The expanded role of the transplant pharmacist: A 10-year follow-up

The role of the transplant pharmacist is recognized by transplant programs, governmental groups, and professional organizations as an essential part of the transplant multidisciplinary team. This role has evolved drastically over the last decade with the advent of major advances in the science of transplantation and the growth of the field, which necessitate expanded pharmacy services to meet the needs of patients. Data now exist within all realms of the phases of care for a transplant recipient regarding the utility and benefit of a solid organ transplant (SOT) pharmacist. Furthermore, governing bodies now have the opportunity to use Board Certification in Solid Organ Transplant Pharmacotherapy as a mechanism to identify and recognize specialty knowledge and expertise within the field of SOT pharmacotherapy. The purpose of this paper is to provide an overarching review of the current and future state of SOT pharmacy while also identifying major changes to the profession, forthcoming challenges, and expected areas of growth.

Overall Infectious Complications Related to Belatacept Conversion in Comparison to Tacrolimus in Kidney Transplant Recipients

Introduction: Belatacept has demonstrated effectiveness for preventing rejection in kidney transplant and has a favorable side effect profile. Studies assessing long-term infectious complications with belatacept compared to tacrolimus are limited. Project Aims: The purpose of this program evaluation was to determine the proportion of patients who developed an infection when converted to belatacept compared to those on tacrolimus. Design: In this retrospective evaluation, kidney transplant recipients receiving belatacept were matched 1:1 to those receiving tacrolimus, based on transplant date, age, induction immunosuppression, and cytomegalovirus risk. Data collection was initiated in tacrolimus patients on the date of belatacept conversion in the belatacept-matched patients. Data were extracted until study conclusion, death, or discontinuation of belatacept. Patients were stratified into 3 groups based on time of conversion posttransplant, which included early, late, and very late conversion. The primary outcome was the proportion of patients with an infection in belatacept compared to tacrolimus. Outcome data were calculated using chi-square, Fisher's exact test, student's t-test or Mann-Whitney U test where appropriate. Results: A total of 328 matched patients were included in the analysis. More patients on belatacept developed an infection compared to tacrolimus (42.7% vs 29.9%, P = 0.02), which was primarily driven by pneumonia (6.1% vs 0.5%; P = 0.01). Higher incidences of infections were identified in those converted within 6 months from transplant. Conclusions: Belatacept was associated with a higher proportion of patients with infections compared to tacrolimus, particularly in those converted within 6 months from time of transplant.

Evaluating Potentially Inappropriate Medications in Older Kidney Transplant Recipients

OBJECTIVES

Beers Criteria and the Screening Tool of Older Persons' Prescriptions (STOPP) Criteria/Screening Tool to Alert to Right Treatment Criteria are used to assess potentially inappropriate prescribing and medications, which could pose a harm to those of older age. The purpose of this study was to assess and compare the use of Beers and STOPP Criteria in older kidney transplant recipients.

METHODS

This was a dual-center, retrospective chart review from May 1, 2014, to March 1, 2018, including kidney transplant recipients 65 years and older. Those who underwent a dual transplant or had incomplete medical records were excluded. Outcomes included number of potentially inappropriate medications (PIMs) comparing Beers and STOPP Criteria on transplant admission, number of PIMs on admission compared with discharge, and readmissions within 3 months related to these medications.

RESULTS

A total of 121 recipients were evaluated. On admission, 60 medications were listed on the STOPP Criteria compared with 106 medications on the Beers Criteria. When comparing PIMs on admission to discharge, there was a 38% decrease in the number of medications on discharge using the STOPP Criteria, whereas there was a 9% increase using the Beers Criteria.

CONCLUSIONS

Older recipients were more likely to be on a medication listed in the Beers Criteria on admission and have a new medication listed in the Beers Criteria upon discharge compared with the STOPP Criteria.

947. Nocardiosis in Renal Transplant Recipients Linked to Decreased Utilization of Trimethoprim/Sulfamethoxazole During COVID-19

Background

The renal transplant population is at increased risk of Nocardiosis due to impaired T-cell mediated immunity with immunosuppression. Pneumocystis jirovecii (PJP) prophylaxis with trimethoprim/sulfamethoxazole (TMP/SMX) provides coverage against Nocardia spp. unlike alternative agents such as atovaquone (ATQ), aerosolized pentamidine (AP), and dapsone. During the COVID-19 pandemic, patients receiving AP were transitioned to ATQ to avoid the use of nebulized medication. This, in turn, led to decreased use of TMP/SMX as patients on oral ATQ were not reassessed for the use of TMP/SMX as would have occurred while on AP. Additionally, an increased incidence of Nocardia infections was observed during this time. The objective of this study was to determine the association between the incidence of Nocardia infections and number of TMP/SMX prophylaxis-days in pre- versus COVID-19 cohorts.

Methods

This was a single center retrospective chart review of all renal transplant recipients between September 2018 – August 2019 (pre-COVID-19 cohort) and April 2020 – March 2021 (COVID-19 cohort). Patients were included if they were at least 18 years of age and a recipient of a cadaveric or living donor kidney transplant. Exclusion criteria included multi-organ transplant, pediatric patients, and repeat transplants. The primary outcome was incidence of Nocardiosis within the first 6 months post-transplant in the pre- and COVID-19 cohorts.

Results

A total of 218 patients were included (Table 1). Induction therapy and initial immunosuppression did not differ significantly between groups, nor did rates of rejection within 180 days of transplant (Table 2). Although the pre-COVID-19 cohort had a higher rate of neutropenia, there was no difference in median absolute lymphocyte count between the two groups. The COVID-19 cohort had a decreased percentage of TMP/SMX prophylaxis-days (59.2% vs. 72.5%, p < 0.0001) and an increased incidence of Nocardia infections in the first 6 months post-transplant (4% vs. 0%, p=0.0292). All 4 cases of Nocardia infections occurred in patients receiving ATQ.

Conclusion

The increased incidence of Nocardiosis was associated with a decreased use of TMP/SMX for PJP prophylaxis which may have been an unintended consequence of increased use of ATQ in lieu of AP during COVID-19.

Disclosures

All Authors: No reported disclosures

Impact of Low-Dose Fluconazole on Tacrolimus Dosing in Renal Transplant

BACKGROUND

The interaction between azole antifungal therapy and immunosuppressant tacrolimus (TAC) is a barrier to use.

OBJECTIVE

This study quantified the drug interaction between low-dose fluconazole (LDF) and TAC to determine the appropriate TAC dose adjustment when used concurrently in renal transplant recipients.

METHODS

We conducted a single-center retrospective chart review of renal transplant patients >18 years who received LDF or nystatin (NYS), and TAC. The primary outcome was the difference in tacrolimus total daily dose (TAC TDD) for LDF versus NYS groups. Secondary outcomes included days with supratherapeutic, therapeutic and subtherapeutic tacrolimus levels, time to therapeutic level, incidence of adverse drug reactions and graft rejection.

RESULTS

We evaluated 94 patients and included 81. Low-dose fluconazole received a greater TAC TDD prior to post-operative day (POD) 10 (10.5 ± 4.7 mg vs. 7.1 ± 4.5 mg, p < 0.001), but a decreased TAC TDD POD 10 - 30 (8.6 ± 2.2 mg vs. 9.8 ± 0.8 mg, p < 0.001) and following LDF discontinuation (6.9 ± 0.1 mg vs. 9.0 ± 0.4 mg, p < 0.001). Low-dose fluconazole had more patient-days with supratherapeutic (17.9 ± 7.0 vs. 13.9 ± 8.5; p = 0.02) but fewer with subtherapeutic (6.7 ± 5.7 vs. 12.9 ± 7.2; p < 0.01) TAC levels. There was no difference in patient-days with therapeutic TAC levels (15.9 ± 5.8 vs. 14.4 ± 6.6, p = 0.28), meanwhile LDF required less patient-days to therapeutic TAC level (7.1 ± 2.7 vs. 11.5 ± 7.7; p < 0.01). There was no difference in adverse drug reactions between groups and no incidence of graft rejection.

CONCLUSION

A 20% reduction in TAC TDD is warranted in renal transplant patients when used concomitantly with LDF to achieve therapeutic levels.

1110. Very Late Onset Infections Amongst Long Term Survivors of Kidney Transplantation

Background

Kidney transplant recipients (KTR) are at increased risk for infections immediately post-transplant due to intense immunosuppression. However, this risk decreases over time as immunosuppression is tapered. The incidence of infection in KTR many years after transplant is not well characterized. The aim of this study was to describe these “very-late onset infections” (VLIs) ≥ 10 years after KT.

Methods

We performed a retrospective chart review of patients age ≥ 18 years who underwent KT between 2003 and 2009 and who survived ≥ 10 years post-KT. VLIs included opportunistic infections (OIs) and non-OIs. Demographics, comorbidities, immunosuppression, and clinical data for VLIs ≥ 10 years from KT were collected. Simple logistic regression was performed to determine characteristics associated with risk for VLIs.

Results

Of 332 KTR that met the inclusion criteria, the majority were male (62.0%), white (59.6%), and the largest proportion was transplanted between the ages of 50-59 (28.3%); 220 (67.9%) were on mycophenolate-based regimens. The mean Charlson Comorbidity Index (CCI) was 4.7 (S.D. 2.0). Of 332, 103 (31.0%) KTR experienced ≥ 1 VLI amounting to 187 episodes. Compared to those without VLI, KTR with VLI were more likely to have diabetes (p=0.005), cardiovascular disease (p=0.004), low ALC (p < 0.001) and require dialysis (p=0.002). Of 103 KTR with VLI, 16 (15.5%) had OIs, while 87 KTR (84.5%) had non-OIs, most commonly urinary tract infection (n=85, 45.5%), pneumonia (n=35, 18.7%) and gastrointestinal infection (n=18, 9.6%). The most commonly isolated pathogens were E. coli (n=30, 16%), K. pneumoniae (n=16, 8.6%), MSSA (n=7, 3.7%), and P. aeruginosa (n=7, 3.7%). Higher CCI, diabetes, dialysis, cerebrovascular, cardiovascular disease and lower ALC were associated with increased risk for VLI (p < 0.05), while living donor KTR was protective (p=0.04). Additionally, every 1 year after transplant was associated with an increased risk of VLI (OR=1.31, p < 0.001).

Table 1: Demographics, comorbidities, immunosuppression, and clinical data for all patients

Conclusion

VLIs were common in long-term survivors of KT and included both conventional and opportunistic pathogens. Every additional year from transplant incurred additional risk for VLI, particularly for those with multiple co-morbidities and lower ALC.

Disclosures

All Authors: No reported disclosures

1099. Opportunistic Infections Among Long Term Survivors of Kidney Transplantation: Defining Risk Factors

Background

Opportunistic infections (OIs) in kidney transplant recipients (KTR) most commonly occur in the early post-transplant period or with increased immunosuppression, largely as a result of impaired T-cell function. Additionally, age confers susceptibility to infection independent of time post-transplant. The combined impact of cumulative immunosuppression and immunosenescence on infection risk of long-term KT survivors has not been well described.

Methods

We performed a retrospective chart review of patients age ≥ 18 years who underwent KT between 2003 to 2009 and who survived ≥ 10 years post-KT, in order to evaluate the risk factors for OIs. Demographics, comorbidities, immunosuppression, and clinical data for OIs occurring ≥ 10 years of KT were collected. AST ID Working Group on Infectious Disease Monitoring definitions for OIs was used. Risk factors for OIs were assessed by simple logistic regression.

Results

Of 332 KTR, 16 (4.8%) had an OI with 18 total episodes. Of 16 KTR, half were white, 10 (62.5%) were male, median age at time of transplant was 43 (range 25-72) and the median post-transplant follow-up was 14.2 years (range 10.3-37.6). The mean Charlson Comorbidity Index (CCI) at diagnosis was 5.6 (S.D. 3.6). Ten patients (62.5%) were on mycophenolate-based regimens. The mean absolute lymphocyte count (ALC) at the time of OI was 0.78 x 10³/µL (S.D. 0.43). Two (12.5%) had acute rejection within 1 year of OI. Of 18 OI episodes, there were 6 PJP, 2 candida esophagitis, 3 CMV (2 viremia, 1 colitis), 2 cryptococcal infections (1 meningitis, 1 myositis/disseminated), 2 adenovirus (pneumonia, colitis), 2 VZV (herpes zoster) and 1 HSV (esophagitis). Two patients had 2 concurrent OIs (1 had PJP and cryptococcus and 1 had HSV and candida esophagitis). Three died within 30-days of OI diagnosis. OI incidence was associated with years from date of transplant [OR 1.3, p=0.002], cerebrovascular disease [OR 4.45, p=0.02], and lower ALC [OR 5.9, p < 0.05]. CCI also trended towards association [OR 1.24, p=0.09].

Table 1: Demographics, comorbidities, immunosuppression, and clinical data for patients with OIs

Table 2: Detailed characteristics of each patient with opportunistic infections

Conclusion

OIs were infrequently observed beyond 10 years of transplant among long-term survivors of KT. However, OI incidence was associated with poor outcome. Low ALC and a higher burden of comorbidities were risk factors for very late occurrence of OIs in this population.

Disclosures

All Authors: No reported disclosures

A Pharmacist-Driven Intervention Designed to Improve Medication Accuracy in the Outpatient Kidney Transplant Setting

Background

Medication errors are one of the leading causes of complications and readmissions in healthcare and stem directly from inadequate medication lists. In transplantation, medication discrepancies can lead to fluctuating levels of immunosuppression, resulting in rejection, infection, or drug toxicity.

Methods

We implemented a pharmacist-driven intervention designed to improve the accuracy of outpatient kidney transplant patients’ medication lists in the electronic medical record (EMR). Baseline medication error rates (Phase 1) were collected, and the intervention was a dedicated pharmacist (Phase 2) who performed medication reconciliation with patients. The primary outcome was the percent of patients with inadequate medication reconciliation determined by any one error in medication reconciliation (Phase 1 vs Phase 2). Secondary outcomes included the number of medication errors, of all medications and high-risk medications, identified per patient sample using statistical process control phase analysis.

Results

Pharmacist-driven medication reconciliation significantly reduced medication list discrepancies from 95% to 28% (P<0.05). There were a total of 398 errors in the control group and 49 errors in the intervention group. In addition, there were 73 high-risk medication discrepancies in the control group and three in the intervention group. The total number of medication errors decreased post-intervention with a marked reduction in the variation of control limits (LCL, UCL: phase 1, −34.3, 113.9; phase 2, −7.1, 15.3) and average number of medication errors per sample (phase 1, 39.8; phase 2, 14.1). For high-risk medications, phase analysis demonstrated a marked reduction in control limit variation between phases (LCL, UCL: phase 1, −10.4, 25.0; phase 2, −0.5, 0.7) and average number of medication errors per sample (phase 1, 7.3; phase 2, 0.1).

Discussion

A dedicated pharmacist improved medication list accuracy over conventional practice that utilizes transplant nurses and physicians. Further studies into the cost-effectiveness of this strategy should further justify this approach.

Identifying a Kidney Transplant Recipient COVID Phenotype to Aid Test Utilization in the Setting of Limited Testing Availability-Does One Exist?

The high morbidity and mortality of COVID-19 in immunocompetent patients raises significant concern for immunosuppressed kidney transplant recipients (KTRs). This level of concern, both on the part of the KTRs and transplant professionals, is heightened by a lack of prior knowledge on how Severe Acute Respiratory Syndrome 2 virus (SARS-CoV-2) may manifest differently in immunosuppressed patients. Characterizing how KTRs may present differently than the general population would allow for more targeted and timely evaluation and treatment of KTRs with COVID-19 infection. METHODS: Without prior knowledge of how this virus would affect our transplant center's delivery of care to KTRs who are SARS-CoV-2 positive or patients under investigation, and in the setting of limited testing availability, we initiated a quality assurance and improvement project (QAPI) to track KTRs followed at our transplant center through the SARS-CoV-2 testing process. RESULTS: Of the 53 symptomatic patients, 20 (38%) tested positive for SARS-CoV-2 either on presentation to the emergency department or referral to a designated outpatient testing center. In addition, 16 (80%) of the 20 patients who tested positive required inpatient treatment. Intriguingly, patients with a history of polyoma BK viremia (BKV) had a higher incidence of testing positive for SARS-CoV-2 compared to patients without a history of BKV (80% and 28%, respectively; P = .002). The Positive Predictive Value and Likelihood ratio was 80% and 6.6 for this association, respectively. Among our KTRs tested, those receiving belatacept had a lower likelihood of testing positive for SARS-CoV-2. This finding approached, but did not achieve, statistical significance (P = .06).

HIV-1 persistence in the central nervous system: viral and host determinants during antiretroviral therapy

Despite remarkable therapeutic advances in the past two decades, the elimination of human immunodeficiency virus type 1 (HIV-1) from latent reservoirs constitutes a major barrier to eradication and preventing neurological disease associated with HIV/AIDS. Invasion of the central nervous system (CNS) by HIV-1 occurs early in infection, leading to viral infection and productive persistence in brain macrophage-like cells (BMCs) including resident microglia and infiltrating macrophages. HIV-1 persistence in the brain and chronic neuroinflammation occur despite effective treatment with antiretroviral therapy (ART). This review examines the evidence from clinical studies, in vivo and in vitro models for HIV-1 CNS persistence, as well as therapeutic considerations in targeting latent CNS reservoirs.

De Novo Belatacept in a Human Immunodeficiency Virus-Positive Kidney Transplant Recipient

Benefits of belatacept-based immunosuppressive regimens in human immunodeficiency virus (HIV)-positive renal transplant recipients include avoidance of drug interactions between calcineurin inhibitors and highly active antiretroviral agents and decreased likelihood or severity of nonimmune toxicities such as new-onset diabetes after transplant, hyperlipidemia and hypertension. We report a successful case of de novo belatacept at >18 mo from transplant in an HIV-positive black man aged 50 years who received his first transplant from a living related kidney donor. To our knowledge, this case is the first reported of belatacept use in an HIV-positive renal transplant recipient.

Listeria monocytogenes bacteremia in a pancreas transplant recipient

We report a case of Listeria monocytogenes bacteremia in a patient 12 years after his pancreas transplant, during which time he received a steroid-free immunosuppressive regimen. To our knowledge, there are no reported cases describing L monocytogenes bacteremia after pancreas transplant. In addition, although typically identified as a complication shortly after transplant or after treatment for organ rejection, this case demonstrates that it is still possible for a patient to develop a L monocytogenes infection far removed from transplant.

Effect of operator and institutional volume on clinical outcomes after percutaneous coronary interventions performed in Canada and the United States: a brief report from the Enhanced Suppression of the Platelet glycoprotein IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) study

BACKGROUND

The Enhanced Suppression of the Platelet glycoprotein IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) trial compared the use of eptifibatide with placebo in 2064 coronary intervention patients. It was previously reported that Canadian patients had reduced rates of 30-day and one-year death, myocardial infarction (MI) or target vessel revascularization (TVR) compared with patients in the United States (US).

OBJECTIVE

To examine whether operator or institutional volume differences explain the regional variation in clinical outcome.

METHODS AND RESULTS

Each site received an operator and institutional volume survey. Fifty-seven sites (62%) returned complete data on 1338 patients. In this smaller cohort, Canadian patients had reduced rates of 30-day and one-year death, MI or TVR compared with US patients (6.3% versus 10.3% and 14.9% versus 20.1%, respectively; P<0.05 for both comparisons). Among 176 physicians with a median of 13 years experience, the median operator volume was 200 cases per year. Operators with fewer than 100 cases per year had higher rates of 30-day death, MI or TVR (13.2% versus 8.7%; P=0.18) and large MI (7.7% versus 3.3%; P=0.06) than those with 100 or more cases per year. The median institutional volume was 1064 cases per year. Canadian and US centres had similar operator and institutional volumes. By multivariate modelling, operator volume was not predictive of adverse clinical events. However, the rates of 30-day and one-year death, MI or TVR fell by 3% for every 100 patients treated by the institution (OR 0.97; P=0.058 and P=0.002, respectively). Enrollment in Canada was associated with improved outcomes at 30 days (OR 0.50; P=0.001) and one year (OR 0.66; P=0.001) despite inclusion of volume variables in the models.

CONCLUSIONS

In the ESPRIT study, institutional volume was associated with a modest reduction in risk of death, MI or TVR over short- and long-term follow-up periods. The Canadian and US investigators and institutions selected in ESPRIT had similar annual procedural volumes. Therefore, volume variables did not explain the differential risk of clinical events observed for patients enrolled in the two countries.

First experience with direct, selective factor Xa inhibition in patients with non-ST-elevation acute coronary syndromes: results of the XaNADU-ACS Trial

BACKGROUND

Unfractionated heparin is widely used in patients with non-ST-elevation acute coronary syndromes but has important limitations. Anticoagulants with predictable kinetics and anticoagulant effects, better efficacy, and greater safety are needed.

OBJECTIVE

To investigate the efficacy and safety of a direct, selective factor Xa inhibitor, DX-9065a (Daiichi Pharmaceuticals LTD, Inc.) compared with heparin, in patients with non-ST-elevation acute coronary syndromes.

PATIENTS AND METHODS

Patients (n = 402) from the USA, Canada, and Japan were randomized to blinded, weight-adjusted heparin, low-dose DX-9065a, or high-dose DX-9065a.

RESULTS

The primary efficacy endpoint of death, myocardial infarction, urgent revascularization, or ischemia on continuous ST-segment monitoring occurred in 33.6%, 34.3%, and 31.3% of patients assigned to heparin, low-dose DX-9065a, and high-dose DX-9065a (P = 0.91 for heparin vs. combined DX-9065a). The composite of death, myocardial infarction, or urgent revascularization occurred in 19.5%, 19.3%, and 11.9% (P = 0.125 for heparin vs. high-dose DX-9065a) of patients; major or minor bleeding occurred in 7.7%, 4.2%, and 7.0% of patients; and major bleeding in 3.3%, 0.8%, and 0.9% of patients. Higher concentrations of DX-9065a were associated with a lower likelihood of ischemic events (P = 0.03) and a non-significant tendency toward a higher likelihood of major bleeding (P = 0.32).

CONCLUSIONS

In this small phase II trial, there was a non-significant tendency toward a reduction in ischemic events and bleeding with DX-9065a compared with heparin in patients with acute coronary syndromes. The absence of an effect on ST-monitor ischemia warrants further investigation. These data provide the rationale for adequately powered studies of DX-9065a in acute coronary syndromes or percutaneous intervention.

Initial experience with factor-Xa inhibition in percutaneous coronary intervention: the XaNADU-PCI Pilot

BACKGROUND

Direct factor (F)Xa inhibition is an attractive method to limit thrombotic complications during percutaneous coronary intervention (PCI).

OBJECTIVES

To investigate drug levels achieved, effect on coagulation markers, and preliminary efficacy and safety of several doses of DX-9065a, an intravenous, small molecule, direct, reversible FXa inhibitor during PCI.

PATIENTS AND METHODS

Patients undergoing elective, native-vessel PCI (n = 175) were randomized 4 : 1 to open-label DX-9065a or heparin in one of four sequential stages. DX-9065a regimens in stages I-III were designed to achieve concentrations of > 100 ng mL-1, > 75 ng mL-1, and > 150 ng mL-1. Stage IV used the stage III regimen but included patients recently given heparin.

RESULTS

At 15 min median (minimum) DX-9065a plasma levels were 192 (176), 122 (117), 334 (221), and 429 (231) ng mL-1 in stages I-IV, respectively. Median whole-blood international normalized ratios (INRs) were 2.6 (interquartile range 2.5, 2.7), 1.9 (1.8, 2.0), 3.2 (3.0, 4.1), and 3.8 (3.4, 4.6), and anti-FXa levels were 0.36 (0.32, 0.38), 0.33 (0.26, 0.39), 0.45 (0.41, 0.51), and 0.62 (0.52, 0.65) U mL-1, respectively. Stage II enrollment was stopped (n = 7) after one serious thrombotic event. Ischemic and bleeding events were rare and, in this small population, showed no clear relation to DX-9065a dose.

CONCLUSIONS

Elective PCI is feasible using a direct FXa inhibitor for anticoagulation. Predictable plasma drug levels can be rapidly obtained with double-bolus and infusion DX-9065a dosing. Monitoring of DX-9065a may be possible using whole-blood INR. Direct FXa inhibition is a novel and potentially promising approach to anticoagulation during PCI that deserves further study.

Influence of human immunodeficiency virus type 1 envelope glycoprotein YXXL endocytosis/polarization signal on viral accessory protein functions

INTRODUCTION

A tyrosine-based targeting signal in the intracytoplasmic domain of human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein is required for basolateral targeting of viral budding in polarized epithelial cells, concentration of viral assembly at one pole of infected lymphocytes, and rapid endocytosis of the glycoprotein from the plasma membrane. In HIV-1, the process of viral assembly and budding is complex and involves the participation of viral accessory proteins.

STUDY DESIGN/METHODS

In this study, we examined whether the functions of the Nef, Vif, and Vpu proteins can influence or be influenced by the presence of envelope targeting signal in epithelial cells or lymphocytes. A series of proviral DNAs combining a mutation that inactivates the targeting signal with independent mutations in the three accessory proteins was constructed for this purpose.

RESULTS

It was found that none of these three accessory proteins affected the basolateral release of the virus in polarized MDCK cells. Reciprocally, a mutation abolishing targeting of the viral envelope glycoprotein did not affect the phenotype conferred by the accessory proteins. Interestingly, the mutation abolishing targeting increased viral infectivity only in the presence of the Vpu protein. This phenotype was found to be associated with the release-enhancing function of Vpu and with an increased incorporation of viral envelope glycoprotein in virions.

CONCLUSIONS

These data clearly show that accessory protein functions, and more specifically Vpu modulation of viral infectivity, can be affected by variations in the viral envelope glycoprotein.

Severe thrombocytopenia possibly related to readministration of eptifibatide

Thrombocytopenia following eptifibatide therapy is a rare event, and acute severe thrombocytopenia following readministration has not been reported. We describe a case of acute severe thrombocytopenia following reexposure to eptifibatide during percutaneous coronary intervention. We continue to monitor platelet counts at 2-4 hr and 16-24 hr following administration of any glycoprotein IIb/IIIa inhibitor. Cathet Cardiovasc Intervent 2001;54:63-67.

Predictors of improvement in left ventricular function after percutaneous revascularization of occluded coronary arteries: a report from the Total Occlusion Study of Canada (TOSCA)

BACKGROUND

The Total Occlusion Study of Canada (TOSCA) is a multicenter, randomized trial evaluating the effect of stenting with > =1 heparin-coated stent on long-term patency after percutaneous coronary intervention by balloon angioplasty of occluded coronary arteries. The purpose of the current study was to compare the effect of stenting and balloon angioplasty on global left ventricular ejection fraction (LVEF) and regional wall motion and to examine what clinical and angiographic factors may have an effect on left ventricular function in this setting.

METHODS AND RESULTS

Analysis at the core angiographic laboratory of paired baseline and follow-up left ventricular angiograms, as well as target vessel patency, was possible in 244 of 410 cases. An improvement in LVEF was observed in the entire group (59.4% +/- 11% to 61.0% +/- 11%, P =.003). The LVEF change was +1.84 +/- 7.54 in the stent group (P =.009) and 1.28 +/- 8.16 in the percutaneous transluminal coronary angioplasty group (P =.085). There was no significant intergroup difference. Patients with duration of occlusion < or =6 weeks had an improvement in LVEF (+2.98 +/- 8.68, P =.0006), whereas those with an occlusion duration of > 6 weeks had no improvement (+0.48 +/- 7.01, P not significant). Multivariate analysis revealed baseline LVEF <60%, duration of occlusion < or =6 weeks, and Canadian Cardiology Society angina class I or II to be independent predictors of improvement in LVEF.

CONCLUSIONS

The restoration of coronary patency of nonacute occluded coronary arteries is associated with a small but significant improvement in regional and global left ventricular function, especially in patients with recent occlusions and depressed left ventricular function. In spite of significant effect on long-term patency, stenting of nonacute coronary occlusions does not result in significantly better left ventricular function compared with balloon angioplasty in this setting.

Comparison of two platelet glycoprotein IIb/IIIa inhibitors, tirofiban and abciximab, for the prevention of ischemic events with percutaneous coronary revascularization

BACKGROUND

In the setting of percutaneous coronary revascularization, agents in the class known as platelet glycoprotein IIb/IIIa inhibitors have significantly reduced the incidence of death or nonfatal myocardial infarction at 30 days. We assessed whether there are differences in safety or efficacy between two such inhibitors, tirofiban and abciximab.

METHODS

Using a double-blind, double-dummy design at 149 hospitals in 18 countries, we randomly assigned patients to receive either tirofiban or abciximab before undergoing percutaneous coronary revascularization with the intent to perform stenting. The primary end point was a composite of death, nonfatal myocardial infarction, or urgent target-vessel revascularization at 30 days. The trial was designed and statistically powered to demonstrate the noninferiority of tirofiban as compared with abciximab.

RESULTS

The primary end point occurred more frequently among the 2398 patients in the tirofiban group than among the 2411 patients in the abciximab group (7.6 percent vs. 6.0 percent; hazard ratio, 1.26; one-sided 95 percent confidence interval of 1.51, demonstrating lack of equivalence, and two-sided 95 percent confidence interval of 1.01 to 1.57, demonstrating the superiority of abciximab over tirofiban; P=0.038). The magnitude and the direction of the effect were similar for each component of the composite end point (hazard ratio for death, 1.21; hazard ratio for myocardial infarction, 1.27; and hazard ratio for urgent target-vessel revascularization, 1.26), and the difference in the incidence of myocardial infarction between the tirofiban group and the abciximab group was significant (6.9 percent and 5.4 percent, respectively; P=0.04). The relative benefit of abciximab was consistent regardless of age, sex, the presence or absence of diabetes, or the presence or absence of pretreatment with clopidogrel. There were no significant differences in the rates of major bleeding complications or transfusions, but tirofiban was associated with a lower rate of minor bleeding episodes and thrombocytopenia.

CONCLUSIONS

Although the trial was intended to assess the noninferiority of tirofiban as compared with abciximab, the findings demonstrated that tirofiban offered less protection from major ischemic events than did abciximab.

Human Jurkat lymphocytes clones differ in their capacity to support productive human immunodeficiency virus type 1 multiplication

CD4-positive human lymphocytic cell lines are essential tools for the study of human immunodeficiency virus (HIV) replication. Jurkat cells are among cells more frequently used for this purpose. In the current study, various cell clones or cells stocks derived from this cell line were shown to vary substantially in their response to viral infection and in their ability to support productive virus multiplication. The formation of syncytia, the effect of Vpu on viral export, and especially the specific infectivity of the viruses released, can vary significantly among independent cell stocks. This suggests that the choice of an adequate cell clone or cell line could be critical while evaluating specific properties of the virus and further stresses the limitations of tissue culture models. However, these observations also raise the possibility of exploiting these differences among cells to study specific aspects of host-cell interactions contributing to viral multiplication.

RNA trafficking signals in human immunodeficiency virus type 1

Intracellular trafficking of retroviral RNAs is a potential mechanism to target viral gene expression to specific regions of infected cells. Here we show that the human immunodeficiency virus type 1 (HIV-1) genome contains two sequences similar to the hnRNP A2 response element (A2RE), a cis-acting RNA trafficking sequence that binds to the trans-acting trafficking factor, hnRNP A2, and mediates a specific RNA trafficking pathway characterized extensively in oligodendrocytes. The two HIV-1 sequences, designated A2RE-1, within the major homology region of the gag gene, and A2RE-2, in a region of overlap between the vpr and tat genes, both bind to hnRNP A2 in vitro and are necessary and sufficient for RNA transport in oligodendrocytes in vivo. A single base change (A8G) in either sequence reduces hnRNP A2 binding and, in the case of A2RE-2, inhibits RNA transport. A2RE-mediated RNA transport is microtubule and hnRNP A2 dependent. Differentially labelled gag and vpr RNAs, containing A2RE-1 and A2RE-2, respectively, coassemble into the same RNA trafficking granules and are cotransported to the periphery of the cell. tat RNA, although it contains A2RE-2, is not transported as efficiently as vpr RNA. An A2RE/hnRNP A2-mediated trafficking pathway for HIV RNA is proposed, and the role of RNA trafficking in targeting HIV gene expression is discussed.

In vitro and in vivo comparison of three different intravascular ultrasound catheter designs

Intravascular ultrasound (IVUS) is an invasive imaging modality, which provides detailed two-dimensional images of blood vessels. There are currently two different types of IVUS catheters available, namely, the phased-array and the mechanical designs. The operating ultrasound frequency of these catheters ranges from 20 to 40 MHz. This study sought to evaluate the image quality, accuracy of diameter and pullback length measurements, and catheter handling characteristics of three different IVUS catheters currently available for clinical use using both in vitro phantom models and in patients undergoing percutaneous coronary intervention (PCI). In gelatin phantom models, image quality assessed on a semiquantitative scale was significantly different between the three IVUS catheters (P = 0.01) with the 40-MHz catheter providing the best images. Accuracy of lumen diameter measurements, when compared to optical microscopy, were similar between the three IVUS catheter designs (all R(2) = 0.99). There were no significant differences in accuracy of pullback length measurements in vitro between the three designs. However, there were differences in the performance of the three IVUS catheters when used for preinterventional imaging in patients undergoing PCI. Both mechanical IVUS catheters were associated with lower procedural, fluoroscopy, and lesion crossing times compared to the phased-array catheter (all P < 0.05). There were no significant differences between the catheters during postinterventional IVUS imaging. There were also small but potentially important differences with regards to clinical events and complications associated with the use of the different IVUS catheters during the PCI procedures, reflecting differences in catheter design.

Bleeding risks with abciximab after full-dose thrombolysis in rescue or urgent angioplasty for acute myocardial infarction

BACKGROUND

The bleeding risk associated with platelet glycoprotein IIb/IIIa inhibition in patients undergoing percutaneous transluminal coronary angioplasty (PTCA) after full-dose thrombolysis for acute myocardial infarction (AMI) is unclear. We examined the risk and predictors of bleeding complications in patients with AMI who received abciximab during rescue or urgent PTCA after full-dose thrombolytic therapy.

METHODS

A multicenter retrospective cohort of 147 consecutive patients who underwent PTCA within 48 hours after full-dose thrombolysis for AMI was studied. Bleeding events (major, minor, nuisance) from the onset of AMI to discharge were compared between those who received abciximab (n = 57) and those who did not (n = 90).

RESULTS

Baseline clinical characteristics were similar between the two groups. Despite lower doses of procedural heparin, the incidence of non-coronary artery bypass graft-related major and minor bleeding was higher in the abciximab group than in controls (63% vs 39%, P =.004). Although the risk of major bleeding was 4-fold with abciximab (12% vs 3%, P =.04), only one intracranial and one fatal bleeding event occurred. Multivariable regression identified abciximab therapy as the most powerful independent predictor of combined major and minor bleeding, with a hazard risk ratio of 1.9 (P =.04).

CONCLUSIONS

In the setting of rescue or urgent PTCA within 48 hours after full-dose thrombolytic therapy after AMI, major and particularly minor bleeding were frequently encountered. The adjunctive use of abciximab increased these bleeding risks by approximately 2-fold.

Y stenting of a bifurcation stenosis using a new radiopaque stent

A case of Y stenting using radiopaque stents for a bifurcation stenosis is described. Angiography and intravascular ultrasound demonstrate that in spite of optimal stent placement there is an area of the lesion that is not fully covered by the stents. This may predispose to subacute thrombosis and restenosis. This case illustrates a potential deficiency of this type of bifurcation stenting.

The Rotational Spectra, Isotopically Independent Parameters, and Interatomic Potentials for the X(1)(2)Pi(3/2) and X(2)(2)Pi(1/2) States of BrO

Observations of the rotational spectrum of BrO have been extended to include vibrational levels up to v = 8 in the X(1)(2)Pi(3/2) and v = 7 in the X(2)(2)Pi(1/2) states. The rotational spectra of isotopically enriched Br(18)O, X(1), v = 0, 1 and X(2), v = 0 have been observed as well. The spectra of all four isotopic species have been fit to a Hamiltonian in which the parameters have fixed isotopic ratios. An extensive set of isotopically independent parameters has been determined. Interatomic potentials have been derived for both the X(1) and X(2) states. The hyperfine constants and their vibrational dependencies have been determined more precisely and several of them have been determined for the first time. These are interpreted in terms of the electronic structure of the molecule. The isotope relations among the constants have provided a means of decorrelating the electron spin-rotation constant gamma from the fine-structure centrifugal distortion constant, A(D), and have allowed the first determination of an effective value for gamma. Copyright 2001 Academic Press.

Hematologic dyscrasia associated with ticlopidine therapy: evidence for causality

BACKGROUND

Several rare, potentially fatal types of hematologic dyscrasia, such as agranulocytosis, aplastic anemia, neutropenia, pancytopenia, thrombocytopenia and thrombotic thrombocytopenic purpura (TTP), have been associated with ticlopidine therapy. The extent to which ticlopidine is the causative factor has not been addressed quantitatively.

METHODS

We identified 211 published case reports of hematologic dyscrasia associated with ticlopidine therapy from a MEDLINE search. We analyzed the 91 reports that could be evaluated, using the Bayesian Adverse Reaction Diagnostic Instrument to calculate the posterior probability that ticlopidine caused the hematologic dyscrasia based on epidemiologic and clinical trial data (prior odds) and case information (likelihood ratio).

RESULTS

The median posterior probability values (and range) for agranulocytosis, aplastic anemia, neutropenia, pancytopenia, thrombocytopenia and TTP were 0.95 (0.53-0.98), 0.81 (0.57-0.93), 0.86 (0.75-0.96), 0.78 (0.61-0.89), 0.74 (0-0.92) and 1.0 (0.33-1.00) respectively. The posterior probability was 0.75 or greater in 82 (90%) of the case reports.

INTERPRETATION

This systematic analysis provides stronger evidence to implicate ticlopidine as the causative factor in the various types of hematologic dyscrasia in most published case reports.

Human immunodeficiency virus type 1 Vpr-mediated G(2) cell cycle arrest: Vpr interferes with cell cycle signaling cascades by interacting with the B subunit of serine/threonine protein phosphatase 2A

The Vpr protein of primate lentiviruses arrests cell cycling at the G(2)/M phase through an inactivation of cyclin B-p34(cdc2) and its upstream regulator cdc25. We provide here biochemical and functional evidence demonstrating that human immunodeficiency virus type 1 (HIV-1) Vpr mediates G(2) arrest by forming a complex with protein phosphatase 2A (PP2A), an upstream regulator of cdc25. Vpr associates with PP2A through a specific interaction with the B55 regulatory subunit. This interaction is necessary but not sufficient for G(2) arrest. Interestingly, we found that Vpr association with B55-containing PP2A targets the enzymatic complex to the nucleus and, importantly, enhances the recruitment and dephosphorylation of the cdc25 substrate. Our data suggest that Vpr mediates G(2) arrest by enhancing the nuclear import of PP2A and by positively modulating its catalytic activity towards active phosphorylated nuclear cdc25.

The double-stranded RNA-binding protein Staufen is incorporated in human immunodeficiency virus type 1: evidence for a role in genomic RNA encapsidation

Human Staufen (hStau), a double-stranded RNA (dsRNA)-binding protein that is involved in mRNA transport, is incorporated in human immunodeficiency virus type 1 (HIV-1) and in other retroviruses, including HIV-2 and Moloney murine leukemia virus. Sucrose and Optiprep gradient analyses reveal cosedimentation of hStau with purified HIV-1, while subtilisin assays demonstrate that it is internalized. hStau incorporation in HIV-1 is selective, is dependent on an intact functional dsRNA-binding domain, and quantitatively correlates with levels of encapsidated HIV-1 genomic RNA. By coimmunoprecipitation and reverse transcription-PCR analyses, we demonstrate that hStau is associated with HIV-1 genomic RNA in HIV-1-expressing cells and purified virus. Overexpression of hStau enhances virion incorporation levels, and a corresponding, threefold increase in HIV-1 genomic RNA encapsidation levels. This coordinated increase in hStau and genomic RNA packaging had a significant negative effect on viral infectivity. This study is the first to describe hStau within HIV-1 particles and provides evidence that hStau binds HIV-1 genomic RNA, indicating that it may be implicated in retroviral genome selection and packaging into assembling virions.

Activation of transcription factors NF-kappaB and NF-IL-6 by human immunodeficiency virus type 1 protein R (Vpr) induces interleukin-8 expression

Human immunodeficiency virus (HIV)-positive individuals express elevated levels of interleukin-8 (IL-8), which is believed to be responsible for some of the clinical manifestations occurring during AIDS. We report here that virion-derived HIV type 1 (HIV-1) protein R (Vpr) increased IL-8 expression in primary T cells and macrophages, as well as in the T-cell line Jurkat, the monocytic cell line U937, and the epithelial cell line A549. Vpr appeared to increase IL-8 expression and IL-8 promoter activity by activating transcription factors NF-kappaB and NF-IL-6. Elevated Vpr was also shown to increase transcription of the NF-kappaB and NF-IL-6 enhancer-containing viral promoters for HIV, cytomegalovirus, and simian virus 40, as well as increase the expression of IL-6 and IL-10 in primary macrophages and in A549 cells, tumor necrosis factor alpha expression in primary T cells, and IL-6 and gamma interferon expression in U937 cells. These results suggest a new role for Vpr in the pathogenesis of HIV infection, namely, the activation of transcription factors NF-IL-6 and NF-kappaB.

The Rotational Spectrum of SO(2) and the Determination of the Hyperfine Constants and Nuclear Magnetic Shielding Tensors of (33)SO(2) and SO(17)O

Precise frequencies for the 1(11)-2(02) transition of (33)SO(2) and SO(17)O in natural isotopic abundance have been obtained near 12 GHz by microwave Fourier transform spectroscopy in order to yield improved hyperfine constants. Nuclear spin-rotation coupling constants have been determined experimentally for (33)SO(2) for the first time. The spin-rotation constants have been used to derive nuclear magnetic shielding parameters. These parameters are compared with values for the isoelectronic O(3) molecule. The transition mentioned above was also measured for (32)SO(2), (34)SO(2), SO(18)O, and vibrationally excited (v(2) = 1) (32)SO(2). For (33)SO(2), some transitions with large hyperfine splitting were also recorded in the millimeter-wave region. Continuing our investigations of the rotational spectra of SO(2) in the submillimeter region, several transitions of SO(17)O have been recorded with the Cologne terahertz spectrometer between 540 and 840 GHz with J and K(a) up to 63 and 16, respectively. Transitions with high K(a), up to 28, have been recorded with the JPL laser sideband spectrometer between 1.8 and 3.2 THz. Copyright 2000 Academic Press.

Fairness in the coronary angiography queue

BACKGROUND

Since waiting lists for coronary angiography are generally managed without explicit queuing criteria, patients may not receive priority on the basis of clinical acuity. The objective of this study was to examine clinical and nonclinical determinants of the length of time patients wait for coronary angiography.

METHODS

In this single-centre prospective cohort study conducted in the autumn of 1997, 357 consecutive patients were followed from initial triage until a coronary angiography was performed or an adverse cardiac event occurred. The referring physicians' hospital affiliation (physicians at Sunnybrook & Women's College Health Sciences Centre, those who practice at another centre but perform angiography at Sunnybrook and those with no previous association with Sunnybrook) was used to compare processes of care. A clinical urgency rating scale was used to assign a recommended maximum waiting time (RMWT) to each patient retrospectively, but this was not used in the queuing process. RMWTs and actual waiting times for patients in the 3 referral groups were compared; the influence clinical and nonclinical variables had on the actual length of time patients waited for coronary angiography was assessed; and possible predictors of adverse events were examined.

RESULTS

Of 357 patients referred to Sunnybrook, 22 (6.2%) experienced adverse events while in the queue. Among those who remained, 308 (91.9%) were in need of coronary angiography; 201 (60.0%) of those patients received one within the RMWT. The length of time to angiography was influenced by clinical characteristics similar to those specified on the urgency rating scale, leading to a moderate agreement between actual waiting times and RMWTs (kappa = 0.53). However, physician affiliation was a highly significant (p < 0.001) and independent predictor of waiting time. Whereas 45.6% of the variation in waiting time was explained by all clinical factors combined, 9.3% of the variation was explained by physician affiliation alone.

INTERPRETATION

Informal queuing practices for coronary angiography do reflect clinical acuity, but they are also influenced by nonclinical factors, such as the nature of the physicians' association with the catheterization facility.

Complementary clinical benefits of coronary-artery stenting and blockade of platelet glycoprotein IIb/IIIa receptors. Evaluation of Platelet IIb/IIIa Inhibition in Stenting Investigators

BACKGROUND

Inhibition of the platelet glycoprotein IIb/IIIa receptor with the monoclonal-antibody fragment abciximab reduces the acute ischemic complications associated with percutaneous coronary revascularization, whereas coronary-stent implantation reduces restenosis. We conducted a trial to determine the efficacy of abciximab and stent implantation in improving long-term outcome.

METHODS

A total of 2399 patients were randomly assigned to stent implantation and placebo, stent implantation and abciximab, or balloon angioplasty and abciximab. The patients were followed for six months.

RESULTS

At six months, the incidence of the composite end point of death or myocardial infarction was 11.4 percent in the group that received a stent and placebo, as compared with 5.6 percent in the group that received a stent and abciximab (hazard ratio, 0.47; 95 percent confidence interval, 0.33 to 0.68; P<0.001) and 7.8 percent in the group assigned to balloon angioplasty and abciximab (hazard ratio, 0.67; 95 percent confidence interval, 0.49 to 0.92; P=0.01). The hazard ratio for stenting plus abciximab as compared with angioplasty plus abciximab was 0.70 (95 percent confidence interval, 0.48 to 1.04; P=0.07). The rate of repeated revascularization of the target vessel was 10.6 percent in the stent-plus-placebo group, as compared with 8.7 percent in the stent-plus-abciximab group (hazard ratio, 0.82; 95 percent confidence interval, 0.59 to 1.13; P=0.22) and 15.4 percent in the angioplasty-plus-abciximab group (hazard ratio, 1.49; 95 percent confidence interval, 1.13 to 1.97; P=0.005). The hazard ratio for stenting plus abciximab as compared with angioplasty plus abciximab was 0.55 (95 percent confidence interval, 0.41 to 0.74; P<0.001). Among patients with diabetes, the combination of abciximab and stenting was associated with a lower rate of repeated target-vessel revascularization (8.1 percent) than was stenting and placebo (16.6 percent, P=0.02) or angioplasty and abciximab (18.4 percent, P=0.008).

CONCLUSIONS

For coronary revascularization, abciximab and stent implantation confer complementary long-term clinical benefits.

Primary stenting versus balloon angioplasty in occluded coronary arteries: the Total Occlusion Study of Canada (TOSCA)

BACKGROUND

Balloon angioplasty (PTCA) of occluded coronary arteries is limited by high rates of restenosis and reocclusion. Although stenting improves results in anatomically simple occlusions, its effect on patency and clinical outcome in a broadly selected population with occluded coronary arteries is unknown.

METHODS AND RESULTS

Eighteen centers randomized 410 patients with nonacute native coronary occlusions to PTCA or primary stenting with the heparin-coated Palmaz-Schatz stent. The primary end point, failure of sustained patency, was determined at 6-month angiography. Repeat target-vessel revascularization, adverse cardiovascular events, and angiographic restenosis (>50% diameter stenosis) constituted secondary end points. Sixty percent of patients had occlusions of >6 weeks' duration, baseline flow was TIMI grade 0 in 64%, and median treated segment length was 30.5 mm. With 95.6% angiographic follow-up, primary stenting resulted in a 44% reduction in failed patency (10.9% versus 19.5%, P=0.024) and a 45% reduction in clinically driven target-vessel revascularization at 6 months (15.4% versus 8.4%, P=0.03). The incidence of adverse cardiovascular events was similar for both strategies (PTCA, 23.6%; stent, 23.3%; P=NS). Stenting resulted in a larger mean 6-month minimum lumen dimension (1.48 versus 1.23 mm, P<0.01) and a reduced binary restenosis rate (55% versus 70%, P<0.01).

CONCLUSIONS

Primary stenting of broadly selected nonacute coronary occlusions is superior to PTCA alone, improving late patency and reducing restenosis and target-vessel revascularization.

Polarized human immunodeficiency virus budding in lymphocytes involves a tyrosine-based signal and favors cell-to-cell viral transmission

Maturation and release of human immunodeficiency virus type 1 (HIV-1) is targeted at the pseudopod of infected mononuclear cells. However, the intracellular mechanism or targeting signals leading to this polarized viral maturation are yet to be identified. We have recently demonstrated the presence of a functional YXXL motif for specific targeting of HIV-1 virions to the basolateral membrane surface in polarized epithelial Madin-Darby canine kidney cells (MDCK). Site-directed mutagenesis was used to demonstrate that the membrane-proximal tyrosine in the intracytoplasmic tail of the HIV-1 transmembrane glycoprotein (gp41) is an essential component of this signal. In the present study, immunolocalization of viral budding allowed us to establish that this tyrosine-based signal is involved in determining the exact site of viral release at the surface of infected mononuclear cells. Substitution of the critical tyrosine residue was also shown to increase the amount of envelope glycoprotein at the cell surface, supporting previous suggestions that the tyrosine-based motif can promote endocytosis. Although alteration of the dual polarization-endocytosis motif did not affect the infectivity of cell-free virus, it could play a key role in cell-to-cell viral transmission. Accordingly, chronically infected lymphocytes showed a reduced ability to transmit the mutant virus to a cocultivated cell line. Overall, our data indicate that the YXXL targeting motif of HIV is active in various cell types and could play an important role in viral propagation; this may constitute an alternative target for HIV therapeutics and vaccine development.

Trends in clinical and economic outcomes of coronary angioplasty from 1992 to 1995: a population-based analysis

BACKGROUND

The impact of recent developments in coronary angioplasty on the broad spectrum of patients treated in routine practice is largely undefined. Analysis of population-based data can provide insight into trends in clinical outcomes and associated costs of coronary angioplasty procedures.

METHODS AND RESULTS

With the use of a comprehensive hospital discharge database covering more than 11 million Canadians, we analyzed 12,748 first-time angioplasty procedures performed from 1992 to 1995 inclusive. Patient demographics and major adverse events were recorded. With the use of forward linkage, readmissions within 12 months were classified according to procedure performed and/or most responsible diagnosis. The proportion of patients readmitted, the number of readmissions per index procedure, and diagnosis-specific readmission costs were compared by calendar year. Over the 4-year study period, there was a 21% increase in the annual volume of index procedures. There were no statistically significant differences between 1992 and 1995 in sex distribution, mean age, comorbid conditions, length of stay, or need for coronary bypass surgery related to the index procedure. The all-cause readmission rate declined from 51.6% to 47.2% between 1992 and 1995 (P <.001), primarily because of a decline in the admission rate for repeat revascularization from 24.8% to 19.6% (P <.001). The 12-month readmission cost declined by $435 (1994 Canadian dollars) per patient.

CONCLUSIONS

The clinical outcomes of coronary angioplasty in a broad cohort of patients have improved in recent years. Although readmissions within 1 year of an angioplasty procedure remain common, the number related to repeat revascularization has declined, with an associated decline in downstream costs.

Human immunodeficiency virus type 1 (HIV-1) Vpr functions as an immediate-early protein during HIV-1 infection

Human immunodeficiency virus type 1 (HIV-1) Vpr is a virion-associated protein which facilitates HIV-1 infection of nondividing cells by contributing to the nuclear transport of the preintegration complex (PIC). Vpr was also shown to induce a cell cycle G2 arrest in infected proliferating cells that optimizes HIV-1 long terminal repeat (LTR)-directed gene expression and viral production. However, it is unclear whether this activity is mediated primarily early by virion-associated Vpr or alternatively late during infection when Vpr is de novo expressed. We report here that in the absence of de novo expression, virion-associated Vpr induces a transient G2 arrest that can subsequently lead to cell killing by apoptosis. Interestingly, the induction of both cell cycle G2 arrest and apoptosis by virion-associated Vpr requires viral entry but not viral replication, since reverse transcriptase and protease inhibitor treatments do not prevent these Vpr effects. These results raise the possibility that in vivo both infectious and noninfectious viruses contribute to the dysfunction and killing of CD4(+) cells. In addition, our results reveal that virion-associated Vpr stimulates viral replication in proliferating cells after establishing a cell cycle G2 arrest by increasing LTR-directed gene expression. Importantly, this Vpr-mediated LTR activation appears to be a requirement for subsequent optimal Tat transactivation. Taken together, these results strongly suggest that in addition to participating in the HIV PIC nuclear transport in nondividing cells, virion-associated Vpr activates HIV-1 LTR-directed gene expression by manipulating the host cell cycle. From this, we conclude that Vpr functions as an immediate-early protein during HIV-1 infection.

Incorporation of Vpr into human immunodeficiency virus type 1 requires a direct interaction with the p6 domain of the p55 gag precursor

The 96-amino acid Vpr protein is the major virion-associated accessory protein of the human immunodeficiency virus type 1 (HIV-1). As Vpr is not part of the p55 Gag polyprotein precursor (Pr55(gag)), its incorporation requires an anchor to associate with the assembling viral particles. Although the molecular mechanism is presently unclear, the C-terminal region of the Pr55(gag) corresponding to the p6 domain appears to constitute such an anchor essential for the incorporation of the Vpr protein. In order to clarify the mechanism by which the Vpr accessory protein is trans-incorporated into progeny virion particles, we tested whether HIV-1 Vpr interacted with the Pr55(gag) using the yeast two-hybrid system and the maltose-binding protein pull-down assay. The present study provides genetic and biochemical evidence indicating that the Pr55(gag) can physically interact with the Vpr protein. Furthermore, point mutations affecting the integrity of the conserved L-X-S-L-F-G motif of p6(gag) completely abolish the interaction between Vpr and the Pr55(gag) and, as a consequence, prevent Vpr virion incorporation. In contrast to other studies, mutations affecting the integrity of the NCp7 zinc fingers impaired neither Vpr virion incorporation nor the binding between Vpr and the Pr55(gag). Conversely, amino acid substitutions in Vpr demonstrate that an intact N-terminal alpha-helical structure is essential for the Vpr-Pr55(gag) interaction. Vpr and the Pr55(gag) demonstrate a strong interaction in vitro as salt concentrations as high as 900 mM could not disrupt the interaction. Finally, the interaction is efficiently competed using anti-Vpr sera. Together, these results strongly suggest that Vpr trans-incorporation into HIV-1 particles requires a direct interaction between its N-terminal region and the C-terminal region of p6(gag). The development of Pr55(gag)-Vpr interaction assays may allow the screening of molecules that can prevent the incorporation of the Vpr accessory protein into HIV-1 virions, and thus inhibit its early functions.

Noncritical disease of the left main coronary artery: limitations of angiography and the role of intravascular ultrasound

OBJECTIVE

To review the diagnosis and management of noncritical left main stem disease.

DATA SOURCES

MEDLINE was searched using the key phrases 'intravascular ultrasound' and 'left main coronary artery'.

DATA EXTRACTION

Articles addressing the angiographic or ultrasound assessment of left main stem disease were systematically reviewed. Reference is also made to articles dealing with outcomes for patients with left main stem disease.

DATA SYNTHESIS

The assessment of left main stem disease by coronary angiography is often suboptimal. Intravascular ultrasound has demonstrated significant left main stem disease in angiographically normal arteries. It has also demonstrated that mild to moderate left main stem disease frequently accompanies disease in the other coronary arteries. The natural history of mild to moderate left main stem disease has not been well characterized; thus, the optimum management of this condition is not known.

CONCLUSIONS

To establish the natural history of noncritical left main stem stenosis, it is proposed that centres performing frequent intravascular ultrasound examinations systematically and quantitatively interrogate the left main stem during all left coronary examinations. Angiographic and ultrasonic measures of left main stem disease can then be correlated with clinical outcome during long term follow-up. This will clearly require the collaboration of several centres to generate a sufficiently large database to address these clinical questions.

Human immunodeficiency virus type 1 vpr protein transactivation function: mechanism and identification of domains involved

The human immunodeficiency virus type 1 (HIV-1) Vpr protein is a virion-associated protein that localizes in the nucleus of infected cells. Vpr has been shown to facilitate HIV infection of non-dividing cells such as macrophages by contributing to the nuclear translocation of the pre-integration complex. More recently, Vpr expression has been shown to induce an accumulation of cells at the G2 phase of the cell-cycle. We have previously reported that Vpr stimulates reporter gene expression directed from the HIV-1 long terminal repeat (LTR) as well as from heterologous viral promoters. However, the mode of action of Vpr-mediated transactivation remains to be precisely defined. We report here that, for a constant amount of transfected DNA, the level of chloramphenicol acetyltransferase (CAT) mRNA is increased in Vpr-expressing cells using either HIV-1 or a murine leukemia virus (MLV) SL3-3 LTR-CAT reporter construct. Moreover, this Vpr-mediated transactivation requires that promoters direct a minimal level of basal expression. Our mutagenic analysis indicates that the transactivation mediated by Vpr is not dependent on the ability of the protein to localize in the nucleus or to be packaged in the virions. Interestingly, all transactivation-competent Vpr mutants were still able to induce a cell-cycle arrest. Conversely, transactivation-defective mutants lost the ability to mediate cell-cycle arrest, implying a functional relationship between these two functions. Overall, our results indicate that the G2 cell-cycle arrest mediated by Vpr creates a cellular environment where the HIV-1 LTR is transcriptionally more active.

Failed coronary stent deployment

BACKGROUND

Coronary stent deployment failure may be more common in clinical practice than generally appreciated. The incidence of failed deployment in routine clinical practice and the clinical sequelae have not been described. This study sought to determine the incidence and consequences of failed coronary stent deployment and to identify clinical and angiographic characteristics associated with deployment failure.

METHODS AND RESULTS

A series of 1303 consecutive procedures involving attempted coronary stenting were reviewed retrospectively. Failed stent deployment was defined as failure of the stent to be either delivered to or adequately deployed at the target lesion site. Clinical records and angiograms were reviewed and qualitative coronary angiography was performed for all cases of failed deployment. Deployment was unsuccessful in 108 (8.3%) cases involving 134 stents. Stenting was attempted as a primary procedure in 40%, as bailout in 18%, and for suboptimal angioplasty in 43% of cases. In 87% of cases, attempts were made to withdraw the stent from the coronary artery. Stent retrieval was successful in 45%, peripheral embolization occurred in 38% of patients, and in 4% the stent dislodged in the left main artery. In 35% of cases, additional stent(s) were successfully deployed. Deployment failure was associated with an overall in-hospital adverse outcome in 19% of patients, including 16% urgent coronary artery bypass grafting, 5% nonfatal myocardial infarction, and 3 in-hospital deaths. At 6-month follow-up, 39% of patients had had at least 1 adverse clinical outcome of death, myocardial infarction, or repeat target lesion revascularization.

CONCLUSIONS

Failure to deploy stents is a serious and relatively common problem that is associated with significant morbidity and mortality rates. Improved deployment strategies, including new stent designs, are required to improve procedural outcomes.

Structural and functional analysis of the membrane-spanning domain of the human immunodeficiency virus type 1 Vpu protein

The human immunodeficiency virus type 1 (HIV-1) vpu gene product is a class I integral membrane phosphoprotein that is capable of oligomerization. Two distinct biological activities have been attributed to Vpu: induction of CD4 degradation in the endoplasmic reticulum and enhancement of viral particle release from the plasma membrane of infected cells. These two biological activities were shown to involve two separable structural domains: the N-terminal transmembrane (TM) domain and the C-terminal cytoplasmic domain. The TM domain mediates enhancement of viral particle release, whereas phosphorylation of the cytoplasmic domain is essential for Vpu-induced CD4 degradation. In this study, we performed a mutational analysis of the TM domain of Vpu to delineate amino acids that are important in the process of viral particle release or in Vpu-induced CD4 degradation. Substitution of conserved amino acids from the N-terminal, middle, or C-terminal parts of the native VpuTM domain generated proteins that integrated normally into canine pancreatic microsomal membranes, exhibited subcellular localization similar to those of wild-type Vpu, but partially lost their ability to enhance viral particle release, strongly suggesting that the VpuTM domain contains determinants responsible for Vpu-mediated enhancement of viral particle release. Interestingly, the C-terminal TM mutant VpuIVW, in contrast to the other mutants, also lost its ability to bind and consequently degrade the CD4 molecule, indicating that the alteration of the C-terminal part of the TM did interfere with this function of Vpu. Taken together, our study supports the notion that both structural elements of Vpu (TM and cytoplasmic) contribute to the biological activities of Vpu.

Multiple arterial grafts. Radial versus right internal thoracic arteries

BACKGROUND

Left internal thoracic artery (LITA) grafts to the left anterior descending coronary artery (LAD) during coronary bypass surgery (CABG) have greater patency rates than saphenous vein grafts and reduce long-term cardiac morbidity and mortality rates. The benefits of multiple versus single arterial grafts and the role of different arterial conduits with respect to short- and medium-term outcome remains controversial. The purpose of this study was to compare the perioperative and intermediate-term results of: (1) patients receiving 2 arterial grafts versus 1 arterial graft and (2) patients receiving a right internal thoracic artery (RITA) versus a radial artery (RA) as the second arterial graft.

METHODS AND RESULTS

Retrospective analysis of prospectively gathered data on consecutive patients undergoing isolated CABG at our institution between 1989 and 1996 was conducted. The first section of the study compared outcomes for 1 arterial graft (LITA to LAD, n = 2333) versus 2 arterial grafts (LITA + RA or LITA + RITA, n = 378). The second section of the study compared outcomes for the RITA (n = 132) versus the RA (n = 171) as second arterial grafts since 1992, when the radial series was initiated. Part I: By multivariable stepwise logistic regression, the use of 1 arterial graft was associated with an increased incidence of perioperative cardiac morbidity and mortality (odds ratio 2.2, 95% confidence interval 1.4 to 3.3), with the use of our current patient selection criteria. Double-arterial graft patients had a nonsignificant trend toward increased intermediate-term actuarial survival (P = 0.12) and cardiac event-free survival (P = 0.09). Part II: Comparison of preoperative demographics revealed a higher incidence of diabetes (27% vs 11%, P < 0.001), peripheral vascular disease (16% vs 8%, P = 0.03), and elderly age (13% vs 2%, P = 0.001) in patients receiving an RA versus those receiving a RITA as the second arterial graft. Perioperative outcome analysis revealed a decreased intensive care unit stay in the RA versus RITA group (median 30.4 vs 36.2 hours, respectively, P = 0.005) but no significant difference in hospital length of stay. There was no significant difference in perioperative mortality or cardiac morbidity rates. RITA patients had a higher incidence of sternal wound infection (5.3% vs 0.6%, P = 0.01), however, and tended to have increased blood product transfusion rates (51% vs 40%, P = 0.06).

CONCLUSIONS

The use of 2 arterial grafts is safe, with a reduction in perioperative cardiac morbidity or mortality rates compared with 1 arterial graft after adjustment for other risk variables. When comparing RITA to RA as second arterial grafts, patients receiving an RA have a lower incidence of sternal wound infection and decreased transfusion requirements, with no difference in perioperative or intermediate-term cardiac morbidity or mortality rates.

Phase 2 studies of adenosine cardioplegia

BACKGROUND

Laboratory evidence supports the use of adenosine-supplemented cardioplegia. An initial phase 1 dose-ranging clinical evaluation demonstrated that an adenosine concentration of 15 mumol/L could be safely administered with warm blood cardioplegia and suggested that phase 2 studies were warranted.

METHODS AND RESULTS

Two separate double-blind, randomized, placebo-controlled trials were performed in patients undergoing primary, isolated, nonemergent coronary artery bypass graft surgery. Patients were randomized to receive adenosine 15 mumol/L versus placebo in the first study (n = 200) and adenosine 50 or 100 mumol/L versus placebo in the second study (n = 128). Adenosine was infused with both initial and final doses of warm antegrade blood cardioplegia. The data from the 2 trials were combined using the methods of Mantel and Haenszel, and the results of the meta-analysis are presented as the relative risk with their associated 95% confidence intervals (CI). The different study groups were comparable with respect to all preoperative clinical characteristics, angiographic findings, and intraoperative variables. In both trials 1 and 2, no differences were found between groups in the incidence of the individual primary or secondary outcomes. Similarly, when both studies were combined, there was no significant evidence of any consistent treatment benefit (primary: death: relative risk [RR] = 1.02, 95% CI = 0.06, 16.6; myocardial infarction by CK-MB: RR = 0.84, CI = 0.54, 1.31; low output syndrome: RR = 1.38, CI = 0.29, 6.42; any of the above: RR = 0.98, CI = 0.78, 1.25; secondary: Q-wave myocardial infarction: RR = 1.30, CI = 0.41, 4.13; myocardial infarction by troponin T: RR = 0.7, CI = 0.40, 1.21; inotrope requirement: RR = 0.9, CI = 0.46, 1.79; intra-aortic balloon pump requirement: RR = 0.6, CI = 0.07, 4.81; P > 0.20).

CONCLUSIONS

Despite promising experimental data, adenosine supplementation of warm blood cardioplegia did not demonstrate any statistically significant benefit in patients undergoing elective coronary artery bypass graft surgery. Although sample sizes were relatively small, based on our interim analyses, it is unlikely that increased patient enrollment would reveal any substantive clinical differences between groups.

The role of glycoprotein IIb/IIIa platelet inhibition in percutaneous coronary intervention in the stent era

In autumn 1996, shortly after the platelet glycoprotein (GP) IIb/IIIa inhibitor abciximab was approved for clinical use by the Health Protection Branch of Health Canada, seven interventional cardiologists met in a roundtable forum to review the use of abciximab in percutaneous transluminal coronary angioplasty (PTCA). While a compelling body of data was presented that argued strongly for adjunctive abciximab in conventional balloon angioplasty, the participants found in difficult to extrapolate the findings to contemporary interventional practice dominated by stent implantation. This uncertainty stemmed from the lack of clinical trials of abciximab during the stent era. Concerns were also raised that the unrestricted use of two expensive therapeutic modalities (stent implantation and GP IIb/IIIa inhibition) would place severe strains on catheterization laboratory budgets. The general consensus was that, pending the availability of further data, abciximab should probably be reserved for selected at-risk patients. This article summarized the roundtable discussions to provide cardiologists' perspectives on the use of abciximab in interventional practice. An overview of platelet physiology and the rationale for GP IIb/IIIa receptor inhibition; a summary of the results of recent randomized clinical trials that assessed the efficacy of abciximab in PTCA; an account of how stents became the most prevalent technique used in coronary intervention; a summary of the available data evaluating abciximab in conjunction with stent implantation; and a synopsis of the conference discussions are included.

Vpr stimulates viral expression and induces cell killing in human immunodeficiency virus type 1-infected dividing Jurkat T cells

In this study we investigated the effects of Vpr during human immunodeficiency virus (HIV) infection of proliferating Jurkat T cells by using a vesicular stomatitis virus envelope G glycoprotein pseudotyped HIV superinfection system. We observe that the expression of Vpr results in a severe reduction in the life span of HIV type 1 (HIV-1)-infected dividing T cells in culture. In agreement with a recent report (S. A. Stewart, B. Poon, J. B. M. Jowett, and I. S. Chen, J. Virol. 71:5579-5592, 1997), we show that events characteristic of apoptotic cell death are involved in the Vpr-mediated cytopathic effects. Our results also show that infection with viruses expressing the wild-type vpr gene results in an increase in viral gene expression and production. Interestingly, the effects of Vpr on cell viability and on viral gene expression both correlate with the ability of the protein to induce a cell cycle arrest in the G2/M phase. Mutagenesis analyses show that the C terminus of Vpr is essential for these biological activities. Although the role of Vpr is currently associated with the infection of nondividing cells, our results suggest that Vpr can also directly increase viral replication in vivo in infected dividing T cells. Furthermore, these in vitro observations suggest that Vpr-mediated cytotoxic effects could contribute to the CD4+ depletion associated with AIDS progression.