Lentiviral Gene Transfer for Treatment of Children Older Than 2 Years of Age With X-Linked Severe Combined Immunodeficiency

Inclusion Criteria: * A proven mutation in the common gamma chain gene as defined by direct sequencing of patient DNA * Human leukocyte antigen (HLA) typing of the patient will have been performed before enrollment * No available HLA matched sibling donor as determined before enrollment. * Must be between 2 and 40 years of age and weigh 10 kg * If previously transplanted, must be 18 months post-hematopoietic stem cell transplant (HSCT) * Expected survival of at least 120 days. * Documented to be negative for HIV infection by genome polymerase chain reaction (PCR) * The patient must be judged by the primary evaluating physician to have a suitable family and social situation consistent with ability to comply with protocol procedures and the long-term follow-up requirements. * Medical lab data (historical) of severe B cell dysfunction (low or absent immunoglobulin G \[IgG\] levels, failed immune response to vaccines); OR demonstrated requirement for intravenous gamma globulin (IVIG) (significant drop over 3 to 6 weeks between peak and trough IgG levels). * Must be willing to have blood and tissue samples stored. IN ADDITION, patients must satisfy the following Laboratory Criteria AND Clinical Criteria: * Laboratory Criteria: (at least 1 must be present) * CD4+ lymphocytes: absolute number less than or equal to 50% of the lower limit of normal (LLN) * CD4+CD45RA+ lymphocytes: absolute number less than or equal to 50% of the LLN OR T-cell receptor excision circles (TRECs) le…