The relationship between ApoE, TNFA, IL1a, IL1b and IL12b genes and HIV-1-associated dementia.

OBJECTIVES: Host genetic factors implicated in AIDS dementia complex (ADC) were studied. METHODS: DNA from ADC patients (n=56), unselected HIV-seropositive patients (n=112, 171, 185 and 204) and HIV-seronegative controls (n=204, 60, 60, 96 and 624) were typed for polymorphic loci in genes encoding tumour necrosis factor (TNF)-alpha, interleukin (IL)-1alpha, IL-1beta, IL-12 and Apolipoprotein E (ApoE). Diagnosis of ADC was based on neurological symptoms, signs and neuroimaging findings with other causes of dementia excluded. Patients selected had ADC stage > or =1 and CD4 counts of <500 cells/microL. RESULTS: Allele 2 of TNFA-308 was more common in ADC patients compared to HIV-positive or HIV-negative controls (P=0.005, 0.024). No other differences between ADC patients and control groups were significant. Meta-analyses confirmed these results. CONCLUSIONS: This study suggests that TNFA-308 allele 2 or an allele in linkage disequilibrium with this locus influences ADC.

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.

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.

Kynurenine pathway inhibition reduces neurotoxicity of HIV-1-infected macrophages.

The AIDS dementia complex (ADC) is a consequence of excessive immune activation driven at least in part by systemic HIV infection and probably brain infection. Quinolinic acid (QUIN) is a neurotoxic tryptophan metabolite produced by macrophages in response to stimulation with cytokines or infection with HIV-1. Consequently it has been implicated in ADC pathogenesis. However, macrophages infected with HIV-1 synthesize numerous neurotoxic substances. Therefore we conducted experiments using human fetal brain tissue to determine the relative importance of QUIN as a neurotoxin in ADC. Human macrophages were infected with HIV-1 in vitro using a viral isolate from a demented patient. 6-Chloro-D-tryptophan, an inhibitor of QUIN biosynthesis, was added to half the macrophage cultures to block formation of QUIN. Supernatants containing QUIN (SQpos) or in which QUIN biosynthesis had been inhibited (SQneg) were then added to human fetal brain aggregate cultures. Toxicity was evaluated using lactate dehydrogenase efflux, trypan blue exclusion, immunohistochemistry, image analysis, and electron microscopy. Each technique showed a reduction of toxicity in SQneg-treated cultures. These studies confirm the significance of QUIN as a neurotoxin in ADC and suggest that neuroprotective strategies may have a place in the treatment of this disease.

Quinolinic acid production by macrophages stimulated with IFN-gamma, TNF-alpha, and IFN-alpha.

Quinolinic acid (QUIN) has been associated with several inflammatory neurologic disorders, including AIDS dementia complex (ADC). Recent studies suggest that activation of macrophages with either HIV-1 or interferon-gamma (IFN-gamma) can lead to QUIN production. However, the importance of other cytokines, especially those related to the macrophage and that are especially important in ADC pathogenesis, remains unclear. We, therefore, sought to determine the role of tumor necrosis factor-alpha (TNF-alpha) and IFN-alpha in the production of QUIN. Primary human macrophages were stimulated with two different concentrations of these cytokines alone, in combination with each other, and with IFN-gamma. QUIN concentrations in the supernatants were then measured by mass spectrometry at 24, 48, and 72 hs. Results at 72 h showed significant increases in QUIN production in the cells stimulated with IFN-gamma (10297 +/- 170 nmol/L) and also in those stimulated with IFN-alpha (3600 +/- 113 nmol/L), whereas TNF-alpha-stimulated macrophages produced low levels of QUIN (1108 +/- 23 nmol/L). Macrophages stimulated with the cytokine combinations TNF-alpha and IFN-gamma, IFN-alpha, and IFN-gamma, and TNF-alpha and IFN-alpha also resulted in increases in QUIN production (11471 +/- 77.6 nmol/L, 16656 +/- 184 nmol/L, and 3369 +/- 120.5 nmol/L, respectively). The increases in QUIN production in all of the cytokine treatments approached or exceeded in vivo concentrations of QUIN that have been shown to be neurotoxic. These data further support a role for QUIN in cytokine-mediated neuronal death in inflammatory disorders of the brain, especially ADC.