Platelet function and HIV: a case-control study

Association of Antiretroviral Therapy with Platelet Function and Systemic Inflammatory Response in People Living with HIV: A Cross-Sectional Study

People living with HIV (PLWHIV) present an increased risk of adverse cardiovascular events. We aimed to assess whether antiretroviral therapy (ART) pharmacologically enhances platelet reactivity and platelet activation intensity, and explore the potential association with underlying inflammatory status. This was a cross-sectional cohort study carried out among PLWHIV on diverse ART regimens. Platelet reactivity and activation intensity were assessed using the bedside point-of-care VerifyNow assay, in P2Y12 reaction units (PRU), measurements of monocyte-platelet complexes, and P-selectin and GPIIb/IIIa expression increase, following activation with ADP, respectively. Levels of major inflammatory markers and whole blood parameters were also evaluated. In total, 71 PLWHIV, 59 on ART and 22 healthy controls, were included in this study. PRU values were significantly elevated in PLWHIV compared to controls [Mean; 257.85 vs. 196.67, p < 0.0001], but no significant differences were noted between ART-naïve or ART-experienced PLWHIV, or between TAF/TDF and ABC based regimens, similar to systemic inflammatory response. However, within-group analysis showed that PRUs were significantly higher in ABC/PI vs ABC/INSTI or TAF/TDF + PI patients, in line with levels of IL-2. PRU values did not correlate strongly with CD4 counts, viral load, or cytokine values. P-selectin and GPIIb/IIIa expression increased following ADP activation and were significantly more prominent in PLWHIV (p < 0.005). Platelet reactivity and platelet activation intensity were shown to be increased in PLWHIV, but they did not appear to be related to ART initiation, similar to the underlying systemic inflammatory response.

Changes in Coagulation and Platelet Reactivity in People with HIV-1 Switching Between Abacavir and Tenofovir

Background:

Several studies have shown an association between abacavir (ABC) and increased risk of myocardial infarction (MI), but the causative mechanism has not been established. Both vascular endothelial inflammation and platelet activation have been proposed as contributing factors.

Objective:

The study aims to investigate the effects of ABC relative to tenofovir disoproxil (TDF) on functional assays of primary and secondary hemostasis and a comprehensible range of relevant biomarkers.

Methods:

In an investigator-initiated, open-labeled, crossover trial, we included HIV-infected males receiving either ABC or TDF and switched treatment to the alternate drug. At inclusion and after three months on the new regimen, we performed Multiplate® and thromboelastography (TEG®) and measured biomarkers of coagulation, inflammation, platelet reactivity, endothelial disruption and activation, and fibrinolysis, lipids, HIV RNA, CD4, CD8, and creatinine. Treatment effects were assessed by comparing intraindividual differences between the two treatment orders by the Wilcoxon Rank Sum test.

Results:

In total, 43 individuals completed the study. No intraindividual differences were observed for Multiplate® or TEG® when switching between regimens. We observed a significant treatment effect on coagulation factors II-VII-X (p<0.0001), sCD40L (a biomarker of platelet reactivity, p=0.04), thrombomodulin (biomarker of endothelial damage, p=0.04), lipids, and CD8 cell counts (p=0.04), with higher values during ABC treatment compared to TDF.

Conclusion:

Compared to TDF, ABC treatment affected several outcome measures in a pro-coagulant direction. Suggesting that the risk of MI associated with ABC may be caused by the sum of multiple, discrete disturbances in the hemostatic system and endothelium.

Study Registration:

The trial was registered at clinicaltrials.gov (NCT02093585).

Challenges in Platelet Functions in HIV/AIDS Management

The interest in platelet functions in HIV/AIDS is due to the high incidence of microvascular thrombosis in these individuals. A lot of laboratory data have been generated regarding platelet functions in this population. The tests demonstrate platelet hyperactivity but decreased aggregation, though results are inconsistent depending on the study design. Antiretroviral treatments currently in use display complex interactions. Many studies on platelet functions in these patients have been for research purposes, but none have found utility in guiding drug treatment of thrombosis.

Long-term treated HIV infection is associated with platelet mitochondrial dysfunction

HIV infection and antiretroviral therapy have been linked to mitochondrial dysfunction. The role of platelet mitochondrial dysfunction in thrombosis, immunoregulation and age-related diseases is increasingly appreciated. Here, we studied platelet mitochondrial DNA content (mtDNA_pl) and mitochondrial function in people living with HIV (PLHIV) and related this to platelet function. In a cohort of 208 treated PLHIV and 56 uninfected controls, mtDNA_pl was quantified, as well as platelet activation, platelet agonist-induced reactivity and inflammation by circulating factors and flow cytometry. In a subgroup of participants, the metabolic activity of platelets was further studied by mitochondrial function tests and the Seahorse Flux Analyzer. PLHIV had significantly lower mtDNA_pl compared to controls (8.5 copies/platelet (IQR: 7.0–10.7) vs. 12.2 copies/platelet (IQR: 9.5–16.6); p < 0.001), also after correction for age, sex and BMI. Prior zidovudine-use (n = 46) was associated with a trend for lower mtDNA_pl. PLHIV also had reduced ex vivo platelet reactivity and mean platelet volume compared to controls. MtDNA_pl correlated positively with both platelet parameters and correlated negatively with inflammatory marker sCD163. Mitochondrial function tests in a subgroup of participants confirmed the presence of platelet mitochondrial respiration defects. Platelet mitochondrial function is disturbed in PLHIV, which may contribute to platelet dysfunction and subsequent complications. Interventions targeting the preservation of normal platelet mitochondrial function may ultimately prove beneficial for PLHIV.

Platelet activation in adult HIV-infected patients on antiretroviral therapy: a systematic review and meta-analysis

BACKGROUND

Antiretroviral therapy (ART) alters platelet reactivity, and as a consequence, patients living with HIV may be at an increased risk of cardiovascular disease (CVD). The current evidence on platelet activation levels in patients with HIV remains inconclusive. We therefore aimed to systematically synthesise evidence on the association of platelet activation in HIV-infected patients on successful treatment.

METHODS

Electronic databases were searched from inception until November 2019. Studies were included if the primary or secondary outcome of the study was to assess platelet activation in HIV-infected patients on ART. The primary outcome of this review included the levels of platelet activation. The pooled effect estimates were calculated using a random-effects meta-analysis model.

RESULTS

We identified 30 studies comprising of 2325 participants. The pooled estimates showed elevated levels of platelet activation in treatment-naïve HIV-infected patients compared to uninfected controls (Hedges' g 2.00 [95%CI 1.05, 2.94]; z = 4.12, p < 0.0001). These remained elevated despite successful ART (Hedges' g 2.05 [95%CI 0.58, 3.52]; z = 2.71, p = 0.0067).

CONCLUSION

The levels of platelet activation are elevated in treatment-naïve HIV-infected patients, and these persist during successful ART. Further studies should assess the clinical relevance of monitoring the levels of platelet activation in HIV-infected patients on ART.

HIV Antivirals Affect Endothelial Activation and Endothelial-Platelet Crosstalk

RATIONALE

People living with HIV on effective antiretroviral therapy are at increased risk of cardiovascular complications, possibly due to off-target drug effects. Some studies have associated antiretroviral therapy with increased risk of myocardial infarction and endothelial dysfunction, but a link between endothelial function and antiretrovirals has not been established.

OBJECTIVE

To determine the effects of antiretrovirals in common clinical use upon in vitro endothelial function to better understand cardiovascular risk in people living with HIV.

METHODS AND RESULTS

Human umbilical cord vein endothelial cells or human coronary artery endothelial cells were pretreated with the antiretrovirals abacavir sulphate (ABC), tenofovir disoproxil fumarate, or tenofovir alafenamide. Expression of adhesion molecules, ectonucleotidases (CD39 and CD73), tissue factor (TF), endothelial-derived microparticle (EMP) numbers and phenotype, and platelet activation were evaluated by flow cytometry. TF and ectonucleotidase activities were measured using colourimetric plate-based assays. ABC-treated endothelial cells had higher levels of ICAM (intercellular adhesion molecule)-1 and TF expression following TNF (tumor necrosis factor)-α stimulation. In contrast, tenofovir disoproxil fumarate and tenofovir alafenamide treatment gave rise to greater populations of CD39⁺CD73⁺ cells. These cell surface differences were also observed within EMP repertoires. ABC-treated cells and EMP had greater TF activity, while tenofovir disoproxil fumarate- and tenofovir alafenamide-treated cells and EMP displayed higher ectonucleotidase activity. Finally, EMP isolated from ABC-treated cells enhanced collagen-evoked platelet integrin activation and α-granule release.

CONCLUSIONS

We report differential effects of antiretrovirals used in the treatment of HIV upon endothelial function. ABC treatment led to an inflammatory, prothrombotic endothelial phenotype that promoted platelet activation. In contrast, tenofovir disoproxil fumarate and tenofovir alafenamide conferred potentially cardioprotective properties associated with ectonucleotidase activity. These observations establish a link between antiretrovirals and specific functional effects that provide insight into cardiovascular disease in people living with HIV.

Effects of gut microbial metabolite trimethylamine N-oxide (TMAO) on platelets and endothelial cells

Thrombotic events result from different pathologies and are the underlying causes of severe diseases like stroke or myocardial infarction. Recent basic research now revealed a link between food uptake, food conversion and gut metabolism. Gut microbial production of trimethylamine N-oxide (TMAO) from dietary nutrients like choline, lecithin and L-carnitine was associated with the development of cardiovascular diseases. Within this review we give a systematic overview about the influence of TMAO on blood components like platelets and endothelial cells which both are involved as key players in thrombotic processes. In summary, a mechanistic correlation between the gut microbiome, TMAO and cardiovascular diseases becomes obvious and emphasizes to the significance of the intestinal microbiome.

Increased levels of reactive oxygen species in platelets and platelet-derived microparticles and the risk of respiratory failure in HIV/AIDS patients

Respiratory failure (RF) is the main cause of hospital admission in HIV/AIDS patients. This study assessed comorbidities and laboratory parameters in HIV/AIDS inpatients with RF (N = 58) in relation to those without RF (N = 36). Tuberculosis showed a huge relative risk and platelet counts were slightly higher in HIV/AIDS inpatients with RF. A flow cytometry assay for reactive oxygen species (ROS) showed lower levels in platelets of these patients in relation to the healthy subjects. However, when stimulated with adrenaline, ROS levels increased in platelets and platelet-derived microparticles of HIV/AIDS inpatients, which may increase the risk of RF during HIV and tuberculosis (HIV-TB) coinfection.

Platelet gene expression and function in patients with COVID-19

There is an urgent need to understand the pathogenesis of coronavirus disease 2019 (COVID-19). In particular, thrombotic complications in patients with COVID-19 are common and contribute to organ failure and mortality. Patients with severe COVID-19 present with hemostatic abnormalities that mimic disseminated intravascular coagulopathy associated with sepsis, with the major difference being increased risk of thrombosis rather than bleeding. However, whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection alters platelet function to contribute to the pathophysiology of COVID-19 remains unknown. In this study, we report altered platelet gene expression and functional responses in patients infected with SARS-CoV-2. RNA sequencing demonstrated distinct changes in the gene-expression profile of circulating platelets of COVID-19 patients. Pathway analysis revealed differential gene-expression changes in pathways associated with protein ubiquitination, antigen presentation, and mitochondrial dysfunction. The receptor for SARS-CoV-2 binding, angiotensin-converting enzyme 2 (ACE2), was not detected by messenger RNA (mRNA) or protein in platelets. Surprisingly, mRNA from the SARS-CoV-2 N1 gene was detected in platelets from 2 of 25 COVID-19 patients, suggesting that platelets may take-up SARS-COV-2 mRNA independent of ACE2. Resting platelets from COVID-19 patients had increased P-selectin expression basally and upon activation. Circulating platelet-neutrophil, -monocyte, and -T-cell aggregates were all significantly elevated in COVID-19 patients compared with healthy donors. Furthermore, platelets from COVID-19 patients aggregated faster and showed increased spreading on both fibrinogen and collagen. The increase in platelet activation and aggregation could partially be attributed to increased MAPK pathway activation and thromboxane generation. These findings demonstrate that SARS-CoV-2 infection is associated with platelet hyperreactivity, which may contribute to COVID-19 pathophysiology.

Pharmacological impact of antiretroviral therapy on platelet function to investigate human immunodeficiency virus-associated cardiovascular risk

BACKGROUND AND PURPOSE

Some clinical studies have reported increased myocardial infarction in people living with human immunodeficiency virus (HIV) taking the antiretroviral abacavir sulphate (ABC). Given that clinical studies contain confounding variables (e.g., HIV-associated factors), we investigated the pharmacological effects of antiretrovirals on platelet function in HIV-negative volunteers in order to identify mechanisms of increased cardiovascular risk.

EXPERIMENTAL APPROACH

Platelets were isolated from healthy volunteers and HIV-negative subjects enrolled on a Phase I clinical trial and platelet function evaluated using aggregometry and flow cytometry. In vivo platelet thromboembolism was monitored in anaesthetized mice.

KEY RESULTS

Human platelet aggregation was unaffected by all antiretrovirals tested, but ABC treatment led uniquely to increased platelet granule release. ABC also interrupted NO-mediated inhibition of platelet aggregation and increased in vivo aggregation in mice. Another antiretroviral, tenofovir, did not affect platelet function. Furthermore, aggregation and activation of platelets isolated from 20 subjects taking clinically relevant doses of tenofovir were comparable to baseline samples.

CONCLUSIONS AND IMPLICATIONS

ABC can enhance platelet activation, independently of variables that confound clinical studies, suggesting a potential pharmacological effect that is absent with tenofovir. Mechanistically, we propose that ABC enhances platelet degranulation and interrupts NO-mediated platelet inhibition. The interaction of ABC with NO signalling is demonstrated by ABC-mediated enhancement of aggregation in vivo and in vitro that persisted in the presence of NO. Although an association between ABC and platelet activation has not been confirmed in patients, these findings provide evidence of a mechanistic link between platelet activation and antiretroviral therapy.

A switch to a raltegravir containing regimen does not lower platelet reactivity in HIV-infected individuals

OBJECTIVE

Platelet hyperreactivity and increased platelet-monocyte aggregation (PMA) are associated with increased cardiovascular risk and inflammation. In a previous cross-sectional study, individuals using a raltegravir (RAL)-based regimen were found to have reduced platelet reactivity and PMA compared with other antiretroviral regimens. Our aim was to investigate whether switching from a nonintegrase inhibitor regimen to a RAL-based regimen reduces platelet reactivity or PMA.

DESIGN

An investigator initiated, single-centre, prospective randomized, open-label, blinded endpoint trial.

METHODS

Forty HIV-infected adults using a nonintegrase inhibitor containing regimen with undetectable viral load were randomized to either continue their regimen or switch to a RAL-based regimen for 10 weeks, continuing the same backbone. The primary outcome was the change in platelet reactivity at week 10, which was determined as the expression of the platelet activation marker P-selectin and binding of fibrinogen before and after ex-vivo stimulation with different platelet agonists. Secondary outcomes included PMA, plasma markers of platelet activation and markers of inflammation and immune cell activation.

RESULTS

Twenty-one participants were enrolled in the continuation group and 19 in the RAL group. Baseline characteristics were comparable between groups. There were no differences in the change in platelet reactivity to either platelet agonist at week 10, nor in plasma markers of platelet activation. PMA, C-reactive protein, T-cell activation (CD38HLA-DR) and monocyte (CD14CD16) subsets.

CONCLUSION

Switching a nonintegrase inhibitor containing regimen to a RAL-based regimen does not reduce platelet reactivity, platelet-leukocyte aggregation, inflammation and immune activation in virologically suppressed HIV-infected individuals.

CLINICAL TRIAL NUMBER

NCT02383355.

Platelet Transcriptome Profiling in HIV and ATP-Binding Cassette Subfamily C Member 4 (ABCC4) as a Mediator of Platelet Activity

An unbiased platelet transcriptome profile identified ATP binding cassette subfamily C member 4 (ABCC4) as a novel mediator of platelet activity in virologically suppressed human immunodeficiency virus (HIV)-infected subjects on antiretroviral therapy. Using ex vivo and in vitro cellular and molecular assays we demonstrated that ABCC4 regulated platelet activation by altering granule release and cyclic nucleotide homeostasis through a cAMP-protein kinase A (PKA)-mediated mechanism. Platelet ABCC4 inhibition attenuated platelet activation and effector cell function by reducing the release of inflammatory mediators, such as sphingosine-1-phosphate. ABCC4 inhibition may represent a novel antithrombotic strategy in HIV-infected subjects on antiretroviral therapy.

Quantitative angiographic characterisation of coronary artery disease in patients with human immunodeficiency virus (HIV) infection undergoing percutaneous coronary intervention

AIMS

Patients with human immunodeficiency virus (HIV) infection have an increased risk of acute myocardial infarction (MI), and 6.5-15% of mortality in this population is attributable to cardiovascular disease. However, the angiographic pattern of coronary artery disease (CAD) in patients with HIV undergoing percutaneous coronary intervention (PCI) remains unknown. We sought to assess and describe the angiographic features and burden of CAD in patients with HIV as compared to those without HIV infection.

METHODS AND RESULTS

This is a retrospective, single-centre study comparing 93 patients with HIV infection who underwent PCI between 2003 and 2011 with 93 control patients without HIV infection matched for age (±3 years), gender, diabetes, and year of PCI (±2 years). Quantitative coronary angiography (QCA) was performed for all treated lesions at baseline and following PCI in both groups. One-year clinical outcomes post PCI were also analysed and compared. The mean age for both study populations was 57 years; patients with HIV were more likely to present with ST-segment elevation myocardial infarction (STEMI). Patients had a similar extent of CAD as measured by the presence of multivessel disease as well as SYNTAX score; however, patients with HIV were more likely to have lesions in the proximal segment of the respective coronary artery. While both groups mostly displayed none/mild calcified lesions, HIV+ patients had longer and fewer stenotic lesions. Clinical outcomes at one year were similar.

CONCLUSIONS

While HIV+ patients were more likely to present with STEMI, detailed coronary angiographic analysis revealed less complex lesions and favourable anatomy. This paradox may suggest alterations in genesis and progression of atherosclerosis in this clinical setting.

Short-term in vivo modifications of platelet NADPH oxidase 2 (NOX2) and prostaglandin F2α in HIV-1 patients on abacavir-based therapies

OBJECTIVES

The aim of the study was to investigate the in vivo effect of abacavir (ABC) on platelet oxidative stress.

METHODS

We performed a randomized pilot study including 39 HIV-1-infected patients, 17 on zidovudine/lamivudine (ZDV/3TC) and 22 on tenofovir/emtricitabine (TDF/FTC). Ten patients on ZDV/3TC and eight patients on TDF/FTC were randomly allocated to switching the nucleoside backbone to ABC/3TC. At baseline and after 6 months, platelet oxidative stress was assessed by platelet NADPH oxidase 2 (NOX2)-derived peptide (sNOX2-dp), a marker of NOX2 activation, and platelet prostaglandin F_2α (8-iso-PGF_2α ). Platelet activation was measured by soluble CD40L (sCD40L).

RESULTS

At baseline, no differences between ZDV/3TC or TDF/FTC recipients were found. After 6 months, patients switching from ZDV/3TC showed a decrease of sNOX2-dp (from 20.9±5.7 to 12.5±3.8 pg/ml, p=0.002) and 8-iso-PGF_2α (from 154.3±41.9 to 122.9±28.0 pmol/l, p=0.025). No effects on platelet oxidative stress biomarkers were observed in subjects from TDF/FTC, who showed a significant increase in blood glucose (p=0.043) and total cholesterol (p=0.027). ABC showed no effect on sCD40L levels in both groups.

CONCLUSIONS

ABC reduced platelet sNOX2-dp and 8-iso-PGF_2α in HIV-1 subjects switching from ZDV/3TC but not in those from TDF/FTC after 6 months. No changes in platelet activation were found in both groups.

Microbiota-dependent metabolite and cardiovascular disease marker trimethylamine-N-oxide (TMAO) is associated with monocyte activation but not platelet function in untreated HIV infection

Background

HIV infection is associated with increased risk of cardiovascular disease beyond that explained by traditional risk factors. Altered gut microbiota, microbial translocation, and immune activation have been proposed as potential triggers. The microbiota-dependent metabolite trimethylamine-N-oxide (TMAO) predicts myocardial infarction (MI) in the general population and has recently been shown to induce platelet hyperreactivity. In the present study, we investigated if TMAO was associated with platelet function, microbial translocation, and immune activation in both untreated and combination anti-retroviral therapy (cART) HIV infection.

Methods

TMAO and the pre-cursors betaine, choline, and carnitine were quantified by mass-spectrometry in plasma samples from a previously established cross-sectional cohort of 50 untreated and 50 cART treated HIV-infected individuals. Whole-blood impedance aggregometry, C-reactive protein, sCD14, and lipopolysaccharide were assessed as measures of platelet function, inflammation, monocyte activation, and microbial translocation, respectively.

Results

TMAO was not associated with platelet aggregation response after stimulation with four different agonists, or with overall hypo- or hyperreactivity in untreated or treated HIV-infected individuals. In contrast, sCD14 a marker of both monocyte activation and microbial translocation was independently associated with TMAO in untreated HIV-infection (R = 0.381, P = 0.008). Lower levels of carnitine [32.2 (28.4–36.8) vs. 38.2 (33.6–42.0), P = 0.001] and betaine [33.1 (27.3–43.4) vs.37.4 (31.5–48.7, P = 0.02], but similar TMAO levels [3.8 (2.3–6.1), vs. 2.9 μM (1.9–4.8) P = 0.15] were found in cART treated compared to untreated HIV-infected individuals, resulting in higher ratios of TMAO/carnitine [0.12 (0.07–0.20) vs. 0.08 (0.05–0.11), P = 0.02] and TMAO/betaine [0.11 (0.07–0.17) vs. 0.08 (0.05–0.13), P 0.02].

Conclusions

In contrast to recent studies in HIV-uninfected populations, the present study found no evidence of TMAO-induced platelet hyperreactivity in HIV infected individuals. Microbial translocation and monocyte activation may affect TMAO levels in untreated individuals. Furthermore, the elevated ratios of TMAO/betaine and TMAO/carnitine in cART-treated individuals could possibly suggest a role of cART in TMAO metabolism.

Cardiovascular disease in patients with HIV

With the progressive increase in life expectancy of HIV-positive patient, thanks to "highly active antiretroviral therapy" (HAART), new comorbidities, and especially cardiovascular diseases (CVDs) are emerging as an important concern. An increased risk of coronary artery disease, often in a younger age, has been observed in this population. The underlying pathophysiology is complex and partially still unclear, with the interaction of viral infection-and systemic inflammation-antiretroviral therapy and traditional risk factors. After an accurate risk stratification, primary prevention should balance the optimal HAART to suppress the virus-avoiding side-effects-the intervention on life-style and the treatment of traditional risk factors (hypertension, dyslipidemia, and diabetes). Also the management after a cardiovascular event is challenging: revascularization strategies-both percutaneous and surgical-are valuable options, keeping in mind the higher rates of recurrent events, and caution is essential to avoid drug-drug interactions. Large evidence-based data on HIV-infected patients are still lacking, and recommendations often follow those of general population. Therefore we performed a comprehensive evaluation of the literature to analyze the current knowledge on CVD's prevalence, prevention and treatment in HIV-infected patients.

Abacavir has no prothrombotic effect on platelets in vitro

OBJECTIVES

HIV patients exposed to abacavir have an increased risk of myocardial infarction, with contradictory results in the literature. The aim of our study was to determine whether abacavir has a direct effect on platelet activation and aggregation using platelets from healthy donors and from HIV-infected patients under therapy with an undetectable viral load.

METHODS

Platelet-rich plasma (PRP) or whole blood from healthy donors was treated with abacavir (5 or 10 μg/mL) or its active metabolite carbovir diphosphate. Experiments were also performed using blood of HIV-infected patients (n = 10) with an undetectable viral load. Platelet aggregation was performed on PRP by turbidimetry and under high shear conditions at 4000 s^-1. Platelet procoagulant potential was analysed by measuring thrombin generation by thrombinography.

RESULTS

Abacavir and carbovir diphosphate significantly increased the aggregation of platelets from healthy donors induced by collagen at 2 μg/mL (P = 0.002), but not at 0.5 μg/mL. No effect of abacavir or carbovir diphosphate was observed on platelet aggregation induced by other physiological agonists or by high shear stress, or on thrombin generation. Pretreatment of blood from HIV-infected patients with abacavir produced similar results.

CONCLUSIONS

Our results suggest that abacavir does not significantly influence platelet activation in vitro when incubated with platelets from healthy donors or from HIV-infected patients. It is, however, not excluded that a synergistic effect with other drugs could promote platelet activation and thereby play a role in the pathogenesis of myocardial infarction.

Modeling HIV-1 Induced Neuroinflammation in Mice: Role of Platelets in Mediating Blood-Brain Barrier Dysfunction

The number of HIV-1 positive individuals developing some form of HIV-associated neurocognitive disorder (HAND) is increasing. In these individuals, the integrity of the blood-brain barrier (BBB) is compromised due to an increase in exposure to pro-inflammatory mediators, viral proteins, and virus released from infected cells. It has been shown that soluble CD40L (sCD40L) is released upon platelet activation and is an important mediator of the pathogenesis of HAND but the underlying mechanisms are unclear, emphasizing the need of an effective animal model. Here, we have utilized a novel animal model in which wild-type (WT) mice were infected with EcoHIV; a derivative of HIV-1 that contains a substitution of envelope protein gp120 with that of gp80 derived from murine leukemia virus-1 (MuLV-1). As early as two-weeks post-infection, EcoHIV led to increased permeability of the BBB associated with decreased expression of tight junction protein claudin-5, in CD40L and platelet activation-dependent manner. Treatment with an antiplatelet drug, eptifibatide, in EcoHIV-infected mice normalized BBB function, sCD40L release and platelet activity, thus implicating platelet activation and platelet-derived CD40L in virally induced BBB dysfunction. Our results also validate and underscore the importance of EcoHIV infection mouse model as a tool to explore therapeutic targets for HAND.

HIV Infection and Primary Prevention of Cardiovascular Disease: Lights and Shadows in the HAART Era

With the progressive increase in life-expectancy of human immunodeficiency virus (HIV)-positive patients in the "highly active antiretroviral therapy" (HAART) era, co-morbidities, particularly cardiovascular (CV) diseases (CVD) are emerging as an important concern. The pathophysiology of CVD in this population is complex, due to the interaction of classical CV risk factors, viral infection and the effects of antiretroviral therapy (ARV). The role of ARV drugs in HIV is double edged. While these drugs reduce systemic inflammation, an important factor in CV development, they may at the same time be proatherogenic by inducing dyslipidemia, body fat redistribution and insulin resistance. In these patients primary prevention is challenging, considering the lower median age at which acute coronary syndromes occur. Furthermore prevention is still limited by the lack of robust evidence-based, HIV-specific recommendations. Therefore we performed a comprehensive evaluation of the literature to analyze current knowledge on CVD prevalence in HIV-infected patients, traditional and HIV-specific risk factors and risk stratification, and to summarize the recommendations for primary prevention of CVD in this HIV population.

Immune activation in the course of HIV-1 infection: Causes, phenotypes and persistence under therapy

Systemic immune activation is a striking consequence of HIV-1 infection. Even in virologically suppressed patients, some hyperactivity of the immune system and even of the endothelium and of the coagulation pathway may persist. Apart from immune deficiency, this chronic activation may contribute to various morbidities including atherothrombosis, neurocognitive disorders, liver steatosis and osteoporosis, which are currently main challenges. It is therefore of major importance to better understand the causes and the phenotypes of immune activation in the course of HIV-1 infection. In this review we will discuss the various causes of immune activation in HIV-1 infected organisms: the presence of the virus together with other microbes, eventually coming from the gut, CD4+ T cell lymphopenia, senescence and dysregulation of the immune system, and/or genetic factors. We will also describe the activation of the immune system: CD4+ and CD8+ T cells, B cells, NKT and NK cells, dendritic cells, monocytes and macrophages, and neutrophils of the inflammation cascade, as well as of the endothelium and the coagulation system. Finally, we will see that antiretroviral therapy reduces the hyperactivity of the immune and coagulation systems and the endothelial dysfunction, but often does not abolish it. A better knowledge of this phenomenon might help us to identify biomarkers predictive of non AIDS-linked comorbidities, and to define new strategies aiming at preventing their emergence.

Thromboelastography on plasma reveals delayed clot formation and accelerated clot lyses in HIV-1 infected persons compared with healthy controls

Background

Thromboembolic events among HIV infected persons are a recognized clinical problem but the underlying mechanisms are poorly understood. To assess whether coagulation and fibrinolysis differ between long-term treated HIV infected individuals (HIV+) and healthy controls (CON), we investigated functional plasma coagulation by thrombelastography (TEG) and plasma markers of endothelial and platelet activation.

Methods

In 67 successfully long-term treated HIV+ and 15 CON we analyzed stored plasma samples by TEG, with or without addition of tissue-type plasminogen activator (tPA), and measured levels of C-reactive protein, thrombomodulin, syndecan-1, sVE-cadherin, soluble CD40 ligand (sCD40L), adrenaline and noradrenaline.

Results

Compared to CON, HIV+ had delayed clot formation (reaction (R)-time 14.2 min. vs. 11.2 min., p = 0.0004) and reduced clot formation rapidity (angle 22.6° vs. 48.6 °, p = <0.0001). Clot lyses induced by tPA was accelerated in HIV+ displaying enhanced clot degradation after 30 and 60 min (53.9 % vs. 24.2 %, p < 0.0001 and 77.4 % vs. 59.9 %, p < 0.0001, respectively). sCD40L and TEG R-time correlated negatively in both HIV+ and CON (Rho =−0.502, p < 0.001 and rho =−0.651, p = 0.012).

Discussion

No previous studies have examined plasma coagulation by TEG in HIV, however, we have previously demonstrated that HIV+ display hypocoagulability in whole blood by TEG in accordance with the results of this study. Others have reported of HIV associated changes in the hemostatic system in a pro-coagulant direction based on measurements of isolated components of the coagulation pahways. In disease conditions, the flowing blood may change from “normal” to hyper- or hypocoagulant or to hyper- or hypofibrinolytic. A balance may exist in the flowing blood, i.e. between blood cells and the plasma phase, so that pro-coagulant blood cells are balanced by a hypocoagulable plasma phase; thus alterations that may promote thromboembolic events in the patient may at the same time appear as a hypocoagulable profile when evaluated in vitro.

Conclusion

Plasma from long-term treated HIV infected persons displays a hypocoagulable profile with reduced fibrinolytic resistance as compared to healthy controls.

Cancer prevention in HIV-infected populations

People living with human immunodeficiency virus (HIV) are living longer since the advent of effective combined antiretroviral therapy (cART). While cART substantially decreases the risk of developing some cancers, HIV-infected individuals remain at high risk for Kaposi sarcoma, lymphoma, and several solid tumors. Currently HIV-infected patients represent an aging group, and malignancies have become a leading cause of morbidity and mortality. Tailored cancer-prevention strategies are needed for this population. In this review we describe the etiologic agents and pathogenesis of common malignancies in the setting of HIV, as well as current evidence for cancer prevention strategies and screening programs.

The effect of initiation of antiretroviral therapy on monocyte, endothelial and platelet function in HIV-1 infection

OBJECTIVES

Monocyte activation, endothelial dysfunction and platelet activation all potentially contribute to the increased risk of cardiovascular disease (CVD) reported in those with HIV-1 infection. To date, no study has examined how initiation of antiretroviral therapy (ART) affects markers of all three processes. We aimed to compare markers of monocyte, endothelial and platelet function between untreated HIV-positive subjects and HIV-negative controls and to examine the early effects of ART initiation on these markers.

METHODS

We measured monocyte [soluble CD14 (sCD14) and sCD163], endothelial [von Willebrand factor (vWF), intercellular adhesion molecule-1 (ICAM-1) and vascular adhesion molecule-1 (VCAM-1)] and platelet [soluble P-selectin (sP-selectin), soluble CD40 ligand (sCD40L) and soluble glycoprotein VI (sGPVI)] biomarkers before and at weeks 4 and 12 post ART initiation in HIV-positive and well-matched HIV-negative controls.

RESULTS

We examined 40 subjects, 25 HIV-positive subjects and 15 controls, with a median age of 34 years [interquartile range (IQR) 31, 40 years], of whom 60% were male and 47.5% Caucasian. Pre-ART, all biomarkers (monocyte, endothelial and platelet) were significantly higher in HIV-positive patients versus controls (all P < 0.05) and decreased with ART initiation, except for sCD14, which remained unchanged [median 1680 (IQR 1489, 1946) ng/mL at week 12 versus 1570 (IQR 1287, 2102) ng/mL at week 0; P = 0.7]. Although platelet activation markers reduced to levels comparable to those in controls, endothelial dysfunction markers remained elevated, as did sCD163 [at week 12, median 1005 (IQR 791, 1577) ng/mL in HIV-positive patients versus 621 (IQR 406, 700) ng/mL in controls; P < 0.0001].

CONCLUSIONS

ART initiation resulted in reductions in levels of CVD-associated biomarkers; however, although they improved, markers of endothelial dysfunction and monocyte activation remained elevated. How these persistent abnormalities affect CVD risk in HIV infection remains to be determined.

Platelet Activation in Human Immunodeficiency Virus Type-1 Patients Is Not Altered with Cocaine Abuse

Recent work has indicated that platelets, which are anucleate blood cells, significantly contribute to inflammatory disorders. Importantly, platelets also likely contribute to various inflammatory secondary disorders that are increasingly associated with Human Immunodeficiency Virus Type-1 (HIV) infection including neurological impairments and cardiovascular complications. Indeed, HIV infection is often associated with increased levels of platelet activators. Additionally, cocaine, a drug commonly abused by HIV-infected individuals, leads to increased platelet activation in humans. Considering that orchestrated signaling mechanisms are essential for platelet activation, and that nuclear factor-kappa B (NF-κB) inhibitors can alter platelet function, the role of NF-κB signaling in platelet activation during HIV infection warrants further investigation. Here we tested the hypothesis that inhibitory kappa B kinase complex (IKK) activation would be central for platelet activation induced by HIV and cocaine. Whole blood from HIV-positive and HIV-negative individuals, with or without cocaine abuse was used to assess platelet activation via flow cytometry whereas IKK activation was analyzed by performing immunoblotting and in vitro kinase assays. We demonstrate that increased platelet activation in HIV patients, as measured by CD62P expression, is not altered with reported cocaine use. Furthermore, cocaine and HIV do not activate platelets in whole blood when treated ex vivo. Finally, HIV-induced platelet activation does not involve the NF-κB signaling intermediate, IKKβ. Platelet activation in HIV patients is not altered with cocaine abuse. These results support the notion that non-IKK targeting approaches will be better suited for the treatment of HIV-associated inflammatory disorders.

Initial Presentation of HIV Infection With Two Successive Acute Arterial Thromboses: A Case Report

Introduction:

One of the complications of HIV infection is greater risk of thromboembolic events. A variety of mechanisms has been found to be responsible for prothrombotic tendency in patients with HIV infection.

Case Presentation:

A 27-year-old heterosexual smoker man was referred to our center due to a sudden-onset severe left lower extremity pain and claudication since three days prior to admission. In physical examination, end extremity coldness and discoloration as well as left lower extremity pulselessness were found. Color-Doppler sonography revealed a large thrombus in the left common iliac artery and two thrombi in the distal halves of both anterior and posterior tibialis arteries, so the patient was transferred to the operating room for proximal thrombectomy where the blood flow was reestablished and all pulses were then detectable. Two days later, the patient developed another similar episode from knee down and underwent the second thrombectomy. In evaluation, HIV Ab had positive result by ELISA.

Conclusions:

This case inspires consideration of HIV infection as a leading cause of thromboembolic event in individuals affected by the first episode of unprovoked one in whom diagnosis of HIV infection has not been established yet.

The evaluation of platelet function in HIV infected, asymptomatic treatment-naïve individuals using flow cytometry

INTRODUCTION

Human immunodeficiency virus (HIV) induces inflammation and platelet activation. People living with HIV are at increased risk of thrombotic events. Activated platelets link inflammation with thrombosis. However platelet function in HIV remains unclear. P-selectin (CD62P), a marker of platelet activation, and platelet glycoprotein GPIV (CD36) a marker of platelet aggregation, can be measured using flow cytometry. We raise a hypothesis that HIV alters the signalling pathways involved in normal platelet function. We evaluated platelet function in HIV using a whole blood platelet flow cytometry based assay.

MATERIALS AND METHODS

Fifty-eight antiretroviral therapy naïve HIV infected and 38 HIV negative individuals were recruited in a clinic in Cape Town. Platelet surface CD36 and CD62P were measured using flow cytometry. These were then correlated with CD4 count, viral load and %CD38 on CD8+ T-cells. Platelet function was evaluated using adenosine diphosphate, arachidonic acid and collagen at varying concentrations.

RESULTS

The HIV group showed increased levels of %CD62P (median 5.51[3.03- 10.11] vs. Control group 2.14[0.19 - 3.59], p<0.0001. This correlated with Viral load (r=0.336, P=0.008). The HIV group also showed increased levels of platelet %CD36 21.93[11.03-44.92] vs. Control 16.15[2.24-25.37], p=0.0087) which correlated with viral load (r=0.398, p=0.024). The HIV group showed a hyper response to AA and collagen at various concentrations. Notably, the HIV group only showed a hyper response to ADP at a maximal concentration of 20 μM (median CD62P MFI, 1.91[1.64-4.95] vs. Control 1.75[1.45-2.44] p=0.0279.

CONCLUSION

The measurement of platelet function using flow cytometry is a rapid technique for the evaluation of platelet signalling pathways that may be modified in HIV infected individuals.

Differential adipose tissue gene expression profiles in abacavir treated patients that may contribute to the understanding of cardiovascular risk: a microarray study

OBJECTIVE

To compare changes in gene expression by microarray from subcutaneous adipose tissue from HIV treatment naïve patients treated with efavirenz based regimens containing abacavir (ABC), tenofovir (TDF) or zidovidine (AZT).

DESIGN

Subcutaneous fat biopsies were obtained before, at 6- and 18-24-months after treatment, and from HIV negative controls. Groups were age, ethnicity, weight, biochemical profile, and pre-treatment CD4 count matched. Microarray data was generated using the Agilent Whole Human Genome Microarray. Identification of differentially expressed genes and genomic response pathways was performed using limma and gene set enrichment analysis.

RESULTS

There were significant divergences between ABC and the other two groups 6 months after treatment in genes controlling cell adhesion and environmental information processing, with some convergence at 18-24 months. Compared to controls the ABC group, but not AZT or TDF showed enrichment of genes controlling adherence junction, at 6 months and 18-24 months (adjusted p<0.05) and focal adhesions and tight junction at 6 months (p<0.5). Genes controlling leukocyte transendothelial migration (p<0.05) and ECM-receptor interactions (p = 0.04) were over-expressed in ABC compared to TDF and AZT at 6 months but not at 18-24 months. Enrichment of pathways and individual genes controlling cell adhesion and environmental information processing were specifically dysregulated in the ABC group in comparison with other treatments. There was little difference between AZT and TDF.

CONCLUSION

After initiating treatment, there is divergence in the expression of genes controlling cell adhesion and environmental information processing between ABC and both TDF and AZT in subcutaneous adipose tissue. If similar changes are also taking place in other tissues including the coronary vasculature they may contribute to the increased risk of cardiovascular events reported in patients recently started on abacavir-containing regimens.

Aspirin Use for Primary and Secondary Prevention in Human Immunodeficiency Virus (HIV)-Infected and HIV-Uninfected Patients

Aspirin use is lower among HIV-infected patients compared to HIV-uninfected patients with a pronounced difference among those patients at highest cardiovascular risk. Aspirin use is also lower among HIV-infected patients when used for secondary prevention.

Background

 Human immunodeficiency virus (HIV) infection is associated with increased risk of myocardial infarction (MI). The use of aspirin for primary and secondary MI prevention in HIV infection has not been extensively studied.

Methods

 We performed a cross-sectional study of 4037 patients infected with HIV and 36 338 demographics-matched control patients in the Partners HealthCare System HIV cohort. We developed an algorithm to ascertain rates of nonepisodic acetylsalicylic acid (ASA) use using medication and electronic health record free text data. We assessed rates of ASA use among HIV-infected and HIV-uninfected (negative) patients with and without coronary heart disease (CHD).

Results

 Rates of ASA use were lower among HIV-infected compared with HIV-uninfected patients (12.4% vs 15.3%, P < .001), with a relatively greater difference among patients with ≥2 CHD risk factors (22.1% vs 42.4%, P < .001). This finding was present among men and among patients in the 30–39 and 40–49 age groups. Among patients with prevalent CHD using ASA for secondary prevention, rates of ASA use were also lower among HIV-infected patients compared with HIV-uninfected patients (51.6% vs 65.4%, P < .001).

Conclusions

 Rates of ASA use were lower among HIV-infected patients compared with controls, with a greater relative difference among those with elevated CHD risk and those with known CHD. Further studies are needed to investigate the optimal strategies for ASA use among patients infected with HIV.

Reduced platelet hyperreactivity and platelet-monocyte aggregation in HIV-infected individuals receiving a raltegravir-based regimen

OBJECTIVE

Platelets are key cells in atherosclerosis and acute cardiovascular events. Platelet hyperreactivity and increased platelet-monocyte aggregation (PMA) are found in HIV-infected patients and may contribute to the excess cardiovascular risk. The integrase inhibitor raltegravir (RAL) has been associated with better residual viral suppression and reduction in inflammatory and coagulation biomarkers. The aim of our study was to investigate whether RAL-treated patients have reduced platelet reactivity and PMA.

DESIGN AND METHODS

We performed a cross-sectional study involving 80 virologically suppressed adult HIV1-infected patients on a RAL-based (n = 25), nonnucleoside reverse transcriptase inhibitor (NNRTI)-based (n = 30) or a protease inhibitor based (n = 25) regimen and 30 healthy controls. Platelet reactivity was determined by measuring platelet P-selectin expression and the binding of fibrinogen to platelets to stimulation with two concentrations of ADP. PMA was determined by measuring the expression of the platelet marker CD42b on CD14 positive cells.

RESULTS

HIV-infected individuals had higher platelet reactivity and PMA than controls. RAL-treated individuals showed significantly lower P-selectin expression to stimulation with low (P = 0.026 vs. NNRTI and P = 0.005 vs. protease inhibitor group) and high-dose ADP (P = 0.009 vs. NNRTI and P = 0.003 vs. protease inhibitor group). A similar trend for was found for fibrinogen binding, although only the difference in P-selectin expression between RAL and protease inhibitor treated patients reached statistical significance (P = 0.038). PMA was also lower in the RAL group than in the NNRTI (P = 0.037) and protease inhibitor (P = 0.034) groups.

CONCLUSION

Use of a RAL-based regimen was associated with a reduction in persistent HIV-induced platelet hyperreactivity and PMA compared with NNRTI and protease inhibitor based regimen.

The value of flow cytometry in the measurement of platelet activation and aggregation in human immunodeficiency virus infection

Human immunodeficiency deficiency virus (HIV) infection is associated with chronic inflammation and an increased risk of thrombotic events. Activated platelets (PLTs) play an important role in both thrombosis and inflammation, and HIV has been shown to induce PLT activation by both direct and indirect mechanisms. P-selectin (CD62P) is a well-described marker of PLT activation, and PLT glycoprotein (GP) IV (CD36) has been identified as a marker of PLT aggregation. Data on PLT function in the context of HIV infection remain inconclusive. Laboratory techniques, such as flow cytometry, enable the assessment of PLTs in their physiological state and environment, with minimal artifactual in vitro activation and aggregation. In this study, we describe a novel flow cytometry PLT assay, which enabled the measurement of PLT function in HIV infection. Forty-one antiretroviral-naïve HIV-positive individuals and 41 HIV-negative controls were recruited from a clinic in the Western Cape. Platelet function was evaluated by assessing the response of platelets to adenosine diphosphate (ADP) at two concentrations (0.04 mM, 0.2 mM). The percentage expression and mean fluorescence intensity (MFI) of CD62P and CD36 was used to evaluate platelet function. These were then correlated with platelet (PLT) count; CD4 count; % CD38/8; viral load and D-dimers. The % CD62P levels were higher in HIV-positive patients (HIV % CD62P 11.33[5.96-29.36] vs. control 2.48[1.56-6.04]; p < 0.0001). In addition, the HIV group showed higher CD62P MFI levels (HIV CD62P MFI 3.25 ± 7.23 vs. control 2.35 ± 1.31, p = 0.0292). Baseline levels of %CD36 expression were significantly higher in HIV-positive patients (%CD36 12.41[6.31-21.83] vs. control 6.04[1.34-13.15]; p = 0.0091). However, the baseline CD36MFI showed no significant difference between the two groups (HIV CD36 MFI 3.09 ± 0.64 vs. control 2.44 ± 0.11, p = 0.4591). The HIV group showed higher levels of % CD36 expression post stimulation with 0.04 mM ADP 43.32 ± 27.41 vs. control 27.47 ± 12.95; p < 0.0214) and no significant difference at 0.2 mM ADP (HIV % CD36 39.06 ± 17.91 vs. control 44.61 ± 18.76; p = 0.3277). Furthermore, the HIV group showed a single phase response to ADP as compared to the control group, which showed a normal biphasic response. We concluded that PLT flow cytometry is valuable in the assessment of levels of PLT activation, and further, that the addition of an endogenous agonist, such as ADP, enabled the measurement of PLT function in HIV infection. We were able to show that, although PLTs are significantly activated in HIV compared to uninfected controls, they retain their functional capacity.

Chronic HIV disease and activation of the coagulation system

With current effective antiretroviral treatment, the spectrum of morbidity and mortality during chronic HIV disease has shifted away from AIDS defining clinical events. Persistent abnormalities in coagulation appear to contribute to excess risk for a broad spectrum of non-AIDS defining complications, including, but not limited to, venous and arterial thrombotic disease. Mechanisms specific to HIV disease, antiretroviral therapy, and lifestyle or behavioral factors contribute to a pro-coagulant state, in part, through increased tissue factor activity coupled with a paradoxical decline in the anti-coagulant response. Alterations in coagulation biology in the context of HIV disease appear to be largely a consequence of persistent systemic immune activation, micro- and macro-vascular disease, and, potentially, impaired hepatic synthesis of coagulation factors. The clinical consequences of HIV-related changes in coagulation biology, the degree to which they are unique to HIV disease, and whether they can be mitigated through adjunct treatments, remains a focus of current research.

In vivo platelet activation and platelet hyperreactivity in abacavir-treated HIV-infected patients

Abacavir (ABC) has been associated with ischaemic cardiovascular events in HIV-infected patients, but the pathogenic mechanisms are unknown. Aim of our study was to assess whether ABC induces in vivo platelet activation and ex vivo platelet hyper-reactivity. In a retrospective, case-control study, in vivo platelet activation markers were measured in 69 HIV-infected patients, before starting therapy and after 6-12 months of either ABC (n=35) or tenofovir (TDF) (n=34), and compared with those from 20 untreated HIV-infected patients. A subgroup of patients was restudied after 28-34 months for ex vivo platelet reactivity. In vivo platelet activation markers were assessed by ELISA or flow cytometry, ex vivo platelet reactivity by light transmission aggregometry (LTA) and PFA-100®. Thein vitro effects of the ABC metabolite, carbovir triphosphate, on aggregation and intra-platelet cGMP were also studied. sPLA2, sPsel and sGPV increased significantly 6-12 months after the beginning of ABC, but not of TDF or of no treatment. Ex vivo platelet function studies showed enhanced LTA, shorter PFA-100® C/ADP closure time and enhanced platelet expression of P-sel and CD40L in the ABC group. The intake of ABC blunted the increase of intraplatelet cGMP induced by nitric oxide (NO) and acutely enhanced collagen-induced aggregation. Preincubation of control platelets with carbovir triphosphate in vitro enhanced platelet aggregation and blunted NO-induced cGMP elevation. In conclusion, treatment with ABC enhances in vivo platelet activation and induces platelet hyperreactivity by blunting the inhibitory effects of NO on platelets. These effects may lead to an increase of ischaemic cardiovascular events.

HIV and coronary heart disease: time for a better understanding

Cardiovascular disease, and particularly coronary heart disease, is an emerging area of concern in the HIV population. Since the advent of efficient antiretroviral therapies and the consequent longer patient life span, an increased risk for myocardial infarction has been observed in HIV-infected patients compared with the general population in Western countries. The pathophysiology of this accelerated atherosclerotic process is complex and multifactorial. Traditional cardiovascular risk factors-overrepresented in the HIV population-associated with uncontrolled viral replication and exposure to antiretroviral drugs (per se or through lipid and glucose disturbances) could promote acute ischemic events. Thus, despite successful antiviral therapy, numerous studies suggest a role of chronic inflammation, together with immune activation, that could lead to vascular dysfunction and atherothrombosis. It is time for physicians to prevent coronary heart disease in this high-risk population through the use of tools employed in the general population. Moreover, the lower median age at which acute coronary syndromes occur in HIV-infected patients should shift prevention to include patients <45 years of age. Available cardiovascular risk scores in the general population usually fail to screen young patients at risk for myocardial infarction. Moreover, the novel vascular risk factors identified in HIV-related atherosclerosis, such as chronic inflammation, immune activation, and some antiretroviral agents, are not taken into account in the available risk scores, leading to underestimation of cardiovascular risk in the HIV population. Cardiovascular prevention in HIV-infected patients is a challenge for both cardiologists and physicians involved in HIV care. We require new tools to assess this higher risk and studies to determine whether intensive primary prevention is warranted.

Role of CD61+ cells in thrombocytopenia of dengue patients

Although hematological disorders with salient features of thrombocytopenia have been well documented in dengue patients, the role of CD61-expressing platelets and the megakaryocytic cell lineage in the pathogenesis of dengue virus (DENV) infection remains largely unexplored. A prospective observational study was performed using blood samples and PBMCs from dengue-confirmed patients, as well as from rhesus monkeys (RM) experimentally infected with DENV. Immunohistochemical staining and FACS techniques were applied to evaluate the frequencies of CD61(+) cells that contained DENV antigen. Highly enriched population of CD61(+) cells was also isolated from acute DENV-infected RM and assayed for DENV RNA by quantitative RT-PCR. Results revealed that DENV antigen was found in small vesicles of varying size, and more frequently in anucleated cells associated with platelets in dengue patients. The DENV antigen-containing cells were CD61(+) and appeared to share characteristics of megakaryocytes. Kinetic profiles of CD61(+) cells from DENV-infected RM revealed a transient increase in CD61(+)CD62P(+) cells early after DENV infection. DENV RNA in a highly enriched population of CD61(+) cells from the infected RM was observed during acute stage. Our results indicate that virus containing CD61(+) cells may be directly linked to the platelet dysfunction and low platelet count characteristics of dengue patients.

Recent advances in pharmacovigilance of antiretroviral therapy in HIV-infected and exposed children

PURPOSE OF REVIEW

Antiretroviral therapy (ART) has greatly improved the survival of HIV-infected children. However, ART is associated with immediate and long-term adverse events. Pharmacovigilance systems, although imperfect, have been developed in many high-income countries (HICs), but coverage in low- and middle-income countries (LMICs) is poor and uneven. This review covers the recent advances in the understanding of adverse events following perinatal ART exposure, including surveillance from birth cohorts; we also describe the adverse events of antiretroviral drugs among HIV-infected children, focussing particularly on those relevant to LMICs, where more than 90% of HIV-infected children live.

RECENT FINDINGS

ART is largely safe in both HIV-infected and HIV-exposed uninfected children, in whom no significant increase in birth defects has been noted. Among HIV-infected children, toxicity to some drugs may be less frequent than in adults, possibly related to immature immune systems in younger children. As per WHO guidelines, many countries are moving from stavudine-based to zidovudine-based or abacavir-based fixed-dose combination (with nevirapine/lamivudine) paediatric mini-pills. However, reassuring data are emerging about short-term stavudine use in LMICs, as this remains an important first-line regimen for young children, as well as an alternative to zidovudine for anaemic children. Zidovudine appears to be well tolerated in young children living in nonmalarious areas, and, among African children, concerns about abacavir hypersensitivity have not been substantiated.

SUMMARY

Optimization of first-line ART regimens needs to take account of the toxicities in HIV-infected children, in particular as they will take ART much longer than adults and during the period of growth and development. The benefits of ART in pregnancy are clear, but long-term follow-up of ART-exposed infants in LMICs through integrated surveillance systems would be invaluable.

HIV replication, inflammation, and the effect of starting antiretroviral therapy on plasma asymmetric dimethylarginine, a novel marker of endothelial dysfunction

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.

Inflammation markers after randomization to abacavir/lamivudine or tenofovir/emtricitabine with efavirenz or atazanavir/ritonavir

BACKGROUND

The effect of specific antiretrovirals on inflammation is unclear.

METHODS

A5224s was a substudy of A5202, which randomized HIV-infected treatment-naïve patients to blinded abacavir/lamivudine (ABC/3TC) or tenofovir/emtricitabine (TDF/FTC) with open-label efavirenz (EFV) or atazanavir/ritonavir (ATV/r) in a factorial design. Our analysis compared changes in inflammation markers from baseline to week 24 between ABC/3TC and TDF/FTC. Secondary analyses included changes at week 96 and comparisons of EFV vs. ATV/r.

RESULTS

Analyses included 244 patients (85% male, 48% white non-Hispanic), median age 39 years, HIV-1 RNA 4.6 log10 copies/ml, CD4 240 cells/μl. TNF-α, soluble receptors of TNF-α (sTNFR)-I and II, soluble vascular cellular adhesion molecule (sVCAM)-1 and soluble intercellular adhesion molecule (sICAM)-1 decreased significantly at weeks 24 and 96, without significant differences between components (P ≥ 0.44). At week 24, ABC/3TC had a greater high-sensitivity C-reactive protein (hsCRP) mean fold change than TDF/FTC {1.43 vs. 0.88, estimated mean fold change percentage difference [Δ] 61.5% [95% confidence interval (CI) 13.6%, 129.5%]; P = 0.008}. Similar results were seen at week 96 (P = 0.021). At week 24 (but not 96), EFV had a greater hsCRP mean fold change than ATV/r [1.41 vs. 0.88; Δ = 60.2% (12.6%, 127.7%); P = 0.009]. IL-6 decreased significantly at week 24 with TDF/FTC but not with ABC/3TC (between-components P = 0.019). At week 96, IL-6 decreased significantly in both nucleoside reverse transcriptase inhibitor components (between-components P = 0.11). IL-6 changes were not significantly different between ATV/r and EFV at either time point (P ≥ 0.89).

CONCLUSIONS

Soluble TNF-receptors and adhesion molecules decreased following treatment initiation and did not differ by regimens. Differences were seen on hsCRP and IL-6 changes with ABC/3TC vs. TDF/FTC and on hsCRP with EFV vs. ATV/r.

HIV infection, aging and cardiovascular disease: epidemiology and prevention

In the developed world, HIV infection is now well managed with very effective and less toxic antiretroviral treatment. HIV-positive patients therefore are living longer, but are now faced by challenges associated with aging. Several non-AIDS associated morbidities are increased in this population, including cardiovascular disease (CVD). It is suggested that CVD occurs earlier among HIV-positive patients compared with HIV-negative patients, and at a higher rate. Several factors have been proposed to contribute to this. First, the traditional CVD risk factors are highly prevalent in this population. High rates of smoking, dyslipidaemia and a family history of CVD have been reported. This population is also aging, with estimates of more than 25% of HIV-positive patients in the developed world being over the age of 50. Antiretroviral treatment, both through its effect on lipids and through other, sometimes less well understood, mechanisms, has been linked to increased CVD risk. HIV infection, especially untreated, is a further contributing factor to increased CVD risk in HIV-positive patients. As the HIV-positive population continues to age, the risk of CVD will continue to increase. Guidelines for the management and prevention of CVD risk have been developed, and are largely modelled on those used in the general population. However, the data currently suggest that these interventions, such as the use of lipid-lowering medications and smoking cessation programs, remain quite low. A better understanding the mechanisms of CVD risk in this aging population and further efforts in improving uptake of prevention strategies will remain an important research area.

Increased platelet reactivity in HIV-1-infected patients receiving abacavir-containing antiretroviral therapy

BACKGROUND

Current or recent use of abacavir for treating human immunodeficiency virus type 1 (HIV-1) infection has been associated with increased rates of myocardial infarction (MI). Given the role of platelet aggregation in thrombus formation in MI and the reversible nature of the abacavir association, we hypothesized that patients treated with abacavir would have increased platelet reactivity.

METHODS

In a prospective study in adult HIV-infected patients, we determined associations between antiretrovirals (ARVs), and in particular the nucleoside reverse transcriptase inhibitor abacavir, and platelet reactivity by measuring time-dependent platelet aggregation in response to agonists: adenosine diphosphate (ADP), thrombin receptor-activating peptide (TRAP), collagen, and epinephrine.

RESULTS

Of 120 subjects, 40 were ARV-naive and 80 ARV-treated, 40 of whom were receiving abacavir. No consistent differences in platelet reactivity were observed between the ARV-naive and ARV-treated groups. In contrast, within the ARV-treated group, abacavir-treated subjects had consistently higher percentages of platelet aggregation upon exposure to ADP, collagen, and epinephrine (P = .037, P = .022, and P = .032, respectively) and had platelets that were more sensitive to aggregation upon exposure to TRAP (P = .025).

CONCLUSIONS

The consistent increases in platelet reactivity observed in response to a range of agonists provides a plausible underlying mechanism to explain the reversible increased rates of MI observed in abacavir-treated patients.

Ritonavir inhibits the two main prasugrel bioactivation pathways in vitro: a potential drug-drug interaction in HIV patients

Prasugrel is an antiplatelet prodrug used in patients with acute coronary syndrome. Prasugrel is mainly bioactivated by cytochromes P450 3A4/5 and CYP2B6. HIV patients are at risk of cardiovascular disease, and the protease inhibitor ritonavir is a potent inhibitor of these 2 CYPs. The aim of this in vitro study was to determine the impact of ritonavir in prasugrel metabolism. Human liver microsomes (HLMs) and recombinant microsomes were used to identify the enzymes responsible for the bioactivation of prasugrel. Prasugrel concentrations of 5 to 200 μM were used for Km determination. Inhibition by ritonavir was characterized using HLMs at concentrations of 0.1 to 30 μM. Prasugrel active metabolite determination was performed with a validated liquid chromatography-mass spectrometry method. Using recombinant microsomes, prasugrel biotransformation was mainly performed by CYP2B6, CYP2D6, CYP2C19, CYP3A4, and CYP3A5. With specific inhibitors of CYP3A, CYP2B6, CYP2D6, CYP2C9, and CYP2C19, active metabolite production was decreased by 38% ± 15% with 4-(4-chlorobenzyl)pyridine (CYP2B6 inhibitor) and by 45 ± 16% with ketoconazole (CYP3A inhibitor). The Km value for prasugrel metabolism in HLMs was determined to be 92.5 μM. Ritonavir at 0.1 to 30 μM was shown to be a potent dose-dependent inhibitor of prasugrel. In this in-vitro study, we found a potent inhibition of prasugrel bioactivation by ritonavir compared to the specific inhibitors of CYP3A and CYP2B6 due to the simultaneous inhibition of CYP2B6 and CYP3A by ritonavir. This finding suggests a potential significant drug-drug interaction between these two drugs.

Abacavir use and cardiovascular disease events: a meta-analysis of published and unpublished data

BACKGROUND

The use of abacavir (ABC) has been associated with an increased risk of cardiovascular disease in some cohort studies. However, no excess risk of myocardial infarction (MI) with ABC therapy has been observed in individual randomized clinical trials (RCTs) and in the aggregated clinical trials database maintained by the manufacturer of ABC.

OBJECTIVE

To combine all the evidence from RCTs by means of meta-analysis to estimate the effect of combined antiretroviral therapy (cART) containing ABC on MI and overall major cardiovascular events (CVEs).

METHODS

Primary outcomes included MI, CVE, adverse events requiring discontinuation of treatment, and overall mortality. We used a conventional Mantel-Haenszel method, with risk ratio and 95% confidence intervals (CIs) or, in the presence of heterogeneity, a random-effect model.

RESULTS

Data were from 28 primary RCTs (9233 participants) comparing ABC-containing cART (4376 participants) to other regimens not containing ABC (4857 controls). MI data were available from 18 trials (31 episodes in 7054 patients) and CVE data from 20 trials (79 episodes in 7899 patients). Compared to the controls, ABC use did not increase significantly the occurrence of MI (risk ratio 0.73, 95% CI 0.39-1.35; P = 0.31), CVE (risk ratio 0.95, 95% CI 0.62-1.44; P = 0.80), overall mortality (risk ratio 1.20, 95% CI 0.63-2.27; P = 0.58), and adverse events requiring discontinuation of treatment (risk ratio 0.82, 95% CI 0.67-1.00; P = 0.05).

CONCLUSION

This meta-analysis of RCTs does not support the hypothesis that ABC-containing cART regimens carry a greater risk of MI or major cardiovascular events relative to comparator cART.

Management of dyslipidemia in HIV-infected patients

Antiretroviral therapy has dramatically increased survival for HIV-infected individuals. As this population lives longer, coronary heart disease has become an important comorbid condition. Dyslipidemia in HIV-infected individuals is a complex condition, with multiple contributing factors including the HIV virus itself, individual genetic characteristics and antiretroviral therapy-induced metabolic changes. Effective management of dyslipidemia in this population is essential to reduce cardiovascular risk but presents multiple challenges due to interactions between antiretroviral therapy agents and lipid-lowering medications.