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At least 1,063 records · Page 59Linked to original sources
PubMed2004

Influence of CD4+ T cell counts on viral evolution in HIV-infected individuals undergoing suppressive HAART.

We analyzed the viral C2-V4 envelope diversity, glycosylation patterns, and dS/dN ratios of plasma HIV-1 in an attempt to better understand the complex interaction between viral quasispecies and the host-selective pressures pre- and post-HAART. Phylogenetic analysis of the envelope gene of five patients revealed monophyletic clustering in patients with higher CD4+ T cell counts and sequence intermingling in those with lower CD4+ T cells in relation to the stage of HAART. Our analyses also showed clear shifts in N-linked glycosylation patterns in patients with higher CD4+ T cells, suggesting possible distinct immunological pressures pre- and post-HAART. The relative preponderance of synonymous/nonsynonymous changes in the envelope region suggested a positive selection in patients with higher CD4+ T cells, whereas lack of evidence for positive selection was found in the patients with lower CD4+ T cells. An exception to the last analysis occurred in the only patient who reached complete viral suppression, maybe due to drug pressure exerted over the pol gene that may obscure the immune pressure/selection at the envelope in this analysis. All these indications may suggest that even when HAART generates viral suppression, quasispecies evolve in the envelope gene probably resulting from host-selective pressure.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Reversion of a human immunodeficiency virus type 1 matrix mutation affecting Gag membrane binding, endogenous reverse transcriptase activity, and virus infectivity.

We previously characterized mutations in the human immunodeficiency virus type 1 matrix (MA) protein that displayed reduced infectivity in single-round assays, defects in the stable synthesis of viral DNA in infected cells, and impaired endogenous reverse transcriptase activity. The mutants, which contained substitutions in a highly conserved Leu at MA amino acid 20, also increased binding of Gag to membrane. To elucidate further the role of MA in the virus replication cycle, we have characterized a viral revertant of an amino acid 20 mutant (20LK). The revertant virus, which replicates with essentially wild-type kinetics in H9 cells, contains second-site compensatory changes at MA amino acids 73 (E-->K) and 82 (A-->T), while retaining the original 20LK mutation. Single-cycle infectivity assays, performed with luciferase-expressing viruses, show that the 20LK/73EK/82AT triple mutant displays markedly improved infectivity relative to the original 20LK mutant. The stable synthesis of viral DNA in infected cells is also significantly increased compared with that of 20LK DNA. Furthermore, activity of revertant virions in endogenous reverse transcriptase assays is restored to near-wild-type-levels. Interestingly, although 20LK/73EK/82AT reverses the defects in replication kinetics, postentry events, and endogenous reverse transcriptase activity induced by the 20LK mutation, the reversion does not affect the 20LK-imposed increase in Gag membrane binding. Mutants containing single and double amino acid substitutions were constructed, and their growth kinetics were examined. Only virus containing all three changes (20LK/73EK/82AT) grew with significantly accelerated kinetics; 73EK, 73EK/82AT, and 20LK/82AT mutants displayed pronounced defects in virus particle production. Viral core-like complexes were isolated by sucrose density gradient centrifugation of detergent-treated virions. Intriguingly, the protein composition of wild-type and mutant detergent-resistant complexes differed markedly. In wild-type and 20LK complexes, MA was removed following detergent solubilization of the viral membrane. In contrast, in revertant preparations, the majority of MA cosedimented with the detergent-resistant complex. These results suggest that the 20LK/73EK/82AT mutations induced a significant alteration in MA-MA or MA-core interactions.

Amino Acid Sequence↗
PubMedDate not supplied

[The circulation of the California encephalitis complex and Batai viruses in the Lake Baikal region (serological research data)].

The serological materials of the indigenous population and cattle suggest that there are viral foci of a complex of California encephalitis with the circulation of viruses of Inkoo, Tahyna [correction of Tyagin], and the white hare. The results of examining the residents of Irkutsk also suggest that there are urban viral foci of a complex of California encephalitis. The epidemiological potential of the natural foci of Batai virus is insignificant in the Baikal region.

Animals↗
PubMed1994

Secretory pathway function, but not cytoskeletal integrity, is required in poliovirus infection.

We examined the importance of two interactions between poliovirus and its host cell: the putative association between viral proteins and a rearranged intermediate filament (IF) network and the apparent requirement for functional vesicle budding machinery within the host-cell secretory pathway. Poliovirus capsid proteins appeared to associate with reorganized IF proteins during infection. Treatment of cells with cytochalasin D and nocodazole in combination disrupted normal cytoskeletal organization and prevented the poliovirus-induced redistribution of IF proteins to a juxtanuclear location. However, this treatment had no effect on viral yields from single-cycle infections, indicating that neither cytoskeletal integrity nor a specific poliovirus-induced rearrangement of IF proteins is required in the poliovirus life cycle. In contrast, we report that the inhibition of poliovirus replication by brefeldin A (BFA), an inhibitor of secretory membrane traffic, is specific to the host cell. Polioviral yields were not affected by BFA in two BFA-resistant cell lines, demonstrating that BFA targets a host protein or process required by poliovirus. No BFA-resistant virus was detected in these experiments, further supporting the hypothesis that poliovirus replication requires secretory pathway function, perhaps for the generation of vesicles on which viral RNA replication complexes are assembled.

Animals↗
PubMed2006

Ebola virus VP35-VP40 interaction is sufficient for packaging 3E-5E minigenome RNA into virus-like particles.

The packaging of viral genomic RNA into nucleocapsids and subsequently into virions is not completely understood. Phosphoprotein (P) and nucleoprotein (NP) interactions link NP-RNA complexes with P-L (polymerase) complexes to form viral nucleocapsids. The nucleocapsid then interacts with the viral matrix protein, leading to specific packaging of the nucleocapsid into the virion. A mammalian two-hybrid assay and confocal microscopy were used to demonstrate that Ebola virus VP35 and VP40 interact and colocalize in transfected cells. VP35 was packaged into budding virus-like particles (VLPs) as observed by protease protection assays. Moreover, VP40 and VP35 were sufficient for packaging an Ebola virus minigenome RNA into VLPs. Results from immunoprecipitation-reverse transcriptase PCR experiments suggest that VP35 confers specificity of the nucleocapsid for viral genomic RNA by direct VP35-RNA interactions.

Animals↗
PubMed1974

Phosphorylation of vesicular stomatitis virus in vivo and in vitro.

The structural protein, NS, of purified vesicular stomatitis virus (VSV) is a phosphoprotein. In infected cells phosphorylated NS is found both free in the cytoplasm and as part of the viral ribonucleoprotein (RNP) complex containing both the 42S RNA and the structural proteins L, N, and NS, indicating that phosphorylation occurs as an early event in viral maturation. VSV contains an endogenous protein kinase activity, probably of host region, which catalyzes the in vitro phosphorylation of the viral proteins NS, M, and L, but not of N or G. The phosphorylated sites on NS appear to be different in the in vivo and in vitro reactions, and are differentially sensitive to alkaline phosphatase. After removal of the membrane components of purified VSV with a dextran-polyethylene glycol two-phase separation, the kinase activity remains tightly associated with the viral RNP. However, viral RNP isolated from infected cells shows only a small amount of kinase activity. The protein kinase enzyme appears to be a cellular contaminant of purified VSV because an activity from the uninfected cell extract can phosphorylate in vitro the dissociated viral proteins NS and M. The virion-associated activity may be derived either from the cytoplasm or the plasma membrane of the host cell since both of these cellular components contain protein kinase activity similar to that found in purified VSV.

Alkaline Phosphatase↗
PubMed1993

Context-dependent role of human immunodeficiency virus type 1 auxiliary genes in the establishment of chronic virus producers.

Two molecularly cloned viruses, human immunodeficiency virus type 1 (HIV-1)-NL4-3 (NL4-3) and HIV-1-HXB-2 (HXB-2), have been used to study the role of HIV-1 auxiliary genes in the establishment of chronic virus producers. NL4-3 encodes all known HIV-1 proteins, whereas HXB-2 is defective for three auxiliary genes: vpr, vpu, and nef. Studies were done in H9 cells, a T-cell line unusually permissive for the establishment of chronic virus producers. NL4-3 and HXB-2 undergo lytic phases of infection in H9 cultures with HXB-2, but not NL4-3, supporting the efficient establishment of chronic virus producers. Tests of mutant NL4-3 genomes containing various combinations of defective auxiliary genes revealed that both vpr and nef limited the ability of NL4-3 to establish chronic virus producers. Tests of a series of recombinants between NL4-3 and HXB-2 revealed that 5' internal sequences as well as fragments containing defective auxiliary genes affected the establishment of chronic virus producers. Viral envelope sequences and levels of virus production did not correlate with the ability to establish chronic virus producers. These results suggest that complex interactions of viral auxiliary and nonauxiliary gene functions with the host cell determine the ability to establish chronic virus producers.

Cloning, Molecular↗
PubMed1983

RNA polymerase of influenza virus. III. Isolation of RNA polymerase-RNA complexes from influenza virus PR8.

Ribonucleoprotein (RNP) cores with RNA-synthesizing activity were prepared in two fractions, M protein-free and M protein-associated, from detergent-treated influenza virus PR8 by centrifugation through a discontinuous triple gradient of cesium sulfate, glycerol, and NP-40. The M-free RNP was fractionated by phosphocellulose column chromatography into two major RNP forms, A and B, which differed in the content of P proteins, while the M-associated RNP gave only the low P-content Form-B RNP. Starting from the high P-content Form-A RNP, an RNA-P proteins complex virtually free from NP protein was isolated by cesium sulfate equilibrium centrifugation. The complex, containing only three P proteins (P1, P2, and P3), was still active in catalyzing RNA synthesis in vitro without addition of exogenous template, indicating that NP protein is not required for the catalysis of RNA synthesis. RNA synthesis by the isolated RNA-P proteins complex was dependent on either ApG or capped RNA primers, and required four ribonucleoside triphosphates as substrates. The RNA product in this reaction was hybridizable to viral RNA. A complex of one each of the three P proteins was separated from RNA by glycerol gradient centrifugation after ribonuclease treatment or cesium chloride equilibrium centrifugation.

DNA-Directed RNA Polymerases↗
PubMed1981

Vaccinia infection of the nervous system in animals with normal and altered immune reaction.

The outcome of viral infection appears to be the result of a complex interplay of both viral and host factors. The virus-host cell relationship as well as the host's immune response are the major factors determining the type of infection and the expression of the disease. Demyelination disease appears to be rare complication of a systemic viral infection. The mayor factor in its expression is an altered response to the virus favoring the establishment of a noncytocidal abortive infection of the glial cells, which in turn induce a complex of potentially pathogenic immune mechanisms.

Animals↗
PubMed1978

Immunopathologic studies of rheumatoid arthritis. I. Absence of complement-dependent cytotoxicity of rheumatoid sera for rheumatoid synovial cell cultures.

A sensitive complement-dependent chromium release cytotoxicity assay was used to determine whether sera from rheumatoid arthritis (RA) patients contain antibody specific for an antigen on rheumatoid synovial cell cultures. Two hundred eight RA sera-RA synovial culture combinations were studied employing 21 sera and 16 synovial membranes; control combinations were derived from 5 normal sera and 10 degenerative joint disease synovial membranes. Anticomplementary activity of some rheumatoid sera was overcome using an increased complement concentration. The percent cytotoxicity of RA serum-RA culture combinations, both homologous and autologous, was not significantly greater than that of RA serum-control culture combinations. No correlation between duration of disease or duration of cell culture and percent cytotoxicity was found. Thus a unique antigen on cultured rheumatoid synovial cells was not recognized by rheumatoid serum antibody by use of this cytotoxicity assay.

Adolescent↗
PubMedDate not supplied

Chemiluminescence ELISA for the detection of antibodies to bovine leukaemia virus antigens.

A chemiluminescence enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to bovine leukaemia virus antigens (BLV) has been developed. The possibility of using an enhanced chemiluminescence reaction for the determination of adsorbed immunoperoxidase conjugates was studied in this work. The intensity of chemiluminescence depends on both the concentration of reagents and experimental conditions used. The efficiency of the assay is determined by the formation of an immobilized antigen monolayer. A relationship between the quantity of the protein added and adsorbed has been shown. The optimal time and temperature for the antigen-antibody incubation steps have been estimated for each system (3 h at 37 degrees C was chosen as a standard incubation time). A linear dependence of the chemiluminescence intensity and optical density on the concentration of antibodies to the BLV antigens was observed. The detection limit of antibodies in the chemiluminescence ELISA is 2-3 times lower than that in the spectrophotometric one. The results obtained indicate the possibility of using both methods.

Animals↗
PubMed1982

Kinetics of the immune response of tumor-bearing hamsters to two simian virus 40 coded non-structural polypeptides present in simian virus 40 tumor cells.

The kinetics of the immune response of hamsters transplanted with virus-free SV40 tumor cells (TSV5) to two SV40-coded non-structural proteins of 94,000 daltons (T antigen) and 17,000 daltons (t antigen) was studied in order to determine if the variation in the immune reactivity of serum from tumor-bearing animals towards these proteins can be explained on the basis of differential immune response during various stages of tumor growth. The results demonstrate that individual animals vary in their capacity to respond immunologically to T and t antigens in SV40-transformed cells and that, further, the immune response to T and t antigens is influenced by the stage of tumor development.

Animals↗
PubMed1983

Human T-cell leukemia virus type I: induction of syncytia and inhibition by patients' sera.

HTLV-producing T-cell lines induce cell fusion when co-cultivated with a wide variety of indicator cells, suggesting that HTLV envelope antigens interact with the membranes of many cell types. Serum antibodies from adult T-cell lymphoma-leukemia (ATL) patients inhibited the formation of syncytia, and sera from British, American and Japanese ATL patients inhibited cell fusion induced by American and Japanese HTLV isolates equally well. No serological cross-inhibition of syncytium induction was found between HTLV and bovine leukosis virus, Moloney murine leukemia virus and simian sarcoma-associated virus. A simple syncytium inhibition test in microtiter plates has been developed to provide a rapid screen for antibodies presumed to be specific to HTLV envelope glycoproteins.

Animals↗
PubMed1982

Antibodies against a preselected peptide recognize and neutralize foot and mouth disease virus.

A major antibody combining site on foot and mouth disease virus (FMDV) serotype O1K has been identified in a predicted surface helix of viral protein 1 (VP1) between amino acid residues 144 and 159. A hexadecapeptide covering this sequence elicits high titers of antibodies that specifically recognize and neutralize FMDV. The high quality of the immune response is attributed to a particularly stable conformation of the antigenic amino acid sequence, which is most likely an alpha-helix.

Amino Acid Sequence↗