AIDS:
2 September 2005 - Volume 19 - Issue 13 - p 1351-1359
Basic Science
Enrichment of activated monocytes in cerebrospinal fluid during antiretroviral therapy
Neuenburg, Jutta K; Furlan, Scott; Bacchetti, Peter; Price, Richard W; Grant, Robert M
 Author Information
From the aGladstone Institute of Virology and Immunology, University of California, San Francisco, California, USA
bDepartment of Neurology, University of California, San Francisco, California, USA
cDepartment of Epidemiology and Biostatistics, University of California, San Francisco, California, USA.
Received 10 October, 2004
Revised 11 February, 2005
Accepted 20 April, 2005
Correspondence to J.K. Neuenburg, J. David Gladstone Institutes, 1650 Owens Street, San Francisco, CA 94158, USA. Tel: +1 415 206 4500; fax: +1 415 206 3633; e-mail: jneuenburg@gladstone.ucsf.edu
Abstract
Objectives: In HIV infection, activated monocytes are enriched in blood and in the perivascular area of the brain, especially in patients with HIV-associated dementia. Although clinical brain disease is uncommon during combination antiretroviral therapy (ART), autopsy series indicate that HIV-infected brain tissue can contain high numbers of monocytes/macrophages despite ART.
Design: We assessed activated monocytes in blood and cerebrospinal fluid (CSF) in 76 living patients on and off ART. Plasma lipids were measured because they have been associated with monocyte activation and ART.
Methods: A novel quantitative six-color flow cytometric approach was used to identify monocytes in blood and CSF and to evaluate monocyte activation status.
Results: The mean percentage and number of activated CD16 monocytes in CSF was highest in individuals on combination ART, especially in those receiving protease inhibitors (PI). CSF viral load was also associated with higher monocyte activation in CSF. The mean calculated low density lipoprotein (LDL)-, oxidized LDL- and total cholesterol in plasma were highest in patients receiving PI.
Conclusions: Activated monocytes are enriched in the CSF of persons living with HIV-1 and receiving ART. This finding is consistent with previously reported autopsy series. The mechanisms and long-term clinical consequences of persistent monocyte activation require further study.
Introduction
Several observations link activated monocytes and macrophages with HIV-pathogenesis. Activated CD14/CD16 monocytes are increased in the blood of HIV-infected patients in general, and in patients with HIV-dementia in particular [1,2]. Activated monocytes traffic from bone marrow via blood to the brain [3,4] and are found in abundance in the perivascular area of the brain of HIV-infected patients. Monocytes/macrophages and monocyte-derived HIV giant cells are signs of HIV-encephalopathy, the neuropathological correlate for HIV dementia. HIV encephalopathy is not always paired with clinical dementia, but the abundance of monocytes/macrophages in brain tissue is a better correlate of HIV dementia than the extent of viral infection in the brain [5]. In HIV disease, monocytes/macrophages invade tissues, [6,7] possibly homing to sites of infection and inflammation [8]. The role of monocyte activation and trafficking into tissues is less clear during combination antiretroviral therapy (ART). Although clinical brain disease is less common in patients on ART, autopsy series indicate that despite treatment, brain tissue can contain high numbers of monocytes/macrophages and monocyte-derived HIV giant cells [9-12].
Cerebrospinal fluid (CSF) is accessible in living people by lumbar puncture. CSF is connected to the perivascular space of the brain and reflects events in brain tissue. To assess the effects of combination ART and viral load on activated monocytes in CSF, we recruited three groups of HIV-infected patients: 'treatment successes' (plasma viral load <500 copies/ml); 'treatment failures' (plasma viral load >500 copies/ml); and individuals off ART. We also registered whether ART included protease inhibitors (PI). To assess activated monocytes in CSF, we developed a novel six-color flow cytometric monocyte assay. The use of multiple colors on one cell was essential to definitely identify activated monocytes and to make optimal use of the limited cell numbers in CSF. By adding quantification beads, we determined relative and absolute counts of activated monocytes in parallel.
We assessed several clinical patient characteristics that have been linked with monocyte activation, including plasma lipids. Plasma lipids are known to be elevated during combination ART [13-17] and have been associated with monocyte activation [18,19]. A particular modified lipid, oxidized low density lipoprotein-cholesterol (LDL-C) [20-22], can bind to scavenger receptor CD36 on monocytes [23-25]. CD36 is part of the innate immune system and helps remove damaged or apoptotic cells displaying damaged outer lipid membranes from the body; CD36 is also involved in the pathogenesis of atherosclerosis [26,27]. Combination ART leads to an atherogenic lipid profile with increased LDL-C and total cholesterol [13-17], increases several plasma lipids [28], and downregulates scavenger receptor CD36 expression on monocytes while increasing CD36 mRNA. The increased production of CD36 mRNA and protein facilitates the development of cholesterol-ester accumulating activated monocytes which are essential in the pathogenesis of atherosclerosis [28,29]. Combination ART, especially PI-containing ART, leads to increased atherosclerosis, that clinically manifests as coronary artery disease [30-34], transient ischemic attacks [35], and strokes [36-38]. Whether lipids and modified lipids play a role in the pathogenesis of atherosclerosis in patients on PI-containing ART is not known.
We investigated whether activated monocytes appear in CSF of living individuals on combination ART, what clinical parameters are associated with their abundance, and whether lipids and modified lipids are increased on ART.
Materials and methods
Study population
Seventy-six HIV-1-seropositive and eight HIV-1-seronegative subjects were seen for study visits at San Francisco General Hospital (SFGH)'s Clinical Research Center. Each participant had a lumbar puncture and blood draw. The Committee on Human Subject Research at the University of California, San Francisco (UCSF) approved the protocol, including informed consent. To allow comparisons by treatment status and outcome, balanced groups of individuals were selected so that there were comparable numbers of treated and untreated individuals, and comparable numbers of treatment successes (defined as viral load <500 copies/ml on ART) versus treatment failures (defined as viral load >500 copies/ml on ART). In addition, a small group of HIV-uninfected controls was recruited.
Viral loads and flow cytometry
Plasma and CSF viral loads were determined using the Amplicor HIV-1 Monitor assay V1.0 and V1.5 with UltraSensitive RNA extraction (Roche Diagnostics, Branchburg, New Jersey, USA). The following monoclonal antibodies (mAb) were used: CD45-fluoresceine isothiocyanate (FITC, Pharmingen, San Diego, California, USA), CD16-phycoerythrin (PE, Pharmingen), CD14-EnergyCouplesDye (ECD)/PE/Texas red (Immunotech, Westbrook, Maine, USA), CCR5-allophycocyanin (APC, Pharmingen), CD4-phycoerythrin/cyanin (Pe-Cy7) (Becton Dickinson, San José, California, USA), CD3-APC-Cy7 (eBioscience, San Diego, California, USA). TRUcount tubes (Becton Dickinson) were used for cell quantification. Data was acquired using a FACSVantage (Becton Dickinson) and CellQuest software.
FACS analysis was performed with Flojo software (Tree Star, Ashland, Oregon, USA). In blood and CSF, the percentages and absolute counts of activated cell subsets were simultaneously determined using activation markers CD16 and CCR5 on monocytes. Live cells were identified using CD45/side scatter, monocytes were identified using CD14+/CD4+low, and activated (CD16 and CCR5) monocyte subsets were identified using Fluorescence Minus One (FMO) samples [39] derived from blood. The scarcity of CSF cells did not allow for CSF-FMO-samples. All blood samples were run in triplicate (three individually stained tubes) of at least 100 000 events each. CSF samples were run in four different acquisition files of 3 × 10 000 events plus a fourth file containing all remaining events to diminish artifacts from cell aggregates. The fourth file contained 10 000-300 000 events (average approximately 80 000 events). Percentages and absolute counts of CSF cell subsets were calculated as the average of all acquisitions of a particular sample.
Blood and CSF processing
Blood (100 μl, EDTA as anticoagulant) was incubated with mouse IgG (10 μl) (Caltag, Burlingame, California, USA) for 15 min to decrease Fc-receptor binding, then incubated with mAb for 15 min at room temperature in the dark. Erythrocytes were lysed using FACSlyse (Becton Dickinson). EDTA (0.5 mM) was added to the CSF sample. CSF specimens were centrifuged at 400 × g for 15 min. The supernatant was decanted, and the cells were resuspended in a residual volume of 100 μl CSF and stained as blood except without lysis. The entire CSF sample was analyzed to maximize cell counts. To obtain absolute counts of a desired cell subset, the event count of the acquired cell subset was divided by the event count of the acquired beads and related to the ratio of the known input volume of blood (100 μl per tube) or CSF (6.5-12 ml) and the known input value of beads.
Lipid measurements
Lipid profiles of total cholesterol, LDL-C, high density lipoprotein (HDL)-C, and triglycerides were performed at the SFGH Clinical Laboratory on frozen plasma from the day of the monocyte assessment. Results were given in mg/dl. LDL-C was calculated using the Friedewald calculation formula: [total cholesterol-(HDL-C + triglycerides/5)]. The triglycerides/5 calculation is an estimated very LDL and not valid in the SFGH laboratory when triglyceride levels are >400 mg/dl. The low end reportable range for triglycerides is 40 mg/dl, so if the triglyceride result was <40 mg/dl, an LDL-C calculation was not performed.
Oxidized LDL-C was measured in frozen plasma from the day of the monocyte assessment using an Oxidized-LDL-ELISA-kit (Mercodia, Uppsala, Sweden), which utilizes a murine monoclonal antibody, mAb-4E6. Samples were run in duplicate.
Lipid measurements were performed on non-fasting plasma samples. Fasting mainly affects triglyceride levels and calculated LDL-C levels, which include triglyceride levels in the calculation [40]. Total cholesterol, oxidized LDL-C, and HDL-C are not severely affected by non-fasting.
Statistics
Univariate 2-group comparisons were done by unpaired t test, and correlations shown are rank correlations. To assess possible confounding or mediating variables, we used multiple regression to model and test the impacts of PI use and other predictors on activated monocytes in CSF. Because activated monocyte counts were skewed, we logarithmically transformed these before modeling them. This produced residuals from all models that appeared to be normally distributed as required for model validity. The effect of predictors was back-transformed to a multiplicative percentage effect with the formula 100*(2^(beta)-1), because we used the base-2 logarithm. We also used this transformation for some skewed predictors, so their estimated effects are per twofold increase. We also modeled the percentage of CSF white blood cells (WBC) that were activated monocytes. This was not skewed and, therefore, not transformed. The normality assumption appeared to be acceptable in multivariate models that included CSF log10 viral load as a predictor. Models of activated monocyte count did not control for CSF WBC because doing so would make these models almost equivalent to modeling the percentage of WBC that were activated monocytes (after the logarithmic transformations used), which we instead modeled directly. We performed similar models for activated monocytes in blood.
Results
Study population
We assessed paired CSF/blood specimens from 76 HIV-1-seropositive persons and eight HIV-1-seronegative controls (Table 1). All paired samples were collected at the same visit. Most participants were male. The mean ages were similar between groups. The HIV-infected groups included 38 persons on treatment, with 22 treatment successes (HIV RNA <500 copies/ml) and 16 treatment failures (HIV RNA >500 copies/ml), and 38 persons off treatment. Patients on ART were additionally divided into PI-containing regimen (n = 27) or non-PI-containing regimen (n = 11). None of the participants suffered from opportunistic central nervous system diseases at the time their CSF/blood samples were taken.
As expected, HIV-infected patients had lower CD4 T-cell counts and higher CD8 T-cell counts than HIV-uninfected individuals. By definition, plasma viral RNA levels were low in the treatment success group (mean 1.40 log10 copies/ml) and were substantial in both the treatment failures (mean 4.20 log10 copies/ml) and those off therapy (mean 3.88 log10 copies/ml). CSF viral loads were lower than blood plasma viral loads in all groups, especially in the treatment failures in which geometric mean CSF viral loads were more than 100-fold (2.49 log10) lower than in blood. CSF pleocytosis was evident in untreated individuals, but not in treated patients, which had CSF WBC in the normal range (1-5 cells/ μl). The CSF/plasma albumin ratios in all HIV-infected groups were not significantly different from uninfected controls. It is, therefore, unlikely that the observed differences were due to a disturbed blood-brain barrier (Table 1).
PI-containing regimens increase percentages of activated monocytes in CSF
The mean percentage of activated CD16 monocytes in CSF was highest in the treatment successes, higher than in either those failing treatment or those off treatment, despite lower plasma and CSF viral load. To identify factors that might explain why virological successes and treated patients had higher levels of activated monocytes in CSF, we divided patients on ART into two groups, PI-containing regimen (n = 27) and non-PI-containing regimen (n = 11). Among all patients on ART, those who were on a PI-containing regimen had the highest percentages of activated monocytes in the CSF (Fig. 1a). PI users had higher monocyte activation percentages in CSF than uninfected controls (P = 0.0009), patients off treatment (P = 0.004), and patients on non-PI-containing regimens (P = 0.02) (Fig. 1a). In multivariate analysis, there was no effect of the recruitment group membership (virological success versus failure) after the use of PI was considered in the model.
All HIV-infected groups had higher mean percentages of activated monocytes in CSF than the uninfected control group. In contrast, the mean percentage of activated CD16 monocytes in the blood did not differ significantly among the groups (Fig. 1). However, the highest percentages of monocyte activation in blood were found in the uninfected controls. Furthermore, there was a trend towards lower activation profiles in PI users in blood compared to uninfected controls (P = 0.065) (Fig. 1b).
PI-containing regimens increase absolute counts of CD16 activated monocytes in CSF
Absolute cell counts mirrored the results for percentages of CD14/CD16 monocytes in CSF. Among all individuals on ART, those who were on a PI-containing regimen had the highest absolute counts of activated monocytes in CSF (Fig. 1c). The mean absolute count of activated CD16 monocytes in CSF was highest in the treatment successes, higher than in either those failing treatment or those off treatment (despite lower plasma and CSF viral load). All HIV-infected patients had higher absolute counts of activated monocytes than uninfected controls. In blood, CD14/CD16 counts/μl did not differ significantly, but were highest in uninfected controls (Fig. 1d).
CSF viral load was an independent predictor for activated monocytes in CSF
We found that among patients not taking PI, those with a measurable CSF viral load had higher percentages of activated monocytes in CSF (Fig. 2). The positive association between detectable CSF viral load and activated monocytes was evident in those off ART and those on regimens that were non-PI-containing. Figure 2 shows the univariate effect in patients on a non-PI-containing regimen and in patients off treatment. In those on PI-containing regimens, the influence of CSF viral load is masked by the strong PI effect. Thus, in absence of PI, CSF viral load appears to increase monocyte activation.
CCR5 monocytes and T cells in CSF and blood
CCR5 expression on monocytes transduces chemotactic signals that affect monocyte trafficking. We found that the percentage of monocytes expressing CCR5 is much higher in CSF than in blood in all groups, regardless of HIV infection status, ART, or response to ART. For example, among uninfected persons, the average percentage of monocytes expressing CCR5 was 17.7% in the CSF and 0.2% in the blood, and in patients off therapy the average percentages were 16.2% versus 0.3%, respectively. Greater proportions of CD4 and CD8 T cells expressing CCR5 were also observed in CSF compared with blood, although the pattern was less striking than with monocytes. Among patients off therapy, the average percentages of T cells expressing CCR5 were 13.5% versus 2.5% for CD4 T cells and 17.6% versus 5.5% for CD8 T cells in CSF and blood, respectively.
Lipids in plasma: the mean total, calculated LDL- and oxidized LDL-C were highest in the PI group
Among HIV-infected patients, the total cholesterol, calculated LDL-C, and oxidized LDL-C levels were highest in patients on PI and lowest in patients off therapy (Fig. 3). HDL-C appeared similar in different groups. Triglycerides and oxidized LDL-C were found to be higher in all HIV-infected groups than in uninfected controls. Total plasma cholesterol and calculated LDL-C were higher in HIV-infected groups on ART than in HIV-infected patients off treatment and uninfected controls, which showed comparable results. We assessed those factors at the same clinic visit as the virological and monocyte characterization.
Plasma cholesterol and CSF WBC
We found that in patients on ART (successes and failures), plasma cholesterol levels correlated with CSF WBC, even though pleocytosis was uncommon (Fig. 4). Patients on ART had a relatively low CSF WBC with a median of 1.5 × 106 cells/l (intraquartile range, 0-3.3 × 106 cells/l). In this group, the median cholesterol was 182.5 mg/dl (intraquartile range, 162.5-202.5 mg/dl).
Multivariate analysis
The bivariate analysis suggested that activated monocytes in CSF (percentages and absolute counts) were most strongly associated with PI use. To identify independent associations, we performed a multivariate regression analysis to control for statin use, CD4 T-cell count, CSF viral load, and CSF WBC.
In multivariate models of percentages of activated monocytes in CSF, the estimated effect of PI use was an increase of 25.6% [95% confidence interval (CI), 12.7-38.5; P = 0.0002] indicating a positive and independent association. Elevated levels of activated monocytes in CSF among PI users were comparable when compared with use of non-PI ART regimens (22.9% elevation in activated monocytes) and those not receiving any ART (27.1% elevation). The PI effect appeared to have a rapid onset, because the estimated effect of duration of PI use was only an increase of 6.9% per year on PI (P = 0.64). The other predictor that reached statistical significance was CSF viral load. In multivariate analysis, CSF viral load was estimated to increase the percentage of activated monocytes in CSF by 8.7% per 1 log10 increase (95% CI, 1.8-15.5; P = 0.014).
In multivariate models of absolute counts of activated monocytes in CSF, the estimated effect of PI use was to double the activated monocyte count (estimated effect, +104%; 95% CI, -5 to +336%; P = 0.066). Additionally in this analysis, patients with higher CD4 count or higher CSF viral load tended to have higher absolute counts of CD16 monocytes in CSF.
Discussion
In an autopsy series previously reported, we found increased numbers of monocytes/macrophages in brain tissue of HIV-infected patients previously exposed to combination ART [9]. We now report an increase in activated monocytes in the CSF of living patients receiving ART. The mean percentage and number of activated CD16 monocytes in CSF was highest in individuals on PI, higher than in those on a non-PI-containing regimen or those not receiving ART. In multivariate analysis, PI treatment was the strongest predictor of the percentage of activated monocytes in CSF. After controlling for the effects of PI therapy, subjects with increased CSF viral load had increased monocyte activation in CSF. Other clinical parameters including plasma viral load, plasma CD4 and CD8 T-cell counts, CSF WBC, and different plasma lipids appeared to have only minimal effects after controlling for use of PI.
The mechanisms linking combination ART use, especially PI use, with activated monocytes in CSF is not known. The association between PI use and plasma cholesterol was reported previously [13] and was also found in our study. LDL-C and oxidized LDL-C were not associated with activated monocytes after controlling for PI use. The lack of an independent association between plasma lipids and monocyte activation in CSF may reflect a limitation in our cross-sectional study design, in which the many host and environmental determinants of lipid metabolism could not be controlled for; furthermore, lipids were measured under non-fasting conditions. Longitudinal study controlling for host determinants of lipids will be needed to evaluate whether lipid levels are linked with monocyte activation, which could occur due to drug or lipid effects on CD36 [28,29], CCR2 [41,42], MCP-1 [43-46], or other factors [24].
Alternatively, PI use may be linked to monocyte activation in CSF through other mechanisms. Monocytes are antigen-presenting cells, and the biology of antigen-presenting cells is changed by PI treatment [47]. Ritonavir is known to selectively inhibit the chymotrypsin-like activity of the 20S core structure of the proteasome, which affects expression of class I histocompatibility antigens. This change in antigen presentation induced by PI could also affect trafficking mechanisms. Moreover, in vitro studies have demonstrated that PI can impair sterol regulatory enhancer-binding protein-1 nuclear localization and inhibit adipocyte differentiation [48,49]. Activated monocytes that have the ability to accumulate cholesterol esters are biologically similar to adipocytes. Inhibiting cell differentiation might also alter trafficking mechanisms. Furthermore, apoptosis of monocytes/macrophages might be altered on PI, as is known for HIV-infected macrophages [50]. Additional laboratory and clinical research is needed to define the mechanism linking PI use with monocyte activation.
Although PI treated individuals had higher monocyte activation in CSF, they tended to have lower monocyte activation in blood, possibly reflecting egress into tissues. An increased density of tissue macrophages in organs of HIV-infected persons has been described [6-8] and an association between HIV-related encephalopathy and cardiomyopathy has been suggested [51]. Interestingly, anemia is an important predictor of HIV-associated dementia [52-55]. Activated monocytes become depleted in bone marrow of patients with anemia, while they are enriched in brain tissue of patients with HIV-dementia [3]. These pathological consequences of HIV infection may have a common basis involving increased trafficking of activated monocytes into afflicted tissues.
We observed a positive association between CSF viral load and increased monocyte activation in CSF. Expression of foreign antigen inside the brain could cause monocytes to invade brain tissue. Brain tissue is exposed to virus early in HIV infection, and some cells become infected [56]. This foreign antigen might lead to activation of resident macrophages, and these in turn can secrete chemokines that attract more monocytes from the circulation. When the HIV-infected patient starts ART, and immune function is partially restored, trafficking of monocytes into the CSF may be augmented further. This process of monocyte trafficking from bone marrow via blood to brain tissue might represent immune restoration during treatment that fails to eliminate viral antigens entirely.
In the past, HIV dementia was common in late-stage HIV disease. Since the introduction of combination ART, it is rarely seen in clinical practice [57-59]. Nevertheless, HIV dementia continues to be seen [9,11,12] even though severe dementia is less common [9,11,12,60]. In our study, activated monocytes are enriched in the CSF of living HIV-infected patients on PI containing ART. The clinical consequences of accumulation of activated monocytes in CSF have not yet been determined. Although none of the patients in this study had clinical evidence of dementia, it is possible that low-level inflammation and accumulation of activated monocytes in CSF represent a long-term pathological process.
Although combination therapy improves HIV-associated dementia in the short-term, enrichment of activated monocytes in brain tissue and CSF may have long-term clinical consequences. Increases in cerebrovascular and cardiovascular incidents already became apparent in the period 1996-2004 after the introduction of PI-containing combination ART. Combination therapies are expected to prolong life for several decades, during which time novel clinical manifestations of chronic HIV infection and treatment may occur in susceptible persons. Combination ART became widely used in clinical practice in 1997, providing insufficient experience to predict long-term outcomes, which should be monitored in cohorts of ART-treated individuals.
Acknowledgements
Sponsorship: Supported by NIH grants RO1 NS37660 and RO1 MH62701 (R.W.P.), UARP CC02-SF-002/UCSF California AIDS Research Center (R.M.G.), UARP F04-SF-215 Postdoctoral Fellowship Grant (J.K.N.), UCSF California AIDS Research Center (C-ARC) Innovative Grant Program (J.K.N.) and the Gladstone Institute for Virology and Immunology, San Francisco, CA.
The authors thank all study participants, Gary Howard from the Gladstone Editorial Department and John Carroll from the Gladstone Graphics Department.
References
1. Pulliam L, Gascon R, Stubblebine M, McGuire D, McGrath MS. Unique monocyte subset in patients with AIDS dementia. Lancet 1997; 349:692-695. 2. Kusdra L, McGuire D, Pulliam L. Changes in monocyte/macrophage neurotoxicity in the era of HAART: implications for HIV-associated dementia. AIDS 2002; 16:31-38. 3. Gartner S. HIV infection and dementia. Science 2000; 287:602-604. 4. Gartner S, Liu Y. Insights into the role of immune activation in HIV neuropathogenesis. J Neurovirol 2002; 8:69-75. 5. Glass JD, Fedor H, Wesselingh SL, McArthur JC. Immunocytochemical quantitation of human immunodeficiency virus in the brain: correlations with dementia. Ann Neurol 1995; 38:755-762. 6. Hufert FT, Schmitz J, Schreiber M, Schmitz H, Racz P, von Laer DD. Human Kupffer cells infected with HIV-1 in vivo. J Acquir Immune Defic Syndr 1993; 6:772-777. 7. Kapasi A, Bhat P, Singhal PC. Tubular cell and HIV-1 gp120 interaction products promote migration of monocytes. Inflammation 1998; 22:137-144. 8. Fischer-Smith T, Croul S, Sverstiuk AE, Capini C, L'Heureux D, Regulier EG, et al. CNS invasion by CD14+/CD16+ peripheral blood-derived monocytes in HIV dementia: perivascular accumulation and reservoir of HIV infection. J Neurovirol 2001; 7:528-541. 9. Neuenburg JK, Brodt HR, Herndier BG, Bickel M, Bacchetti P, Price RW, et al. HIV-related neuropathology, 1985 to 1999: rising prevalence of HIV encephalopathy in the era of highly active antiretroviral therapy. J Acquir Immune Defic Syndr 2002; 31:171-177. 10. Budka H. Multinucleated giant cells in brain: a hallmark of the acquired immune deficiency syndrome (AIDS). Acta Neuropathologica 1986; 69:253-258. 11. Masliah E, DeTeresa RM, Mallory ME, Hansen LA. Changes in pathological findings at autopsy in AIDS cases for the last 15 years. AIDS 2000; 14:69-74. 12. Gray F, Adle-Biassette H, Chretien F, Lorin de la Grandmaison G, Force G, Keohane C. Neuropathology and neurodegeneration in human immunodeficiency virus infection. Pathogenesis of HIV-induced lesions of the brain, correlations with HIV-associated disorders and modifications according to treatments. Clin Neuropathol 2001; 20:146-155. 13. Periard D, Telenti A, Sudre P, Cheseaux JJ, Halfon P, Reymond MJ, et al. Atherogenic dyslipidemia in HIV-infected individuals treated with protease inhibitors. The Swiss HIV Cohort Study. Circulation 1999; 100:700-705. 14. Berthold HK, Parhofer KG, Ritter MM, Addo M, Wasmuth JC, Schliefer K, et al. Influence of protease inhibitor therapy on lipoprotein metabolism. J Intern Med 1999; 246:567-575. 15. Badiou S, De Boever CM, Dupuy AM, Baillat V, Cristol JP, Reynes J. Small dense LDL and atherogenic lipid profile in HIV-positive adults: influence of lopinavir/ritonavir-containing regimen. AIDS 2003; 17:772-774. 16. Fantoni M, Del Borgo C, Autore C, Barbaro G. Metabolic disorders and cardiovascular risk in HIV-infected patients treated with antiretroviral agents. Ital Heart J 2002; 3:294-299. 17. Bonnet E, Ruidavets JB, Tuech J, Ferrieres J, Collet X, Fauvel J, et al. Apoprotein c-III and E-containing lipoparticles are markedly increased in HIV-infected patients treated with protease inhibitors: association with the development of lipodystrophy. J Clin Endocrinol Metab 2001; 86:296-302. 18. Panasenko OM, Vol'nova TV, Osipov AN, Azizova OA, Vladimirov Yu A. Free-radical generation by monocytes and neutrophils: a possible cause of plasma lipoprotein modification. Biomed Sci 1991; 2:581-589. 19. Aviram M. Interaction of oxidized low density lipoprotein with macrophages in atherosclerosis, and the antiatherogenicity of antioxidants. Eur J Clin Chem Clin Biochem 1996; 34:599-608. 20. Steinberg D, Witztum JL. Is the oxidative modification hypothesis relevant to human atherosclerosis? Do the antioxidant trials conducted to date refute the hypothesis? Circulation 2002; 105:2107-2111. 21. Landmesser U, Harrison DG. Oxidant stress as a marker for cardiovascular events: Ox marks the spot. Circulation 2001; 104:2638-2640. 22. Harrison DG, Ohara Y. Physiologic consequences of increased vascular oxidant stresses in hypercholesterolemia and atherosclerosis: implications for impaired vasomotion. Am J Cardiol 1995; 75:75B-81B. 23. Palinski W, Horkko S, Miller E, Steinbrecher UP, Powell HC, Curtiss LK, et al. Cloning of monoclonal autoantibodies to epitopes of oxidized lipoproteins from apolipoprotein E-deficient mice. Demonstration of epitopes of oxidized low density lipoprotein in human plasma. J Clin Invest 1996; 98:800-814. 24. Steinberg D. Low density lipoprotein oxidation and its pathobiological significance. J Biol Chem 1997; 272:20963-20966. 25. Martens JS, Reiner NE, Herrera-Velit P, Steinbrecher UP. Phosphatidylinositol 3-kinase is involved in the induction of macrophage growth by oxidized low density lipoprotein. J Biol Chem 1998; 273:4915-4920. 26. Han J, Hajjar DP, Febbraio M, Nicholson AC. Native and modified low density lipoproteins increase the functional expression of the macrophage class B scavenger receptor, CD36. J Biol Chem 1997; 272:21654-21659. 27. Febbraio M, Podrez EA, Smith JD, Hajjar DP, Hazen SL, Hoff HF, et al. Targeted disruption of the class B scavenger receptor CD36 protects against atherosclerotic lesion development in mice. J Clin Invest 2000; 105:1049-1056. 28. Dressman J, Kincer J, Matveev SV, Guo L, Greenberg RN, Guerin T, et al. HIV protease inhibitors promote atherosclerotic lesion formation independent of dyslipidemia by increasing CD36-dependent cholesteryl ester accumulation in macrophages. J Clin Invest 2003; 111:389-397. 29. Serghides L, Nathoo S, Walmsley S, Kain KC. CD36 deficiency induced by antiretroviral therapy. AIDS 2002; 16:353-358. 30. Vittecoq D, Escaut L, Chironi G, Teicher E, Monsuez JJ, Andrejak M, et al. Coronary heart disease in HIV-infected patients in the highly active antiretroviral treatment era. AIDS 2003; 17:S70-S76. 31. Hsue PY, Giri K, Erickson S, MacGregor JS, Younes N, Shergill A, et al. Clinical features of acute coronary syndromes in patients with human immunodeficiency virus infection. Circulation 2004; 109:316-319. 32. Cotter BR. Epidemiology of HIV cardiac disease. Prog Cardiovasc Dis 2003; 45:319-326. 33. Mooser V. Atherosclerosis and HIV in the highly active antiretroviral therapy era: towards an epidemic of cardiovascular disease? AIDS 2003; 17:S65-S69. 34. Neumann T, Miller M, Esser S, Gerken G, Erbel R. Atherosclerosis in HIV-positive patients. Z Kardiol 2002; 91:879-888. 35. Hsue PY, Lo JC, Franklin A, Bolger AF, Martin JN, Deeks SG, et al. Progression of atherosclerosis as assessed by carotid intima-media thickness in patients with HIV infection. Circulation 2004; 109:1603-1608. 36. Evers S, Nabavi D, Rahmann A, Heese C, Reichelt D, Husstedt IW. Ischaemic cerebrovascular events in HIV infection: a cohort study. Cerebrovasc Dis 2003; 15:199-205. 37. Zunker P, Nabavi DG, Allardt A, Husstedt IW, Schuierer G. HIV-associated stroke: report of two unusual cases. Stroke 1996; 27:1694-1696. 38. Menge T, Neumann-Haefelin T, von Giesen HJ, Arendt G. Progressive stroke in an HIV-1-positive patient under protease inhibitors. Eur Neurol 2000; 44:252-254. 39. Roederer M, Brenchley JM, Betts MR, De Rosa SC. Flow cytometric analysis of vaccine responses: how many colors are enough? Clin Immunol 2004; 110:199-205. 40. Rifai N, Merrill JR, Holly RG. Postprandial effect of a high fat meal on plasma lipid, lipoprotein cholesterol and apolipoprotein measurements. Ann Clin Biochem 1990; 27:489-493. 41. Han KH, Tangirala RK, Green SR, Quehenberger O. Chemokine receptor CCR2 expression and monocyte chemoattractant protein-1-mediated chemotaxis in human monocytes. A regulatory role for plasma LDL. Arterioscler Thromb Vasc Biol 1998; 18:1983-1991. 42. Han KH, Han KO, Green SR, Quehenberger O. Expression of the monocyte chemoattractant protein-1 receptor CCR2 is increased in hypercholesterolemia. Differential effects of plasma lipoproteins on monocyte function. J Lipid Res 1999; 40:1053-1063. 43. Zink MC, Coleman GD, Mankowski JL, Adams RJ, Tarwater PM, Fox K, et al. Increased macrophage chemoattractant protein-1 in cerebrospinal fluid precedes and predicts simian immunodeficiency virus encephalitis. J Infect Dis 2001; 184:1015-1021. 44. Bernasconi S, Cinque P, Peri G, Sozzani S, Crociati A, Torri W, et al. Selective elevation of monocyte chemotactic protein-1 in the cerebrospinal fluid of AIDS patients with cytomegalovirus encephalitis. J Infect Dis 1996; 174:1098-1101. 45. Charo IF, Peters W. Chemokine receptor 2 (CCR2) in atherosclerosis, infectious diseases, and regulation of T-cell polarization. Microcirculation 2003; 10:259-264. 46. Charo IF, Taubman MB. Chemokines in the pathogenesis of vascular disease. Circ Res 2004; 95:858-866. 47. Andre P, Groettrup M, Klenerman P, de Giuli R, Booth BL Jr, Cerundolo V, et al. An inhibitor of HIV-1 protease modulates proteasome activity, antigen presentation, and T cell responses. Proc Natl Acad Sci USA 1998; 95:13120-13124. 48. Grinspoon S, Carr A. Cardiovascular risk and body-fat abnormalities in HIV-infected adults. N Engl J Med 2005; 352:48-62. 49. Jain RG, Lenhard JM. Select HIV protease inhibitors alter bone and fat metabolism ex vivo. J Biol Chem 2002; 277:19247-19250. 50. Cosenza MA, Zhao ML, Lee SC. HIV-1 expression protects macrophages and microglia from apoptotic death. Neuropathol Appl Neurobiol 2004; 30:478-490. 51. Antinori A, Giancola ML, Alba L, Soldani F, Grisetti S. Cardiomyopathy and encephalopathy in AIDS. Ann N Y Acad Sci 2001; 946:121-129. 52. McArthur JC, Hoover DR, Bacellar H, Miller EN, Cohen BA, Becker JT, et al. Dementia in AIDS patients: incidence and risk factors. Multicenter AIDS Cohort Study. Neurology 1993; 43:2245-2252. 53. Qureshi AI, Hanson DL, Jones JL, Janssen RS. Estimation of the temporal probability of human immunodeficiency virus (HIV) dementia after risk stratification for HIV-infected persons. Neurology 1998; 50:392-397. 54. Buchanan RJ, Wang S, Huang C. Nursing home residents with HIV and anemia. AIDS Patient Care STDS 2001; 15:373-383. 55. Brokering KL, Qaqish RB. Management of anemia of chronic disease in patients with the human immunodeficiency virus. Pharmacotherapy 2003; 23:1475-1485. 56. Miyake A, Enose Y, Ohkura S, Suzuki H, Kuwata T, Shimada T, et al. The quantity and diversity of infectious viruses in various tissues of SHIV-infected monkeys at the early and AIDS stages. Arch Virol 2004; 149:943-955. 57. Sacktor N, Lyles RH, Skolasky R, Kleeberger C, Selnes OA, Miller EN, et al. HIV-associated neurologic disease incidence changes: Multicenter AIDS Cohort Study, 1990-1998. Neurology 2001; 56:257-260. 58. Sacktor N, McDermott MP, Marder K, Schifitto G, Selnes OA, McArthur JC, et al. HIV-associated cognitive impairment before and after the advent of combination therapy. J Neurovirol 2002; 8:136-142. 59. Maschke M, Kastrup O, Esser S, Ross B, Hengge U, Hufnagel A. Incidence and prevalence of neurological disorders associated with HIV since the introduction of highly active antiretroviral therapy (HAART). J Neurol Neurosurg Psychiatry 2000; 69:376-380. 60. Dore GJ, McDonald A, Li Y, Kaldor JM, Brew BJ. Marked improvement in survival following AIDS dementia complex in the era of highly active antiretroviral therapy. AIDS 2003; 17:1539-1545. © 2005 Lippincott Williams & Wilkins, Inc.
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