HIV-1 Tat蛋白与艾滋病脑病

Tat 蛋白是HIV-1 编码的反式转录激活因子,其主要功能是反式激活HIV-1病毒基因组转录的起始和延伸,启动病毒复制.近年来研究发现,Tat 蛋白在HIV-1感染所引起的严重中枢神经系统（CNS）并发症--艾滋病脑病中起重要作用,是艾滋病脑病发生与发展的重要致病因子.本文就HIV-1 Tat蛋白在艾滋病脑病中的研究进展作一综述.     

Single-Cell and Single-Cycle Analysis of HIV-1 Replication

The dynamics of the late stages of the HIV-1 life cycle are poorly documented. Viral replication dynamics are typically measured in populations of infected cells, but asynchrony that is introduced during the early steps of HIV-1 replication complicates the measurement of the progression of subsequent steps and can mask replication dynamics and their variation in individual infected cells. We established microscopy-based methods to dynamically measure HIV-1-encoded reporter gene and antiviral gene expression in individual infected cells. We coupled these measurements with conventional analyses to quantify delays in the HIV-1 replication cycle imposed by the biphasic nature of HIV-1 gene expression and by the assembly-inhibiting property of the matrix domain of Gag. We further related the dynamics of restriction factor (APOBEC3G) removal to the dynamics of HIV-1 replication in individual cells. These studies provide a timeline for key events in the HIV-1 replication cycle, and reveal that the interval between the onset of early and late HIV-1 gene expression is only ~3h, but matrix causes a ~6–12h delay in the generation of extracellular virions. Interestingly, matrix delays particle assembly to a time at which APOBEC3G has largely been removed from the cell. Thus, a need to prepare infected cells to be efficient producers of infectious HIV-1 may provide an impetus for programmed delays in HIV-1 virion genesis. Our findings also emphasize the significant heterogeneity in the length of the HIV-1 replication cycle in homogenous cell populations and suggest that a typical infected cell generates new virions for only a few hours at the end of a 48h lifespan. Therefore, small changes in the lifespan of infected cells might have a large effect on viral yield in a single cycle and the overall clinical course in infected individuals.     

Increased human immunodeficiency virus type 1 (HIV-1) env compartmentalization in the presence of HIV-1-associated dementia

The human immunodeficiency virus type 1 (HIV-1) surface Env protein has been implicated in the development of HIV-1-associated dementia (HAD). HIV-1 env diversity was analyzed by heteroduplex tracking assay in 27 infected subjects with various neurological statuses. env compartmentalization between the blood and cerebral spinal fluid (CSF) was apparent with all neurological categories. However, in subjects with HAD, significantly more CSF virus was represented by CNS-unique env variants. Variants specialized for replication in the CNS may play a larger role in the development of HAD. Alternatively, HAD may be associated with a more pronounced state of immunosuppression that permits more extensive replication and independent evolution within the CNS compartment.     

Efficient Gene Transfer Mediated by HIV-1-based Defective Lentivector and Inhibition of HIV-1 Replication

Lentiviral vectors have drawn considerable attention recently and show great promise to become important delivery vehicles for future gene transfer manipulation. In the present study we have optimized a protocol for preparation of human immunodeficiency virus type-1 (HIV-1)-based defective lentiviral vectors (DLV) and characterized these vectors in terms of their transduction of different cells. Transient co-transfection of 293T packaging cells with DNA plasmids encoding lentiviral vector constituents resulted in production of high-titer DLV (0.5-1.2 × 107IU/mL), which can be further concentrated over 100-fold through a single step ultracentrifugation. These vectors were capable of transducing a variety of cells from both primate and non-primate sources and high transduction efficiency was achieved using concentrated vectors. Assessment of potential generation of RCV revealed no detection of infection by infectious particles in DLV-transduced CEM, SupT-1 and MT-2 cells. Long-term culture of transduced cells showed a stable expression of transgenes without apparent alteration in cellular morphology and growth kinetics. Vector mobilization to untransduced cells mediated by wild-type HIV-1 infection was confirmed in this test. Challenge of transduced human T-lymphocytes with wild-type HIV-1 showed these cells are totally resistant to the viral infection. Considering the effective gene transfer and stable gene expression, safety and anti-HIV activity, these DLV vectors warrant further exploration for their potential use as a gene transfer vehicle in the development of gene therapy protocols.     

Quantitative Comparison of HTLV-1 and HIV-1 Cell-to-Cell Infection with New Replication Dependent Vectors

We have developed an efficient method to quantify cell-to-cell infection with single-cycle, replication dependent reporter vectors. This system was used to examine the mechanisms of infection with HTLV-1 and HIV-1 vectors in lymphocyte cell lines. Effector cells transfected with reporter vector, packaging vector, and Env expression plasmid produced virus-like particles that transduced reporter gene activity into cocultured target cells with zero background. Reporter gene expression was detected exclusively in target cells and required an Env-expression plasmid and a viral packaging vector, which provided essential structural and enzymatic proteins for virus replication. Cell-cell fusion did not contribute to infection, as reporter protein was rarely detected in syncytia. Coculture of transfected Jurkat T cells and target Raji/CD4 B cells enhanced HIV-1 infection two fold and HTLV-1 infection ten thousand fold in comparison with cell-free infection of Raji/CD4 cells. Agents that interfere with actin and tubulin polymerization strongly inhibited HTLV-1 and modestly decreased HIV-1 cell-to-cell infection, an indication that cytoskeletal remodeling was more important for HTLV-1 transmission. Time course studies showed that HTLV-1 transmission occurred very rapidly after cell mixing, whereas slower kinetics of HIV-1 coculture infection implies a different mechanism of infectious transmission. HTLV-1 Tax was demonstrated to play an important role in altering cell-cell interactions that enhance virus infection and replication. Interestingly, superantigen-induced synapses between Jurkat cells and Raji/CD4 cells did not enhance infection for either HTLV-1 or HIV-1. In general, the dependence on cell-to-cell infection was determined by the virus, the effector and target cell types, and by the nature of the cell-cell interaction.     

Control of cell adhesion and compartmentalization in the intestinal epithelium

Continuous cell renewal in the intestinal mucosa occurs without disrupting the integrity of the epithelial layer. Despite the restrictions imposed by strong cell-to-cell adhesions, epithelial intestinal cells migrate constantly between tissue compartments. Alterations in cell adhesion and compartmentalization play key roles in diseases of the intestine. In particular, decreased E-cadherin-mediated adhesion during inflammatory bowel disease and loss of EphB/ephrin-B-mediated compartmentalization in colorectal cancer have recently emerged as key players of these prevalent pathologies. Here we will review our current knowledge on how cell-to-cell adhesion, migration and cell positioning are coordinated in the intestinal epithelium. We will highlight what the in vivo genetic analysis of intestinal epithelium has taught us about the complex regulation of cell adhesion and migration in homeostasis and disease.     

Role of Cellular DNA Repair Systems in HIV-1 Replication

Molecular Biology - A serious problem in the treatment of HIV infection is the emergence of drug-resistant forms of the virus. One promising approach to solving this problem is the development of...     

Selection promotes organ compartmentalization in HIV-1: evidence from gag and pol genes

The existence of organ-specific human immunodeficiency virus type 1 (HIV-1) populations within infected hosts has been long lasting studied. Previous work established that population subdivision by organs occurs at the envelope env gene, but less is known about other genomic regions. Here, we used a population genetics approach to detect organ compartmentalization in proviral sequences of HIV-1 gag and pol genes. Significant population structure was found in pol (100% of cases) and gag (33%) pair-wise organ comparisons. The degree of compartmentalization positively correlated with the ratio of nonsynonymous to synonymous substitutions, and codons showing organ compartmentalization were more likely to be under significantly positive selection. This suggests that HIV-1 populations dynamically adapt to locally variable intra-host environments. In the case of pol gene, differential penetration of antiretroviral drugs might account for the observed pattern, whereas for gag gene, local selective pressures remain unexplored.     

Early Combination Antiretroviral Therapy Limits Exposure to HIV-1 Replication and Cell-Associated HIV-1 DNA Levels in Infants

The primary aim of this study was to measure HIV-1 persistence following combination antiretroviral therapy (cART) in infants and children. Peripheral blood mononuclear cell (PBMC) HIV-1 DNA was quantified prior to and after 1 year of cART in 30 children, stratified by time of initiation (early, age <3 months, ET; late, age >3 months-2 years, LT). Pre-therapy PBMC HIV-1 DNA levels correlated with pre-therapy plasma HIV-1 levels (r = 0.59, p<0.001), remaining statistically significant (p = 0.002) after adjustment for prior perinatal antiretroviral exposure and age at cART initiation. PBMC HIV-1 DNA declined significantly after 1 year of cART (Overall: -0.91±0.08 log₁₀ copies per million PBMC, p<0.001; ET: -1.04±0.11 log₁₀ DNA copies per million PBMC, p<0.001; LT: -0.74 ±0.13 log₁₀ DNA copies per million PBMC, p<0.001) but rates of decline did not differ significantly between ET and LT. HIV-1 replication exposure over the first 12 months of cART, estimated as area-under-the-curve (AUC) of circulating plasma HIV-1 RNA levels, was significantly associated with PBMC HIV-1 DNA at one year (r = 0.51, p = 0.004). In 21 children with sustained virologic suppression after 1 year of cART, PBMC HIV-1 DNA levels continued to decline between years 1 and 4 (slope -0.21 log₁₀ DNA copies per million PBMC per year); decline slopes did not differ significantly between ET and LT. PBMC HIV-1 DNA levels at 1 year and 4 years of cART correlated with age at cART initiation (1 year: p = 0.04; 4 years: p = 0.03) and age at virologic control (1 and 4 years, p = 0.02). Altogether, these data indicate that reducing exposure to HIV-1 replication and younger age at cART initiation are associated with lower HIV-1 DNA levels at and after one year of age, supporting the concept that HIV-1 diagnosis and cART initiation in infants should occur as early as possible.     

Antioxidant Defenses Influence HIV-1 Replication and Associated Cytopathic Effects

HIV-infected cells often exhibit reduced levels of antioxidant enzymes and thiols. To investigate the role of cellular antioxidant defenses in the progression of an acutely spreading HIV-1 infection, human Sup-T1 T cells were engineered to overexpress the selenium-dependent glutathione peroxidase, GSHPx-1. This enzyme represents a major cellular defense mechanism against toxicity associated with reactive oxygen species (ROS). T cells engineered to produce elevated GSHPx-1 activity displayed accelerated viral replication and associated cytopathic effects compared to control cells. Conversely, the inhibition of the synthesis of glutathione with buthione sulfoximine (BSO) resulted in the attenuation of viral replication in Sup-T1 cells. Similarly, exposure of human peripheral blood lymphocytes (PBLs) to low, nontoxic levels of BSO resulted in an approximately 80% decline in HIV-1 replication as indicated by Western blot analysis of viral proteins.     

Plasmacytoid Dendritic Cells Suppress HIV-1 Replication but Contribute to HIV-1 Induced Immunopathogenesis in Humanized Mice

The role of plasmacytoid dendritic cells (pDC) in human immunodeficiency virus type 1 (HIV-1) infection and pathogenesis remains unclear. HIV-1 infection in the humanized mouse model leads to persistent HIV-1 infection and immunopathogenesis, including type I interferons (IFN-I) induction, immune-activation and depletion of human leukocytes, including CD4 T cells. We developed a monoclonal antibody that specifically depletes human pDC in all lymphoid organs in humanized mice. When pDC were depleted prior to HIV-1 infection, the induction of IFN-I and interferon-stimulated genes (ISGs) were abolished during acute HIV-1 infection with either a highly pathogenic CCR5/CXCR4-dual tropic HIV-1 or a standard CCR5-tropic HIV-1 isolate. Consistent with the anti-viral role of IFN-I, HIV-1 replication was significantly up-regulated in pDC-depleted mice. Interestingly, the cell death induced by the highly pathogenic HIV-1 isolate was severely reduced in pDC-depleted mice. During chronic HIV-1 infection, depletion of pDC also severely reduced the induction of IFN-I and ISGs, associated with elevated HIV-1 replication. Surprisingly, HIV-1 induced depletion of human immune cells including T cells in lymphoid organs, but not the blood, was reduced in spite of the increased viral replication. The increased cell number in lymphoid organs was associated with a reduced level of HIV-induced cell death in human leukocytes including CD4 T cells. We conclude that pDC play opposing roles in suppressing HIV-1 replication and in promoting HIV-1 induced immunopathogenesis. These findings suggest that pDC-depletion and IFN-I blockade will provide novel strategies for treating those HIV-1 immune non-responsive patients with persistent immune activation despite effective anti-retrovirus treatment.     

HIV-1 Replication Benefits from the RNA Epitranscriptomic Code

The effects of RNA methylation on HIV-1 replication remain largely unknown. Recent studies have discovered new insights into the effect of 2′-O-methylation and 5-methylcytidine marks on the HIV-1 RNA genome. As so far, HIV-1 benefits from diverse RNA methylations through distinct mechanisms. In this review, we summarize the recent advances in this emerging field and discuss the role of RNA methylation writers and readers in HIV-1 infection, which may help to find alternative strategies to control HIV-1 infection.     

Unperturbed Posttranscriptional Regulatory Rev Protein Function and HIV-1 Replication in Astrocytes

Astrocytes protect neurons, but also evoke proinflammatory responses to injury and viral infections, including HIV. There is a prevailing notion that HIV-1 Rev protein function in astrocytes is perturbed, leading to restricted viral replication. In earlier studies, our finding of restricted viral entry into astrocytes led us to investigate whether there are any intracellular restrictions, including crippled Rev function, in astrocytes. Despite barely detectable levels of DDX3 (Rev-supporting RNA helicase) and TRBP (anti-PKR) in primary astrocytes compared to astrocytic cells, Rev function was unperturbed in wild-type, but not DDX3-ablated astrocytes. As in permissive cells, after HIV-1 entry bypass in astrocytes, viral-encoded Tat and Rev proteins had robust regulatory activities, leading to efficient viral replication. Productive HIV-1 infection in astrocytes persisted for several weeks. Our findings on HIV-1 entry bypass in astrocytes demonstrated that the intracellular environment is conducive to viral replication and that Tat and Rev functions are unperturbed.     

HIV-associated nephropathy: role of AT2R

AT₁R has been reported to play an important role in the progression of HIV-associated nephropathy (HIVAN); however, the effect of AT₂R has not been studied. Age and sex matched control (FVB/N) and Tg26 mice aged 4, 8, and 16 weeks were studied for renal tissue expression of AT₁R and AT₂R (Protocol A). Renal tissue mRNA expression of AT₂R was lower in Tg26 mice when compared with control mice. In Protocol B, Tg26 mice were treated with either saline, telmisartan (TEL, AT₁ blocker), PD123319 (PD, AT₂R blocker), or TEL + PD for two weeks. TEL-receiving Tg26 (TRTg) displayed less advanced glomerular and tubular lesions when compared with saline-receiving Tg26 (SRTg). TRTgs displayed enhanced renal tissue AT₂R expression when compared to SRTgs. Diminution of renal tissue AT₂R expression was associated with advanced renal lesions in SRTgs; whereas, upregulation of AT₂R expression in TRTgs was associated with attenuated renal lesions. PD-receiving Tg26 mice (PDRTg) did not show any alteration in the course of HIVAN; whereas, PD + TEL-receiving Tg26 (PD-TRTg) showed worsening of renal lesions when compared to TRTgs. Interestingly, plasma as well as renal tissues of Tg26 mice displayed several fold higher concentration of Ang III, a ligand of AT₂R.     

ADAR1 Facilitates HIV-1 Replication in Primary CD4+ T Cells

Unlike resting CD4⁺ T cells, activated CD4⁺T cells are highly susceptible to infection of human immunodeficiency virus 1 (HIV-1). HIV-1 infects T cells and macrophages without activating the nucleic acid sensors and the anti-viral type I interferon response. Adenosine deaminase acting on RNA 1 (ADAR1) is an RNA editing enzyme that displays antiviral activity against several RNA viruses. Mutations in ADAR1 cause the autoimmune disorder Aicardi-Goutieères syndrome (AGS). This disease is characterized by an inappropriate activation of the interferon-stimulated gene response. Here we show that HIV-1 replication, in ADAR1-deficient CD4⁺T lymphocytes from AGS patients, is blocked at the level of protein translation. Furthermore, viral protein synthesis block is accompanied by an activation of interferon-stimulated genes. RNA silencing of ADAR1 in Jurkat cells also inhibited HIV-1 protein synthesis. Our data support that HIV-1 requires ADAR1 for efficient replication in human CD4⁺T cells.