Biomedical subjects

A Garzino-Demo

Publications and source records attributed to A Garzino-Demo.

14 recordsLinked to original sources

PubMed1998

The leukotriene B4 receptor functions as a novel type of coreceptor mediating entry of primary HIV-1 isolates into CD4-positive cells.

The recently cloned human chemoattractant receptor-like (CMKRL)1, which is expressed in vivo in CD4-positive immune cells, has structural homology with the two chemokine receptors C-C chemokine receptor (CCR)5 and C-X-C chemokine receptor (CXCR)4, which serve as the major coreceptors necessary for fusion of the HIV-1 envelope with target cells. In view of the structural similarity, CMKRL1 was tested for its possible function as another HIV-1 coreceptor after stable expression in murine fibroblasts bearing the human CD4 receptor. The cells were infected with 10 primary clinical isolates of HIV-1, and entry was monitored by semiquantitative PCR of viral DNA. The efficiency of the entry was compared with the entry taking place in CD4-positive cells expressing either CCR5 or CXCR4. Seven of the isolates used CMKRL1 for viral entry; they were mainly of the syncytium-inducing phenotype and also used CXCR4. Entry efficiency was higher with CMKRL1 than with CXCR4 for more than half of these isolates. Three of the ten isolates did not use CMKRL1; instead, entry was mediated by both CCR5 and CXCR4. The experiments thus indicate that CMKRL1 functions as a coreceptor for the entry of HIV-1 into CD4-positive cells. In the course of this study, leukotriene B4 was shown to be the natural ligand for this receptor (now designated BLTR), which therefore represents a novel type of HIV-1 coreceptor along with the previously identified chemokine receptors. BLTR belongs to the same general chemoattractant receptor family as the chemokine receptors but is structurally more distant from them than are any of the previously described HIV-1 coreceptors.

3T3 Cells↗

PubMed1998

Induction of monocyte chemoattractant protein-1 in HIV-1 Tat-stimulated astrocytes and elevation in AIDS dementia.

Activated monocytes release a number of substances, including inflammatory cytokines and eicosanoids, that are highly toxic to cells of the central nervous system. Because monocytic infiltration of the central nervous system closely correlates with HIV-1-associated dementia, it has been suggested that monocyte-derived toxins mediate nervous system damage. In the present study, we show that the HIV-1 transactivator protein Tat significantly increases astrocytic expression and release of monocyte chemoattractant protein-1 (MCP-1). Astrocytic release of beta-chemokines, which are relatively less selective for monocytes, including RANTES, macrophage inflammatory protein-1alpha, and macrophage inflammatory protein-1beta, was not observed. We also show that MCP-1 is expressed in the brains of patients with HIV-1-associated dementia and that, of the beta-chemokines tested, only MCP-1 could be detected in the cerebrospinal fluid of patients with this condition. Together, these data provide a potential link between the presence of HIV-1 in the brain and the monocytic infiltration that may substantially contribute to dementia.

AIDS Dementia Complex↗

PubMed1998

Chemokine receptors and chemokines in HIV infection.

Suppression of HIV by chemokines represents a special case in virology and immunology where soluble molecules other than antibodies inhibit infection by a specific virus. The basis for this inhibition is that HIV has evolved to use certain chemokine receptors as "coreceptors" for entry into host cells. Human genotypes that reduce or prevent coreceptor expression are strongly associated with protection against infection and slower disease progression. We suggest that local production of certain chemokines can produce a similar modulation of coreceptor expression, and mounting evidence indicates that chemokine release is a major determinant of protection from HIV infection. Here we review this evidence and explore future avenues for investigating the role of chemokines in controlling HIV infection.

Chemokines↗

PubMed1998

Beta-chemokines and protection from HIV type 1 disease.

A small revolution has occurred in the field of AIDS research. A number of chemokines, most of which belong to the CC or beta family, were found by us and others to inhibit HIV infection potently and specifically. The mechanism of such inhibition was shown to be at the level of receptor binding, as these chemokines are binding to receptors that mediate HIV infection. Therefore, chemokines effectively block entry of HIV. Although chemokines have a natural function as chemoattractants, it is intriguing to think that in crossing their path with the virus, they constitute the first example of a naturally occurring soluble molecule, other than antibodies, that can specifically prevent infection. Thus, chemokines could play a role in protective immunity against HIV infection together with other classic correlates, such as neutralizing antibodies and cytotoxic T cells, and some clinical studies suggest that this is indeed the case. Here we review and analyze some of the basic and clinical science that led to the elucidation of the role of chemokines and their receptor in protection from HIV infection.

Animals↗

PubMed1997

C-C chemokine RANTES and HIV long terminal repeat-driven gene expression.

The C-C chemokines RANTES, MIP-1alpha, and MIP-1beta have been characterized as constituents of an HIV- and SIV-suppressive factor released by CD8+ cells. Furthermore, it has been demonstrated that chemokine receptors cooperate in HIV entry. However, these proteins are also known to have an effect on multiple intracellular signaling cascades that may affect the process of transcription. In the present study we demonstrate that treatment of CD4+ T cells with these chemokines or with cell supernatants from HTLV-I-immortalized CD8+ T cells results in significant reduction in the abundance of HIV-1-specific RNA as analyzed by Northern blot hybridization. To examine the possibility that such suppressive factors may inhibit HIV RNA transcription, we studied the effect of RANTES, the most effective HIV-suppressive chemokine, on basal and Tat-induced HIV-directed LTR expression of a reporter gene. Neither recombinant RANTES nor conditioned medium from CD8+ cells significantly altered HIV-1 LTR-directed chloramphenicol acetyltransferase expression in either transiently or stably transfected CD4+ T cell lines, either in the presence or in the absence of Tat. These results suggest that C-C chemokines do not inhibit viral RNA transcription.

CD4-Positive T-Lymphocytes↗

PubMed1997

Inhibition of HIV-1 infection by the beta-chemokine MDC.

CD8(+) T lymphocytes from individuals infected with human immunodeficiency virus-type 1 (HIV-1) secrete a soluble activity that suppresses infection by HIV-1. A protein associated with this activity was purified from the culture supernatant of an immortalized CD8(+) T cell clone and identified as the beta-chemokine macrophage-derived chemokine (MDC). MDC suppressed infection of CD8(+) cell-depleted peripheral blood mononuclear cells by primary non-syncytium-inducing and syncytium-inducing isolates of HIV-1 and the T cell line-adapted isolate HIV-1IIIB. MDC was expressed in activated, but not resting, peripheral blood mononuclear cells and binds a receptor on activated primary T cells. These observations indicate that beta-chemokines are responsible for a major proportion of HIV-1-specific suppressor activity produced by primary T cells.

Amino Acid Sequence↗

PubMed1996

Enhancement of TAT-induced transactivation of the HIV-1 LTR by two genomic fragments of HHV-6.

Clinical and experimental observations suggest that human herpesvirus-6 (HHV-6), a T-lymphotropic herpesvirus, may act as a cofactor in the acquired immunodeficiency syndrome (AIDS). Moreover, a possible role of HHV-6 in the increased incidence and severity of cervical carcinoma in human immunodeficiency virus (HIV)-infected women was suggested by the recent observation that HHV-6 can infect cervical carcinoma cells, accelerating their tumorigenicity in vivo. Therefore, the ability of four HHV-6 genomic clones derived from HHV-6 to transactivate the long terminal repeat (LTR) of HIV-1 in two cervical carcinoma cell lines and in a T-lymphoid cell line was tested. Two HHV-6 clones, pZVH-14 and pZVB-70, which were previously shown to increase the expression of human papillomavirus (HPV)-transforming genes, were, per se, weak transactivators of the HIV-1 LTR. However, an increased effect occurred when these clones were combined with the HIV-1 transactivator TAT-1. No such effect was seen with two other HHV-6 clones used as controls. Analysis with HIV-1 LTR deletion mutants indicated that this enhancing effect requires the presence of elements contained in both the enhancer region and the TAT activation region (TAR) of HIV-1. This data may have implications for the potential role of HHV-6 in AIDS and AIDS-related cervical carcinoma.

Genes, tat↗

PubMed1996

The V3 domain of the HIV-1 gp120 envelope glycoprotein is critical for chemokine-mediated blockade of infection.

The ability of CD8 T cells derived from human immunodeficiency virus (HIV)-infected patients to produce soluble HIV-suppressive factor(s) (HIV-SF) has been suggested as an important mechanism of control of HIV infection in vivo. The C-C chemokines RANTES, MIP-1 alpha and MIP-1 beta were recently identified as the major components of the HIV-SF produced by both immortalized and primary patient CD8 T cells. Whereas they potently inhibit infection by primary and macrophage-tropic HIV-1 isolates, T-cell line-adapted viral strains tend to be insensitive to their suppressive effects. Consistent with this discrepancy, two distinct chemokine receptors, namely, CXCR4 (ref. 7) and CCR5 (ref. 8), were recently identified as potential co-receptors for T-cell line-adapted and macrophage-tropic HIV-1 isolates, respectively. Here, we demonstrate that the third hypervariable domain of the gp 120 envelope glycoprotein is a critical determinant of the susceptibility of HIV-1 to chemokines. Moreover, we show that RANTES, MIP-1 alpha and MIP-1 beta block the entry of HIV-1 into cells and that their antiviral activity is independent of pertussis toxin-sensitive signal transduction pathways mediated by chemokine receptors. The ability of the chemokines to block the early steps of HIV infection could be exploited to develop novel therapeutic approaches for AIDS.

Amino Acid Sequence↗

PubMed1995

Identification of RANTES, MIP-1 alpha, and MIP-1 beta as the major HIV-suppressive factors produced by CD8+ T cells.

Evidence suggests that CD8+ T lymphocytes are involved in the control of human immunodeficiency virus (HIV) infection in vivo, either by cytolytic mechanisms or by the release of HIV-suppressive factors (HIV-SF). The chemokines RANTES, MIP-1 alpha, and MIP-1 beta were identified as the major HIV-SF produced by CD8+ T cells. Two active proteins purified from the culture supernatant of an immortalized CD8+ T cell clone revealed sequence identity with human RANTES and MIP-1 alpha. RANTES, MIP-1 alpha, and MIP-1 beta were released by both immortalized and primary CD8+ T cells. HIV-SF activity produced by these cells was completely blocked by a combination of neutralizing antibodies against RANTES, MIP-1 alpha, and MIP-1 beta. Recombinant human RANTES, MIP-1 alpha, and MIP-1 beta induced a dose-dependent inhibition of different strains of HIV-1, HIV-2, and simian immunodeficiency virus (SIV). These data may have relevance for the prevention and therapy of AIDS.

Adult↗

PubMed1995

Infection of gamma/delta T lymphocytes by human herpesvirus 6: transcriptional induction of CD4 and susceptibility to HIV infection.

Human herpesvirus 6 (HHV-6), a T-lymphotropic human herpesvirus, is a potentially immunosuppressive agent that has been suggested to play a role as a cofactor in the natural history of human immunodeficiency virus (HIV) infection. We studied the interactions between HHV-6 and gamma/delta T lymphocytes, a subset of T cells involved in the protective immune response against specific microorganisms. Polyclonal gamma/delta T cell populations, purified from the peripheral blood of healthy adults and activated in vitro with phytohemagglutinin, were exposed to HHV-6, strain GS (subgroup A), at the approximate multiplicity of infection (MOI) of 1. Signs of virus replication were detected as early as 72 h after infection, as documented by immunofluorescence, electron microscopy, and transmission of extracellular virus. Progression of the infection was associated with the appearance of typical cytomorphological changes and, eventually, massive cell death. In contrast, no signs of infection or cytopathic effects were detected after exposure of gamma/delta T lymphocytes to HHV-7, a CD4+ T-lymphotropic virus closely related to HHV-6. Polyclonal gamma/delta T cells displayed cytolytic activity against both autologous and heterologous target cells infected with HHV-6 and maintained this activity for at least 72 h after infection with HHV-6, despite the high MOI used. As previously documented in mature CD8+ alpha/beta T cells and natural killer cells, HHV-6 infection induced gamma/delta T lymphocytes to express de novo CD4 messenger RNA and protein, as detected by reverse transcriptase-polymerase chain reaction and fluorocytometry, respectively. Whereas purified CD4- gamma/delta T cell populations were per se refractory to HIV infection, they became susceptible to productive infection by HIV-1, strain IIIB, after induction of CD4 expression by HHV-6. These results demonstrate that gamma/delta T cells can be directly targeted and killed by a herpesvirus and may have implications for the potential role of HHV-6 in AIDS.

Adult↗

PubMed1995

Human immunodeficiency virus type 2 (HIV-2): packaging signal and associated negative regulatory element.

Human immunodeficiency virus type 2 (HIV-2)-based retroviral vectors will have several desirable features as vehicles for gene therapy. These include target cell specificity, regulated expression, and attenuated cytopathicity. Such vectors require efficient packaging of RNA into retroviral particles which depends on a cis-acting sequence element called packaging signal or psi site. For most retroviruses, the principal part of this element is located between the major splice donor site and the gag initiator codon (AUG) in the leader sequence. The deletion of the corresponding region of HIV-2 did indeed cause a packaging defect; however, it did not abolish RNA encapsidation and viral infectivity. Additionally, deletions in this region resulted in an increase in intracellular viral RNA and extracellular p27 core antigen. However, only a fraction of the intracellular viral RNA was packaged into mature particles. These effects appeared to be sequence specific as deletion of the sequence elements upstream of the splice donor site did not result in increased viral RNA and proteins. A computer-assisted analysis of the leader sequence of viral RNA shows it to be rich in secondary structure, which was markedly altered in the deletion mutants. Thus, the leader sequence of HIV-2 between the splice donor site and the gag ATG has at least two regulatory functions: one positive, affecting encapsidation, and the other negative, regulating virus expression. Because there is only a limited sequence or structural homology between the corresponding region of HIV-1 and HIV-2, they are likely to differ in their pathways regulating packaging and gene expression.

Base Sequence↗

PubMed1994

CD4 is a critical component of the receptor for human herpesvirus 7: interference with human immunodeficiency virus.

In this study, we demonstrate that the glycoprotein CD4, a member of the immunoglobulin superfamily, is a critical component of the receptor for human herpesvirus 7 (HHV-7), a recently discovered T-lymphotropic human herpesvirus. A selective and progressive downregulation of the surface membrane expression of CD4 was observed in human CD4+ T cells in the course of HHV-7 infection. Various murine monoclonal antibodies to CD4 and the recombinant soluble form of human CD4 caused a dose-dependent inhibition of HHV-7 infection in primary CD4+ T lymphocytes. Moreover, radiolabeled HHV-7 specifically bound to cervical carcinoma cells (HeLa) expressing human CD4. A marked carcinoma cells (HeLa) expressing human CD4. A marked reciprocal interference was observed between HHV-7 and human immunodeficiency virus (HIV), the retrovirus that causes the acquired immunodeficiency syndrome and also uses CD4 as a receptor. Previous exposure of CD4+ T cells to HHV-7 dramatically interfered with infection by both primary and in vitro-passaged HIV-1 isolates. Reciprocally, persistent infection with HIV-1 or treatment with the soluble form of gp120, the CD4-binding envelope glycoprotein of HIV-1, rendered CD4+ T cells resistant to HHV-7 infection. These data indicate that CD4 is critically involved in the receptor mechanism for HHV-7. The antagonistic effect between HHV-7 and HIV could be exploited to devise therapeutic approaches to AIDS.

Binding, Competitive↗

PubMed1993

Infection of natural killer cells by human herpesvirus 6.

Natural killer (NK) cells are a functionally defined subset of non-T, non-B lymphocytes of bone marrow origin, which induce lysis of selected target cells, including neoplastic and virus-infected cells. The NK cell function provides an important mechanism of primary defence against viruses in vivo, as demonstrated by the occurrence of multiple herpesvirus infections in patients congenitally lacking NK cells. Here we show that functionally competent CD3- NK clones can be productively infected by human herpesvirus 6 (HHV-6), a T-lymphotropic DNA virus that may play a role in the acquired immunodeficiency syndrome (AIDS) and in the chronic fatigue syndrome, two disorders associated with a defective NK cell activity. The infection is cytopathic and induces de novo expression of CD4, an antigen not expressed within the NK lineage, thereby predisposing NK cells to infection by human immunodeficiency virus type 1 (HIV-1). These results provide evidence that a herpesvirus can directly target and kill NK cells, a potential strategy to suppress the natural anti-viral immunity of the host.

Adult↗

PubMed1993

Human immunodeficiency virus type 2 multiply spliced transcripts.

Viral transcripts, particularly those of the regulatory genes (e.g., rev) in lymphocytic cells chronically infected with human immunodeficiency virus type 2, consist of two types, differing in the structure of the leader sequence derived from the 5' long terminal repeat (LTR). Some transcripts undergo a specific splicing event within the 5' LTR, removing an intron consisting of a part of the R region whereas others do not. Because this spliced-out R region is a part of the trans-activation response element (TAR), it could influence trans-activator (Tat)-mediated trans-activation of viral gene expression. Moreover, this part of the R region is predicted to contain a stable secondary structure that could affect the efficiency of translation of the transcripts without this splicing. Thus, the 5' LTR splicing could have important consequences for virus replication, latency, and pathogenicity.

Base Sequence↗