CSF) viral load, intrathecal immunoactivation and CSF drug concentration measurements are considered in this review of antiretroviral treatment effects on CNS HIV-1 infection. We conclude that antiretroviral combination treatment regimens improve neurocognitive symptoms in HIV-1 infection and substantially lower CSF viral load. The threat of an increasing number of patients with neurological symptoms and continued HIV-1 replication in the brain despite otherwise effective antiretroviral therapy has not yet proved to be a problem. It is, however, important to keep this potential risk in mind, and more longitudinal prospective studies addressing the issue of antiretroviral treatment effects on CNS HIV-1 infection are needed.