Gene therapy for leukocyte adhesion deficiency

Leukocyte adhesion deficiency (LAD) is an autosomal recessive immunodeficiency disease characterized by severe, recurrent bacterial infections. In patients with LAD, the leukocytes, particularly the neutrophils, fail to adhere to the endothelial cell wall and migrate to the site of infection. LAD results from heterogeneous molecular defects in the leukocyte integrin CD18, which prevent CD11/CD18 heterodimer formation and surface expression. To date, hematopoietic stem cell transplantation remains the only curative treatment for LAD, however, this approach is limited by transplant-related toxicities and graft-versus-host disease. During the course of the preceding decade we have conducted extensive experimental studies demonstrating that gene transfer of the CD18 subunit corrects the structural and functional defect in LAD leukocytes. These studies provided the support for the initiation of a clinical trial of retroviral-mediated gene transfer of CD18 in two patients with the severe deficiency phenotype or LAD. This review will present an overview of LAD, preclinical CD18 gene transfer studies and the initial results from the current clinical trial.