Cerebrospinal fluid HIV RNA originates from both local CNS and systemic sources

Transmigration of macrophages across the choroid plexus epithelium in response to the feline immunodeficiency virus

Although lentiviruses such as human, feline and simian immunodeficiency viruses (HIV, FIV, SIV) rapidly gain access to cerebrospinal fluid (CSF), the mechanisms that control this entry are not well understood. One possibility is that the virus may be carried into the brain by immune cells that traffic across the blood-CSF barrier in the choroid plexus. Since few studies have directly examined macrophage trafficking across the blood-CSF barrier, we established transwell and explant cultures of feline choroid plexus epithelium and measured trafficking in the presence or absence of FIV. Macrophages in co-culture with the epithelium showed significant proliferation and robust trafficking that was dependent on the presence of epithelium. Macrophage migration to the apical surface of the epithelium was particularly robust in the choroid plexus explants where 3-fold increases were seen over the first 24 h. Addition of FIV to the cultures greatly increased the number of surface macrophages without influencing replication. The epithelium in the transwell cultures was also permissive to PBMC trafficking, which increased from 17 to 26% of total cells after exposure to FIV. Thus, the choroid plexus epithelium supports trafficking of both macrophages and PBMCs. FIV significantly enhanced translocation of macrophages and T cells indicating that the choroid plexus epithelium is likely to be an active site of immune cell trafficking in response to infection.

HIV type 1 viral encephalitis after development of viral resistance to plasma suppressive antiretroviral therapy

HIV-1 viral encephalitis produced by antiretroviral-resistant strains in cerebrospinal fluid (CSF), despite suppression of plasma HIV-1 RNA, has been rarely described. We report two cases of symptomatic viral encephalitis demonstrated by clinical, magnetic resonance imaging (MRI), and an inflammatory CSF profile. Viral load in CSF was 24,000 and 6850 copies/ml, whereas plasma HIV RNA level was undetectable since the beginning of therapy. A resistance test in CSF showed genotypic mutations confering resistance to the drugs the patients received for more than 2 years. In the two cases, a high baseline HIV RNA level, a low nadir CD4(+) count, and suboptimal CSF levels of atazanavir were considered as the risk factors for developing encephalitis. The two cases did not resolve with a change to antiretroviral drugs with better CNS penetration, but they had complete clinical and MRI recovery after changing to therapy considering both CNS viral resistance and penetration.

HIV-1 replication in the central nervous system occurs in two distinct cell types

Human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system (CNS) can lead to the development of HIV-1-associated dementia (HAD). We examined the virological characteristics of HIV-1 in the cerebrospinal fluid (CSF) of HAD subjects to explore the association between independent viral replication in the CNS and the development of overt dementia. We found that genetically compartmentalized CCR5-tropic (R5) T cell-tropic and macrophage-tropic HIV-1 populations were independently detected in the CSF of subjects diagnosed with HIV-1-associated dementia. Macrophage-tropic HIV-1 populations were genetically diverse, representing established CNS infections, while R5 T cell-tropic HIV-1 populations were clonally amplified and associated with pleocytosis. R5 T cell-tropic viruses required high levels of surface CD4 to enter cells, and their presence was correlated with rapid decay of virus in the CSF with therapy initiation (similar to virus in the blood that is replicating in activated T cells). Macrophage-tropic viruses could enter cells with low levels of CD4, and their presence was correlated with slow decay of virus in the CSF, demonstrating a separate long-lived cell as the source of the virus. These studies demonstrate two distinct virological states inferred from the CSF virus in subjects diagnosed with HAD. Finally, macrophage-tropic viruses were largely restricted to the CNS/CSF compartment and not the blood, and in one case we were able to identify the macrophage-tropic lineage as a minor variant nearly two years before its expansion in the CNS. These results suggest that HIV-1 variants in CSF can provide information about viral replication and evolution in the CNS, events that are likely to play an important role in HIV-associated neurocognitive disorders.

Human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system (CNS) can lead to the development of a severe neurological disease termed HIV-1-associated dementia (HAD). Individuals diagnosed with HAD commonly have genetically distinct HIV-1 variants in their cerebrospinal fluid (CSF) that are not detected in the blood virus population, suggesting that independent viral replication is occurring in the CNS of HIV-1-infected subjects with severe neurological disease. We examined HIV-1 variants in the blood plasma and CSF of HAD subjects to determine the viral characteristics associated with the development of dementia during HIV-1 infection. We found that genetically distinct HIV-1 variants in the CSF of HAD subjects were either R5 T cell-tropic or macrophage-tropic. The R5 T cell-tropic viruses required high levels of the cellular surface receptor CD4 to enter cells, while macrophage-tropic viruses could enter cells with low levels of CD4, suggesting that HIV-1 can replicate in at least two cell types within the CNS during the course of dementia. Finally, macrophage-tropic viruses were detected in the CSF but poorly represented in the blood virus population. Our results suggest that HIV-1 variants in the CSF can provide information about independent viral replication in the CNS during the course of HIV-1 infection.

HIV-1 infection and neurocognitive impairment in the current era

Brain HIV-1-infection may result in a syndrome of profound cognitive, behavioral and motor impairment known as AIDS dementia complex (ADC) in adults and HIV-related encephalopathy in children. Although the introduction of highly active antiretroviral therapy (HAART) has prolonged and improved the lives of infected individuals, it is clear that HAART does not provide complete protection against neurological damage in HIV/AIDS. HIV-1 associated dementia is a complex phenomenon, which could be the result of several mechanisms caused by those players using different intracellular signaling pathways. Understanding the causes of neurodegeneration during HIV-1 infection and the factors which certain individuals develop disease can provide researches on new therapeutic targets to positively affect disease outcomes. Controlling CNS viral replication with HAART is an essential primary approach, but it should be complemented with adjunctive CNS-directed therapeutics. Understanding the nature of HIV-1 infection within the CNS as well as inflammatory responses will ultimately lead to the elimination of HIV-associated neurocognitive disorders.

Curing HIV: Pharmacologic approaches to target HIV-1 latency

HIV-1 infection persists even after years of antiretroviral therapy (ART). Although ART can halt viral replication and thereby reduce viremia to clinically undetectable levels, proviral latency established within the host genome remains largely unaffected by ART and can replenish systemic infection following interruption of therapy. Pharmacologic strategies, which not only target viral replication but also deplete proviral infection, are required for successful clearance of HIV-1 infection. This review highlights the current understanding of molecular mechanisms that establish and maintain HIV-1 latency in its major reservoir, the resting memory CD4(+) T cell. We also identify the molecular targets that might be exploited to induce HIV-1 expression, remove epigenetic restrictions, or enhance effective transcription. Finally, we discuss the potential pharmacologic approaches toward targeting viral persistence in different cellular and anatomical reservoirs to achieve a cure of HIV-1 infection.

Prevalence of non-confounded HIV-associated neurocognitive impairment in the context of plasma HIV RNA suppression

HIV-associated neurocognitive disorder is known to occur in the context of successful combination antiretroviral therapy (cART; plasma HIV RNA <50 copies/ml). Here, we newly provide an analysis of its prevalence and nature in the absence of medical or psychiatric confounds that may otherwise inflate the prevalence rate. We enrolled a cohort of 116 advanced HIV + individuals on cART (51% virally suppressed (VS)). They were screened for active Hepatitis C, current substance use disorder and were assessed with standard neuropsychological (NP) testing. Our results showed that out of the entire sample, NP impairment occurred in 18.1% (21/116) in VS individuals which was not statistically different from the 24.1% (28/116) that were found to be NP-impaired and not VS. In comparison with NP-normal-VS persons, NP impairment in VS individuals was associated with shorter duration of current cART and lower pre-morbid ability. Higher cART CNS penetration effectiveness tended to be associated with lesser cognitive severity in NP-impaired VS individuals. Current CD4 cell count, depression symptoms and past CNS HIV-related diseases did not specifically account for persistent NP impairment in VS individuals. In conclusion, despite suppression of systemic viral load, non-confounded HIV-related NP-impairment prevalence reached 18.1%. Of the potential explanations for this persistent deficit, a "burnt-out" form of the disease and immune reconstitution inflammatory syndrome were the less likely explanations, while a shorter current cART duration and lower pre-morbid intellectual capacity were significant. Nonetheless, predictive modelling with these last two factors misclassified 27% and had low sensitivity (43%) emphasising that other yet-to-be-defined factors were operative.

HIV-1 infection and cognitive impairment in the cART era: a review

With the introduction of combination antiretroviral therapy AIDS dementia complex or HIV-associated dementia, as it was termed later, largely disappeared in clinical practice. However, in the past few years, patients, long-term infected and treated, including those with systemically well controlled infection, started to complain about milder memory problems and slowness, difficulties in concentration, planning, and multitasking. Neuropsychological studies have confirmed that cognitive impairment occurs in a substantial (15-50%) proportion of patients. Among HIV-1-infected patients cognitive impairment was and is one of the most feared complications of HIV-1 infection. In addition, neurocognitive impairment may affect adherence to treatment and ultimately result in increased morbidity for systemic disease. So what may be going on in the CNS after so many years of apparently controlled HIV-1 infection is an urgent and important challenge in the field of HIV medicine. In this review we summarize the key currently available data. We describe the clinical neurological and neuropsychological findings, the preferred diagnostic approach with new imaging techniques and cerebrospinal fluid analysis. We try to integrate data on pathogenesis and finally discuss possible therapeutic interventions.

HIV coreceptor tropism in paired plasma, peripheral blood mononuclear cell, and cerebrospinal fluid isolates from antiretroviral-naïve subjects

A survey of HIV coreceptor usage in cerebrospinal fluid (CSF) samples, peripheral blood mononuclear cells (PBMCs), and plasma samples from naïve seropositive patients was conducted. One hundred patients were enrolled in this study. Of the 100 patients, 36 had a primary or recent infection (P-RI), 31 had an early chronic infection (>350 CD4 cells) (ECI), and 33 had a late chronic infection (LCI). All 3 compartments were sampled in a subset of 33 participants, while the remaining 67 patients provided plasma samples and PBMCs only. Seventy-seven patients harbored the R5 virus in plasma samples and had a significantly higher median and percentage of CD4(+) T cells than patients with X4 virus (437 and 281 cells/μl, respectively; P = 0.0086; 20.6% and 18.6%, respectively). The X4 strain was detected more frequently in patients with LCI than in patients with P-RI or ECI (39.3%, 19.4%, and 9.6%, respectively; P = 0.0063). PBMC and plasma tropism was concordant in 90 patients, and 73 had the R5 strain. Among patients with discordant results, 4 had the R5 virus in their plasma and the X4 virus in PBMCs; 6 showed the opposite profile. Plasma, PBMC, and CSF tropism determinations were concordant in 26/33 patients (21 patients had R5, and 5 had X4). The tropism was discordant in 5/33 patients, with the X4 virus in plasma and R5 in CSF; the HIV tropism in PBMCs was X4 in 3 patients. The remaining 2/33 patients had the R5 virus in plasma and PBMCs and the X4 virus in CSF; one of these patients had a P-RI. The discordant tropism in CSF and blood may have implications for chemokine (C-C motif) receptor 5 (CCR5) antagonist use in patients with limited response to antiretroviral therapy (ART) or in responding patients evaluated for simplification of treatment.

Effects of central nervous system antiretroviral penetration on cognitive functioning in the ALLRT cohort

OBJECTIVE

Differences in antiretroviral distribution into the central nervous system (CNS) may impact neurocognitive status. We assessed the relationship between estimates of antiretroviral therapy penetration into the CNS, using a published ranking system, and neurocognitive status in HIV-positive participants with plasma HIV-1 RNA (vRNA) suppression.

DESIGN

Participants with at least 6 weeks ongoing antiretroviral drug use and vRNA less than 50 copies/ml (N = 2636; 83% male, median baseline CD4 T cells: 244 cells/μl) had at least one neuroscreen assessment [Trail Making Test, Part A and B; Wechsler Adult Intelligence Scale-Revised (WAIS-R) Digit Symbol] at 10 413 neurovisits. Neuroscreen test scores were demographically adjusted and converted to Z-scores (NPZ3: lower scores imply more impairment). Central nervous system penetration effectiveness (CPE) ranks of 0.0 (low), 0.5 (medium), or 1.0 (high) were assigned to antiretrovirals and summed per regimen, per neurovisit.

METHODS

Multivariate linear regression models using generalized estimating equations assessed NPZ3 scores with respect to antiretroviral regimen. Covariates were retained if P ≤ 0.1.

RESULTS

A final model demonstrated that better NPZ3 scores were associated with higher CPE among participants taking more than three antiretroviral drugs (+0.07 per one unit increase in CPE score; P = 0.004) but not among participants with three or less antiretroviral drugs in the regimen (+0.01; P = 0.5). Results were adjusted for demographics, injection drug use, hepatitis C virus serostatus, CD4 cell count (current and nadir), baseline vRNA, antiretroviral experience, and years since first antiretroviral drug use.

CONCLUSION

Use of antiretroviral drugs with better estimated CNS penetration may be associated with better neurocognitive functioning; some people may require more than three antiretroviral drugs to treat HIV in the CNS. Clinically this means antiretroviral regimens could be designed to optimize estimated CNS penetration without sacrificing virologic and immunologic benefits.

Total raltegravir concentrations in cerebrospinal fluid exceed the 50-percent inhibitory concentration for wild-type HIV-1

HIV-associated neurocognitive disorders continue to be common. Antiretrovirals that achieve higher concentrations in cerebrospinal fluid (CSF) are associated with better control of HIV and improved cognition. The objective of this study was to measure total raltegravir (RAL) concentrations in CSF and to compare them with matched concentrations in plasma and in vitro inhibitory concentrations. Eighteen subjects with HIV-1 infection were enrolled based on the use of RAL-containing regimens and the availability of CSF and matched plasma samples. RAL was measured in 21 CSF and plasma pairs by liquid chromatography-tandem mass spectrometry, and HIV RNA was detected by reverse transcription-PCR (RT-PCR). RAL concentrations were compared to the 50% inhibitory concentration (IC(50)) for wild-type HIV-1 (3.2 ng/ml). Volunteers were predominantly middle-aged white men with AIDS and without hepatitis C virus (HCV) coinfection. The median concurrent CD4(+) cell count was 276/μl, and 28% of CD4(+) cell counts were below 200/μl. HIV RNA was detectable in 38% of plasma specimens and 4% of CSF specimens. RAL was present in all CSF specimens, with a median total concentration of 14.5 ng/ml. The median concentration in plasma was 260.9 ng/ml, with a median CSF-to-plasma ratio of 0.058. Concentrations in CSF correlated with those in with plasma (r(2), 0.24; P, 0.02) but not with the postdose sampling time (P, >0.50). RAL concentrations in CSF exceeded the IC(50) for wild-type HIV in all specimens by a median of 4.5-fold. RAL is present in CSF and reaches sufficiently high concentrations to inhibit wild-type HIV in all individuals. As a component of effective antiretroviral regimens or as the main antiretroviral, RAL likely contributes to the control of HIV replication in the nervous system.

HIV-associated neurocognitive disorder: pathogenesis and therapeutic opportunities

Human immunodeficiency virus type 1 (HIV) infection presently affects more that 40 million people worldwide, and is associated with central nervous system (CNS) disruption in at least 30% of infected individuals. The use of highly active antiretroviral therapy has lessened the incidence, but not the prevalence of mild impairment of higher cognitive and cortical functions (HIV-associated neurocognitive disorders) as well as substantially reduced a more severe form dementia (HIV-associated dementia). Furthermore, improving neurological outcomes will require novel, adjunctive therapies that are targeted towards mechanisms of HIV-induced neurodegeneration. Identifying such molecular and pharmacological targets requires an understanding of the events preceding irreversible neuronal damage in the CNS, such as actions of neurotoxins (HIV proteins and cellular factors), disruption of ion channel properties, synaptic damage, and loss of adult neurogenesis. By considering the specific mechanisms and consequences of HIV neuropathogenesis, unified approaches for neuroprotection will likely emerge using a tailored, combined, and non-invasive approach.

Difference in drug resistance patterns between minor HIV-1 populations in cerebrospinal fluid and plasma

OBJECTIVE

The aim of the study was to determine to what extent unique drug resistance patterns appear in minor and major HIV-1 quasispecies in cerebrospinal fluid (CSF) as compared with blood.

METHODS

Forty-four plasma and CSF samples from 13 multi-treatment-experienced patients, seven of whom provided longitudinal samples, were included in the study. The subjects had failed antiretroviral therapy including lamivudine. The reverse transcriptase (RT) gene was examined by selective real-time polymerase chain reaction (SPCR), which can detect M184I/V mutants down to 0.2% of the viral population.

RESULTS

SPCR revealed differences at amino acid position 184 in the plasma/CSF populations in 12 paired samples from eight patients. One plasma sample was positive by SPCR where direct sequencing showed wild-type M184. The other 11 paired samples showed quantitative differences in the mixed populations of the mutant or wild-type M184 quasispecies. Differences in other resistance-associated mutations between plasma and CSF viruses were also found by direct sequencing.

CONCLUSIONS

In multi-treatment-experienced patients with therapy failure, differences in drug resistance patterns were found frequently between plasma and CSF in both minor and major viral populations. To what extent this was a true biological phenomenon remains to be established, and the clinical relevance of these findings is yet to be determined.

Variables that influence HIV-1 cerebrospinal fluid viral load in cryptococcal meningitis: a linear regression analysis

Background

The central nervous system is considered a sanctuary site for HIV-1 replication. Variables associated with HIV cerebrospinal fluid (CSF) viral load in the context of opportunistic CNS infections are poorly understood. Our objective was to evaluate the relation between: (1) CSF HIV-1 viral load and CSF cytological and biochemical characteristics (leukocyte count, protein concentration, cryptococcal antigen titer); (2) CSF HIV-1 viral load and HIV-1 plasma viral load; and (3) CSF leukocyte count and the peripheral blood CD4+ T lymphocyte count.

Methods

Our approach was to use a prospective collection and analysis of pre-treatment, paired CSF and plasma samples from antiretroviral-naive HIV-positive patients with cryptococcal meningitis and assisted at the Francisco J Muñiz Hospital, Buenos Aires, Argentina (period: 2004 to 2006). We measured HIV CSF and plasma levels by polymerase chain reaction using the Cobas Amplicor HIV-1 Monitor Test version 1.5 (Roche). Data were processed with Statistix 7.0 software (linear regression analysis).

Results

Samples from 34 patients were analyzed. CSF leukocyte count showed statistically significant correlation with CSF HIV-1 viral load (r = 0.4, 95% CI = 0.13-0.63, p = 0.01). No correlation was found with the plasma viral load, CSF protein concentration and cryptococcal antigen titer. A positive correlation was found between peripheral blood CD4+ T lymphocyte count and the CSF leukocyte count (r = 0.44, 95% CI = 0.125-0.674, p = 0.0123).

Conclusion

Our study suggests that CSF leukocyte count influences CSF HIV-1 viral load in patients with meningitis caused by Cryptococcus neoformans.

Comparison of HIV type 1 sequences from plasma, cell-free breast milk, and cell-associated breast milk viral populations in treated and untreated women in Mozambique

We analyzed the sequences of the HIV viral populations obtained from plasma, cell-free breast milk, and breast milk cells of HAART-treated (23) and untreated (30) HIV-infected women to obtain information about the origin of the breast milk virus. Sequence analyses of viruses were performed using the TruGene HIV-1 assay. Direct sequences of the reverse transcriptase (RT) and protease (PR) genes were analyzed using the Phylip 3.68 suite of sequence analysis program and pairwise evolutionary distances were calculated with the Kimura two parameter model for estimation of distances. We found that the genetic distances between the plasma and the cell-free breast milk viruses and between the cell-free and cell-associated breast milk viruses for RT were higher in HAART-receiving women than in untreated women, suggesting viral evolution under selective drug pressure in breast milk. Our data support the hypothesis of the presence of an actively replicating viral population in the breast milk compartment, distinct from that present in plasma.

Cross-sectional characterization of HIV-1 env compartmentalization in cerebrospinal fluid over the full disease course

OBJECTIVES

To characterize HIV-1 env compartmentalization between cerebrospinal fluid (CSF) and peripheral blood plasma over all stages of the HIV-1 disease course, and to determine the relationship between the extent of CSF HIV-1 env compartmentalization and clinical neurologic disease status.

DESIGN

Paired blood plasma and CSF specimens were collected from 66 HIV-infected patients cross-sectionally representing all major clinical stages relating to HIV-associated neurologic disease, including primary infection, asymptomatic chronic infection, chronic infection with minor global impairment, and immune deficiency with HIV-associated dementia.

METHODS

Heteroduplex tracking assays and bulk sequence analysis targeting the V1/V2, C2-V3, and V4/V5 regions of env were performed to characterize the genetic makeup of complex HIV-1 populations in the cross-sectional blood plasma and CSF specimens. The levels of blood plasma/CSF env compartmentalization were quantified and compared across the different clinical stages of HIV-1 neurologic disease.

RESULTS

Blood plasma/CSF env compartmentalization levels varied considerably by disease stage and were generally consistent across all three regions of env characterized. Little or no compartmentalization was observed in non-impaired individuals with primary HIV-1 infection. Compartmentalization levels were elevated in chronically infected patients, but were not significantly different between mildly impaired and non-impaired patients. Patients with HIV-associated dementia showed significantly greater blood plasma/CSF env compartmentalization relative to other groups.

CONCLUSION

: Increased CSF compartmentalization of the HIV-1 env gene, which may reflect independent HIV-1 replication and evolution within the central nervous system, is specifically associated with HIV-associated dementia and not the less severe forms of HIV-1 neurologic disease.

Compartmentalized human immunodeficiency virus type 1 originates from long-lived cells in some subjects with HIV-1-associated dementia

Human immunodeficiency virus type 1 (HIV-1) invades the central nervous system (CNS) shortly after systemic infection and can result in the subsequent development of HIV-1–associated dementia (HAD) in a subset of infected individuals. Genetically compartmentalized virus in the CNS is associated with HAD, suggesting autonomous viral replication as a factor in the disease process. We examined the source of compartmentalized HIV-1 in the CNS of subjects with HIV-1–associated neurological disease and in asymptomatic subjects who were initiating antiretroviral therapy. The heteroduplex tracking assay (HTA), targeting the variable regions of env, was used to determine which HIV-1 genetic variants in the cerebrospinal fluid (CSF) were compartmentalized and which variants were shared with the blood plasma. We then measured the viral decay kinetics of individual variants after the initiation of antiretroviral therapy. Compartmentalized HIV-1 variants in the CSF of asymptomatic subjects decayed rapidly after the initiation of antiretroviral therapy, with a mean half-life of 1.57 days. Rapid viral decay was also measured for CSF-compartmentalized variants in four HAD subjects (t_1/2 mean = 2.27 days). However, slow viral decay was measured for CSF-compartmentalized variants from an additional four subjects with neurological disease (t_1/2 range = 9.85 days to no initial decay). The slow decay detected for CSF-compartmentalized variants was not associated with poor CNS drug penetration, drug resistant virus in the CSF, or the presence of X4 virus genotypes. We found that the slow decay measured for CSF-compartmentalized variants in subjects with neurological disease was correlated with low peripheral CD4 cell count and reduced CSF pleocytosis. We propose a model in which infiltrating macrophages replace CD4⁺ T cells as the primary source of productive viral replication in the CNS to maintain high viral loads in the CSF in a substantial subset of subjects with HAD.

Infection of the central nervous system (CNS) with human immunodeficiency virus type 1 (HIV-1) can lead to the development of HIV-1–associated dementia, a severe neurological disease that results in cognitive and motor impairment. Individuals that are chronically infected with HIV-1 sometimes display unique viral variants in their cerebrospinal fluid (CSF) that are not detected in the blood virus population, termed CSF-compartmentalized variants. The cell type that produces CSF-compartmentalized virus throughout the course of infection has not been determined. We used a sensitive assay to detect compartmentalized variants in the CSF of subjects with and without neurological disease, and then measured the decay kinetics of compartmentalized virus when subjects were starting antiretroviral therapy. We found that compartmentalized virus decays rapidly in asymptomatic subjects. Additionally, we detected differential decay (i.e. rapid or slow) in subjects with neurological disease, and this was associated with the number of white blood cells in the CSF. Our data supports a model of HIV-1 infection in the CNS where compartmentalized virus is produced by a long-lived cell type (slow decay), and this virus can be amplified by short-lived cells (rapid decay) that traffic into the CNS, but is increasingly produced from long-lived cells in the immunodeficient state.

Low atazanavir concentrations in cerebrospinal fluid

OBJECTIVE

Protease inhibitors may not penetrate into the central nervous system in therapeutic concentrations, which may allow ongoing HIV replication and injury. The objective of this study was to determine atazanavir penetration into cerebrospinal fluid (CSF).

DESIGN

Single random plasma or paired plasma and CSF samples were drawn from participants enrolled in a multicenter, observational cohort study and taking atazanavir with or without ritonavir between October 2003 and October 2005.

METHODS

Plasma samples were assayed by high performance liquid chromatography and immunoassay; lower limit of detection was 45 ng/ml. CSF samples were assayed by immunoassay (ARK ATV-test); lower limit of detection was 5 ng/ml.

RESULTS

One hundred and seventeen participants (43 +/- 7.7 years, 79% men, 81 +/- 15 kg) had plasma or plasma and CSF paired samples drawn a median (interquartile range) of 10 (5-17) h postdose. Median (interquartile range) plasma atazanavir concentrations with or without ritonavir were 1278 (525-2265) and 523 (283-1344) ng/ml. The median (interquartile range) CSF concentrations with or without ritonavir were 10.3 (<5-21.1) and 7.9 (6.6-22) ng/ml. Nineteen of 79 (24%) CSF samples were less than 5 ng/ml. CSF concentrations were less than 1% of plasma concentrations and near the atazanavir wild-type IC50 of 1-11 ng/ml.

CONCLUSION

Atazanavir CSF concentrations are highly variable and 100-fold lower than plasma concentrations, even with ritonavir boosting. CSF concentrations of atazanavir do not consistently exceed the wild-type IC50 of atazanavir and may not protect against HIV replication in the CSF.

Estimation of virological and immunological parameters in subjects from South India infected with human immunodeficiency virus type 1 clade C and correlation of findings with occurrence of neurological disease

Several studies carried out in Western countries have demonstrated that a number of virological and immunological markers such as viral loads, cytokines, beta(2)-microglobulin, neopterin, etc., are elevated in the serum and cerebrospinal fluid (CSF) of human immunodeficiency virus (HIV)-infected individuals with neurological disease. The neurological manifestations of HIV infection noted in Indian patients is different from those reported in Western countries. Moreover, few studies have investigated the role of virological and immunological parameters with respect to the progression of HIV-1 clade C infection in India. In this study, we measured virological (HIV-1 RNA levels) and immunological parameters (CD4 cell count and inflammatory markers) in the plasma and CSF of HIV-1-infected neurologically asymptomatic and symptomatic (with opportunistic infections and/or dementia) subjects. By using clade-specific polymerase chain reaction (PCR), we ascertained that all samples used for the study were infected with HIV-1 clade C. Among the various laboratory parameters evaluated, high viral loads in the CSF, low CD4 counts, and higher levels of interleukin (IL)-1alpha, IL-6, tumor necrosis factor alpha (TNFalpha), beta(2)-microglobulin, and neopterin were noted in HIV-infected subjects with neurological disease as compared to asymptomatic subjects. These data suggest that the markers evaluated in plasma and CSF samples correlated with occurrence of neurological disease in symptomatic individuals as compared to asymptomatic HIV infected subjects.

Cognitive functioning during highly active antiretroviral therapy interruption in human immunodeficiency virus type 1 infection

Although no longer considered therapeutically beneficial, antiretroviral treatment interruptions (TIs) still occur frequently among patients with human immunodeficiency virus (HIV) infection for a variety of reasons. TIs typically result in viral rebound and worsening immunosuppression, which in turn are risk factors for neurocognitive decline and dementia. We sought to determine the extent of neurocognitive risk with TIs and subsequent reintroduction of highly active antiretroviral therapy (HAART) by using a comprehensive, sensitive neuropsychological assessment and by concurrently determining changes in plasma and cerebrospinal fluid (CSF) viral load and CD4 counts. Prospective, serial, clinical evaluations including neuropsychological (NP) testing and measurement of plasma HIV RNA and CD4 count and mood state were performed on HIV-1-infected individuals (N=11) at three time points: (1) prior to a TI, while on HAART; (2) after TIs averaging 6 months; and (3) after reinitiating HAART therapy. During TI, plasma HIV RNA increased and CD4 counts declined significantly, but NP performance did not change. Following reinitiation of HAART, viral loads fell below pre-TI levels, and CD4 counts rose. Improved viral suppression and immune restoration with reinitiation of HAART resulted in significant improvement in neurocognitive performance. No changes on comprehensive questionnaires of mood state were observed in relation to TI.NP performance and mood state remained stable during TIs despite worsened viral loads and CD4 counts. Because "practice effects" are generally greatest between the first and second NP testing sessions, improvement at the third, post-TI time point was unlikely to be accounted for by practice. TIs of up to 6 months appear to be neurocognitively and psychiatrically safe for most patients.

Preventing brain damage in HIV infection

HIV-1 is a virus with neurotropic features causing major morbidity and also mortality if untreated. Mild symptoms of neurocognitive impairment are common and precede more severe forms of dementia, termed AIDS dementia complex (ADC). The pathogenesis of neurodegeneration in HIV-1 infection is not fully understood, and we lack specific markers to verify the diagnosis. Fortunately, antiretroviral treatment is effective in treating both systemic and CNS infection, and neurocognitive symptoms and ADC will, in most cases, improve on treatment. This review focuses on current research regarding cerebral spinal fluid biomarkers and effects of highly active antiretroviral treatment on HIV-1 CNS disease.

Chronic alcohol consumption generates a vulnerable immune environment during early SIV infection in rhesus macaques

BACKGROUND

Alcohol consumption is a common problem in HIV-infected individuals, and the effects of alcohol may alter the efficiency of the immune response, potentially aggravating the disease as well as affecting end organs, such as the brain. However, the elements of the virus-host interaction that are modulated by ethanol are poorly dissected.

METHODS

Ethanol intake was conditioned in rhesus macaques prior to SIV infection, in order to mimic this common human behavior, and allow the evaluation of aspects of the virus-immune system interactions during acute time-points, when important facets of the infection are set up and when virus reproducibly enters the brain.

RESULTS

Although ethanol had a limited effect on the acute plasma viral load, it resulted in reduced circulating memory CD4(+) T cells and increased levels of monocytes expressing the viral coreceptor CCR5. In organs, ethanol consumption impacted immune cells in the liver as well as lymphoid and other nonlymphoid tissues, where CD4(+) T cells were predominantly affected.

CONCLUSION

Overall, the consumption of alcohol causes immune cell alterations that can contribute to the generation of a disease susceptible environment upon SIV infection.

Antiretroviral therapy and central nervous system HIV type 1 infection

Central nervous system (CNS) human immunodeficiency virus type 1 (HIV-1) infection begins during primary viremia and continues throughout the course of untreated systemic infection. Although frequently accompanied by local inflammatory reactions detectable in cerebrospinal fluid (CSF), CNS HIV-1 infection usually is not clinically apparent. In a minority of patients, CNS HIV-1 infection evolves into encephalitis during the late stages of systemic infection, which compromises brain function and presents clinically as acquired immunodeficiency syndrome dementia complex (ADC). Combination antiretroviral therapy (ART) has had a major impact on all aspects of CNS HIV-1 infection and disease. In those with asymptomatic infection, ART usually effectively suppresses HIV-1 in CSF and markedly reduces the incidence of symptomatic ADC. In those presenting with ADC, ART characteristically prevents neurological progression and leads to variable, and at times substantial, recovery. Similarly, treatment has reduced CNS opportunistic infections. With better control of these severe disorders, attention has turned to the possible consequences of chronic silent infection and the issue of whether indolent, low-grade brain injury might require earlier treatment intervention.

Antiretroviral treatment effect on immune activation reduces cerebrospinal fluid HIV-1 infection

OBJECTIVE

To define the effect of antiretroviral therapy (ART) on activation of T cells in cerebrospinal fluid (CSF) and blood, and interactions of this activation with CSF HIV-1 RNA concentrations.

DESIGN

Cross-sectional analysis of 14 HIV-negative subjects and 123 neuroasymptomatic HIV-1-infected subjects divided into 3 groups: not on ART (termed "offs"), on ART with plasma HIV-1 RNA >500 copies/mL ("failures"), and on ART with plasma HIV-1 RNA <or=500 copies/mL ("successes"). T-cell activation was measured by coexpression of CD38 and human leukocyte antigen DR (HLA-DR). Other measurements included CSF neopterin and white blood cell (WBC) counts.

RESULTS

CD8 T-cell activation in CSF and blood was highly correlated across all subjects and was highest in the offs, lower in the failures, and lower still in the successes. While CD8 activation was reduced in failures compared to offs across the range of plasma HIV-1, it maintained a coincident relation to CSF HIV-1 in both viremic groups. In addition to correlation with CSF HIV-1 concentrations, CD8 activation in blood and CSF correlated with CSF WBCs and CSF neopterin. Multivariate analysis confirmed the association of blood CD8 T-cell activation, along with plasma HIV-1 RNA and CSF neopterin, with CSF HIV-1 RNA levels.

CONCLUSIONS

The similarity of CD8 T-cell activation in blood and CSF suggests these cells move from blood to CSF with only minor changes in CD38/HLA-DR expression. Differences in the relation of CD8 activation to HIV-1 concentrations in the blood and CSF in the 2 viremic groups suggest that changes in immune activation not only modulate CSF HIV-1 replication but also contribute to CSF treatment effects. The magnitude of systemic HIV-1 infection and intrathecal macrophage activation are also important determinants of CSF HIV-1 RNA levels.

NeuroAIDS: characteristics and diagnosis of the neurological complications of AIDS

The neurological complications of AIDS (NeuroAIDS) include neurocognitive impairment and HIV-associated dementia (HAD; also known as AIDS dementia and HIV encephalopathy). HAD is the most significant and devastating central nervous system (CNS) complications associated with HIV infection. Despite recent advances in our knowledge of the clinical features, pathogenesis, and neurobiological aspects of HAD, it remains a formidable scientific and therapeutic challenge. An understanding of the mechanisms of HIV neuroinvasion, CNS proliferation, and HAD pathogenesis provide a basis for the interpretation of the diagnostic features of HAD and its milder form, HIV-associated minor cognitive/motor disorder (MCMD). Current diagnostic strategies are associated with significant limitations, but it is hoped that the use of biomarkers may assist researchers and clinicians in predicting the onset of the disease process and in evaluating the effects of new therapies.

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.

Biomarkers of HIV related central nervous system disease

In this review we critically assess biomarkers of the direct effects of HIV related brain disease. This area is becoming increasingly complex because of the presence of confounds and varying degrees of activity of HIV brain disease. Sensitive and specific biomarkers are urgently needed although existing biomarkers do have some utility. The review will focus on the practical implications of the more established biomarkers. We discuss blood, cerebrospinal fluid and neurophysiological biomarkers but not neuroimaging techniques as they are beyond the scope of this review.

The prevalence and incidence of neurocognitive impairment in the HAART era

OBJECTIVES

HAART suppresses HIV viral replication and restores immune function. The effects of HAART on neurological disease are less well understood. The aim of this study was to assess the prevalence and incidence of neurocognitive impairment in individuals who initiated HAART as part of an AIDS clinical trial.

DESIGN

A prospective cohort study of HIV-positive patients enrolled in randomized antiretroviral trials, the AIDS Clinical Trials Group (ACTG) Longitudinal Linked Randomized Trials (ALLRT) study.

METHODS

We examined the association between baseline and demographic characteristics and neurocognitive impairment among 1160 subjects enrolled in the ALLRT study.

RESULTS

A history of immunosuppression (nadir CD4 cell count < 200 cells/microl) was associated with an increase in prevalent neurocognitive impairment. There were no significant virological and immunological predictors of incident neurocognitive impairment. Current immune status (low CD4 cell count) was associated with sustained prevalent impairment.

CONCLUSION

The association of previous advanced immunosuppression with prevalent and sustained impairment suggests that there is a non-reversible component of neural injury that tracks with a history of disease progression. The association of sustained impairment with worse current immune status (low CD4 cell count) suggests that restoring immunocompetence increases the likelihood of neurocognitive recovery. Finally, the lack of association between incident neurocognitive impairment and virological and immunological indicators implies that neural injury continues in some patients regardless of the success of antiretroviral therapy on these laboratory measures.

HIV-1 RNA concentration and cognitive performance in a cohort of HIV-positive people

OBJECTIVE

To determine whether higher viral concentrations in the cerebrospinal fluid (CSF) and/or peripheral blood were associated with greater severity of cognitive impairment in HIV-1-seropositive subjects with cognitive-motor impairment.

METHODS

Cognitive performance measurements and viral load were obtained from HIV-1-seropositive individuals with cognitive-motor impairment entering a clinical trial before the introduction of highly active antiretroviral therapy (HAART). CSF viral load (UltraSensitive Roche HIV-1 Monitor test with detection limit of 50 copies/ml) was available from 179 patients, and peripheral (plasma or serum) viral load from 111 patients. Of these patients, 62% met the 1993 Centers for Disease Control (CDC) criteria for AIDS, and 19% had clinically significant cognitive impairment (i.e., global deficit score > or = 0.5). Possible associations between viral load and cognitive scores were examined with general linear regression models with and without adjustment for age, education, study site, antiretroviral use, CD4 cell count, and CDC stage.

RESULTS

The mean CSF viral load was 2.83 log(10)/ml +/- 0.94 (SD) (undetectable in 19.5%). Mean peripheral viral load was 4.11 log(10)/ml +/- 0.90 (SD). No statistically significant associations emerged between either CSF or peripheral viral load and the global deficit score, or any of the seven cognitive domain deficit scores.

CONCLUSIONS

Among these HIV-1-sero-positive individuals with mainly minor HIV-1-associated cognitive deficits and not receiving HAART, no association between CSF or blood concentration of HIV-1 RNA and cognitive performance could be found. These results suggest that the severity of HIV-1-associated cognitive impairment is not directly related to concurrent viral concentration in the CSF or the peripheral blood.

Neurologic and neurodevelopmental manifestations of pediatric HIV/AIDS: a global perspective

Neurodevelopmental abnormalities associated with HIV infection have been described since the first reports of pediatric AIDS in the 1980s. Before antiretroviral therapy (ART) became widely available, progressive HIV-1 encephalopathy (PHE) was reported in the US in 13-35% of children with HIV-1 infection and in 35-50% of children with AIDS. Introduction of ART can prevent PHE and reverse PHE present at ART initiation, but a high prevalence of residual problems has been described. Even though 90% of HIV-infected children live in the developing world, few children have access to ART and little is known regarding the neurological manifestations of perinatal HIV infection in those regions. Mechanisms of pediatric HIV-1 neuropathogenesis and factors associated with neurodevelopmental abnormalities in perinatally infected children are not yet fully understood. Studies have demonstrated that HIV-1 enters the CNS soon after infection and may persist in this compartment over the entire course of HIV-1 infection. The CNS is a distinct viral reservoir, differing from peripheral compartments in target cells and antiretroviral penetration. Neurotropic HIV-1 likely develops distinct genotypic characteristics in response to this unique environment. We reviewed the literature on pediatric neuroAIDS and identified gaps in the current knowledge.

Feline immunodeficiency virus neuropathogenesis: from cats to calcium

Invasion of human immunodeficiency virus (HIV) into the central and peripheral nervous system produces a wide range of neurological symptoms, which continue to persist even with adequate therapeutic suppression of the systemic viremia. The development of therapies designed to prevent the neurological complications of HIV require a detailed understanding of the mechanisms of virus penetration into the nervous system, infection, and subsequent neuropathogenesis. These processes, however, are difficult to study in humans. The identification of animal lentiviruses similar to HIV has provided useful models of HIV infection that have greatly facilitated these efforts. This review summarizes contributions made from in vitro and in vivo studies on the infectious and pathological interactions of feline immunodeficiency virus (FIV) with the nervous system. In vivo studies on FIV have provided insights into the natural progression of CNS disease as well as the contribution of various risk factors. In vitro studies have contributed to our understanding of immune cell trafficking, CNS infection and neuropathogenesis. Together, these studies have made unique contributions to our understanding of (1) lentiviral interactions at the blood-cerebrospinal fluid (CSF) barrier within the choroid plexus, (2) early FIV invasion and pathogenesis in the brain, and (3) lentiviral effects on intracellular calcium deregulation and neuronal dysfunction. The ability to combine in vitro and in vivo studies on FIV offers enormous potential to explore neuropathogenic mechanisms and generate information necessary for the development of effective therapeutic interventions.

HIV pharmacology: barriers to the eradication of HIV from the CNS

Total eradication of HIV-1 is not yet achievable, in part because reservoirs of latent HIV-1 can develop within lymphoid tissue, the testes, and the central nervous system (CNS). The presence of HIV-1 in the CNS is clinically significant because of its association with the development of HIV dementia, which occurs in up to one fifth of untreated patients. This review summarizes current theory regarding HIV-1 infection within the CNS, describes physiologic and pharmacologic factors limiting CNS penetration of antiretroviral drugs used to treat HIV-1 infection, and reviews current treatment of CNS HIV-1 infection and HIV encephalopathy.

Management of advanced HIV disease: resistance, antiretroviral brain penetration and malignancies

Data from Italy, Spain and the USA all highlight the worrying fact that presentation with advanced HIV disease - defined as a cluster of differentiation 4 (CD4) count <50 cells/mm(3) or the presence of an acquired immunodeficiency syndrome-defining illness - is increasingly common. A review from 2003 showed that 31% of patients in the UK and Ireland presented late (<200 CD4 cells/mm(3)). Early diagnosis is vital to ensure that patients benefit from antiretroviral therapy, and when patients present late, they do not obtain the benefits of early treatment. The risk of death is lower when antiretroviral therapy is initiated at CD4 counts of 201-350 cells/mm(3) than at lower CD4 cell counts. In addition, the risk of unintentional infection of others is increased, which is particularly troubling in light of evidence that transmission of resistance can occur even in the absence of antiretroviral therapy. The management of patients with advanced disease and no complications is complex, but issues of transmitted resistance and comorbid conditions further confuse management decisions in the treatment of patients with higher CD4 counts. This article reviews recent evidence on transmitted resistance, the pharmacokinetics of antiretroviral drugs in patients with central nervous system disease and the management issues in patients with comorbid malignancies to offer practical advice on therapeutic options for treatment-naïve patients who present with advanced HIV disease.

Relationship of antiretroviral treatment to postmortem brain tissue viral load in human immunodeficiency virus-infected patients

Human immunodeficiency virus (HIV)-1 invades the central nervous system (CNS) soon after infection and is partially protected there from host immunity and antiretroviral drugs (ARVs). Sanctuary from highly active antiretroviral therapy (HAART) in the CNS could result in ongoing viral replication, promoting the development of drug resistance and neurological disease. Despite the importance of these risks, no previous study has directly assessed HAART's effects on brain tissue viral load (VL). The authors evaluated 61 HIV-infected individuals for whom both histories of HAART treatment and postmortem brain tissue VL measurements were available. Two groups were defined based on HAART use in the 3 months prior to death: HAART(+) subjects had received HAART, and HAART(-) subjects had not received HAART. HIV RNA was quantified in postmortem brain tissue (log10 copies/10 microg total tissue RNA) and antemortem plasma (log10 copies/ml) by reverse transcriptase-polymerase chain reaction (RT-PCR). Brain tissue VLs were significantly lower among HAART(+) subjects compared to HAART(-) subjects (median 2.6 versus 4.1; P= .0007). These findings suggest that despite the limited CNS penetration of many antiretroviral medications, HAART is at least partially effective in suppressing CNS viral replication. Because some HAART regimens may be better than others in this regard, regimen selection strategies could be used to impede CNS viral activity, limit neuronal dysfunction, and prevent or treat clinical neurocognitive disorders in HIV-infected patients. Furthermore, such strategies might help to prevent the development of ARV resistance.

HIV-TAT protein upregulates expression of multidrug resistance protein 1 in the blood-brain barrier

Central nervous system (CNS) complications of human immunodeficiency virus (HIV) infection remain a serious health risk in HIV/acquired immunodeficiency syndrome despite significant advances in highly active antiretroviral therapy (HAART). Specific drugs used for HAART are substrates for the efflux transport systems, such as the multidrug resistance-associated proteins (MRPs), which are present on brain microvascular endothelial cells (BMEC) and astrocytes, that is, the main cell types that form the blood-brain barrier (BBB). Thus, drugs employed in HAART are actively removed from the CNS and do not efficiently inhibit HIV replication in the brain. To study the potential mechanisms of this process, the aim of the present research was to address the hypothesis that HIV Tat protein can contribute to upregulation of MRP expression at the BBB level. Tat is a protein produced and released by HIV-infected cells, which may play an important role in brain vascular pathology in the course of HIV infection. Among the family of MRPs, exposure to Tat specifically induced MRP1 messenger ribonucleic acid and protein expression both in BMEC and astrocytes. These alterations were accompanied by enhanced MRP1-mediated efflux functions. Furthermore, activation of the mitogen-activated protein kinase signaling cascade was identified as the mechanism involved in Tat-mediated overexpression of MRP1. These results indicate that Tat exposure can lead to alterations of the BBB functions and decrease HAART efficacy in the CNS through overexpression of drug efflux transporters.

Genetic attributes of cerebrospinal fluid-derived HIV-1 env

HIV-1 often invades the CNS during primary infection, eventually resulting in neurological disorders in up to 50% of untreated patients. The CNS is a distinct viral reservoir, differing from peripheral tissues in immunological surveillance, target cell characteristics and antiretroviral penetration. Neurotropic HIV-1 likely develops distinct genotypic characteristics in response to this unique selective environment. We sought to catalogue the genetic features of CNS-derived HIV-1 by analysing 456 clonal RNA sequences of the C2-V3 env subregion generated from CSF and plasma of 18 chronically infected individuals. Neuropsychological performance of all subjects was evaluated and summarized as a global deficit score. A battery of phylogenetic, statistical and machine learning tools was applied to these data to identify genetic features associated with HIV-1 neurotropism and neurovirulence. Eleven of 18 individuals exhibited significant viral compartmentalization between blood and CSF (P < 0.01, Slatkin-Maddison test). A CSF-specific genetic signature was identified, comprising positions 9, 13 and 19 of the V3 loop. The residue at position 5 of the V3 loop was highly correlated with neurocognitive deficit (P < 0.0025, Fisher's exact test). Antibody-mediated HIV-1 neutralizing activity was significantly reduced in CSF with respect to autologous blood plasma (P < 0.042, Student's t-test). Accordingly, CSF-derived sequences exhibited constrained diversity and contained fewer glycosylated and positively selected sites. Our results suggest that there are several genetic features that distinguish CSF- and plasma-derived HIV-1 populations, probably reflecting altered cellular entry requirements and decreased immune pressure in the CNS. Furthermore, neurological impairment may be influenced by mutations within the viral V3 loop sequence.

Neuroactive antiretroviral drugs do not influence neurocognitive performance in less advanced HIV-infected patients responding to highly active antiretroviral therapy

OBJECTIVE

To analyze the effect of antiretroviral therapy, including drugs that have good penetration in cerebrospinal fluid (CSF), on neuropsychologic performance.

METHODS

One hundred sixty-five HIV-1-infected patients exposed to a stable highly active antiretroviral therapy (HAART) regimen were studied. Neuropsychologic examinations were performed for all patients.

RESULTS

A total of 50.3% of patients were impaired. In multivariate analysis, older age (for 10-year increase, odds ratio [OR] = 4.8, 95% confidence interval [CI]: 2.2 to 10.4; P< 0.0001) and higher plasma HIV-1 RNA levels (OR = 1.90, 95% CI: 1.1 to 3.2; P = 0.021) at testing were independently associated with an increased probability of impaired neurocognitive performance, whereas higher educational level was a protective factor (OR = 0.76, 95% CI: 0.65 to 0.90; P=0.001). A significant linear correlation was observed between the neuropsychologic z score for 8 tests (NPZ8) score, a quantitative parameter of neurocognitive impairment, and CD4 cell count at neuropsychologic testing (R = 0.273, P = 0.001) and between the NPZ8 score and the patient's age (R = 0.288, P = 0.001).

CONCLUSIONS

Our study indicates that the use of stable HAART, including multiple drugs that have good CSF penetration, was not associated with neuropsychologic performance. To prevent independent replication of HIV in CSF with better control of a relevant reservoir of HIV is one of the crucial aims of therapeutic strategy.

HIV-1 persistence, viral reservoir, and the central nervous system in the HAART era

HAART therapy has led to a significant reduction of general and neurological morbidity, and mortality among HIV-1 infected patients. It can also decrease HIV-1 RNA titres in plasma and CSF towards undetectable level. However, the initial hope of achieving total eradication of the virus from the body has vanished. Even in patients who do not develop viral resistance or treatment intolerance, two kinds of viral persistence have been demonstrated both in lymphoid and central nervous system. The first one is a smoldering infection that persists, despite prolonged and apparently efficient HAART, in monocytes, tissue macrophages and most probably microglia. The second one is an integration of proviral DNA in the genome of subpopulations of CD4 lymphocytes of patients receiving efficient HAART. A similar viral integration in astrocytes and less likely in resting microglia is suggested by several studies, although it has yet to be demonstrated conclusively.

HIV-1 RNA levels in cerebrospinal fluid and plasma and their correlation with opportunistic neurological diseases in a Brazilian AIDS reference hospital

BACKGROUND: Plasma HIV RNA levels reflect systemic viral replication but in CNS it may occur relatively independent of systemic infection, yet clinical application of CSF HIV-1 RNA levels is less clear. OBJECTIVE: to compare CSF and plasma HIV-1 RNA levels of patients with different opportunistic neurological diseases to those without neurological disease, as well as to correlate these levels with the outcome of the disease and use of HAART. METHOD: 97 patients who had lumbar puncture for routine work up of suspected neurological diseases, were divided in 2 groups: without neurological disease (23) and with neurological disease (74). NASBA was used for plasma and CSF HIV RNA. RESULTS: Median CSF viral load was higher in toxoplasmic encephalitis, cryptococcal meningitis, HIV dementia and neurological diseases without a defined etiology when compared to patients without neurological disease. There was no difference between plasma viral load in patients with and without neurological diseases. Median viral load was higher in plasma and CSF among patients who died when compared to those successfully treated. CSF and plasma viral load were lower in patients with opportunistic diseases on HAART than without HAART. CONCLUSION: CSF viral load was higher in patients with any neurological disease, but this difference was not present in plasma viral load, suggesting that neurological disease influences more the CSF than plasma compartments. Notwithstanding different neurological diseases were not possible to be diferentiated by the levels of CSF HIV-1.

Cerebrospinal fluid HIV infection and pleocytosis: relation to systemic infection and antiretroviral treatment

BACKGROUND

Central nervous system (CNS) exposure to HIV is a universal facet of systemic infection. Because of its proximity to and shared barriers with the brain, cerebrospinal fluid (CSF) provides a useful window into and model of human CNS HIV infection.

METHODS

Prospective study of the relationships of CSF to plasma HIV RNA, and the effects of: 1) progression of systemic infection, 2) CSF white blood cell (WBC) count, 3) antiretroviral therapy (ART), and 4) neurological performance. One hundred HIV-infected subjects were cross-sectionally studied, and 28 were followed longitudinally after initiating or changing ART.

RESULTS

In cross-sectional analysis, HIV RNA levels were lower in CSF than plasma (median difference 1.30 log10 copies/mL). CSF HIV viral loads (VLs) correlated strongly with plasma VLs and CSF WBC counts. Higher CSF WBC counts associated with smaller differences between plasma and CSF HIV VL. CSF VL did not correlate with blood CD4 count, but CD4 counts <50 cells/microL associated with a low prevalence of CSF pleocytosis and large differences between plasma and CSF VL. CSF HIV RNA correlated neither with the severity of the AIDS dementia complex (ADC) nor abnormal quantitative neurological performance, although these measures were associated with depression of CD4 counts. In subjects starting ART, those with lower CD4 counts had slower initial viral decay in CSF than in plasma. In all subjects, including five with persistent plasma viremia and four with new-onset ADC, CSF HIV eventually approached or reached the limit of viral detection and CSF pleocytosis resolved.

CONCLUSION

CSF HIV infection is common across the spectrum of infection and is directly related to CSF pleocytosis, though whether the latter is a response to or a contributing cause of CSF infection remains uncertain. Slowing in the rate of CSF response to ART compared to plasma as CD4 counts decline indicates a changing character of CSF infection with systemic immunological progression. Longer-term responses indicate that CSF infection generally responds well to ART, even in the face of systemic virological failure due to drug resistance. We present simple models to explain the differing relationships of CSF to plasma HIV in these settings.

The central nervous system is a viral reservoir in simian immunodeficiency virus--infected macaques on combined antiretroviral therapy: a model for human immunodeficiency virus patients on highly active antiretroviral therapy

This study used a simian immunodeficiency virus (SIV)-macaque model to determine whether virus persists in the central nervous system (CNS) of human immunodeficiency virus (HIV)-infected individuals in which plasma viral load has been suppressed by highly active antiretroviral therapy. SIV-infected macaques were treated with two reverse transcriptase inhibitors: PMPA (q- R-(2-phosphonomethoxypropyl)adenine)which does not cross the blood-brain barrier, and FTC (beta-2('),3(')-dideoxy-3 thia-5-fluorocytidine), which does. Viral DNA and RNA were quantitated in the brain after 6 months of suppression of virus replication in blood and cerebrospinal fluid (CSF). Viral DNA was detected in brain from all macaques, including those in which peripheral viral replication had been suppressed either by antiretroviral therapy or host immune responses. Significant neurological lesions were observed only in one untreated macaque that had active virus replication in the CNS. Expression of the inflammatory markers, major histocmopatibility complex (MHC) II and CD68 was significantly lower in macaques treated with PMPA/FTC. Thus, although antiretroviral treatment may suppress virus replication in the periphery and the brain and reduce CNS inflammation, viral DNA persists in the brain despite treatment. This suggests that the brain may serve as a long-term viral reservoir in HIV-infected individuals treated with antiretroviral drugs that suppress virus replication.

Neurological complications of HIV infection

Cognitive disorders, vacuolar myelopathy, and sensory neuropathies associated with HIV are the most common disorders in patients with HIV AIDS, and are the focus of this review. These disorders are treatable and of those associated with HIV AIDS the pathogenic mechanisms are the most understood. Although triggered by productive HIV macrophage infections, aberrant immune activation plays a major role in inducing the CNS disorders. Novel therapies aimed at these inflammatory mechanisms can be effective. The sensory neuropathies associated with HIV infection are a major cause of morbidity; incidence may be increased by the toxic effects of specific antiretroviral drugs within the peripheral nervous system.

Increased human immunodeficiency virus type 1 (HIV-1) env compartmentalization in the presence of HIV-1-associated dementia

The human immunodeficiency virus type 1 (HIV-1) surface Env protein has been implicated in the development of HIV-1-associated dementia (HAD). HIV-1 env diversity was analyzed by heteroduplex tracking assay in 27 infected subjects with various neurological statuses. env compartmentalization between the blood and cerebral spinal fluid (CSF) was apparent with all neurological categories. However, in subjects with HAD, significantly more CSF virus was represented by CNS-unique env variants. Variants specialized for replication in the CNS may play a larger role in the development of HAD. Alternatively, HAD may be associated with a more pronounced state of immunosuppression that permits more extensive replication and independent evolution within the CNS compartment.

Compartmentalized human immunodeficiency virus type 1 present in cerebrospinal fluid is produced by short-lived cells

Human immunodeficiency virus type 1 (HIV-1) invades the central nervous system (CNS) during primary infection and persists in this compartment by unknown mechanisms over the course of infection. In this study, we examined viral population dynamics in four asymptomatic subjects commencing antiretroviral therapy to characterize cellular sources of HIV-1 in the CNS. The inability to monitor viruses directly in the brain poses a major challenge in studying HIV-1 dynamics in the CNS. Studies of HIV-1 in cerebrospinal fluid (CSF) provide a useful surrogate for the sampling of virus in the CNS, but they are complicated by the fact that infected cells in local CNS tissues and in the periphery contribute to the population pool of HIV-1 in CSF. We utilized heteroduplex tracking assays to differentiate CSF HIV-1 variants that were shared with peripheral blood plasma from those that were compartmentalized in CSF and therefore presumably derived from local CNS tissues. We then tracked the relative decline of individual viral variants during the initial days of antiretroviral therapy. We found that HIV-1 variants compartmentalized in CSF declined rapidly during therapy, with maximum half-lives of approximately 1 to 3 days. These kinetics emulate the decline in HIV-1 produced from short-lived CD4+ T cells in the periphery, suggesting that a similarly short-lived, HIV-infected cell population exists within the CNS. We propose that short-lived CD4+ T cells trafficking between the CNS and the periphery play an important role in amplifying and maintaining HIV-1 populations in the CNS during the asymptomatic phase of infection.