Current Gene Therapy - Volume 1, Issue 3, 2001

Gene therapy is a promising endeavor for the treatment of disease in the 21st century. The key to capitalize on this venture lies in the availability of efficient gene transfer and expression tools. Viral vectors are useful vehicles for the delivery of foreign genes into target cells, and retroviral vectors have been popular because of their ability to integrate into the host cell genome and maintain persistent gene expression. Recent studies of the human immunodeficiency virus (HIV) have demonstrated that lentiviruses, members of the retroviral family, have the ability to infect cells at both mitotic and post-mitotic stages of the cell cycle. This article aims to analyze the molecular genetics, review existing systems and applications, and address problems as well as potential future developments of the lentiviral vector systems.

A promising strategy for cancer treatment is adoptive gene therapy / immunotherapy by genetically modifying T lymphocytes with a chimeric receptor (ch-TCR) so that cytotoxic T lymphocytes (CTL) can target and lyse tumors in a MHC-non-restricted manner. It is, however, not clear whether non-MHC-restricted tumor cell recognition by T cells will result in activation- induced apoptosis (AICD). This review discusses the factors that affect the development of AICD or CTL proliferation, and how such factors should be considered in the design of clinical trials using ch-TCR.

Gene transfer into stem cells has long been studied as a means by which primitive hematopoietic cells could be characterized and manipulated. While a variety of strategies have been attempted, it still remains relatively difficult to perform direct stem cell analysis. In this review, we examine recent studies using adenovirus-based vectors as a means to achieve high-level gene transfer into primitive hematopoietic cell types.

Enhancement of dermal and epidermal regeneration represents a crucial goal for the treatment of acute, e.g. burn and trauma wounds, and chronic wounds, e.g. diabetic, autoimmune, arterial and venous wounds. Studies defining molecular mechanisms of the complex cascade of wound healing have shown that growth factors represent a new therapeutic strategy. The clinical application of growth factors in the form of proteins has been shown to be of little benefit. Therefore new delivery systems and therapeutic strategies needed to be developed to improve dermal and epidermal regeneration, one of which is gene therapy.For successful gene delivery the selection of an appropriate vector has been shown to be paramount. Because Retroviruses, Adenoviruses and Adeno-Associated Viruses can cause immunologic reactions and mutations, non-viral delivery systems for gene therapy, such as liposomal gene transfer appear advantageous over viral gene therapy. This review discusses the success, potential and limitations of non-viral gene transfer to improve regeneration of dermal and epidermal structures.

The generation of unlimited quantities of neural stem and / or progenitor cells derived from the human brain holds great interest for basic and applied neuroscience. In this article we critically review the origins and recent developments of procedures developed for the expansion, perpetuation, identification, and isolation of human neural precursors, as well as their attributes. Factors influencing their in vitro properties, both under division and after differentiation conditions, are evaluated, with the aim of identifying properties common to the different culture systems reported. This analysis suggests that different culture procedures result in cells with different properties, or even in different cells being isolated. With respect to in vivo performance, present evidence obtained in rodents indicate that cultured human neural precursors, in general, are endowed with excellent integrative properties. Differentiation of the implanted cells, in particular in the case of adult recipients, seems not to be complete, and functionality still needs to be demonstrated. In relation to gene transfer and therapy, aspects currently underexplored, initial data support the view that human neural stem and progenitor cells may serve a role as a platform cell for the delivery of bioactive substances to the diseased CNS. Although a large deal of basic research remains to be done, available data illustrate the enormous potential that human neural precursors isolated, expanded, and characterized in vitro hold for therapeutic applications. In spite of this potential, maintaining a critical view on many unresolved questions will surely help to drive this research field to a good end, that is, the development of real therapies for diseases of the human nervous system.

Hemophilia A and B are hereditary coagulation disorders that result from functional deficiencies of factor VIII (FVIII) or factor IX (FIX), respectively. Current treatment consists of injections with plasma-derived or recombinant clotting factors. Despite the significant clinical benefits of protein replacement therapies, these do not constitute a cure and patients are still at risk of bleeding. Significant progress has been made recently in the development of gene therapy for hemophilia. This has been primarily due to the technical improvements of existing vector systems and the development of new gene delivery methods. Therapeutic and sometimes physiologic levels of FVIII and FIX could be achieved in FVIII- and FIX-deficient mice and hemophilic dogs using different types of viral vectors. In these preclinical studies, long-term correction of the bleeding disorders and in some cases a permanent cure has been realized. However, complications related to the induction of neutralizing antibodies or viral promoter inactivation often precludes stable phenotypic correction. Several gene therapy phase I clinical trials have been initiated in patients suffering from severe hemophilia A or B. The results from the extensive pre-clinical studies and the preliminary clinical data are encouraging. It is likely that successful gene therapy for hemophilia will become a reality at the beginning of this new millennium, serving as the trailblazer for gene therapy of other diseases.