The interaction between HIV-1 central polypurine tract and host SAMHD1 dNTPase during HIV-1 vector transduction in human primary nondividing monocyte-derived macrophages.

Sterile alpha motif and histidine-aspartate domain-containing protein 1 (SAMHD1) is a dNTPase that depletes intracellular dNTP pools in nondividing cells such as human monocyte-derived macrophages (MDMs). These low dNTP levels suppress HIV-1 reverse transcription kinetics in MDMs. In contrast, viral protein X (Vpx), an accessory protein encoded by human immunodeficiency virus type 2 (HIV-2) and some simian immunodeficiency viruses (SIVs), induces degradation of SAMHD1, thereby increasing cellular dNTP pools and promoting a more permissive infection in MDMs. Our previous study demonstrated that the central polypurine tract (cPPT) facilitates completion of HIV-1 reverse transcription, particularly when reverse transcription is kinetically delayed due to dNTP limitation in nondividing human lung fibroblasts. However, the role of cPPT during HIV-1 replication in macrophages where SAMHD1 establishes low dNTP pools and kinetically restricts viral reverse transcription remains untested. To address this question, we performed time-course analyses of transduction efficiency and fluorescence intensity in MDMs transduced with two distinct HIV-1 vector systems containing or lacking the cPPT sequence, in the presence or absence of Vpx. Our data show that while either cPPT insertion or Vpx treatment alone modestly increases HIV-1 vector transduction efficiency, the combined presence of cPPT and Vpx results in a pronounced enhancement of both transduction efficiency and fluorescence intensity in MDMs. Overall, these findings demonstrate that cPPT and Vpx act cooperatively to enhance HIV-1 vector transduction in nondividing MDMs, supporting an interplay between cPPT function and Vpx-mediated SAMHD1 degradation in macrophages.