Approaches to Inhibit HIV through Enhancement of Tetherin Restriction

Paula Cannon, University of Southern California, Los Angeles
Basic Biomedical Sciences
Innovative, Developmental, Exploratory Award (IDEA)

The human protein Tetherin/BST-2 has recently been identified as a cellular factor that 'tethers' newly budded HIV particles at the surface of a cell, and thereby reduces the yield of infectious virions. Tetherin also restricts the release of other enveloped viruses, such as filoviruses and arenaviruses, suggesting that it may be part of an intrinsic cellular defense against enveloped viruses. Significantly, HIV codes for two distinct proteins that counteract Tetherin, the HIV-1 Vpu protein and the HIV-2 Env protein. In addition, the Kaposi’s sarcoma-associated herpesvirus (KSHV), which can be a significant complication of HIV infections, also expresses an anti-Tetherin factor, K5. The fact that at least 3 human pathogens encode proteins that target Tetherin suggests that viral anti-Tetherin factors represent important new targets for therapeutic interventions.
We have recently found that removal of Tetherin from the cell surface by Vpu, HIV-2 Env and K5 is the basis of their anti-Tetherin activity. We therefore hypothesize that surrogate Tetherin-based reporters could be developed that recapitulated this interaction, and could thereby form the basis of high-throughput screens to identifying compounds that blocked anti-Tetherin activities. Towards that goal we have identified a minimal region of Tetherin that can be fused to reporter constructs (eGFP and luciferase) to produce a cell surface signal that is downregulated by Vpu and K5. The goal of this proposal is to develop additional regents, including Tetherin-enzyme fusions, to provide sensitive, one-well HTS capabilities, and use these reagents to screen small molecule libraries. Any candidates identifed by such screens will be further investigated for anti-HIV activity, and to understand their mechanism of action.