Preclinical Demonstration of Lentiviral Vector-mediated Correction of Immunological and Metabolic Abnormalities in Models of Adenosine Deaminase Deficiency

Abstract

Gene transfer into autologous hematopoietic stem cells by γ-retroviral vectors (gRV) is an effective treatment for adenosine deaminase (ADA)-deficient severe combined immunodeficiency (SCID). However, current gRV have significant potential for insertional mutagenesis as reported in clinical trials for other primary immunodeficiencies. To improve the efficacy and safety of ADA-SCID gene therapy (GT), we generated a self-inactivating lentiviral vector (LV) with a codon-optimized human cADA gene under the control of the short form elongation factor-1α promoter (LV EFS ADA). In ADA(-/-) mice, LV EFS ADA displayed high-efficiency gene transfer and sufficient ADA expression to rescue ADA(-/-) mice from their lethal phenotype with good thymic and peripheral T- and B-cell reconstitution. Human ADA-deficient CD34(+) cells transduced with 1-5 × 10(7) TU/ml had 1-3 vector copies/cell and expressed 1-2x of normal endogenous levels of ADA, as assayed in vitro and by transplantation into immune-deficient mice. Importantly, in vitro immortalization assays demonstrated that LV EFS ADA had significantly less transformation potential compared to gRV vectors, and vector integration-site analysis by nrLAM-PCR of transduced human cells grown in immune-deficient mice showed no evidence of clonal skewing. These data demonstrated that the LV EFS ADA vector can effectively transfer the human ADA cDNA and promote immune and metabolic recovery, while reducing the potential for vector-mediated insertional mutagenesis.

Outcomes in Two Japanese Adenosine Deaminase-Deficiency Patients Treated by Stem Cell Gene Therapy with No Cytoreductive Conditioning

“…Following a trend pushed forward by the promising results in recent SCGT trials [15,36], safety in SCGT will be further enhanced by the use of vector systems with better safety characteristics, such as self-inactivating lentiviral vectors [37].…”

Evolving Gene Therapy in Primary Immunodeficiency

“…[33][34][35] Following several years of preclinical development, clinical studies using lentiviral vectors are under way for ADA-SCID. 36 Early indications in more than 32 treated patients, some of whom were identified by newborn screening, are of excellent efficacy and no associated toxicity (H.B. Gaspar and D.B.…”

Cytoreductive conditioning intensity predicts clonal diversity in ADA-SCID retroviral gene therapy patients

“…An adaptation of nonrestrictive linear amplification-mediated PCR (nrLAM-PCR) was used to produce integration site sequencing libraries for Illumina sequencing. 5,[15][16][17][18][19][20][21] …”