Role Of Human Immunodeficiency Virus Type 1 Research Articles

Targeting deoxyhypusine hydroxylase activity impairs cap-independent translation initiation driven by the 5'untranslated region of the HIV-1, HTLV-1, and MMTV mRNAs

Replication of the human immunodeficiency virus type 1 (HIV-1) is dependent on eIF5A hypusination. Hypusine is formed post-translationally on the eIF5A precursor by two consecutive enzymatic steps; a reversible reaction involving the enzyme deoxyhypusine synthase (DHS) and an irreversible step involving the enzyme deoxyhypusine hydroxylase (DOHH). In this study we explored the effect of inhibiting DOHH activity and therefore eIF5A hypusination, on HIV-1 gene expression. Results show that the expression of proteins from an HIV-1 molecular clone is reduced when DOHH activity is inhibited by Deferiprone (DFP) or Ciclopirox (CPX). Next we evaluated the requirement of DOHH activity for internal ribosome entry site (IRES)-mediated translation initiation driven by the 5'untranslated region (5′UTR) of the full length HIV-1 mRNA. Results show that HIV-1 IRES activity relies on DOHH protein concentration and enzymatic activity. Similar results were obtained for IRES-dependent translation initiation mediated by 5′UTR of the human T-cell lymphotropic virus type 1 (HTLV-1) and the mouse mammary tumor virus (MMTV) mRNAs. Interestingly, activity of the poliovirus IRES, was less sensitive to the targeting of DOHH suggesting that not all viral IRESs are equally dependent on the cellular concentration or the activity of DOHH. In summary we present evidence indicating that the cellular concentration of DOHH and its enzymatic activity play a role in HIV-1, HTLV-1 and MMTV IRES-mediated translation initiation.

Chemokine receptors and their interactors in HIV-1 replication: potential therapeutic targets

Chemokine receptors CXCR4 and CCR5 are co-receptors indispensable for human immunodeficiency virus type 1 (HIV-1) entry and subsequent infection in host cells. Antiretroviral therapies based on the viral proteins have been developed, and significant achievements have been made in the treatment of HIV/AIDS patients based on the HAART regimens. However, a lot of concerns are still present, the purge of latent viral reservoirs and cure of AIDS are currently impossible, and prophylactic vaccines are not yet available. Most recently, HIV-1 entry has been understood much more and targeting viral entry based on chemokine receptors represents an interesting prospective. In this research highlight, we review the role of HIV-1 co-receptors-interacting proteins during chemokine receptor signal activation and assembly, as well as present new results about how they can regulate the replication of the virus.

Activation of DC-SIGN Promoter and Common Signaling Pathways Between HIV-1 5′LTR and DC-SIGN

Objective: To explore whether expression of dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) and reactivation of human immunodeficiency virus type 1 (HIV-1) provirus in dendritic cells (DCs) occur through similar or common signaling pathways. Methods: Phorbol 12-myristate 13-acetate (PMA)–differentiated THP-1 cells were used as the in vitro model of DCs. The activation of the DC-SIGN promoter and HIV-1 5′long-term repeat (LTR) sequence induced by interleukin 4 ( IL-4 ) in differentiated THP-1 cells was studied using luciferase reporter plasmids. The regulatory signaling pathways were identified using specific inhibitors, and the activity of the DC-SIGN promoter and HIV-1 5′LTR was detected. Results: HIV-1 5′LTR was activated by IL-4 –induced signaling pathways but much weaker than DC-SIGN promoter. IL-4 –induced activation of HIV-1 5′LTR was mainly through the nuclear factor kappa-light-chain-enhancer of activated B cells ( NF-κB) pathway, which was also involved in activation of the DC-SIGN promoter. The extracellular signal-regulated kinase (ERK) pathway, which was the main pathway for DC-SIGN promoter activation, also played an important role in HIV-1 5′LTR activation. Conclusion: Our study suggests that the activation of the DC-SIGN promoter and HIV-1 5′LTR may share NF-κB and ERK-signaling pathways. * HIV-1 : human immunodeficiency virus type 1; cDNA : complementary DNA; DCs : dendritic cells; LTR : long-term repeat; NF-κB : nuclear factor-kappa B; Sp-1 : stimulatory protein 1; AP-1 : activator protein 1; NF-AT : nuclear factor of activated T cells; DC-SIGN : dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin; gp120 : glycoprotein 120; PMA : phorbol 12-myristate 13-acetate; MEK1/2 : mitogen-activated protein kinase/extracellular signal-regulated kinase; PBMCs : peripheral blood mononuclear cells; PCR : polymerase chain reaction; CCR5 : CC-chemokine receptor-5; dNTP : deoxyribonucleotide triphosphate; RPMI : Royal Park Memorial Institute; pRL-TK : promoter-Renilla luciferase reporter plasmid; ERK : extracellular signal-regulated kinase; JAK : Janus activated kinase; STAT : signal transducers and activators of transcription; Lyf-1 : lymphocyte transcription factor 1; Sp-1 : specificity protein 1; TLR8 : toll-like receptor 8; IL-1β : interleukin 1–beta; IL-6 : interleukin 6; TNF-α : tumor necrosis factor–alpha; IL-4 : interleukin 4

Mapping determinants in the gp41 CT of HIV‐1 Env that mediate resistance to antibody neutralization during cell‐cell infection.

Human Immunodeficiency Virus Type 1 (HIV‐1) uses its surface envelope glycoprotein (Env) to mediate entry into CD4+ T‐cells. During direct T‐cell to T‐cell infection mediated by the virological synapse (VS), Env initiates cell‐cell adhesion in a CD4 dependent manner. Entry of viral capsids into a target cell resulting from this fusion can be blocked by neutralizing antibodies. However VS‐mediated infection is more resistant to neutralization compared to cell‐free infection. The transmembrane region of Env, gp41 has a cytoplasmic tail (CT) made up of 151 amino acids that has been shown to aid in the fusion process and play a role in HIV‐1's resistance to neutralizing antibodies during cell‐cell infection by regulating the exposure of neutralizing epitopes on the cell surface. Complete truncation of the gp41 CT makes VS‐mediated infection more sensitive to antibody neutralization. We hypothesize that specific structural features in the CT regulate HIV‐1 neutralization and certain amino acids correspond to the exposure of neutralizing epitopes. To map these putative conformation altering motifs, we constructed a series of C‐terminal truncations in the gp41 CT. Infectivity and neutralization assays are being performed to evaluate how these truncations affect HIV‐1's infectivity and its resistance to neutralizing antibodies during cell free and cell‐cell infection.

The Scaffolding Protein Dlg1 Is a Negative Regulator of Cell-Free Virus Infectivity but Not of Cell-to-Cell HIV-1 Transmission in T Cells

BackgroundCell-to-cell virus transmission of Human immunodeficiency virus type-1 (HIV-1) is predominantly mediated by cellular structures such as the virological synapse (VS). The VS formed between an HIV-1-infected T cell and a target T cell shares features with the immunological synapse (IS). We have previously identified the human homologue of the Drosophila Discs Large (Dlg1) protein as a new cellular partner for the HIV-1 Gag protein and a negative regulator of HIV-1 infectivity. Dlg1, a scaffolding protein plays a key role in clustering protein complexes in the plasma membrane at cellular contacts. It is implicated in IS formation and T cell signaling, but its role in HIV-1 cell-to-cell transmission was not studied before.Methodology/Principal FindingsKinetics of HIV-1 infection in Dlg1-depleted Jurkat T cells show that Dlg1 modulates the replication of HIV-1. Single-cycle infectivity tests show that this modulation does not take place during early steps of the HIV-1 life cycle. Immunofluorescence studies of Dlg1-depleted Jurkat T cells show that while Dlg1 depletion affects IS formation, it does not affect HIV-1-induced VS formation. Co-culture assays and quantitative cell-to-cell HIV-1 transfer analyses show that Dlg1 depletion does not modify transfer of HIV-1 material from infected to target T cells, or HIV-1 transmission leading to productive infection via cell contact. Dlg1 depletion results in increased virus yield and infectivity of the viral particles produced. Particles with increased infectivity present an increase in their cholesterol content and during the first hours of T cell infection these particles induce higher accumulation of total HIV-1 DNA.ConclusionDespite its role in the IS formation, Dlg1 does not affect the VS and cell-to-cell spread of HIV-1, but plays a role in HIV-1 cell-free virus transmission. We propose that the effect of Dlg1 on HIV-1 infectivity is at the stage of virus entry.

The Human Endosomal Sorting Complex Required for Transport (ESCRT-I) and Its Role in HIV-1 Budding

Efficient human immunodeficiency virus type 1 (HIV-1) budding requires an interaction between the PTAP late domain in the viral p6(Gag) protein and the cellular protein TSG101. In yeast, Vps23p/TSG101 binds both Vps28p and Vps37p to form the soluble ESCRT-I complex, which functions in sorting ubiquitylated protein cargoes into multivesicular bodies. Human cells also contain ESCRT-I, but the VPS37 component(s) have not been identified. Bioinformatics and yeast two-hybrid screening methods were therefore used to identify four novel human proteins (VPS37A-D) that share weak but significant sequence similarity with yeast Vps37p and to demonstrate that VPS37A and VPS37B bind TSG101. Detailed studies produced four lines of evidence that human VPS37B is a Vps37p ortholog. 1) TSG101 bound to several different sites on VPS37B, including a putative coiled-coil region and a PTAP motif. 2) TSG101 and VPS28 co-immunoprecipitated with VPS37B-FLAG, and the three proteins comigrated together in soluble complexes of the correct size for human ESCRT-I ( approximately 350 kDa). 3) Like TGS101, VPS37B became trapped on aberrant endosomal compartments in the presence of VPS4A proteins lacking ATPase activity. 4) Finally, VPS37B could recruit TSG101/ESCRT-I activity and thereby rescue the budding of both mutant Gag particles and HIV-1 viruses lacking native late domains. Further studies of ESCRT-I revealed that TSG101 mutations that inhibited PTAP or VPS28 binding blocked HIV-1 budding. Taken together, these experiments define new components of the human ESCRT-I complex and characterize several TSG101 protein/protein interactions required for HIV-1 budding and infectivity.

Some aspects of the pathogenesis of HIV-1-associated Kaposi's sarcoma.

Kaposi's sarcoma (KS) is a very rare tumor except after human immunodeficiency virus type 1 (HIV-1) infection when it becomes common. Most investigators assume that the role of HIV-1 is passive, i.e., via inducing immune deficiency, thereby enhancing cancer development, and specifically, in the case of human herpesvirus 8 (KSHV) by enhancing HHV-8 replication. We suggest that the role of HIV-1 is more active in the disease process by at least two events: 1) promoting an increase in inflammatory cytokines, which through sustained release influences early stage KS by inciting local microinflammatory responses, and 2) by the Tat protein that effects growth of the inflammatory cells. Cultures of all activated endothelial spindle cells, whether hyperplastic or neoplastic, are negative for HHV-8; transmission of HHV-8 does not induce cell growth or transformation; monkeys immune suppressed by simian immunodeficiency virus infection and infected also with HHV-8 do not develop KS; polymerase chain reaction analysis of blood cells shows HHV-8 sequences in monocytes and B cells (about 20% of normal donors in Maryland); M. Starzl showed that early KS has few cells (mostly macrophage) positive for HHV-8, increasing and present in endothelial cells only late in the disease; no increase in HHV-8 has been found in association with progressive immune deficiency; and recent studies in Gambia by others showed that HHV-8 is a very common infection, and though HHV-2 is known to be relatively common, HIV-1 is unusual and so is KS. Collectively, these findings lead me to conclude that there is little evidence that HHV-8 is a transforming virus as has been repeatedly suggested and that its role in KS is more likely to be indirect (like HIV-1), perhaps necessary but hardly likely to be sufficient for KS development.

Increased incidence of cancer among homosexual men, New York City and San Francisco, 1978-1990.

Several studies have shown that human immunodeficiency virus type 1 (HIV-1) is associated with an increase in the incidence of Kaposi's sarcoma and non-Hodgkin's lymphoma among homosexual men. The role of HIV-1 in increasing the incidence of other malignancies is more controversial. The incidence of non-Kaposi's sarcoma cancer was examined from 1978 to 1990 among 15,565 homosexual men who participated in studies of hepatitis B virus infection in the late 1970s in New York City, New York, and San Francisco, California. The standardized incidence ratio (SIR) for all cancers was 1.6 (95% confidence interval (CI) 1.4-1.8). Excesses were observed for non-Hodgkin's lymphoma (SIR = 12.7; 95% CI 11.0-14.6). Hodgkin's disease (SIR = 2.5; 95% CI 1.5-3.9), and anal cancer (SIR = 24.2 95% CI 13.5-39.9). As seen with non-Hodgkin's lymphoma, a cancer known to be associated with HIV-1. Hodgkin's disease incidence was significantly higher in more recent years compared with earlier years. No cases of Hodgkin's disease were found among HIV-1 antibody-negative men, and Hodgkin's disease was diagnosed near the time of initial acquired immunodeficiency syndrome diagnoses. Anal cancer incidence did not correlate with HIV-1 antibody status and did not tend to occur near the time of AIDS diagnoses. This study confirms the association of non-Hodgkin's lymphoma with HIV-1 infect on and suggests an association between Hodgkin's disease and HIV-1 infection. An excess in anal cancer was observed but did not appear to be associated with HIV-1 infection.