Single-Cell Imaging Shows That the Transcriptional State of the HIV-1 Provirus and Its Reactivation Potential Depend on the Integration Site

Abstract

A longstanding question exists on the impact of the HIV-1 integration site on viral gene expression. This unsolved question has significant implications for the search toward an HIV-1 cure, as eradication strategies set up to reactivate and eliminate HIV-1 depend on the site where the provirus is integrated.

Determinants of Retroviral Integration and Implications for Gene Therapeutic MLV—Based Vectors and for a Cure for HIV-1 Infection

“…Adverse events with gammaretroviral vectors have shifted the focus of researchers toward lentiviral vectors. Lentiviral vectors prefer to integrate near actively transcribed genes [ 20 , 21 , 22 , 23 ]. LEDGF/p75 can be considered as the ‘GPS’ of the provirus to target the integration to these sites [ 22 , 35 , 36 , 73 , 75 , 78 ].…”

“…With the use of latency–promoting agents (LPAs), the block–and–lock cure strategy strives to generate a cellular reservoir that is resistant to reactivation and unable to rebound after treatment interruption [ 222 , 223 , 224 ]. Several LPAs have been described, such as the Tat inhibitor didehydro–cortistatin A [ 225 , 226 ], curaxin CBL0100 [ 227 ], heat shock protein 90 (HSP90) inhibitors [ 228 ], Janus kinase signal transducer and activator of transcription (JAK–STAT) pathway inhibitors [ 229 ], mammalian target of rapamycin signaling inhibitors [ 230 ] and LEDGINs [ 22 , 23 , 77 ] (for a review, see [ 223 , 231 ]). In this review on retroviral integration, we will further discuss the block–and–lock functional cure with LEDGINs.…”

“…Most recently, Janssens et al underscored again the proof–of–concept for LEDGINs in a block–and–lock cure strategy with branched–DNA (bDNA) imaging. This technique can simultaneously quantify the vDNA and vRNA spots in single cells in HIV latency cell line models and primary cells [ 23 ]. With this approach, Janssens et al investigated how LEDGIN treatment (CX014442) influences the three-dimensional location, basal transcription and TNF—α—mediated reactivation of HIV-1 compared to raltegravir, a clinically approved integrase strand transfer inhibitor [ 23 ].…”

“…This technique can simultaneously quantify the vDNA and vRNA spots in single cells in HIV latency cell line models and primary cells [ 23 ]. With this approach, Janssens et al investigated how LEDGIN treatment (CX014442) influences the three-dimensional location, basal transcription and TNF—α—mediated reactivation of HIV-1 compared to raltegravir, a clinically approved integrase strand transfer inhibitor [ 23 ]. Treatment with LEDGINs and raltegravir dose—dependently decreased the vDNA level, indicating that they both inhibit HIV-1 integration [ 23 ].…”

“…The deltaretroviruses, such as human T lymphotropic virus type 1 and 2 (HTLV-1 and HTLV-2) and bovine leukemia virus (BLV), show a preferential integration pattern into transcriptional units, alphoid repetitive sequences and actively transcribed genes [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. The lentivirus human immunodeficiency virus type 1 (HIV-1) is known to favor integration in decondensed areas of chromatin, which are associated with active transcription [ 20 , 21 , 22 , 23 ]. Other lentiviruses, such as feline immunodeficiency virus (FIV) and simian immunodeficiency virus (SIV), show a similar integration profile, with also a tendency to integrate near RefSeq genes [ 24 , 25 ].…”