A Fluorescence Polarization Assay for High-Throughput Screening of Inhibitors Against HIV-1 Nef-mediated MHC-I Downregulation.

The multifunctional, HIV-1 accessory protein Nef enables infected cells to evade host immunity and thus plays a key role in viral pathogenesis. One prominent function of Nef is the downregulation of major histocompatibility complex class I (MHC-I), which disrupts antigen presentation and thereby allows the infected cells to evade immune surveillance by the cytotoxic T cells. Therapeutic inhibition of this Nef function is a promising direction of antiretroviral drug discovery as it may revitalize cytotoxic T cells to identify, and potentially clear, hidden HIV-1 infections. Guided by the crystal structure of the protein complex formed between Nef, MHC-I, and the hijacked clathrin adaptor protein complex 1, we have developed a fluorescence polarization-based assay for inhibitor screening against Nef's activity on MHC-I. The optimized assay has a good signal-to-noise ratio, substantial tolerance of dimethylsulfoxide, and excellent ability to detect competitive inhibition, indicating that it is suitable for high-throughput screening.