Cerebrospinal-fluid HIV-1 RNA and drug concentrations after treatment with lamivudine plus zidovudine or stavudine

Pharmacology of HIV Cure: Site of Action

Despite significant advances in HIV treatment over the past 30 years, critical barriers to an HIV cure persist. The HIV reservoir, defined at both the cellular and anatomical level, constitutes the main barrier to cure. While the mechanisms underlying the reservoir are not yet well understood, one theory to explain persistence at the anatomical level is that subtherapeutic exposure to antiretroviral therapy (ART) within certain tissue compartments permits ongoing replication. Characterizing ART pharmacology throughout the body is important in the context of these potential pharmacologic sanctuaries and for maximizing the probability of success with forthcoming cure strategies that rely on latency reversal and require ART to prevent reseeding the reservoir. In this review, we provide a comprehensive overview of ART and latency reversal agent distribution at the site of action for HIV cure (i.e., anatomical sites commonly associated with HIV persistence, such as lymphoid organs and the central nervous system). We also discuss methodologic approaches that provide insight into HIV cure pharmacology, including experimental design and advances within the computational, pharmaceutical, and analytical chemistry fields. The information discussed in this review will assist in streamlining the development of investigational cure strategies by providing a roadmap to ensure therapeutic exposure within the site of action for HIV cure.

Drug Resistance Mutation Frequency of Single-Genome Amplification-Derived HIV-1 Polymerase Genomes in the Cerebrospinal Fluid and Plasma of HIV-1-Infected Individuals under Nonsuppressive Therapy

HIV-1 evolution in the cerebrospinal fluid (CSF) and plasma may result in discordant drug resistance mutations (DRMs) in the compartments. Single-genome amplification (SGA) was used to generate partial HIV-1 polymerase genomes in paired CSF and plasma samples from 12 HIV-1-positive participants in the CNS HIV Antiretroviral Therapy Effects Research (CHARTER) study who were classified as neurocognitively unimpaired or with various degrees of HIV-associated neurocognitive disorders (HAND). Subjects were viremic on combination antiretroviral therapy (cART). HIV-1 DRMs and phylogenetic characteristics were determined using the Stanford HIVdb program and phylogenetic analyses. Individual DRMs were identified more frequently in plasma than in paired CSF (P = 0.0078). Significant differences in the ratios of DRMs in CSF and plasma were found in 3 individuals with HAND (3/7 = 43%). Two HAND subjects (2/7 = 29%) demonstrated one DRM in CSF not identified in paired plasma. Longitudinal analyses (n = 4) revealed significant temporal differences in the ratios of DRMs in the compartments. Statistically significant differences in the frequency of DRMs in the CSF and plasma are readily found in those on nonsuppressive cART. While compartment-based DRM discordance was largely consistent with increased drug-selective pressures in the plasma, overrepresentation of DRMs in the central nervous system (CNS) can occur. Underlying mechanisms of HAND are complex and multifactorial. The clinical impact of DRM discordance on viral persistence and HAND pathogenesis remains unclear and warrants further investigation in larger, longitudinal cohorts.IMPORTANCE Several antiretroviral agents do not efficiently enter the CNS, and independent evolution of HIV-1 viral variants in the CNS and plasma can occur. We used single-genome amplification (SGA) in cross-sectional and longitudinal analyses to uniquely define both the identity and relative proportions of drug resistance mutations (DRMs) on individual HIV-1 polymerase genomes in the cerebrospinal fluid (CSF) and plasma in individuals with incomplete viral suppression and known neurocognitive status. Statistically significant differences in the ratio of DRMs in the CSF and plasma were readily found in those on nonsuppressive cART, and overrepresentation of DRMs in the CNS can occur. Although questions about the clinical significance of DRM discordance remain, in the quest for viral eradication, it is important to recognize that a significant, dynamic, compartment-based DRM ratio imbalance can exist, as it has the potential to go unnoticed in the setting of standard clinical drug resistance testing.

Zidovudine and Lamivudine as Potential Agents to Combat HIV-Associated Neurocognitive Disorder

The central nervous system has been identified as an anatomical reservoir for HIV due the difficulties in delivering therapeutic agents into the brain and this complication results in HIV-associated neurocognitive disorder that persists in infected patients. The brain regions that are potentially exposed to tissue deficits due to HIV have been reported in previous reports; therefore, it is important to determine the drugs that can enter and localize in brain regions that are known to be susceptible to HIV neurodegeneration. Sprague-Dawley rats received intraperitoneal doses of zidovudine and lamivudine (50 mg kg^-1). Mass spectrometry methods were used to determine the pharmacokinetics, of zidovudine and lamivudine, in the brain using liquid chromatography tandem mass spectrometry and mass spectrometry imaging (MSI), respectively. Zidovudine and lamivudine displayed complementary pharmacokinetic curves indicating a rapid absorption and blood-brain barrier penetration of both drugs reaching C_max at 0.5 h after single dose. MSI of coronal brain sections showed that zidovudine and lamivudine are mostly distributed in corpus callosum, globus pallidus, striatum, and the neocortex region. Mass spectrometry techniques were used to demonstrate that zidovudine and lamivudine drugs are able to reach and localize in brain regions that are targets of HIV neurodegeneration in the brain.

Mass spectrometric investigations into the brain delivery of abacavir, stavudine and didanosine in a rodent model

HIV replication in the brain is unopposed due to reduced antiretroviral drug penetration into the central nervous system (CNS). Prevalence of HIV-associated neurocognitive disorder (HAND) has increased severely in patients living with HIV despite current treatments. The aims of this study were to evaluate the brain bio-distribution of alternative nucleoside reverse transcriptase inhibitors, abacavir, stavudine and didanosine in the CNS and to determine their localization patterns in the brain.Sprague-Dawley rats received 50 mg kg^-1 single i.p dose of each drug. Mass spectrometric techniques were then used to investigate the pharmacokinetics and localization patterns of these drugs in the brain using LC-MS/MS and mass spectrometric imaging (MSI), respectively.Abacavir, stavudine and didanosine reached the Brain C_max with concentration of 831.2, 1300 and 43.37 ngmL^-1, respectively. Based on MSI analysis Abacavir and Stavudine were located in brain regions that are strongly implicated in the progression of HAND.Abacavir and Stavudine penetrated into CNS, reaching a C_max that was above the IC₅₀ for HIV (457.6 and 112.0 ngmL^-1, respectively), however, it was noted ddI showed poor entry within the brain, therefore, it is recommended that this drug cannot be considered for treating CNS-HIV.

CNS penetration of ART in HIV-infected children

Background

Paediatric data on CNS penetration of antiretroviral drugs are scarce.

Objectives

To evaluate CNS penetration of antiretroviral drugs in HIV-infected children and explore associations with neurocognitive function.

Patients and methods

Antiretroviral drug levels were measured in paired CSF and blood samples of clinically stable HIV-infected children between 8 and 18 years old on long-term combined ART. Plasma drug concentrations were corrected for protein binding. We evaluated CNS penetration using CSF/plasma ratios and compared CSF concentrations with the IC50 as a surrogate marker for effectiveness. Blood-brain barrier permeability was assessed for possible confounding. Associations with neurocognitive function were explored using linear regression analysis.

Results

Median CSF/plasma ratios (IQR) were: lopinavir 0.059 (0.024-0.157, n = 7), efavirenz 0.681 (0.555-0.819, n = 12), tenofovir 0.021 (0.020-0.024, n = 4), lamivudine 0.464 (0.331-0.607, n = 17), emtricitabine 0.365 (0.343-0.435, n = 3), nevirapine 1.203 (n = 1), zidovudine 0.718 (0.711-1.227, n = 5) and abacavir 1.344 (0.670-2.450, n = 10). CSF concentrations were below the IC50 for tenofovir (100%), emtricitabine (100%), abacavir (50%) and zidovudine (17%). Lamivudine, lopinavir, efavirenz and nevirapine concentrations were all above the IC50. All participants were virologically suppressed in blood and CSF. CSF drug concentrations were not associated with blood-brain barrier permeability or neurocognitive function.

Conclusions

We showed adequate CSF concentrations of lamivudine, lopinavir, efavirenz and nevirapine, and potential suboptimal CSF concentrations of tenofovir, abacavir and emtricitabine in long-term treated HIV-infected children. None the less, the use of combined antiretroviral drugs led to adequate viral suppression.

Determination of nucleosidic/tidic reverse transcriptase inhibitors in plasma and cerebrospinal fluid by ultra-high-pressure liquid chromatography coupled with tandem mass spectrometry

Nucleoside reverse transcriptase inhibitors (NRTIs) have been the first class of antiretroviral drugs used against HIV infection. Despite NRTI-free regimens have been eagerly sought over the years in an effort for treatment simplification, NRTIs remain in most antiretroviral combination treatment. There has been generally a limited interest for their therapeutic drug monitoring, arguably because NRTIs levels measured in plasma poorly predict the concentration of pharmacologically active metabolites in cells. Plasma concentrations do impact cellular levels, while large differences between NRTIs have been found with regard to their ability to distribute into the cerebrospinal fluid (CSF) compartment. The renewed interest for the measurements of NRTIs concentrations in plasma and CSF was raised by ongoing efforts to understand some instances of toxicity or for determining their actual implication in the development of HIV-associated neurological disorders. In this context, a 5-min multiplex ultra-high-pressure chromatography tandem mass spectrometry (UHPLC-MS/MS) analysis in human plasma and CSF was developed for NRTIs used in clinical practice: abacavir, emtricitabine, lamivudine, tenofovir and zidovudine along with zidovudine glucuronide (Gln-ZDV). The 200-fold dilution of blank human plasma was shown to be a reliable surrogate matrix for quantification of NRTIs and Gln-ZDV in CSF. Both methodologies were fully validated over the clinically relevant concentrations, and satisfactorily fulfilled all parameters for bioanalytical methods validation. This sensitive, rapid, and robust UHPLC-MS/MS assay offers a methodology for increasing our understanding of the ability of NRTIs to cross the blood-brain barrier and their potential implication in neuropsychological disorders observed in HIV-infected patients.

Reduced antiretroviral drug efficacy and concentration in HIV-infected microglia contributes to viral persistence in brain

BACKGROUND

In patients with HIV/AIDS receiving antiretroviral therapy (ART), HIV-1 persistence in brain tissue is a vital and unanswered question. HIV-1 infects and replicates in resident microglia and trafficking macrophages within the brain although the impact of individual ART drugs on viral infection within these brain myeloid cells is unknown. Herein, the effects of contemporary ART drugs were investigated using in vitro and in vivo models of HIV-1 brain infection.

RESULTS

The EC₅₀ values for specific ART drugs in HIV-infected human microglia were significantly higher compared to bone marrow-derived macrophages and peripheral blood mononuclear cells. Intracellular ART drug concentrations in microglia were significantly lower than in human lymphocytes. In vivo brain concentrations of ART drugs in mice were 10 to 100-fold less in brain tissues compared with plasma and liver levels. In brain tissues from untreated HIV-infected BLT mice, HIV-encoded RNA, DNA and p24 were present in human leukocytes while ART eradicated viral RNA and DNA in both brain and plasma. Interruption of ART resulted in detectable viral RNA and DNA and increased human CD68 expression in brains of HIV-infected BLT mice. In aviremic HIV/AIDS patients receiving effective ART, brain tissues that were collected within hours of last ART dosing showed HIV-encoded RNA and DNA with associated neuroinflammatory responses.

CONCLUSIONS

ART drugs show variable concentrations and efficacies in brain myeloid cells and tissues in drug-specific manner. Despite low drug concentrations in brain, experimental ART suppressed HIV-1 infection in brain although HIV/AIDS patients receiving effective ART had detectable HIV-1 in brain. These findings suggest that viral suppression in brain is feasible but new approaches to enhancing ART efficacy and concentrations in brain are required for sustained HIV-1 eradication from brain.

Ocular and Cerebrospinal Fluid Penetration of Antiretroviral Agents

PURPOSE

The ocular penetration of systemically administered antiretroviral drugs (ARVs), which is important in the clinical setting of HIV uveitis, is unknown. This study aimed to assess the ocular penetration of different antiretroviral drugs in an animal model.

METHODS

Twenty-five male New Zealand white rabbits were assigned to one of five treatment groups. Each group received a single oral dose of an antiretroviral drug (lamivudine, tenofovir, efavirenz, lopinavir, and raltegravir). These 5 drugs represent 4 different ARV drug classes [nucleoside reverse transcriptase inhibitors (NRTI), non-NRTI, protease inhibitors, and integrase inhibitors]. Serum, cerebrospinal fluid (CSF), and aqueous and vitreous humor samples were collected at the time of theoretical maximum serum concentration of each respective drug, for example, lamivudine 1 h, tenofovir 1 h, efavirenz 5 h, lopinavir 4 h, and raltegravir 3 h. The drug concentration in each sample was determined by means of high-performance liquid chromatography and mass spectrometry.

RESULTS

After a single oral dose, measurable levels of all five ARVs administered could be detected in all 4 body compartments. The limit of detection based on a signal-to-noise ratio of 1:3 for the antiretroviral agents was as follows: 1 part per billion (ppb) for lamivudine, tenofovir, and efavirenz and 0.1 ppb for lopinavir and raltegravir. The IC50 (inhibitory concentration where 50% of viral replication is inhibited by a drug) was reached for all drugs in the serum and CSF. In the aqueous humor, lopinavir failed to reach IC50 and in the vitreous humor, only efavirenz and lopinavir attained IC50 levels.

CONCLUSION

After a single oral dose, measurable levels of all 4 classes of ARVs could be detected in all 4 body compartments sampled. In the eye, IC50 levels were lower in the vitreous humor than in aqueous humor. IC50 levels in the serum were higher than in the CSF.

Pharmacokinetics and pharmacodynamics of antiretrovirals in the central nervous system

HIV-positive patients may be effectively treated with highly active antiretroviral therapy and such a strategy is associated with striking immune recovery and viral load reduction to very low levels. Despite undeniable results, the central nervous system (CNS) is commonly affected during the course of HIV infection, with neurocognitive disorders being as prevalent as 20-50 % of treated subjects. This review discusses the pathophysiology of CNS infection by HIV and the barriers to efficacious control of such a mechanism, including the available data on compartmental drug penetration and on pharmacokinetic/pharmacodynamic relationships. In the reviewed articles, a high variability in drug transfer to the CNS is highlighted with several mechanisms as well as methodological issues potentially influencing the observed results. Nevirapine and zidovudine showed the highest cerebrospinal fluid (CSF) to plasma ratios, although target concentrations are currently unknown for the CNS. The use of the composite CSF concentration effectiveness score has been associated with better virological outcomes (lower HIV RNA) but has been inconsistently associated with neurocognitive outcomes. These findings support the CNS effectiveness of commonly used highly antiretroviral therapies. The use of antiretroviral drugs with increased CSF penetration and/or effectiveness in treating or preventing neurocognitive disorders however needs to be assessed in well-designed prospective studies.

ING116070: a study of the pharmacokinetics and antiviral activity of dolutegravir in cerebrospinal fluid in HIV-1-infected, antiretroviral therapy-naive subjects

Median dolutegravir concentrations in cerebrospinal fluid were similar to unbound concentrations in plasma and all subjects exceeded the in vitro 50% inhibitory concentration for wild-type viruses (0.2 ng/mL) by ≥66-fold, suggesting therapeutic concentrations are achieved in cerebrospinal fluid..

Background. Dolutegravir (DTG), a once-daily, human immunodeficiency virus type 1 (HIV-1) integrase inhibitor, was evaluated for distribution and antiviral activity in cerebrospinal fluid (CSF).

Methods. ING116070 is an ongoing, single-arm, open-label, multicenter study in antiretroviral therapy–naive, HIV-1–infected adults. Subjects received DTG (50 mg) plus abacavir/lamivudine (600/300 mg) once daily. The CSF and plasma (total and unbound) DTG concentrations were measured at weeks 2 and 16. The HIV-1 RNA levels were measured in CSF at baseline and weeks 2 and 16 and in plasma at baseline and weeks 2, 4, 8, 12, and 16.

Results. Thirteen white men enrolled in the study; 2 withdrew prematurely, 1 because of a non–drug-related serious adverse event (pharyngitis) and 1 because of lack of treatment efficacy. The median DTG concentrations in CSF were 18 ng/mL (range, 4–23 ng/mL) at week 2 and 13 ng/mL (4–18 ng/mL) at week 16. Ratios of DTG CSF to total plasma concentration were similar to the unbound fraction of DTG in plasma. Median changes from baseline in CSF (n = 11) and plasma (n = 12) HIV-1 RNA were −3.42 and −3.04 log₁₀ copies/mL, respectively. Nine of 11 subjects (82%) had plasma and CSF HIV-1 RNA levels <50 copies/mL and 10 of 11 (91%) had CSF HIV-1 RNA levels <2 copies/mL at week 16.

Conclusions. The DTG concentrations in CSF were similar to unbound plasma concentrations and exceeded the in vitro 50% inhibitory concentration for wild-type HIV (0.2 ng/mL), suggesting that DTG achieves therapeutic concentrations in the central nervous system. The HIV-1 RNA reductions were similar in CSF and plasma.

Clinical Trials Registration. NCT01499199.

Proteasome inhibitors act as bifunctional antagonists of human immunodeficiency virus type 1 latency and replication

Background

Existing highly active antiretroviral therapy (HAART) effectively controls viral replication in human immunodeficiency virus type 1 (HIV-1) infected individuals but cannot completely eradicate the infection, at least in part due to the persistence of latently infected cells. One strategy that is being actively pursued to eliminate the latent aspect of HIV-1 infection involves therapies combining latency antagonists with HAART. However, discordant pharmacokinetics between these types of drugs can potentially create sites of active viral replication within certain tissues that might be impervious to HAART.

Results

A preliminary reverse genetic screen indicated that the proteasome might be involved in the maintenance of the latent state. This prompted testing to determine the effects of proteasome inhibitors (PIs) on latently infected cells. Experiments demonstrated that PIs effectively activated latent HIV-1 in several model systems, including primary T cell models, thereby defining PIs as a new class of HIV-1 latency antagonists. Expanding upon experiments from previous reports, it was also confirmed that PIs inhibit viral replication. Moreover, it was possible to show that PIs act as bifunctional antagonists of HIV-1. The data indicate that PIs activate latent provirus and subsequently decrease viral titers and promote the production of defective virions from activated cells.

Conclusions

These results represent a proof-of-concept that bifunctional antagonists of HIV-1 can be developed and have the capacity to ensure precise tissue overlap of anti-latency and anti-replication functions, which is of significant importance in the consideration of future drug therapies aimed at viral clearance.

CSF penetration by antiretroviral drugs

Severe HIV-associated neurocognitive disorders (HAND), such as HIV-associated dementia, and opportunistic CNS infections are now rare complications of HIV infection due to comprehensive highly active antiretroviral therapy (HAART). By contrast, mild to moderate neurocognitive disorders remain prevalent, despite good viral control in peripheral compartments. HIV infection seems to provoke chronic CNS injury that may evade systemic HAART. Penetration of antiretroviral drugs across the blood-brain barrier might be crucial for the treatment of HAND. This review identifies and evaluates the available clinical evidence on CSF penetration properties of antiretroviral drugs, addressing methodological issues and discussing the clinical relevance of drug concentration assessment. Although a substantial number of studies examined CSF concentrations of antiretroviral drugs, there is a need for adequate, well designed trials to provide more valid drug distribution profiles. Neuropsychological benefits and neurotoxicity of potentially CNS-active drugs require further investigation before penetration characteristics will regularly influence therapeutic strategies and outcome.

Clinical features and preliminary studies of virological correlates of neurocognitive impairment among HIV-infected individuals in Nigeria

In Nigeria, the incidence and prevalence of human immunodeficiency virus (HIV)-related neurocognitive impairment (NCI) are unknown and there currently exists little information related to the viral correlates rates of NCI. Therefore, studies were performed to examine the potential utility of applying an established neuropsychological (NP) screening battery and detailed NP testing to detect NCI and correlations with functional impairment and the presence of specific viral signatures among infected subjects. A total of 60 HIV-1 seropositive antiretroviral-naive individuals and 56 seronegative control subjects were administered the International HIV Dementia Scale (IHDS) and assessed for functional impairment using the Karnofsky performance status scale. Fifteen HIV-infected patients and 11 controls were also administered a detailed NP battery. Blood samples from eight infected subjects, three with evidence of NCI, were obtained for molecular analysis of HIV-1 strain. Unadjusted scores on the IHDS showed that, using a recommended total score cutoff of 10, 28.8% of the HIV-1 seropositive and 16.0% of seropositive individuals scored abnormally. Results from testing using the full NP battery showed that, overall, the HIV seropositive group performed worse than the seronegative group, with effect sizes spanning from small (0.25 on the trail making test A) to large (0.82 on action fluency), and an average effect size across the battery of 0.45, which approaches that which has been recorded in other international settings. Sequencing of partial pol amplicons from viral isolates revealed that two of three patients with NCI were infected with subtype G virus and 1 with the circulating recombinant form (CRF)02_AG; all four individuals without NCI were infected with CRF_02AG. These studies demonstrate the utility of the IHDS in identifying cognitive impairment among HIV infected individuals in Nigeria. Future studies aimed at examining the burden of NCI among the population of individuals with HIV-1 infection in Nigeria and which assess the virologic correlates will contribute to the evolving understanding of the pathogenetic factors that underlie this disorder.

Analysis of correlation between cerebrospinal fluid and plasma HIV-1 RNA levels in patients with neurological opportunistic diseases

The question of whether HIV-1 RNA in cerebrospinal fluid (CSF) is derived from viral replication in the central nervous system or simply reflects the transit of infected lymphocytes from the blood compartment has long been a matter of debate. Some studies found no correlation between CSF and plasma viral load, whereas others did. The lack of a correlation between the two compartments suggests that the presence of HIV-1 RNA is not simply due to the passive passage of the virus from blood to CSF but rather due to intrathecal replication. To evaluate the correlation between plasma and CSF HIV-1 RNA levels and to identify situations in which there is no correlation between the two compartments, seventy patients were prospectively studied. The association between CSF and plasma viral load was evaluated in the total population and in subgroups of patients with similar characteristics. A correlation between the CSF and plasma compartments was observed for patients undergoing highly active antiretroviral therapy (HAART), those with a CD4 T lymphocyte count lower than 200 cells/mm³, and those with increased CSF protein content. On the other hand, no correlation was observed for patients without adequate virological control, who had a CD4 count higher than 200 cells/mm³ and who did not use HAART. The correlation between the two compartments observed in some patients suggests that CSF HIV-1 RNA levels may reflect plasma levels in these subjects. In contrast, the lack of a correlation between the two compartments in patients who were not on HAART and who had normal CSF proteins and a poor virological control possibly indicates compartmentalization of the virus in CSF and, consequently, plasma-independent intrathecal viral replication.

HIV-associated neurological disorders: a guide to pharmacotherapy

In the era of highly active antiretroviral therapy (HAART), HIV-1-associated neurocognitive disorder (HAND) continues to be a common and significant morbidity among individuals infected with HIV. The term HAND encompasses a spectrum of progressively severe CNS involvement, ranging from asymptomatic neurocognitive impairment and minor neurocognitive disorder through to the most severe form of HIV-associated dementia (HAD). While the incidence of HAD has declined significantly with HAART, the milder forms of HAND persist. In addition, HAND now develops in individuals with less advanced immunosuppression. The reasons for the persistence of milder forms of HAND in individuals treated with HAART are not entirely known. There are several hypotheses to explain this phenomenon that include the legacy effect, a failure of antiretroviral agents to reverse neurological damage, poor access of antiretroviral agents to the CNS, chronic systemic immune activation associated with microbial translocation products, sustained CNS inflammation, the improved survival of HIV-seropositive individuals and the possible contribution from aging, amyloid deposition and other co-morbidities. In contrast, the incidence of HIV-associated CNS opportunistic processes including progressive multifocal leukoencephalopathy, tuberculosis, CNS toxoplasmosis, cytomegalovirus encephalitis, cryptococcosis and primary CNS lymphoma has declined dramatically with the introduction of HAART. This review briefly summarizes our current understanding of HAND and the pathological mechanisms involved, namely direct injury from HIV-1 and viral proteins, indirect neurotoxicity from proinflammatory cytokines and chronic, sustained immune activation in the CNS. To date, only HAART has been shown to benefit HAND despite numerous controlled trials of adjunctive 'anti-inflammatory' agents. Although HAART has a profound impact on the incidence and severity of HAND, there exists a 'therapeutic gap' as even HAART that is effective at inducing durable virological suppression may only partially reverse HAND. In addition, there may be potential CNS adverse effects of antiretroviral agents. There is an ongoing multicentre clinical trial to investigate the role of the CNS Penetration-Effectiveness index, an indicator of drug permeability and availability in the CNS, to help guide the choice of antiretroviral agents in the treatment of HAND. With recent recommendations for earlier treatment intervention with HAART for HIV-1 infection, it remains to be seen the effects of this on HAND. There is an urgent need to better define the therapeutic guidelines for the prevention and treatment of HAND.

Penetration of drugs through the blood-cerebrospinal fluid/blood-brain barrier for treatment of central nervous system infections

The entry of anti-infectives into the central nervous system (CNS) depends on the compartment studied, molecular size, electric charge, lipophilicity, plasma protein binding, affinity to active transport systems at the blood-brain/blood-cerebrospinal fluid (CSF) barrier, and host factors such as meningeal inflammation and CSF flow. Since concentrations in microdialysates and abscesses are not frequently available for humans, this review focuses on drug CSF concentrations. The ideal compound to treat CNS infections is of small molecular size, is moderately lipophilic, has a low level of plasma protein binding, has a volume of distribution of around 1 liter/kg, and is not a strong ligand of an efflux pump at the blood-brain or blood-CSF barrier. When several equally active compounds are available, a drug which comes close to these physicochemical and pharmacokinetic properties should be preferred. Several anti-infectives (e.g., isoniazid, pyrazinamide, linezolid, metronidazole, fluconazole, and some fluoroquinolones) reach a CSF-to-serum ratio of the areas under the curves close to 1.0 and, therefore, are extremely valuable for the treatment of CNS infections. In many cases, however, pharmacokinetics have to be balanced against in vitro activity. Direct injection of drugs, which do not readily penetrate into the CNS, into the ventricular or lumbar CSF is indicated when other effective therapeutic options are unavailable.

Maraviroc-containing regimen suppresses HIV replication in the cerebrospinal fluid of patients with neurological symptoms

We report the concentrations of maraviroc in the cerebrospinal fluid (CSF) and plasma of six HIV-1-infected patients with both neurological impairment and detectable HIV-1 replication in CSF. One month after starting maraviroc, the viral load in the CSF decreased significantly (P = 0.005). The median (range) maraviroc concentration in plasma was 347 ng/ml (123-2678). Four patients had CSF concentrations above the protein-adjusted inhibitory concentration (IC90) of 0.57 ng/ml (0.06-10.7) with a median of 102 ng/ml (35-173).

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).

Identification of a potential pharmacological sanctuary for HIV type 1 in a fraction of CD4(+) primary cells

We have identified a subset of HIV-susceptible CD4(+)CCR5(+) cells in human PBMCs that can efficiently exclude protease inhibitors (PI) due to high P-glycoprotein (P-gp) efflux activity. Phenotypically these cells are heterogeneous, include both T and non-T cells, and some display markers of memory cells. Cells with high P-gp represent 16-56% (median = 37.3) of all CD4(+)CCR5(+) cells in healthy donors, and are selectively depleted in HIV-1-infected individuals (4.1-33%, median = 10.1). A fraction of primary cells productively infected by HIV-1, in vitro, have high P-gp pump activity, demonstrating that infection does not inhibit P-gp function. In agreement with these data, HIV-susceptible cells expressing high levels of P-gp require higher levels of PI for complete inhibition of virus spread. We conclude that the PI concentrations achieved in plasma could be suboptimal for full inhibition of virus spread in high P-gp cells, indicating that they may represent a pharmacological sanctuary for HIV-1.

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.

Regulation of SIV mac 239 basal long terminal repeat activity and viral replication in macrophages: functional roles of two CCAAT/enhancer-binding protein beta sites in activation and interferon beta-mediated suppression

CCAAT/enhancer-binding protein (C/EBP) beta and C/EBP sites in the HIV-1 long terminal repeat (LTR) are crucial for HIV-1 replication in monocyte/macrophages and for the ability of interferon beta (IFN beta) to inhibit ongoing active HIV replication in these cells. This IFN beta-mediated down-regulation involves induction of the truncated, dominant-negative isoform of C/EBP beta referred to as liver-enriched transcriptional inhibitory protein (LIP). Although binding of the C/EBP beta isoform to C/EBP sites in the simian immunodeficiency virus (SIV) LTR has previously been examined, the importance of these sites in core promoter-mediated transcription, virus replication, IFN beta-mediated regulation, and the relative binding of the two isoforms (C/EBP beta and LIP) has not been investigated. Here, we specifically examine two C/EBP sites, JC1 (-100 bp) and DS1 (+134 bp), located within the minimal region of the SIV LTR, required for core promoter-mediated transcription and virus replication in macrophages. Our studies revealed that the JC1 but not DS1 C/EBP site is important for basal level transcription, whereas the DS1 C/EBP site is imperative for productive virus replication in primary macrophages. In contrast, either JC1 or DS1 C/EBP site is sufficient to mediate IFN beta-induced down-regulation of SIV LTR activity and virus replication in these cells. We also characterized the differential binding properties of C/EBP beta and LIP to the JC1 and DS1 sites. In conjunction with previous studies from our laboratory, we demonstrate the importance of these sites in virus gene expression, and we propose a model for their role in establishing latency and persistence in macrophages in the brain.

Clinical implications of antiretroviral pharmacokinetics and pharmacodynamics in the CNS

The prevalence of HIV-associated brain disease remains high in the combination antiretroviral era. Factors associated with the development of HIV-associated neurocognitive impairment remain poorly understood. The selection of an antiretroviral regimen that can successfully penetrate the CNS compartment and control cerebrospinal fluid HIV replication may prove a crucial strategy in preventing the emergence and progression of HIV-associated neurocognitive impairment. Different antiretroviral agents and drug classes vary in their ability to penetrate the CNS. In this review, data on the CNS penetration of antiretrovirals are evaluated, including the clinical studies examining their relevance. Prospective studies examining the effect of different treatment strategies on CNS clinical outcomes are needed.

Treatment intensification does not reduce residual HIV-1 viremia in patients on highly active antiretroviral therapy

In HIV-1-infected individuals on currently recommended antiretroviral therapy (ART), viremia is reduced to <50 copies of HIV-1 RNA per milliliter, but low-level residual viremia appears to persist over the lifetimes of most infected individuals. There is controversy over whether the residual viremia results from ongoing cycles of viral replication. To address this question, we conducted 2 prospective studies to assess the effect of ART intensification with an additional potent drug on residual viremia in 9 HIV-1-infected individuals on successful ART. By using an HIV-1 RNA assay with single-copy sensitivity, we found that levels of viremia were not reduced by ART intensification with any of 3 different antiretroviral drugs (efavirenz, lopinavir/ritonavir, or atazanavir/ritonavir). The lack of response was not associated with the presence of drug-resistant virus or suboptimal drug concentrations. Our results suggest that residual viremia is not the product of ongoing, complete cycles of viral replication, but rather of virus output from stable reservoirs of infection.

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.

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.

Changes in the incidence and predictors of human immunodeficiency virus-associated dementia in the era of highly active antiretroviral therapy

OBJECTIVE

Though effective anti-human immunodeficiency virus (HIV) therapies are now available, they have variable penetration into the brain. We therefore aimed to assess changes over calendar time in the risk for HIV-associated dementia (HIV-D), and factors associated with HIV-D risk.

METHODS

Using Concerted Action on Seroconversion to AIDS and Death in Europe (CASCADE) data, we analyzed factors associated with time from HIV seroconversion to HIV-D using Cox models with time-updated covariates. The effect of duration of infection was explored using flexible parametric survival models.

RESULTS

222 of 15,380 seroconverters developed HIV-D. The incidence per 1,000 person-years was 6.49 pre-1997 (before highly active antiretroviral therapy was available), declining to 0.66 by 2003 to 2006. Compared with most recent CD4 count > or = 350 cells/mm3, the adjusted relative risk (95% confidence interval) of HIV-D was 3.47 (1.91-6.28), 10.19 (5.72-18.15), and 39.03 (22.96-66.36) at 200 to 349, 100 to 199, and 0 to 99 cells/mm3, respectively. In 2003 to 2006, older age at seroconversion (relative risk = 3.24 per 10-year increase [95% confidence interval, 2.00-5.24]) and previous acquired immune deficiency syndrome diagnosis (relative risk = 4.92 [95% confidence interval, 1.43-16.92]) were associated with HIV-D risk, independently of current CD4 count. HIV-D risk appeared to increase during chronic infection, by 48% at 10 years after seroconversion compared with the lowest risk at 1.8 years.

INTERPRETATION

HIV-D incidence has reduced markedly since 1997. However, patients with low (<200 cells/mm3) or even intermediate (200-349 cells/mm3) CD4 counts, previous acquired immune deficiency syndrome diagnosis, longer HIV infection duration, and older age at seroconversion are at increased risk and should be closely monitored for neurocognitive disorders.

Factors in AIDS dementia complex trial design: results and lessons from the abacavir trial

Objectives:

To determine the efficacy of adding abacavir (Ziagen, ABC) to optimal stable background antiretroviral therapy (SBG) to AIDS dementia complex (ADC) patients and address trial design.

Design:

Phase III randomized, double-blind placebo-controlled trial.

Setting:

Tertiary outpatient clinics.

Participants:

ADC patients on SBG for ≥8 wk.

Interventions:

Participants were randomized to ABC or matched placebo for 12 wk.

Outcome Measures:

The primary outcome measure was the change in the summary neuropsychological Z score (NPZ). Secondary measures were HIV RNA and the immune activation markers β-2 microglobulin, soluble tumor necrosis factor (TNF) receptor 2, and quinolinic acid.

Results:

105 participants were enrolled. The median change in NPZ at week 12 was +0.76 for the ABC + SBG and +0.63 for the SBG groups (p = 0.735). The lack of efficacy was unlikely related to possible limited antiviral efficacy of ABC: at week 12 more ABC than placebo participants had plasma HIV RNA ≤400 copies/mL (p = 0.002). There were, however, other factors. Two thirds of patients were subsequently found to have had baseline resistance to ABC. Second, there was an unanticipated beneficial effect of SBG that extended beyond 8 wk to 5 mo, thereby rendering some of the patients at baseline unstable. Third, there was an unexpectedly large variability in neuropsychological performance that underpowered the study. Fourth, there was a relative lack of activity of ADC: 56% of all patients had baseline cerebrospinal fluid (CSF) HIV-1 RNA <100 copies/mL and 83% had CSF β-2 microglobulin <3 nmol/L at baseline.

Conclusions:

The addition of ABC to SBG for ADC patients was not efficacious, possibly because of the inefficacy of ABC per se, baseline drug resistance, prolonged benefit from existing therapy, difficulties with sample size calculations, and lack of disease activity. Assessment of these trial design factors is critical in the design of future ADC trials.

Background: AIDS dementia complex (ADC) was first identified early in the HIV epidemic and at that time affected a substantial proportion of patients with AIDS. Patients with ADC experience dementia as well as disordered behavior and problems with movement and balance. ADC is now much less common in locations where patients have access to HAART (highly active antiretroviral therapy), consisting of combinations of several drugs that attack the virus at different stages of its life cycle. At present, however, there are no generally accepted guidelines for the best treatment of people with ADC. It has been thought for some time that the best treatment regimens for people with ADC would include drugs that cross the barrier between blood and brain well. Shortly following the introduction of HAART, a trial was carried out to find out whether adding one particular drug, abacavir, to existing combinations of drugs would be beneficial in people with ADC. This drug is known to cross the barrier between the blood and brain. The trial enrolled HIV-positive individuals with mild to moderate ADC and who were already receiving antiretroviral drug treatment. 105 participants were assigned at random to receive either high-dose abacavir or a placebo, in addition to their existing therapy. The primary outcome of the trial was a summary of performance on a set of different tests, designed to evaluate cognitive, behavior, and movement skills, at 12 weeks. Other outcomes included levels of HIV RNA (viral load) in fluid around the brain, as well as other neurological evaluations, and the level of HIV RNA and CD4⁺ T cells (the cells infected by HIV) in blood.

What this trial shows: When comparing the change in performance scores for individuals randomized to either abacavir or placebo, the results showed an improvement in scores for both groups, but no significant difference in improvement between the two groups. Similarly, the levels of HIV RNA in the cerebrospinal fluid did not differ between the two groups being compared, and other neurological tests did not show any differences between the two groups. However, at 12 weeks, patients receiving abacavir were more likely to have low levels of HIV RNA in their blood, suggesting that abacavir was active against the virus, but this did not translate into an additional improvement of these patients' dementia. The overall rates of adverse events were roughly comparable between the two groups in the trial, although participants receiving abacavir were more likely to experience certain types of events, such as nausea.

Strengths and limitations: The trial was appropriately randomized and controlled, using central telephone procedures for randomizing participants and subsequent blinding of patients and trial investigators. These procedures help minimize the chance of bias in assigning participants to the different arms as well as in the subsequent performance of individuals within the trial and the assessment of their outcomes. Limitations in the study design have been identified. One limitation is that individuals enrolled into the trial may not in fact have been receiving their existing HAART regimen for long enough to experience its optimal effect, and therefore the improvement seen in both groups could have resulted from an ongoing response to their existing regimen. It is also possible that patients improved in their test scores over the course of the trial simply because they became more familiar with the tests and not because their condition improved. This is a problem in all such trials that try to improve mental function. Finally, a limitation may have been the inclusion of patients who did not have active disease leading to worsening dementia.

Contribution to the evidence: The findings from this trial suggest that adding high-dose abacavir to existing HAART is not beneficial for patients with ADC. However, the trial provides several insights into the way that future studies of this type can be done, and which typically pose a number of challenging design problems. In particular, sensitive markers are needed that will allow researchers to monitor progression of ADC and patients' response to therapy.

Cerebrospinal Fluid Viral Loads Reach Less than 2 Copies/ML in HIV-1-Infected Patients with Effective Antiretroviral Therapy

Background

A low-grade persisting viraemia despite long-term treatment with highly active antiretroviral therapy (HAART) has previously been demonstrated in HIV-1-infected patients. Whether ongoing viral replication also could be detected in cerebrospinal fluid (CSF) in those circumstances has not been studied before.

Methods

Paired CSF and blood samples from 13 neurologically asymptomatic HIV-1-infected patients on stable HAART were analysed regarding HIV-1 RNA, by using a PCR assay with a detection limit of 2 copies/ml.

Results

All 13 patients had HIV-1 RNA <2 copies/ml in CSF, compared with 8/13 in plasma.

Conclusion

We could not demonstrate any persistent viral replication in the CSF of neurologically asymptomatic HIV-1-infected patients on effective HAART, rendering it unlikely that CSF acts as a viral reservoir in this category of patients.

Nanoparticulate drug carriers for delivery of HIV/AIDS therapy to viral reservoir sites

Providing the optimum treatment of AIDS is a major challenge in the 21st Century. HIV is localised and harboured in certain inaccessible compartments of the body, such as the CNS, the cerebrospinal fluid, the lymphatic system and in the macrophages, where it cannot be reached by the majority of therapeutic agents in adequate concentrations or in which the therapeutic agents cannot reside for the necessary duration. Progression in HIV/AIDS treatment suggests that available therapy can lower the systemic viral load below the detection limit. However, on discontinuation of treatment, there is relapse of the infection from the reservoir sites and a potential for resistance development. This review discusses the aetiology and pathology of HIV, with emphasis on the viral reservoirs, current therapy of AIDS, and the opportunity for nanotechnology-based drug delivery systems to facilitate complete eradication of viral load from the reservoir sites. Literature-cited examples of drug delivery systems that are under investigation for the treatment of AIDS are discussed. The article also focuses on the future outlook and strategies for investigational drug formulations that use nanotherapeutic strategy for HIV/AIDS.

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.

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.

Changing patterns in the neuropathogenesis of HIV during the HAART era

Rapid progress in the development of highly active antiretroviral therapy has changed the observed patterns in HIV encephalitis and AIDS-related CNS opportunistic infections. Early in the AIDS epidemic, autopsy studies pointed to a high prevalence of these conditions. With the advent of nucleoside reverse transcriptase inhibitors, the prevalence at autopsy of opportunistic infections, such as toxoplasmosis and progressive multifocal leukoencephalopathy, declined while that of HIV encephalitis increased. After the introduction of protease inhibitors, a decline in both HIV encephalitis and CNS opportunistic infections was observed. However, with the increasing resistance of HIV strains to antiretrovirals, there has been a resurgence in the frequency of HIV encephalitis and HIV leukoencephalopathy. HIV leukoencephalopathy in AIDS patients failing highly active antiretroviral therapy is characterized by massive infiltration of HIV infected monocytes/macrophages into the brain and extensive white matter destruction. This condition may be attributable to interactions of anti-retrovirals with cerebrovascular endothelium, astroglial cells and white matter of the brain. These interactions may lead to cerebral ischemia, increased blood-brain barrier permeability and demyelination. Potential mechanisms of such interactions include alterations in host cell signaling that may result in trophic factor dysregulation and mitochondrial injury. We conclude that despite the initial success of combined anti-retroviral therapy, more severe forms of HIV encephalitis appear to be emerging as the epidemic matures. Factors that may contribute to this worsening include the prolonged survival of HIV-infected patients, thereby prolonging the brain's exposure to HIV virions and proteins, the use of increasingly toxic combinations of poorly penetrating drugs in highly antiretroviral-experienced AIDS patients, and selection of more virulent HIV strains with higher replication rates and greater virulence in neural tissues.

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.

Efficacy of cerebrospinal fluid (CSF)-penetrating antiretroviral drugs against HIV in the neurological compartment: different patterns of phenotypic resistance in CSF and plasma

BACKGROUND

Cerebrospinal fluid (CSF) concentrations of multiple drugs in a large human immunodeficiency virus (HIV)-infected patient population, the virtual phenotype profiles for HIV in the plasma and CSF compartments, and the correlation of these profiles with exposure to antiretroviral therapy need to be further investigated.

METHODS

Drug concentrations in CSF and plasma were concomitantly determined for a large group of HIV-infected individuals receiving highly active antiretroviral therapy (HAART). Samples were analyzed using a validated method consisting of liquid chromatography with mass spectrometry. For patients with detectable levels of virus, genotypic analysis was performed, followed by a virtual phenotype study.

RESULTS

Sixty-three HIV-infected patients were included in the study, 78% of whom were affected by neurological disease. Drug concentrations in CSF specimens were undetectable for didanosine, efavirenz, nelfinavir, and concomitantly administered ritonavir and saquinavir. CSF concentrations were higher for nevirapine, with a median CSF-to-plasma concentration ratio of 0.63, followed by lamivudine (0.23), stavudine (0.20), and indinavir (0.11). In 18 of the 40 patients with virtual phenotype data available for virus recovered from CSF samples and from plasma samples, differences in fold-change of resistance between the CSF virus and the plasma virus were noted for at least 1 drug. Factors associated with having differences in fold-change of resistance were number of drugs to which the patient had been exposed (P=.02) and presence of neurological disease (P=.05). A significant association was found between duration of therapy and fold-change of resistance in CSF and plasma isolates.

CONCLUSIONS

Antiretrovirals have different levels of penetration in the CSF, with several drugs achieving only low CSF concentrations. CSF isolates have different resistance profiles than do plasma isolates. Effective treatment decisions for CSF manifestations of disease may require better knowledge of drug penetration and the drug susceptibility of HIV in the CSF.

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.

Molecular mechanisms of HIV-1 associated neurodegeneration

Since identification of the human immunodeficiency virus-1 (HIV-1), numerous studies suggest a link between neurological impairments, in particular dementia, with acquired immunodeficiency syndrome (AIDS) with alarming occurrence worldwide. Approximately, 60% of HIV-infected people show some form of neurological impairment, and neuropathological changes are found in 90% of autopsied cases. Approximately 30% of untreated HIV-infected persons may develop dementia. The mechanisms behind these pathological changes are still not understood. Mounting data obtained by in vivo and in vitro experiments suggest that neuronal apoptosis is a major feature of HIV associated dementia (HAD), which can occur in the absence of direct infection of neurons. The major pathway of neuronal apoptosis occurs indirectly through release of neurotoxins by activated cells in the central nervous system (CNS) involving the induction of excitotoxicity and oxidative stress. In addition a direct mechanism induced by viral proteins in the pathogenesis of HAD may also play a role. This review focuses on the molecular mechanisms of HIV-associated dementia and possible therapeutic strategies.

The AIDS dementia complex: clinical and basic neuroscience with implications for novel molecular therapies

The AIDS dementia complex (ADC, also referred to as HIV-associated cognitive impairment) is a common disorder among HIV-infected patients associated with both inflammatory and neurodegenerative processes. This review describes recent advances in the clinical and basic neurosciences of HIV infection and discusses the multivariable nature of what has become a chronic disorder in the context of highly active antiretroviral therapies (HAART). Since its initial description twenty years ago, advances in cell and molecular biology along with those in neuroimaging have furthered our understanding of the underlying pathogenic mechanisms. The clinical and neuropsychological profile of ADC is generally consistent with a "frontal-subcortical" pattern of injury. Neuropathogenesis is largely driven by indirect mechanisms mediated by infected, or more commonly, immune activated macrophages, which secrete viral and host-derived factors. Magnetic resonance spectroscopy (MRS) provides a robust in vivo method to measure the inflammatory and neurotoxic events triggered by these factors and their associated signals. Although the use of combined or highly active antiretroviral therapies (HAART) has significantly improved survival rates, cerebral injury and cognitive impairment remain common events. Factors such as aging and chronic infection will likely impact the course of this disease, its pathogenesis, and treatment. The combined observations presented in this review suggest a number of critical areas for future inquiry.

Isolated central nervous system involvement in adult T-cell lymphoma/leukaemia

Central nervous system (CNS) presentation of adult T-cell lymphoma/leukaemia is rare, and almost invariably associated with systemic disease. We report an unusual manifestation of adult T-cell lymphoma/leukaemia, with isolated CNS involvement and unusual imaging findings. We also describe objective response to antiviral therapy. To our knowledge, this is the first report of such presentation and response.

Population pharmacokinetics of abacavir in plasma and cerebrospinal fluid

The distribution of abacavir into the cerebrospinal fluid (CSF) was assessed by use of a population pharmacokinetic analysis. Plasma and CSF abacavir concentrations in 54 subjects were determined. The abacavir CSF/plasma ratio averaged 36% and increased throughout the dose interval. Abacavir penetrates into the CSF in adequate concentrations to inhibit local human immunodeficiency virus replication.

Factors affecting delivery of antiviral drugs to the brain

Although the CNS is in part protected from peripheral insults by the blood-brain barrier and the blood-cerebrospinal fluid barrier, a number of human viruses gain access to the brain, replicate within this organ, or sustain latent infection. The efficacy of antiviral drugs towards the cerebral viral load is often limited as both blood-brain interfaces impede their cerebral distribution. For polar compounds, the major factor restricting their entry lies in the tight junctions that occlude the paracellular pathway across these barriers. For compounds with more favourable lipid solubility properties, CNS penetration will be function of a number of physicochemical factors that include the degree of lipophilicity, size and ability to bind to protein or red blood cells, as well as other factors inherent to the vascular and choroidal systems, such as the local cerebral blood flow and the surface area available for exchange. In addition, influx and efflux transport systems, or metabolic processes active in both capillary endothelial cells and choroid plexus epithelial cells, can greatly change the bioavailability of a drug in one or several compartments of the CNS. The relative importance of these various factors with respect to the CNS delivery of the different classes of antiviral drugs is illustrated and discussed.

HIV-Tat protein induces P-glycoprotein expression in brain microvascular endothelial cells

Among the different factors which can contribute to CNS alterations associated with HIV infection, Tat protein is considered to play a critical role. Evidence indicates that Tat can contribute to brain vascular pathology through induction of endothelial cell activation. In the present study, we hypothesized that Tat can affect expression of P-glycoprotein (P-gp) in brain microvascular endothelial cells (BMEC). P-gp is an ATP-dependent cellular efflux transporter which is involved in the removal of specific non-polar molecules, including drugs used for highly active antiretroviral therapy (HAART). Treatment of BMEC with Tat(1-72) resulted in P-gp overexpression both at mRNA and protein levels. These alterations were confirmed in vivo in brain vessels of mice injected with Tat(1-72) into the hippocampus. Furthermore, pre-treatment of BMEC with SN50, a specific NF-kappaB inhibitor, protected against Tat(1-72)-stimulated expression of mdr1a gene, i.e. the gene which encodes for P-gp in rodents. Tat(1-72)-mediated changes in P-gp expression were correlated with increased rhodamine 123 efflux, indicating the up-regulation of transporter functions of P-gp. These results suggest that Tat-induced overexpression of P-gp in brain microvessels may have significant implications for the development of resistance to HAART and may be a contributing factor for low efficacy of HAART in the CNS.

Genetic composition of human immunodeficiency virus type 1 in cerebrospinal fluid and blood without treatment and during failing antiretroviral therapy

Human immunodeficiency virus (HIV) infection of the central nervous system (CNS) is a significant cause of morbidity. The requirements for HIV adaptation to the CNS for neuropathogenesis and the value of CSF virus as a surrogate for virus activity in brain parenchyma are not well established. We studied 18 HIV-infected subjects, most with advanced immunodeficiency and some neurocognitive impairment but none with evidence of opportunistic infection or malignancy of the CNS. Clonal sequences of C2-V3 env and population sequences of pol from HIV RNA in cerebrospinal fluid (CSF) and plasma were correlated with clinical and virologic variables. Most (14 of 18) subjects had partitioning of C2-V3 sequences according to compartment, and 9 of 13 subjects with drug resistance exhibited discordant resistance patterns between the two compartments. Regression analyses identified three to seven positions in C2-V3 that discriminated CSF from plasma HIV. The presence of compartmental differences at one or more of the identified positions in C2-V3 was highly associated with the presence of discordant resistance (P = 0.007), reflecting the autonomous replication of HIV and the independent evolution of drug resistance in the CNS. Discordance of resistance was associated with severity of neurocognitive deficits (P = 0.07), while low nadir CD4 counts were linked both to the severity of neurocognitive deficits and to discordant resistance patterns (P = 0.05 and 0.09, respectively). These observations support the study of CSF HIV as an accessible surrogate for HIV virions in the brain, confirm the high frequency of discordant resistance in subjects with advanced disease in the absence of opportunistic infection or malignancy of the CNS, and begin to identify genetic patterns in HIV env associated with adaptation to the CNS.

Stavudine Entry into Cerebrospinal Fluid After Single and Multiple Doses in Patients Infected with Human Immunodeficiency Virus

STUDY OBJECTIVE

To establish the pharmacokinetics of stavudine within the cerebrospinal fluid (CSF) of patients infected with human immunodeficiency virus (HIV).

DESIGN

Pharmacokinetic study.

SETTING

General clinical research center.

PATIENTS

Thirty-six patients infected with HIV; 21 were receiving long-term stavudine therapy, 15 were not (single-dose treatment group).

INTERVENTION

After an overnight fast, all patients received a single dose of stavudine 40 mg. Fifteen patients in the long-term treatment group and all 15 patients in the single-dose treatment group were randomized to undergo lumbar puncture 2, 4, or 6 hours after dosing (five patients for each time point from each group). The six other patients in the long-term treatment group underwent lumbar puncture 0 or 8 hours after dosing.

MEASUREMENTS AND MAIN RESULTS

Serum stavudine concentrations were obtained just before dosing, 1 hour after dosing (approximate peak), and at the time of lumbar puncture. The CSF was also analyzed for cell counts, protein, and glucose levels. The mean peak serum stavudine concentration in the long-term treatment group was estimated to be 580.7 ng/ml (2.59 micromol/L), occurring approximately 1.3 hours after dosing. The CSF concentrations over 0-8 hours were 0.0-109.9 ng/ml (0.00-0.49 micromol/L) with an overall mean of 51.6 ng/ml (0.23 micromol/L). Mean peak CSF concentration was estimated to be 62.8 ng/ml (0.28 micromol/L), occurring 4.7 hours after dosing. For the 15 patients not taking stavudine, both the serum and the CSF estimated peaks were significantly lower than those of the long-term group: 475.3 ng/ml (2.12 micromol/L) and 40.4 ng/ml (0.18 micromol/L), respectively. However, time to peak was similar at 1.2 hours and 5.0 hours, respectively. In both groups, no correlation was found between CSF and baseline or peak serum stavudine concentrations, CSF white blood cell count, baseline CD4 + lymphocyte count, or plasma viral load.

CONCLUSION

Mean CSF stavudine concentrations equaled or exceeded the mean concentration producing 50% of the maximal effect in vivo (EC 50 ) for HIV. The CSF concentrations were higher in the stavudine-experienced patients, indicating that concentrations rise with progressive doses until steady state is reached.