Technical considerations of endovascular management of true visceral artery aneurysms

BACKGROUND

True visceral artery aneurysms are potentially complex to treat but with advances in technology and increasing interventional radiology expertise over the past decade are now increasingly the domain of the interventional radiologist. BODY: The interventional approach is based on localization of the aneurysm and identification of the anatomical determinants to treat these lesions to prevent aneurysm rupture. Several different endovascular techniques are available and should be selected carefully, dependent on the aneurysm morphology. Standard endovascular treatment options include stent-graft placement and trans-arterial embolisation. Different strategies are divided into parent artery preservation and parent artery sacrifice techniques. Endovascular device innovations now include multilayer flow-diverting stents, double-layer micromesh stents, double-lumen balloons and microvascular plugs and are also associated with high rates of technical success.

CONCLUSION

Complex techniques such as stent-assisted coiling and balloon-remodeling techniques are useful techniques and require advanced embolisation skills and are further described.

Developing day-case units: imperative for optimal patient care in interventional radiology

As interventional radiology (IR) treatments have evolved, they have become less invasive, enabling rapid recovery, which expedites ambulation and promotes same-day discharge. As a result of this, a significant proportion of IR elective work can be provided using a day-case service model. Reconfiguration of IR services to increase day-case procedures using a dedicated IR day-case unit (RDU) to facilitate the passage of patients is vital to ensure best medical practice. The aim of this review is to discuss the benefits of day-case IR procedures, the optimal structure of an RDU, and to inform radiologists how to introduce and/or improve day-case IR services in their IR practice.

Access to beds for interventional radiology patients: improving patient care

This review describes the rationale in support of admitting rights for interventional radiologists and presents options for the management of interventional radiology (IR) inpatients. The manuscript also discusses wider aspects of IR involvement in inpatient treatment, such as income and funding for IR services, and the implications for IR as a clinical specialty.

Adipose tissue dysfunction in obese horses with equine metabolic syndrome

BACKGROUND

Obesity is a common feature of equine metabolic syndrome (EMS). In other species, obese adipose tissue shows pathological features such as adipocyte hypertrophy, fibrosis, inflammation and impaired insulin signalling all of which contribute to whole body insulin dysregulation. Such adipose tissue dysfunction has not been investigated in horses.

OBJECTIVES

To determine if obese horses with EMS have adipose tissue dysfunction characterised by adipocyte hypertrophy, fibrosis, inflammation and altered insulin signalling.

STUDY DESIGN

Cross-sectional post-mortem study.

METHODS

Samples of peri-renal (visceral) and retroperitoneal adipose tissue were obtained at post-mortem from healthy horses (n = 9) and horses with EMS (n = 6). Samples were analysed to determine average adipocyte size, fibrotic content and expression of inflammatory and insulin signalling genes.

RESULTS

Horses with metabolic syndrome showed marked adipocyte hypertrophy and increased expression of adipokines (leptin) and inflammatory cytokines (TNFα, IL1β and CCL2) in both adipose tissue depots compared to healthy horses. There were no differences in fibrosis or expression of genes relating to insulin signalling between the groups.

MAIN LIMITATIONS

Cases used in this study had advanced EMS and may represent the end stage of the condition; the design of the study is such that we were unable to relate the identified adipose tissue dysfunction to whole body insulin dysregulation.

CONCLUSIONS

Horses with obesity and EMS have significant dysfunction of the peri-renal and retroperitoneal adipose tissue that may contribute to whole body insulin dysregulation.

Secondary interventions after endovascular aneurysm sac sealing: endoleak embolization and limb-related interventions

The Nellix endovascular aneurysm sealing system is a novel alternative to conventional endovascular aneurysm repair for aortic aneurysm management using paired balloon expandable endografts supported by polymer-filled endobags to achieve sealing and anatomic fixation. Part of the promise of endovascular aneurysm sealing is increased resistance to lateral and longitudinal forces and thus a potential for reduced rates of device-related failures, particularly endoleaks. Initial efficacy data on this device are encouraging, but our knowledge of its associated complications and their management is limited. Reported adverse events include Type 1 and 2 endoleaks, graft stenosis and occlusion. The aim of this article is to review the early experience of endovascular aneurysm sealing focusing on the incidence, significance, and management of device-related complications.

Treatment of equine metabolic syndrome: A clinical case series

REASONS FOR PERFORMING STUDY

Treatment of equine metabolic syndrome (EMS) is essential to improve insulin sensitivity and reduce the risk of laminitis. Calorie restriction and increased exercise are the mainstays of treatment but there is potential for poor owner compliance.

OBJECTIVES

To determine whether significant weight loss accompanied by improvements in measures of insulin sensitivity can be achieved in horses and ponies with EMS managed by their owners in their normal environment under veterinary guidance.

STUDY DESIGN

Retrospective clinical case series.

METHODS

Horses and ponies attending 2 university hospitals for investigation and treatment of suspected EMS were eligible for inclusion in the study. Animals underwent a clinical examination, basal and dynamic endocrine testing; those with pituitary pars intermedia dysfunction (PPID) were excluded. Owners were given individually tailored diet and exercise programmes to follow for between 3 and 6 months. After the treatment period, clinical examination and endocrine tests were repeated and results compared to the initial assessment.

RESULTS

Nineteen animals were recruited to the study, 17 with a history of laminitis. All animals showed a reduction in body condition score (P<0.001) and 18/19 had a reduction in bodyweight (P<0.001) between assessments. There were significant (P<0.05) reductions in basal insulin, insulin at 45 min during a combined glucose insulin tolerance test (CGIT), time for blood glucose concentration to return to baseline during a CGIT and mean area under the glucose curve.

CONCLUSIONS

A diet and exercise programme tailored to the needs of the individual animal and implemented by the owner results in weight loss accompanied by improvements in insulin sensitivity.

Abstract MS01-1: Using T cell receptor engineered T cells for the treatment of cancer

Adoptive cellular immunotherapy involves the administration of autologous or allogenic tumor reactive T cells into patients to achieve tumor regression and has been successful in transplant-related malignancies, leukemia, and melanoma. The molecule responsible for the recognition of tumor antigens is the T cell receptor (TCR). Best studied in melanoma, this process involves the identification of lymphocytes with high affinity for tumor antigens that can be selected in vitro and expanded and administered to patients. The administration of naturally occurring T cells has been shown to have an objective response rate ranging from 50-70% in metastatic melanoma patients; including bulky invasive tumors at multiple sites including liver, lung, soft tissue and brain. A major limitation to the widespread application of adoptive cell therapy is the difficulty in generating human T cells with anti-tumor reactivity. To overcome this limitation, we can now insert highly active TCR genes into T cells that can recognize tumor antigens. Genetic engineering of TCR genes into normal T cells is a powerful new strategy to generate large numbers of defined antigen-specific cells for therapeutic application. This approach has evolved beyond experimental stage into a clinical reality. The feasibility of TCR engineered T cells has been shown to be an effective clinical strategy resulting in the regression of established tumors in recent clinical trials. Ultimately it may be possible to establish a collection of defined TCR genes that could be used to treat a diverse set of cancers tailored to each patient depending on the expression pattern of their tumor antigens.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr MS01-1.

Inhibition of TGF-β signaling in genetically engineered tumor antigen-reactive T cells significantly enhances tumor treatment efficacy

Transforming growth factor β (TGF-β) is a cytokine with complex biological functions that may involve tumor promotion or tumor suppression. It has been reported that multiple types of tumors secrete TGF-β, which can inhibit tumor-specific cellular immunity and may represent a major obstacle to the success of tumor immunotherapy. In this study, we sought to enhance tumor immunotherapy using genetically modified antigen-specific T cells by interfering with TGF-β signaling. We constructed three γ-retroviral vectors, one that expressed TGF-β-dominant-negative receptor II (DNRII) or two that secreted soluble TGF-β receptors: soluble TGF-β receptor II (sRII) and the sRII fused with mouse IgG Fc domain (sRIIFc). We demonstrated that T cells genetically modified with these viral vectors were resistant to exogenous TGF-β-induced smad-2 phosphorylation in vitro. The functionality of antigen-specific T cells engineered to resist TGF-β signaling was further evaluated in vivo using the B16 melanoma tumor model. Antigen-specific CD8+ T cells (pmel-1) or CD4+ T cells (tyrosinase-related protein-1) expressing DNRII dramatically improved tumor treatment efficacy. There was no enhancement in the B16 tumor treatment using cells secreting soluble receptors. Our data support the potential application of the blockade of TGF-β signaling in tumor-specific T cells for cancer immunotherapy.

Efficient nonviral Sleeping Beauty transposon-based TCR gene transfer to peripheral blood lymphocytes confers antigen-specific antitumor reactivity

Genetically engineered lymphocytes hold promise for the treatment of genetic disease, viral infections and cancer. However, current methods for genetic transduction of peripheral blood lymphocytes rely on viral vectors, which are hindered by production and safety-related problems. In this study, we demonstrated an efficient novel nonviral platform for gene transfer to lymphocytes. The Sleeping Beauty transposon-mediated approach allowed for long-term stable expression of transgenes at approximately 50% efficiency. Utilizing transposon constructs expressing tumor antigen-specific T-cell receptor genes targeting p53 and MART-1, we demonstrated sustained expression and functional reactivity of transposon-engineered lymphocytes on encountering target antigen presented on tumor cells. We found that transposon- and retroviral-modified lymphocytes had comparable transgene expression and phenotypic function. These results demonstrate the promise of nonviral ex vivo genetic modification of autologous lymphocytes for the treatment of cancer and immunologic disease.

Actinomyces species as a cause of abscesses in nine horses

The characteristics, history, clinical signs, treatment and outcome of nine horses with abscesses caused by Actinomyces species were reviewed. dna sequencing was used to determine the species of one of the isolates. The horses were one to 11 years of age, and the abscesses were most commonly located in the submandibular and retropharyngeal regions. The bacterium was usually cultured as the sole isolate and the horses were most often affected in the autumn. Most of the abscesses were treated with antimicrobials and drainage, but some of them recurred. The horses with submandibular abscesses had residual scar tissue that in some cases did not resolve.

How safe is bilateral internal iliac artery embolization prior to EVAR?

PURPOSE

To assess the outcomes of patients after bilateral internal iliac artery (IIA) embolization prior to endovascular aneurysm repair (EVAR).

METHODS

Thirty-nine patients (age range 55-88 years, mean 72.5 years; 2 women) underwent IIA embolization/occlusion before EVAR. There were 28 patients with aorto-biiliac aneurysms and 6 with bilateral common iliac artery (CIA) aneurysms. Five patients with unilateral CIA aneurysms had previous surgical ligation of the contralateral IIA or inadvertent covering by the stent-graft of the contralateral IIA origin. Outcomes were assessed by clinical follow-up.

RESULTS

Severe ischemic complications were limited to spinal cord ischemia in 1 patient (3%) who developed paraparesis following EVAR. No other severe ischemic complications such as buttock necrosis, or bowel or bladder ischemia, occurred. Buttock and/or thigh claudication occurred in 12 patients (31%) and persisted beyond 1 year in 3 patients (9%). Sexual dysfunction occurred in 2 patients (5%). Patients who underwent simultaneous embolization had a 25% (3/12) ischemic complication rate versus 41% (11/27) in those with sequential embolization (p = 0.48). Embolization limited to the main trunk of the IIA resulted in a significantly reduced ischemic complication rate of 16% (3/19) versus 55% (11/20) of patients who had a more distal embolization of the IIA (p = 0.019, Fisher's exact test).

CONCLUSION

Severe complications after bilateral IIA embolization are uncommon. Although buttock/thigh claudication occurs in around 30% of patients soon after the procedure, this resolves in the majority after 1 year. There is no obvious benefit for sequential versus simultaneous IIA embolization in our series. Occlusion of the proximal IIA trunk is associated with reduced complications compared with occlusion of the distal IIA.

Strategies for the Management of SVC Stent Migration into the Right Atrium

PURPOSE

Stent migration into the right atrium is a potentially fatal complication of stenting in the venous system and is most likely to occur during the treatment of superior vena cava obstruction. Endovascular approaches that can salvage this hazardous situation are described and the keys to successful treatment are highlighted.

MATERIALS AND METHODS

Four different strategies are reviewed: (1) snaring the stent directly, (2) angioplasty balloon-assisted snaring of the stent, (3) guide wire-assisted snaring of the stent, and (4) superior vena cava-to-inferior vena cava bridging stent.

RESULTS

These techniques have been employed in the successful management of four cases. No short- or long-term complications as a result of these maneuvers have been identified. Additional treatment of the underlying disease was possible at the same time in each case.

CONCLUSION

We conclude that prompt management of right atrial stent migration is essential and can be successfully achieved by a variety of "bale-out" techniques which are within the technical range of most interventional radiologists.

Endovascular embolization of visceral artery aneurysms with ethylene-vinyl alcohol (Onyx): a case series

We report the application of the liquid embolic agent ethylene-vinyl alcohol (Onyx; MicroTherapeutics, Irvine, CA, USA) in the management of visceral artery aneurysms. The technique and indications for using Onyx are discussed with emphasis on the management of wide-necked aneurysms and maintenance of patency of the parent vessel. None of the cases was considered suitable for stent-grafting or embolization with conventional agents. Two aneurysms of the renal artery bifurcation and one aneurysm of the inferior pancreaticoduodenal artery were treated. Following treatment there was complete exclusion of all aneurysms. There was no evidence of end-organ infarction. Follow-up with intervals up to 6 months has shown sustained aneurysm exclusion. Onyx is known to be effective in the management of intracranial aneurysms. Our experience demonstrates the efficacy and applicability of the use of Onyx in the treatment of complex visceral artery aneurysms.

Autologous thrombin-induced thrombosis of pseudoaneurysms

Background

This study was designed to evaluate the use of autologous thrombin (as opposed to commercial bovine thrombin) in the percutaneous obliteration of postcatheterization femoral pseudoaneurysms.

Methods

Ten consecutive patients with a symptomatic femoral pseudoaneurysm following cardiac catheterization underwent duplex assessment. All ten pseudoaneurysms were at least 2 cm in the longest axis. Autologous thrombin was isolated from 60 ml blood, under sterile conditions. The autologous thrombin was injected into the cavity of the pseudoaneurysm under ultrasonographic guidance. The progression of thrombosis was monitored throughout with ultrasonography. After the procedure, the femoral arteries were examined for thrombosis propagation or embolization. The foot pulses and ankle pressures were checked. Samples of the thrombin isolates were analysed to quantify thrombin activity. Duplex assessment was repeated at 6 weeks.

Results

All ten patients had successful thrombosis of the pseudoaneurysm, although three required repeat thrombin injections within 24 h. No long-term symptoms were identified relating to the thrombosis and no patient required surgery. There was no evidence of recanalization at 6 weeks on duplex imaging, and no signs of infection.

Conclusion

Autologous thrombin-induced thrombosis of pseudoaneurysms is a simple, safe, painless and inexpensive procedure. This novel approach, which uses the patient's own thrombin, is cheaper than bovine thrombin; it also avoids the risk of viral contamination or anaphylaxis from commercial thrombin.

Inhibition of HIV-1 replication by novel lentiviral vectors expressing transdominant Rev and HIV-1 env antisense

Retroviral vectors expressing transdominant negative mutants of Rev (TdRev) inhibit HIV-1 replication by preventing the nuclear export of unspliced viral transcripts, thus inhibiting the synthesis of Gag-Pol, Env and reducing the levels of genomic RNA available for packaging. Due to these effective mechanisms of inhibition, production of HIV-1-based lentiviral vectors expressing TdRev has been difficult. Here we describe HIV-based vectors in which expression of TdRev is negatively regulated by Rev expression. In these vectors, we maintained the wild-type HIV-1 Tat/Rev exons and intron configuration and its mode of splicing regulation. The second Rev exon was mutated to encode TdRev. Inhibition of TdRev expression by Rev during vector production yields high titer vector preparations. A second vector containing an additional anti-HIV gene (env-antisense) was constructed by flipping a 1.2-kb env fragment contained within the Tat/TdRev intron. SupT1 cells and primary CD4+ lymphocytes transduced with these vectors inhibit HIV-1 replication and show a preferential advantage for survival. Although these vectors are poorly mobilized to secondary target cells by wild-type HIV-1, they reduce the infectivity of the wild-type virions escaping inhibition.

Development of an avian leukosis-sarcoma virus subgroup A pseudotyped lentiviral vector

We are using avian leukosis-sarcoma virus (ALSV) vectors to generate mouse tumor models in transgenic mice expressing TVA, the receptor for subgroup A ALSV. Like other classical retroviruses, ALSV requires cell division to establish a provirus after infection of host cells. In contrast, lentiviral vectors are capable of integrating their viral DNA into the genomes of nondividing cells. With the intention of initiating tumorigenesis in resting, TVA-positive cells, we have developed a system for the preparation of a human immunodeficiency virus type 1 (HIV-1)-based lentiviral vector, pseudotyped with the envelope protein of ALSV subgroup A (EnvA). The HIV(ALSV-A) vector retains the requirement for TVA on the surface of target cells and can be produced at titers of 5 x 10(3) infectious units (IU)/ml. By inserting the central polypurine tract (cPPT) from the HIV-1 pol gene and removing the cytoplasmic tail of EnvA, the pseudotype can be produced at titers approaching 10(5) IU/ml and can be concentrated by ultracentrifugation to titers of 10(7) IU/ml. HIV(ALSV-A) also infects embryonic fibroblasts derived from transgenic mice in which TVA expression is driven by the beta-actin promoter. In addition, this lentivirus pseudotype efficiently infects these fibroblasts after cell cycle arrest, when they are resistant to infection by ALSV vectors. This system may be useful for introducing genes into somatic cells in adult TVA transgenic animals and allows evaluation of the effects of altered gene expression in differentiated cell types in vivo.

Distal venous arterialization for lower limb salvage: angiographic appearances and interventional procedures

Approximately 14%-20% of patients with critical lower limb ischemia are unsuited for distal arterial reconstruction and face major distal amputation. Distal venous arterialization is a unique procedure in which the venous bed is used as an alternative conduit for perfusion of peripheral tissues. Eighteen patients with stage IV Fontaine critical lower limb ischemia underwent venous arterialization. Preoperative angiographic findings confirmed the absence of any below-knee continuous arterial vessels. The most distal satisfactory artery was used for proximal bypass anastomosis, and venous valves were destroyed with Parsonnet probes, cutting balloons, Fogarty catheters, and valvulotomes under radiologic guidance. All patients underwent intra- and postoperative angiography of the venous grafts and the distal venous bed. Primary and secondary graft patencies were 66% and 72%, respectively, at a mean follow-up of 25 months. The limb salvage rate was 83% overall and 75% at 2-year follow-up. Vascular imaging is essential in selecting and following up patients and in determining the appropriate intraoperative procedure.

Malignant biliary disease: percutaneous interventions

Interventional radiologists have an important role in the management of patients with malignant biliary obstruction. This article describes the techniques for percutaneous biliary drainage, insertion of biliary endoprostheses, and the management of occluded biliary endoprostheses. Most procedures are performed by using fluoroscopic guidance alone. Ultrasound is also a useful modality for guiding biliary drainage, particularly drainage of the left biliary ducts. Patients should be treated by internal drainage if possible. Metallic endoprostheses can be inserted at the time of the initial biliary drainage procedure. Plastic tubes should be inserted a few days after biliary drainage because of their relatively large size compared with metallic stents. Occluded plastic stents should be replaced. Blocked metallic stents should be treated either by placement of additional overlapping metallic stents or by placement of plastic stents within the metallic stent lumen.

Specific inhibition of gene expression by small double-stranded RNAs in invertebrate and vertebrate systems

Short interfering RNAs (siRNAs) are double-stranded RNAs of approximately 21-25 nucleotides that have been shown to function as key intermediaries in triggering sequence-specific RNA degradation during posttranscriptional gene silencing in plants and RNA interference in invertebrates. siRNAs have a characteristic structure, with 5'-phosphate/3'-hydroxyl ends and a 2-base 3' overhang on each strand of the duplex. In this study, we present data that synthetic siRNAs can induce gene-specific inhibition of expression in Caenorhabditis elegans and in cell lines from humans and mice. In each case, the interference by siRNAs was superior to the inhibition of gene expression mediated by single-stranded antisense oligonucleotides. The siRNAs seem to avoid the well documented nonspecific effects triggered by longer double-stranded RNAs in mammalian cells. These observations may open a path toward the use of siRNAs as a reverse genetic and therapeutic tool in mammalian cells.

Percutaneous treatment of pseudoaneurysms using fibrin adhesive

This study was performed to assess the safety and efficacy of treatment of iatrogenic pseudoaneurysms with fibrin adhesive. 28 patients with iatrogenic pseudoaneurysms were treated. The first 20 patients had either at least one previously unsuccessful treatment of ultrasound guided compression repair (UGCR), a contraindication to UGCR or could not tolerate the procedure. Diagnosis was confirmed on ultrasound and angiography and a balloon inflated across the neck of the pseudoaneurysm. Fibrin adhesive was injected under ultrasound control directly into the pseudoaneurysm sac. The balloon was deflated after 15 min and check ultrasound and angiography performed, with a further ultrasound at 24 h. The subsequent eight patients underwent embolisation as the first line treatment without use of a protective balloon. 16 of the first 20 patients (80%) and all of the subsequent 8 patients had successful embolisation of the pseudoaneurysm after a single treatment. Two pseudoaneurysms failed to thrombose despite two treatments in one case and three treatments in the other, and both required surgery. The only significant complication was the development of local cellulitis in one patient. In conclusion, embolisation of iatrogenic aneurysms with fibrin adhesive is a safe and effective treatment. It should be considered as an alternative to surgery and UGCR.

Inhibition of human immunodeficiency virus type 1 (HIV-1) replication by HIV-1-based lentivirus vectors expressing transdominant Rev

Retrovirus vectors expressing transdominant-negative mutants of Rev (TdRev) inhibit human immunodeficiency virus type 1 (HIV-1) replication by preventing the nuclear export of unspliced viral transcripts, thus inhibiting the synthesis of Gag-Pol, Env, and genomic RNA. The use of HIV-1-based vectors to express TdRev would have the advantage of allowing access to nondividing hematopoietic cells. It would also provide additional levels of protection by sequestering the viral regulatory proteins Tat and Rev, competing for encapsidation into wild-type virions, and inhibiting reverse transcription. Here we describe HIV-1-based vectors that express TdRev. These vectors contain mutations in the splicing signals or replacement of the Rev-responsive element by the simian retrovirus type 1 constitutive transport element, making them less sensitive to the inhibitory effects of TdRev. In addition, overexpression of Rev and the use of an HIV-1 helper plasmid that drives high levels of Gag-Pol synthesis were used to transiently overcome the inhibition by TdRev of the synthesis of Gag-Pol during vector production. SupT1 cells transduced with these vectors were more resistant to HIV-1 replication than cells transduced with Moloney murine leukemia virus-based vectors expressing TdRev. Furthermore, we show that these vectors can be mobilized by the wild-type virus, reducing the infectivity of virions escaping inhibition and conferring protection against HIV-1 replication to previously untransduced cells.

Potent inhibition of human immunodeficiency virus type 1 replication by conditionally replicating human immunodeficiency virus-based lentiviral vectors expressing envelope antisense mRNA

We describe an HIV-based lentiviral vector that expresses a 1-kb antisense mRNA directed against the HIV-1 mRNAs containing env sequences. The expression of antisense env mRNAs (envAS) does not inhibit the synthesis of p24 expressed from the HIV-1 helper plasmid used to package the vector, as this helper has a deletion in the env gene. This allows the production of high-titer VSV-G pseudotyped lentiviral particles. In challenge experiments using unselected populations of SupT1 cells transduced with this vector, a complete inhibition of HIV-1 replication was observed for long periods of in vitro culture, even at high HIV-1 infectious doses. The potent inhibition of HIV-1 replication by this vector correlated with a low occurrence of mobilization of the vector to previously untransduced cells. The infectivity of the wild-type HIV-1 that escapes inhibition was highly inhibited, suggesting that the vector is providing HIV-1 inhibition of replication not only due to its antisense effect but also by competing for encapsidation and mobilization to noninfected cells.

Efficient gene transfer to human peripheral blood monocyte-derived dendritic cells using human immunodeficiency virus type 1-based lentiviral vectors

Dendritic cells (DCs) are potent antigen-presenting cells and are capable of activating naive T cells. Gene transfer of tumor antigen and cytokine genes into DCs could be an important strategy for immunotherapeutic applications. Dendritic cells derived from peripheral blood monocytes do not divide and are therefore poor candidates for gene transfer by Moloney murine leukemia virus (Mo-MuLV)-based retroviral vectors. Lentiviral vectors are emerging as a powerful tool for gene delivery into dividing and nondividing cells. A three-plasmid expression system pseudotyped with the envelope from vesicular stomatitis virus (VSV-G) was used to generate lentiviral vector particles expressing enhanced green fluorescent protein (EGFP). Peripheral blood monocyte-derived DCs were cultured in the presence of GM-CSF and IL-4 and transduced with lentiviral or Mo-MuLV-based vectors expressing EGFP. FACS analysis of lentiviral vector-transduced DCs derived either from normal healthy volunteers or from melanoma patients demonstrated transduction efficiency ranging from 70 to 90% compared with 2-8% using Mo-MuLV-based vectors pseudotyped with VSV-G. Comparison of lentiviral vectors expressing EGFP driven by CMV or human PGK promoters showed similar levels of transgene expression. Lentiviral vector preparations produced in the absence of HIV accessory proteins transduced DCs at efficiencies equal to vectors produced with accessory proteins. Alu-HIV-1 LTR PCR demonstrated the genomic integration of the lentiviral vector in the transduced DCs. Transduced cells showed characteristic dendritic cell phenotype and strong allostimulatory capacity and maintained the ability to respond to activation signals such as CD40 ligand and lipopolysaccharide. These results provide evidence that lentiviral vectors are efficient tools for gene transfer and expression in monocyte-derived DCs that could be useful for immunotherapeutic applications.

Lentiviral-mediated gene transfer into human lymphocytes: role of HIV-1 accessory proteins

Resting lymphocytes are refractory to gene transfer using Moloney murine leukemia virus (MMLV)-based retroviral vectors because of their quiescent status. Recently, it has been shown that lentiviral vectors are capable of transferring genes into nondividing and terminally differentiated cells. We used human immunodeficiency virus type-1 (HIV-1)-based vectors expressing enhanced green fluorescent protein (EGFP) driven by different promoters (CMV, MPSV, or PGK) and investigated their ability to transduce human T- and B-cell lines, as well as resting or activated primary peripheral and umbilical cord blood lymphocytes. The effects of the presence or the absence of HIV-1 accessory proteins (Vif, Vpr, Vpu, and Nef) in the vector system were also assessed. Flow cytometry analysis showed no differences in the ability of these vectors of transferring the reporter gene into lymphocytic lines and mitogen-stimulated primary lymphocytes in the presence or the absence of HIV-1 accessory proteins (APs). Similarly, viral supernatants generated in the presence of accessory genes could efficiently transduce various subsets of resting lymphocytes and provide long-term expression of the transgene. No significant transduction-induced changes in cell activation or cycling status were observed and Alu-HIV-1 long terminal repeat polymerase chain reaction (LTR PCR) analysis demonstrated integration of the vector sequences at the molecular level. In contrast, in the absence of HIV-1 APs, lentiviral vectors failed to integrate and express the transgene in resting lymphocytes. These results show that transduction of primary resting lymphocytes with HIV-1-based vectors requires the presence of viral accessory proteins. (Blood. 2000;96:1309-1316)

Improved titers of HIV-based lentiviral vectors using the SRV-1 constitutive transport element

The development of lentiviral vectors that use Rev-independent mechanisms of nuclear export for their genomic RNA could facilitate the construction of novel anti-HIV vectors. We have improved the titers of Rev-independent lentiviral vectors having the SRV-1 CTE by mutating the major splice donor and acceptor sites present in the vector and by relocalization of the CTE sequences adjacent to the HIV-1 3'LTR. These two modifications have additive beneficial effects on vector titers and packaging efficiency. Packaging these CTE+ vectors expressing marker genes with a Rev-dependent HIV-1 helper vector yields higher titers than are obtained using a Rev-dependent lentiviral vector.

dsRNA-mediated gene silencing in cultured Drosophila cells: a tissue culture model for the analysis of RNA interference

RNA interference (RNAi) is a form of post-transcriptional gene silencing that has been described in a number of plant, nematode, protozoan, and invertebrate species. RNAi is characterized by a number of features: induction by double stranded RNA (dsRNA), a high degree of specificity, remarkable potency and spread across cell boundaries, and a sustained down-regulation of the target gene. Previous studies of RNAi have examined this effect in whole organisms or in extracts thereof; we have now examined the induction of RNAi in tissue culture. A screen of mammalian cells from three different species showed no evidence for the specific down-regulation of gene expression by dsRNA. By contrast, RNAi was observed in Drosophila Schneider 2 (S2) cells. Green fluorescent protein (GFP) expression in S2 cells was inhibited in a dose-dependent manner by transfection of dsRNA corresponding to gfp when GFP was expressed either transiently or stably. This effect was structure- and sequence-specific in that: (1) little or no effect was seen when antisense (or sense) RNA was transfected; (2) an unrelated dsRNA did not reduce GFP expression; and (3) dsRNA corresponding to gfp had no effect on the expression of an unrelated target transgene. This invertebrate tissue culture model should allow facile assays for loss of function in a well-defined cellular system and facilitate further understanding of the mechanism of RNAi and the genes involved in this process.

Modified human immunodeficiency virus-based lentiviral vectors display decreased sensitivity to trans-dominant Rev

As a first step toward the development of HIV-based conditionally replicating defective interfering particles expressing trans-dominant Rev (TdRev), we studied whether mutation of the splicing signals and replacement of the RRE by the SRV-1 CTE would render these vectors less sensitive to TdRev. Vectors with mutations in the splicing signals (SD-/RRE+) yielded high titers (5 X 10(6) CFU/ml) and showed higher levels of cytoplasmic unspliced mRNA than the corresponding SD+/RRE+ vectors either in the absence of Rev, in the presence of TdRev, or in the presence of both TdRev and Rev. Proviral copies of SD-/RRE+ vectors were rescued more efficiently than SD+/RRE+ vectors when TdRev was expressed. Vectors with the SRV-1 CTE (SD+/CTE+ and SD-/CTE+) expressed high levels of cytoplasmic unspliced mRNA in the absence of Rev expression. Titers obtained with the SD-/CTE+ vectors (10(6) CFU/ml) were higher than the titers obtained with SD+/CTE+ vectors. We also tested the effect of other structural modifications such as the orientation of the expression cassette and the presence of the central polypurine tract (cPPT/CTS). We show that an expression cassette cloned in the reverse orientation with respect to the LTRs or elimination of the cPPT/CTS element severely affected vector titers. We also demonstrated that these vectors can be efficiently mobilized from their proviral state by HIV trans-complementing functions, and transduced into secondary target cells without suffering any genomic rearrangement.

Evaluation of recombinant alphaviruses as vectors in gene therapy

Alphavirus vectors based on Sindbis virus and Semliki Forest virus (SFV) were characterized as potential gene transfer vectors. Initial studies were performed using vectors engineered to transfer either lacZ or green fluorescent protein (GFP). High levels of gene transfer were achieved in human primary fibroblasts, BHK and 293T cells, with low levels of transduction observed in more than 20 other target cells. Alphavirus-based expression was generally very high, but transient in every cell type. Replication-competent alphavirus was never detected in SFV preparations but could be produced by Sindbis-based vectors at a frequency of up to 3 x 10(-3) infectious units per ml. We constructed a human clotting factor IX (hFIX) cDNA-containing Sindbis virus and compared it with hFIX cDNA-harboring adenoviral and retroviral vectors. In most cases, hFIX levels obtained with Sindbis vector were initially at least an order of magnitude higher than those obtained with other viral vectors. These data demonstrate that alphavirus vectors compare favorably with adenovirus vectors as systems to promote high-level transient gene expression and should be considered as an alternative vector for gene transfer and potential gene therapy studies.

Adenovirus-mediated expression of human coagulation factor IX in the rhesus macaque is associated with dose-limiting toxicity

We used a first-generation adenovirus vector (AVC3FIX5) to assess whether human factor IX could be expressed and detected in the rhesus macaque, which we have shown does not make high-titer antibodies to human factor IX protein. Three animals received 1 x 10(10) to 1 x 10(11) plaque-forming units per kilogram by intravenous injection. Human factor IX was present within 24 hours of vector administration and peaked 4 days later at 4,000 ng/mL in the high-dose recipient, and lower levels were seen in the intermediate-dose recipient. No human factor IX was detected in the low-dose recipient's plasma. Serum cytokine analysis and early hypoferremia suggested a dose-dependent acute-phase response to the vector. Human factor IX was detectable in rhesus plasma for 2 to 3 weeks for the high- and intermediate-dose recipients, but disappeared concomitant with high-titer antihuman factor IX antibody development. There was substantial, dose-dependent, dose-limiting liver toxicity that was manifest as elevated serum transaminase levels, hyperbilirubinemia, hypoalbuminemia, and prolongation of clotting times. Of particular interest was prolongation of the thrombin clotting time, an indicator of decreased fibrinogen or fibrinogen dysfunction. All evidence of liver toxicity resolved except for persistent hypofibrinogenemia in the high-dose recipient, indicating possible permanent liver damage. Our data suggest a narrow therapeutic window for first-generation adenovirus-mediated gene transfer. The development of antihuman factor IX antibodies and abnormalities of fibrinogen in the rhesus macaque is of concern for application of adenovirus (or other viral) vectors to hemophilia gene therapy.

Genetic strategies to inhibit HIV

The worldwide incidence of HIV infection continues to rise despite more than a decade of intense research aimed at developing effective intervention strategies. Because the mechanisms of action of the essential HIV gene products are now known, these have become potential targets for intervention. Some of these targets are attractive candidates for intervention by gene therapy. This review will focus on the recent progress in gene therapy strategies, including approaches approved for clinical trials. The efficacy of these various anti-HIV strategies, as well as the advantages and drawbacks of the different existing gene delivery systems, will be discussed.

Management of ureteral strictures in renal transplants by antegrade balloon dilatation and temporary internal stenting

PURPOSE

To evaluate the efficacy of percutaneous balloon dilatation and temporary internal stenting in the treatment of transplant ureteral strictures.

METHODS

Nine patients presenting with obstructed renal transplants were treated by antegrade nephrostomy insertion, ureteroplasty, and temporary internal stenting. Following stent removal, patients were divided into two groups for analysis according to whether the obstruction occurred less than (group A) or more than (group B) 3 months following transplantation.

RESULTS

All procedures were technically successful. In group A (n = 6), all patients were successfully treated by one or two dilatations with stenting. In group B (n = 3), two patients were successfully treated by one dilatation with stenting. Overall, eight patients (89%) have had their primary or secondary stent removed successfully at a mean interval of 97.5 days after insertion, and remain well at a mean follow-up interval of 22 months.

CONCLUSION

Balloon dilatation and temporary internal stenting is a useful method for treating transplant ureteral strictures.

Gene therapy clinical trials for HIV

Despite advances in drug treatment for human immunodeficiency virus (HIV), new therapeutics are needed for sustained treatment of this infection. Gene therapy has great potential for HIV due to its specificity for viral targets and prolonged expression of therapeutics. In this review, the various approaches that current gene therapy clinical trials are using to treat HIV disease are described. Results reported from these trials indicate that the approaches tested appear to be safe and confer some benefit to the genetically-modified cell. However, technical improvements must be made in order for gene therapy to realize its true potential.

Production of minigene-containing retroviral vectors using an alphavirus/retrovirus hybrid vector system

In an attempt to increase the synthesis of human clotting factors VIII and IX in transduced cells, optimized expression cassettes containing genomic genelike elements (minigenes) were assembled. Plasmid DNA containing factor VIII or factor IX minigenes and driven by three human cellular promoters (albumin, factor IX, PGK) or the strong viral promoter RSV-LTR were electroporated into TE671 and HepG2 cell lines, and clotting factor levels were determined by ELISA. In comparison with a parallel transfection of MLV-LTR-promoted retroviral vector plasmid DNAs, the PGK- and RSV-LTR-promoted minigene constructs produced equal or greater amounts of clotting factor proteins. A factor IX minigene cassette was cloned into the retrovirus-based gene transfer vector LN (in both forward and reverse orientations) and the minigene vector was introduced into the Phoenix retroviral packaging cell line. Analysis of neo(r) cells demonstrated that insertion of a factor IX minigene into the retroviral vector LN resulted in rearrangement of the factor IX sequence and loss of factor IX expression in the Phoenix packaging cell line. The same factor IX minigene was then inserted into an alphavirus/retrovirus hybrid vector that facilitates the synthesis of retroviral vector RNA in the cytoplasm of cells. Alphavirus/retrovirus virions were produced and used to transduce the Phoenix retroviral vector packaging cell line. The cytoplasmically produced factor IX minigene-containing retroviral vectors were collected and used to transduce TE671 cells. Analysis of transduced cells demonstrated stable transfer of the minigene and expression of factor IX.

The rhesus macaque as an animal model for hemophilia B gene therapy

We have determined the 2905 nucleotide sequence of the rhesus macaque factor IX complementary DNA (cDNA) and found it to be greater than 95% identical to that of the human factor IX cDNA. The cDNA has a large 3' untranslated region like the human cDNA, but unlike the human cDNA has two polyadenylation sites 224 nucleotides apart that are used for transcription of the messenger RNA. The deduced amino acid sequence is greater than 97% identical to that of human factor IX, differing in only 11 of 461 amino acids in the complete precursor protein. We found a single silent polymorphism in the nucleotide sequence at the third position of the codon for asparagine at position 167 in the secreted protein (AAC/AAT). All residues subject to posttranslational modifications in the human protein are also found in the rhesus factor IX sequence. The high degree of homology between the rhesus and human factor IX proteins suggested the possibility that the human factor IX protein might be nonimmunogenic in the rhesus. We tested the immunogenicity of human factor IX in three rhesus macaques by repeated intravenous injections of monoclonal antibody-purified, plasma-derived human factor IX over the course of more than a year and assessed the recovery and half-life of the infused protein, as well as in vitro indicators of antihuman factor IX antibodies. Human factor IX recovery and half-life remained unchanged over the course of a year in the three animals studied, and aPTT mixing studies showed no evidence for neutralizing antihuman factor IX antibodies. An outbred, nonhuman primate model that permits assessment of the level and duration of factor IX expression as well as vector safety would complement the use of other (mouse and canine) hemophilia B animal models in current use for the development of gene therapy for hemophilia B.

Inhibition of human immunodeficiency virus type 1 by Tat/Rev-regulated expression of cytosine deaminase, interferon alpha2, or diphtheria toxin compared with inhibition by transdominant Rev

A retroviral vector was designed to express toxic proteins only in the presence of the HIV-1 Rev and/or Tat protein(s). The design of this vector incorporates an HIV-specific expression cassette that consists of three elements: the U3R region of the HIV-1 IIIB LTR provides the promoter and Tat-responsive element, a modified intron derived from the human c-src gene facilitates the splicing of inserted genes, and the HIV-1 RRE region enhances the transport of unspliced mRNAs. To further limit potential readthrough transcription, the expression cassette was inserted in the reverse transcriptional orientation relative to the retroviral vector LTR. Three different genes, interferon alpha2, diphtheria toxin (DT-A), and cytosine deaminase, were inserted into this vector. Tat and Rev inducibility was demonstrated directly by a >300-fold induction of interferon production and functionally by a decrease in colony-forming units when a Tat and Rev expression vector was titered on HeLa cells harboring the inducible DT-A cassette. The Tat-inducible cytosine deaminase gene was tested in the Sup-T1 T cell line and shown to inhibit HIV-1 production only when engineered cells were grown in the presence of 5-fluorocytosine. To test the ability of this system to inhibit HIV-1 infection in bulk PBL cultures, a series of transduction and challenge experiments was initiated with both the interferon and DT-A vectors. Protection against infection was documented against three HIV strains in PBLs. Last, the interferon and DT-A vectors were compared with a vector encoding a transdominant Rev protein and were shown to mediate equal or greater inhibition of HIV-1.

Transplantation of transduced nonhuman primate CD34+ cells using a gibbon ape leukemia virus vector: restricted expression of the gibbon ape leukemia virus receptor to a subset of CD34+ cells

The transduction efficiencies of immunoselected rhesus macaque (Macaca mulatta) CD34+ cells and colony-forming progenitor cells based on polymerase chain reaction (PCR) analysis were comparable for an amphotropic Moloney murine leukemia virus (MLV) retroviral vector and a retroviral vector derived from the gibbon ape leukemia virus (GaLV) packaging cell line, PG13. On performing autologous transplantation studies using immunoselected CD34+ cells transduced with the GaLV envelope (env) retroviral vector, less than 1% of peripheral blood (PB) contained provirus. This was true whether bone marrow (BM) or cytokine-mobilized PB immunoselected CD34+ cells were reinfused. This level of marking was evident in two animals whose platelet counts never fell below 50,000/microliter and whose leukocyte counts had recovered by days 8 and 10 after having received 1.7 x 10(7) or greater of cytokine-mobilized CD34+ PB cells/kg. Reverse transcriptase(RT)-PCR analysis of CD34+ subsets for both the GaLV and amphotropic receptor were performed. The expression of the GaLV receptor was determined to be restricted to CD34+ Thy-1+ cells, and both CD34+ CD38+ and CD34+ CD38dim cells, while the amphotropic receptor was present on all CD34+ cell subsets examined. Our findings suggest that, in rhesus macaques, PG13-derived retroviral vectors may only be able to transduce a subset of CD34+ cells as only CD34+ Thy-1+ cells express the GaLV receptor.

Characterization of diverse viral vector preparations, using a simple and rapid whole-virion dot-blot method

A number of different viruses have been adapted as gene transfer vectors, including retroviruses, adenoviruses, adenoassociated viruses (AAVs), herpes simplex virus, SV40 viruses, and alphaviruses (both Semliki Forest and Sindbis viruses). One of the major rate-limiting and time-consuming steps in the characterization of these vectors is the process of determining the viral vector titers. In addition, there is no "universal" method that can be used to rapidly estimate the titer and the utility of viral vector preparations. We demonstrate here that supernatant from diverse classes of viral vectors, with either RNA or DNA genomes, can be rapidly evaluated by a simple virus dot-blot hybridization without prior extraction of nucleic acids. This system can provide a reliable screen for physical titer of viral vector supernatants in 1 day.

Ex vivo fibroblast transduction in rabbits results in long-term (>600 days) factor IX expression in a small percentage of animals

Delivery of human factor IX to the circulation was analyzed in rabbits by ex vivo fibroblast transduction followed by subcutaneous implantation. Kinetic studies of human factor IX in rabbits demonstrated a half-life of approximately 16 hr and a volume distribution of 22%, where intraperitoneal and subcutaneous bioavailability was three- to sevenfold lower than by intravenous administration. Ex vivo retroviral transduction of autologous fibroblasts was performed on 15 animals. After subcutaneous injection of fibroblast-collagen mixtures, the expression of human factor IX in rabbit plasma was followed by ELISA. Of 15 rabbits injected, expression of human factor IX was detected in 2 animals, and expression was long term (>600 days). One animal had stable levels of human factor IX, at 20 ng/ml, while the second animal had lower and gradually decreasing levels of human factor IX. There were no gross differences in pathology at the injection sites, when comparing animals with human factor IX in plasma and those without. Immunological studies demonstrated antibody formation in response to injection mixture components (including human factor IX), but again there was no correlation with immune response and long-term factor IX production in animals. Tissues at the implantation sites were positive for factor IX DNA by PCR analysis, regardless of whether there was detectable plasma factor IX or not. Small numbers of PCR-positive cells were detected in the internal organs of the long term-expressing rabbits while similar tissues were negative in nonexpressing animals.