Jason V. Baker

Purpose of review This article describes the potential contribution of immune activation in the pathogenesis of HIV-associated cardiovascular disease (CVD) – a leading cause of morbidity and mortality among HIV-positive persons with access to antiretroviral therapy (ART). Recent findings We review recent literature that suggests abnormalities in both adaptive and innate immunity contributes to CVD risk among persons with HIV infection. In particular, potentially atherogenic T-cell mechanisms include persistent high-level T-cell activation (and associated proinflammatory mechanisms), as well as the presence of copathogens (e.g., cytomegalovirus) providing an ongoing stimulus for cytotoxic T-cell responses. More recent data have then emphasized the potential impact of monocyte-/macrophage-mediated inflammation and injury within atherosclerotic lesions. The abnormality driving innate immune activation many not fully reverse with antiretroviral therapy, highlighting the need for interventions that target inflammation as a CVD prevention strategy. Summary Premature CVD among persons with HIV infection is due, in part, to persistent abnormalities in immune activation and systemic inflammation despite viral suppression. Prevention strategies for persons with HIV infection include those that target traditional CVD risk factors, as well as newer candidate treatments with potential immunomodulatory benefits.

Background. Soluble biomarkers of inflammation predict non-AIDS related morbidity and mortality among human immunodeficiency virus (HIV)–infected persons. Exploring associations between plasma biomarkers and cellular phenotypes may identify sources of excess inflammation. Methods. Plasma biomarkers (interleukin 6 [IL-6] level, D-dimer level, high-sensitivity C-reactive protein [hsCRP] level, soluble CD14 [sCD14] level, and soluble CD163 [sCD163] level) were measured from cryopreserved samples from the Study to Understand the Natural History of HIV/AIDS in the Era of Effective Therapy (SUN Study). We performed immunophenotyping of peripheral blood mononuclear cells for markers of T-cell and monocyte activation, maturation, and migration. We evaluated associations between cellular phenotypes and soluble biomarkers by Spearman rank correlation and multivariate linear regression. Results. Participants' (n = 670) median age was 41 years, 88% were prescribed antiretroviral therapy, 72% had a plasma HIV RNA load of + T-lymphocyte count was 471 cells/µL. After adjustment, CD14⁺⁺CD16⁺ monocytes were associated with higher levels of IL-6, hsCRP, and sCD163; associations with IL-6 and hsCRP persisted in persons with suppressed HIV replication. While CCR5⁺ monocytes positively associated with D-dimer levels, CCR2⁺ monocytes were inversely associated with hsCRP levels. Conclusions. Plasma inflammatory biomarkers that predict morbidity and mortality were strongly associated with monocyte activation and migration, modestly associated with T-cell maturation, and not associated with CD8⁺ T-cell activation phenotypes. These findings suggest that strategies to control monocyte activation warrant further investigation.

Background: Identifying immunologic mechanisms that contribute to premature cardiovascular disease (CVD) among HIV-positive patients will inform prevention strategies. Methods: Coronary artery calcium (CAC) progression was studied in an HIV cohort. Immunophenotypes were measured on baseline cryopreserved peripheral blood mononuclear cells using multicolor flow cytometry. Logistic regression identified predictors of CAC progression after adjusting for traditional and HIV-related risk factors. Results: Baseline characteristics for the analysis cohort (n = 436) were median age 42 years, median CD4⁺ cell count 481 cells/μl, and 78% receiving antiretroviral therapy. Higher frequencies of CD16⁺ monocytes were associated with greater likelihood of CAC progression, after adjusting for traditional and HIV risk factors [odds ratio per doubling was 1.66 for CD14⁺/CD16⁺ (P = 0.02), 1.36 for CD14^dim/CD16⁺ (P = 0.06), and 1.69 for CD14^var/CD16⁺ (P = 0.01)]. Associations for CD16⁺ monocytes persisted when restricted to participants with viral suppression. We found no significant associations for CAC progression with other cellular phenotypes, including T-cell activation and senescence markers. Conclusion: Circulating CD16⁺ monocytes, potentially reflecting a more pro-atherogenic subpopulation, independently predicted greater CAC progression among HIV-infected persons at low risk for AIDS. In contrast to T-cell abnormalities classically associated with AIDS-related disease progression, these data highlight the potential role of monocyte activation in HIV-related CVD risk.

Background: Assessing whether hepatitis C (HCV) co-infection with human immunodeficiency virus (HIV) is associated with increased inflammation is complex. The liver, integral to inflammatory biomarker synthesis, is compromised by HCV and alcohol abuse. Using single liver-synthesized biomarkers (e.g. C-reactive protein) to represent inflammation may not be appropriate in HIV/HCV co-infection. We hypothesized that 1) detectable HIV/HCV RNA was independently associated with increased inflammation; 2) a composite inflammation measure describes inflammation differently from single inflammatory biomarkers.Methods: We compared inflammation by HIV/HCV group in a cohort of 361 HIV infected participants from the HIV-Longitudinal Interrelationships of Viruses and Ethanol study. Inflammatory biomarkers >75th percentile were considered elevated. Associations between HIV/HCV group and elevated biomarkers were analyzed as a composite measure (inflammatory burden) or individually. We defined inflammatory burden as number of concurrently elevated biomarkers. Biomarkers included interleukin-6 (IL-6), C-reactive protein (CRP), cystatin C, serum amyloid-A (SAA), tumor necrosis factor-alpha (TNF-α), interleukin-10 (IL-10). Covariates: alcohol, liver fibrosis, comorbidities, CD4 count, antiretroviral therapy, substance use.Results: Detectable HIV and HCV RNA (OR = 2.49; 95% CI = 1.05–5.89) and detectable HCV RNA alone (2.95; 1.08–8.01) were independently associated with increased odds of having a greater inflammatory burden compared to undetectable viremia. Elevated IL-10 (7.79; 1.90–31.97) and TNF-α (7.70; 1.42–41.83) were independently associated with detectable HIV and HCV RNA. Elevated IL-10 was also associated with detectable HCV RNA alone (5.51; 1.17, 25.84).Conclusions: Detectable HIV and HCV replication versus undetectable replication was associated with inflammatory burden and certain inflammatory biomarkers independently of alcohol consumption, liver fibrosis and other comorbidities.

Background: HIV infection leads to activation of coagulation, which may increase the risk for atherosclerosis and venous thromboembolic disease. We hypothesized that HIV replication increases coagulation potentially through alterations in extrinsic pathway factors. Methods and Results: Extrinsic pathway factors were measured among a subset of HIV participants from the Strategies for Management of Anti‐Retroviral Therapy ( SMART ) trial. Thrombin generation was estimated using validated computational modeling based on factor composition. We characterized the effect of antiretroviral therapy ( ART ) treatment versus the untreated state ( HIV replication) via 3 separate analyses: (1) a cross‐sectional comparison of those on and off ART (n=717); (2) a randomized comparison of deferring versus starting ART (n=217); and (3) a randomized comparison of stopping versus continuing ART (n=500). Compared with viral suppression, HIV replication consistently showed short‐term increases in some procoagulants (eg, 15% to 23% higher FVIII ; P P P <0.01 for all). The pattern of changes from HIV replication was reversed with ART treatment and consistent across all 3 independent comparisons. Conclusions: HIV replication leads to complex changes in extrinsic pathway factors, with the net effect of increasing coagulation potential to a degree that may be clinically relevant. The key influence of changes in FVIII and AT suggests that HIV ‐related coagulation abnormalities may involve changes in hepatocyte function in the context of systemic inflammation. Clinical Trial Registration: URL: ClinicalTrials.gov . Unique identifier: NCT 00027352.

Activation of coagulation pathways may contribute to risk for non–AIDS-related conditions among HIV-positive patients. Tissue factor (TF)–dependent procoagulant activity on circulating microparticles (MP-TF) in the plasma of 163 HIV-positive participants, both untreated and treated, with viral suppression was measured. MP-TF activity was 39% lower among treated versus untreated participants (P < 0.001), which persisted in adjusted models (−36%, P = 0.03). Among treated participants, MP-TF activity correlated modestly with D-dimer (r = 0.24, P = 0.01), von Willebrand factor (r = 0.36, P < 0.001), and interleukin-6 (r = 0.20, P = 0.04) levels. Future research should focus on mechanisms driving residual functional TF activity and whether these alterations have clinical consequences for non–AIDS-defining complications.

Treatments that reduce inflammation and cardiovascular disease (CVD) risk among individuals with HIV infection receiving effective antiretroviral therapy (ART) are needed. We conducted a 2×2 factorial feasibility study of lisinopril (L) (10 mg daily) vs L-placebo in combination with pravastatin (P) (20 mg daily) vs P-placebo among participants receiving ART with undetectable HIV RNA levels, a Framingham 10 year risk score (FRS) ≥3%, and no indication for ACE-I or statin therapy. Tolerability and adherence were evaluated. Longitudinal mixed models assessed changes in blood pressure (BP), blood lipids, and inflammatory biomarkers from baseline through months 1 and 4. Thirty-seven participants were randomized and 34 [lisinopril/pravastatin (n = 9), lisinopril/P-placebo (n = 8), L-placebo/pravastatin (n = 9), L-placebo/P-placebo (n = 8)] attended at least one follow-up visit. Participants were 97% male, 41% white, 67% were current smokers, and 65% were taking a protease inhibitor. Median age was 48 years, CD4 count 483 cells/mm³, FRS 7.79%, total cholesterol 184 mg/dL, and LDL-C 95 mg/dL. There was no treatment difference for pravastatin vs P-placebo in total cholesterol, LDL-C, or any of the inflammatory biomarkers. Participants randomized to lisinopril vs. L-placebo had significant declines in diastolic BP (−3.3 mmHg, p = 0.05), hsCRP (−0.61 µg/mL, p = 0.02) and TNF-α (−0.17 pg/mL, p = 0.04). Participants taking lisinopril vs L-placebo were more likely to report missed doses (88 vs 35%; p = 0.001) and have adherence <90% by pill count (42 vs. 0%; p = 0.02). Few participants from either group reported side effects (n = 3 vs. n = 1). The modest BP changes and decreased adherence with lisinopril and absence of lipid differences with pravastatin suggest future studies of these drug classes should consider a run-in period to assess adherence and use a different statin. Our results also indicate that ACE-I therapy may have anti-inflammatory benefits for ART-treated persons with HIV infection and this should be further evaluated. ClinicalTrials.gov NCT00982189

Background: HIV infection is associated with premature development of cardiovascular disease. Understanding the effects of HIV replication on endothelial dysfunction and platelet activation may identify treatment targets to reduce cardiovascular disease risk. Methods: A subgroup of HIV-infected participants in the Strategies for Management of Antiretroviral Therapy study off antiretroviral therapy (ART) at entry enabled a randomized comparison of immediate versus deferred ART initiation of changes in asymmetric dimethylarginine (ADMA), soluble CD40 ligand (sCD40L), and P-selectin levels. Results: At study entry, median (interquartile range) levels of ADMA, sCD40L, and P-selectin were 0.57 (0.49–0.66) μg/mL, 251 (135–696) μmol/L, and 34 (28–44) pg/mL. Compared to those randomized to deferral of ART (n = 114), participants randomized to immediate ART (n = 134) had 10.3% lower ADMA levels (P = 0.003) at 12 months; treatment differences in sCD40L (95% confidence interval: −17% to 44%; P = 0.53) and P-selectin (95% confidence interval: −10% to 10%; P = 0.95) were not significant. The difference in ADMA for those assigned immediate ART compared with those assigned ART deferral was greater among younger patients and those with higher levels of high-sensitivity C-reactive protein and D-dimer (P ≤ 0.05 for interaction for both) but not HIV RNA level at baseline (P = 0.51). Discussion ART initiation leads to declines in ADMA levels, a marker of nitric oxide–mediated endothelial dysfunction. Improvement in ADMA levels was related to the degree of inflammation and coagulation, suggesting that upregulation of these pathways contributes to premature vascular disease among individuals with HIV infection. Whether declines in ADMA levels impact risk of disease requires further research.