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At least 1,405 records · Page 78Linked to original sources
PubMed1997

Induction of the expression of gag protein in HTLV-I infected lymphocytes by anti-ICAM 1 antibody in vitro.

Intercellular adhesion molecule 1 (ICAM 1) is an inducible protein ligand which is up-regulated during inflammation and is either not constitutively expressed or is only expressed at low levels. The expression of ICAM 1 increases in HTLV-I infected T cell lines as well as in CD4+ T-cells of peripheral blood lymphocytes (PBLs) from HAM/TSP patients. After PBLs of HAM/TSP patients were cultured in the presence of stimulating anti-ICAM 1 antibody, the expression of the HTLV-I gag protein in PBLs was observed by both immuno-histostaining and western blot analysis using HTLV-I Ag-specific mouse monoclonal antibody. These data thus suggested that the signal transduction via adhesion molecule, ICAM 1 could induce the transcription of the HTLV-I gene and this might therefore play an important role in the pathogenesis of HAM/TSP.

Adult↗
PubMed2003

10A1-MuLV but not the related amphotropic 4070A MuLV is highly neurovirulent: importance of sequences upstream of the structural Gag coding region.

Recombinants of Moloney murine leukemia virus (MoMuLV) with either an amphotropic (MoAmphoV) or 10A1-tropic host range (Mo10A1V) induce a spongiform neurodegenerative disease in susceptible mice. To test whether MoMuLV -derived sequences are required for induction of neuropathology, mice were inoculated with either the original 10A1 or the amphotropic (4070A) MuLV isolate. Strikingly, wild-type 10A1 was more neurovirulent than Mo10A1V, inducing severe neurological clinical symptoms with a median latency of 99 days in 100% of infected mice. In contrast, no motor disturbances were detected in any of the 4070A-infected mice, although limited central nervous system lesions were observed. A viral determinant conferring high neurovirulence to 10A1 was mapped to a region encompassing the first 676 bases of the viral genome, including the U5 LTR and encoding the amino-terminus of glycosylated Gag (glycoGag). In contrast to studies with the highly neurovirulent CasFr(KP) virus, an inverse correlation between surface expression levels of glycoGag and neurovirulence was not observed; however, this does not rule out a common underlying mechanism regulating virus pathogenicity.

Amino Acid Sequence↗
PubMed1987

Human immunodeficiency virus infection in two cohorts of homosexual men: neutralising sera and association of anti-gag antibody with prognosis.

Sequential sera from 48 subjects infected with human immunodeficiency virus type I (HIV-I) were examined over 36 months for the presence of neutralising antibodies, and for specific anti-gag (p24) and anti-env (gp41) antibodies to HIV-I. Results were interpreted in terms of clinical outcome during the period 1982/3 to 1985/6. HIV-I-infected subjects who remained symptom-free, by comparison with those who manifested AIDS or AIDS-related complex (ARC), had a significantly higher titre of anti-p24 antibodies throughout the 3 years, as measured by competitive enzyme-linked immunosorbent assay and radioimmunoprecipitation. The symptomless subjects also showed a trend towards an increasing neutralising antibody titre with time. There was no relation between anti-gp41 titre and clinical outcome, nor an independent relation between anti-p24 and neutralising titre. A lower or falling titre of anti-p24 antibody was associated significantly with clinical progression, up to 27 months before development of AIDS/ARC.

AIDS-Related Complex↗
PubMed1998

Overlapping epitopes of friend murine leukemia virus gag-encoded leader sequence recognized by single cytotoxic T-lymphocyte clones.

The leader signal sequence of the non-structural gag-encoded glycoprotein precursor, Pr75gag, of Friend murine leukemia virus (F-MuLV) contains overlapping epitopes, SIVLCCLCL (p71-79) and CCLCLTVFL (p75 83) that activate Friend virus (FV)-induced tumor (FBL-3)-specific cytotoxic T-lymphocytes (CTL) (Kondo et al., J. Virol., 69, 1995, 6735-6741; Chen et al., J. Virol., 70, 1996, 7773-7782). It was investigated whether these two peptides are recognized by a single CTL clone or by individual clones with different specificities. The results show that both hydrophobic and cysteine-containing peptides are bound to H-2Db class I major histocompatibility complex (MHC) molecules and cross-recognized by a single CTL clone as well as bulk-cultured CTL from the spleens of mice immunized with FBL-3. The peptide p71-79 was effective for sensitizing target cells to lysis by CTL in the concentration of common antigenic peptides. Moreover, peptide p75-83 was 1000-fold more potent than the peptide p71-79. Specific cytotoxicity assays with variant peptides with alanine- and serine-substitutions suggested a highly complex function of the disulfide bond-forming peptides potentially sensitive to small sequence differences. The dominance of CTL responses to the transmembrane region is discussed in light of the high affinity of a novel hydrophobic peptide to compete with other peptides for binding to MHC molecules.

Amino Acid Sequence↗
PubMed2001

Cellular distribution of bovine leukemia virus proteins gp51SU, Pr72(env), and Pr66(gag-pro) in persistently infected cells.

Monoclonal antibodies (mAbs) against bovine leukemia virus (BLV) mature proteins and precursors were used to map the localization of these proteins in persistently infected non-lymphocytic cell lines using immunofluorescence assay (IFA) and immuno-electron microscopy. IFA staining was observed in the basolateral surface of live FLK-BLV cells. When using a mAb against Pr66(gag-pro), mottled pinpoint fluorescence was seen in the cell surface of polarized cells, but no reaction was observed in cells undergoing mitosis. However, a mAb against Pr72(env) stained only mitotic cells and cellular fragments. Additionally, in these dividing cells, this envelope (Env) precursor polyprotein was not evenly distributed but concentrated predominantly in only one daughter cell. To the best of our knowledge, this observation has not been reported previously, either for BLV or for other retroviruses. The results of immunogold electron microscopy confirmed the specificity of the mAbs in the intracellular level. In infected cells, Pr72(env) and gp51SU were seen in proximity at the plasma membrane in incipient budding sites. Additionally, the mAb against Pr72(env) also reacted with Env precursor polyproteins in the mitochondria of BLV-bat(2) ultrathin sections. These mAbs may be used as a tool for mapping virus excretion sites in the cell surface of naturally or in vitro infected cells in the different stages of the cell cycle.

Animals↗
PubMed2000

Novel anionic microparticles are a potent adjuvant for the induction of cytotoxic T lymphocytes against recombinant p55 gag from HIV-1.

Microparticles with entrapped antigens have recently been shown to possess significant potential as vaccine delivery systems and adjuvants. However, the potential of microparticles as adjuvants has been seriously limited by the common problem of degradation and denaturation of antigens following encapsulation and release. To overcome these problems, we have developed a novel way to use microparticles as adjuvants, by the adsorption of proteins onto their surface. Anionic microparticles were prepared through the inclusion of an anionic detergent, sodium dodecyl sulphate (SDS), in the microparticle preparation process. The anionic microparticles were capable of the efficient and reproducible adsorption of recombinant p55 gag protein from HIV-1. Microparticles with adsorbed p55 were capable of inducing potent cytotoxic T lymphocyte responses in mice following intramuscular immunization. In addition, the microparticles also exhibited a potent adjuvant effect for antibody induction against p55.

Adjuvants, Immunologic↗
PubMed2002

Synergistic adjuvant activity of immunostimulatory DNA and oil/water emulsions for immunization with HIV p55 gag antigen.

A synthetic oligonucleotide containing a previously identified adjuvant active CpG DNA sequence was evaluated for its ability to augment antibody and CTL responses to p55 gag from HIV-1 in mice. Surprisingly, the CpG oligonucleotide, although, it had previously been described as the most potent adjuvant sequence in mice for the particulate HbsAg, was ineffective when used in a simple combination with urea-solubilized p55 antigen. However, a potent adjuvant effect was observed with the CpG sequence when it was formulated with emulsions. Enhancement of antibody titer by CpG emulsion formulations was observed with urea-solubilized p55 antigen, however, significantly higher titers were obtained with p55 bound to polylactide-co-glycolide microparticles. In both cases IgG2a was enhanced in the presence of CpG. It appears likely that presentation of CpG with emulsions and particulate antigens enhances their delivery into antigen presenting cells (APC) and results in more effective presentation of antigen and adjuvant. To support this hypothesis, preliminary in vitro studies were undertaken to show upregulation of CD86 on mouse bone marrow-derived dendritic cells (BMDC) in vitro, following incubation with CpG formulations.

AIDS Vaccines↗
PubMed1998

Delayed progression of murine AIDS in C57BL/6 mice pre-immunized with a highly antigenic 10-mer peptide encoded by the murine AIDS defective virus gag p12 gene.

C57BL/6 (B6) mice were immunized with a highly antigenic 10-mer peptide (P12-10), which is encoded by the murine AIDS (MAIDS) defective virus gag p12 gene, emulsified in incomplete Freund's adjuvant (ICFA). One week later, the mice were inoculated with the MAIDS virus to see if the immunization affects progression of MAIDS. It was demonstrated that the immunization significantly delayed progression of MAIDS, although it failed to induce appreciable cytotoxic T lymphocyte (CTL) responses against the P12-10 antigen. In contrast, immunization of B6 mice with the P12-10 coupled with liposome induced substantial CTL responses but failed to protect the mice against MAIDS development. This segregation between CTL activity and in vivo protection efficacy might be worth considering when we exploit vaccines for augmenting cellular immunity mediated by CD8+ T cells.

Animals↗
PubMed1982

Murine retrovirus genome directs the synthesis of gag protein precursor early after infection.

Incoming type C retroviral genomic 35S RNA is present in polysomes of undifferentiated and differentiated murine teratocarcinoma cell lines at 4 hours after infection. At the same time a 65,000 daltons viral specific protein is produced by the infected cells. These data present evidence that incoming viral RNA serves as messenger for the synthesis of gag protein precursor Pr65 early in the infectious cycle of ecotropic murine retrovirus.

Animals↗
PubMed2000

Contribution of the intercalated adenosine at the helical junction to the stability of the gag-pro frameshifting pseudoknot from mouse mammary tumor virus.

The mouse mammary tumor virus (MMTV) gag-pro frameshifting pseudoknot is an H-type RNA pseudoknot that contains an unpaired adenosine (A14) at the junction of the two helical stems required for efficient frameshifting activity. The thermodynamics of folding of the MMTV vpk pseudoknot have been compared with a structurally homologous mutant RNA containing a G x U to G-C substitution at the helical junction (U13C RNA), and an A14 deletion mutation in that context (U13CdeltaA14 RNA). Dual wavelength optical melting and differential scanning calorimetry reveal that the unpaired adenosine contributes 0.7 (+/-0.2) kcal mol(-1) at low salt and 1.4 (+/-0.2) kcal mol(-1) to the stability (deltaG(0)37) at 1 M NaCl. This stability increment derives from a favorable enthalpy contribution to the stability deltadeltaH = 6.6 (+/-2.1) kcal mol(-1) with deltadeltaG(0)37 comparable to that predicted for the stacking of a dangling 3' unpaired adenosine on a G-C or G x U base pair. Group 1A monovalent ions, NH4+, Mg2+, and Co(NH3)6(3+) ions stabilize the A14 and deltaA14 pseudoknots to largely identical extents, revealing that the observed differences in stability in these molecules do not derive from a differential or specific accumulation of ions in the A14 versus deltaA14 pseudoknots. Knowledge of this free energy contribution may facilitate the prediction of RNA pseudoknot formation from primary nucleotide sequence (Gultyaev et al., 1999, RNA 5:609-617).

Adenosine↗
PubMed1989

Analysis of the ribonuclease H activity of HIV-1 reverse transcriptase using RNA.DNA hybrid substrates derived from the gag region of HIV-1.

The RNase H activity associated with recombinant p66/p51 HIV-1 reverse transcriptase (RT) has been analyzed in the absence of DNA synthesis by using homogeneous RNA.DNA substrates. The substrates consisted of SP6 runoff transcripts from a portion of the gag region of the HIV-1 genome hybridized to complementary single-stranded DNA from either an M13 subclone or a phagemid transcription vector subclone. The corresponding hybrids either carried a 5'-mismatch of seven nucleotides or were fully base-paired. Analysis of recombinant HIV-1 p66/p51 RT by an activated gel assay employing these substrates suggested that the RNase H activity was exclusively associated with the p66 polypeptide. Denaturing gel electrophoresis was used to analyze the oligonucleotide products generated by hydrolysis of the hybrids by HIV-1 RT, M-MuLV RT, and Escherichia coli RNase H. The significant difference in the time-dependent distribution of products of HIV-1 RT vs E. coli RNase H catalyzed cleavage of 5'-mismatched hybrids indicated that the preparation of recombinant HIV-1 RT was free of contaminating bacterial RNase H. Although the HIV-1 RT associated RNase H activity shares many of the general mechanistic features of other retroviral enzymes [Gerard, G. F. (1981) Biochemistry 20, 256-265], the appearance of unique intermediates and end products in the course of hydrolysis of 5'-mismatched and fully base-paired hybrids indicated a significant difference in the sequence dependence of the kinetics of RNase H cleavage by HIV-1 RT and M-MuLV RT.

Base Sequence↗
PubMed1998

Hydrophilic peptides derived from the transframe region of Gag-Pol inhibit the HIV-1 protease.

The HIV-1 transframe region (TFR) is between the structural and functional domains of the Gag-Pol polyprotein, flanked by the nucleocapsid and the protease domains at its N and C termini, respectively. Transframe octapeptide (TFP) Phe-Leu-Arg-Glu-Asp-Leu-Ala-Phe, the N terminus of TFR, and its analogues are competitive inhibitors of the action of the mature HIV-1 protease. The smallest, most potent analogues are tripeptides: Glu-Asp-Leu and Glu-Asp-Phe with Ki values of approximately 50 and approximately 20 microM, respectively. Substitution of the acidic amino acids in the TFP by neutral amino acids and d or retro-d configurations of Glu-Asp-Leu results in an >40-fold increase in Ki. Protease inhibition by Glu-Asp-Leu is dependent on a protonated form of a group with a pKa of 3.8; unlike other inhibitors of HIV-1 protease which are highly hydrophobic, Glu-Asp-Leu is extremely soluble in water, and its binding affinity decreases with increasing NaCl concentration. However, Glu-Asp-Leu is a poor inhibitor (Ki approximately 7.5 mM) of the mammalian aspartic acid protease pepsin. X-ray crystallographic studies at pH 4.2 show that the interactions of Glu at P2 and Leu at P1 of Glu-Asp-Leu with residues of the active site of HIV-1 protease are similar to those of other product-enzyme complexes. It was not feasible to understand the interaction of intact TFP with HIV-1 protease under conditions of crystal growth due to its hydrolysis giving rise to two products. The sequence-specific, selective inhibition of the HIV-1 protease by the viral TFP suggests a role for TFP in regulating protease function during HIV-1 replication.

Amino Acid Sequence↗
PubMed2002

Molecular docking and 3D-QSAR studies on gag peptide analogue inhibitors interacting with human cyclophilin A.

The interaction of a series gag peptide analogues with human cyclophilin A (hCypA) have been studied employing molecular docking and 3D-QSAR approaches. The Lamarckian Genetic Algorithm (LGA) and divide-and-conquer methods were applied to locate the binding orientations and conformations of the inhibitors interacting with hCypA. Good correlations between the calculated interaction free energies and experimental inhibitory activities suggest that the binding conformations of these inhibitors are reasonable. A novel interaction model was identified for inhibitors 11, 15, and 17 whose N-termini were modified by addition of the deaminovaline (Dav) group and the C-termini of 15 and 17 were modified by addition of a benzyl group. Accordingly, two new binding sites (sites A and D in Figure 1) were revealed, which show a strong correlation with inhibitor potency and thus can be used as a starting point for new inhibitor design. In addition, two predictive 3D-QSAR models were obtained by CoMFA and CoMSIA analyses based on the binding conformations derived from the molecular docking calculations. The reasonable r(cross)(2) (cross-validated) values 0.738 and 0.762 were obtained for CoMFA and CoMSIA models, respectively. The predictive ability of these models was validated by four peptide analogues test set. The CoMFA and CoMSIA field distributions are in general agreement with the structural characteristics of the binding groove of hCypA. This indicates the reasonableness of the binding model of the inhibitors with hCypA. Considering all these results together with the valuable clues of binding from references published recently, reasonable pharmacophore elements have been suggested, demonstrating that the 3D-QSAR models about peptide analogue inhibitors are expected to be further employed in predicting activities of the novel compounds for inhibiting hCypA.

Binding Sites↗
PubMed1998

PCR detection of lentiviral GAG segment DNA in the white blood cells of sheep and goats.

A PCR assay for the detection of small ruminant lentiviral gag DNA (provirus) in the white blood cells of sheep and goats was developed and compared with a serological test (AGIDT). A sample of the DNA prepared from the white blood cells in 3 ml of blood from 208 sheep and goats from 18 different flocks was subjected to PCR assay. One of 85 animals from flocks accredited under the Dutch national MVV/CAEV control programme was positive by PCR while none was positive by AGIDT. In infected flocks, the AGIDT appeared slightly more sensitive, but preliminary results show that the sensitivity of the PCR assay may be further improved by increasing the number of monocytes tested. The PCR assay, however, was clearly more sensitive in detecting animals in the early stages of infection. With the use of a set of mixed primers and probes, the assay was able to detect the variety of CAEV and MVV strains occurring in the field.

Animals↗
PubMed1998

Gag-Pol region determines the tropism of SIVagm for human cells.

Simian immunodeficiency virus isolated from African green monkeys (SIVagm) does not grow in many of human cell lines such as CEM x 174, H9, and MT-4, but could replicate in some human cell lines. Sequence of SIVagm responsible for its narrow host range was determined by making and monitoring growth potential of chimeric clones between SIVagm and human immunodeficiency virus type 1 (HIV-1). The results obtained indicated that the gag-pol region determines the observed narrow host range. By monitoring virus DNA synthesis and progeny virion production, the defect(s) of SIVagm in the replication in the restricted cells was demonstrated to be located at early phase.

Animals↗
PubMed2000

Simian retrovirus serogroup 5: partial gag-prt sequence and viral RNA distribution in an infected rhesus macaque.

The simian type D retroviruses (SRVs) are one of the causative agents of simian acquired immunodeficiency syndrome (SAIDS) in Asian macaques. In this report, we describe the infection of a rhesus macaque with the SRV serogroup 5 isolate, D5/RHE/OR. Using reverse transcriptase-polymerase chain reaction (RT-PCR) and dot blot hybridization analyses, we have determined the tissue distribution of D5/RHE/OR in this infected rhesus macaque, and have demonstrated viral mRNA in the majority of the surveyed tissues, including robust loads in the bone marrow, seminal vesicle, submaxillary salivary gland, prostate, and skeletal muscle. Microscopic examination of necropsy tissues revealed generalized lymphoid hyperplasia that was most severe in the salivary gland, bone marrow, kidney, and spleen. We also describe the first sequence analyses of portions of the D5/RHE/OR gag-prt region, obtained as a RT-PCR amplification product from infected rhesus macaque tissue, and report the first confirmation using Northern blot analyses that the SRV serogroups, including D5/RHE/OR, express similarly-sized genomic and subgenomic env mRNAs.

Amino Acid Sequence↗
PubMed2005

Characterization of functional and phenotypic changes in anti-Gag vaccine-induced T cell responses and their role in protection after HIV-1 infection.

Worldwide HIV-1 vaccine efforts are guided by the principle that HIV-specific T cell responses may provide protection from infection or delay overt disease. However, no clear correlates of T cell-mediated immune protection have been identified. Here, we examine in a HLA-B27(+) HIV seronegative vaccinee persistent HIV-specific vaccine-induced anti-Gag CD4(+) and CD8(+) T cell responses. Although these responses exhibited those characteristics (multifunctionality, appropriate memory phenotype, and targeting of epitopes associated with long-term nonprogression) predicted to correlate with protection from infection, the subject became HIV infected. After HIV infection, the vaccine-induced CD8(+) T cells expanded, but both CD4(+) and CD8(+) T cell responses acquired the functional and phenotypic patterns characteristic of chronic HIV infection. The virus quickly escaped the vaccine-induced T cell response, and the subject progressed more rapidly than expected for someone expressing the HLA-B27 allele. These data suggest that control of HIV by vaccine-elicited HIV-specific T cell responses may be difficult, even when the T cell response has those characteristics predicted to provide optimal protection.

AIDS Vaccines↗
PubMed1981

Host restriction of Friend leukemia virus: gag proteins of host range variants.

The host response to murine ecotropic leukemia viruses is mainly controlled by the mouse Fv-1 gene. This locus controls virus replication at an intracellular stage and prevents provirus integration. Biological studies suggest that the Fv-1 effector molecule recognizes at least one virion structural protein. We have produced host range variants of B-tropic Friend murine leukemia virus in order to study the primary structure of potential viral target proteins. Our results show that conversion of B-tropism to NB-tropism is associated with changes in the primary structure of three gag proteins--p15, p12, and p30. These results suggest that host range conversion is due to a recombinational event, presumably between the parental virus and an endogenous murine virus. They also open the possibility that p12 and p30 may be involved in host range restriction.

Amino Acid Sequence↗