Immunogenicity of a human immunodeficiency virus (HIV) polytope vaccine containing multiple HLA A2 HIV CD8(+) cytotoxic T-cell epitopes.
(17/3874)
Compelling evidence now suggests that alphabeta CD8 cytotoxic T lymphocytes (CTL) have an important role in preventing human immunodeficiency virus (HIV) infection and/or slowing progression to AIDS. Here, we describe an HIV type 1 CTL polyepitope, or polytope, vaccine comprising seven contiguous minimal HLA A2-restricted CD8 CTL epitopes conjoined in a single artificial construct. Epitope-specific CTL lines derived from HIV-infected individuals were able to recognize every epitope within the construct, and HLA A2-transgenic mice immunized with a recombinant virus vaccine coding for the HIV polytope also generated CTL specific for different epitopes. Each epitope in the polytope construct was therefore processed and presented, illustrating the feasibility of the polytope approach for HIV vaccine design. By simultaneously inducing CTL specific for different epitopes, an HIV polytope vaccine might generate activity against multiple challenge isolates and/or preempt the formation of CTL escape mutants. (+info)
Activation of Ste20 by Nef from human immunodeficiency virus induces cytoskeletal rearrangements and downstream effector functions in Saccharomyces cerevisiae.
(18/3874)
The negative factor (Nef) from human and simian immunodeficiency viruses is important for the pathogenesis of acquired immune deficiency syndrome. Among other targets, it activates the Nef-associated kinase, which is related to the p21-activated kinase. In this study, we demonstrate that Nef activates Ste20, the homolog of p21-activated kinase in Saccharomyces cerevisiae. Nef binds to the adaptor proteins Bem1 and Ste20 via its proline-rich (PXXP) and diarginine (RR) motifs, respectively. These interactions induce the mitogen-activated protein kinase and increase the rates of budding, sizes of cells, and patterns of mating projections. These effects of Nef depend on the small GTPase Cdc42 and guanine nucleotide exchange factor Cdc24. Thus, studies in S. cerevisiae identified specific interactions between Nef and cellular proteins and their associated signaling cascade. (+info)
HIV-HCV RNA loads and liver failure in coinfected patients with coagulopathy.
(19/3874)
BACKGROUND AND OBJECTIVE: The aim of this study was to measure contemporaneously HCV-RNA load, HIV-RNA load and CD4+ lymphocyte count in HCV/HIV coinfected patients with coagulopathy and to examine the relationship between these parameters and the liver failure. DESIGN AND METHODS: A cross-sectional study was performed on 54 patients with severe coagulopathy: 39 HCV/HIV coinfected and 15 HCV+/HIV- comparable for age and HCV exposure time. HCV-RNA and HIV-RNA load, CD4+ lymphocyte count, biochemical and ultrasonographic parameters were evaluated at the time of entry to the study. RESULTS: Mean HCV-RNA load was significantly higher in coinfected patients (643,872 717,687 copies/mL) than in HCV+/HIV- (mean 161,573 276,896 copies/mL) (p = 0.01). The 39 HCV/HIV coinfected patients had a mean HIV-RNA load of 205,913 456,311 copies/mL (range 4,000-2,500,000) and a mean CD4+ lymphocyte count of 206.5171/microL (range 5-693). Five of the 39 (12.8%) coinfected patients had liver failure. In these five patients the mean HCV-RNA load (770,200 996,426 copies/mL) was high but not significantly different from that in the 34 HCV+/HIV+ patients (623,496 682,239 copies/mL) without liver failure (p = 1.0). Coinfected patients with liver failure had a significantly higher HIV-RNA load (mean 764, 599 978,542 copies/mL) and lower CD4+ lymphocyte count (mean 52.655. 6/microL) than those observed in coinfected patients without liver failure (p = 0.007 and p = 0.03, respectively). A significant inverse correlation was found between CD4+ lymphocyte count and HIV-RNA load (r = -0.37, p = 0.01). INTERPRETATION AND CONCLUSIONS: HCV-RNA load is significantly higher in HIV+ than in HIV- patients with coagulopathy. Liver failure was found only in the HCV/HIV coinfected patients with severe immunodepression, expressed either by low CD4+ lymphocyte count or by high HIV-RNA load. (+info)
Vaccinia virus-bacteriophage T7 expression vector for complementation analysis of late gene processes.
(20/3874)
A vaccinia virus-bacteriophage T7 RNA polymerase hybrid transient expression vector has been developed for complementation analysis of late gene functions in vaccinia virus. The conditionally defective virus ts21 was modified to express the bacteriophage T7 RNA polymerase. The derived virus, vtsT7, was conditionally defective in viral late gene expression but produced high levels of a target protein under the control of a T7 promoter at non-permissive temperatures. The level of beta-galactosidase expression under the control of a T7 promoter was slightly lower in vtsT7 infections than those with the prototypical T7 RNA polymerase vector vTF7.3. However, the levels of expression for the human immunodeficiency virus envelope gene, a protein which undergoes post-translational modification, was slightly higher in vtsT7 infections, suggesting that some proteins may be expressed better in the absence of vaccinia virus late gene expression. Infections using vtsT7 at a low m.o.i. at 39 degrees C resulted in the accumulation of high molecular mass, non-linear replicative intermediates of vaccinia virus DNA replication and high levels of expression of a transfected gene proximal to a T7 promoter. The virus vtsT7 provides a means for the analysis of potential trans-acting factors participating in vaccinia virus late processes such as resolution of DNA replicative intermediates. (+info)
HIV: a new role for Nef in the spread of HIV.
(21/3874)
The HIV Nef protein downregulates the cell-surface expression of the HIV receptor glycoprotein CD4, but the significance of this event has remained obscure. Recent data suggest that Nef reduces cell-surface CD4 to promote the efficient spread of the virus. (+info)
T-cell induced pathogenesis in HIV: bystander effects and latent infection.
(22/3874)
The progress of HIV is accompanied by the infection and decline of the population of CD4+ cells. This reduction in cells results from both cytolytic influences of the virus and virus-specific cytotoxic T-cell (CTL) responses. We seek to characterize the extent of CD4+ reduction caused by HIV-specific CTLs at equilibrium. Here we show that intermediate levels of cytotoxic killing of infected cells can be inferior to both strong and weak or absent immune responses. We further show that the deleterious effects of the CTL response are made worse by a slow immune response. Bystander effects in which uninfected cells are thought to be eliminated by non-specific CTL activation lead to small or negligible reductions in uninfected CD4+ cells. Latently infected cells containing pro-viral DNA and which become activated at a constant rate ensure that the immune response is more effective for a larger range of CTL activities and reduces T-cell associated pathology. (+info)
Induction of phosphorylation and intracellular association of CC chemokine receptor 5 and focal adhesion kinase in primary human CD4+ T cells by macrophage-tropic HIV envelope.
(23/3874)
Binding of HIV-1 envelope glycoproteins to the surface of a CD4+ cell transduces intracellular signals through the primary envelope receptor, CD4, and/or the envelope coreceptor, a seven-transmembrane chemokine receptor. Macrophage-tropic strains of HIV-1 preferentially use CCR5 as an entry coreceptor, whereas T cell-tropic strains use CXC chemokine receptor-4 for entry. Intracellular signals transduced by HIV-1 envelope may have immunopathogenic consequences, including anergy, syncytium formation, apoptosis, and inappropriate cell trafficking. We demonstrate here that a recombinant envelope protein derived from an M-tropic isolate of HIV-1 can transduce CD4-dependent as well as CCR5-dependent intracellular signals in primary human CD4+ T cells. Novel HIV-induced intracellular signals that were identified include tyrosine phosphorylation of focal adhesion kinase (FAK) and CCR5, which are involved in cell adhesion and chemotaxis, respectively. HIV envelope-induced cellular association of FAK and CCR5 was also demonstrated, suggesting that ligation of CD4 and CCR5 leads to the formation of an activation complex composed of FAK and CCR5. Activation of this signaling pathway by HIV-1 envelope may be an important pathogenic mechanism of dysregulated cellular activation and trafficking during HIV infection. (+info)
Nuclear c-Abl is a COOH-terminal repeated domain (CTD)-tyrosine (CTD)-tyrosine kinase-specific for the mammalian RNA polymerase II: possible role in transcription elongation.
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The c-Abl tyrosine kinase has been shown to interact with the COOH-terminal repeated domain (CTD) of mammalian RNA polymerase II and can phosphorylate the tyrosine residues in the CTD. Interestingly, the Drosophila or the yeast CTD were not efficiently phosphorylated by the mammalian c-Abl. This species-specificity was found to be determined by the extreme COOH-terminal CTD sequences that are not conserved through evolution. In vitro, COOH-terminal-truncated CTD could neither bind to, nor be phosphorylated by, c-Abl. In vivo, coexpression of a full length CTD prevents c-Abl from inducing the tyrosine phosphorylation of endogenous RNA polymerase II, and such inhibitory effect was not observed with the coexpression of COOH-terminal-truncated CTD. Serine/threonine phosphorylation of the CTD has been linked to the regulation of transcription elongation. Transcription from the human immunodeficiency virus type 1 (HIV-1) promoter requires CTD-phosphorylation, which is stimulated by the viral Tat protein through the recruitment of cellular Ser/Thr CTD kinases. In transient cotransfection experiments, the c-Abl kinase was found to activate the HIV promoter in the absence of Tat. The activation of the HIV promoter required the nuclear localization of c-Abl and could be correlated with increased tyrosine phosphorylation of RNA polymerase II. These observations suggest that tyrosine phosphorylation of the CTD may be functionally equivalent to its serine/threonine phosphorylation in stimulating transcription elongation. (+info)