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Query: UMLS:C0021051 (immunodeficiency)
 71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The human immunodeficiency virus type 1 (HIV-1) Pr55gag precursors were previously shown to assemble and bud efficiently as noninfectious virus-like particles (VLPs) when expressed in baculovirus-infected insect cells. In this study, we examined the abilities of foreign antigens to be incorporated on the outer surface of HIV-1 Gag particles. We have used a dual recombinant baculovirus, expressing the HIV-1 Gag gene and gD gene under the control of the P10 and polyhedrin promoters, respectively, to obtain hybrid VLPs. Transmission electron microscopy of insect cells infected with the dual recombinant revealed very large aggregates of particles budding from the cell membrane. The release of VLPs into the culture medium was clearly different for a recombinant baculovirus producing solely HIV-1 Gag, for which particles were uniformly distributed all around the cell surface. Biochemical analysis of hybrid particles indicated that glycoprotein gD was packaged into HIV-1 Gag VLPs. Moreover, the carboxy-terminal p6 region of Gag polyprotein and the glycoprotein gD intracytoplasmic domain were not required for gD incorporation. The experiments described here clearly demonstrate that glycoprotein gD can be packaged with HIV-1 Gag particles and released from insect cells.
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PMID:Incorporation of pseudorabies virus gD into human immunodeficiency virus type 1 Gag particles produced in baculovirus-infected cells. 776 63

We report single-point mutations that are located in the matrix protein domain of the gag gene of human immunodeficiency virus type 1 and that prevent Gag particle formation. We show that mutations of p17 that abolish human immunodeficiency virus particle assembly also prevent the dimerization of p17 protein, as measured directly by a protein-protein binding assay. In the three-dimensional structure of p17, mutations that abolish dimerization are located in a single alpha helix that forms part of a fingerlike projection from one side of the molecule. Peptides derived from this region of p17 also reduce the level of p17 dimer when they are added to p17-expressing cells and compete for p17 self-association when present in protein-protein binding assays. We propose that the dimerization of the Gag precursor that occurs by the interdigitation of alpha helices on adjacent matrix molecules is a key stage in virion assembly and that the prevention of such an interaction is the molecular basis of particle misassembly.
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PMID:A molecular determinant of human immunodeficiency virus particle assembly located in matrix antigen p17. 776 15

Productive, spreading infection of peripheral blood lymphocytes (PBL) with human immunodeficiency virus type 1 (HIV-1) requires the viral protein Vif. To study the requirement for vif in this system, we infected PBL with a phenotypically complemented HIV-1 clone mutated in vif. Progeny virus was produced which was noninfectious in PBL but replicated in SupT1 cells. Analysis of metabolically labeled proteins of sedimentable extracellular particles made in PBL by radioimmunoprecipitation with either serum from a patient with AIDS or a monoclonal antibody reactive with HIV-1 Gag proteins revealed that vif-negative but not wild-type particles carry higher levels of p55, p41, and p38 Gag-specific proteins compared with those of p24. Similar results were obtained with sucrose-purified virions. Our data indicate that vif plays a role in Gag protein processing or in incorporation of processed Gag products into mature virions. The presence of unprocessed precursor Gag polyprotein (Pr55gag) and other Gag processing intermediates in PBL-derived vif-negative extracellular particles may contribute to the reduced infectivity of this virus.
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PMID:Aberrant Gag protein composition of a human immunodeficiency virus type 1 vif mutant produced in primary lymphocytes. 776 28

Eighteen rhesus macaques were inoculated with either an infectious molecularly cloned human immunodeficiency virus type 2 (HIV-2)SBL/ISY, or with one of eight mutants defective in one or more accessory genes. The immune responses generated by the macaques were monitored for up to 2 years postinfection. All the macaques except those that received mutants lacking the vpr or vif genes demonstrated low to moderate antibody titers. Macaques inoculated with vpx- mutants exhibited a persistent serological response, suggesting continuous virus expression even in the absence of detectable virus in the peripheral blood mononuclear cells (PBMCs). Neutralizing antibodies developed in only four macaques. In general, low-level cytotoxic T lymphocyte (CTL) activity, not clearly HIV-2 specific, was detected in PBMCs. However, one virus-negative macaque exhibited significant HIV-2-specific CTL activity in an enriched CD8+ cell population from PBMCs, suggesting clearance of the viral infection. In addition, CTL activity against the Env and Gag/Pol epitopes of HIV-2 by CD8+ lymphocytes from the spleens and lymph nodes of two infected macaques, in one case requiring CD8+ T cell enrichment and in the other clearly evident in unfractionated tissue lymphocytes, was demonstrated for the first time. This sequestration of tissue CTLs occurred in the absence of significant levels of circulating CTLs in the blood. Our results suggest that routine monitoring of PBMCs may sometimes be inadequate for detecting cell-mediated immune responses. Elucidation of immune correlates of vaccine protection may therefore require sampling of lymphoid tissues and assessment of enriched CD8+ populations.
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PMID:Humoral and cellular immune responses in rhesus macaques infected with human immunodeficiency virus type 2. 778 83

A chimeric human and simian immunodeficiency virus carrying the tat, rev, vpu, env, and nef genes of human immunodeficiency virus type 1 was generated. The chimeric virus, NM-3n, grew competently in peripheral blood mononuclear cells from cynomolgus monkeys like the parental SIVmac. Two cynomolgus monkeys and one rhesus monkey inoculated with NM-3n raised antibodies to SIVmac Gag and HIV-1 Env. The antibodies raised in the cynomolgus monkeys persisted for at least 1.7 years. The antibodies contained virus neutralizing activity not only to the original chimeric virus but also to the parental HIV-1. Infectious viruses were isolated from one of the cynomolgus monkeys 37 and 63 weeks after inoculation and from the rhesus monkey continuously from 6 weeks after infection onward. The recovered virus maintained its chimeric structure but included several clones with mutations in the env V3 region. When the recovered virus was inoculated to another rhesus monkey, no difference in the frequency of virus recovery was seen from the originally infected monkeys. These carrier monkeys have so far shown no sign of the disease.
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PMID:Persistent infection with SIVmac chimeric virus having tat, rev, vpu, env and nef of HIV type 1 in macaque monkeys. 781 33

We have examined structural interactions between Gag proteins within Moloney murine leukemia virus (M-MuLV) particles by making use of the cysteine-specific cross-linking agents iodine and bis-maleimido hexane. Virion-associated wild-type M-MuLV Pr65Gag proteins in immature particles were intermolecularly cross-linked at cysteines to form Pr65Gag oligomers, from dimers to pentamers or hexamers. Following a systematic approach of cysteine-to-serine mutagenesis, we have shown that cross-linking of Pr65Gag occurred at cysteines of the nucleocapsid (NC) Cys-His motif, suggesting that the Cys-His motifs within virus particles are packed in close proximity. The M-MuLV Pr65Gag protein did not cross-link to the human immunodeficiency virus Pr55Gag protein when the two molecules were coexpressed, indicating either that they did not coassemble or that heterologous Gag proteins were not in close enough proximity to be cross-linked. Using an assembly-competent, protease-minus, cysteine-minus Pr65Gag protein as a template, novel cysteine residues were generated in the M-MuLV capsid domain major homology region (MHR). Cross-linking of proteins containing MHR cysteines showed above-background levels of Gag-Gag dimers but also identified a novel cellular factor, present in virions, that cross-linked to MHR residues. Although the NC cysteine mutation was compatible with M-MuLV particle assembly, deletions of the NC domain were not tolerated. These results suggest that the Cys-His motif is held in close proximity within immature M-MuLV particles by interactions between CA domains and/or non-Cys-His motif domains of the NC.
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PMID:Structural interactions between retroviral Gag proteins examined by cysteine cross-linking. 781 93

The multiple roles of the viral proteinase 2A in poliovirus replication have been difficult to assess because, to date, it has not been possible to isolate and characterize a viral genome with an inactive 2Apro. We have previously reported that a poliovirus replicon containing an inactive 2Apro by virtue of a change at amino acid 109 from a cysteine to a serine (C109S) was replication competent when transfected into cells previously infected with vaccinia virus (R. Pal-Ghosh and C. D. Morrow, J. Virol. 67:4621-4629, 1993). To further develop this system, we have used a poliovirus replicon which contains the human immunodeficiency virus type 1 (HIV-1) gag gene positioned between nucleotides 1174 and 2470 of the poliovirus genome and have engineered a second mutation within this replicon to change the codon for amino acid 109 of the 2Apro from cysteine to serine (2AC109S). Transfection of this replicon into cells previously infected with vaccinia virus results in the replication and expression of a protein with a molecular mass consistent with that of a P1-HIV-1 Gag-2A fusion protein. Using a recently described complementation system which relies on the capacity of a recombinant vaccinia virus (VV-P1) to provide the capsid precursor (P1) in trans (D. C. Ansardi, D. C. Porter, and C. D. Morrow, J. Virol. 67:3684-3690, 1993; and D. C. Porter, D. C. Ansardi, W. S. Choi, and C. D. Morrow, J. Virol. 67:3712-3719, 1993), we have encapsidated this replicon containing the 2AC109S mutation. By using reverse transcription PCR, we demonstrated that after 15 serial passages the encapsidated replicon still contained the 2AC109S mutation. Infection of cells with a stock of encapsidated replicon, either in the presence or in the absence of vaccinia virus, resulted in the expression of the P1-HIV-1 Gag-2A fusion protein. Expression of the P1-HIV-1 Gag fusion protein in cells infected with the encapsidated replicon containing the 2AC109S mutation was reduced compared with the expression of P1-HIV-1 Gag in those cells infected with a replicon containing a wild type 2A gene. The protein expression and replication of the replicon RNA in cells containing the 2AC109S mutation was maintained for a longer period of time than for the replicons containing the wild-type 2A gene, possibly because of a reduced cytopathic effect.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Encapsidation and serial passage of a poliovirus replicon which expresses an inactive 2A proteinase. 781 22

The phenotypes of a series of mutant human immunodeficiency virus type 1 proviruses with linker insertion and deletion mutations within the gag coding region were characterized. These mutants were tested for their ability to make and release viral particles in COS7 cells and for their viability in vivo. Of the 12 mutant proviruses, 4 did not make extracellular virion particles when transfected into COS7 cells. All four of these mutants had mutations in the C-terminal domain of CA. These mutants appeared to have defects both in the ability to accumulate high-molecular-weight intracellular structures containing Gag and Pol products and in the ability to release virion particles. Seven of the mutant proviruses retained the ability to make, release, and process virion particles from COS7 cells. These particles contained the Env glycoprotein, viral genomic RNA, and the mature products of the Gag and Gag-Pol polyproteins, yet they were noninfectious or poorly infectious. The defect in these mutants appears to be in one of the early steps of the viral life cycle. Thus, multiple regions throughout Gag appear to be important in mediating the early steps of the viral life cycle.
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PMID:Linker insertion mutations in the human immunodeficiency virus type 1 gag gene: effects on virion particle assembly, release, and infectivity. 781 27

SDZ NIM 811 is a cyclosporin A analog that is completely devoid of immunosuppressive capacity but exhibits potent and selective anti-human immunodeficiency virus type 1 (HIV-1) activity. The mechanism of action of SDZ NIM 811 is clearly different from those of all other anti-HIV agents described so far. In cell-free assays, it is not an inhibitor of reverse transcriptase, protease, integrase, and it does not interfere with Rev or Tat function. SDZ NIM 811 does not down-regulate CD4 or inhibit fusion between infected and uninfected, CD4-expressing cells. p24 production from chronically HIV-infected cells is not impaired either. To elucidate the mode of action of SDZ NIM 811, we performed DNA PCR analysis in HIV-1 IIIB-infected MT4 cells in one cycle of virus replication. The effects of SDZ NIM 811 on the kinetics of viral DNA synthesis, appearance of two-long terminal repeat circles (2-LTR circles), and integration of DNA were studied. SDZ NIM 811 inhibited 2-LTR circle formation in a concentration-dependent manner, which is indicative of nuclear localization of preintegration complexes. Half-maximal inhibition was achieved at 0.17 microgram/ml; this concentration is close to the 50% inhibitory concentrations (0.01 to 0.2 microgram/ml) for viral growth inhibition. As expected, integration of proviral DNA into cellular DNA was also inhibited by SDZ NIM 811. Analysis of the viral particles produced by SDZ NIM 811-treated, chronically infected cells revealed amounts of capsid proteins, reverse transcriptase activity, and viral RNA comparable to those of the untreated control. However, these particles showed a dose-dependent reduction in infectivity (50% inhibitory concentration of 0.028 microgram/ml) which indicates that the assembly process is also impaired by SDZ NIM 811. Gag proteins are postulated to play a role not only in assembly but also in early steps of viral replication, e.g., nuclear localization of the preintegration complex. Recently, it was reported that HIV-1 Gag protein binds to cyclophilin A, the intracellular receptor for cyclosporin A. Interference with Gag-cyclophilin interaction may be the molecular basis for the antiviral activity of cyclosporin A and its analogs.
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PMID:Mode of action of SDZ NIM 811, a nonimmunosuppressive cyclosporin A analog with activity against human immunodeficiency virus type 1 (HIV-1): interference with early and late events in HIV-1 replication. 781 48

Retroviral proteinase(PR)-catalyzed cleavage of the viral Gag and Gag-Pol polyproteins within the nascent virus particle is required for productive viral infection. Kinetic characterization and specificity analyses have been reported for several retroviral PR using oligopeptide substrates. In this study, we performed a comparative analysis of PR from avian, bovine, simian and human retroviruses using polyproteins of human immunodeficiency virus (HIV) type 1 or avian leukosis virus as substrates. Polyproteins were derived from immature virus-like particles purified from culture medium of transfected or recombinant baculovirus-infected cells. Specific cleavage to the correct size intermediate and end products occurred in the presence of detergent and homologous PR. HIV-1 PR cleaved its Gag precursor to completion at a concentration of approximately 25 nM but cleaved the Gag-Pol precursor incompletely even at fourfold higher PR concentration. In contrast to the requirement for high ionic strength for peptide cleavage reported previously, we found that Gag protein cleavage by HIV-1 PR proceeded best at low ionic strength, for both of the protein substrates tested. HIV-2 PR was approximately sixfold less active than HIV-1 PR. PR from avian myeloblastosis-associated virus (MAV) yielded efficient cleavage of the HIV-1 polyprotein only at concentrations above 1 microM. Both enzymes were stimulated by high salt and their cleavage products were identical or very similar to those of HIV-1 PR. A mutant of MAV PR engineered to cleave HIV-1 peptide substrates did not cleave the HIV-1 polyprotein at a concentration of 0.4 microM. The PR of Mason Pfizer monkey virus cleaved this polyprotein very poorly, whereas PR of bovine leukemia virus cleaved it, albeit at different sites.
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PMID:Proteolytic processing of particle-associated retroviral polyproteins by homologous and heterologous viral proteinases. 788 3


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