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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1996 was a watershed year for AIDS research, largely due to the introduction of protease inhibitors. Researchers also gained crucial new knowledge about the mechanism by which HIV infects CD4 cells, creating an opportunity for deciphering the disease process. Important discoveries made throughout the year by NIAID researchers are briefly described in a chronology of significant findings. Research included a study of individuals who remain HIV-negative in spite of repeated high-risk behavior, the discovery of co-receptors, the role of CCR-5 in protecting against AIDS, and studies on chemokine receptors.
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PMID:1996--a very good year for pathogenesis research. 1136 75

Presentations at the Fifth Conference on Retroviruses and Opportunistic Infections focused on new and novel HIV treatments. Four new agents in advanced testing are described: abacavir (1592), efavirenz (DMP-266), adefovir dipivoxil (bis-POM PMEA), and amprenavir (141W94). Other new drugs are being developed; however, the drugs are not as far along in the testing and approval process. The new drugs include integrase inhibitors, zinc finger inhibitors, cyclams and bycyclams, fusion inhibitors, and CKR-5 gene therapy. A summary of each drug is provided.
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PMID:Novel approaches for the treatment of HIV. 1136 50

This article reviews the cell and molecular biology of human immunodeficiency virus (HIV), emphasizing the features that lead to opportunistic infection by organisms such as mycobacteria. Mycobacteria, especially M. avium complex and M. tuberculosis infections, are closely associated with HIV disease. HIV is a very small retrovirus and its high mutation rate leads to extremely variable viral populations, both within and between individuals. It is coated with glycoprotein 120 (gp120), which it uses to bind to and infect a range of CD4+ leukocytes, depending on the co-receptor specificity. T cell-tropic HIV strains tend to use the CXCR-4 chemokine receptor, while macrophage-tropic strains tend to use the CCR-5 chemokine receptor. Immunosuppression is induced in a number of ways. As well as frank depletion of virus-infected T cells, antigen-specific T cell clones can be selectively deleted by mechanisms such as defective antigen presentation by HIV-infected macrophages (activation-induced cell death). Changes in cytokine production in HIV infection are also proposed. All this leads to falling T cell counts, B cell dysregulation and macrophage dysfunction. Opportunistic infections exploit this immunosuppressed environment. Certain infections are prevalent, reflecting factors such as environmental exposure to pathogens, poor mucosal defences and subcellular interactions between HIV and, e.g. viral or mycobacterial infections. Opportunistic infection exacerbates immune destruction by HIV, producing a vicious cycle that is ultimately fatal.
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PMID:The biology of HIV infection. 1149 53

The discovery that chemokines and their receptors (in particular CXCR-4 and CCR-5) play a role in HIV infection challenges traditional views on the pathogenesis of HIV infection in man and identifies new potential targets for therapeutic intervention. Several groups as well as our pilot study have found that increased numbers of CCR-5 positive macrophage/microglia correlate with disease severity in brains of patients with AIDS. Among HIV-related disorders, vacuolar myelopathy (VM) is the most common spinal cord disorder in patients with AIDS. The purpose of this study was to investigate the possible relationship between the expression of CCR-5/CXCR-4 and spinal cord pathology in patients with AIDS. Thirty-four spinal cords (forming two groups: without and with VM) of patients with AIDS and 6 HIV-1-negative controls were investigated by routine histological examination and immunohistochemistry. Elevated expression of CXCR-4 was found in most AIDS cases with/without neuropathological disorders (8/17 and 13/16, respectively). No CCR-5 expression was detected in HIV-1-negative controls. Among 34 cases with AIDS, expression of CCR-5 was detected in 1/16 HIV-1-positive normal spinal cords and 5/18 with VM. Despite the lack of statistical significance between the two groups (P=0.1019), our results suggest that CCR-5/CXCR-4 are present in spinal cord of patients with AIDS and that CCR-5 is more frequently found in association with VM.
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PMID:Expression of CCR-5/CXCR-4 in spinal cord of patients with AIDS. 1156 33

In this paper we addressed the expression of the HIV co-receptors CXCR-4 and CCR-5 in human thymocytes by phenotypic, molecular and functional approaches. Cytofluorimetric analysis disclosed that CXCR-4 was constitutively expressed by freshly isolated thymocytes (~10 000 molecules/cell in about 30% of thymocytes); the receptor was endowed with functional activity, as it mediated polarization, migration and intracellular Ca2+ increase in response to its ligand, SDF-1. On the contrary, CCR-5 expression in freshly isolated thymocytes was significantly lower (<4000 molecules/cell in less than 5% of the cells), and no functional response to CCR-5 agonists could be documented. Northern blot analysis of freshly isolated thymocytes showed high CXCR-4 mRNA levels, whereas the message for CCR-5 was barely detectable. On the other hand, a modest increase in the expression of CCR-5 was associated with in vitro thymocyte stimulation, and CCR-5 density at the cell surface attained CXCR-4 figures in most cases. None the less, no functional response to CCR-5 agonists could be documented in in vitro stimulated thymocytes. In vitro infection of thymocytes by CAT-expressing recombinant HIV bearing the envelope glycoproteins from different isolates showed that T-tropic strains, which use CXCR-4 as a co-receptor, were more efficient in infecting thymocytes than M-tropic strains, which preferentially use CCR-5. Altogether, these data indicate that expression of the major co-receptors involved in infection by M-tropic HIV strains is very poor in human thymocytes, and would suggest that thymocyte infection by M-tropic HIV strains may be a rare event in vivo.
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PMID:Expression and functional activity of CXCR-4 and CCR-5 chemokine receptors in human thymocytes. 1187 57

Intrakines, modified intracellular chemokines, offer a novel strategy to prevent cellular entry of HIV-1 by blocking the surface expression of HIV-1 co-receptors. To investigate potential clinical applications of the RANTES-intrakine, we explored the use of HIV-1-based lentiviral vectors for therapeutic gene transfer into T-lymphocytes. RANTES-intrakine genes can be efficiently transduced into primary human T-lymphocytes by lentiviral vectors, especially when human T-lymphocytes were stimulated with CD3 and CD28 antibodies. The transduced T cells showed decreased surface expression of the chemokine receptor CCR-5, as well as CCR-1 and CCR-3. This lentivirus-mediated approach to intrakine gene transfer protected human T-lymphocytes from infection by a variety of R5-tropic HIV-1 strains. A quantitative real-time PCR assay, developed to monitor cells for HIV entry and persistence, revealed persistent low copy numbers of proviral HIV DNA in RANTES intrakine-transduced T-lymphocytes during 3-week culture, suggesting that viruses produced from infected untransduced cell populations were unable to infect the surrounding transduced T-lymphocytes. We conclude that targeting HIV-1 co-receptors to block virus entry with lentiviral vectors is an attractive approach to the control of HIV-1 infection.
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PMID:Lentiviral transduction of human T-lymphocytes with a RANTES intrakine inhibits human immunodeficiency virus type 1 infection. 1208 Mar 83

Effect of CCR-5 delta 32 heterozygosity in immunological protection was studied by a lymphocyte proliferation assay. Twenty of 86 HIV+ and eight of 32 healthy subjects showed heterozygous mutation (wt/mut) of the CCR-5 gene. Lymphocyte proliferation to pokeweed mitogen was found significantly higher (P < 0.005) in wt/mut versus wild type homozygous (wt/wt) HIV+ subjects in groups with CD4 > 500 and CD4 < 200 cell/ micro L. Phytohaemagglutinin induced stronger proliferation of cells from wt/mut HIV+ subjects with CD4 < 200 cell/ micro L (P = 0.03). Decline of lymphocyte response was more significant among wt/wt groups with different CD4+ cell counts than that between wt/mut groups to both mitogens. Reduced number of CCR-5 receptors on CD4+ cells may decrease the ability of HIV-1 envelope glycoproteins to transduce intracellular signals through CCR-5. Mutation in CCR-5 gene seems to have a benefit in preventing T-cells from HIV envelope-mediated immunopathogenic effects and maintain a relatively normal response to lectins.
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PMID:A comparison of the lymphoproliferative capacity of pokeweed mitogen (PWM) and phytohaemagglutinin (PHA) in CCR-5 wild-type and heterozygous HIV-infected and uninfected subjects. 1239 39

Understanding the origin, distribution, and evolving dominance of HIV-1 subtype C strains is an important component in the design and evaluation of a globally effective AIDS vaccine. To better understand subtype C viruses, we constructed complete molecular clones of primary, CCR-5-using isolates from South Africa and analyzed the molecular phylogenies of these clones using best fitting evolutionary substitution models. Analyses were performed on three full-length sequences, and on the individual genes. All clones were nonrecombinant, and although two of three had open reading frames and intact splice sites, they were not infectious. At the genomic level, the models demonstrated the increasing variability of subtype C in South Africa. At the subgenomic level, they revealed marked differences in the evolutionary patterns of individual genes, a finding that suggests that the genes are under different selective pressures and constraints. These data underscore the dynamic nature of the subtype C epidemic and emphasize the need for continuous monitoring of local strains.
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PMID:Novel evolutionary analyses of full-length HIV type 1 subtype C molecular clones from Cape Town, South Africa. 1248 21

Monocytes, macrophages and dendritic cells play an important role in the initial infection and contribute to its pathogenesis throughout the course of infection. Myeloid cells express CD4 and chemokine receptors known for HIV-1 fusion and entry. The beta-chemokine receptor, CCR5, is the major co-receptor in conjunction with CD4 for macrophage (M)-tropic or (R5) isolates of HIV-1, whereas the alpha-chemokine receptor, CXCR4, facilitates entry of T-tropic or (X4) HIV-1 strains. Cells of myeloid lineage may be infected predominantly with R5- strains, although infection with dual-tropic isolates of HIV-1 (exhibiting the capacity to use CCR-5 and/or CXCR-4 for entry) or some strains of X4- isolates has also been reported. The expression of chemokine receptors, HIV-1 infection and replication is under continuous regulation by a complex cytokine network produced by a variety of cells. The effects of cytokines/chemokines on HIV-1 replication in cells of myeloid lineage can be inhibitory (IFN-alpha, IFN-beta, IFN-gamma, GM-CSF, IL-10, IL-13 and IL-16 and beta-chemokines), stimulatory (M-CSF, TNF-alpha, TNF-beta, IL-1, IL-6) or bifunction al, that is both inhibitory and stimulatory (IL-4). This review focuses on the overall expression of chemokine receptors on cells of myeloid lineage and considers the mechanisms of entry of R5-, X4- and dual-tropic strains of HIV-1 into these cells. The effects of cytokines/chemokines on viral entry and productive HIV-1 infection are also reviewed.
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PMID:The influence of cytokines, chemokines and their receptors on HIV-1 replication in monocytes and macrophages. 1251 61

HIV-1 vertical transmission is thought to mainly take place by virus crossing the placental barrier. However, the mechanism by which HIV-1-infects placental cells remains to be elucidated. We have found that purified cytotrophoblasts as well as trophoblastic cell lines are susceptible to infection by different HIV-1 isolates as detected by DNA-PCR and release of infectious virus, although with very low efficiency. Purified trophoblast or trophoblastic cell lines express low levels of chemokine receptors CCR-5 and CXCR-4 but not CD4 on the cell surface. To test if those molecules were used as receptors for HIV-1 infection, placental cells were pretreated with antibodies to CD4, CC-chemokines, C-X-C chemokines. None of those treatments inhibited HIV-1 infection. In contrast, we have found that HIV-1 infection of placental cells was increased in cocultures of infected T-cell blasts and placental cells. More interestingly, antibodies to beta(2) integrins and to LFA-1 were able to significantly block infection of placental cells. Cell surface expression of ICAM-1, an adhesion molecule involved in attachment of leukocytes to placenta, was upregulated in HIV-1-infected placental cells. Placental cells were able to transfer HIV-1 infection to T-cell blasts. This transmission required cell to cell contact and was also inhibited by anti-LFA-1 antibodies. In summary our results suggest that placental trophoblast could be infected by HIV-1 by a mechanism involving T cell to placental contact. Moreover, placental infection enhanced ICAM-1 expression and leukocyte adherence, an event which was required to transfer HIV-1 infection to T cells. This provides an explanation of the virus passing through the placental barrier during in utero HIV-1 vertical transmission.
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PMID:Transmission of HIV-1 infection between trophoblast placental cells and T-cells take place via an LFA-1-mediated cell to cell contact. 1266 96


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