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)

Previous studies have shown that the gene coding for the Vpu protein of the human immunodeficiency virus type 1 (HIV-1) is 5' to the env gene, is in a different reading frame, and overlaps the env by 90 nucleotides. In this study, we examined the processing of the Env protein as well as the maturation and infectivity of a virus (SHIV(Vpenv)) in which a single nucleotide was removed at the vpu-env junction, fusing the first 162 bases of vpu to the env ORF. Pulse-chase analysis revealed that SHIV(Vpenv)-infected cells gave rise to two precursor glycoprotein species (gp160 and gp175). Immune precipitation results also revealed that an anti-Vpu serum could immune precipitate the gp175 precursor, suggesting that the amino-terminal Vpu sequence was fused to the Env protein. Growth curves revealed that the SHIV(Vpenv)-inoculated cultures released approximately three times more p27 into the culture medium than parental SHIV(KU-1bMC33). Electron microscopy revealed that while both viruses matured at the cell plasma membrane, significantly higher quantities of virus particles were cell associated on SHIV(Vpenv)-infected cells compared to cultures inoculated with parental SHIV(KU-1bMC33). Furthermore, virus was observed maturing into intracellular vesicles of SHIV(Vpenv)-infected cells. To assess the pathogenicity of SHIV(Vpenv), three pig-tailed macaques were inoculated with the SHIV(Vpenv) and monitored for 6 months for CD4(+) T cell levels, viral loads, and the stability of the deletion at the vpu-env junction. Our results indicated that SHIV(Vpenv) caused a severe CD4(+) T cell loss in all three macaques within weeks of inoculation. Sequence analysis of the vpu gene analyzed from sequential PBMC samples derived from macaques revealed that this mutation was stable during the period of rapid CD4(+) T cell loss. Sequence analysis showed that with increasing time of infection, the one base pair deletion was repaired in all three macaques inoculated with SHIV(Vpenv) with the reversion occurring at 10 weeks in macaque CT1G and at 12 weeks in macaque CP3R and CT1R. These results indicate that fusion of the first 54 amino acids of Vpu to Env results in intracellular maturation of virus, and accumulation of virus within intracellular vesicles as well as on the cell plasma membrane. Our results indicate that while fusion of the vpu gene to env results in a virus that is still pathogenic for pig-tailed macaques, there is a selective pressure to maintain the vpu and env genes in separate reading frames.
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PMID:Fusion of the upstream vpu sequences to the env of simian human immunodeficiency virus (SHIV(KU-1bMC33)) results in the synthesis of two envelope precursor proteins, increased numbers of virus particles associated with the cell surface and is pathogenic for pig-tailed macaques. 1516 22

Experimental vaccines based on recombinant vesicular stomatitis viruses (VSV) expressing foreign viral proteins are protective in several animal disease models. Although these attenuated viruses are nonpathogenic in nonhuman primates when given by nasal, oral, or intramuscular routes, they are pathogenic in mice when given intranasally, and further vector attenuation may be required before human trials with VSV-based vectors can begin. Mutations truncating the VSV glycoprotein (G) cytoplasmic domain from 29 to 9 or 1 amino acid (designated CT9 or CT1, respectively) were shown previously to attenuate VSV growth in cell culture and pathogenesis in mice. Here we show that VSV recombinants carrying either the CT1 or CT9 deletion and expressing the human immunodeficiency virus (HIV) Env protein are nonpathogenic in mice, even when given by the intranasal route. We then carried out a detailed analysis of the CD8+ T-cell responses, including in vivo cytotoxic T-cell activity, induced by these vectors. When given by either the intranasal or intraperitoneal route, the VSV-CT9 vector expressing HIV Env elicited primary and memory CD8+ T-cell responses to Env equivalent to those elicited by recombinant wild-type VSV expressing Env. The VSV-CT1 vector also induced potent CD8+ T-cell responses after intraperitoneal vaccination, but was less effective when given by the intranasal route. The VSV-CT1 vector was also substantially less effective than the VSV-CT9 or wild-type vector at inducing antibody to Env. The VSV-CT9 vector appears ideal because of its lack of pathogenesis, propagation to high titers in vitro, and stimulation of strong cellular and humoral immune responses.
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PMID:Characterization of nonpathogenic, live, viral vaccine vectors inducing potent cellular immune responses. 1530 26

We investigated the effect of the conserved tyrosine-based endocytosis motif (YXXPhi) in the cytoplasmic domain of the human immunodeficiency viruses (HIV) envelope protein (Env) on its immunogenicity. Genes with codons optimized for mammalian expression were synthesized for the HIV 89.6 Env with a truncated cytoplasmic domain and a mutant Env in which the tyrosine residue in the YXXPhi motif was changed into a serine. Mutation of the Tyr residue enhanced surface expression of the Env protein. Analysis of immune responses induced by DNA immunization of mice showed that the DNA construct for the Tyr mutant Env induced moderately higher levels of T cell responses. More interestingly, the DNA construct for the mutant Env induced significantly higher levels of antibody responses against the Env protein in comparison to the construct for the wild type Env. Our results suggest that the YXXPhi motif in the HIV Env cytoplasmic domain may play a role in virus evasion of host immune responses through affecting its immunogenicity.
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PMID:Enhancement of immunogenicity of an HIV Env DNA vaccine by mutation of the Tyr-based endocytosis motif in the cytoplasmic domain. 1538 Mar 59

The effects of two functional domains, the membrane-proximal YXXPhi motif and the membrane-distal inhibitory sequence in the long cytoplasmic tail of the human immunodeficiency virus type 1 (HIV-1) envelope protein (Env), on immunogenicity of the envelope protein were investigated. Genes with codons optimized for mammalian expression were synthesized for the HIV 89.6 Env and a truncated Env with 50 amino acids in the cytoplasmic domain to delete the membrane distal inhibitory sequence for surface expression. Additional genes were generated in which the tyrosine residue in the YXXPhi motif was changed into a serine. Pulse-chase radioactive labeling and immunoprecipitation studies indicated that both domains can mediate endocytosis of the HIV Env, and removal of both domains is required to enhance HIV Env protein surface stability. Analysis of immune responses induced by DNA immunization of mice showed that the DNA construct for the mutant Env exhibiting enhanced surface stability induced significantly higher levels of antibody responses against the HIV Env protein. Our results suggest that the HIV Env cytoplasmic domain may play important roles in virus infection and pathogenesis by modulating its immunogenicity.
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PMID:Surface stability and immunogenicity of the human immunodeficiency virus envelope glycoprotein: role of the cytoplasmic domain. 1556 51

The target for neutralizing antibodies against human immunodeficiency virus (HIV) is the trimeric Env protein on the native virion. Conserved neutralizing epitopes of receptor binding sites are located in the recessed core of the Env protein, partially masked by glycosylations and variable loops. In this study, we have investigated the effects of modifications of the HIV Env protein by glycosylation site mutations, deletions of variable loops, or combinations of both types of mutations on their protein functions and reactivities with neutralizing antibodies. Modified Env proteins were expressed in insect or mammalian cells, and their reactivity with epitope-specific broadly neutralizing monoclonal antibodies (Mabs) was determined by flow cytometry. A unique mutant designated 3G with mutations in three glycosylation motifs within the V3/C3 domains surrounding the CD4 binding site showed higher levels of binding to most broadly neutralizing Mabs (b12 and 2F5) in both insect and mammalian expression systems. Mutants with a deletion of both V1 and V2 loop domains or with a unique combination of both types of mutations also bound to most neutralizing Mabs at higher levels compared to the wild-type control. Most mutants maintained the ability to bind CD4 and to induce syncytium formation at similar or higher levels as compared to that of the wild-type Env protein, except for a mutant with a combination of variable loop deletions and deglycosylation mutations. Our study suggests that modified HIV Env proteins with reduced glycosylation in domains surrounding the CD4 binding site or variable loop-deleted mutants expose important neutralizing epitopes at higher levels than wild type and may provide novel vaccine immunogens.
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PMID:Modified HIV envelope proteins with enhanced binding to neutralizing monoclonal antibodies. 1558 50

In contrast to most gammaretrovirus envelope proteins (Env), the Gibbon ape leukemia virus (GaLV) Env protein does not mediate the infectivity of human immunodeficiency virus type 1 (HIV-1) particles. We made use of this observation to set up a directed evolution system by creating a library of GaLV Env variants diversified at three critical amino acids, all located around the R-peptide cleavage site within the cytoplasmic tail. This library was screened for variants that were able to functionally pseudotype HIV-1 vector particles. All selected Env variants mediated the infectivity of HIV-1 vector particles and encoded novel cytoplasmic tail motifs. They were efficiently incorporated into HIV particles, and the R peptide was processed by the HIV protease. Interestingly, in some of the selected variants, the R-peptide cleavage site had shifted closer to the C terminus. These data demonstrate a valuable approach for the engineering of chimeric viruses and vector particles.
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PMID:Directed evolution of retrovirus envelope protein cytoplasmic tails guided by functional incorporation into lentivirus particles. 1561 11

Entry of lentiviruses, such as human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV), requires folding of two heptad repeat regions (HR1 and HR2) of gp41 into a trimer-of-hairpins, which subsequently brings virus and cell membrane into fusion. This motif is a generalized feature of viral fusion proteins and has been exploited in generating antiviral fusion agents. In the present paper, we report structural characters of Env protein from another lentivirus, bovine immunodeficiency virus (BIV), which contributes to a good animal model of HIV. BIV HR1 and HR2 regions are predicted by two different programs and expressed separately or conjointly in Escherichia coli. Biochemical and biophysical analyses show that the predicted HRs of BIV Env can form a stable trimer-of-hairpins or six-helix bundle just like that formed by feline immunodeficiency virus Env. Cell fusion assay demonstrates that the HR2 peptide of BIV can efficiently inhibit the virus-mediated cell fusion.
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PMID:Characterization of BIV Env core: implication for mechanism of BIV-mediated cell fusion. 1573 28

The human immunodeficiency virus-1 (HIV-1) envelope glycoprotein (Env) is comprised of non-covalently associated gp120/gp41 subunits that form trimeric spikes on the virion surface. Upon binding to host cells, Env undergoes a series of structural transitions, leading to gp41 rearrangement necessary for fusion of viral and host membranes. Until now, the prefusion state of gp41 ectodomain (e-gp41) has eluded molecular and structural analysis, and thus assessment of the potential of such an e-gp41 conformer to elicit neutralizing antibodies has not been possible. Considering the importance of gp120 amino (C1) and carboxyl (C5) segments in the association with e-gp41, we hypothesize that these regions are sufficient to maintain e-gp41 in a prefusion state. Based on the available gp120 atomic structure, we designed several truncated gp140 variants by including the C1 and C5 regions of gp120 in a gp41 ectodomain fragment. After iterative cycles of protein design, expression and characterization, we obtained a variant truncated at Lys(665) that stably folds as an elongated trimer under physiologic conditions. Several independent biochemical/biophysical analyses strongly suggest that this mini-Env adopts a prefusion e-gp41 configuration that is strikingly distinct from the postfusion trimer-of-hairpin structure. Interestingly, this prefusion mini-Env, lacking the fragment containing the 2F5/4E10 neutralizing monoclonal antibody binding sites, displays no detectable HIV-neutralizing epitopes when employed as an immunogen in rabbits. The result of this immunogenicity study has important implications for HIV-1 vaccine design efforts. Moreover, this engineered mini-Env protein should facilitate three-dimensional structural studies of the prefusion e-gp41 and serve to guide future attempts at pharmacologic and immunologic intervention of HIV-1.
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PMID:Design, expression, and immunogenicity of a soluble HIV trimeric envelope fragment adopting a prefusion gp41 configuration. 1583 40

Adaptation of antibody neutralization-resistant human immunodeficiency virus type I (HIV-1) to growth in vitro generally results in the acquisition of a neutralization-sensitive phenotype, an alteration of viral growth kinetics, and an array of amino acid substitutions associated with these changes. Here we examine a panel of Env chimeras and mutants derived from these neutralization-resistant and -sensitive parental Envs. A range of neutralization and infectivity phenotypes was observed. These included a modulation of the CD4 binding site (CD4bs) towards recognition by neutralizing and non-neutralizing CD4bs-directed antibodies, resulting in a globally neutralization-sensitive Env; alterations which affected Env complex stability; and interactions which resulted in differential infectivity and CCR5/CXCR4 usage. This range of properties resulted from the complex interactions of no more than three amino acids found in key Env locations. These data add to a growing body of evidence that dramatic functional alterations of the native oligomeric Env protein complex can result from relatively minor amino acid substitutions.
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PMID:Neutralization sensitivity of HIV-1 Env-pseudotyped virus clones is determined by co-operativity between mutations which modulate the CD4-binding site and those that affect gp120-gp41 stability. 1591 27

DNA vaccines have been used widely in experimental primate models of human immunodeficiency virus (HIV), but their effectiveness has been limited. In this study, we evaluated three technologies for increasing the potency of DNA vaccines in rhesus macaques. These included DNA encoding Sindbis virus RNA replicons (pSINCP), cationic poly(lactide-co-glycolide) (PLG) microparticles for DNA delivery, and recombinant protein boosting. The DNA-based pSINCP replicon vaccines encoding HIV Gag and Env were approximately equal in potency to human cytomegalovirus (CMV) promoter-driven conventional DNA vaccines (pCMV). The PLG microparticle DNA delivery system was particularly effective at enhancing antibody responses induced by both pCMV and pSINCP vaccines and had less effect on T cells. Recombinant Gag and Env protein boosting elicited rapid and strong recall responses, in some cases to levels exceeding those seen after DNA or DNA/PLG priming. Of note, Env protein boosting induced serum-neutralizing antibodies and increased frequencies of gamma interferon-producing CD4 T cells severalfold. Thus, PLG microparticles are an effective means of delivering DNA vaccines in nonhuman primates, as demonstrated for two different types of DNA vaccines encoding two different antigens, and are compatible for use with DNA prime-protein boost regimens.
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PMID:Enhanced potency of plasmid DNA microparticle human immunodeficiency virus vaccines in rhesus macaques by using a priming-boosting regimen with recombinant proteins. 1595 64


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