Review HIV protease as a target for retrovirus vector-mediated gene therapy Stephen Todd a ; *, Carol-Gay Anderson d , Douglas J. Jolly d , Charles S. Craik ac a Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94143-0446, USA b Department of Molecular and Cellular Pharmacology, University of California, San Francisco, San Francisco, CA 94143-0446, USA c Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143-0446, USA d Chiron Technologies, Center for Gene Therapy, 11055 Roselle St., San Diego, CA 92121-1204, USA Received 1 November 1999; accepted 1 December 1999 Abstract The dimeric aspartyl protease of HIV has been the subject of intense research for almost a decade. Knowledge of the substrate specificity and catalytic mechanism of this enzyme initially guided the development of several potent peptidomimetic small molecule inhibitors. More recently, the solution of the HIV protease structure led to the structure- based design of improved peptidomimetic and non-peptidomimetic antiviral compounds. Despite the qualified success of these inhibitors, the high mutation rate associated with RNA viruses continues to hamper the long-term clinical efficacy of HIV protease inhibitors. The dimeric nature of the viral protease has been conducive to the investigation of dominant- negative inhibitors of the enzyme. Some of these inhibitors are defective protease monomers that interact with functional monomers to form inactive protease heterodimers. An advantage of macromolecular inhibitors as compared to small- molecule inhibitors is the increased surface area of interaction between the inhibitor and the target gene product. Point mutations that preserve enzyme activity but confer resistance to small-molecule inhibitors are less likely to have an adverse effect on macromolecular interactions. The use of efficient retrovirus vectors has facilitated the delivery of these macromolecular inhibitors to primary human lymphocytes. The vector-transduced cells were less susceptible to HIV infection in vitro, and showed similar levels of protection compared to other macromolecular inhibitors of HIV replication, such as RevM10. These preliminary results encourage the further development of dominant-negative HIV protease inhibitors as a gene therapy-based antiviral strategy. ß 2000 Elsevier Science B.V. All rights reserved. Keywords : HIV protease inhibitor ; Transdominant ; Dominant-negative ; Gene therapy ; Retrovirus vector ; Lentivirus 1. Overview The widespread use of small-molecule human im- munode¢ciency virus (HIV) protease (PR) inhibitors has resulted in the ¢rst signi¢cant reduction in the number of acquired immune de¢ciency syndrome (AIDS)-related deaths since the beginning of the epi- demic (see [1] and references within). The initial suc- cess of PR inhibitors validates the enzyme as a target for antiviral therapy, although the emergence of PR inhibitor-resistant virus strains threatens to circum- vent the e¤cacy of these drugs. As pharmaceutical manufacturers design new peptidomimetic and non- peptidomimetic PR inhibitors aimed at reducing the incidence of resistance, many laboratories continue to explore alternative strategies for controlling HIV replication. Some of these strategies involve macro- molecular inhibitors that target speci¢c HIV gene 0167-4838 / 00 / $ ^ see front matter ß 2000 Elsevier Science B.V. All rights reserved. PII:S0167-4838(99)00272-1 * Corresponding author. Fax: +1-415-502-8298; E-mail : todd@cgl.ucsf.edu Biochimica et Biophysica Acta 1477 (2000) 168^188 www.elsevier.com/locate/bba