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

Evaluation of the effect of 48 weeks of BIC/F/TAF and DRV/c/F/TAF on platelet function in the context of rapid ART start

INTRODUCTION

The BIC-T&T study aimed to determine the efficacy of bictegravir/emtricitabine/tenofovir alafenamide (BIC/F/TAF) and darunavir/cobicistat/emtricitabine/tenofovir alafenamide (DRV/c/F/TAF) at suppressing viral load in a two-arm, open-label, multi-centre, randomised trial under a UK test-and-treat setting. This sub-study aimed to evaluate potential off-target cardiovascular impact by examining ex vivo platelet function.

METHODS

Platelets were isolated by centrifugation of citrated blood from participants attending Chelsea and Westminster Hospital or St Mary's Hospital at Week 48 following enrolment. Platelet activation was assessed by real-time flow cytometry to examine integrin activation and granule release and platelet aggregation was evaluated by light transmission aggregometry. Statistical significance was determined by 2-way ANOVA with a Šidák's multiple comparisons post-test.

RESULTS

An analysis of 21 participants was performed at Week 48 (96% male and 48% white; mean (range) age was 37 (23-78) years). No difference between arms was observed in ADP-, collagen- or thrombin receptor activator for peptide (TRAP)-6-evoked platelet αIIbβ3 integrin activation, granule release or platelet aggregation in response to any of the agonists tested. Despite differences in the demographics between treatment arms, the presence of an unboosted integrase inhibitor or boosted protease inhibitor in a test-and-treat setting did not impact platelet function.

CONCLUSIONS

Our study provides no evidence of differences in downstream platelet responses between participants taking BIC/F/TAF compared to DRV/c/F/TAF following 48 wk of treatment. Further data are required to explore whether there are biologically significant off-target effects, including effects on platelets and other components of the cardiovascular system between these two test-and-treat regimens.

CLINICAL TRIAL NUMBER

NCT04653194.

In vitro and patient studies with platelets to explore off-target cardiovascular effects of integrase inhibitors

INTRODUCTION

People with HIV currently face a tenfold higher risk of developing cardiovascular disease (CVD) than those without HIV. Studies have shown various off-target effects of antiretroviral treatment (ART) on the cardiovascular system, but little is known about the effects of currently used integrase strand transfer inhibitors (INSTIs) on platelets. Platelet activation is associated with increased CVD, thrombus formation, and release of proinflammatory mediators, so exploring platelet effects from currently prescribed ART may contribute to the understanding of CVD etiopathogenesis in people with HIV.

METHODS

We aimed to identify potential effects of INSTIs on platelet aggregation and activation markers from individuals without HIV after in vitro treatment with clinically relevant drug concentrations. We used bictegravir (BIC) and dolutegravir (DTG) individually or in the therapeutic drug combinations BIC/emtricitabine (FTC)/tenofovir alafenamide fumarate (TAF) or DTG/lamivudine (3TC). Additionally, we conducted a pilot study to compare platelet activity profiles from people with HIV on BIC/FTC/TAF and DTG/3TC.

RESULTS

Changes to in vitro platelet aggregation responses upon exposure to different INSTIs were observed both upon individual drug application and when using therapeutic combinations. However, these effects were not reflected in flow-cytometric evaluation of platelet degranulation. A pilot study in eight people with HIV and eight without HIV revealed no significant effects but established protocols for future patient studies.

CONCLUSION

There is currently no consistent evidence of an effect of INSTIs on platelet activation. Further study is warranted, focusing on models with more pathophysiological relevance, including extensive studies in people with HIV.

Balancing the Interactions: Assessing Antiplatelet and Antiretroviral Therapy Drug-Drug Interactions in People Living With HIV

ABSTRACT

The clinical effect of drug-drug interactions (DDIs) between antiplatelets and antiretroviral therapy (ART) on bleeding, thrombosis, and other major adverse cardiovascular events (MACE) is unknown. The objective of this retrospective study was to assess the incidence of DDI at P2Y12 inhibitor (P2Y12inh) initiation and the effect of DDI on patient outcomes. Adult people living with HIV (PLWH) receiving ART newly initiated on an oral P2Y12inh were included. The primary outcome was the incidence of DDI between ART and P2Y12inh at P2Y12inh initiation. Secondary outcomes included bleeding events, MACE, and switches in P2Y12inh. There were 149 PLWH included, of these, 119 (80%) were initiated on clopidogrel, 23 (15%) on ticagrelor, and 7 (5%) on prasugrel. Ninety-three PLWH (60%) had a DDI at time of P2Y12inh initiation, with highest incidence in the clopidogrel group (n = 84, 71%), followed by ticagrelor (n = 9, 39%) and none with prasugrel. Within 1 year, MACE occurred in 12 PLWH, with DDI present at the time of 4 events. There were 29 bleeding events occurring within 1 year, including 17 events with DDI at time of event. However, 88% of DDI in patients with bleeding events were expected to decrease the efficacy of P2Y12inh. Though we observed high incidence of DDI between P2Y12inh and ART in PLWH, MACE and bleeding events at 1 year did not correlate with DDI. It remains unknown whether DDI presence at P2Y12inh initiation with ART causes clinical outcomes of concern, or whether underlying platelet reactivity in PLWH is associated with these events.

Role of the NO-GC/cGMP signaling pathway in platelet biomechanics

Cyclic guanosine monophosphate (cGMP) is a second messenger produced by the NO-sensitive guanylyl cyclase (NO-GC). The NO-GC/cGMP pathway in platelets has been extensively studied. However, its role in regulating the biomechanical properties of platelets has not yet been addressed and remains unknown. We therefore investigated the stiffness of living platelets after treatment with the NO-GC stimulator riociguat or the NO-GC activator cinaciguat using scanning ion conductance microscopy (SICM). Stimulation of human and murine platelets with cGMP-modulating drugs decreased cellular stiffness and downregulated P-selectin, a marker for platelet activation. We also quantified changes in platelet shape using deep learning-based platelet morphometry, finding that platelets become more circular upon treatment with cGMP-modulating drugs. To test for clinical applicability of NO-GC stimulators in the context of increased thrombogenicity risk, we investigated the effect of riociguat on platelets from human immunodeficiency virus (HIV)-positive patients taking abacavir sulfate (ABC)-containing regimens. Our results corroborate a functional role of the NO-GC/cGMP pathway in platelet biomechanics, indicating that biomechanical properties such as stiffness or shape could be used as novel biomarkers in clinical research.

Heterogeneity of platelets and their responses

There has been increasing recognition of heterogeneity in blood platelets and their responses, particularly in recent years, where next-generation technologies and advanced bioinformatic tools that interrogate "big data" have enabled large-scale studies of RNA and protein expression across a growing list of disease states. However, pioneering platelet biologists and clinicians were already hypothesizing upon and investigating heterogeneity in platelet (and megakaryocyte) activity and platelet metabolism and aggregation over half a century ago. Building on their foundational hypotheses, in particular Professor Marian A. Packham's pioneering work and a State of the Art lecture in her memoriam at the 2023 International Society on Thrombosis and Haemostasis Congress by Anandi Krishnan, this review outlines the key features that contribute to the heterogeneity of platelets between and within individuals. Starting with important epidemiologic factors, we move stepwise through successively smaller scales down to heterogeneity revealed by single-cell technologies in health and disease. We hope that this overview will urge future scientific and clinical studies to recognize and account for heterogeneity of platelets and aim to apply methods that capture that heterogeneity. Finally, we summarize other exciting new data presented on this topic at the 2023 International Society on Thrombosis and Haemostasis Congress.

Clinical features and treatment effect of HIV-associated immune thrombocytopenia-single center Ten-Years data summary

Thrombocytopenia represents one of the most prevalent hematologic complications observed in patients infected with the human immunodeficiency virus (HIV). In this study, we sought to analyze the clinical characteristics and treatment outcomes of patients with coexisting HIV and thrombocytopenia. Specifically, we retrospectively examined the medical records of 45 patients diagnosed with HIV/AIDS and thrombocytopenia at the Yunnan Infectious Diseases Specialist Hospital between January 2010 and December 2020, all of whom received highly active antiretroviral therapy (HAART) with/without glucocorticoids. The median follow-up period was 79 days, ranging between 14 and 368 days, the total platelet count was higher after receiving treatment than before (Z = -5.662, P < .001). Among the cohort, 27 patients (60.0%) responded to treatment, with 12 patients (44.44%) experiencing relapse during the follow-up period. The response rate (80.00%) of newly diagnosed ITP were significantly higher than of persistent ITP (28.57%) and chronic ITP (38.46%) (\x ² = 9.560, P = .008) and the relapse rate of the newly diagnosed ITP (30.00%) was significantly lower than the persistent ITP and chronic ITP (100.00%, 80.00%) (\x² = 6.750, P = .034). Notably, we found that the number of CD4+ T cells, duration of HIV infection, selection of HAART and type of glucocorticoids administered displayed no statistically significant effect on platelet count, treatment response, or relapse rate. However, we observed a significant decrease in platelet count in hepatitis C virus-positive individuals coinfected with HIV compared to those with HIV alone (Z = -2.855, P = .003). Our findings suggest that patients diagnosed with HIV and thrombocytopenia exhibit a low response rate to treatment and have an increased likelihood of relapse.

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.

Two-Drug Regimens for HIV-Current Evidence, Research Gaps and Future Challenges

During the last 30 years, antiretroviral treatment (ART) for human immunodeficiency virus (HIV) infection has been continuously evolving. Since 1996, three-drug regimens (3DR) have been standard-of-care for HIV treatment and are based on a protease inhibitor (PI) or a non-nucleoside reverse transcriptase inhibitor (NNRTI) plus two nucleoside reverse transcriptase inhibitors (NRTIs). The effectiveness of first-generation 3DRs allowed a dramatic increase in the life expectancy of HIV-infected patients, although it was associated with several side effects and ART-related toxicities. The development of novel two-drug regimens (2DRs) started in the mid-2000s in order to minimize side effects, reduce drug-drug interactions and improve treatment compliance. Several clinical trials compared 2DRs and 3DRs in treatment-naïve and treatment-experienced patients and showed the non-inferiority of 2DRs in terms of efficacy, which led to 2DRs being used as first-line treatment in several clinical scenarios, according to HIV clinical guidelines. In this review, we summarize the current evidence, research gaps and future prospects of 2DRs.

Manifestations and Related Risk Factors of Thrombocyte Abnormalities in HIV-Positive Patients Before and After the Initiation of ART

Background

At present, the thrombocyte abnormality is not well described before and after the initiation of antiretroviral therapy (ART). The purpose of this research is to investigate the dynamic changes and related risk factors of thrombocytopenia and thrombocytosis in HIV-infected individuals.

Methods

We performed a real-world observational study among 6637 HIV patients who started ART from January, 2013 to August, 2020 at the Beijing Ditan Hospital. Hazard indicators linked with thrombocytopenia and thrombocytosis were analyzed by logistic/Cox regression.

Results

The prevalence of thrombocytopenia and thrombocytosis was 2.65% and 5.85% among ART-naïve patients, respectively. Correlated risk factors: (thrombocytopenia) older age, coinfection with HBV, leucopenia, anemia, and CD4 count <350 cells/uL; (thrombocytosis) WBC level ≥4.0 x 10⁹/L, anemia, NLR ≥2.0, and CD4 count ≥350 cells/uL. As for the recovery rate, it was 86.6/54.2, 83.4/46.3, 66.0/35.1, and 65.3/ 33.9 per 100 PYFU in thrombocytopenia/thrombocytosis at different treatment period (12m, 24m, 36m, and 48m). While the new-onset incidence of thrombocytopenia/thrombocytosis at different ART period (12m, 24m, 36m, 48m, 60m, 72m, and 84m) was 0.25/7.2, 0.19/6.31, 0.16/4.74, 0.16/4.55, 0.16/4.48, 0.15/4.41, and 0.15/4.39. And the driving forces of thrombocytosis were antiretroviral treatment, female, overweight, and WBC level ≥ 4.0 x 10⁹/L.

Conclusion

In the medical practice, while paying attention to thrombocytopenia, clinicians should be highly vigilant about the thrombocytosis of HIV/AIDS patients, and related treatment strategies need to be further studied.

Plasmatic Coagulation Capacity Correlates With Inflammation and Abacavir Use During Chronic HIV Infection

BACKGROUND

D-dimer concentrations in people living with HIV (PLHIV) on combination antiretroviral therapy (cART) are increased and have been linked to mortality. D-dimer is a biomarker of in vivo coagulation. In contrast to reports on D-dimer, data on coagulation capacity in PLHIV are conflicting. In this study, we assessed the effect of cART and inflammation on coagulation capacity.

SETTING

We explored coagulation capacity using calibrated thrombin generation (TG) and linked this to persistent inflammation and cART in a cross-sectional study including PLHIV with viral suppression and uninfected controls.

METHODS

We used multivariate analyses to identify independent factors influencing in vivo coagulation (D-dimer) and ex vivo coagulation capacity (TG).

RESULTS

Among 208 PLHIV, 94 (45%) were on an abacavir-containing regimen. D-dimer levels (219.1 vs 170.5 ng/mL, P = 0.001) and inflammatory makers (sCD14, sCD163, and high-sensitive C-reactive protein) were increased in PLHIV compared with those in controls (n = 56). PLHIV experienced lower TG (reflected by endogenous thrombin potential [ETP]) when compared with controls, after correction for age, sex, and antiretroviral therapy. Abacavir use was independently associated with increased ETP. Prothrombin concentrations were strongly associated with ETP and lower in PLHIV on a non-abacavir-containing regimen compared with those in controls, suggesting consumption as a possible mechanism for HIV-associated reduction in TG. D-dimer concentrations were associated with inflammation, but not TG.

CONCLUSIONS

Abacavir use was associated with increased TG and could serve as an additional factor in the reported increase in thrombotic events during abacavir use. Increased exposure to triggers that propagate coagulation, such as inflammation, likely underlie increased D-dimer concentrations found in most PLHIV.

Fibrinogen-mimicking, multiarm nanovesicles for human thrombus-specific delivery of tissue plasminogen activator and targeted thrombolytic therapy

Clinical use of tissue plasminogen activator (tPA) in thrombolytic therapy is limited by its short circulation time and hemorrhagic side effects. Inspired by fibrinogen binding to activated platelets, we report a fibrinogen-mimicking, multiarm nanovesicle for thrombus-specific tPA delivery and targeted thrombolysis. This biomimetic system is based on the lipid nanovesicle coated with polyethylene glycol (PEG) terminally conjugated with a cyclic RGD (cRGD) peptide. Our experiments with human blood demonstrated its highly selective binding to activated platelets and efficient tPA release at a thrombus site under both static and physiological flow conditions. Its clot dissolution time in a microfluidic system was comparable to that of free tPA. Furthermore, we report a purpose-built computational model capable of simulating targeted thrombolysis of the tPA-loaded nanovesicle and with a potential in predicting the dynamics of thrombolysis in physiologically realistic scenarios. This combined experimental and computational work presents a promising platform for development of thrombolytic nanomedicines.

Platelet Function in Viral Immunity and SARS-CoV-2 Infection

Platelets, as nonnucleated blood components, are classically recognized for their pivotal role in hemostasis. In recent years, however, accumulating evidence points to a nonhemostatic role for platelets, as active participants in the inflammatory and immune responses to microbial organisms in infectious diseases. This stems from the ability of activated platelets to secrete a plethora of immunomodulatory cytokines and chemokines, as well as directly interplaying with viral receptors. While much attention has been given to the role of the cytokine storm in the severity of the coronavirus disease 2019 (COVID-19), less is known about the contribution of platelets to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Here, we give a brief overview on the platelet contribution to antiviral immunity and response during SARS-CoV-2 infection.

Two drugs regimens for HIV

PURPOSE OF REVIEW

As the evidence for two-drug regimens (2DR) for HIV treatment accumulates and 2DR start to enter consensus guidelines, this review covers the history, rationale and current evidence for 2DR in first-line and switch settings.

RECENT FINDINGS

Until recently, most evidence for 2DR was for boosted protease inhibitor-based therapies but now we have large, randomized trials to support the use of dolutegravir (DTG)-based 2DR, both for initial therapy and suppressed switch, with high efficacy and no emergent resistance at failure.

SUMMARY

2DR will increasingly form part of the choice we are able to offer people with HIV but we must consider some of the limitations to ensure these regimens are used in the most clinically appropriate manner.

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.

Interactions of HIV and Antiretroviral Therapy With Neutrophils and Platelets

Neutrophils are important components of the innate immune system that mediate pathogen defense by multiple processes including phagocytosis, release of proteolytic enzymes, production of reactive oxygen species, and neutrophil extracellular trap formation. Abnormalities of neutrophil count and function have been described in the setting of HIV infection, with the majority of antiretroviral agents (ARVs), excluding zidovudine, having been reported to correct neutropenia. Questions still remain, however, about their impact on neutrophil function, particularly the possibility of persistent neutrophil activation, which could predispose people living with HIV to chronic inflammatory disorders, even in the presence of virally-suppressive treatment. In this context, the effects of protease inhibitors and integrase strand transfer inhibitors, in particular, on neutrophil function remain poorly understood and deserve further study. Besides mediating hemostatic functions, platelets are increasingly recognized as critical role players in the immune response against infection. In the setting of HIV, these cells have been found to harbor the virus, even in the presence of antiretroviral therapy (ART) potentially promoting viral dissemination. While HIV-infected individuals often present with thrombocytopenia, they have also been reported to have increased platelet activation, as measured by an upregulation of expression of CD62P (P-selectin), CD40 ligand, glycoprotein IV, and RANTES. Despite ART-mediated viral suppression, HIV-infected individuals reportedly have sustained platelet activation and dysfunction. This, in turn, contributes to persistent immune activation and an inflammatory vascular environment, seemingly involving neutrophil-platelet-endothelium interactions that increase the risk for development of comorbidities such as cardiovascular disease (CVD) that has become the leading cause of morbidity and mortality in HIV-infected individuals on treatment, clearly underscoring the importance of unraveling the possible etiologic roles of ARVs. In this context, abacavir and ritonavir-boosted lopinavir and darunavir have all been linked to an increased risk of CVD. This narrative review is therefore focused primarily on the role of neutrophils and platelets in HIV transmission and disease, as well as on the effect of HIV and the most common ARVs on the numbers and functions of these cells, including neutrophil-platelet-endothelial interactions.

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.

HIV protease inhibitor ritonavir induces renal fibrosis and dysfunction: role of platelet-derived TGF-β1 and intervention via antioxidant pathways

OBJECTIVE

Chronic kidney disease (CKD) with tubular injury and fibrosis occurs in HIV infection treated with certain protease inhibitor-based antiretroviral therapies. The pathophysiology is unclear.

DESIGN

We hypothesized that fibrosis, mediated by platelet-derived transforming growth factor (TGF)-β1, underlies protease inhibitor-associated CKD. We induced this in mice exposed to the protease inhibitor ritonavir (RTV), and intervened with low-dose inhaled carbon monoxide (CO), activating erythroid 2-related factor (Nrf2)-associated antioxidant pathways.

METHODS

Wild-type C57BL/6 mice and mice deficient in platelet TGF-β1, were given RTV (10 mg/kg) or vehicle daily for 8 weeks. Select groups were exposed to CO (250 ppm) for 4 h after RTV or vehicle injection. Renal disorder, fibrosis, and TGF-β1-based and Nrf2-based signaling were examined by histology, immunofluorescence, and flow cytometry. Renal damage and dysfunction were assessed by KIM-1 and cystatin C ELISAs. Clinical correlations were sought among HIV-infected individuals.

RESULTS

RTV-induced glomerular and tubular injury, elevating urinary KIM-1 (P = 0.004). It enhanced TGF-β1-related signaling, accompanied by kidney fibrosis, macrophage polarization to an inflammatory phenotype, and renal dysfunction with cystatin C elevation (P = 0.008). Mice lacking TGF-β1 in platelets were partially protected from these abnormalities. CO inhibited RTV-induced fibrosis and macrophage polarization in association with upregulation of Nrf2 and heme oxygenase-1 (HO-1). Clinically, HIV infection correlated with elevated cystatin C levels in untreated women (n = 17) vs. age-matched controls (n = 19; P = 0.014). RTV-treated HIV+ women had further increases in cystatin C (n = 20; P = 0.05), with parallel elevation of HO-1.

CONCLUSION

Platelet TGF-β1 contributes to RTV-induced kidney fibrosis and dysfunction, which may be amenable to antioxidant interventions.

Key Principles of Antiretroviral Pharmacology

Antiretroviral therapy has advanced significantly since zidovudine was first approved. Although 31 antiretrovirals have been approved by the FDA, only about half of those are commonly used. Newer, more tolerable agents have made human immunodeficiency virus into a chronic condition, which can be managed with medication. The most common antiretroviral regimens consist of 2 nucleoside reverse transcriptase inhibitors plus a third agent, often an integrase inhibitor because of better tolerability and fewer drug interactions than other regimens. Understanding the dosage forms, adverse effects, and drug interactions of antiretrovirals allow clinicians to choose the most appropriate regimen for their patient. New developments, such as branded generic regimens and long-acting intramuscular injections, may play a larger role in the future.

Platelet function in HIV plus dengue coinfection associates with reduced inflammation and milder dengue illness

HIV-infected subjects under virological control still exhibit a persistent proinflammatory state. Thus, chronic HIV infection changes the host homeostasis towards an adapted immune response that may affect the outcome of coinfections. However, little is known about the impact of HIV infection on inflammatory amplification and clinical presentation in dengue. Platelets have been shown to participate in immune response in dengue and HIV. We hypothesized that altered platelet responses in HIV-infected subjects may contribute to altered inflammatory milieu and disease progression in dengue. We prospectively followed a cohort of 84 DENV-infected patients of whom 29 were coinfected with HIV under virological control. We report that dengue and HIV coinfection progress with reduced inflammation and milder disease progression with lower risk of vascular instability. Even though the degree of thrombocytopenia and platelet activation were similar between dengue-infected and HIV plus dengue-coinfected patients, plasma levels of the platelet-derived chemokines RANTES/CCL5 and PF4/CXCL4 were lower in coinfection. Consistently, platelets from coinfected patients presented defective secretion of the stored-chemokines PF4 and RANTES, but not newly synthesized IL-1β, when cultured ex vivo. These data indicate that platelets from HIV-infected subjects release lower levels of chemokines during dengue illness, which may contribute to milder clinical presentation during coinfection.

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.