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Query: UMLS:C0021311 (Infection)
 38,178 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The human immunodeficiency virus type 2 (HIV-2)-related isolate, referred to as HIV-2 EHO, has been isolated from an Ivory Coast patient with acquired immunodeficiency syndrome (AIDS). Infection of CD4 expressing cells with this highly infectious virus mediates a cytopathic effect characterized by single-cell killing as a consequence of apoptosis. Nucleotide sequence analysis of the HIV-2 EHO genome revealed a significant degree of divergence of its envelope gene from that of other known HIV-2 strains. This divergence for the deduced amino acid sequence corresponding to the extracellular envelope glycoprotein was 26 to 30%. These unique genetic and biological properties suggest that the HIV-2 EHO isolate is a distinct prototype in the HIV-2 family.
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PMID:HIV-2 EHO isolate has a divergent envelope gene and induces single cell killing by apoptosis. 800 58

Infection of goat synovial membrane (GSM) cells by caprine arthritis-encephalitis virus (CAEV) was inhibited by incubation of cells with CAEV gp 135 envelope glycoprotein (SU) expressed by recombinant vaccinia virus. Incubation of cells with protein expressed by a control recombinant vaccinia virus without the CAEV envelope gene did not inhibit CAEV infection. Removal of recombinant SU from blocking medium by adsorption with anti-SU IgG/protein G-Sepharose complexes resulted in loss of CAEV inhibition. Results support that CAEV infection of GSM cells is mediated by a specific interaction between SU and a cell surface receptor or receptor complex.
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PMID:Caprine arthritis-encephalitis lentivirus SU is the ligand for infection of caprine synovial membrane cells. 839 Jul 59

Two molecularly cloned, replication-defective variants of feline leukemia virus, called 61B and 61C, have both been shown to cause fatal immunodeficiency in cats when coinfected with a replication-competent, minimally pathogenic helper virus, but 61B exhibits a longer latency period between infection and disease (J. Overbaugh, E. A. Hoover, J. I. Mullins, D. P. W. Burns, L. Rudensey, S. L. Quackenbush, V. Stallard, and P. R. Donahue, Virology 188:558-569, 1992). Infection of the 3201 feline T-cell line with 61B plus helper virus also results in longer time from infection to cytopathic effect compared with 61C plus helper virus, providing an in vitro system with which to study the mechanism for this difference. We report that the primary determinant of cytopathicity of 61B maps to gp70, the extracellular envelope glycoprotein. The long latency of 61B, on the other hand, maps to the extracellular portion of the envelope transmembrane protein, in which there are only four predicted amino acid differences between 61B and 61C. These differences render 61B replication defective, and two of the predicted amino acid changes lie in a region that is highly conserved among many retroviruses. The eventual onset of 61B cytopathicity in cell culture was associated with the outgrowth of an apparent recombinant virus that encodes the pathogenic gp70 of 61B and replaces the transmembrane protein of 61B with that of the helper virus. Thus, during in vitro infection, a cytopathic virus evolved from a replication-defective virus and a nonpathogenic virus, suggesting that recombination between multiple variants in natural infection may influence progression of feline leukemia virus-associated immunodeficiency disease.
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PMID:Delayed cytopathicity of a feline leukemia virus variant is due to four mutations in the transmembrane protein gene. 839 54

Infection by Epstein-Barr virus (EBV), a B lymphotropic human herpesvirus, of its target cells is initiated by the binding of the viral envelope glycoprotein gp350/220 to a 145-kDa cell membrane glycoprotein (CD21, CR2) which also serves as the receptor for the complement fragment C3d (Fingeroth et al., 1984; Nemerow et al., 1987). We used the fluorescent probe 1-6-diphenyl-1,3,5-hexatriene (DPH), extremely sensitive to the polar environment, in order to analyse the membrane viscosity distribution in single cells of two lymphoid cell lines, Raji and Akata. Lipid analysis on both cell lines showed a slightly lower cholesterol:phospholipid molar ratio on Akata than on Raji cells. Measurements of cell fluidity by DPH polarization in native cells and after cholesterol enrichment indicated that the apparent Akata membrane viscosity was lower than the viscosity of Raji cells. To examine the possibility that this difference could be correlated to a difference in the behaviour of Akata and Raji cells in expressing EBV early antigens, both lines were superinfected with the EBV non-transforming P3HR1 strain. We report here evidence that lipid composition can regulate EBV entry into cells.
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PMID:Role of Akata cell membrane fluidity in susceptibility to Epstein-Barr virus infection. 853 94

Infection by human immunodeficiency virus type 1 (HIV-1) leads to progressive destruction of the CD4+ T-cell subset, resulting in immune deficiency and AIDS. The specific binding of the viral external envelope glycoprotein of HIV-1, gp120, to the CD4 molecules initiates viral entry. In the past few years, several studies have indicated that the interaction of HIV-1 envelope glycoprotein with cells and molecules of the immune system leads to pleiotropic biological effects on immune functions, which include effects on differentiation of CD34+ lymphoid progenitor cells and thymocytes, aberrant activation and cytokine secretion patterns of mature T cells, induction of apoptosis, B-cell hyperactivity, inhibition of T-cell dependent B-cell differentiation, modulation of macrophage functions, interactions with components of complement, and effects on neuronal cells. The amino acid sequence homologies of the envelope glycoproteins with several cellular proteins have suggested that molecular mimicry may play a role in the pathogenesis of the disease. This review summarizes work done by several investigators demonstrating the profound biological effects of envelope glycoproteins of HIV-1 on immune system cells. Extensive studies have also been done on interactions of the viral envelope proteins with components of the immune system which may be important for eliciting a "protective immune response." Understanding the influences of HIV-1 envelope glycoproteins on the immune system may provide valuable insights into HIV-1 disease pathogenesis and carries implications for the trials of HIV-1 envelope protein vaccines and immunotherapeutics.
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PMID:Envelope glycoproteins of human immunodeficiency virus type 1: profound influences on immune functions. 880 39

Infection with HIV-1 results in a disruption of the thymic microenvironment and the presence of HIV-1 in thymic epithelial cells has been demonstrated in vivo. In the present study, we examined the susceptibility of a highly enriched culture of thymic epithelial cells (TEC) to infection in vitro by HIV-1 laboratory strains and primary isolates. Replication in TEC is shown to depend on the virus and on the expression of CD4 molecules that are found to be expressed at a low density on the plasma membrane. Our results are consistent with infection of TEC controlled by the efficiency of the interactions between the envelope glycoprotein of the virus and the cell surface molecules. As a consequence, certain HIV-1 viruses induce a productive and persistent infection in TEC without damaging the cells. Altogether these results support the idea that TEC may act as a reservoir for HIV-1 in the thymus but are probably destroyed by an indirect mechanism involving infection of thymocytes.
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PMID:Productive and persistent infection of human thymic epithelial cells in vitro with HIV-1. 891 29

HIV preferentially infects the RO+ memory subset of CD4+ lymphocytes, and these cells are lost earlier in HIV infection than their RA+ counterparts. Although both populations express similar amounts of CD4 and bind the HIV envelope glycoprotein (gp120) equally well, calcium signals and CD4 down-regulation subsequent to gp120 binding are not the same in both populations. Data suggest these disparities are mediated by differential tyrosine kinase (TK) regulation. Syncytium formation is enhanced in RO+ cells, partly a consequence of increased leucocyte function antigen-1 (LFA-1) expression and, again, partly due to altered TK regulation. After in vitro HIV infection, reverse transcription is not detected in RA+ cells, is minimal in the RO+ class II- population, but progresses well in RO+ class II+. Infection followed by mitogen stimulation permits reverse transcription in all cells. HIV infection of RO+ cells is enhanced moderately at multiple points in the virus life cycle.
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PMID:HIV infection of CD45RA+ and CD45RO+ CD4+ T cells. 903 Aug 67

Infection of human monocytes with human immunodeficiency virus type (HIV-1 LAI) triggers the release of both the cytokine tumour necrosis factor alpha (TNF-alpha) and its soluble receptor (TNFsr). In the present study, the authors have investigated the cellular events implicated in the modulation of expression and shedding of the monocyte TNF receptor induced by HIV-1 LAI. Release of TNFsr75 was triggered at an early step of interaction of the virus particles with the monocyte, involving the envelope glycoprotein gp120. HIV-1 LAI induced an upregulation of TNFr75 mRNA, whereas TNFr55 mRNA was not detectable. TNFsr75 release required exocytosis, proteolytic cleavage by serine protease(s), but was independent of prior endocytosis of the receptor. Early shedding of TNFr75 accounted for the almost total but transient disappearance of the membrane TNF receptor P75, observed 60 min after activation with HIV-1 LAI, whereas internalization was minimal. Endogenous TNF-alpha had no role in the disappearance of its own receptor. Complete and stable restoration of TNFr expression at the cell membrane, dependent on de novo protein synthesis, occurred after 5 h, followed by massive TNFsr75 release. These results demonstrate that interaction of human monocytes with HIV-1 LAI triggers at an early stage a cascade of cellular events that lead to profound remodeling of the cell TNFr pool. Understanding the mechanisms of these receptor movements is of importance to document the central role of the TNF system in HIV infection.
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PMID:Mechanisms of downmodulation and release of tumour necrosis factor receptor induced by human immunodeficiency virus type 1 in human monocytes. 906 91

Human immunodeficiency virus type 1 (HIV-1) normally enters cells by direct fusion with the plasma membrane. In this report, HIV-1 particles capable of infecting cells through an endocytic pathway are described. Chimeric viruses composed of the HIV-1 core and the envelope glycoprotein of vesicular stomatitis virus (VSV-G) were constructed and are herein termed HIV-1(VSV) pseudotypes. HIV-1(VSV) pseudotypes were 20- to 130-fold more infectious than nonpseudotyped HIV-1. Infection by HIV-1(VSV) pseudotypes was markedly diminished by ammonium chloride and concanamycin A, a selective inhibitor of vacuolar H+ ATPases, demonstrating that these viruses require endosomal acidification to achieve productive infection. HIV-1 is thus capable of performing all of the viral functions necessary for infection when entry is targeted to an endocytic route. Maximal HIV-1 infectivity requires the presence of the viral Nef protein and the cellular protein cyclophilin A (CyPA) during virus assembly. Pseudotyping by VSV-G markedly suppressed the requirement for Nef. HIV-1(VSV) particles were also resistant to inhibition by cyclosporin A; however, the deleterious effect of a gag mutation inhibiting CyPA incorporation was not relieved by VSV-G. These results suggest that Nef acts at a step of the HIV-1 life cycle that is either circumvented or facilitated by targeting virus entry to an endocytic pathway. The findings also support the hypothesis that Nef and CyPA enhance HIV-1 infectivity through independent processes and demonstrate a mechanistic difference between reduction of HIV-1 infectivity by cyclosporin A and gag mutations that decrease HIV-1 incorporation of CyPA.
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PMID:Pseudotyping human immunodeficiency virus type 1 (HIV-1) by the glycoprotein of vesicular stomatitis virus targets HIV-1 entry to an endocytic pathway and suppresses both the requirement for Nef and the sensitivity to cyclosporin A. 922 76

The biological phenotype of primary human immunodeficiency virus type 1 (HIV-1) isolates varies according to the severity of the HIV infection. Here we show that the two previously described groups of rapid/high, syncytium-inducing (SI) and slow/low, non-syncytium-inducing (NSI) isolates are distinguished by their ability to utilize different chemokine receptors for entry into target cells. Recent studies have identified the C-X-C chemokine receptor CXCR4 (also named fusin or Lestr) and the C-C chemokine receptor CCR5 as the principal entry cofactors for T-cell-line-tropic and non-T-cell-line-tropic HIV-1, respectively. Using U87.CD4 glioma cell lines, stably expressing the chemokine receptor CCR1, CCR2b, CCR3, CCR5, or CXCR4, we have tested chemokine receptor specificity for a panel of genetically diverse envelope glycoprotein genes cloned from primary HIV-1 isolates and have found that receptor usage was closely associated with the biological phenotype of the virus isolate but not the genetic subtype. We have also analyzed a panel of 36 well-characterized primary HIV-1 isolates for syncytium induction and replication in the same series of cell lines. Infection by slow/low viruses was restricted to cells expressing CCR5, whereas rapid/high viruses could use a variety of chemokine receptors. In addition to the regular use of CXCR4, many rapid/high viruses used CCR5 and some also used CCR3 and CCR2b. Progressive HIV-1 infection is characterized by the emergence of viruses resistant to inhibition by beta-chemokines, which corresponded to changes in coreceptor usage. The broadening of the host range may even enable the use of uncharacterized coreceptors, in that two isolates from immunodeficient patients infected the parental U87.CD4 cell line lacking any engineered coreceptor. Two primary isolates with multiple coreceptor usage were shown to consist of mixed populations, one with a narrow host range using CCR5 only and the other with a broad host range using CCR3, CCR5, or CXCR4, similar to the original population. The results show that all 36 primary HIV-1 isolates induce syncytia, provided that target cells carry the particular coreceptor required by the virus.
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PMID:Coreceptor usage of primary human immunodeficiency virus type 1 isolates varies according to biological phenotype. 931 27


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