EFFICIENT TRANSFER, INTEGRATION, AND SUSTAINED LONG-TERM EXPRESSION OF THE TRANSGENE IN ADULT-RAT BRAINS INJECTED WITH A LENTIVIRAL VECTOR

We describe the construction of a safe, replication-defective and effi cient lentiviral vector suitable for in vivo gene delivery. The revers e transcription of the vector was found to be a rate-limiting step; th erefore, promoting the reaction inside the vector particles before del ivery significantly enhanced the efficiency of gene transfer. After in jection into the brain of adult rats, sustained long-term expression o f the transgene was obtained in the absence of detectable pathology. A high proportion of the neurons in the areas surrounding the injection sites of the vector expressed the transduced beta-galactosidase gene. This pattern was invariant in animals sacrificed several months after a single administration of the vector. Transduction occurs by integra tion of the vector genome, as it was abolished by a single amino acid substitution in the catalytic site of the integrase protein incorporat ed in the vector. Development of clinically acceptable derivatives of the lentiviral vector may thus enable the sustained delivery of signif icant amounts of a therapeutic gene product in a wide variety of somat ic tissues.