Cardiovascular challenges in the era of antiretroviral therapy for AIDS/ HIV: A comprehensive review of research advancements, pathophysiological insights, and future directions

Cardiovascular disease, particularly coronary heart disease, is becoming more common among those living with HIV. Individuals with HIV face an increased susceptibility to myocardial infarction, also known as a heart attack, as compared to the general population in developed countries. This heightened risk can be attributed mainly to the presence of effective antiretroviral drugs and the resulting longer lifespan. Some cardiac issues linked to non-antiretroviral medications, including myocarditis, endocarditis, cardiomyopathy with dilation, pulmonary hypertension, and oedema of the heart, may affect those not undergoing highly active antiretroviral therapy (ART). Impaired immune function and systemic inflammation are significant contributors to this phenomenon after initiating highly aggressive antiretroviral treatment ART. It is becoming more challenging to determine the best course of treatment for HIV-associated cardiomyopathy due to new research suggesting that protease inhibitors might have a negative impact on the development of HF. Currently, the primary focus of research on ART medications is centered on the cardiovascular adverse effects of nucleoside reverse transcriptase inhibitors and protease inhibitors. This review paper thoroughly evaluates the advancements achieved in cardiovascular disease research and explores the potential implications for prospects. Additionally, it considers the field's future prospects while examining how ART might be altered and its clinical applications.

Platelet Dysregulation in the Pathobiology of COVID-19

Coronavirus disease 2019 (COVID-19) encompasses a broad spectrum of clinical manifestations caused by infection with severe acute respiratory syndrome coronavirus 2.Patients with severe disease present with hyperinflammation which can affect multiple organs which often include observations of microvascular and macrovascular thrombi. COVID-19 is increasingly recognized as a thromboinflammatory disease where alterations of both coagulation and platelets are closely linked to mortality and clinical outcomes. Although platelets are most well known as central mediators of hemostasis, they possess chemotactic molecules, cytokines, and adhesion molecules that are now appreciated as playing an important role in the regulation of immune response. This review summarizes the current knowledge of platelet alterations observed in the context of COVID-19 and their impact upon disease pathobiology.

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.

Recent Advances in the Discovery and Function of Antimicrobial Molecules in Platelets

The conventional function described for platelets is maintaining vascular integrity. Nevertheless, increasing evidence reveals that platelets can additionally play a crucial role in responding against microorganisms. Activated platelets release molecules with antimicrobial activity. This ability was first demonstrated in rabbit serum after coagulation and later in rabbit platelets stimulated with thrombin. Currently, multiple discoveries have allowed the identification and characterization of PMPs (platelet microbicidal proteins) and opened the way to identify kinocidins and CHDPs (cationic host defense peptides) in human platelets. These molecules are endowed with microbicidal activity through different mechanisms that broaden the platelet participation in normal and pathologic conditions. Therefore, this review aims to integrate the currently described platelet molecules with antimicrobial properties by summarizing the pathways towards their identification, characterization, and functional evaluation that have promoted new avenues for studying platelets based on kinocidins and CHDPs secretion.

Platelets function as an acute viral reservoir during HIV-1 infection by harboring virus and T-cell complex formation

Platelets were recently found to harbor infectious HIV virions in infected individuals who are on antiretroviral treatment with poor CD4+ T-cell recovery. In this study, we screened platelets from recently infected individuals, before and after antiretroviral therapy, for the presence of virus and examined platelet activation, as well as CD4+ T-cell recovery. This was followed by in vitro studies assessing platelet-CD4+ T-cell complex formation as a contributing factor to viral transmission. HIV+ platelets were detected in 10 of 10 acutely infected individuals with no prior history of antiretroviral therapy. The percentage of HIV+ platelets dropped significantly after 3 months of antiretroviral therapy in all of the study participants. These individuals also demonstrated significant recovery of CD4+ T cells. Interestingly, the percentage of HIV+ platelets correlated positively with viral load but not with CD4+ T-cell count. Furthermore, we found that platelet activation with soluble CD40L or thrombin receptor activator peptide 6 (TRAP6) increased platelet-virus interactions in vitro. TRAP6-mediated interactions were reduced by platelet antagonists, aspirin, and R406. We demonstrated that platelets transmit the virus to CD4+ T cells, and this transinfection was abolished by inhibiting platelet-T-cell complex formation via exposure to an anti-CD62P antibody. Additionally, treatment with TRAP6 significantly increased the transinfection, which was also inhibited by aspirin and R206. These results reveal that platelets have the potential to promote HIV viral spread during the acute stage of infection, by harboring infectious virus transmitting infection to susceptible CD4+ T cells through complex formation.

Platelets in HIV: A Guardian of Host Defence or Transient Reservoir of the Virus?

The immune and inflammatory responses of platelets to human immunodeficiency virus 1 (HIV-1) and its envelope proteins are of great significance to both the treatment of the infection, and to the comorbidities related to systemic inflammation. Platelets can interact with the HIV-1 virus itself, or with viral membrane proteins, or with dysregulated inflammatory molecules in circulation, ensuing from HIV-1 infection. Platelets can facilitate the inhibition of HIV-1 infection via endogenously-produced inhibitors of HIV-1 replication, or the virus can temporarily hide from the immune system inside platelets, whereby platelets act as HIV-1 reservoirs. Platelets are therefore both guardians of the host defence system, and transient reservoirs of the virus. Such reservoirs may be of particular significance during combination antiretroviral therapy (cART) interruption, as it may drive viral persistence, and result in significant implications for treatment. Both HIV-1 envelope proteins and circulating inflammatory molecules can also initiate platelet complex formation with immune cells and erythrocytes. Complex formation cause platelet hypercoagulation and may lead to an increased thrombotic risk. Ultimately, HIV-1 infection can initiate platelet depletion and thrombocytopenia. Because of their relatively short lifespan, platelets are important signalling entities, and could be targeted more directly during HIV-1 infection and cART.

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.

The chemotactic cytokines in the cerebrospinal fluid of patients with neuroborreliosis

BACKGROUND

The outcome of neuroborreliosis (NB) is variable and may partially depend on host-related immune factors. In NB, the cerebrospinal fluid (CSF) contains a large population of T lymphocytes, but the mechanisms and consequences of their recruitment have not been fully elucidated. We have studied expression of T lymphocyte chemoattractant cytokines in association with CSF cytometric parameters and clinical data in NB patients.

METHODS

The blood and CSF of 17 patients with NB and blood of 12 patients with erythema migrans (EM) were obtained before the antibiotic administration, and in fraction of NB patients during and/or after antibiotic treatment. The control samples came from blood donors (blood) and patients in whom neuroinfection was excluded by a lumbar puncture (CSF). Concentrations of IL-16, CXCL9, CXCL10, CXCL11, CCL2 and CCL5 in serum and CSF were measured with commercial ELISA. Data were analyzed with non-parametric tests, p < 0.05 considered significant.

RESULTS

The serum concentrations of IL-16, CXCL9, CXCL10 and CCL5 were increased, higher in NB than in EM. In CSF all the cytokines were upregulated, CXCL10, CXCL9 and IL-16 over ten-fold. The CSF concentration index favored the intrathecal synthesis of all the cytokines except CCL5, for which it could not be reliably estimated. CCL2, CXCL10 and CXCL9 created concentration gradients towards CSF. The intrathecal expression of IL-16, CCL5 and CXCL9 correlated with CSF lymphocyte counts, of IL-16, CXCL9 and CXCL10 - with a blood-brain barrier disruption, and of CXCL9 and CXCL10 with intrathecal specific IgG synthesis. The expression of CCL2, CXCL10 and CXCL11 peaked early after NB onset and decreased naturally afterwards. High initial CSF CXCL9, CXCL10 and CXCL11 levels associated with a persistent CSF pleocytosis and BBB disruption after treatment, but no cytokine was predictive of clinical outcome. In follow up (post-treatment) examinations, CSF CXCL10 and CCL5 associated positively and CCL2 negatively with a protracted lymphocytic pleocytosis.

CONCLUSIONS

Several cytokines chemotactic for T lymphocytes are upregulated intrathecally in NB, with different dynamics and relation to other inflammatory parameters, suggesting their distinct pathogenetic roles. CXCL10 and CXCL9 are vividly upregulated and seem deeply involved in the pathogenesis of the intrathecal inflammation. IL-16 and CCL5 may directly drive T lymphocyte migration from periphery, but their ability to create an adequate chemotactic gradient remains to be confirmed. A delayed normalization of pleocytosis is accompanied by higher intrathecal expression of Th1-related and lower of Th2-related chemokines, in agreement with the protective role of Th1 to Th2 transition in the course of NB.

The lymphocyte populations and their migration into the central nervous system in tick-borne encephalitis

In tick-borne encephalitis (TBE) the cerebrospinal fluid (CSF) cytosis is dominated by T CD3+CD4+ and T CD3+CD8+ lymphocytes, but their pathogenetic roles and mechanisms of migration into central nervous system (CNS) are unclear. Currently, we have studied CSF lymphocyte subsets and chemotactic axes in TBE patients stratified according to the clinical presentation. Blood and CSF were obtained from 51 patients with TBE (presenting as meningitis in 30, meningoencephalitis in 18 and meningoencephalomyelitis in 3), 20 with non-TBE meningitis and 11 healthy controls. We have studied: (1) abundances of the main lymphocyte subsets and (2) CXCR3 and CCR5 expression on CD3+CD4+ and CD3+CD8+ lymphocytes cytometrically with fluorochrome-stained monoclonal antibodies; (3) concentrations of chemotactic cytokines: CCL5 (CCR5 ligand), CXCL10 (CXCR3 ligand), IL-16, CCL2, CCL20 and CXCL5 with ELISA. Cytokine concentrations were additionally studied in 8 pediatric TBE patients. Data were analyzed with non-parametric tests, p < 0.05 considered significant. The higher CSF lymphocyte counts were associated with symptoms of CNS involvement, especially with altered consciousness (B, Th and Tc cells) and focal neurologic deficits (B cells). The minor fraction of double-positive T CD4+CD8+ cells was unique in associating negatively with encephalitis and altered consciousness. CSF CD3+CD4+ and CD3+CD8+ lymphocyte population was enriched in CCR5-positive cells and CCL5 concentration in CSF was increased and associated with a milder presentation. Although CXCL10 was vividly up-regulated intrathecally and correlated with CSF T lymphocyte counts, the CXCR3 expression in CSF T lymphocytes was low. Serum and CSF concentrations of CCL2, CXCL5 and IL-16 were increased in adult TBE patients, CCL2 created a chemotactic gradient towards CSF and both CCL2 and IL-16 concentrations correlated positively with CSF lymphocyte counts. The particular lymphoid cell populations in CSF associate differently with the clinical presentation of TBE, suggesting their distinct roles in pathogenesis. CCR5/CCL5 axis probably contributes to T lymphocyte migration into CNS. CXCL10 mediates the intrathecal immune response, but is probably not directly responsible for T cell migration. Additional chemotactic factors must be involved, probably including CCL2 and IL-16.

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.

Inflammation-Associated Cytokines IGFBP1 and RANTES Impair the Megakaryocytic Potential of HSCs in PT Patients after Allo-HSCT

Prolonged isolated thrombocytopenia (PT) is a severe complication in patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Whether the megakaryoctic potential of hematopoietic stem cells (HSCs) in bone marrow is intact and what factors drive the pathological process of PT remain elusive. A retrospective study in patients (n = 285) receiving HSCT revealed that the occurrence of PT was approximately 8% and the number of platelets and megakaryocytes in PT patients is much lower compared with control subjects. To test whether the deficiency of thrombopoiesis was caused by the activities of HSCs, the megakaryocytic differentiation potential of HSCs before or after transplantation was assessed. Interestingly, a substantial decrease of megakaryocytic differentiation was observed 2 weeks after transplantation of HSCs in all of the allo-HSCT recipients. However, 4 weeks after transplantation, the ability of HSCs to generate CD41⁺CD42b⁺ megakaryocytes in successful platelet engraftment patients recovered to the same level as those of HSCs before implantation. In contrast, HSCs derived from PT patients throughout the postimplantation period exhibited poor survival and failed to differentiate properly. A protein array analysis demonstrated that multiple inflammation-associated cytokines were elevated in allo-HSCT recipients with PT. Among them, insulin-like growth factor-binding protein 1 and regulated on activation, normal T cell expressed and secreted were found to significantly suppress the proliferation and megakaryocytic differentiation of HSCs in vitro. Our results suggested that the occurrence of PT may be attributed, at least partially, to the damage to HSC function caused by inflammation-associated cytokines after HSCT. These findings shed light on the mechanism underlying HSC megakaryocytic differentiation in PT patients and may provide potential new strategies for treating PT patients after HSCT.

Serum levels of inflammatory cytokines in Rift Valley fever patients are indicative of severe disease

BACKGROUND

Rift Valley fever (RVF) is a mosquito-borne viral zoonosis affecting domestic and wild ruminants, camels and humans. Outbreaks of RVF are characterized by a sudden onset of abortions and high mortality amongst domestic ruminants. Humans develop disease ranging from a mild flu-like illness to more severe complications including hemorrhagic syndrome, ocular and neurological lesions and death. During the RVF outbreak in South Africa in 2010/11, a total of 278 human cases were laboratory confirmed, including 25 deaths. The role of the host inflammatory response to RVF pathogenesis is not completely understood.

METHODS

Virus load in serum from human fatal and non-fatal cases was determined by standard tissue culture infective dose 50 (TCID50) titration on Vero cells. Patient serum concentration of chemokines and cytokines involved in inflammatory responses (IL-8, RANTES, CXCL9, MCP-1, IP-10, IL-1β, IL-6, IL-10, TNF and IL-12p70) was determined using cytometric bead assays and flow cytometry.

RESULTS

Fatal cases had a 1-log10 higher TCID50/ml serum concentration of RVF virus (RVFV) than survivors (p < 0.05). There were no significant sequence differences between isolates recovered from fatal and non-fatal cases. Chemokines and pro- and anti-inflammatory cytokines were detected at significantly increased (IL-8, CXCL9, MCP-1, IP-10, IL-10) or decreased (RANTES) levels when comparing fatal cases to infected survivors and uninfected controls, or when comparing combined infected patients to uninfected controls.

CONCLUSIONS

The results suggest that regulation of the host inflammatory responses plays an important role in the outcome of RVFV infection in humans. Dysregulation of the inflammatory response contributes to a fatal outcome. The cytokines and chemokines identified in this study that correlate with fatal outcomes warrant further investigation as markers for disease severity.

Human platelets and their capacity of binding viruses: meaning and challenges?

Blood platelets are first aimed at ensuring primary hemostasis. Beyond this role, they have been acknowledged as having functions in the maintenance of the vascular arborescence and, more recently, as being also innate immune cells, devoted notably to the detection of danger signals, of which infectious ones. Platelets express pathogen recognition receptors that can sense bacterial and viral moieties. Besides, several molecules that bind epithelial or sub-endothelial molecules and, so forth, are involved in hemostasis, happen to be able to ligate viral determinants, making platelets capable of either binding viruses or even to be infected by some of them. Further, as platelets express both Fc-receptors for Ig and complement receptors, they also bind occasionally virus-Ig or virus-Ig-complement immune complexes. Interplays of viruses with platelets are very complex and viral infections often interfere with platelet number and functions. Through a few instances of viral infections, the present review aims at presenting some of the most important interactions from pathophysiological and clinical points of view, which are observed between human viruses and platelets.

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.

Targeting platelet-derived soluble CD40 ligand: a new treatment strategy for HIV-associated neuroinflammation?

Human immunodeficiency virus type 1 (HIV) continues to be one of the most prevalent global health afflictions to date. The advent and introduction of combined antiretroviral therapy (cART) has made a significant impact on the course of infection. However, as patients are living longer, many HIV-associated illnesses are becoming prevalent among the infected population, especially those associated with chronic inflammation. Consistently, HIV-associated neuroinflammation is believed to be a major catalyst in the development of HIV-associated neurocognitive disorders (HAND), which are estimated to persist in approximately 50% of infected individuals regardless of cART. This dramatically underscores the need to develop effective adjunctive therapies capable of controlling this aspect of the disease, which are currently lacking.

We previously demonstrated that the inflammatory mediator soluble CD40 ligand (sCD40L) is elevated in both the plasma and cerebrospinal fluid of cognitively impaired infected individuals compared to their non-impaired infected counterparts. Our group, and others have recently demonstrated that there is an increasing role for this inflammatory mediator in the pathogenesis of HIV-associated neuroinflammation, thereby identifying this molecule as a potential therapeutic target for the management of HAND. Platelets are the major source of circulating sCD40L, and these small cells are increasingly implicated in a multitude of inflammatory disorders, including those common during HIV infection. Thus, antiplatelet therapies that minimize the release of platelet-derived inflammatory mediators such as sCD40L are an innovative, non-traditional approach for the treatment of HIV-associated neuroinflammation, with the potential to benefit other HIV-associated illnesses.

Platelet activation suppresses HIV-1 infection of T cells

Background

Platelets, anucleate cell fragments abundant in human blood, can capture HIV-1 and platelet counts have been associated with viral load and disease progression. However, the impact of platelets on HIV-1 infection of T cells is unclear.

Results

We found that platelets suppress HIV-1 spread in co-cultured T cells in a concentration-dependent manner. Platelets containing granules inhibited HIV-1 spread in T cells more efficiently than degranulated platelets, indicating that the granule content might exert antiviral activity. Indeed, supernatants from activated and thus degranulated platelets suppressed HIV-1 infection. Infection was inhibited at the stage of host cell entry and inhibition was independent of the viral strain or coreceptor tropism. In contrast, blockade of HIV-2 and SIV entry was less efficient. The chemokine CXCL4, a major component of platelet granules, blocked HIV-1 entry and neutralization of CXCL4 in platelet supernatants largely abrogated their anti-HIV-1 activity.

Conclusions

Release of CXCL4 by activated platelets inhibits HIV-1 infection of adjacent T cells at the stage of virus entry. The inhibitory activity of platelet-derived CXCL4 suggests a role of platelets in the defense against infection by HIV-1 and potentially other pathogens.

Platelet-Derived Microparticles and Platelet Function Profile in Children With Congenital Heart Disease

Platelet microparticles (PMPs) and function profile in children with congenital heart disease (CHD) have not been widely explored. We investigated platelet aggregation, flow cytometric platelet surface receptors (P-selectin and glycoprotein (GP) IIb/IIIa) and PMPs in 23 children with cyanotic CHD (CCHD), 30 children with acyanotic CHD (ACHD) and 30 healthy controls correlating these variables to hematological and coagulation parameters including von Willebrand factor antigen (vWF Ag) as a marker of endothelial dysfunction. Hemoglobin, hematocrit (HCT), d-dimer, and vWF Ag were significantly higher in CCHD than ACHD group. Platelet MPs and P-selectin expression were increased in patients than controls, particularly in CCHD and positively correlated to HCT, d-dimer, and vWF Ag while platelet count, aggregation, and GP IIb/IIIa expression were decreased in CCHD compared with ACHD group and negatively correlated to HCT. The overproduction of PMPs and platelet activation with suppressed aggregation may be implicated in the pathogenesis of coagulation/hemostatic abnormalities in children with CCHD.

Identification of the platelet-derived chemokine CXCL4/PF-4 as a broad-spectrum HIV-1 inhibitor

The natural history of HIV-1 infection is highly variable in different individuals, spanning from a rapidly progressive course to a long-term asymptomatic infection. A major determinant of the pace of disease progression is the in vivo level of HIV-1 replication, which is regulated by a complex network of cytokines and chemokines expressed by immune and inflammatory cells. The chemokine system is critically involved in the control of HIV-1 replication by virtue of the role played by specific chemokine receptors, most notably CCR5 and CXCR4, as cell-surface coreceptors for HIV-1 entry; hence, the chemokines that naturally bind such coreceptors act as endogenous inhibitors of HIV-1. Here, we show that the CXC chemokine CXCL4 (PF-4), the most abundant protein contained within the α-granules of platelets, is a broad-spectrum inhibitor of HIV-1 infection. Unlike other known HIV-suppressive chemokines, CXCL4 inhibits infection by the majority of primary HIV-1 isolates regardless of their coreceptor-usage phenotype or genetic subtype. Consistent with the lack of viral phenotype specificity, blockade of HIV-1 infection occurs at the level of virus attachment and entry via a unique mechanism that involves direct interaction of CXCL4 with the major viral envelope glycoprotein, gp120. The binding site for CXCL4 was mapped to a region of the gp120 outer domain proximal to the CD4-binding site. The identification of a platelet-derived chemokine as an endogenous antiviral factor may have relevance for the pathogenesis and treatment of HIV-1 infection.

Internalization of IgG-coated targets results in activation and secretion of soluble CD40 ligand and RANTES by human platelets

Platelets are crucial elements for maintenance of hemostasis. Other functions attributable to platelets are now being appreciated, such as their role in inflammatory reactions and host defense. Platelets have been reported to bind immunological stimuli like IgG complexes, and for nearly 50 years it has been speculated that platelets may participate in immunological reactions. Platelets have been reported to bind and internalize various substances, similar to other leukocytes, such as macrophages and dendritic cells. In the present study, we tested the hypothesis that human platelets can bind and internalize IgG-coated particles, similar to leukocytes. To this end, we observed that interaction with IgG-coated beads resulted in platelet activation (as measured by CD62P expression), internalization of targets, and significant soluble CD40 ligand (sCD40L) and RANTES (regulated upon activation, normal T cell expresses and secreted) secretion. Blocking FcγRIIA with monoclonal antibody (MAb) IV.3 or inhibiting actin remodeling with cytochalasin D inhibited platelet activation, internalization, and cytokine production. These data suggest that platelets are capable of mediating internalization of IgG-coated particles, resulting in platelet activation and release of both sCD40L and RANTES.

Activation of platelets by Aspergillus fumigatus and potential role of platelets in the immunopathogenesis of Aspergillosis

Aspergillus fumigatus is the most frequent cause of invasive mold infections worldwide. Platelets contribute to inflammation and promote thrombosis, characteristically seen in aspergillosis, and might be involved both in antifungal defense and in the histopathological process. In the experiments reported here, in vitro activation of platelets by conidia, swollen conidia, and hyphae from A. fumigatus was assessed by flow cytometry and enzyme immunoassays. THP-1 monocytes and human monocytes with and without platelets were cultured with hyphae from A. fumigatus, and the release of interleukin-8 (IL-8) was measured by enzyme immunoassays. A. fumigatus potently induced the expression of CD62-p and CD63 and the release of CD40 ligand, RANTES, and Dickkopf homolog 1 in platelets, with particularly enhancing effects of hyphae compared with conidia. The hypha-mediated activation of platelets further enhanced the release of IL-8 both in THP-1 monocytes and in human adherent monocytes. In conclusion, we have found that A. fumigatus is a potent inducer of platelet-mediated inflammation, potentially promoting protective as well as harmful responses during aspergillosis.

Raised LIGHT levels in pulmonary arterial hypertension: potential role in thrombus formation

RATIONALE

Thrombus formation and inflammation are involved in the pathogenesis of pulmonary arterial hypertension (PAH), and LIGHT (Lymphotoxin-like Inducible protein that competes with Glycoprotein D for Herpesvirus entry mediator on T lymphocytes) has been shown to promote vascular inflammation.

OBJECTIVES

We sought to investigate the role of the tumor necrosis factor superfamily ligand LIGHT in the pathogenesis of PAH.

METHODS

We studied 73 patients with severe PAH and 10 control subjects. LIGHT and pro- and antithrombotic markers were assessed by enzyme immunoassays.

MEASUREMENTS AND MAIN RESULTS

(1) Patients with idiopathic PAH (n = 21), patients with PAH related to risk factors or associated conditions (n = 31), and those with chronic thromboembolic PAH (n = 21) all had raised serum levels of LIGHT compared with control subjects (n = 10). (2) LIGHT levels in femoral artery were significantly related to mortality in the patients with PAH. (3) Immunostaining of LIGHT and its receptors was seen in alveolar macrophages, vascular smooth muscle cells, and endothelial cells in lungs from patients with PAH. (4) Thirteen patients received prostacyclin infusion (3 mo), and all showed hemodynamic improvement, accompanied by decreased LIGHT levels. (5) Prostacyclin abolished the release of LIGHT from activated platelets in vitro, suggesting that the decrease in LIGHT during prostacyclin therapy could involve direct effects on platelets. (6) LIGHT increased tissue factor and plasminogen activator inhibitor type 1 and decreased thrombomodulin levels in endothelial cells, inducing a prothrombotic state in these cells.

CONCLUSIONS

Our findings suggest prothrombotic effects of LIGHT in PAH involving endothelium-related mechanisms, potentially contributing to the progression of this disorder.

Increased Levels of Neutrophil-Activating Peptide-2 in Acute Coronary Syndromes

OBJECTIVES

We sought to investigate the role of the CXC chemokine neutrophil-activating peptide-2 (NAP-2) in atherogenesis and plaque destabilization.

BACKGROUND

Chemokines are involved in atherogenesis, but the role of NAP-2 in atherosclerotic disorders is unclear. Based on its potential pro-atherogenic properties, we hypothesized a pathogenic role for NAP-2 in coronary artery disease.

METHODS

We tested this hypothesis by differential experimental approaches including studies in patients with stable (n = 40) and unstable angina (n = 40) and healthy control subjects (n = 20).

RESULTS

The following results were discovered: 1) patients with stable, and particularly those with unstable, angina had markedly raised plasma levels of NAP-2 compared with control subjects, accompanied by increased expression of CXC receptor 2 in monocytes; 2) platelets, but also peripheral blood mononuclear cells (PBMCs), released large amounts of NAP-2 upon stimulation, with a particularly prominent PBMC response in unstable angina; 3) NAP-2 protein was detected in macrophages and smooth muscle cells of atherosclerotic plaques and in monocytes and platelets of coronary thrombi; 4) in vitro, recombinant and platelet-derived NAP-2 increased the expression of adhesion molecules and chemokines in endothelial cells; and 5) whereas aspirin reduced plasma levels of NAP-2, statin therapy increased NAP-2 with stimulating effects both on platelets and leukocytes.

CONCLUSIONS

Our findings suggest that NAP-2 has the potential to induce inflammatory responses within the atherosclerotic plaque. By its ability to promote leukocyte and endothelial cell activation, such a NAP-2-driven inflammation could promote plaque rupture and acute coronary syndromes.

Stimulation of toll-like receptor 2 in mononuclear cells from HIV-infected patients induces chemokine responses: possible pathogenic consequences

Toll-like receptor 2 (TLR2) stimulation in monocytes may contribute to enhanced inflammation and viral replication in HIV infection. In the present study we examined if TLR2 stimulation could modulate chemokine responses in peripheral blood mononuclear cells (PBMC) from HIV-infected patients and healthy controls. Our main findings were, with similar qualitative patterns in both healthy controls and HIV-infected patients: (1) TLR2 stimulation induced up-regulation of several chemokines at the mRNA level as well as increased protein levels of macrophage inflammatory protein (MIP)-1alpha, interleukin (IL)-8 and regulated on activation, normal T cell expressed and secreted (RANTES); (2) TLR2 stimulation induced enhanced protein expression of CCR5 (a receptor for MIP-1alpha and RANTES) on monocytes; (3) In vitro stimulation with RANTES induced release of MIP-1alpha, MCP-1, IL-8 and interferon-gamma from PBMC. While increased levels of beta-chemokines possibly have antiviral effects, TLR2 stimulation may also promote a chemokine-driven inflammatory loop, potentially contributing to the immunopathogenesis of HIV infection.

Interleukin-7-dependent production of RANTES that correlates with human immunodeficiency virus disease progression

There is a relationship between CD4-T-cell number and circulating interleukin 7 (IL-7) levels in human immunodeficiency virus (HIV)-positive individuals. Here, we show that IL-7 induced a dose-dependent production of CCL3 (MIP-1alpha), CCL4 (MIP-1beta), and CCL5 (RANTES) in peripheral blood mononuclear cells (PBMC), ex vivo tonsil lymphoid tissue of HIV(-) individuals, and PBMC from HIV(+) individuals, suggesting that IL-7 may regulate beta-chemokine production in vivo. In a cross-sectional study of HIV(+) individuals (n = 130), a weak but significant correlation between IL-7 and RANTES was noted (r = 0.379; P < 0.001). Remarkably, the correlation between IL-7 and RANTES increased to an r value of 0.798 (P < 0.001) if individuals with low CD4 cell counts (<200 cells/ micro l) were excluded from the analysis. Our results suggest that there is a relationship between IL-7 and the production of RANTES both in vitro and in vivo that is lost in immune-compromised patients (CD4 count of <200 cells/ micro l) but that could be restored by antiretroviral therapy. Unlike the case for IL-7, high levels of RANTES suggest an intermediate stage of HIV disease progression.

Significance of chemokines and activated platelets in patients with diabetes

Levels of platelet-derived microparticles (PMPs), platelet activation markers (P-selectin expressed on, or annexin V binding to, platelets (plt:P-selectin or plt:annexin V, respectively)), chemokines (IL-8, monocyte chemotactic peptide-1 (MCP-1), and regulated on activation normally T-cell expressed and secreted (RANTES)), and soluble P- and E-selectins were compared in peripheral blood from diabetic and control patients in order to develop a better understanding of their potential contribution to diabetic vascular complications. Significant increases were found for PMPs, plt:P-selectin, MCP-1, RANTES and soluble P- and E-selectins in diabetic individuals, whereas IL-8 levels were similar. Furthermore, after ticlopidine treatment, most of these factors receded to baseline levels observed in non-diabetic patients. Our findings indicate that ticlopidine might be able to prevent or reduce vascular complications in diabetic patients.

Spontaneous and antigen-induced production of HIV-inhibitory beta-chemokines are associated with AIDS-free status

The beta-chemokines RANTES, macrophage inflammatory protein (MIP)-1alpha, and MIP-1beta suppress infection by macrophage-tropic strains of HIV and simian immunodeficiency virus (SIV) by binding and down-regulating the viral coreceptor, CCR5. Accordingly, we have examined whether higher levels of CCR5 ligands are associated with a more favorable clinical status in AIDS. A cross-sectional study of 100 subjects enrolled in the Multicenter AIDS Cohort Study at the Baltimore site was conducted to measure chemokine production and lymphocyte proliferation by peripheral blood mononuclear cells (PBMC). Statistical analyses of the data revealed that the production of HIV-suppressive beta-chemokines by HIV antigen-stimulated PBMC was significantly higher in HIV-positive subjects without AIDS compared with subjects with clinical AIDS. Increased chemokine production was also correlated with higher proliferative responses to HIV antigens. Both parameters were significantly lower in the AIDS versus non-AIDS group. Notably, significantly higher levels of MIP-1alpha were also observed with unstimulated PBMC from seronegative subjects at risk for HIV infection released as compared with seropositive and non-Multicenter AIDS Cohort Study seronegative subjects. The association of chemokine production with antigen-induced proliferative responses, more favorable clinical status in HIV infection, as well as with an uninfected status in subjects at risk for infection suggests a positive role for these molecules in controlling the natural course of HIV infection.

Longitudinal analysis of serum chemokine levels in the course of HIV-1 infection

OBJECTIVES

To investigate the correlation between the serum levels of the CC-chemokines RANTES, macrophage inflammatory protein (MIP)-1alpha and MIP-1beta, and the progression of HIV-1 disease.

DESIGN

Retrospective analysis of serial serum samples from HIV-1 seroconverters selected according to clinical outcome.

METHODS

Twenty-one patients, derived from a cohort recruited between 1985 and 1996 for a prospective study of the natural history of HIV infection, were analysed. All patients had at least one HIV-1-seronegative sample within 1 year prior to the first seropositive test and were followed longitudinally throughout the course of HIV-1 infection (mean follow-up, 73.5 months). Nine were rapid progressors (RP; patients who developed AIDS within 60 months of antibody seroconversion), seven were slow progressors (SP; patients who developed AIDS after 60 months), and five were long-term asymptomatic (LTA; patients with circulating CD4+ cells higher than 400 x 10(6)/l, no signs of HIV disease, no antiretroviral therapy for more than 96 months). A total of 339 serum samples was studied (mean, 16.1 per patient). The levels of RANTES, MIP-1alpha and MIP-1beta were measured by enzyme-linked immunosorbent assay and correlated with different immunological and clinical parameters.

RESULTS

Over the entire follow-up period, the geometric mean of serum RANTES was significantly higher in RP [68.6 ng/ml; 95% confidence interval (CI), 56.9-82.7] than in SP (23.7 ng/ml; 95% CI, 20.0-28.2; P < 0.001) and LTA (19.5 ng/ml; 95% CI, 15.5-24.5; P < 0.001). This difference was already significant during the early clinical stages, when patients had peripheral blood CD4+ cell counts still greater than 400 x 10(6)/l (P < 0.001). By contrast, the mean serum levels of MIP-1alpha and MIP-1beta did not differ significantly between the three study groups. Multivariate analysis using the Cox proportional hazard model demonstrated that the mean serum concentration of RANTES before the development of AIDS was independently associated with the time to AIDS (relative risk, 4.5; 95% CI, 1.1-18.2; P = 0.035). In patients with low versus high mean serum RANTES before the fall of CD4+ cells below 400 x 10(6)/l, the median AIDS-free time was 117.5 and 42.7 months, respectively (P = 0.037).

CONCLUSION

These data suggest that an elevation of serum RANTES predicts a rapid progression of the disease since the early stages of HIV-1 infection.

Kinetics of β-Chemokine Levels during Anti-HIV Therapy

Chemokines are pro-inflammatory cytokines that inhibit human immunodeficiency virus type 1 (HIV-1) replication in vitro. We studied the kinetics of the β-chemokines, macrophage inhibitory protein (MIP)-1α, MIP-1β, RANTES, and monocyte chemotactic protein (MCP)-1 in plasma during 12 months of antiretroviral therapy in 26 HIV-1-infected patients and in 11 untreated subjects. Eleven patients with moderate immunodeficiency had HIV-1 RNA levels <50 copies/ml after 1 year, whereas 12 out of 15 patients with severe immunodeficiency had detectable virus. At baseline, MCP-1 levels correlated positively with HIV-1 RNA and DNA levels and inversely with CD4 cell counts. A reverse pattern was seen for the MIP-1β levels. No correlation was seen between MIP-1α or RANTES and any of the parameters. Also, there was a dichotomy between the different β-chemokines in response to therapy. Decreases of MCP-1 and RANTES levels were found, but no durable changes of MIP-1α and MIP-1β. The MCP-1 levels rebounded back to baseline after 1 year in the patients who responded virologically, which could possibly reflect an increased immune activation. The biological consequences of the changes in β-chemokines levels during antiretroviral treatment are still unknown and deserve further studies.