Direct gene transfer into human epileptogenic hippocampal tissue with an adeno-associated virus vector: Implications for a gene therapy approach to epilepsy

Purpose: Virus vectors capable of transferring genetic information into human cells provide hope for improved therapy in several neurological diseases, including epilepsy. We evaluated the ability of an adeno-associated virus (AAV) vector to transfer and cause expression of a lacZ marker gene in brain slices obtained from patients undergoing temporal lobectomy for control of medically intractable seizures. Methods: Human brain slices were injected with an AAV vector (AAVlacZ) encoding Escherichia coli β-galactosidase and incubated for as long as 24 h. The presence of lacZ mRNA. β-galactosidase protein and enzymatic activity were assayed by reverse transcriptase polymerase chain reaction (rtPCR), immunocytochemistry, and the X-Gal technique, respectively. Results: AAVlacZ directed the expression in human epileptogenic brain of E. coil β-galactosidase that had functional activity. Expression was observed in ≤5 h and was sustained for as long as the slices were viable. Morphological analysis indicated that neurons were preferentially transfected, and there was no evidence of cytotoxicity. Conclusions: Our results confirm the feasibility of using AAV vectors to transfer genes into the human CNS and in particular, into neurons. Replacement of the lacZ gene with a functional gene modulating hippocampal neuronal physiology, might allow a localized genetic intervention for focal seizures based on the stereotaxic or endovascular delivery of such a vector system into the appropriate brain region.