Department of Microbiology and Molecular Genetics - University of Pittsburgh

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Host:  Lauren Kueffer

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“HIV-1 Nef: Biological Probe of Host Cell Kinase Regulation and Drug Target for HIV/AIDS”

Nef is a small, membrane-associated accessory protein of HIV-1 essential for high-titer viral replication, immune escape of HIV-infected cells and AIDS progression. The Nef protein has no known catalytic functions, working instead through protein-protein interactions with host cell pathways involved in endocytic trafficking and signal transduction. In particular, Nef interacts with the macrophage-specific Src-family kinase Hck through its SH3 domain, causing constitutive kinase activation. Selective inhibition of this pathway suppresses viral infectivity, replication and restores immune escape.  More recently, we discovered that Itk and Btk, two members of the Tec-kinase family expressed in HIV-1 host cells, are also activated by Nef.  Itk activation by Nef in CD4 T cells is essential to several stages of the HIV-1 life cycle, offering a unique opportunity for anti-retroviral drug development.

Treatment for HIV disease was revolutionized with the advent of anti-retroviral drugs more than 25 years ago.  Unfortunately, existing anti-retroviral therapy does not clear the virus from the body, requiring life-long drug administration to prevent relapse. Chronic anti-retroviral drug exposure causes clinical metabolic disturbances, organ damage and promotes drug resistance.  To address these issues, our group initiated a drug discovery and development campaign targeting HIV-1 Nef, because of its roles in HIV-1 infectivity, replication, and immune escape of HIV-infected cells.  Using a high-throughput screening platform based on Nef-dependent activation of its host cell partner kinase, Hck, we identified small molecule inhibitors of Nef-dependent enhancement of HIV infectivity and replication.  Remarkably, these compounds also reverse Nef-dependent down-regulation of cell surface MHC-I, resulting in recognition and killing of HIV⁺ CD4 T cells by autologous CD8 cytotoxic T lymphocytes in vitro.  These studies show that Nef antagonists have the potential to restore recognition of HIV-infected cells by the patient’s own immune system, potentially eradicating the virus in vivo.