Cutaneous and plasma values of von Willebrand factor in AIDS: a marker of endothelial stimulation?

Von Willebrand Factor Adhesive Activity and ADAMTS13 Protease Activity in HIV-1-Infected Men

Background: Endothelial activation caused by HIV-1 infection leads to release of von Willebrand factor (VWF), which enters the circulation or attaches to vessel walls and self-assembles into strings and fibers, enabling platelet adhesion; this adhesive activity is regulated by the VWF-cleaving protease ADAMTS13. Our objective was to assess VWF adhesive activity and ADAMTS13 protease activity in HIV-1 infection. Methods: We measured levels of VWF antigen, VWF activation factor (a measure of adhesive activity), ADAMTS13 antigen, ADAMTS13 activity, and apolipoprotein A1 (which interferes with VWF self-association) in serum samples from HIV-1-infected men whose infections were acute (n=10), chronic untreated (n=10), or chronic treated (n=10), compared to uninfected controls (n=10). Means across groups were compared using analysis of variance with contrasts, and Pearson correlations were calculated. Results: Plasma viral load was positively correlated with VWF adhesive activity, which was elevated in acute relative to chronic treated HIV-1 infection. ADAMTS13 antigen and activity were both positively correlated with plasma viral load, and ADAMTS13 activity was significantly higher in men with acute HIV infection than in uninfected controls, and in both acute and chronic untreated HIV infection relative to chronic treated infection. Conclusion: These findings suggest that even in the setting of increased ADAMTS13 protease activity, VWF in HIV-1 infection is hyperadhesive, which may favor development of microvascular and arterial thromboses and thereby contribute to increased cardiovascular risk in HIV-1-infected individuals.

Venous Thrombosis Among Patients with AIDS

Thrombosis has been considered an uncommon complication in patients with AIDS. In a 42-month period, 28 adult male homosexuals with AIDS experienced 34 thrombotic events. All but three received HAART regimen, two a successful round of double nucleoside analog therapy, and one patient received no treatment. Median age of group was 38.5 years (range, 24 to 56 years). Median time from HIV infection to thrombosis was 40.5 months (range, 3 to 108 months). No patient had previous thrombosis, family history of thrombosis, or prothrombotic conditions. There were 31 deep vein thromboses, two pulmonary thromboembolisms, and one renal vein thrombosis. Six patients had two thrombotic events. The rate of thrombosis during the 42-month study period was 1.52% (cumulative incidence = 0.30%/year), while the rate of thrombosis in 600 patients before the era of protease inhibitor therapy was 0.33% (cumulative incidence approximately 0.055%/year) (p < 0.001). Due to high incidence of thrombotic recurrences and hemorrhagic complications while using oral anticoagulants, acetylsalicylic acid was initiated; no thrombotic episodes were recorded while using this drug. Protein C and protein S deficiency were found in nine and two patients, respectively. Two patients had lupus anticoagulant and two activated protein C resistance (APCR) without FV Leiden mutation (APCR test was negative after initial screening). Fifteen patients had no thrombophilic abnormalities. These data suggest that protease inhibitors could be a risk factor for venous thrombosis not due to thrombophilic abnormalities but likely related to abnormalities in platelets or endothelium.

Functional Synergy between CD40 Ligand and HIV-1 Tat Contributes to Inflammation: Implications in HIV Type 1 Dementia

HIV type 1 (HIV-1)-associated dementia (HAD) is believed to occur due to aberrant activation of monocyte-derived macrophages and brain-resident microglial cells by viral proteins as well as by the proinflammatory mediators released by infected cells. To investigate the inflammatory aspects of the disease, we examined the levels of soluble CD40L (sCD40L) in paired samples of plasma and cerebrospinal fluid obtained from 25 HIV-infected individuals. A significantly higher level of sCD40L was detected in both cerebrospinal fluid and plasma from HIV-infected patients with cognitive impairment, compared with their nonimpaired counterparts. The contribution of sCD40L to the pathogenesis of HAD was then examined by in vitro experiments. rCD40L synergized with HIV-1 Tat to increase TNF-alpha release from primary human monocytes and microglia, in an NF-kappaB-dependent manner. The mechanistic basis for this synergism was attributed to a Tat-mediated up-regulation of CD40 in monocytes and microglia. Finally, the CD40L-mediated increase in TNF-alpha production by monocytes was shown to be biologically important; immunodepletion experiments revealed that TNF-alpha was essential for the neurotoxic effects of conditioned medium recovered from Tat/CD40L-treated monocytes. Taken together, our results show that CD40 signaling in microglia and monocytes can synergize with the effects of Tat, further amplifying inflammatory processes within the CNS and influencing neuronal survival.

Thrombosis and a hypercoagulable state in HIV-infected patients

Human immunodeficiency virus infection is an illness with protean manifestations including hematological abnormalities. Thromboembolic complications in HIV-infected patients have been described. Recent literature describes an incidence ranging from 0.26% to 7.6%; higher incidence is seen in patients with active opportunistic infections or malignancy, and in patients with the acquired immunodeficiency syndrome. A variety of potential mechanisms have been proposed to account for the observed hypercoagulability in HIV-infected patients. These include the presence of antiphospholipid-anticardiolipin antibodies, decreased activities of natural anticoagulants (especially protein S), and increased platelet activation. Recent epidemiological studies emphasize the increased incidence of thromboembolic events including myocardial infarction in the HIV-infected population after the introduction of highly active antiretroviral therapy. The use of protease inhibitors in particular is implicated. A hypercoagulable state and especially thromboses are emerging as clinical issues in HIV-infected patients. Further studies are in order to more clearly delineate the pathophysiologic mechanism(s) of thromboses in HIV-infected patients.

Sensitivity of the ProC global assay for protein C pathway abnormalities. clinical experience in 899 unselected patients with venous thromboembolism

The ProC Global is a clotting assay designed to globally evaluate the functionality of the protein C (PC) pathway, which is found defective in up to 30% of the Caucasian patients with thrombophilia. It is based on the ability of endogenous activated protein C (APC), generated by activation of PC by a snake venom extract, to prolong an activated partial thromboplastin time (APTT). This retrospective study was carried out to evaluate the ability of this assay to distinguish patients with or without any PC pathway abnormalities in a cohort of 899 unselected patients with a history of thrombosis. The result of the ProC Global assay, expressed in PC activation time-normalized ratio (PCAT-NR), was significantly lower in patients in whom was previously demonstrated an abnormality of the PC pathway compared to those without. The cut-off level of PCAT-NR=0.75 was found to provide the best sensitivity-specificity ratio, since all the patients with the factor V (FV) Leiden mutation (n=71), APC resistance (n=3), PC deficiency (n=22), or combined defects (n=19) had a PCAT-NR below that value. The sensitivity of the ProC Global assay for a low protein S (PS) level (n=56) was only 66%, and was even weaker in the case of hereditary PS deficiency (46.6%, n=15). The assay did not perform well in samples from patients on oral anticoagulant treatment (OAT, n=64) or with liver failure (n=4), as the PCAT-NR was reduced in most cases, even in the absence of any abnormality. These results suggest that the ProC Global assay could be validly used as a first-step screening test for the FV Leiden-related APC resistance and PC deficiency in patients not on OAT. Given the moderate sensitivity of the assay for PS deficiency, this coagulation inhibitor must be determined in every case. However, the overall benefit of such a screening strategy is limited since more than 38% of the 659 patients without abnormality had a decreased PCAT-NR.

The effects of HIV infection on endothelial function

Endothelial dysfunction and/or injury is pivotal to the development of cardiovascular and inflammatory pathology. Endothelial dysfunction and/or injury has been described in Human Immunodeficiency Virus (HIV) infection. Elaboration of circulating markers of endothelial activation, such as soluble adhesion molecules and procoagulant proteins, occurs in HIV infection. Certain endothelial cells, such as those lining liver sinusoids, human umbilical vein endothelial cells, bone marrow stromal endothelial cells or brain microvascular endothelial cells, have been shown to be variably permissive for HIV infection. Entry of virus into endothelial cells may occur via CD4 antigen or galactosyl-ceramide receptors. Other mechanisms of entry including chemokine receptors have been proposed. Nevertheless, endothelial activation may also occur in HIV infection either by cytokines secreted in response to mononuclear or adventitial cell activation by virus or else by the effects of the secreted HIV-associated proteins, gp 120 (envelope glycoprotein) and Tat (transactivator of viral replication) on endothelium. Enhanced adhesiveness of endothelial cells, endothelial cell proliferation and apoptosis as well as activation of cytokine secretion have all been demonstrated. Synergy between select inflammatory cytokines and viral proteins in inducing endothelial injury has been shown. In HIV infection, dysfunctional or injured endothelial cells potentiate tissue injury, inflammation and remodeling, and accelerate the development of cardiovascular disease.

Acquired protein S deficiency in children infected with human immunodeficiency virus

OBJECTIVES

To determine the prevalence of an acquired deficiency of protein S, a coagulation inhibitor, in children infected with the human immunodeficiency virus (HIV) and to identify clinical and laboratory features associated with this coagulation abnormality.

METHODS

A convenience sample of HIV-infected children, ages 2 to 18 years, was evaluated for total, free and functional protein S; total and functional protein C; prothrombin and activated partial thromboplastin times; fibrinogen; antithrombin III activity; dilute Russell viper venom time; IgG anticardiolipin antibodies; von Willebrand factor antigen; C4b-binding protein; CD4+ T lymphocyte counts; HIV p24 antigen concentration; and serum beta 2-microglobulin concentrations.

RESULTS

Thirty-four subjects were evaluated. Twenty-four subjects were infected perinatally and 10 by transfusion. Nine of the subjects were CDC Class N (asymptomatic), 13 were Class A/B (symptomatic without AIDS-defining condition) and 12 were Class C (AIDS). None had previously documented thrombosis, nephrosis or significant hepatic dysfunction. Twenty-six subjects (76.5%) had decreased free protein S, and 19 (55.9%) had functional protein S < 2 SD below the mean of laboratory controls. Decreased functional protein S was seen in 33.3% of Class N, 53.8% of Class A/B and 75.0% of Class C subjects. The prevalence of decreased total and functional protein S was greater in those with absolute CD4+ T lymphocyte counts < 200/mm3 compared to those with CD4+ counts > or = 200/mm3 (75.0% vs. 38.9%; chi square, 4.48, P = 0.034). A trend toward negative correlation was observed between protein S and duration of HIV infection only for Class N subjects. No linear correlation was seen between protein S and CD4+ T lymphocyte counts; and no significant relationships were observed between protein S values and CMV status, HIV p24 antigen, C4b-binding protein, von Willebrand factor antigen, IgG anti-cardiolipin antibodies or serum beta 2-microglobulin values.

CONCLUSIONS

Acquired protein S deficiency is common in HIV-infected children. The high prevalence of this anticoagulant abnormality suggests an increased risk for thrombotic complications in this population.

Cytokines from activated T cells induce normal endothelial cells to acquire the phenotypic and functional features of AIDS-Kaposi's sarcoma spindle cells

Kaposi's sarcoma (KS) is a proliferative disease of vascular origin particularly frequent in HIV-1-infected homosexual men (AIDS-KS) and characterized by proliferating spindle-shaped cells, angiogenesis, and inflammatory cell infiltration. Previous work has suggested that KS spindle cells are of endothelial cell origin and that chronic immune activation via the release of inflammatory cytokines may cooperate with basic fibroblast growth factor (bFGF) and the HIV-1 Tat protein in the induction and progression of AIDS-KS. Here we show that KS spindle cells have features of activated endothelial cells, and that conditioned media from activated T cells, rich in the same inflammatory cytokines increased in HIV-1-infected individuals, induce normal endothelial cells to acquire the phenotypic and functional features of KS cells. These include (a) acquisition of a similar pattern of cell surface antigen expression; (b) similar proliferative response to bFGF; (c) induction of the responsiveness to the mitogenic effect of extracellular HIV-1 Tat protein that is now able to promote the G1-S transition of endothelial cell cycle; and (d) induction in nude mice of vascular lesions closely resembling early KS as well as the lesions induced by inoculation of KS cells. These results suggest that chronic immune activation, via release of inflammatory cytokines, may play a role in the induction of KS.

Hemostatic abnormalities in acute myocardial infarction as detected by specific blood markers

In order to elucidate the mechanism of thrombus formation in acute myocardial infarction (AMI), coagulation and fibrinolytic and inhibitory proteins were systemically examined in 12 patients with AMI and 29 normal subjects. Activities of factor XII, II and V and concentration of high molecular weight kininogen and Factor II were significantly lower in AMI patients than in normal control subjects. Factor XI activity was also increased in AMI patients as compared with normal controls. Von Willebrand Factor and fibrinogen levels were increased in patients with AMI. Plasma D-dimer concentration was also significantly higher in AMI patients than in controls. Activation of the intrinsic pathway, thrombin generation, fibrin formation and fibrin degradation may be present in patients with AMI just after the onset of coronary thrombus formation.

Quantitative and qualitative assessment of plasma von Willebrand factor in classic Kaposi's sarcoma

BACKGROUND

von Willebrand factor (vWF) is synthesized almost exclusively by endothelial cells and is stored there as ultra-high-molecular-weight multimers. The vWF multimers that are detected in the plasma are smaller than those stored within the endothelium. In two previous studies, comprising small series of cases with classic Kaposi's sarcoma (KS), an endothelium-derived tumor, increased levels of plasma von Willebrand factor antigen (VWF:Ag, the antigenic structure) were reported, suggesting that vWF:Ag may be a marker of endothelium proliferation.

OBJECTIVE

Our purpose was to investigate the quantitative as well as qualitative alterations of plasma vWF in a large series of patients with classic KS at various stages of the disease.

METHODS

Levels of plasma vWF:Ag were studied in 38 patients with classic KS confined to the skin at various stages of the disease and compared with a control group. Thirty-three patients had active KS (i.e., with skin lesions) and five were in remission. In five patients with active KS multimeric analysis of plasma vWF was also performed.

RESULTS

The levels of vWF:Ag were significantly higher among KS patients than in the control group (n = 29, p < 0.01). Levels of vWF:Ag were also significantly higher in patients with active disease as compared with those in remission (p < 0.05). No correlation was found between vWF:Ag levels and the extent of KS. Analysis of the multimeric pattern of plasma vWF showed enhanced staining of all bands, particularly the intermediate and high molecular weight forms, which resemble the endothelial forms as opposed to normal circulating vWF multimers.

CONCLUSION

Quantitative as well as qualitative alterations in plasma vWF were found in patients with KS, which may reflect the destruction or activation of endothelial cells within the lesions. vWF:Ag may serve as a marker of disease activity in classic KS; however, it is not a good marker for the extent of the disease.

An immunoradiometric assay for von Willebrand factor antigen to assess angiogenesis

A method of determining the degree of vascularization of tissues would be of great value in dermatological research such as the investigation of neoangiogenesis in wounds and in the study of the vascular abnormality in psoriasis. We describe an adaptation of an immunoradiometric assay (IRMA) for von Willebrand factor antigen for this purpose. The results show that in endothelial cells in culture there was a good relationship between the number of cells and von Willebrand factor antigen measured by the IRMA. The relationships between the numbers of endothelial cells in biopsies of normal and healing wound skin as estimated by the histometric technique and the IRMA are less good (r = 0.45 and 0.32, respectively) but suggest that there is a positive and proportionate variation. There is a much stronger relationship (r = 0.79) between the biochemical and histometric methods in psoriatic skin.

An immunohistological and genotypic study of the plasma cell form of Castleman's disease

The plasma cell variant of Castleman's disease (angiofollicular hyperplasia) is an uncommon and poorly understood lymphoproliferative disorder which may be associated with a wide variety of systemic features. The clinical, pathological, immunophenotypic and genotypic features of a series of five cases are presented. The clinical manifestations were variable but systemic features were present in four cases. Histologically, all five cases were similar. The characteristic follicle-like structures are composed of concentric rings of B-lymphocytes with a mantle zone phenotype, surrounding an inner core of dendritic reticulum cells. The central regions are composed of plump cells that express Factor VIII related antigen, stain with Ulex europaeus I and are associated with laminin immunoreactivity. Many of these cells stain with Ki67 indicating cellular proliferation. Between these 'follicles', plasma cells are present interspersed between high endothelial venules. Using immunohistochemical techniques two cases were polyclonal, whilst in two others unequivocal lambda/IgA restriction was present; in the other case an intermediate picture of lambda/IgA predominance was apparent. Genotypic studies in three cases indicated immunoglobulin gene rearrangements but germ line T-cell receptor genes. The significance of the apparent clonal proliferation of plasma cells is discussed and a unifying model of Castleman's disease is proposed.