STEM CELL DIRECTED GENE THERAPY

Barbara C. Engel and Donald B. Kohn

Division of Research Immunology/Bone Marrow Transplantation, Childrens Hospital Los Angeles, Department of Pediatrics, University of Southern California, School of Medicine

TABLE OF CONTENTS

1. Abstract

2. Introduction

3. Phenotype of hematopoietic stem cells

4. Sources of hematopoietic stem cells

5. Anti-HIV genes

6. Gene transfer into hematopoietic stem cells

6.1. Retroviral vectors
6.2. Lentiviral vectors

7. Gene expression

8. Clinical trials

8.1. Transfer of an anti-HIV-1 ribozyme into CD34⁺ PBSC from HIV-1-positive adults
8.2. Transfer of an RRE decoy gene into CD34⁺ cells from the bone marrow of HIV-1-positive children
8.3. Transfer of an anti-HIV-1 ribozyme into CD34⁺ PBSC from adults with HIV-1 and lymphoma
8.4. Umbilical cord blood cell trial

9. Perspective

10. References

1. ABSTRACT

A potential therapeutic approach to HIV-1 infection is the genetic modification of cells of a patient to make them resistant to HIV-1. Hematopoietic stem cells are an attractive target for gene therapy of AIDS because of their ability to generate a broad repertoire of mature T lymphocytes, as well as the monocytic cells (macrophages, dendritic cells and microglia) which are also involved in HIV-1 pathogenesis. A number of synthetic "anti-HIV-1 genes" have been developed which inhibit HIV-1 replication. However, current methods for gene transfer into human hematopoietic stem cells, using retroviral vectors derived from the Moloney murine leukemia virus, have been minimally effective. Clinical trials performed to date in which hematopoietic cells from HIV-1-positive patients have been transduced with retroviral vectors and then reinfused have produced low to undetectable levels of gene-containing peripheral blood leukocytes. New vector delivery systems, such as lentiviral vectors, need to be developed to ensure efficient gene transfer and persistent transgene expression to provide life-long resistance to the cells targeted by HIV-1.