Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0021051 (immunodeficiency)
 71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Development of viral resistance to the aminodiol human immunodeficiency virus (HIV) protease inhibitor BMS 186,318 was studied by serial passage of HIV type 1 RF in MT-2 cells in the presence of increasing concentrations of compound. After 11 passages, an HIV variant that showed a 15-fold increase in 50% effective dose emerged. This HIV variant displays low-level cross-resistance to the C2 symmetric inhibitor A-77003 but remains sensitive to the protease inhibitors Ro 31-8959 and SC52151. Genetic analysis of the protease gene from a drug-resistant variant revealed an Ala-to-Thr change at amino acid residue 71 (A71T) and a Val-to-Ala change at residue 82 (V82A). To determine the effects of these mutations on protease and virus drug susceptibility, recombinant protease and proviral HIV type 1 clones containing the single mutations A71T and V82A or double mutation A71T/V82A were constructed. Subsequent drug sensitivity assays on the mutant proteases and viruses indicated that the V82A substitution was responsible for most of the resistance observed. Further genotypic analysis of the protease genes from earlier passages of virus indicated that the A71T mutation emerged prior to the V82A change. Finally, the level of resistance did not increase following continued passage in increasing concentrations of drug, and the resistant virus retained its drug susceptibility phenotype 34 days after drug withdrawal.
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PMID:Characterization of a human immunodeficiency virus type 1 variant with reduced sensitivity to an aminodiol protease inhibitor. 788 62

We have established a hybridoma clone, designated 2F5, secreting a neutralizing human monoclonal antibody (MAb) specific for gp41 of human immunodeficiency virus type 1 (HIV-1). The epitope of MAb 2F5 was mapped to amino acid sequence Glu-Leu-Asp-Lys-Trp-Ala on the ectodomain of gp41. In this study different in vitro test systems were used to characterize the neutralizing properties of MAb 2F5. In syncytium inhibition assays, fusion inhibition experiments, and neutralization assays on different HIV-susceptible cells (H9, U937, and peripheral blood mononuclear cells) MAb 2F5 showed broad-spectrum neutralizing capacity against HIV-1 laboratory isolates IIIB, MN, RF, and SF2. In addition, primary isolates from AIDS patients were also neutralized.
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PMID:A broadly neutralizing human monoclonal antibody against gp41 of human immunodeficiency virus type 1. 788 24

Proviral clones of human immunodeficiency virus type 1 which contained single amino acid changes in the envelope V3 region were constructed. PCR amplification of Sup-T1 T cells transfected with one such mutant, G312T, revealed low levels of virus that resulted in the generation of a revertant virus, in which an alanine replaced the threonine residue at amino acid 312. The revertant virus (rA312) was fully infectious in Sup-T1 cells but lacked the ability to infect AA5 cells. The presence of a second mutation in a subsequent revertant virus (rR306), in which arginine was substituted for serine at amino acid 306 within the V3 loop, restored the ability of the mutated virus to infect AA5 cells. Our data highlight the importance of the V3 loop in defining virus tropism for specific cell types in culture and further suggest that a degree of interplay exists among V3 loop residues that helps maintain or control its biological function of the virus.
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PMID:Effect of a single amino acid substitution in the V3 domain of the human immunodeficiency virus type 1: generation of revertant viruses to overcome defects in infectivity in specific cell types. 796 30

T-cell-line-tropic human immunodeficiency virus type 1 cannot infect CD4-positive, brain-derived cells. We isolated several new variants that readily infected brain-derived cells. Mutation of proline to serine, to alanine, or to threonine in the well-conserved GPGR sequence in the V3 region of the envelope glycoprotein was found in all these variants. This indicates the importance of amino acid sequences at the tip of the V3 region for brain cell tropism of human immunodeficiency virus type 1.
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PMID:Isolation and characterization of human immunodeficiency virus type 1 variants infectious to brain-derived cells: detection of common point mutations in the V3 region of the env gene of the variants. 798 Jul 82

The glycosphingolipid galactosylceramide (GalCer), which binds gp120 with high affinity and specificity, is a potential alternative receptor for human immunodeficiency virus type 1 (HIV-1) in some CD4-negative neural and epithelial human cells, including the human colonic epithelial cell line HT-29. In the present study, we demonstrate that synthetic multibranched peptides derived from the consensus sequence of the HIV-1 V3 loop block HIV-1 infection in HT-29 cells. The most active peptide was an eight-branched multimer of the motif Gly-Pro-Gly-Arg-Ala-Phe which at a concentration of 1.8 microM induced a 50% inhibition of HIV-1 infection in competition experiments. This peptide was not toxic to HT-29 cells, and preincubation with HIV-1 did not affect viral infectivity, indicating that the antiviral activity was not due to a nonspecific virucidal effect. Using a high-performance thin-layer chromatography binding assay, we found that multibranched V3 peptides recognized GalCer and inhibited binding of recombinant gp120 to the glycosphingolipid. In addition, these peptides abolished the binding of an anti-GalCer monoclonal antibody to GalCer on the surface of live HT-29 cells. These data provide additional evidence that the V3 loop is involved in the binding of gp120 to the GalCer receptor and show that multibranched V3 peptides are potent inhibitors of the GalCer-dependent pathway of HIV-1 infection in CD4-negative mucosal epithelial cells.
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PMID:Synthetic multimeric peptides derived from the principal neutralization domain (V3 loop) of human immunodeficiency virus type 1 (HIV-1) gp120 bind to galactosylceramide and block HIV-1 infection in a human CD4-negative mucosal epithelial cell line. 798 25

Integrase is the only viral protein necessary for integration of retroviral DNA into chromosomal DNA of the host cell. Biochemical analysis of human immunodeficiency virus type 1 (HIV-1) integrase with purified protein and synthetic DNA substrates has revealed extensive information regarding the mechanism of action of the enzyme, as well as identification of critical residues and functional domains. Since in vitro reactions are carried out in the absence of other viral proteins and they analyze strand transfer of only one end of the donor substrate, they do not define completely the process of integration as it occurs during the course of viral infection. In an effort to further understand the role of integrase during viral infection, we initially constructed a panel of 24 HIV-1 mutants with specific alanine substitutions throughout the integrase coding region and analyzed them in a human T-cell line infection. Of these mutant viruses, 12 were capable of sustained viral replication, 11 were replication defective, and 1 was temperature sensitive for viral growth. The replication defective viruses express and correctly process the integrase and Gag proteins. Using this panel of mutants and an additional set of 18 mutant viruses, we identified nine amino acids which, when replaced with alanine, destroy integrase activity. Although none of the replication-defective mutants are able to integrate into the host genome, a subset of them with alterations in the catalytic triad are capable of Tat-mediated transactivation of an indicator gene linked to the viral long terminal repeat promoter. We present evidence that integration of the HIV-1 provirus is essential not only for productive infection of T cells but also for virus passage in both cultured peripheral blood lymphocytes and macrophage cells.
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PMID:Human immunodeficiency virus type 1 integrase: effects of mutations on viral ability to integrate, direct viral gene expression from unintegrated viral DNA templates, and sustain viral propagation in primary cells. 798 32

Between hypervariable regions V1 and V2 of human immunodeficiency virus type 1 (HIV-1) gp120 lies a cluster of relatively conserved residues. The contribution of nine charged residues in this region to virus infectivity was evaluated by single-amino-acid substitutions in an infectious provirus clone. Three of the HIV-1 mutants studied had slower growth kinetics than the wild-type virus. The delay was most pronounced in a mutant with an alanine substituted for an aspartic acid residue at position 180. This aspartic acid is conserved by all HIV-1 isolates with known nucleotide sequences. Substitutions with three other residues at this position, including a negatively charged glutamic acid, all affected virus infectivity. The defect identified in these mutants suggests that this aspartic acid residue is involved in the early stages of HIV-1 replication.
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PMID:The highly conserved aspartic acid residue between hypervariable regions 1 and 2 of human immunodeficiency virus type 1 gp120 is important for early stages of virus replication. 798 52

We have created a temperature-sensitive (ts) mutant of human immunodeficiency virus type 1, using the technique of charge-cluster-to-alanine scanning mutagenesis to introduce specific changes into the integrase coding region. In the ts mutant virus, the lysine at amino acid 136 and the glutamic acid at amino acid 138 of integrase have been replaced with alanines (K136A/E138A). When K136A/E138A is synthesized at 35 degrees C, it replicates to a similar degree as wild-type virus during infection of CEM cells at 35 degrees C on the basis of syncytium formation, levels of core antigen, and reverse transcriptase activity. However, during infection at the nonpermissive temperature of 39.5 degrees C, K136A/E138A is capable of only one round of integration. Mutant virions formed at 39.5 degrees C do not integrate but are indistinguishable from wild-type virions when scored for activity of reverse transcriptase and correct expression and processing of Gag and Pol proteins. We demonstrate that the defect responsible for the ts phenotype of K136A/E138A is localized to a step after proviral formation and integrase protein synthesis but prior to particle maturation. It is the temperature at which the K136A/E138A virion is synthesized, not the temperature at which infection occurs, which determines the ability of the virus to integrate.
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PMID:Identification and characterization of a temperature-sensitive mutant of human immunodeficiency virus type 1 by alanine scanning mutagenesis of the integrase gene. 798 62

Retroviral capsid (CA) proteins contain a uniquely conserved stretch of 20 amino acids which has been named the major homology region (MHR). To examine the role of this region in human immunodeficiency virus type 1 morphogenesis and replication, four highly conserved positions in the MHR were individually altered by site-directed mutagenesis. Conservative substitution of two invariant residues (glutamine 155 and glutamic acid 159) abolished viral replication and significantly reduced the particle-forming ability of the mutant gag gene products. Conservative substitution of the third invariant residue in the MHR (arginine 167) or of an invariably aromatic residue (tyrosine 164) had only a moderate effect. However, removal of the extended side chains of these amino acids by substitution with alanine prevented viral replication and affected virion morphogenesis. The replacement of tyrosine 164 with alanine substantially impaired viral particle production. By contrast, the substitution of arginine 167 with alanine had only a two- to threefold effect on particle yield but led to the formation of aberrant core structures. The MHR mutant which were severely defective for particle production had a dominant negative effect on particle formation by the wild-type Gag product. The role of the MHR in the incorporation of the Gag-Pol precursor was examined by expressing the Gag and Gag-Pol polyproteins individually from separate plasmids. Only when the two precursor polyproteins were coexpressed did processed Gag and Pol products appear in the external medium. The appearance of these products was unaffected or only moderately affected by substitutions in the MHR of the Gag-Pol precursor, suggesting that the mutant Gag-Pol precursors were efficiently incorporated into viral particles. The results of this study indicate that specific residues within the MHR are required both for human immunodeficiency virus type 1 particle assembly and for the correct assembly of the viral core. However, mutant Gag and Gag-Pol polyproteins with substitutions in the MHR retained the ability to interact with wild-type Gag protein.
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PMID:Role of the major homology region of human immunodeficiency virus type 1 in virion morphogenesis. 803 91

The most preferred residue in the substrates of human immunodeficiency virus (HIV-1) protease is glutamic acid in the P2' position. The catalytic importance of this charged residue has been studied to obtain a detailed insight into the mechanism of action, which will promote drug design to combat the virus. To this end, we have synthesized Lys-Ala-Arg-Val-Leu*Phe(NO2)-Glu-Ala-Nle (substrate E) and its counterpart containing the neutral Gln (substrate Q) in place of Glu. Kinetic analyses have shown that the specificity rate constants (kcat/Km) display bell-shaped pH dependencies for both substrates, but the pH-independent limiting value is 35-40-fold higher with substrate E than with substrate Q. In contrast to the pH-rate profiles of kcat/Km, there is a striking difference between the pH dependencies of Km and kcat for the two substrates. This indicates different ground state and transition state stabilizations in the two reactions. Solvent kinetic deuterium isotope effects show that the rate-limiting step for the hydrolysis of substrate E is a chemical step coupled with proton transfer whereas with substrate Q it is a physical step, presumably a conformational change. Accordingly, the charged residue in P2' alters the rate-limiting step and the nature of the enzyme-substrate complex, resulting in different mechanisms for the two substrates.
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PMID:Substrate-dependent mechanisms in the catalysis of human immunodeficiency virus protease. 804 36


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