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

In previous studies, we demonstrated that the substitution of amino acid triplets for alanines in the carboxy-terminal portion (amino acids 341-352: ATL EEM MTA CQC) of the capsid protein domain (p24) of human immunodeficiency virus type 1 (HIV-1) partly led to an inhibitory effect on the capacity to form virus-like particles (VLPs). In these experiments, the uncleaved Pr55gag precursor protein was expressed by recombinant vaccinia viruses. We have now investigated the effects of these mutations with respect to a replication-competent HI-provirus system. Substitution of amino acids 344-346 (EEM) for alanines, which was previously shown to lead to an inhibition of VLP formation, completely blocked assembly and release of HIV. A substantial reduction of HIV synthesis was also observed in the proviral system after exchange of amino acids 347-348 [MT(A)] which, in contrast, was formerly shown to result in an increased formation of VLPs. Western blot analysis of lysates of cells transfected with these mutated proviral constructs revealed an abnormal intracellular processing pattern of the Pr55gag precursor molecules. Further analyses suggest a structural aberration of these altered polyproteins as the basis for the observed block of virus formation.
 ...
PMID:Inhibition of human immunodeficiency virus type 1 particle formation by alterations of defined amino acids within the C terminus of the capsid protein. 934 69

A mutant of human immunodeficiency virus type 1 (HIV-1), which is deficient for Gag precursor cleavage and noninfectious, was characterized with respect to its defective step in the viral replication phase. Upon transfection, the mutant produced a normal level of progeny virions as monitored by electron microscopy and RNA hybridization. Single-round replication assay demonstrated, in contrast, that the mutant was defective at the early phase of the replication cycle. Furthermore, no viral DNA was detected in the cells infected with the mutant. Taken together, it is concluded that maturation of Gag precursor protein of HIV-1 is required for an early event(s) before or during a coupled process of uncoating/reverse transcription.
 ...
PMID:Cleavage of Gag precursor is required for early replication phase of HIV-1. 935 Oct 1

Several monoclonal antibodies (mAbs) were produced against feline immunodeficiency virus (FIV) p24 capsid antigen. One of these, F2710, reacted strongly, not only with viral p24 and recombinant p24, but also with p50 Gag precursor protein in Western blot. Epitope mapping analysis revealed that mAb F2710 recognizes a heptapeptide, SFIDRLF, in the FIV p24 amino acid sequence. As this portion of FIV p24 is highly conserved among various FIV strains, the mAb seems to be a useful tool for detecting FIV p24 antigen in various samples. By means of this mAb and rabbit anti-p24 polyclonal antibody, an antigen capture ELISA was developed. The ELISA detected viral p24 antigen with good linearity. The lower detection limit of this assay is 40 pg/ml of recombinant p24 antigen, which is at least as sensitive as the reverse transcriptase assay in detecting FIV virion. Thus, this system is valuable for monitoring FIV replication in vitro.
 ...
PMID:Characterization of one monoclonal antibody against feline immunodeficiency virus p24 and its application to antigen capture ELISA. 938 8

Effort to develop a vaccine to prevent infection of human immunodeficiency virus (HIV) have focused on the induction of neutralizing antibodies. In our previous study, we reported that chimeric gag-env virus-like particles (VLPs) induce neutralizing antibodies which block HIV infection. In addition to the neutralizing antibodies, the cytotoxic T-lymphocyte (CTL) response is considered to be another major immune defense mechanism required for recovery from many different viral infections. In the present study, we have constructed chimeric fusion proteins using HIV-2 gag precursor protein with (1) four neutralizing epitopes from HIV-1 gp160; (2) three tandem copies of consensus V3 domain, which have been derived from 245 different isolates of HIV-1 and carries both the principal neutralizing determinant (PND) and CTL epitopes; and (3) V3 domains from HIV-1IIIB, HIV-1MN, HIV-1RF, and HIV-1SF2. These chimeric fusion proteins were expressed in a large quantity within insect cells, and released as VLPs into the cell culture medium. The purified gag-env VLPs from all three constructs appear to be spherical particles similar to immature HIV but slightly larger than the gag VLPs. Immunoprecipitation analysis showed that the chimeric proteins were recognized not only by HIV-1 positive patient sera, but also by monoclonal and polyclonal antisera raised against V3 peptides of HIV-1IIIB, HIV-1MN, HIV-1RF, and the gp120 antiserum against HIV-1SF2. Balb/C mice immunized with these chimeric VLPs successfully induced CTL activity against V3 peptide-stimulated target cells. In addition, a high degree of cross-reactivity was observed among the four different strains of HIV-1 V3 domain, indicating that the tandem multiple consensus V3 peptide sequence carried by HIV-2 gag can be used as a potential HIV vaccine against various HIVs.
 ...
PMID:Induction of V3-specific cytotoxic T lymphocyte responses by HIV gag particles carrying multiple immunodominant V3 epitopes of gp120. 945 5

The role of the integrase region of feline immunodeficiency virus (FIV) in viral replication was examined using an integrase mutant clone of FIV which carries a frameshift mutation in the region. Upon transfection, although the integrase mutant was able to release virus-like particles into the supernatant from the transfected cells, the virions produced by the mutant contained unprocessed gag precursor protein and undetectable levels of reverse transcriptase activity. Furthermore, the mutant virions were unable to direct the synthesis of viral DNA after infection in target cells. To understand this phenotype of the integrase mutant in more detail, we constructed a gag-pol expression plasmid from an FIV molecular clone and assayed roles of the integrase region on virus particle formation following transfection. When an inframe deletion was introduced into the protease region of the expression plasmid, the mutant was able to efficiently release gag- and gag-pol precursor proteins into the supernatant from the transfected cells. An expression plasmid with mutations in both the protease and integrase regions, however, failed to release the gag-pol precursor protein from the cells. These results suggested an essential role for the integrase region for efficient incorporation of the gag-pol precursor into the virions.
 ...
PMID:Characterization of an integrase mutant of feline immunodeficiency virus. 950 62

We have studied the effect of mutations in the human immunodeficiency virus type 1 (HIV-1) nucleocapsid (NC) sequence on tRNA(3Lys) genomic placement, i.e., the in vivo placement of primer tRNA(3Lys) on the HIV-1 primer binding site (PBS). HIV-1 produced from COS cells transfected with wild-type or mutant proviral DNA was used in this study. We have found that mutations in the amino acid sequences flanking the first Cys-His box in the NC sequence produce the maximum inhibition of genomic placement. A similar finding was obtained when the NC-facilitated annealing of primer tRNA(3Lys) to the HIV PBS in vitro was studied. However, since the genomic placement of tRNA(3Lys) occurs independently of precursor protein processing, the NC mutations studied here have probably exerted their effect through one or both of the precursor proteins, Pr55gag and/or Pr160(gag-pol). One mutation in the linker region between the two Cys-His boxes, P31L, prevented packaging of both Pr160(gag-pol) and tRNA(3Lys) and prevented the genomic placement of tRNA(3Lys). Both packaging and genomic placement were rescued by cotransfection with a plasmid coding for wild-type Pr160(gag-pol). For other linker mutations [R7R10K11 S, R32G, and S3(32-34)], packaging of Pr160(gag-pol) and tRNA(3Lys) was not affected, but genomic placement was, and placement could not be rescued by cotransfection with plasmids coding for either Pr55gag or Pr160(gag-pol). After placement, the initiation of reverse transcription within extracellular virions is characterized by a 2-base DNA extension of the placed tRNA(3Lys). This process requires precursor processing, and those NC mutations which showed the most inhibition of initiation were in either of the two NC Cys-His boxes. Destabilization of a U5 stem-A-rich loop immediately upstream of the PBS (through deletion of four consecutive A's in the loop) did not affect the in vivo genomic placement of tRNA(3Lys) but resulted in the presence in the extracellular virus of longer cDNA extensions of tRNA(3Lys), with a corresponding decrease in the presence of unextended and 2-base-extended tRNA(3Lys).
 ...
PMID:The role of nucleocapsid and U5 stem/A-rich loop sequences in tRNA(3Lys) genomic placement and initiation of reverse transcription in human immunodeficiency virus type 1. 955 76

We constructed a deletion mutant of feline herpesvirus type 1 (FHV-1) and a recombinant FHV-1. The deletion mutant is the virus with a region (367 bp) deleted from the start codon of thymidine kinase (TK) gene to the SmaI site within the TK gene, and the other is a recombinant FHV-1 expressing Gag protein of feline immunodeficiency virus (FIV), in which a cDNA encoding the Gag protein of FIV was inserted at the TK deletion site of the former deletion mutant. These viruses were designated as C7301ddlTK and C7301ddlTK-gag, respectively. Growth kinetics of these viruses in Crandell feline kidney cells was similar to that of the parent C7301 strain. By immunoblot analysis, C7301 ddlTK-gag was confirmed to express the FIV Gag precursor protein in the cells.
 ...
PMID:Construction of a recombinant feline herpesvirus type 1 expressing Gag precursor protein of feline immunodeficiency virus. 957 47

Previously we demonstrated that murine retroviral Gag proteins associate with a cellular motor protein, KIF-4. Using the yeast two-hybrid assay, we also found an association of KIF-4 with Gag proteins of Mason-Pfizer monkey virus (MPMV), simian immunodeficiency virus (SIV), and human immunodeficiency virus type 1 (HIV-1). Studies performed with mammalian cell systems confirmed that the HIV-1 Gag protein associates with KIF-4. Soluble cytoplasmic proteins from cells infected with recombinant vaccinia virus expressing the entire Gag-Pol precursor protein of HIV-1 or transfected with HIV-1 molecular clone pNL4-3 were fractionated by sucrose gradient centrifugation and further separated by size-exclusion and anion-exchange chromatographies. KIF-4 and HIV-1 Gag cofractionated in both chromatographic separations. Immunoprecipitation assays have also verified the KIF-4-Gag association. KIF-4 binds mainly to the Gag precursor (Pr55 Gag) and a matrix-capsid processing intermediate (Pr42) but not to other processed Gag products. The binding of Gag is mediated by a domain of KIF-4 proximal to the C terminus. These results, and our previous studies, raise the possibility that KIF-4 may play an important role in retrovirus Gag protein transport.
 ...
PMID:Cellular motor protein KIF-4 associates with retroviral Gag. 1055 69

A key stage in the life cycle of C-type retroviruses is the assembly of Gag precursor protein at the plasma membrane of infected cells. Here we report the assembly of bovine leukemia virus (BLV) gag gene product into virus-like particles (VLPs) using the baculovirus expression system. Expression of BLV Pr44(Gag) resulted in the assembly and release of VLPs, thereby confirming the ability of retroviral Gag polyprotein to assemble and bud from insect cells. Efficient particle formation required a myristoylation signal at the N-terminus of BLV Pr44(Gag). Recombinant baculoviruses expressing matrix (MA) or capsid-nucleocapsid (CA-NC) proteins of BLV were generated but neither of these domains was capable of assembling into particulate structures. To assess the compatibility of Gag domains between leukemia and lentivirus groups three different recombinant chimeras each expressing MA of one virus (e.g., simian immunodeficiency or BLV) and CA-NC of another (e.g., BLV or human T-cell leukemia virus type-I) were constructed. Each of the chimeric proteins assembled efficiently and budded as VLPs, suggesting that the MA and CA domains of these two evolutionary divergent retrovirus groups can be functionally exchanged without perturbation of Gag VLP formation. The lenti-leukemia chimeric Gag approach has potential for studying protein-protein interactions in other retroviruses.
 ...
PMID:Bovine leukemia virus Gag particle assembly in insect cells: formation of chimeric particles by domain-switched leukemia/lentivirus Gag polyprotein. 1060 Jun 2

Human immunodeficiency virus (HIV) and equine infectious anemia virus (EIAV) are closely related lentiviruses that infect immune cells, but their pathogenesis differ. Localization to the cytosolic leaflet of the plasma membrane is critical for replication of both viruses. This localization is accomplished through the matrix (MA) domain of the Gag precursor protein. In HIV-1, association of MA to anionic membranes appears to be primarily driven by a linear cluster of basic residues in the MA domain and an N-myristoylation signal. Interestingly, the MA protein of EIAV does not contain either of these signals. To understand which factors could promote EIAV assembly we characterized the membrane binding properties of its MA protein using fluorescence and biochemical methods. We find that EIAV MA exists as a multimer in solution whose protein-protein interactions are destabilized by membrane binding. EIAV MA binds strongly to electrically neutral membranes as well as to negatively charged membranes. Fluorescence quenching and chemical modification techniques, as well as trypsin proteolysis, indicate a different exposure of the EIAV MA Trp residues when bound to the two types of membranes, and EIAV MA proteolysis by trypsin differs when bound to the two types of membranes. Based on these data and the known structures of closely related matrix proteins, we constructed a structural model. This model predicts that EIAV MA binds to negatively charged membranes, but EIAV MA has an additional membrane binding region rich in residues that partition favorably into the membrane headgroup region. This secondary site may play a role in early events of viral infection.
 ...
PMID:Binding of equine infectious anemia virus matrix protein to membrane bilayers involves multiple interactions. 1067 89


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>