A simultaneous knockout knockin genome editing strategy in HSPCs potently inhibits CCR5- and CXCR4-tropic HIV-1 infection

Allogeneic hematopoietic stem and progenitor cell transplant (HSCT) of CCR5 null (CCR5Δ32) cells can be curative for HIV-1-infected patients. However, because allogeneic HSCT poses significant risk, CCR5Δ32 matched bone marrow donors are rare, and CCR5Δ32 transplant does not confer resistance to the CXCR4-tropic virus, it is not a viable option for most patients. We describe a targeted Cas9/AAV6-based genome editing strategy for autologous HSCT resulting in both CCR5- and CXCR4-tropic HIV-1 resistance. Edited human hematopoietic stem and progenitor cells (HSPCs) maintain multi-lineage repopulation capacity in vivo, and edited primary human T cells potently inhibit infection by both CCR5-tropic and CXCR4-tropic HIV-1. Modification rates facilitated complete loss of CCR5-tropic replication and up to a 2,000-fold decrease in CXCR4-tropic replication without CXCR4 locus disruption. This multi-factor editing strategy in HSPCs could provide a broad approach for autologous HSCT as a functional cure for both CCR5-tropic and CXCR4-tropic HIV-1 infections.

The SAMHD1 dNTP Triphosphohydrolase Is Controlled by a Redox Switch

AIMS

Proliferative signaling involves reversible posttranslational oxidation of proteins. However, relatively few molecular targets of these modifications have been identified. We investigate the role of protein oxidation in regulation of SAMHD1 catalysis.

RESULTS

Here we report that SAMHD1 is a major target for redox regulation of nucleotide metabolism and cell cycle control. SAMHD1 is a triphosphate hydrolase, whose function involves regulation of deoxynucleotide triphosphate pools. We demonstrate that the redox state of SAMHD1 regulates its catalytic activity. We have identified three cysteine residues that constitute an intrachain disulfide bond "redox switch" that reversibly inhibits protein tetramerization and catalysis. We show that proliferative signals lead to SAMHD1 oxidation in cells and oxidized SAMHD1 is localized outside of the nucleus. Innovation and Conclusions: SAMHD1 catalytic activity is reversibly regulated by protein oxidation. These data identify a previously unknown mechanism for regulation of nucleotide metabolism by SAMHD1. Antioxid. Redox Signal. 27, 1317-1331.

TLR7/8 agonist induces a post-entry SAMHD1-independent block to HIV-1 infection of monocytes

Background

Monocytes, the primary myeloid cell-type in peripheral blood, are resistant to HIV-1 infection as a result of the lentiviral restriction factor SAMHD1. Toll-like receptors recognize microbial pathogen components, inducing the expression of antiviral host proteins and proinflammatory cytokines. TLR agonists that mimic microbial ligands have been found to have activity against HIV-1 in macrophages. The induction of restriction factors in monocytes by TLR agonist activation has not been well studied. To analyze restriction factor induction by TLR activation in monocytes, we used the imidazoquinoline TLR7/8 agonist R848 and infected with HIV-1 reporter virus that contained packaged viral accessory protein Vpx, which allows the virus to escape SAMHD1-mediated restriction. 

Results

R848 prevented the replication of Vpx-containing HIV-1 and HIV-2 in peripheral blood mononuclear cells and monocytes. The block was post-entry but prior to reverse transcription of the viral genomic RNA. The restriction was associated with destabilization of the genomic RNA molecules of the in-coming virus particle. R848 treatment of activated T cells did not protect them from infection but treated monocytes produced high levels of proinflammatory cytokines, including type-I IFN that protected bystander activated T cells from infection.

Conclusion

The activation of TLR7/8 induces two independent restrictions to HIV-1 replication in monocytes: a cell-intrinsic block that acts post-entry to prevent reverse transcription; and a cell-extrinsic block, in which monocytes produce high levels of proinflammatory cytokines (primarily type-I IFN) that protects bystander monocytes and T lymphocytes. The cell-intrinsic block may result from the induction of a novel restriction factor, which can be termed Lv5 and acts by destabilizing the in-coming viral genomic RNA, either by the induction of a host ribonuclease or by disrupting the viral capsid. TLR agonists are being developed for therapeutic use to diminish the size of the latent provirus reservoir in HIV-1 infected individuals. Such drugs may both induce latent provirus expression and restrict virus replication during treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-016-0316-3) contains supplementary material, which is available to authorized users.

Catalytic activity of APOBEC3F is required for efficient restriction of Vif-deficient human immunodeficiency virus

APOBEC3 proteins are DNA cytosine deaminases that restrict the replication of human immunodeficiency virus deficient in the counterdefense protein Vif. Here, we address the capacity of APOBEC3F to restrict via deaminase-dependent and -independent mechanisms by monitoring spreading infections in diverse T cell lines. Our data indicate that only a deaminase-proficient protein is capable of long-term restriction of Vif-deficient HIV in T cells, analogous to prior reports for APOBEC3G. This indicates that the principal mechanism of APOBEC3F restriction is deaminase-dependent.