Significance For more than three decades since the discovery of HIV-1, AIDS remains a major public health problem affecting greater than 35.3 million people worldwide. Current antiretroviral therapy has failed to eradicate HIV-1, partly due to the persistence of viral reservoirs. RNA-guided HIV-1 genome cleavage by the Cas9 technology has shown promising efficacy in disrupting the HIV-1 genome in latently infected cells, suppressing viral gene expression and replication, and immunizing uninfected cells against HIV-1 infection. These properties may provide a viable path toward a permanent cure for AIDS, and provide a means to vaccinate against other pathogenic viruses. Given the ease and rapidity of Cas9/guide RNA development, personalized therapies for individual patients with HIV-1 variants can be developed instantly.

The major reservoirs for HIV in the CNS are in the microglia, perivascular macrophages, and to a lesser extent, astrocytes. To study the molecular events controlling HIV expression in the microglia, we developed a reliable and robust method to immortalize microglial cells from primary glia from fresh CNS tissues and commercially available frozen glial cells. Primary human cells, including cells obtained from adult brain tissue, were transformed with lentiviral vectors expressing SV40 T antigen or a combination of SVR40 T antigen and hTERT. The immortalized cells have microglia-like morphology and express key microglial surface markers including CD11b, TGFβR, and P2RY12. Importantly, these cells were confirmed to be of human origin by sequencing. The RNA expression profiles identified by RNA-seq are also characteristic of microglial cells. Furthermore, the cells demonstrate the expected migratory and phagocytic activity, and the capacity to mount an inflammatory response characteristic of primary microglia. The immortalization method has also been successfully applied to a wide range of microglia from other species (macaque, rat, and mouse). To investigate different aspects of HIV molecular regulation in CNS, the cells have been superinfected with HIV reporter viruses and latently infected clones have been selected that reactive HIV in response to inflammatory signals. The cell lines we have developed and rigorously characterized will provide an invaluable resource for the study of HIV infection in microglial cells as well as studies of microglial cell function.Electronic supplementary materialThe online version of this article (doi:10.1007/s13365-016-0499-3) contains supplementary material, which is available to authorized users.

BackgroundMultiple toll-like receptors (TLRs) are expressed in cells of the monocytic lineage, including microglia, which constitute the major reservoir for human immunodeficiency virus (HIV) infection in the brain. We hypothesized that TLR receptor mediated responses to inflammatory conditions by microglial cells in the central nervous system (CNS) are able to induce latent HIV proviruses, and contribute to the etiology of HIV-associated neurocognitive disorders.ResultsNewly developed human microglial cell lines (hµglia), obtained by immortalizing human primary microglia with simian virus-40 (SV40) large T antigen and the human telomerase reverse transcriptase, were used to generate latently infected cells using a single-round HIV virus carrying a green fluorescence protein reporter (hµglia/HIV, clones HC01 and HC69). Treatment of these cells with a panel of TLR ligands showed surprisingly that two potent TLR3 agonists, poly (I:C) and bacterial ribosomal RNA potently reactivated HIV in hμglia/HIV cells. LPS (TLR4 agonist), flagellin (TLR5 agonist), and FSL-1 (TLR6 agonist) reactivated HIV to a lesser extent, while Pam3CSK4 (TLR2/1 agonist) and HKLM (TLR2 agonist) only weakly reversed HIV latency in these cells. While agonists for TLR2/1, 4, 5 and 6 reactivated HIV through transient NF-κB induction, poly (I:C), the TLR3 agonist, did not activate NF-κB, and instead induced the virus by a previously unreported mechanism mediated by IRF3. The selective induction of IRF3 by poly (I:C) was confirmed by chromatin immunoprecipitation (ChIP) analysis. In comparison, in latently infected rat-derived microglial cells (hT-CHME-5/HIV, clone HC14), poly (I:C), LPS and flagellin were only partially active. The TLR response profile in human microglial cells is also distinct from that shown by latently infected monocyte cell lines (THP-1/HIV, clone HA3, U937/HIV, clone HUC5, and SC/HIV, clone HSCC4), where TLR2/1, 4, 5, 6 or 8, but not for TLR3, 7 or 9, reactivated HIV.ConclusionsTLR signaling, in particular TLR3 activation, can efficiently reactivate HIV transcription in infected microglia, but not in monocytes or T cells. The unique response profile of microglial cells to TLR3 is fundamental to understanding how the virus responds to continuous microbial exposure, especially during inflammatory episodes, that characterizes HIV infection in the CNS.Electronic supplementary materialThe online version of this article (doi:10.1186/s12977-017-0335-8) contains supplementary material, which is available to authorized users.

Despite effective antiretroviral therapy (

CRISPR-Cas9/gRNA exhibits therapeutic efficacy against latent human immunodeficiency virus (HIV) genome but the delivery of this therapeutic cargo to the brain remains as a challenge. In this research, for the first time, we demonstrated magnetically guided non-invasive delivery of a nano-formulation (NF), composed of Cas9/gRNA bound with magneto-electric nanoparticles (MENPs), across the blood-brain barrier (BBB) to inhibit latent HIV-1 infection in microglial (hμglia)/HIV (HC69) cells. An optimized ac-magnetic field of 60 Oe was applied on NF to release Cas9/gRNA from MENPs surface and to facilitate NF cell uptake resulting in intracellular release and inhibition of HIV. The outcomes suggested that developed NF reduced HIV-LTR expression significantly in comparison to unbound Cas9/gRNA in HIV latent hμglia/HIV (HC69) cells. These findings were also validated qualitatively using fluorescence microscopy to assess NF efficacy against latent HIV in the microglia cells. We believe that CNS delivery of NF (CRISPR/Cas9-gRNA-MENPs) across the BBB certainly will have clinical utility as future personalized nanomedicine to manage neuroHIV/AIDS.

The 18 kDa translocator protein (TSPO) is an evolutionary conserved cholesterol binding protein localized in the outer mitochondrial membrane. It has been implicated in the regulation of various cellular processes including oxidative stress, proliferation, apoptosis, and steroid hormone biosynthesis. Since the expression of TSPO in activated microglia is upregulated in various neuroinflammatory and neurodegenerative disorders, we set out to examine the role of TSPO in an immortalized human microglia C20 cell line. To this end, we performed a dual approach and used (i) lentiviral shRNA silencing to reduce TSPO expression, and (ii) the CRISPR/Cas9 technology to generate complete TSPO knockout microglia cell lines. Functional characterization of control and TSPO knockdown as well as knockout cells, revealed only low de novo steroidogenesis in C20 cells, which was not dependent on the level of TSPO expression or influenced by the treatment with TSPO-specific ligands. In contrast to TSPO knockdown C20 cells, which did not show altered mitochondrial function, the TSPO deficient knockout cells displayed a significantly decreased mitochondrial membrane potential and cytosolic Ca2+ levels, as well as reduced respiratory function. Performing the rescue experiment by lentiviral overexpression of TSPO in knockout cells, increased oxygen consumption and restored respiratory function. Our study provides further evidence for a significant role of TSPO in cellular and mitochondrial metabolism and demonstrates that different phenotypes of mitochondrial function are dependent on the level of TSPO expression.

We have developed models of HIV latency using microglia derived from adult human patient brain cortex and transformed with the SV40 T large and hTERT antigens. Latent clones infected by HIV reporter viruses display high levels of spontaneous HIV reactivation in culture. BrainPhys, a medium highly representative of the CNS extracellular environment, containing low glucose and 1% FBS, reduced, but did not prevent, HIV reactivation. We hypothesized that spontaneous HIV reactivation in culture was due to the expression of pro-inflammatory genes, such as TNF-α, taking place in the absence of the natural inhibitory signals from astrocytes and neurons. Indeed, expression and secretion of TNF-α is strongly reduced in HIV-latently infected microglia compared to the subset of cells that have undergone spontaneous HIV reactivation. Whereas inhibitors of NF-κB or of macrophage activation only had a short-term silencing effect, addition of dexamethasone (DEXA), a glucocorticoid receptor (GR) agonist and mediator of anti-inflammation, silenced the HIV provirus in a long-term, and shRNA-mediated knock-down of GR activated HIV. DEXA also decreased secretion of a number of cytokines, including TNF-α. Chromatin immunoprecipitation analysis revealed that DEXA strongly increased GR occupancy at the HIV promoter, and reduced histone 3 acetylated levels. Moreover, TNF-α expression inhibitors in combination with DEXA induced further HIV silencing and increased the histone 3 lysine 27 tri-methylated epigenetic mark of repression at the HIV promoter region. We conclude that GR is a critical repressor of HIV transcription in microglia, and a novel potential pharmacological target to restrict HIV expression in the CNS.

Most studies of HIV latency focus on the peripheral population of resting memory T cells, but the brain also contains a distinct reservoir of HIV-infected cells in microglia, perivascular macrophages, and astrocytes. Studying HIV in the brain has been challenging, since live cells are difficult to recover from autopsy samples and primate models of SIV infection utilize viruses that are more myeloid-tropic than HIV due to the expression of Vpx. Development of a realistic small animal model would greatly advance studies of this important reservoir and permit definitive studies of HIV latency. When radiation or busulfan-conditioned, immune-deficient NSG mice are transplanted with human hematopoietic stem cells, human cells from the bone marrow enter the brain and differentiate to express microglia-specific markers. After infection with replication competent HIV, virus was detected in these bone marrow-derived human microglia. Studies of HIV latency in this model would be greatly enhanced by the development of compounds that can selectively reverse HIV latency in microglial cells. Our studies have identified members of the CoREST repression complex as key regulators of HIV latency in microglia in both rat and human microglial cell lines. The monoamine oxidase (MAO) and potential CoREST inhibitor, phenelzine, which is brain penetrant, was able to stimulate HIV production in human microglial cell lines and human glial cells recovered from the brains of HIV-infected humanized mice. The humanized mice we have developed therefore show great promise as a model system for the development of strategies aimed at defining and reducing the CNS reservoir.