Therapeutic doses of irradiation activate viral transcription and induce apoptosis in HIV-1 infected cells

Abstract

The highly active antiretroviral therapy reduces HIV-1 RNA in plasma to undetectable levels. However, the virus continues to persist in the long-lived resting CD4+ T cells, macrophages and astrocytes which form a viral reservoir in infected individuals. Reactivation of viral transcription is critical since the host immune response in combination with antiretroviral therapy may eradicate the virus. Using the chronically HIV-1 infected T lymphoblastoid and monocytic cell lines, primary quiescent CD4+ T cells and humanized mice infected with dual-tropic HIV-1 89.6, we examined the effect of various X-ray irradiation (IR) doses (used for HIV-related lymphoma treatment and lower doses) on HIV-1 transcription and viability of infected cells. Treatment of both T cells and monocytes with IR, a well-defined stress signal, led to increase of HIV-1 transcription, as evidenced by the presence of RNA polymerase II and reduction of HDAC1 and methyl transferase SUV39H1 on the HIV-1 promoter. This correlated with the increased GFP signal and elevated level of intracellular HIV-1 RNA in the IR-treated quiescent CD4+ T cells infected with GFP-encoding HIV-1. Exposition of latently HIV-1infected monocytes treated with PKC agonist bryostatin 1 to IR enhanced transcription activation effect of this latency-reversing agent. Increased HIV-1 replication after IR correlated with higher cell death: the level of phosphorylated Ser46 in p53, responsible for apoptosis induction, was markedly higher in the HIV-1 infected cells following IR treatment. Exposure of HIV-1 infected humanized mice with undetectable viral RNA level to IR resulted in a significant increase of HIV-1 RNA in plasma, lung and brain tissues. Collectively, these data point to the use of low to moderate dose of IR alone or in combination with HIV-1 transcription activators as a potential application for the “Shock and Kill” strategy for latently HIV-1 infected cells.

Humanized Mouse Model of HIV-1 Latency with Enrichment of Latent Virus in PD-1 + and TIGIT + CD4 T Cells

“…Several humanized mouse models have been developed to study HIV-1 replication and latency (30,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44). Mice containing human CD4 T cells support both R5-and X4-tropic HIV-1 infections (reviewed in reference 45) and respond to treatment with ART, typically administered by intraperitoneal (i.p.)…”

“…injections (34-36, 38-42, 44) or, less commonly, by addition to drinking water (40,43) or food (37,41,44). The presence of a latent reservoir in ART-treated humanized mice is inferred by observing virus rebound following withdrawal of ART (37,38,41,(43)(44)(45), with estimates of the size of the reservoir obtained by measuring the total HIV-1 DNA load in the human cells in the animals by qPCR (30,37,39,41,43). The QVOA has also been adapted for mouse models, although the requirement for large numbers of cells in order to detect latent, reactivatable, and infectious genomes in ART-treated mice required pooling of several tissues (30,34,35,38,43).…”

HIV-1 Latency and Eradication: Past, Present and Future

“…Using the SCID-hu model, it has been shown that IL-7 induces substantial expression of latent HIV while having minimal effects on the cell phenotype [68]. In a recent study using HIV-1 infected NSG humanized mice with undetected basal levels of viral replication, a dramatic increase in HIV-1 RNA in plasma, lung and brain tissues were observed following ionizing radiation-induced cellular stress [69]. …”

Potential of Radiation-Induced Cellular Stress for Reactivation of Latent HIV-1 and Killing of Infected Cells

“…28 Recent clinical studies that included analysis of CD4 + T-cell count in the blood from cancer patients infected or not with HIV-1 indicated that radiation therapy reduced the CD4 + cell count more dramatically in HIV-1-infected individuals. 25,29 Treatment with NNRTIbased ART exacerbated this effect.…”

“…31,32 Nevertheless, the combination of moderate doses of IR with chemical compound, PKC agonist bryostatin 1, enhanced transcription activation and cell killing in monocyte/macrophages. 28 This suggests that the IR effect is cell-type specific and that infected T cells are more prone to apoptosis with IR, whereas IR with LRAs is needed to kill infected myeloid cells.…”