Development of Replication-Defective Herpes Simplex Virus Vectors

A greater understanding of the molecular, biochemical, and genetic factors involved in the progression of a specific disease state has led to the development of genetic therapies using direct gene transfer to ameliorate the disease condition or correct a genetic defect in situ . Effective gene therapy approaches require delivery strategies and vehicles that 1) efficiently deliver the therapeutic gene(s) to a sufficient number of dividing or nondividing cells to achieve the desired therapeutic effect; 2) persist long term within the cell without disturbing host cell functions; and 3) can regulate the level and duration of therapeutic gene expression for diseases that may either require high-level transient transgene expression or continuous low-level synthesis of the therapeutic product. Numerous viral and nonviral vectors have been employed to treat a variety of genetic and acquired diseases. Each vector system has its own particular advantages and disadvantages that will suit it to a specific therapeutic application.