Preexposure Prophylaxis Implementation in a Reproductive Health Setting: Perspectives From Planned Parenthood Providers and Leaders

Integrating pregnancy and HIV prevention services would make reproductive health care settings an optimal venue for the promotion and delivery of preexposure prophylaxis (PrEP) to cisgender women. However, these settings have been slow to adopt PrEP. Planned parenthood clinicians and leaders possess critical insight that can help accelerate PrEP implementation in reproductive health care settings and elements of the Consolidated Framework for Implementation Research (i.e., relative priority of the intervention to staff, implementation climate, available resources to implement the intervention, and staff access to knowledge and information about the intervention) can shed light on elements of Planned Parenthood's inner setting that can facilitate PrEP implementation. In this study, individual 60-min interviews were conducted with clinical care team members (n = 10), leadership team members (n = 6), and center managers (n = 2) to explore their perspectives on PrEP implementation and associated training needs. Transcripts were transcribed verbatim and thematically analyzed. Despite having variable PrEP knowledge, participants (100% women, 61% non-Hispanic White) expressed positive attitudes toward implementing PrEP. Barriers and facilitators toward providing PrEP were reported at the structural, provider, and patient levels. Participants desired PrEP training that incorporated culturally competent patient-provider communication. Although participants identified ways that Planned Parenthood uniquely enabled PrEP implementation, barriers must be overcome to optimize promotion and delivery of PrEP to cisgender women.

Short Communication:Outcomes of Dual Versus Triple Antiretroviral Drug Regimens Among Virally Suppressed Adults in the DC Cohort

This study explored virological outcomes of two-drug (2DRs) and three-drug (3DRs) antiretroviral regimens in adults with HIV in the DC Cohort. We analyzed 310 treatment-experienced adults with sustained HIV RNA ≤50 copies/mL at baseline, 53 of whom switched to 2DRs and 257 continued 3DRs. Adults on 2DRs and 3DRs had similar demographics (median age 53.3 years, 76.8% cisgender male, 76.1% Black). Adults on 2DRs had more participants with ≥2 comorbidities (62.3% vs. 42.8%, p = .019), had a longer time since HIV diagnosis (median years 20.4 vs. 13.2, p = .017), and received the regimen of interest for a shorter duration (median years 1.3 vs. 3.3, p < .001) compared with adults on 3DRs. Adults receiving 2DRs had a higher, although nonsignificant, risk for virological failure (two consecutive HIV RNA ≥50 copies/mL) at 24 months follow-up than adults on 3DRs (6.7% vs. 1.7%, respectively; p = .10). Future analysis of the effectiveness of 2DRs is needed.

Barriers and Facilitators to HIV Testing Among Adolescents and Young Adults in Washington, District of Columbia: Formative Research to Inform the Development of an mHealth Intervention

BACKGROUND

Adolescents and young adults (AYA) in the United States, and in Washington, District of Columbia (DC), specifically, are disproportionately affected by HIV. Both the national Ending the HIV Epidemic initiative and DC-specific plans emphasize HIV testing, and innovative strategies to encourage testing among AYA are needed.

OBJECTIVE

The purpose of this study is to identify sexual behaviors, HIV knowledge, HIV perceptions (eg, susceptibility and severity), and perceived barriers and facilitators to HIV testing among AYA at risk for HIV in DC.

METHODS

This study was part of a larger study to determine the acceptability of using a life-and-dating simulation game to increase HIV testing among AYA. Focus groups and surveys stratified by self-reported sexual orientation were conducted among, and administered to, AYA aged 13-24 years in DC. HIV knowledge was explored during focus groups and measured using an adapted version of the Brief HIV Knowledge Questionnaire. Survey data were summarized using descriptive statistics and compared by self-reported sexual orientation. Transcripts were thematically analyzed.

RESULTS

Of the 46 AYA who participated in the focus groups, 30 (65%) identified as heterosexual and 16 (35%) as lesbian, gay, bisexual, transgender, or queer. A higher proportion of lesbian, gay, bisexual, transgender, or queer AYA reported sexual activity (12/16, 75%, vs 18/30, 60%), condomless sex (11/12, 92%, vs 15/18, 83%), and HIV testing (13/16, 81%, vs 17/29, 58%) than heterosexual AYA. HIV prevention ("condoms" and "...PrEP") and transmission ("exchange of fluids") knowledge was high, and most (34/44, 77%) of the AYA perceived HIV testing as beneficial. However, the AYA also demonstrated some misinformation concerning HIV: an average of 67% (31/46; SD 0.474) of the participants believed that an HIV test could deliver accurate results 1 week after a potential exposure and an average of 72% (33/46; SD 0.455) believed that an HIV vaccine exists. The AYA also identified individual ("...people...are scared"), interpersonal ("it's an awkward conversation"), and structural ("...people don't...know where they can go") barriers to testing. Most of the AYA indicated that they were very likely to use the demonstrated game prototype to help with getting tested for HIV (median 3.0, IQR 2.0-3.0, using a scale ranging from 0 to 3, with 3 indicating high likelihood) and strongly agreed that the game was interesting (median 5.0, IQR 5.0-5.0), fun (median 5.0, IQR 4.0-5.0), and easy to learn (median 5.0, IQR 5.0-5.0, using a scale ranging from 1 to 5, with 5 indicating strong agreement).

CONCLUSIONS

These results suggest a need for multilevel HIV testing interventions and informed the development of a mobile health intervention aiming to increase HIV knowledge and risk perception among AYA, while reducing barriers to testing at the individual and structural levels, supporting efforts to end the domestic HIV epidemic.

Characterization of HIV Risk Behaviors and Clusters Using HIV-Transmission Cluster Engine Among a Cohort of Persons Living with HIV in Washington, DC

Molecular epidemiology (ME) is one tool used to end the HIV epidemic in the United States. We combined clinical and behavioral data with HIV sequence data to identify any overlap in clusters generated from different sequence datasets; to characterize HIV transmission clusters; and to identify correlates of clustering among people living with HIV (PLWH) in Washington, District of Columbia (DC). First, Sanger sequences from DC Cohort participants, a longitudinal HIV study, were combined with next-generation sequences (NGS) from participants in a ME substudy to identify clusters. Next, demographic and self-reported behavioral data from ME substudy participants were used to identify risks of secondary transmission. Finally, we combined NGS from ME substudy participants with Sanger sequences in the DC Molecular HIV Surveillance database to identify clusters. Cluster analyses used HIV-Transmission Cluster Engine to identify linked pairs of sequences (defined as distance ≤1.5%). Twenty-eight clusters of ≥3 sequences (size range: 3-12) representing 108 (3%) participants were identified. None of the five largest clusters (size range: 5-12) included newly diagnosed PLWH. Thirty-four percent of ME substudy participants (n = 213) reported condomless sex during their last sexual encounter and 14% reported a Syphilis diagnosis in the past year. Seven transmission clusters (size range: 2-19) were identified in the final analysis, each containing at least one ME substudy participant. Substudy participants in clusters from the third analysis were present in clusters from the first analysis. Combining HIV sequence, clinical and behavioral data provided insights into HIV transmission that may not be identified using traditional epidemiological methods alone. Specifically, the sexual risk behaviors and STI diagnoses reported in the substudy survey may not have been disclosed during Partner Services activities and the survey data complemented clinical data to fully characterize transmission clusters. These findings can be used to enhance local efforts to interrupt transmission and avert new infections.

A Digital Gaming Intervention to Improve HIV Testing for Adolescents and Young Adults: Protocol for Development and a Pilot Randomized Controlled Trial

Background

Two strategies of the US Ending the HIV Epidemic initiative are early diagnosis of infections via widespread testing and prevention of new infections using pre-exposure prophylaxis (PrEP). These strategies are particularly important for adolescents and young adults (AYAs) who are disproportionately affected by HIV, particularly if they identify as Black and/or lesbian, gay, bisexual, transgender, queer or questioning, and others (LGBTQ+). This study will develop and test an interactive life-simulation game in which players can enact real-life behaviors and receive their HIV risk profile to improve HIV testing and PrEP access among AYAs aged 13-24 years in Washington, DC.

Objective

This mixed methods study aims to determine the acceptability of an interactive, enhanced life-simulation game prototype among AYAs, conduct a pilot test of the gaming intervention among a small cohort of AYAs to ensure game usability and acceptability, and evaluate the efficacy of the game in a randomized controlled study with AYAs at risk for HIV in Washington, DC.

Methods

This research protocol will be conducted in 3 phases. A formative phase will involve surveys and focus groups (n=64) with AYAs living in the DC area. These focus groups will allow researchers to understand youth preferences for game enhancement. The second phase will consist of a pilot test (n=10) of the gaming intervention. This pilot test will allow researchers to modify the game based on formative results and test the planned recruitment and data collection strategy with intended end users. The third phase will consist of a randomized controlled study among 300 AYAs to examine the efficacy of the life-simulation game compared with app-based HIV educational materials on HIV and PrEP in changing HIV testing, knowledge, risk behaviors, and PrEP access. Participants will have unlimited access to either the life-simulation game or the educational app for 3 months from the time of enrollment. Study assessments will occur at enrollment and at 1, 3, and 6 months post enrollment via e-surveys. At 6 months, a subset of intervention participants (n=25) will participate in in-depth exit interviews regarding their experience being in the study.

Results

Institutional review board approval was received on February 5, 2020. This project is currently recruiting participants for the formative phase.

Conclusions

This interactive life-simulation intervention aims to increase HIV testing and PrEP access among AYAs in the DC area. In this intervention, players can enact real-life behaviors and receive their HIV risk profile to promote HIV testing and PrEP seeking. Such an intervention has great potential to improve knowledge of HIV and PrEP among AYAs, increase motivation and self-efficacy related to HIV testing and PrEP use, and decrease individual and structural barriers that often preclude engagement in HIV prevention services.

Trial Registration

ClinicalTrials.gov NCT04917575; https://clinicaltrials.gov/ct2/show/NCT04917575

International Registered Report Identifier (IRRID)

PRR1-10.2196/29792

SARS-CoV-2 and HIV: Epidemiology, Treatment, and Lessons Learned from HIV

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of COVID-19, was first detected in China in December 2019 and has rapidly spread throughout the world. Globally, the impact of COVID-19 has been severe with more than half a million deaths over 6 months; in contrast, the HIV pandemic has resulted in over 32 million deaths worldwide over 40 years. This paper reviews the current epidemiology of COVID-19, summarizes its relationship to HIV, identifies synergies in our response, and suggests actions that can be taken to curtail the spread of COVID-19 among persons living with HIV (PLWH). Our understanding of the epidemiology, clinical presentation, prevention, and treatment of COVID-19 has evolved rapidly as they did with HIV. Epidemiologically, there are similarities between the two viruses including asymptomatic spread, disproportionate impact on persons of color, need for rapid diagnostic testing, and lack of a cure or vaccine. PLWH do not appear generally to have an increased incidence of COVID-19 infection or a more severe course of disease. Clinical trials to identify potential treatment and prevention options for COVID-19 have included antiretrovirals used to treat HIV that have not been efficacious. Public health responses overlap between the two pandemics including the need for behavior change and containment strategies such as contact tracing. As the SARS-CoV-2 pandemic evolves, the path forward to controlling, preventing, and treating COVID-19 can be informed by lessons learned from HIV as we seek to control the spread of both viral pandemics.

Racial and ethnic differences in women's HIV risk and attitudes towards pre-exposure prophylaxis (PrEP) in the context of the substance use, violence, and depression syndemic

Women with syndemic conditions, i.e., two or more co-occurring epidemics, are at elevated risk for HIV acquisition and are therefore prime candidates for pre-exposure prophylaxis (PrEP). However, PrEP uptake remains low among women, especially among Black and Hispanic women. This study examined associations of syndemic conditions with PrEP attitudes and HIV risk among women, and the moderating effect of race and ethnicity. In 2017, 271 non-Hispanic Black, non-Hispanic White, and Hispanic, PrEP-eligible women engaged in care at Planned Parenthood in the northeastern region of the U.S. completed an online survey. Participants reported syndemic conditions (i.e., intimate partner violence, depression, substance use), PrEP attitudes (e.g., PrEP interest), HIV sexual risk (e.g., multiple male sexual partners), and sociodemographics. Structural equation modeling was used to examine the effects of syndemic conditions on PrEP attitudes and HIV risk, and the moderating effect of race and ethnicity. Women with more syndemic conditions had a higher odds of reporting multiple male sexual partners. Syndemic conditions were positively associated with PrEP attitudes for Hispanic women than non-Hispanic Black and White women. Women with syndemic conditions, particularly Hispanic women, may be receptive to interventions promoting PrEP.

A cross-sectional study to characterize local HIV-1 dynamics in Washington, DC using next-generation sequencing

Washington, DC continues to experience a generalized HIV-1 epidemic. We characterized the local phylodynamics of HIV-1 in DC using next-generation sequencing (NGS) data. Viral samples from 68 participants from 2016 through 2017 were sequenced and paired with epidemiological data. Phylogenetic and network inferences, drug resistant mutations (DRMs), subtypes and HIV-1 diversity estimations were completed. Haplotypes were reconstructed to infer transmission clusters. Phylodynamic inferences based on the HIV-1 polymerase (pol) and envelope genes (env) were compared. Higher HIV-1 diversity (n.s.) was seen in men who have sex with men, heterosexual, and male participants in DC. 54.0% of the participants contained at least one DRM. The 40-49 year-olds showed the highest prevalence of DRMs (22.9%). Phylogenetic analysis of pol and env sequences grouped 31.9-33.8% of the participants into clusters. HIV-TRACE grouped 2.9-12.8% of participants when using consensus sequences and 9.0-64.2% when using haplotypes. NGS allowed us to characterize the local phylodynamics of HIV-1 in DC more broadly and accurately, given a better representation of its diversity and dynamics. Reconstructed haplotypes provided novel and deeper phylodynamic insights, which led to networks linking a higher number of participants. Our understanding of the HIV-1 epidemic was expanded with the powerful coupling of HIV-1 NGS data with epidemiological data.

Development, Refinement, and Acceptability of Digital Gaming to Improve HIV Testing Among Adolescents and Young Adults at Risk for HIV

Objective: Adolescents and young adults (AYAs) account for >20% of new HIV diagnoses in the United States, yet >50% are unaware of their infection. Digital gaming is widespread among youth and has proven efficacious in other disease areas; thus, we sought to determine whether a life-and-dating simulation game to increase HIV testing would be acceptable among AYAs. Materials and Methods: Focus groups and surveys were administered to health care providers and AYAs in Washington, DC. AYAs were shown a life-and-dating simulation game that incorporated the Centers for Disease Control and Prevention Risk Estimator tool to demonstrate the potential HIV risk of selected behaviors and a zipcode-level HIV testing locator. Thematic analysis was used to identify general gaming themes and game acceptance. Descriptive statistics were used to summarize response frequencies and Likert scales were used to evaluate game acceptability. Results: Providers, some of whom (38%, n = 5/13) had significant experience caring for youth living with or at increased risk for HIV, advised against the game forcing youth to disclose sexual identity or labeling youth "at risk." AYAs (n = 46) found the initial and revised versions of the game to be highly acceptable: youth thought the game was interesting [mean (standard deviation, SD) = 4.8/5 (0.4)]; liked playing games about HIV-related behaviors [mean (SD) = 4.8/5 (0.5)]; and would share the game to help friends get tested for HIV [mean = 4.6/5 (0.8)]. Conclusions: This study suggests that a digital game to improve HIV testing is acceptable among youth. An efficacy trial is planned to determine the impact of the game on improving HIV testing.

Validation of publicly-available software used in analyzing NGS data for HIV-1 drug resistance mutations and transmission networks in a Washington, DC, Cohort

The DC Cohort is an ongoing longitudinal observational study of persons living with HIV. To better understand HIV-1 drug resistance and potential transmission clusters among these participants, we performed targeted, paired-end next-generation sequencing (NGS) of protease, reverse transcriptase and integrase amplicons. We elected to use free, publicly-available software (HyDRA Web, Stanford HIVdb and HIV-TRACE) for data analyses so that laboratory personnel without extensive bioinformatics expertise could use it; making the approach accessible and affordable for labs worldwide. With more laboratories transitioning away from Sanger-based chemistries to NGS platforms, lower frequency drug resistance mutations (DRMs) can be detected, yet their clinical relevance is uncertain. We looked at the impact choice in cutoff percentage had on number of DRMs detected and found an inverse correlation between the two. Longitudinal studies will be needed to determine whether low frequency DRMs are an early indicator of emerging resistance. We successfully validated this pipeline against a commercial pipeline, and another free, publicly-available pipeline. RT DRM results from HyDRA Web were compared to both SmartGene and PASeq Web; using the Mantel test, R2 values were 0.9332 (p<0.0001) and 0.9097 (p<0.0001), respectively. PR and IN DRM results from HyDRA Web were then compared with PASeq Web only; using the Mantel test, R2 values were 0.9993 (p<0.0001) and 0.9765 (p<0.0001), respectively. Drug resistance was highest for the NRTI drug class and lowest for the PI drug class in this cohort. RT DRM interpretation reports from this pipeline were also highly correlative compared to SmartGene pipeline; using the Spearman's Correlation, rs value was 0.97757 (p<0.0001). HIV-TRACE was used to identify potential transmission clusters to better understand potential linkages among an urban cohort of persons living with HIV; more individuals were male, of black race, with an HIV risk factor of either MSM or High-risk Heterosexual. Common DRMs existed among individuals within a cluster. In summary, we validated a comprehensive, easy-to-use and affordable NGS approach for tracking HIV-1 drug resistance and identifying potential transmission clusters within the community.

ICAM-1-coupled cytoskeletal rearrangements and transendothelial lymphocyte migration involve intracellular calcium signaling in brain endothelial cell lines

Endothelium of the cerebral blood vessels, which constitutes the blood-brain barrier, controls adhesion and trafficking of leukocytes into the brain. Investigating signaling pathways triggered by the engagement of adhesion molecules expressed on brain endothelial cells using two rat brain endothelial cell lines (RBE4 and GP8), we report in this paper that ICAM-1 cross-linking induces a sustained tyrosine phosphorylation of the phosphatidylinositol-phospholipase C (PLC)gamma1, with a concomitant increase in both inositol phosphate production and intracellular calcium concentration. Our results suggest that PLC are responsible, via a calcium- and protein kinase C (PKC)-dependent pathway, for p60Src activation and tyrosine phosphorylation of the p60Src substrate, cortactin. PKCs are also required for tyrosine phosphorylation of the cytoskeleton-associated proteins, focal adhesion kinase and paxillin, but not for ICAM-1-coupled p130Cas phosphorylation. PKC's activation is also necessary for stress fiber formation induced by ICAM-1 cross-linking. Finally, cell pretreatment with intracellular calcium chelator or PKC inhibitors significantly diminishes transmonolayer migration of activated T lymphocytes, without affecting their adhesion to brain endothelial cells. In summary, our data demonstrate that ICAM-1 cross-linking induces calcium signaling which, via PKCs, mediates phosphorylation of actin-associated proteins and cytoskeletal rearrangement in brain endothelial cell lines. Our results also indicate that these calcium-mediated intracellular events are essential for lymphocyte migration through the blood-brain barrier.

Proteasome and thiol involvement in quality control of glycosylphosphatidylinositol anchor addition

Improperly processed secretory proteins are degraded by a hydrolytic system that is associated with the endoplasmic reticulum (ER) and appears to involve re-export of lumenal proteins into the cytoplasm for ultimate degradation by the proteasome. The chimaeric protein hGHDAF28, which contains a crippled glycosylphosphatidylinositol (GPI) C-terminal signal peptide, is degraded by a pathway highly similar to that for other ER-retained proteins and is characterized by formation of disulphide-linked aggregates, failure to reach the Golgi complex and intracellular degradation with a half life of approximately 2 h. Here we show that N-acetyl-leucinal-leucinal-norleucinal, MG-132 and lactacystin, all inhibitors of the proteasome, protect hGHDAF28; hGHDAF28 is still proteolytically cleaved in the presence of lactacystin or MG-132, by the removal of approximately 2 kDa, but the truncated fragment is not processed further. We demonstrate that the ubiquitination system accelerates ER-degradation of hGHDAF28, but is not essential to the process. Overall, these findings indicate that GPI quality control is mediated by the cytoplasmic proteasome. We also show that the presence of a cysteine residue in the GPI signal of hGHDAF28 is required for retention and degradation, as mutation of this residue to serine results in secretion of the fusion protein, implicating thiol-mediated retention as a mechanism for quality control of some GPI signals. Removal of the cysteine also prevents inclusion of hGHDAF28 in disulphide-linked aggregates, indicating that aggregate formation is an additional retention mechanism for this class of protein. Therefore our data suggest that an unpaired terminal cysteine is the retention motif of the hGHDAF28 GPI-processing signal and that additional information may be required for efficient engagement of ER quality control systems by the majority of GPI signals which lack cysteine residues.

Alterations in the structure of apolipoprotein B-100 determine the behaviour of LDL towards thromboplastin

Apolipoprotein B-100 acts as an inhibitor of thromboplastin activity independently of the tissue factor pathway inhibitor (TFPI) associated with plasma lipoproteins. Analysis of the primary structure of Apo B-100 showed a higher than expected occurrence of lysine groups in the receptor-binding region. In order to demonstrate the participation of lysine groups of Apo B-100 in the inhibition of thromboplastin, thromboplastin and Apo B-100 were incubated together in the presence of poly-L-lysine, poly-L-arginine, lysine and arginine monomers. The inhibition of thromboplastin by Apo B-100 was completely suppressed in the presence of poly-L-lysine. Poly-L-arginine was found to be less effective and neither lysine or arginine monomers had any significant effect on the inhibitory effect of Apo B-100. Alterations in the structure of Apo B-100 reconstituted in lipid vesicles resembling LDL, brought about by lipid peroxidation and lipid loading were examined by means of Fourier transform infra-red spectroscopy. It was found that, upon oxidation without the addition of cupric ions, the apolipoprotein attains a more exposed conformation with an increase in alpha-helical structure. This increase occurred at the expense of beta-structure. On lipid loading, an increase in beta-structure at the expense of the alpha-helix, was demonstrated. It is therefore proposed that the variable action of LDL towards thromboplastin derives from alterations in the secondary structure of the Apo B-100, particularly the receptor-binding region.

The mechanism of inhibition of factor III (thromboplastin) activity by apolipoprotein B-100. Protein-protein interactions

Factor III (thromboplastin) activity is inhibited by apoB-100, but the mechanism of inhibition is unknown. By examining the effect of purified apoB-100 on factor III activity, we showed that apoB-100 can inhibit factor III via a different mechanism from that caused by the issue-factor pathway-inhibitor, which is mainly carried on the surface of lipoproteins. Although the presence of calcium ions and factors X and VII may enhance the rate of inhibition, they are not a prerequisite for the inhibition of factor III by apoB-100. In addition, by investigating the changes in the UV spectra of apoB-100 on interaction with factor III and factors X and VII and by assigning the shifts in absorption spectra to particular amino acids, we showed that these interactions involve negative and positive residues within these proteins. By following the rates of interactions between apoB-100 and either factors III, X, VII, a two-step mechanism for the inhibition process involving factors X and VII was postulated. In this mechanism, the primary interaction of apoB-100 with factor III is followed by a rate-limiting step that can be accelerated by the presence of either factor X or VII and leads to the inhibition of factor III. Furthermore, a computer-based analysis of the sequences of factor III revealed a possible binding site for apoB-100.

Porcine platelets contain an increased quantity of ultra-high molecular weight von Willebrand factor and numerous alpha-granular tubular structures

Immunoelectronmicroscopy of human platelet alpha-granules reveals that von Willebrand factor (vWf:Ag) colocalizes with a small number of discrete tubular structures which appear identical to those observed within the Weibel-Palade bodies of endothelial cells. Although it is likely that tubules are composed of vWf:Ag as they are absent in severe vWD porcine platelets, their exact structural and functional nature is still unclear. In this study quantitative/qualitative analysis of vWf:Ag was undertaken in a series of platelet preparations obtained from normal pigs, normal humans and various vWD patients. Electron microscopy confirmed that normal pig platelet alpha-granules contain numerous, regularly spaced tubular structures eccentrically located and coincident with immunogold staining of vWf:Ag. In contrast, normal human platelet alpha-granules contain significantly fewer tubules (usually four to six) which are absent or reduced in number within various vWD platelet sections. Furthermore, the pig platelet lysates not only contained a full complement of multimers but also demonstrated significant intense staining of ultra-high MW material, irrespective of the presence or absence of proteolytic inhibitors. This ultra-high MW vWf appears similar to that observed within lysates prepared from endothelial cells and is susceptible to degradation to lower MW multimers. This study suggests that the tubular structures within alpha-granules and Weibel-Palade bodies may be composed of, or structurally related to, the ultra-high MW intracellular form of vWf:Ag.

The influence of therapeutic blocking of Gp IIb/IIIa on platelet alpha-granular fibrinogen

Recent evidence suggests that platelet alpha-granule fibrinogen (fg) is derived from the plasma pool. Since platelets from patients with Type I Glanzmann's thrombasthenia (GT) are deficient in intracellular fibrinogen (fg) it was hypothesized that Gp IIb/IIIa could mediate the uptake of fg. To study the potential role of Gp IIb/IIIa in intracellular fg trafficking, the influence of therapeutic blocking of Gp IIb/IIIa on platelet fg was studied in 12 patients with stable ischaemic heart disease. Patients were either given a single intravenous dose of the monoclonal antibody 7E3 Fab (n = 4) or a combination of bolus and continuous infusion up to 24 (n = 3), 36 (n = 3) or 96 h (n = 2). All patients showed grossly prolonged bleeding times with a significant reduction of ex-vivo ADP induced aggregation. Although, surface Gp IIb/IIIa binding sites were consistently reduced in all patients, there was a variable but delayed decrease in platelet fg relative to vWf:Ag in only six out of the 12 patients studied. The reduction in fg appeared dependent upon both dosage and duration of Gp IIb/IIIa blockade. The study provides further evidence for the novel role of Gp IIb/IIIa in the intracellular trafficking of fg to platelet and megakaryocytic alpha-granules.

Unique expression of von Willebrand factor by type IIA von Willebrand's disease endothelial cells

Endothelial cells (EC) were cultured from the umbilical cord of a male neonate whose mother was previously diagnosed with type IIA von Willebrand's disease (vWd). The diagnosis of type IIA vWd in the proband was confirmed by low ristocetin activity and the absence of the highest molecular weight (MW) forms of von Willebrand factor (vWf) in his platelet poor plasma. The vWf of EC cultured from the neonate's umbilical cord differed from that of control EC and the cell line EA.hy926 in two respects. Firstly, the full range of molecular weight forms was present in the patient EC lysate and, secondly, vWf:Ag expression was approximately seven-fold greater than that of control cells. Platelet lysates prepared from other affected members of the type IIA vWd family in the presence or absence of proteolytic inhibitors demonstrated a near normal vWf multimeric distribution. Resistance of these high MW forms to heat degradation was conferred by the presence of proteolytic inhibitors. Moreover, the full plasma vWf multimeric distribution could not be restored by the inclusion of EDTA. N-ethylmaleimide and leupeptin in the anticoagulant during the rapid preparation of platelet poor plasma. These findings lend support to the heterogeneous nature of type IIA vWd and has possible implications in the understanding of the intracellular processes involved in the biosynthesis and storage of the vWf macromolecular complex as well as the pathogenesis of type IIA vWd.

Endothelium specific Weibel-Palade bodies in a continuous human cell line, EA.hy926

Weibel-Palade bodies are ultrastructurally defined organelles found only in vascular endothelial cells. Because endothelium in corpo is very dispersed, isolation and further characterization of this organelle has been dependent on increasing the number of cells in culture. However, primary isolates of endothelial cells have a limited replication potential and tend to senesce in culture. In this report, EA.hy926, a continuously replicating cell line derived from human endothelium, is shown to contain Weibel-Palade bodies. Electron micrographs demonstrate the ultrastructural characteristics of these tissue-specific organelles and their cytoplasmic distribution in EA.hy926 cells. Von Willebrand factor, which has been shown to exist in Weibel Palade bodies, is demonstrated by immunofluorescence in discrete rod-shaped organelles whose size, shape, and distribution are consistent with that of Weibel-Palade bodies in primary endothelial cell cultures. Rapid release of von Willebrand factor can be induced by calcium ionophore, and large multimeric forms of the protein are found in EA.hy926 cells. These two properties are consistent with the function currently ascribed to Weibel Palade bodies: storage of multimerized von Willebrand factor. Thus ultrastructural, immunologic, and functional data establish the existence of this as yet poorly understood tissue-specific organelle in a continuous, vigorously replicating human cell line.

Uptake of plasma fibrinogen into the alpha granules of human megakaryocytes and platelets

The origin of platelet alpha-granule fibrinogen (Fg), whether from endogeneous synthesis or exogeneous derivation, remains unknown. Although Fg biosynthesis by megakaryocytes (MK) has been suggested, recent studies have demonstrated that certain alpha-granular proteins originate primarily from plasma. To study the origin of alpha-granule Fg, platelet-associated Fg was measured by ELISA and Western blotting, and localized by immunofluorescence and immunoelectron microscopy in a patient with symptomatic congenital afibrinogenemia before and after replacement therapy with cryoprecipitate. alpha-Granule Fg was detected in the majority of platelets as early as 24 h postinfusion, suggesting that direct platelet uptake was occurring. Platelet Fg reached a maximum value of 42.5% of normal values at 3 d postinfusion and was localized in the alpha-granules, while plasma levels followed a typical half-life profile. Significant alpha-granule Fg was still detectable at 13 d postinfusion, with plasma Fg virtually absent. Studies on cultured CFU-MKs from the patient also confirmed that MKs can incorporate exogeneous Fg into alpha-granules. These results indicate that platelet alpha-granule Fg can be derived from the circulating plasma pool and that Fg uptake can occur in both platelets and MKs.

Benoxaprofen inhibits the adhesion of human monocytes to cultured vascular endothelium

Pretreatment of human monocytes with benoxaprofen for at least 2 h produced a dose-dependent abrogation of their adhesion to monolayers of cultured porcine endothelium with 0.05 microgram/ml and 50.0 micrograms/ml of the drug inducing a mean 33% and 83% inhibition of adhesion respectively. When the endothelium was treated with the drug there was no modification of monocyte adhesion. In contrast, pretreatment of endothelium with 5.0 and 50.0 micrograms/ml benoxaprofen for at least 6 h resulted in a mean 35% and 31% inhibition of polymorphonuclear cell (PMN) adhesion in 6/11 experiments. This inhibitory effect was not seen when drug-treated PMNs were added to endothelium. An impairment of monocyte chemotactic migration was only apparent with high concentrations of the drug (50 micrograms/ml). These results suggest that an important anti-inflammatory property of benoxaprofen is the inhibition of monocyte adhesion to vascular endothelium.