Biochemical Mechanism of HIV DNA Integration

HIV-1 remains a significant health problem. In 2022, 1.3 million people became infected globally, and 0.63 million people died from AIDS. 39 million people currently live with HIV. We still lack effective vaccine and cure strategies. Antiretroviral inhibitors, which mainly target HIV-1 enzyme activities, have however altered the course of the HIV/AIDS pandemic. Drug cocktails composed of two nucleoside reverse transcriptase inhibitors and a second-generation integrase strand transfer inhibitor are commonly prescribed for drug-naïve patients as well as individuals failing non-integrase inhibitor containing regimens. Integrase is the viral enzyme responsible for integrating the viral reverse transcript into a cellular chromosome, which most often occurs in concert with the chromatin-binding host protein lens epithelium-derived growth factor (LEDGF)/p75. The binding of integrase to LEDGF/p75 targets integration to the mid-regions of active genes to enhance subsequent transcription and HIV-1 pathogenesis. This grant over its lifetime has contributed seminal results to the biochemical mechanism of HIV DNA integration, including the co-discovery of LEDGF/p75 as an integrase binding protein, as well as the determination of the part of LEDGF/p75 that binds integrase and 3- dimensional (3d) structure determinations of the LEDGF/p75 integrase binding domain (IBD) and IBD- integrase complexes. Such results set the stage for the discovery of allosteric integrase inhibitors (ALLINIs), which compete for LEDGF/p75 binding to the integrase catalytic core domain dimerization interface, and, as a consequence, impart aberrant, multi-chain integrase polymerization that inhibits integrase binding to RNA in virus particles and the morphological transformation of non-infectious immature viruses to infectious mature virions. The most recent iteration of this grant described pirmitegravir, the first ALLINI to advance to phase II clinical trials, and solved high resolution 3d structures of ALLINIs bound to the complete integrase binding interface that includes the integrase C-terminal domain in addition to the catalytic core domain dimer. Although HIV-1 integration occurs in human chromatin, the precise nature of LEDGF/p75 chromatin binding activity in HIV-1 integration targeting is unknown and will be determined in this R37 extension application. Prior to integration, virus capsid-host factor interactions enable HIV-1 nuclear incursion, but pathways taken downstream from capsid-host factor engagement to LEDGF/p75-dependent integration are also unknown and will accordingly be determined herein. Finally, to emulate our ALLINI discoveries and to define new integrase interfaces for pharmacological development, we will characterize and determine 3d structures of novel host factor-integrase complexes. RELEVANCE (See instructions): Continual antiviral inhibitor development is important to keep the HIV/AIDS pandemic in check, and we previously described allosteric integrase inhibitors that compete for LEDGF/p75-integrase binding. LEDGF/p75 directs integration into active genes, and this grant will elucidate molecular details of LEDGF/p75 action in HIV-1 integration. We will also characterize novel integrase-host factor complexes to define new targets for future drug development. Project Number: 4R37AI039394-30 | Fiscal Year: 2025 | NIH Institute/Center: National Institute of Allergy and Infectious Diseases (NIAID) | Principal Investigator: Alan Engelman | Institution: DANA-FARBER CANCER INST, BOSTON, MA | Award Amount: $819,601 | Activity Code: R37 | Study Section: NSS View on NIH RePORTER: https://reporter.nih.gov/project-details/4R37AI03939430