Endothelial activation markers are linked to HIV status and are independent of antiretroviral therapy and lipoatrophy

Biomarkers and HIV-associated cardiovascular disease

PURPOSE OF REVIEW

Our goal is to summarize recent literature on biomarkers of cardiovascular disease (CVD) in the setting of HIV infection with an emphasis on those associated with clinical events.

RECENT FINDINGS

Epidemiological data have demonstrated that HIV infection is associated with increases in well established markers of inflammation and thrombosis, and levels of high sensitivity C-reactive protein, interleukin-6, and D-dimer predict CVD and mortality risk in HIV cohorts. Levels of interleukin-6, D-dimer and endothelial adhesion molecules increase when antiretroviral therapy is interrupted, suggesting that HIV replication may be driving CVD risk in this context. However, data on changes in many CVD biomarkers after starting antiretroviral therapy are inconsistent or lacking. Finally, high-density lipoprotein particles may be more informative than other lipoprotein measures for CVD risk specifically among individuals with HIV infection.

SUMMARY

Biomarkers of inflammation and thrombosis have the potential to improve CVD risk stratification beyond traditional and HIV-specific factors, and may prove useful for evaluating CVD prevention strategies for individuals with HIV infection.

Premature onset of cardiovascular disease in HIV-infected individuals: the drugs and the virus

Life expectancy in HIV-infected individuals has been greatly enhanced through immunologic restoration and virologic suppression resulting from antiretroviral therapy. Current clinical HIV care in Western countries focuses on treatment of drug toxicities and prevention of comorbidities. These non-AIDS HIV-related comorbidities, such as cardiovascular disease, occur even in individuals with virologic suppression and manifest at an earlier age than when normally presenting in the general population. While traditional risk factors are present in many HIV-infected individuals who develop cardiovascular disease, the additional roles of HIV-related chronic inflammation and immune activation as well as chronic HIV viremia may be significant. This review provides current evidence for the contributions of the virus, in terms of both chronic viremia and its contribution via chronic low-level inflammation, immune activation, premature immune senescence and dyslipidemia, to the pathogenesis of HIV-related cardiovascular disease, and balances this against the propensity of specific antiretroviral therapies to cause cardiovascular disease, in particular through altered cholesterol metabolism.

Relationship of body composition, metabolic status, antiretroviral use, and HIV disease factors to endothelial dysfunction in HIV-infected subjects

Vascular endothelial dysfunction may contribute to the increase in cardiovascular events during HIV-1 infection and its treatment. Antiretroviral therapy (ART), metabolic factors, lipodystrophy, and HIV infection itself may be involved. Ninety-six HIV-infected subjects were evaluated for endothelial function by measurement of brachial artery flow-mediated dilation (FMD) by ultrasound, single-slice CT of the abdomen and mid-thigh, whole-body dual x-ray absorptiomety (DXA) scans, and metabolic evaluations in a cross-sectional study. The median age was 40 years; 28% were female, 38% black, 3% Hispanic, and 59% white. Forty-nine (51%) were receiving ART, which included a PI in 28 (57%) and was non-PI based in 21 (43%). FMD (+/-SD) in subjects not on ART was 5.5 +/- 4.3%, PI-ART 5.3 +/- 3.6%, and non-PI-ART 5.5 +/- 4.1% (p = 0.9). Age, race, CD4 cell count, and HIV RNA did not correlate significantly with FMD. Among ART-treated subjects in the lowest tertile of thigh subcutaneous fat area (range 3-31 cm(2)), FMD was 4.4 +/- 3.5% and in the highest tertile (range 67-237 cm(2)) FMD was 6.8 +/- 3.6% (p = 0.07, t-test). However, in multivariate analyses, no body composition measure showed a significant association with FMD for either the group as a whole or in ART-treated subjects. ART use, PI use, CD4 cell count, and HIV RNA levels were not associated with endothelial dysfunction by brachial FMD. A definitive association with measures of adiposity was not detected in multivariate analysis, suggesting that lipoatrophy may not be an important contributor to endothelial dysfunction in HIV-infected individuals on ART.

Salsalate is poorly tolerated and fails to improve endothelial function in virologically suppressed HIV-infected adults

In this 13-week, open-label, randomized study of the anti-inflammatory salsalate versus usual care, there were no significant improvements in flow-mediated dilation of the brachial artery, endothelial activation, inflammation or coagulation markers, homeostasis model assessment of insulin resistance or lipoproteins with salsalate or between groups in virologically suppressed, HIV-infected adults on antiretrovirals. Tinnitus and transaminitis occurred frequently in the salsalate group. Dose reduction due to toxicities encountered and low level of inflammation may explain these results.

Longitudinal changes in carotid intima-media thickness and cardiovascular risk factors in human immunodeficiency virus-infected children and young adults compared with healthy controls

OBJECTIVES

HIV-infected patients are at increased risk of cardiovascular disease (CVD). This study assessed longitudinal changes in carotid intima-media thickness (cIMT) as a surrogate marker for CVD, and determined the relationship between cIMT and cardiovascular risk factors in HIV infected children/young adults.

METHODS

This was a longitudinal, observational study comparing cIMT,fasting metabolic profile, and C-reactive protein in HIV-infected subjects 2 to 21 years old to matched controls at baseline and 48 weeks.

RESULTS

Thirty-five HIV + subjects and 37 controls were included in the analysis. Among HIV + subjects, the median age was 10 years, body mass index was 18.7 kg/m2, 37% were male, CD4 count was 32%, 77% had HIV-RNA 400 copies/mL, and 86% were on antiretrovirals. At baseline,HIV + had higher lipids and C-reactive protein. HIV-infected had higher internal carotid artery (ICA) and common carotid artery (CCA) IMT (mm)(ICA: HIV + , 0.90; controls, 0.78 [P = 0.01]; CCA: HIV + , 1.00; controls,0.95 [P = 0.05]). At 48 weeks, CD4% increased and low-density lipoprotein decreased in HIV-infected subjects. ICA and CCA median changes for HIV-infected subjects were -0.23 and -0.15 mm, respectively (both P 0.01). In controls, only CCA changed (P = 0.04). Between-group changes were not significant, except when only 31 perinatally infected HIV - subjects and the controls were compared (CCA P = 0.04). In multiple regression analyses of HIV + subjects, antiretroviral therapy duration and CD4% were associated with cIMT changes.

CONCLUSIONS

Higher cIMT was found in HIV-infected subjects than in healthy controls, but at 48 weeks, cIMT was similar between groups. These data suggest that HIV-infected children/young adults are at high risk of CVD, but lipid control, immune restoration, and viral suppression with continuous antiretroviral therapy may prevent its worsening.

Recent key advances in human immunodeficiency virus medicine and implications for China

In this article we summarize several recent major developments in human immunodeficiency virus treatment, prevention, outcome, and social policy change. Updated international guidelines endorse more aggressive treatment strategies and safer antiretroviral drugs. New antiretroviral options are being tested. Important lessons were learned in the areas of human immunodeficiency virus vaccines and microbicide gels from clinical studies, and additional trials in prevention, especially pre-exposure prophylaxis, are nearing completion. Insight into the role of the virus in the pathogenesis of diseases traditionally thought to be unrelated to acquired immunodeficiency syndrome has become a driving force for earlier and universal therapy. Lastly, we review important achievements of and future challenges facing China as she steps into her eighth year of the National Free Antiretroviral Treatment Program.

d-Dimer and CRP levels are elevated prior to antiretroviral treatment in patients who develop IRIS

Biomarkers could be useful in evaluating immune reconstitution inflammatory syndrome (IRIS). A cohort of 45 HIV-1-infected, antiretroviral treatment (ART)-naive patients with baseline CD4 T cell counts <or=100 cells/microL who were started on ART, suppressed HIV-RNA to <50 copies/mL, and seen every 1-3 months for 1 year were retrospectively evaluated for suspected or confirmed IRIS. d-Dimer, C-reactive protein (CRP), and selected autoantibodies were analyzed at baseline, 1 and 3 months post-ART in cryopreserved plasma. Median differences between cases and controls were compared with Mann-Whitney and Fisher's exact tests. Sixteen patients (35.6%) developed IRIS (median of 35 days post-ART initiation): unmasking=8, paradoxical=7, autoimmune=1. Pre-ART d-dimer and CRP were higher in IRIS cases versus controls (d-dimer: 0.89 mg/L versus 0.66 mg /L, p=0.037; CRP: 0.74 mg/L versus 0.39 mg/L, p=0.022), while d-dimer was higher in unmasking cases at IRIS onset (2.04 mg/L versus 0.36 mg /L, p=0.05). These biomarkers may be useful in identifying patients at risk for IRIS.

The macrophage: the intersection between HIV infection and atherosclerosis

HIV-infected individuals are at increased risk of coronary artery disease (CAD) with underlying mechanisms including chronic immune activation and inflammation secondary to HIV-induced microbial translocation and low-grade endotoxemia; direct effects of HIV and viral proteins on macrophage cholesterol metabolism; and dyslipidemia related to HIV infection and specific antiretroviral therapies. Monocytes are the precursors of the lipid-laden foam cells within the atherosclerotic plaque and produce high levels of proinflammatory cytokines such as IL-6. The minor CD14+/CD16+ "proinflammatory" monocyte subpopulation is preferentially susceptible to HIV infection and may play a critical role in the pathogenesis of HIV-related CAD. In this review, the central role of monocytes/macrophages in HIV-related CAD and the importance of inflammation and cholesterol metabolism are discussed.

Relationship between inflammatory markers, endothelial activation markers, and carotid intima-media thickness in HIV-infected patients receiving antiretroviral therapy

BACKGROUND

Human immunodeficiency virus (HIV)-infected patients are at increased risk of cardiovascular disease, which may be related to chronic inflammation and endothelial dysfunction despite virological control with antiretroviral therapy. The relationship between carotid intima-media thickness (IMT), a surrogate marker for cardiovascular disease, proinflammatory cytokines, and endothelial activation markers has not been fully explored in HIV-infected patients who are receiving antiretroviral therapy.

METHODS

We conducted a prospective, cross-sectional, observational study of treated HIV-infected patients and healthy control subjects to evaluate the relationship between carotid IMT, proinflammatory cytokines, endothelial activation biomarkers, and metabolic parameters in treated HIV-infected patients, compared with healthy control subjects.

RESULTS

We enrolled 73 HIV-infected patients and 21 control subjects. Common carotid artery and internal carotid artery IMT measurements, as well as tumor necrosis factor-alpha, high-sensitivity C-reactive protein, interleukin-6, myeloperoxidase, and soluble vascular cell adhesion molecule-1 levels were higher in the HIV-infected group. High-sensitivity C-reactive protein was the only biomarker that was positively correlated with carotid IMT in both groups. In the HIV-infected group, soluble vascular cell adhesion molecule-1 was positively correlated with all inflammatory cytokine levels. In multiple regression analysis, soluble vascular cell adhesion molecule-1, myeloperoxidase, and tumor necrosis factor-alpha levels were all associated with internal carotid artery IMT in the HIV-infected group, whereas age was associated with both common carotid artery and internal carotid artery IMT.

CONCLUSIONS

Enhanced endothelial activation, inflammation, and increased carotid IMT occur in HIV-infected patients despite antiretroviral therapy. Inflammatory markers are associated with endothelial activation, and both are associated with internal carotid artery IMT, supporting a potential role of inflammation in endothelial activation and cardiovascular disease in HIV infection.

Cardiovascular risk assessment in antiretroviral-naïve HIV patients

Various studies have been conducted to evaluate the role of antiretroviral therapy in the onset of cardiovascular risk among HIV-1-infected patients, while fewer data are available regarding antiretroviral-naïve patients. Our objective was to evaluate the cardiovascular risk among naïve subjects examining traditional risk factors, immunovirologic parameters, assessing the Framingham risk score (FRS), and detecting the presence of subclinical carotid lesions by means of color Doppler ultrasonography. One hundred seventy-two antiretroviral-naïve patients underwent color Doppler ultrasonography. An intima-media thickness (IMT) greater than 0.9 mm and/or atherosclerotic plaques were considered pathologic findings. Demographic, immunovirologic data, and risk factors for cardiovascular disease were collected. The 10-year probability of acute coronary events was assessed by the FRS. The statistical analysis was performed using t test and chi(2), Fisher's test, and conditional multiple logistic. Thirty-six patients (20.9%) had lesions at ultrasonographic investigation. The presence of lesions was significantly related to male gender (p = 0.005), age (p = 0.003), sedentary life (p = 0.05), Centers for Disease Control and Prevention (CDC) group C or CD4(+) less than 150 cells/mm(3), and viral load (VL) > 100,000 copies per milliliter (p = 0.04). The presence of subclinical carotid lesions showed a highly significant direct association with the estimated FRS (p < 0.002). The presence of subclinical atheromasic lesion results was also high among antiretroviral-naïve patients. FRS is highly predictive of the lesions, but also an advanced stage of disease plays a significant role. Our data support the hypothesis that HIV infection per se is a risk factor for atherosclerosis. We recommend an ultrasonographic assessment both among patients with FRS 6% or more and among those in advanced stage of disease.

Interleukin-2 cycling causes transient increases in high-sensitivity C-reactive protein and D-dimer that are not associated with plasma HIV-RNA levels

OBJECTIVE

To determine the effects of interleukin (IL)-2 treatment on inflammatory and thrombotic biomarkers in chronically HIV-infected adults receiving antiretroviral therapy.

METHODS

Cryopreserved plasma was evaluated retrospectively for C-reactive protein (CRP) and D-dimer at baseline, end of an IL-2 cycle, and long-term follow up from two randomized, controlled trials: 57 IL-2-naive adults receiving either three to six cycles of IL-2 as well as antiretroviral therapy (nucleoside analogues) or antiretroviral therapy alone for 12 months, and 40 IL-2-experienced adults on highly active antiretroviral therapy who either interrupted or continued therapy for 6 months after a baseline IL-2 cycle. High-sensitivity CRP (hsCRP) was measured by immunonephelometry (detection limit 0.175 mg/l) and D-dimer by latex agglutination (detection limit 0.20 mg/l). Median within-group differences and pre and post-IL-2 changes between groups were assessed via nonparametric Wilcoxon signed-rank and Mann-Whitney U-tests. Spearman's rank test was used to assess correlations between changes in hsCRP, D-dimer, and HIV-RNA viral load.

RESULTS

Significant increases in hsCRP (study 1: 138.6 mg/l; study 2: 58.9 mg/l) and D-dimer (study 1: 3.1 mg/l; study 2: 0.4 mg/l, all P < 0.0001) occurred by the end of the initial IL-2 cycle, returning to baseline by the end of study. No correlations were seen between changes in hsCRP or D-dimer and HIV-RNA, CD4 T-cell count, or proliferation (Ki67 expression). No thrombotic or cardiovascular serious adverse events occurred during these study periods.

CONCLUSION

IL-2 dosing caused transient increases in plasma hsCRP and D-dimer levels, regardless of HIV-RNA viral load, suggesting the possibility of increased risk for thrombotic events.

Plasma concentrations of the cardiovascular risk factor asymmetric dimethylarginine (ADMA) are increased in patients with HIV-1 infection and correlate with immune activation markers

OBJECTIVE

Higher concentrations of inflammation and immune activation markers as well as the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) are associated with an increased cardiovascular risk. In vitro, parallel formation of ADMA and macrophage marker neopterin was found in stimulated human peripheral blood mononuclear cells.

METHODS

In 112 HIV-1 infected patients, concentrations of ADMA, SDMA and arginine were compared to C-reactive protein and neopterin concentrations before they were referred to antiretroviral therapy. Disease activity was determined by viral load (qPCR), CD4(+) cell counts (FACS) and neopterin concentrations in plasma and urine (HPLC and ELISA). Additionally, concentrations of lipids were determined.

RESULTS

HIV-1 infected patients presented with increased neopterin, ADMA and SDMA concentrations, whereas CD4(+) counts and arginine and plasma lipid concentrations were low. ADMA and SDMA concentrations significantly correlated with markers of immune activation, but not with plasma lipids.

CONCLUSIONS

Results of this study indicate that increased ADMA and SDMA production may be related to an increased activity of immune activation pathways.