Pathogenicity and immunogenicity of attenuated, nef-deleted HIV-1 strains in vivo

In efforts to develop an effective vaccine, sterilizing immunity to primate lentiviruses has only been achieved by the use of live attenuated viruses carrying major deletions in nef and other accessory genes. Although live attenuated HIV vaccines are unlikely to be developed due to a myriad of safety concerns, opportunities exist to better understand the correlates of immune protection against HIV infection by studying rare cohorts of long-term survivors infected with attenuated, nef-deleted HIV strains such as the Sydney blood bank cohort (SBBC). Here, we review studies of viral evolution, pathogenicity, and immune responses to HIV infection in SBBC members. The studies show that potent, broadly neutralizing anti-HIV antibodies and robust CD8+ T-cell responses to HIV infection were not necessary for long-term control of HIV infection in a subset of SBBC members, and were not sufficient to prevent HIV sequence evolution, augmentation of pathogenicity and eventual progression of HIV infection in another subset. However, a persistent T-helper proliferative response to HIV p24 antigen was associated with long-term control of infection. Together, these results underscore the importance of the host in the eventual outcome of infection. Thus, whilst generating an effective antibody and CD8+ T-cell response are an essential component of vaccines aimed at preventing primary HIV infection, T-helper responses may be important in the generation of an effective therapeutic vaccine aimed at blunting chronic HIV infection.

Elevated Cerebrospinal Fluid Neurofilament Light Protein Concentrations Predict the Development of AIDS Dementia Complex

The light subunit of neurofilament protein (NFL) is a sensitive indicator of central nervous system axonal injury. We retrospectively identified 9 subjects participating in a longitudinal cohort study who developed acquired immunodeficiency syndrome dementia complex (ADC) and who had had a lumbar puncture performed within 2 years before presentation. Elevated cerebrospinal fluid (CSF) NFL concentrations were found in 7 (78%) of the 9 case patients who later developed ADC, compared with 9 (33%) of 27 CD4 cell count-matched HIV-1-infected control subjects. By contrast, no differences were found in CSF HIV-1 RNA or neopterin concentrations between the 2 groups. CSF NFL may prove to be a useful predictive marker for ADC.

CSF neurofilament protein (NFL) — a marker of active HIV-related neurodegeneration

BACKGROUND AND METHODS

The light subunit of the neurofilament protein (NFL), a major structural component of myelinated axons, is a sensitive indicator of axonal injury in the central nervous system (CNS) in a variety of neurodegenerative disorders. Cerebrospinal fluid (CSF) NFL concentrations were measured by ELISA (normal < 250 ng/l) in archived samples from 210 HIV-infected patients not taking antiretroviral treatment: 55 with AIDS dementia complex (ADC), 44 with various CNS opportunistic infections/tumours (CNS OIs), 95 without neurological symptoms or signs, and 16 with primary HIV infection (PHI). The effect of highly active antiretroviral treatment (HAART) was studied by repeated CSF sampling in four of the ADC patients initiating treatment.

RESULTS

CSF NFL concentrations were significantly higher in patients with ADC (median 2590 ng/l, IQR 780-7360) and CNS OIs (2315 ng/l, 985-7390 ng/l) than in neuroasymptomatic patients (<250 ng/l, <250-300) or PHI (<250 ng/l, <250-280), p < 0.001. Among patients with ADC, those with more severe disease (stage 2-4) had higher levels than those with milder disease (stage 0.5-1), p < 0.01. CSF NFL declined during HAART to the limit of detection in parallel with virological response and neurological improvement in ADC.CSF NFL concentrations were higher in neuroasymptomatic patients with lower CD4-cell strata than higher, p < 0.001. This increase was less marked than in the ADC patients and noted in 26/58 neuroasymptomatic patients with CD4 counts <200/microl compared to 1/37 with CD4-cells > or =200/microl.

CONCLUSIONS

The findings of this study support the value of CSF NFL as a useful marker of ongoing CNS damage in HIV infection. Markedly elevated CSF NFL concentrations in patients without CNS OIs are associated with ADC, follow the grade of severity, and decrease after initiation of effective antiretroviral treatment. Nearly all previously suggested CSF markers of ADC relate to immune activation or HIV viral load that do not directly indicate brain injury. By contrast NFL is a sensitive marker of such injury, and should prove useful in evaluating the presence and activity of ongoing CNS injury in HIV infection.

Human mesenchymal stem cells constitutively express chemokines and chemokine receptors that can be upregulated by cytokines, IFN-beta, and Copaxone

The factors associated with the migration of marrow-derived mesenchymal stem cells (MSCs) when transplanted into the diseased central nervous system (CNS) are unclear. Chemokines are key mediators of selective cell migration in neurodegenerative diseases and related inflammatory processes. We hypothesized that chemokines are likely to be the chief determinants of MSC migration. We, therefore, systematically assessed the expression and modulating factors for chemokines and chemokine receptors in human MSCs (HuMSCs). The present study demonstrates that unstimulated HuMSCs express a broad range of mRNAs encoding cytokines, chemokines, and their receptors. Using chemotaxis assays, we also assessed the functionality of the receptor expression in HuMSC and we show that CXCL12/stromal cell-derived factor-lalpha (SDF-lalpha), CX3CL1/fractalkine, and CXCL10/interferon-gamma (IFN-gamma)-inducible protein (IP-10) lead to significant HuMSC migration. Moreover, we provide evidence that tumor necrosis factor-alpha (TNF-alpha) and IFN-gamma act as major regulators of the expression of chemokines and their receptors in HuMSCs. Correspondingly, we demonstrate for the first time that current multiple sclerosis (MS) therapies, namely, IFN-beta and Copaxone, influence the expression of chemokines and their receptors in HuMSCs at both mRNA and protein levels. Administration of cytokines, including IFN-beta and Copaxone, may be important in stem cell transplantation therapies and perhaps important in the efficacy of existing MS therapies.

Human immunodeficiency virus-associated progressive multifocal leucoencephalopathy: epidemiology and predictive factors for prolonged survival

We performed a retrospective review of cases of human immunodeficiency virus-associated progressive multifocal leucoencephalopathy in four hospitals (three in Australia and one in Hong Kong) between 1987 and 2003 in order to describe the local experience with this disease and to evaluate parameters impacting upon survival. Eighty-seven cases were identified and demographic details, baseline parameters and treatment methods and response were described. Survival was substantially increased in the post-highly active antiretroviral therapy (HAART) era with a median survival increase from 14 to 64 weeks. On multivariate analysis, variables associated with prolonged survival included a CD4 count of >100 cells/mul at diagnosis and the use of HAART post-diagnosis, with no significant additional advantage from the use of neuroactive antiretrovirals.

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.

Neural transplantation of human MSC and NT2 cells in the twitcher mouse model

BACKGROUND

Accumulating evidence has demonstrated that the NT2 embryonal carcinoma cell line and multipotential stem cells found in BM, mesenchymal stromal cells (MSC), have the ability to differentiate into a wide variety of cell types. This study was designed to explore the efficacy of these two human stem cell types as a graft source for the treatment of demyelinating disorders such as Krabbe's disease and multiple sclerosis (MS).

METHODS

We examined the engraftment and in vivo differentiation of adult MSC and NT2 cells after transplantation into two demyelinating environments, the neonatal and postnatal twitcher mouse brain.

RESULTS

Both types of xenografts led to anatomical integration, without tumor formation, and remained viable in the normal and twitcher mouse brain, showing differentiation into neurons, astrocytes and oligodendrocytes.

DISCUSSION

This study represents a platform for further stem cell transplantation studies in the twitcher model and potentially has important therapeutic implications.

Valproic acid is associated with cognitive decline in HIV-infected individuals: a clinical observational study

Background

Valproic acid (VPA) is often used to control pain in HIV-related neuropathy. However, the effect of VPA on cognitive functions in advanced HIV-infected individuals is largely unknown. A recent study would suggest that it may have a neuroprotective effect, the doses used were low and the observation period short.

Methods

We used a well studied HIV-infected cohort assessed for a median of 15 (range 6–27 months) to determine whether individuals who were receiving VPA showed any cognitive benefits. Multiple regression procedures allowed us to control for the effects of HAART and HIV disease status as well as numbers of visits and variation in VPA intake over-time.

Results

We found a negative effect of VPA (mean dose of 850 mg/d for 18 months on average; range 6–27 months) on cognitive performance in eight advanced HIV-infected individuals compared to 32 advanced HIV-infected individuals on no VPA who had comparable neuropsychological performance at baseline. Control for plasma HIV viral load provided similar results.

Conclusion

Our results suggest that further studies of VPA in advanced HIV-infection should cautiously include high doses over prolonged periods of at least 18 months in order to more accurately determine whether the posited neuroprotective benefit of VPA still occurs or whether it is replaced by toxicity.

Transcriptional activity of blood-and cerebrospinal fluid-derived nef/long-terminal repeat sequences isolated from a slow progressor infected with nef-deleted human immunodeficiency virus type 1 (HIV-1) who developed HIV-associated dementia

The authors studied the transcriptional activity of blood-and cerebrospinal fluid (CSF)-derived nef/long-terminal repeat (LTR) sequences isolated from a slow progressor infected with nef-deleted human immunodeficiency virus type 1 (HIV-1) who developed HIV-associated dementia (HIVD). The transcriptional activity of CSF-derived nef/LTR clones isolated during HIVD was up to 4.5-fold higher than blood-derived clones isolated before and during HIVD when tested under basal, phorbol 12-myristate 13-acetate-(PMA-), and Tat-activated conditions, and was associated with the presence of duplicated nuclear factor (NF)-kappaB and specificity factor-1 (Sp-1) binding sites coupled with a truncated nef sequence, increased replication capacity, and high CSF viral load. Thus, nef and LTR mutations that augment transcription may contribute to neuropathogenesis of nef-deleted HIV-1.

Implications for the kynurenine pathway and quinolinic acid in amyotrophic lateral sclerosis

The kynurenine pathway (KP) is a major route of L-tryptophan catabolism leading to production of several neurobiologically active molecules. Among them is the excitotoxin quinolinic acid (QUIN) that is known to be involved in the pathogenesis of several major inflammatory neurological diseases. In amyotrophic lateral sclerosis (ALS) degeneration of motor neurons is associated with a chronic and local inflammation (presence of activated microglia and astrocytes). There is emerging evidence that the KP is important in ALS. Recently, we demonstrated that QUIN is significantly increased in serum and CSF of ALS patients. Moreover, most of the factors associated with QUIN toxicity are found in ALS, implying that QUIN may play a substantial role in the neuropathogenesis of ALS. This review details the potential role the KP has in ALS and advances a testable hypothetical model.

Defining and evaluating HIV-related neurodegenerative disease and its treatment targets: a combinatorial approach to use of cerebrospinal fluid molecular biomarkers

There are a number of reasons that the accomplishments of clinical trials related to HIV-related neurodegenerative disease (HRND) and the AIDS dementia complex (ADC) have had such limited impact on clinical practice. These include: rapid evolution and progress in the treatment of systemic HIV infection that has quickly outpaced neurological efforts and has markedly reduced disease incidence; ethical constraints that (rightly) demand neurologically compromised patients receive the best available treatment before experimental therapeutics; complicated backgrounds and comorbidities of patients now most susceptible to HRND; and reluctance of general AIDS clinicians and drug companies to look beyond systemic or pivotal outcomes. However, the field has also been slow to adopt methods that better exploit advances in understanding of the pathogenesis of central nervous system (CNS) infection and brain injury, and that might circumvent some of these constraints. Using a simple model of pathogenesis, we propose an approach to characterizing patients, selecting treatment targets, and evaluating outcomes that emphasize a combination of cerebrospinal fluid (CSF) markers. This model begins by using three markers related to cardinal components of HRND: CNS HIV infection (measurement of CSF HIV RNA), intrathecal immunoactivation (CSF neopterin), and brain injury [CSF light chain neurofilament (NFL)]. Careful analysis of this and other marker combinations promises more rational trial design and more rapid progress in managing CNS HIV infection and HRND using both antiviral and adjuvant treatment approaches.

Variable benefit in neuropsychological function in HIV-infected HAART-treated patients

The authors examined cognitive performance change in 101 individuals with advanced HIV infection on highly active antiretroviral therapy (HAART), using standard neuropsychological testing in three visits, over a 27-month-period. Cognitive performance stabilized in a majority of HIV+ participants over time. A neuroactive HAART regimen was associated with neuropsychological improvement. Decline occurred in a minority with lower nadir CD4. The current CD4 count and plasma viral load were not associated with cognitive change.

The neuropsychological profile of symptomatic AIDS and ADC patients in the pre-HAART era: a meta-analysis

It remains essential to document the neuropsychological profile of acquired immunodeficiency syndrome (AIDS) dementia complex (ADC) and minor forms human immunodeficiency virus (HIV)-associated neurocognitive impairment by quantifying the magnitude of impairment across eras of treatment. Indeed, with the introduction of the highly active antiretroviral therapy (HAART), there is evidence of changes in aspects of ADC. To allow quantitative and qualitative comparisons with the HAART era studies, we developed a summary of neuropsychological performance acquired in pre-HAART era studies in advanced HIV infection and ADC. Using a meta-analytical procedure and a test nomenclature that accounts for task complexity, we found that individuals with symptomatic infection (but no AIDS) demonstrated a global mild level of cognitive impairment, except for the domains complex attention/psychomotor speed, motor coordination, and learning, which showed moderate impairment. Individuals with AIDS demonstrated a global moderate level of cognitive impairment with a predominance of deficits in attention, complex attention/psychomotor speed, learning, motor coordination, with additional deficits in verbal memory and reasoning. Individuals with ADC demonstrated the most severe cognitive disturbances in domains of learning, motor coordination, with additional deficits in veibal fluency and verbal memory. Moderate impairment was evidenced in domains of complex attention/psychomotor speed, whereas naming and visuospatial functions were relatively preserved. The profile of deficits in ADC suggests that it may not be only interpreted as a worsening form of the impairment that is seen in the AIDS and symptomatic stages of HIV disease but that there are also additional deficits suggestive of an alternate pathogenetic process(es).

CSF amyloid beta42 and tau levels correlate with AIDS dementia complex

There is concern that AIDS dementia complex (ADC) may be complicated by Alzheimer disease (AD). Because AD presence and risk are related to CSF beta-amyloid(1-42) (Abeta42), total tau (t-tau), and phosphorylated tau (p-tau), the authors examined these in ADC, AD, and controls. ADC had significantly decreased CSF Abeta42 and increased t-tau and p-tau concentrations similar to AD, suggesting that ADC may be associated with AD or an AD-like process.

Env gp120 sequence analysis of HIV type 1 strains from diverse areas of the brain shows preponderance of CCR5 usage

In this study diverse areas of the autopsied brain of 12 HIV-infected patients with and without dementia were analyzed. All brain samples were obtained at autopsy through prior consent. Env C2-V5 region was PCR amplified and sequenced and compared between different brain regions within the same patient and also between patients to find changes, which can discriminate between patients with and without dementia and also identify motifs responsible for coreceptor-mediated entry of HIV into the CNS. For this, the Env gp120 hypervariable V3 region (35 amino acid residues) was subjected to position scoring matrix analyses (PSSM) for predicting coreceptor usage in the brain. These predictions based on the V3 loop sequence were absolutely consistent with the biologically determined viral phenotype at least for the samples, which were successful for virus culture. These data clearly show that the PSSM correlates can be unambiguously applied in determining viral phenotype for entry. The most notable observation is that of 69 V3 region sequences analyzed from 12 patients from diverse brain regions, 64 showed CCR5 usage (93%) as opposed to only five using CXCR4. Comparison of the V3 loop charge failed to show any correlation between charge and coreceptor usage. Given that cells of macrophage lineage predominate in the CNS and also facilitate HIV entry into the CNS, the preponderance of CCR5 usage in brain-derived HIV strains from patients with and without dementia may have important clinical implications.

Undifferentiated mouse mesenchymal stem cells spontaneously express neural and stem cell markers Oct-4 and Rex-1

BACKGROUND

Previous adult stem cells studies have provided evidence that BM mesenchymal stem cells (MSC) exhibit multilineage differentiation capacity. These properties of MSC prompted us to explore the neural potential of MSC with a view to their use for the treatment of demyelinating disorders, such as multiple sclerosis. Indeed, issues such as the identification of a subset of stem cells that is neurally fated, methods of expansion and optimal stage of differentiation for transplantation remain poorly understood.

METHODS

In order to isolate mouse (m) MSC from BM, we used and compared the classic plastic-adhesion method and one depleting technique, the magnetic-activated cell sorting technique.

RESULTS

We established and optimized culture conditions so that mMSC could be expanded for more than 360 days and 50 passages. We also demonstrated that undifferentiated mMSC express the neural markers nestin, MAP2, A2B5, GFAP, MBP, CNPase, GalC, O1 under standard culture conditions before transplantation. The pluripotent stem cell marker Oct-4 and the embryonic stem cell marker Rex-1 are spontaneously expressed by untreated mMSC. The lineage-negative mMSC (CD5- CD11b- Ly-6G- Ter119- CD45R- c-kit/CD117-) overexpressed Oct-4, O1 and A2B5 in the first days of culture compared with the non-sorted MSC. Finally, we identified a distinct subpopulation of mMSC that is primed towards a neural fate, namely Sca-1+/nestin+ mMSC.

DISCUSSION

These results should facilitate the optimal timing of harvesting a neurally fated subpopulation of mMSC for transplantation into animal models of human brain diseases.

The assessment of cognitive function in advanced HIV-1 infection and AIDS dementia complex using a new computerised cognitive test battery

The validity of a new computerised battery called CogState was determined in 60 individuals with advanced human immunodeficiency virus-1 (HIV-1) infection from which eleven were assessed as AIDS dementia complex (ADC) stage 1 or 2. Twenty-one seronegative individuals were recruited as controls. Participants were evaluated with a brief computerised examination, lasting 10-15 min, assessing reaction time, accuracy in working memory and learning. They were also assessed with a standard neuropsychological examination lasting 1h 30 min on average. The computerised assessment demonstrated a good sensitivity of 81.1% and specificity of 69.9% as well as good positive predictive value (81%) and acceptable construct validity (.45-.62). Slowed reaction time and learning deficits in the computerised battery were characteristic of ADC. This study supports the utility of a brief computerised battery in the detection of HIV-associated neurocognitive impairment that could be used for wide-scale screening.

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.

Indoleamine 2,3 dioxygenase and quinolinic acid immunoreactivity in Alzheimer's disease hippocampus

The present immunohistochemical study provides evidence that the kynurenine pathway is up-regulated in Alzheimer's disease (AD) brain, leading to increases in the excitotoxin quinolinic acid (QUIN). We show that the regulatory enzyme of the pathway leading to QUIN synthesis, indoleamine 2,3 dioxygenase (IDO) is abundant in AD compared with controls. In AD hippocampus, both IDO- and QUIN-immunoreactivity (-IR) was detected in cortical microglia, astrocytes and neurones, with microglial and astrocytic expression of IDO and QUIN highest in the perimeter of senile plaques. QUIN-IR was present in granular deposits within the neuronal soma of AD cortex and was also seen uniformly labelling neurofibrillary tangles. Our data imply that QUIN may be involved in the complex and multifactorial cascade leading to neuro-degeneration in AD. These results may open a new therapeutic door for AD patients.

Undetectable Cerebrospinal Fluid HIV RNA and β-2 Microglobulin Do Not Indicate Inactive AIDS Dementia Complex in Highly Active Antiretroviral Therapy-Treated Patients

OBJECTIVE

To assess whether nonelevated cerebrospinal fluid (CSF) markers could delineate inactive AIDS dementia complex (ADC) in patients receiving highly active antiretroviral therapy (HAART), using neuropsychologic performance change as an indicator of ADC stability.

METHODS

We used data from the abacavir (ABC) ADC trial (n = 78) and examined the patients' neuropsychologic performance change with the Reliable Change Index according to 3 cutoff groups: (1) CSF viral load (VL) <100 copies/mL, (2) CSF beta-2 microglobulin (beta2m) <2.2 mg/L, and (3) CSF VL and CSF beta2m below cutoffs.

RESULTS

CSF marker cutoff groups did not define neuropsychologic change. Linear regression showed that only CSF VL was a weak predictor of neuropsychologic performance change.

CONCLUSION

HAART-treated ADC patients with baseline CSF markers of viral and immunologic inactivity did not necessarily have inactive ADC when followed over 12 weeks. More sensitive CSF markers to judge the activity of ADC are urgently needed, whereas the interpretation of these markers should be considered with caution in HAART-treated ADC patients.

Quinolinic acid selectively induces apoptosis of human astrocytes: potential role in AIDS dementia complex

There is evidence that the kynurenine pathway (KP) and particularly one of its end products, quinolinic acid (QUIN) play a role in the pathogenesis of several major neuroinflammatory diseases, and more particularly AIDS dementia complex (ADC). We hypothesized that QUIN may be involved in astrocyte apoptosis because: 1) apoptotic astrocytes have been observed in the brains of ADC patients, 2) ADC patients have elevated cerebrospinal fluid QUIN concentrations, and 3) QUIN can induce astrocyte death. Primary cultures of human fetal astrocytes were treated with three pathophysiological concentrations of QUIN. Numeration of apoptotic cells was assessed using double immunocytochemistry for expression of active caspase 3 and for nucleus condensation. We found that treatment of human astrocytes with QUIN induced morphological (cell body shrinking) and biochemical changes (nucleus condensation and over-expression of active caspase 3) of apoptosis. After 24 hours of treatment with QUIN 500 nM and 1200 nM respectively 10 and 14% of astrocytes were undergoing apoptosis. This would be expected to lead to a relative lack of trophic support factors with consequent neuronal dysfunction and possibly death. Astroglial apoptosis induced by QUIN provides another potential mechanism for the neurotoxicity of QUIN during ADC.

Prevalence and pattern of neuropsychological impairment in human immunodeficiency virus-infected/acquired immunodeficiency syndrome (HIV/AIDS) patients across pre- and post-highly active antiretroviral therapy eras: a combined study of two cohorts

The objective of this study was to assess the prevalence and pattern of neuropsychological impairment in cohorts of human immunodeficiency virus (HIV)-infected individuals across pre- and post-HAART (highly active antiretroviral therapy) eras. Two cohorts of HIV-infected individuals attending tertiary referral hospital outpatient clinics were studied. The cohorts represented two eras of antiretroviral medication: monotherapy (n = 51) and HAART (n = 90). Each was compared in nine neuropsychological domains in regard to the prevalence as well as pattern of neuropsychological impairment. Because the authors intended to characterize the prevalence and pattern of neuropsychological deficits in nondemented advanced HIV-infected individuals, patients with a current diagnosis of acquired immunodeficiency syndrome (AIDS) dementia complex were not included. The prevalence of impairment was not significantly different across pre-HAART and HAART eras using a standard criterion to define impairment: -2 SD in two neuropsychological measures (41.1%/38.8%). Prevalence of deficits was not significantly reduced in patients with undetectable plasma viral load. The pattern of neuropsychological impairment was different across pre-HAART and HAART eras, with an improvement in attention, verbal fluency, visuoconstruction deficits, but a deterioration in learning efficiency and complex attention. This change remained even in patients with an undetectable plasma viral load, although the severity was partially diminished. Neuropsychological deficits remain common in the HAART era, essentially uninfluenced by HAART. The finding that some neuropsychological functions are improving while other are deteriorating indicates that these deficits do not reflect "burnt out" damage but rather that there is an active intracerebral process occurring, the nature of which is still to be determined.

Involvement of quinolinic acid in AIDS dementia complex

Human immunodeficiency virus (HIV) infection is often complicated by the development of acquired immunodeficiency syndrome (AIDS) dementia complex (ADC). Quinolinic acid (QUIN) is an end product of tryptophan, metabolized through the kynurenine pathway (KP) that can act as an endogenous brain excitotoxin when produced and released by activated macrophages/microglia, the very cells that are prominent in the pathogenesis of ADC. This review examines QUIN's involvement in the features of ADC and its role in pathogenesis. We then synthesize these findings into a hypothetical model for the role played by QUIN in ADC, and discuss the implications of this model for ADC and other inflammatory brain diseases.

Longitudinal Analysis ofnef/Long Terminal Repeat–Deleted HIV‐1 in Blood and Cerebrospinal Fluid of a Long‐Term Survivor Who Developed HIV‐Associated Dementia

We studied the evolution and compartmentalization of nef/long terminal repeat (nef/LTR)-deleted human immunodeficiency virus type 1 (HIV-1) from a long-term survivor who developed HIV-associated dementia (HIVD). Analysis of sequential blood-derived HIV-1 isolated before and during HIVD revealed a persistent R5X4 phenotype and a progressive loss of nef/LTR sequence; in contrast, HIV-1 present in cerebrospinal fluid during HIVD had an R5 phenotype, distinct nef/LTR sequence of unique deletions and additional nuclear factor- kappa B sites and specificity factor-1 sites, and enhanced transcriptional activity, compared with the blood-derived isolates. Thus, nef/LTR-deleted HIV-1 strains may undergo compartmentalized evolution in long-term survivors and cause neurologic disease.

Antiretroviral Therapy in HIV Infection

BACKGROUND

The effect on neuropsychological function of antiretroviral drugs that are able to penetrate into the brain in effective concentration (neuroactive drugs) remains unclear.

OBJECTIVE

To investigate whether highly active antiretroviral therapy (HAART) containing neuroactive drugs is associated with better neuropsychological performance in patients with human immunodeficiency virus disease.

DESIGN

Cross-sectional survey.

SETTING

Tertiary referral hospital outpatient clinics.

PATIENTS

The study population consisted of 97 individuals positive for human immunodeficiency virus (stage C3, 1993 Centers for Disease Control and Prevention classification) whose condition had been stable on their current HAART regimen for a mean +/- SD of 18.5 +/- 16.5 months and who were aged 48.14 +/- 9.38 years. The patient groups were analyzed according to whether their regimen contained 3 or more neuroactive drugs (neuroHAART group; n = 41) or not (HAART group; n = 56). Thirty seronegative men matched for age and education were recruited as controls.

MAIN OUTCOME MEASURE

Neuropsychological performance on 7 cognitive domains.

RESULTS

The neuroHAART and HAART groups did not differ from one another on neuropsychological performance, but both patient groups were impaired compared with controls. Impaired patients in each treatment group were compared, and the neuroHAART group showed significantly better memory performance, unrelated to plasma viral load, than the HAART group.

CONCLUSION

No direct benefit of neuroactive HAART therapy was found in patients with advanced human immunodeficiency virus infection. However, in neuropsychologically impaired patients, there was a benefit in memory function. This suggests that a threshold of neuropsychological impairment is required for the benefit of neuroactive HAART.

Independent evolution of human immunodeficiency virus (HIV) drug resistance mutations in diverse areas of the brain in HIV-infected patients, with and without dementia, on antiretroviral treatment

AIDS dementia complex (ADC) in human immunodeficiency virus (HIV)-infected patients continues to be a problem in the era of highly active antiretroviral therapy (HAART). A better understanding of the drug resistance mutation patterns that emerge in the central nervous system (CNS) during HAART is of paramount importance as these differences in drug resistance mutations may explain underlying reasons for poor penetration of antiretroviral drugs into the CNS and suboptimal concentrations of the drugs that may reside in the brains of HIV-infected individuals during therapy. Thus, we provide a detailed analysis of HIV type 1 (HIV-1) protease and reverse transcriptase (RT) genes derived from different regions of the brains of 20 HIV-1-infected patients (5 without ADC, 2 with probable ADC, and 13 with various stages of ADC) on antiretroviral therapy. We show the compartmentalization and independent evolution of both primary and secondary drug resistance mutations to both RT and protease inhibitors in diverse regions of the CNS of HIV-infected patients, with and without dementia, on antiretroviral therapy. Our results suggest that the independent evolution of drug resistance mutations in diverse areas of the CNS may emerge as a consequence of incomplete suppression of HIV, probably related to suboptimal drug levels in the CNS and drug selection pressure. The emergence of resistant virus in the CNS may have considerable influence on the outcome of neurologic disease and also the reseeding of HIV in the systemic circulation upon failure of therapy.

Expression of the kynurenine pathway enzymes in human microglia and macrophages

There is good evidence that the kynurenine pathway (KP) and one of its products, quinolinic acid (QUIN) play a role in the pathogenesis of neurological diseases. Monocytic cells are known to be the major producers of QUIN. However, macrophages have the ability to produce approximately 20 to 30-fold more QUIN than microglia. The molecular origin of this difference has not been clarified yet. Using unstimulated and IFN-gamma-stimulated cultures of human fcetal microglia and adult macrophages, we assayed mRNA expression of 8 key enzymes of the KP using RT-PCR and QUIN production using GC-MS. We found that after stimulation with IFN-gamma microglia produced de novo 20-fold less QUIN than macrophages. This quantitative difference in the ability to produce QUIN appears to be associated with a lower expression of 3 important enzymes of the KP in microglia: indoleamine 2,3-dioxygenase (IDO), kynureninase (KYNase) and kynurenine hydroxylase (KYN(OH)ase). These results suggest that activated infiltrating macrophages are the most potent QUIN producers during brain inflammatory diseases with playing a lesser role.

A beta 1-42 induces production of quinolinic acid by human macrophages and microglia

We hypothesized that the tryptophan catabolites produced through the kynurenine pathway (KP), and more particularly the excitotoxin quinolinic acid (QUIN), may play an important role in the pathogenesis of Alzheimer's disease (AD). In this study, we demonstrated that aggregated amyloid peptide A beta 1-42 induced indoleamine 2,3-dioxygenase (IDO) expression and resulted in a significant increase in production of QUIN by human primary macrophages and microglia. In contrast, A beta 1-40 and prion peptide (PrP) 106-126 did not induce any significant increase in QUIN production. These data imply that local QUIN production may be one of the factors involved in the pathogenesis of neuronal damage in AD.

Can the peripheral blood monocyte count be used as a marker of CSF resistance to antiretroviral drugs?

Resistance to antiretroviral drugs in human immunodeficiency virus (HIV) disease may be discordant between blood and cerebrospinal fluid (CSF). However, there is no method by which patients who are likely to harbor resistant HIV in the CSF can be noninvasively identified. Activated monocytes are known to traffic through the brain and perivascular microglia are considered to "turnover" regularly from bone marrow-derived monocytes. Monocytes lack certain kinases necessary to metabolize some antiretroviral drugs, making it possible that monocytes, could deliver antiretroviral drugs to the brain. Low monocyte counts in the peripheral blood, however, would be expected to lead to decreased trafficking and turnover of monocytes, with less drug delivery to the brain. The authors hypothesized that this would increase the likelihood of drug resistant HIV in the central nervous system. To test this, 24 matching CSF and plasma samples that had been prospectively collected and stored from patients treated with nucleoside analogue reverse transcriptase inhibitor drugs were assessed for genotypic resistance. Those CSFs, with evidence of resistance mutations, were compared to those without for peripheral blood monocyte count, hemoglobin, CD4 cell count, and zidovudine (ZDV) use. The same analyses were repeated on the plasma samples. There were 11 CSFs with evidence of resistance mutations. The peripheral blood monocyte count was significantly lower in the CSF resistant group (0.29 +/- 0.16) versus (0.52 +/- 0.21) x 10(9)/L (P <.001). There was no difference between the groups according to hemoglobin, CD4 cell count, total white cell count, or use of ZDV. There was no difference between resistant and sensitive plasma samples according to peripheral blood monocyte count. To further test the hypothesis, the authors determined the concentrations of ZDV, stavudine, and abacavir in monocytes after each drug had been added to monocyte cultures. There was a significant decline in the concentration of each drug in the supernatant, implying that it had been "taken up" by the monocytes. These preliminary data suggest that peripheral blood monocytes may be important in delivery of antiretroviral drugs to the brain and the development of resistance.

Human immunodeficiency virus-related primary central nervous system lymphoma

BACKGROUND

The current study evaluated factors influencing survival in patients diagnosed with human immunodeficiency virus (HIV)-related primary central nervous system lymphoma (PCNSL), with a focus on the effects of therapeutic radiotherapy (RT) and highly active antiretroviral therapy (HAART).

METHODS

A retrospective chart review of patients with a diagnosis of HIV-related PCNSL at one of five university hospitals between 1987 and 1998 was performed. Clinical details including antiretroviral agent use, brain imaging scan results, RT use, and survival outcomes were recorded.

RESULTS

One hundred eleven patients with HIV-related PCNSL were identified. The annual incidence decreased significantly between 1992 and 1995 and between 1996 and 1998 (P = 0.04). The median survival period was 50 days (mean, 109 days; range, 4-991 days), with improved survival for patients diagnosed after 1993. Patients treated with two or more antiretroviral agents had improved survival (P = 0.01), as did patients who received RT (P < 0.0001). For patients who received RT, completion of the prescribed course and treatment to > or = 30 Gray (Gy) independently predicted a more favorable outcome. RT used in conjunction with antiretroviral therapy involving two or more agents had an additive positive effect on survival. For patients who did not receive RT, poor performance status and encephalopathy predicted a shorter survival duration.

CONCLUSIONS

The results of the current study suggest that HAART and treatment with RT to > or = 30 Gy improve survival for patients with HIV-related PCNSL. This combination of therapies may provide a standard of care as the basis for further trials of chemotherapy, novel adjunctive treatment, and quality of life assessment.

Evidence for a change in AIDS dementia complex in the era of highly active antiretroviral therapy and the possibility of new forms of AIDS dementia complex

This review will discuss emerging evidence for the possibility that AIDS dementia complex (ADC) has changed in the era of highly active antiretroviral therapy (HAART). The consequences of not considering these possibilities at the patient level and at the level of research are considerable. Data will be discussed that are derived from epidemiological studies, neuropsychological and positron emission tomography studies, as well as analyses from the abacavir ADC trial. These will then be assessed to develop the concept that there are now different forms of ADC: an inactive form, a chronic variety and a 'transformed' variant. Whereas the latter relates to the compounding influence of a number of other processes on ADC, such as hepatitis C, particular discussion will focus upon Alzheimer's disease and whether HIV may lead to Alzheimer-like changes. It is certainly recognized that some of the concepts discussed here are highly speculative.

Expression of indoleamine 2,3-dioxygenase and production of quinolinic acid by human microglia, astrocytes, and neurons

There is good evidence that the kynurenine pathway (KP) and one of its end products, quinolinic acid (QUIN) play a role in the pathogenesis of several major neurological diseases. While QUIN has been shown to be produced in neurotoxic concentrations by macrophages and microglia, the capacity of astrocytes and neurons to produce QUIN is controversial. Using interferon gamma (IFN-gamma)-stimulated primary cultures of human mixed brain cells, we assayed expression of the KP regulatory enzyme indoleamine 2,3-dioxygenase (IDO) and QUIN production by immunocytochemistry. Using IFN-gamma-stimulated purified cultures of neurons, astrocytes, microglia and macrophages, we studied IDO expression by RT-PCR and production of QUIN using mass spectrometry. We found that astrocytes, neurons, and microglia expressed IDO but only microglia were able to produce detectable amounts of QUIN. However, astrocytes and neurons had the ability to catabolize QUIN. This study also provides the first evidence of IDO expression and lack of production of QUIN in culture of primary human neurons.

The peripheral nerve complications of human immunodeficiency virus (HIV) infection

Peripheral nerve complications occurring in patients with human immunodeficiency virus (HIV) infection are frequent and challenging. This review discusses these various complications according to the degree of advancement of HIV disease. Particular emphasis is placed upon emerging causes of neuropathy found in the context of HIV disease, such as infection with hepatitis C and human T-lymphotropic virus type I, as well as neuropathies related to antiretroviral medications.

Microglia, macrophages, perivascular macrophages, and pericytes: a review of function and identification

The phenotypic differentiation of systemic macrophages that have infiltrated the central nervous system, pericytes, perivascular macrophages, and the "real" resident microglial cells is a major immunocytochemical and immunohistochemical concern for all users of cultures of brain cells and brain sections. It is not only important in assessing the purity of cell cultures; it is also of fundamental importance in the assessment of the pathogenetic significance of perivascular inflammatory phenomena within the brain. The lack of a single membranous and/or biochemical marker allowing conclusive identification of these cells is still a major problem in neurobiology. This review briefly discusses the functions of these cells and catalogs a large number of membranous and biochemical markers, which can assist in the identification of these cells.

Marked improvement in survival following AIDS dementia complex in the era of highly active antiretroviral therapy

OBJECTIVE

To determine the effect of introduction of highly active antiretroviral therapy (HAART) on survival following AIDS dementia complex (ADC).

METHODS

Australian AIDS notification data in the period 1993-2000 were examined. In order to examine the impact of HAART, two periods of AIDS diagnoses were chosen: pre-HAART (1993-1995) and HAART (1996-2000). Median survival was based on Kaplan-Meier estimates, with examination of factors influencing survival in a Cox proportional hazards model.

RESULTS

In the period 1993-2000 in Australia, 5017 initial AIDS illnesses were diagnosed among 4351 AIDS patients. The proportion of AIDS cases with ADC increased from 5.2% in 1993-1995 to 6.8% in 1996-2000 (P = 0.029). Median survival following AIDS increased from 19.6 months for those diagnosed with AIDS in 1993-1995 to 39.6 months for those diagnosed in 1996-2000 (P < 0.0005). Median survival following ADC increased to a greater extent than that for all other AIDS illnesses, from 11.9 months in 1993-1995 to 48.2 in 1996-2000 (P < 0.0005). Most striking was the increase in survival among those with ADC and a CD4 cell count < 100 x 10(6) cells/l at diagnosis; 5.1 months in 1993-1995 to 38.5 months in 1996-2000 (P < 0.0005).

CONCLUSION

Although there has been a proportional increase in ADC at AIDS diagnosis, survival following ADC has improved markedly in the era of HAART.

Lactate concentrations distinguish between nucleoside neuropathy and HIV neuropathy

We prospectively assessed serum lactate and plasma HIV viral load in 20 patients with stavudine-related nucleoside neuropathy, 10 with HIV-related distal sensory polyneuropathy (DSPN), 20 receiving stavudine but without neuropathy and 23 not receiving stavudine and without neuropathy. Raised serum lactate levels discriminated between stavudine nucleoside neuropathy and DSPN with 90% sensitivity and 90% specificity (P = 0.001). DSPN occurred despite an undetectable viral load, making it a poor discriminator.

Implications of the kynurenine pathway and quinolinic acid in Alzheimer's disease

The kynurenine pathway (KP) is a major route of L-tryptophan catabolism leading to production of a number of biologically active molecules. Among them, the neurotoxin quinolinic acid (QUIN), is considered to be involved in the pathogenesis of a number of inflammatory neurological diseases. Alzheimer's disease is the major dementing disorder of the elderly that affects over 20 million peoples world-wide. Most of the approaches to explain the pathogenesis of Alzheimer's disease focus on the accumulation of amyloid beta peptide (A beta), in the form of insoluble deposits leading to formation of senile plaques, and on the formation of neurofibrillary tangles composed of hyperphosphorylated Tau protein. Accumulation of A beta is believed to be an early and critical step in the neuropathogenesis of Alzheimer's disease. There is now evidence for the KP being associated with Alzheimer's disease. Disturbances of the KP have already been described in Alzheimer's disease. Recently, we demonstrated that A beta 1-42, a cleavage product of amyloid precursor protein, induces production of QUIN, in neurotoxic concentrations, by macrophages and, more importantly, microglia. Senile plaques in Alzheimer's disease are associated with evidence of chronic local inflammation (especially activated microglia) A major aspect of QUIN toxicity is lipid peroxidation and markers of lipid peroxidation are found in Alzheimer's disease. Together, these data imply that QUIN may be one of the critical factors in the pathogenesis of neuronal damage in Alzheimer's disease. This review describes the multiple correlations between the KP and the neuropathogenesis of Alzheimer's disease and highlights more particularly the aspects of QUIN neurotoxicity, emphasizing its roles in lipid peroxidation and the amplification of the local inflammation.

Expression of chemokines and their receptors in human and simian astrocytes: evidence for a central role of TNF alpha and IFN gamma in CXCR4 and CCR5 modulation

Chemokines are key mediators of the selective migration of leukocytes that occurs in neurodegenerative diseases and related inflammatory processes. Astrocytes, the most abundant cell type in the CNS, have an active role in brain inflammation. To ascertain the role of astrocytes during neuropathological processes, we have investigated in two models of primary cells (human fetal and simian adult astrocytes) the repertoire of chemokines and their receptors expressed in response to inflammatory stimuli. We demonstrated that, in the absence of any stimulation, human fetal and simian adult astrocytes express mRNA for receptors APJ, BOB/GPR15, Bonzo/CXCR6, CCR2, CCR3, CCR5, CCR8, ChemR23, CXCR3/GPR9, CXCR4, GPR1, and V28/CX3CR1. Moreover, TNFalpha and IL-1beta significantly increase BOB/GPR15, CCR2, and V28/CX3CR1 mRNA levels in both models. Furthermore, TNFalpha and IFNgamma act synergistically to induce expression of the major coreceptors for HIV infection, CXCR4 and CCR5, at both the mRNA and protein levels in human and simian astrocytes, whereas CCR3 expression was not affected by cytokine treatment. Finally, TNFalpha/IFNgamma was the most significant cytokine combination in leading to a pronounced upregulation in a comparable, time-dependent manner of the production of chemokines IP-10/CXCL10, RANTES/CCL5, MIG/CXCL9, MCP-1/CCL2, and IL-8/CXCL8. In summary, these data suggest that astrocytes serve as an important source of chemokines under the dependence of a complex cytokine regulation, and TNFalpha and IFNgamma are important modulators of chemokines and chemokine receptor expression in human as well as simian astrocytes. Finally, with the conditions we used, there was no difference between species or age of tissue.

Quinolinic acid upregulates chemokine production and chemokine receptor expression in astrocytes

Within the brain, quinolinic acid (QUIN) is an important neurotoxin, especially in AIDS dementia complex (ADC). Its production by monocytic lineage cells is increased in the context of inflammation. However, it is not known whether QUIN promotes inflammation. Astrocytes are important in immunoregulation within the brain and so we chose to examine the effects of QUIN on the astrocyte. Using purified primary human fetal astrocyte cultures, we determined chemokine production using ELISA assays and RT-PCR and chemokine receptor expression using immunocytochemistry and RT-PCR with QUIN in comparison to TNFalpha, IL-1beta, and IFNgamma. We found that QUIN induces astrocytes to produce large quantities of MCP-1 (CCL2) and lesser amounts of RANTES (CCL5) and IL-8 (CXCL8). QUIN also increases SDF-1alpha (CXCL12), HuMIG (CXCL9), and fractalkine (CX(3)CL1) mRNA expression. Moreover, QUIN leads to upregulation of the chemokine receptor expression of CXCR4, CCR5, and CCR3 in human fetal astrocytes. Most of these effects were comparable to those induced by TNFalpha, IL-1beta, and IFNgamma. The present work represents the first evidence that QUIN induces chemokine and chemokine receptor expression in astrocytes and is at least as potent as classical mediators such as inflammatory cytokines. These results suggest that QUIN may be critical in the amplification of brain inflammation, particularly in ADC.

QUINOLINIC ACID IN THE PATHOGENESIS OF ALZHEIMER’S DISEASE

We propose that the tryptophan catabolites produced through the kynurenine pathway (KP), and more particularly quinolinic acid (QUIN), may play an important role in the pathogenesis of Alzheimer's disease (AD). In this study, we demonstrated that after 72 hours amyloid peptide (Abeta) 1-42 induced indoleamine 2,3-dioxygenase (IDO) expression and in a significant increase in production of QUIN by human macrophages and microglia. In contrast, Abeta11-40 and Prion peptide (PrP) 106-126 did not induce any significant increase in QUIN production. We also investigated the potential modulatory effect of QUIN and kynurenic acid (KYNA) on Abeta11-42 and Abeta1-40 aggregation. After 24 and 120 hours, we did not observe any significant difference in the level of aggregation compared to the control (Abeta alone). Abeta has been shown to induce IL1-beta mRNA expression by human foetal astrocytes and macrophages. We demonstrate that QUIN has the same effect. Interestingly, IL-1beta has been found in association with plaques in AD. All together these data imply that QUIN may be, locally, one of the factors involved in the pathogenesis of neuronal damage in AD.

Quinolinic acid up-regulates chemokine production and chemokine receptor expression in astrocytes

Within the brain, quinolinic acid (QUIN) is an important neurotoxin, especially in AIDS dementia complex (ADC). Its production by monocytic lineage cells is increased in the context of inflammation. However, it is not known whether QUIN promotes inflammation. Astrocytes are important in immuno-regulation within the brain and so we chose to examine the effects of QUIN on the astrocyte. Using purified cultures of primary human foetal astrocyte, we determined chemokine production using ELISA assays and RT-PCR, and chemokine receptor expression using immunocytochemistry and RT-PCR with QUIN in comparison to TNF-alpha/IFN-gamma. We found that QUIN induces astrocytes to produce large quantities of MCP-1 (CCL2), and lesser amounts of RANTES (CCL5), IL-8 (CXCL8). QUIN also increases SDF-1alpha (CXCL12), HuMIG (CXCL9) and fractalkine (CX3CL1) mRNA expression. Moreover, QUIN leads to up-regulation of the chemokine receptor expression of CXCR4, CCR5, and CCR3 in human foetal astrocytes. Most of these effects were comparable to those induced by TNF-alpha/IFN-gamma. The present work represents the first evidence that QUIN induces chemokine and chemokine receptor expression in astrocytes and is at least as potent as classical mediators such as inflammatory cytokines. These results suggest that QUIN may be critical in the amplification of brain inflammation particularly in ADC.

Concurrent quantification of quinolinic, picolinic, and nicotinic acids using electron-capture negative-ion gas chromatography-mass spectrometry

Quinolinic, picolinic, and nicotinic acids and nicotinamide are end products of the kynurenine pathway from l-tryptophan and are intermediates in the biosynthesis of nicotinamide adenine dinucleotide. These compounds are involved in complex interrelationships with inflammatory and apoptotic responses associated with neuronal cell damage and death in the central nervous system. To facilitate the study of these compounds, we have utilized gas chromatography-mass spectrometry in electron capture negative ionization mode for their concurrent trace quantification in a single sample. Deuterium-labeled quinolinic, picolinic, and nicotinic acids were used as internal standards and the compounds were converted to their hexafluoroisopropyl esters prior to chromatography. Nicotinamide was readily quantified after conversion to nicotinic acid using gas-phase hydrolysis-a process which did not affect the deuterated internal standards. The on-column limit of quantification was less than 1 fmol for each of the analytes and calibration curves were linear. A packed column liner was used in the gas chromatograph inlet to effectively eliminate sample interference effects in the analysis of trace (femtomolar) levels of quinolinic acid. The method enables rapid and specific concurrent quantification of quinolinic, picolinic, and nicotinic acids in tissue extracts and physiological and culture media.

Treatment of opportunistic infections and lymphoma in the nervous system

The advent of highly active antiretroviral therapy has affected many aspects of the management of AIDS-related opportunistic infections (OIs). Aspects of treating OIs of the brain, spinal cord, peripheral nerves and muscles are discussed, with emphasis on more recent developments in this area. Treatment for primary and metastatic central nervous system lymphoma is also reviewed.

IFN-beta1b induces kynurenine pathway metabolism in human macrophages: potential implications for multiple sclerosis treatment

Interferon-beta(1b) (IFN-beta(1b)) has limited efficacy in the treatment of relapsing-remitting multiple sclerosis (RRMS). The kynurenine pathway (KP) is chiefly activated by IFN-gamma and IFN-alpha, leading to the production of a variety of neurotoxins. We sought to determine whether IFN-beta(1b) induces the KP in human monocyte-derived macrophages, as one explanation for its limited efficacy. Serial dilutions of IFN-beta(1b) (at concentrations comparable to those found in the sera of IFN-beta(1b)-treated patients) were added to human macrophage cultures. Supernatants were collected at various time points and assayed for the KP end product, quinolinic acid (QUIN). The effect of IFN-beta(1b) on the KP enzymes indoleamine 2,3-dioxygenase (IDO), 3-hydroxyanthranilate dioxygenase (3HAO), and quinolinate phosphoribosyltransferase (QPRTase) mRNA expression was assessed by semiquantitative RT-PCR. IFN-beta(1b) (> or =10 IU/ml) led to increased mRNA expression of both IDO and QUIN production (7901 +/- 715 nM) after 72 h at 50 IU/ml IFN-beta(1b) (p < 0.0001). This study demonstrates that IFN-beta(1b), in pharmacologically relevant concentrations, induces KP metabolism in human macrophages and may be a limiting factor in its efficacy in the treatment of MS. Inhibitors of the KP may be able to augment the efficacy of IFN-beta in MS.

Cerebrospinal fluid S-100beta and its relationship with AIDS dementia complex

BACKGROUND

The astrocyte is thought to be important in AIDS dementia complex (ADC) pathogenesis on the basis of ADC neuropathology and cell culture models putatively because HIV can infect astrocytes leading to a compromise of their physiological detoxifying and neuronal support functions. Confirmatory in vivo data are lacking. Currently, the only widely available marker of the astrocyte is the protein S-100beta.

OBJECTIVE

The aims of this study were to determine whether cerebrospinal fluid (CSF) levels of S-100beta correlate with the presence, severity and rapidity of ADC progression.

STUDY DESIGN

Fourty nine CSF samples from HIV-1 seropositive individuals with either no ADC (ADC stage 0) or varying degrees of ADC (ADC stages 1-3) were analysed in this study. An immunoradiometric assay was used to quantify levels of S-100beta in the CSF. All individuals in this study were receiving antiretroviral therapy. In addition, individuals with ADC were grouped as either rapid ADC progressors or slow ADC progressors depending on the period of time from ADC diagnosis to death.

RESULTS

CSF S-100beta levels in individuals with either ADC stage 2 or 3 were significantly elevated compared to those with stage 0 or 1. Moreover, CSF S-100beta levels were significantly higher in individuals with rapid ADC progression compared with slow progressors.

CONCLUSIONS

This study shows that CSF S-100beta levels predict those patients in whom ADC will progress rapidly.