Recombinant Semliki Forest virus as a vector system for fast and selective in vivo gene delivery into balloon-injured rat aorta

The metamorphosis of vascular stents: passive structures to smart devices

The role of nanotechnology enabled techniques in the evolution of vascular stents.

Development of viral vectors for use in cardiovascular gene therapy

Cardiovascular disease represents the most common cause of mortality in the developed world but, despite two decades of promising pre-clinical research and numerous clinical trials, cardiovascular gene transfer has so far failed to demonstrate convincing benefits in the clinical setting. In this review we discuss the various targets which may be suitable for cardiovascular gene therapy and the viral vectors which have to date shown the most potential for clinical use. We conclude with a summary of the current state of clinical cardiovascular gene therapy and the key trials which are ongoing.

Targeting Sindbis virus-based vectors to Fc receptor-positive cell types

Some viruses display enhanced infection for Fc receptor (FcR)-positive cell types when complexed with virus-specific immunoglobulin (Ig). This process has been termed antibody-dependent enhancement of viral infection (ADE). We reasoned that the mechanism of ADE could be exploited and adapted to target alphavirus-based vectors to FcR-positive cell types. Towards this goal, recombinant Sindbis viruses were constructed that express 1 to 4 immunoglobulin-binding domains of protein L (PpL) as N-terminal extensions of the E2 glycoprotein. PpL is a bacterial protein that binds the variable region of antibody kappa light chains from a range of mammalian species. The recombinant viruses incorporated PpL/E2 fusion proteins into the virion structure and recapitulated the species-specific Ig-binding phenotypes of native PpL. Virions reacted with non-immune serum or purified IgG displayed enhanced binding and ADE for several species-matched FcR-positive murine and human cell lines. ADE required virus expression of a functional PpL Ig-binding domain, and appeared to be FcgammaR-mediated. Specifically, ADE did not occur with FcgammaR-negative cells, did not require active complement proteins, and did not occur on FcgammaR-positive murine cell lines when virions were bound by murine IgG-derived F(ab')2 fragments.

Induction of specific human primary immune responses to a Semliki Forest virus-based tumor vaccine in a Trimera mouse model

Recombinant Semliki Forest virus (rSFV) enables high-level, transient expression of heterologous proteins in vivo, and is believed to be a superior vector for genetic vaccination, compared with the conventional DNA plasmid. Nonetheless, the efficacy of rSFV-based vaccine in eliciting human immune responses has not been tested. We used a Trimera mouse model, consisting of lethally irradiated BALB/c host reconstituted with nonobese diabetes/severe combined immunodeficiency (NOD/SCID) bone marrow plus human peripheral blood mononuclear cells (PBMCs), to characterize the in vivo immune responses against rSFV-encoded human melanoma antigen MAGE-3. MAGE-3-specific antibody and cytotoxic T lymphocyte (CTL) activity were detected by ELISA and 51Cr-release assay, respectively, and the responses were compared with those induced by a plasmid DNA vaccine encoding the same antigen. The results showed that rSFV vaccine could elicit human MAGE-3-specific antibody and CTL response in the Trimera mice, and the antitumor responses were more potent than those by plasmid DNA vaccination. This is the first report to evaluate human immune responses to an rSFV-based tumor vaccine in the Trimera mouse model. Our data suggest that rSFV vector is better than DNA plasmid in inducing protective immunity, and the Trimera model may serve as a general tool to evaluate the efficacy of tumor vaccines in eliciting human primary immune response in vivo.

Endothelium-Targeted Gene and Cell-Based Therapies for Cardiovascular Disease

Most common cardiovascular diseases are accompanied by endothelial dysfunction. Because of its predominant role in the pathogenesis of cardiovascular disease, the vascular endothelium is an attractive therapeutic target. The identification of promoter sequences capable of rendering endothelial-specific transgene expression together with the recent development of vectors with enhanced tropism for endothelium may offer opportunities for the design of new strategies for modulation of endothelial function. Such strategies may be useful in the treatment of chronic diseases such as hypertension, atherosclerosis, and ischemic artery disease, as well as in acute myocardial infarction and during open heart surgery for prevention of ischemia and reperfusion (I/R)-induced injury. The recent identification of putative endothelial progenitor cells in peripheral blood may allow the design of autologous cell-based strategies for neovascularization of ischemic tissues and for the repair of injured blood vessels and bioengineering of vascular prosthesis. "Proof-of-concept" for some of these strategies has been established in animal models of cardiovascular disease. However the successful translation of these novel strategies into clinical application will require further developments in vector and delivery technologies. Further characterization of the processes involved in mobilization, migration, homing, and incorporation of endothelial progenitor cells into the target tissues is necessary, and the optimal conditions for therapeutic application of these cells need to be defined and standardized.

Superior Therapeutic Efficacy of Alphavirus-Mediated Immunization against Human Papilloma Virus Type 16 Antigens in a Murine Tumour Model: Effects of the Route of Immunization

In our efforts to develop a strong, effective immune response against cervical carcinoma and premalignant disease, we study the use of recombinant Semliki Forest virus (SFV) encoding the oncoproteins E6 and E7 from high-risk human papilloma viruses (HPVs). Optimal immunization conditions are required for immunotherapeutic treatment of cervical cancer as it has been postulated that cervical cancer patients are immune-suppressed and/or immunologically tolerant for HPV. We previously generated an optimized construct encoding a fusion protein of HPV16 E6 and E7 and a translational enhancer (enhE6,7). Immunization of mice with SFV-enhE6,7 was shown to induce cytoxic T cell (CTL) responses and resulted in the eradication of established tumours. We now demonstrate, using HPV16-specific MHC class I tetramers, that high pCTL frequencies can be induced. However, this induction is strongly influenced by the route of immunization applied. Whilst in bulk CTL assays, requiring in vitro restimulation, CTL activity can be observed upon sc, ip, iv and im immunization, detectable pCTL frequencies, without in vitro restimulation, are only induced upon im and iv immunization. The route of immunization also strongly influences the dose of viral vector needed to induce CTLs and tumour therapy. As few as 5x104 SFV-enhE6,7, primed and boosted iv, are needed to eradicate tumours in six out of seven mice treated. Furthermore, exponentially growing tumours of approximately 500 mm3 in size were seen to completely resolve and even tumours as large as 1500 mm3 decreased to one-third of their size. Apart from this potency, SFV vectors can safely be used for the expression of oncoproteins such as E6 and E7, since the viral RNA is not integrated in the host genome. Thus SFV-enhE6,7 meets with the criteria that a vaccine against cervical cancer should be safe and induce a very strong, long-lasting CTL response, strong enough to eradicate existing tumours.

Gene Therapy and Endovascular Treatment of Intracranial Aneurysms

Background— Endovascular treatment of intracranial aneurysms is safe and effective but too often is followed by recurrences. Gene therapy may improve healing after embolization, and endovascular approaches may offer future in situ delivery systems designed to prevent aneurysm rupture.

Summary of Review— Advances in coil technology have focused on coating strategies designed to modify the biological reaction to the embolic agent. Gene therapy in cardiovascular applications is limited by low efficiency and transient gene expression. Current advances include the potential use of circulating progenitor cells for ex vivo genetic manipulations followed by in vivo delivery. Direct gene transfer may also be enhanced in situ by coils carrying antibody-tethered adenovirus or through the use of cell-specific or radiation-inducible promoters. Candidate genes that may be of value in promoting healing after endovascular treatment include growth factors and metalloproteinase inhibitors. A better understanding of the biology of aneurysm is necessary to conceive strategies designed to control the development of these lesions before their rupture.

Conclusions— Many technical difficulties remain to be solved, but the combination of gene therapy and endovascular techniques offers multiple therapeutic possibilities in the future control of intracranial aneurysms.

Post-intervention vessel remodeling

By-pass surgery and percutaneous transluminal (coronary) angioplasty, PT(C)A, are standard techniques for the treatment of vascular occlusions. Their usefulness is limited by by-pass graft failure and restenosis occurring after the procedures. Twenty percent of patients treated with PTCA/PTA need a new revascularization procedure within 6 months, despite a successful procedure. Stents are used to prevent restenosis in selected lesions, but in-stent restenosis also remains an important clinical problem. In this review we discuss progress of gene therapy for the treatment of post-PT(C)A restenosis, in-stent restenosis and by-pass graft stenosis over the last 2 years (2000-2002).