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PubMed1987

Immunoprecipitation of the simian virus 40 late transcription complex with antibody against T-antigen.

Tumor antigen (T-antigen) of simian virus 40 (SV40) has been shown to have a number of regulatory roles in both viral replication and early viral transcription. However, the nature of its role on late viral transcription remains unclear. We have analyzed for the presence of T-antigen on SV40 late viral transcription complexes which exhibit RNA polymerase II extension activity in vitro. Nuclear extract or glycerol gradient-isolated transcription complexes were treated with either polyclonal or monoclonal antibodies, and the amount of extension activity that could be immunoprecipitated was determined. Anti-T antibody derived from hamster ascites as well as the anti-T monoclonal antibodies PAb 102, 109, 416, and 419 all precipitated 12-29% of viral transcription complex activity. Immunoprecipitation resulted in significant enrichment of transcription complex activity relative to bulk minichromosomes, indicating a preferential association of T-antigen with the late viral transcription complex. This is the first direct demonstration of the presence of T-antigen on the SV40 late transcription complex. Furthermore, the immunoprecipitated transcription complexes exhibited a salt dependence of their in vitro extension activity which was distinct from that of the total complex population, indicating that T-antigen is present on a specific subclass of transcription complexes.

Antibodies↗
PubMed2004

Intracellular processing of human herpesvirus 6 glycoproteins Q1 and Q2 into tetrameric complexes expressed on the viral envelope.

Human herpesvirus 6 (HHV-6) glycoproteins H and L (gH and gL, respectively) and the 80-kDa form of glycoprotein Q (gQ-80K) form a heterotrimeric complex that is found on the viral envelope and that is a viral ligand for human CD46. Besides gQ-80K, the gQ gene encodes an additional product whose mature molecular mass is 37 kDa (gQ-37K) and which is derived from a different transcript. Therefore, we designated gQ-80K as gQ1 and gQ-37K as gQ2. We show here that gQ2 also interacts with the gH-gL-gQ1 complex in HHV-6-infected cells and in virions. To examine how these components interact in HHV-6-infected cells, we performed pulse-chase studies. The results demonstrated that gQ2-34K, which is endo-beta-N-acetylglucosaminidase H sensitive and which is the precursor form of gQ2-37K, associates with gQ1-74K, which is the precursor form of gQ1-80K, within 30 min of the pulse period. After a 1-h chase, these precursor forms had associated with the gH-gL dimer. Interestingly, an anti-gH monoclonal antibody coimmunoprecipitated mainly gQ1-80K and gQ2-37K, with little gQ1-74K or gQ2-34K. These results indicate that although gQ2-34K and gQ1-74K interact in the endoplasmic reticulum, the gH-gL-gQ1-80K-gQ2-37K heterotetrameric complex arises in the post-endoplasmic reticulum compartment. The mature complex is subsequently incorporated into viral particles.

Amino Acid Sequence↗
PubMedDate not supplied

Gene delivery into malignant cells in vivo by a conjugated adenovirus/DNA complex.

Current viral delivery systems suffer from disadvantages that may limit the rate at which therapeutic gene expressing constructs can be tested both in vitro and in vivo. In this study, our focus was to develop a simple gene delivery system for the rapid and reproducible testing of therapeutic genes in cancer cells both in vitro and in vivo. We report here that a delivery system based on using a conjugated adenovirus in complex from with a DNA plasmid can be used for not only delivering genes in vitro but also for efficient and reproducible delivery in vivo. Replication defective adenoviral particles were chemically modified by covalent attachment of poly-L-lysine (PLL) to the viral capsid, allowing for direct interaction with DNA. The adenovirus/PLL conjugate (Adv/PLL) was used to deliver the plasmid pCMV/beta-gal to several different cancer cell lines (i.e., lung, cervical) in vitro and resulted in transduction efficiencies as high as 52% as determined by histochemical staining. On direct intralesional injection of the Adv/PLL/DNA complex into subcutaneous tumors, transduction efficiencies greater than 35% could also be achieved. As a result, this system provides a simple method for delivering and testing therapeutic genes in cells both in vitro and in vivo, prior to the further development of gene therapy vectors for both malignant and benign disease.

Adenoviridae↗
PubMed1975

Failure to detect antibody against Gross virus in tetraparental AKR reversible CBA mouse chimaeras.

In spite of early acquisition upon the germ line, tolerance to the Gross (gs) virus is short-lived in the AKR. From about the age of 3 months anti-gs antibodies occur and these complex with the corresponding viral antigens. Such complexes are best seen in the glomeruli by means of immunofluorescence. In marked contrast to the AKR, renal complexes were minimal in a group of AKR reversible CBA/H-T6 chimaeras derived by early embryo aggregation. This was particularly surprising since large numbers of type C murine leukaemia virus-like particles were identified in the chimaeras and the tissues were found to be saturated with gs antigen. The lack of renal antigen-antibody complexes was the first suggestion that anti-gs antibody might not be present in the chimaeras and renal elution studies here support this assumption. In contrast to the AKR where "split " renal eluates have been shown to have anti-gs activity, no activity was demonstrated in eluates from any of the chimaras. Tolerance to the oncogenic Gross virus in the chimaeras has to be attributed to the CBA parental strain component and since this component is also held responsible for the tumour resistance of these chimaeras, both phenomena could well be related. In this context it would appear that in the absence of masking by antibody viral antigenic complexes, tumour specific sites can be recognized in the chimaeras and unlike the AKR "normal" tumour immunity can be effected. This hypothesis is currently bei-ng tested.

AKR murine leukemia virus↗
PubMed1985

Purification and enzymatic properties of an RNA polymerase-RNA complex from influenza virus.

An RNA polymerase-viral RNA complex was purified from influenza A/PR/8 virions by combination of cesium trifluoroacetate centrifugation and phosphocellulose column chromatography. Surface proteins were removed from the detergent-treated virions by the centrifugation. Starting from the M protein-free ribonucleoprotein (RNP) fraction, an RNA polymerase-RNA complex lacking NP protein was isolated by repeated chromatography on phosphocellulose columns. The isolated RNA polymerase-RNA complex, which is composed of PB1, PB2, PA and vRNA, cleaved capped poly(A) endonucleolytically at 10-12 nucleotides from the 5' end and incorporated GMP into the 3' end of the resulting capped fragments. In the presence of all four ribonucleotide triphosphate substrates, the cleaved fragments were elongated to polynucleotides in the absence of exogenous vRNA. The RNA synthesis was primed not only by capped polynucleotides but also dinucleotide ApG. These results indicate that the purified RNA polymerase-RNA complex is as active in viral mRNAs synthesis as native RNP and that NP protein is not required for the catalytic function.

Centrifugation, Isopycnic↗
PubMed1985

Isolation of herpes simplex virus regulatory protein ICP4 as a homodimeric complex.

The viral polypeptide ICP4 (or Vmw175) is synthesized during the immediate early phase of infection by herpes simplex virus and regulates the transcription of delayed early and late viral genes. We obtained a partially purified preparation of soluble ICP4 under nondenaturing conditions. Physical constants for native ICP4 were empirically determined by molecular sieve chromatography and sucrose density gradient ultracentrifugation. The Stokes radius of native ICP4 was 8.72 X 10(-7) cm. The sedimentation coefficient of native ICP4 was 9.00S. From these values, the calculated molecular weight of native ICP4 was 342,000, a value which is twice that of monomeric ICP4, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The failure of any other polypeptides to specifically coprecipitate with native ICP4 in the presence of anti-ICP4 antibody indicates that the 342,000-dalton complex is a homodimer of ICP4. The frictional coefficient ratio of native ICP4, which is 1.9, indicates that the homodimer is a highly elongated molecule.

Animals↗
PubMed2001

Increased soluble Fas in HIV-infected hemophilia patients with CD4+ and CD8+ cell count increases and viral load and immune complex decreases.

Previous studies interpreted increases of soluble Fas (sFas) in the plasma during disease progression in HIV-infected patients as evidence of increased apoptosis of CD4(+) lymphocytes. We studied whether sFas and sFas ligand (sFasL) plasma levels are associated with CD4(+) and CD8(+) lymphocyte counts, plasma viral load, and IgM, IgG, C3d, and gp120 complexes on circulating CD4(+) blood lymphocytes in long-term surviving HIV-infected hemophilia patients, most of whom were receiving HAART. Twenty-six hemophilia patients who were infected with HIV in the early 1980s were investigated in 1997, 1998, and 1999. HAART was initiated in 1996 and 1997 in most patients. Lymphocyte subpopulations and immune complex-coated CD4(+) lymphocytes in the blood were investigated by flow cytometry, plasma viral load (HIV-1 mRNA copies/ml plasma) was tested with HIV-1 QT Nuclisens kits, sFas (ng/ml) and sFasL (ng/ml) plasma levels were measured with MBL ELISA kits, and the in vitro response of patient lymphocytes was tested in cell cultures. During the period from 1997 to 1999 we observed an increase in sFas plasma levels (p = 0.003) as well as in CD4(+) (p = 0.004) and CD8(+) (p = 0.023) cell counts; a decrease in IgG (p = 0.047), C3d (p = 0.024), and gp120 (p = 0.001)-coated CD4(+) lymphocytes in the blood; and a decrease in the number of impaired mitogen stimulation assays (p = 0.013). sFas was negatively associated with viral burden (r = -0.662, p = 0.0002) as well as with CD4(+)IgM(+) (r = -0.554, p = 0.004), CD4(+)IgG(+) (r = -0.431, p = 0.031), CD4(+)C3d(+) (r = -0.551, p = 0.041), and CD4(+)gp120(+) (r = -0.430, p = 0.041) blood lymphocytes, CD8(+)DR(+) cell counts (r = -0.700, p = 0.016), and impaired in vitro responses of patient lymphocytes to PHA (r = -0.475, p = 0.016). sFasL was negatively associated with total lymphocyte counts (r = -0.433, p = 0.027), as well as with absolute numbers of CD3(+) (r = -0.492, p = 0.011) and CD8(+) (r = -0.432, p = 0.027) cells. We conclude that, contrary to expectations, sFas plasma levels increased in long-term surviving HIV-infected hemophilia patients receiving HAART, concomitant with increases in CD4(+) and CD8(+) cell counts. Increased sFas may reflect the growing pool of T lymphocytes that recovers because of a decreasing viral burden and a decreasing immune complex load of CD4(+) lymphocytes.

Antigen-Antibody Complex↗
PubMed1973

Properties of nucleoprotein complexes containing replicating polyoma DNA.

Short-lived nucleoprotein complexes (r-py complex) containing replicating polyoma DNA were isolated from infected cells after lysis with Triton X-100. The Triton lysing procedure of Green, Miller, and Hendler (1971) releases most complexes containing supercoiled viral DNA (py complex) from nuclei, but liberates only a portion of r-py complexes. r-py Complexes are associated more strongly with nuclear sites but can be extracted by prolonged incubation of nuclei in lysing solution. Complexes containing replicating polyoma DNA appear to be precursors to stable complexes containing supercoiled DNA. Sedimentation and buoyant density studies indicate that protein is bound to both r-py complexes and py complexes at a ratio of protein to DNA of about 1 to 2/1. Both types of complexes sediment as if the viral DNA is more compact than free DNA and both undergo major reversible configurational changes with increased salt concentration. Changes resulting from enzymatic and chemical treatment indicate that there may be two or more protein components in both r-py complex and py complex. One component is digested by Pronase and trypsin while another is resistant to the enzymes but released by deoxycholate. The abundance and similarity in chemical and physical properties of protein bound to all forms of polyoma DNA suggest that part of the protein molecules may serve in a structural capacity.

Animals↗
PubMed1997

HIV infection of macrophages and pathogenesis of AIDS dementia complex: interaction of the host cell and viral genotype.

AIDS dementia complex (ADC) develops in only a third of HIV-infected patients who progress to AIDS. Macrophages and microglial cells are the major cellular sites of productive HIV replication in brain. Using 11 blood isolates of HIV from asymptomatic patients there was marked variation in tropism and the level of productive infection in recently adherent monocytes and monocyte-derived macrophages cultured in vitro. However, less variation was seen with 19 blood isolates from advanced HIV infection and 11 postmortem tissue isolates from brain, cerebrospinal fluid, spleen, and lung. Newly adherent monocytes expressed CCR5 in all seven patients tested, consistent with their susceptibility to infection but not explaining the above variability. There is, also marked regional variability in neuropathology in the brain of patients with ADC. We have demonstrated that there was marked variation in the V3 sequences of HIV clones from different regions of the cortex of a patient with ADC, suggesting independent evolution of HIV replication in brain. Furthermore, production of the neurotoxin quinolinic acid from HIV-infected macrophages varied, depending on the host and source of HIV isolate. Hence variations in viral genotype, production by infected macrophages, and subsequent toxin production may contribute to the variability in neuropathology between individuals and between different regions of the brain in the same individual.

AIDS Dementia Complex↗
PubMed1997

The catalytic subunit of the DNA polymerase of herpes simplex virus type 1 interacts specifically with the C terminus of the UL8 component of the viral helicase-primase complex.

The herpes simplex virus type 1 (HSV-1) UL8 DNA replication protein is a component of a trimeric helicase-primase complex. Sixteen UL8-specific monoclonal antibodies (MAbs) were isolated and characterized. In initial immunoprecipitation experiments, one of these, MAb 804, was shown to coprecipitate POL, the catalytic subunit of the HSV-1 DNA polymerase, from extracts of insect cells infected with recombinant baculoviruses expressing the POL and UL8 proteins. Coprecipitation of POL was dependent on the presence of UL8 protein. Rapid enzyme-linked immunosorbent assays (ELISAs), in which one protein was bound to microtiter wells and binding of the other protein was detected with a UL8- or POL-specific MAb, were developed to investigate further the interaction between the two proteins. When tested in the ELISAs, five of the UL8-specific MAbs consistently inhibited the interaction, raising the possibility that these antibodies act by binding to epitopes at or near a site(s) on UL8 involved in its interaction with POL. The epitopes recognized by four of the inhibitory MAbs were approximately located by using a series of truncated UL8 proteins expressed in mammalian cells. Three of these MAbs recognized an epitope near the C terminus of UL8, which was subjected to fine mapping with a series of overlapping peptides. The C-terminal peptides were then tested in the ELISA for their ability to inhibit the POL-UL8 interaction: the most potent exhibited a 50% inhibitory concentration of approximately 5 microM. Our findings suggest that the UL8 protein may be involved in recruiting HSV-1 DNA polymerase into the viral DNA replication complex and also identify a potential new target for antiviral therapy.

Amino Acid Sequence↗
PubMed2003

Virus subversion of the MHC class I peptide-loading complex.

Many viral proteins modulate class I expression, yet, in general, their mechanisms of specific class I recognition are poorly understood. The mK3 protein of gamma(2)-Herpesvirus 68 targets the degradation of nascent class I molecules via the ubiquitin/proteasome pathway. Here, we identify cellular components of the MHC class I assembly machinery, TAP and tapasin, that are required for mK3 function. mK3 failed to regulate class I in TAP- or tapasin-deficient cells, and mK3 interacted with TAP/tapasin, even in the absence of class I. Expression of mK3 resulted in the ubiquitination of TAP/tapasin-associated class I, and mutants of class I incapable of TAP/tapasin interaction were unaffected by mK3. Thus, mK3 subverts TAP/tapasin to specifically target class I molecules for destruction.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

E1A repression of IL-6-induced gene activation by blocking the assembly of IL-6 response element binding complexes.

Some viral products interfere with host antiviral defense mechanisms. Adenovirus E1A represses IFN signal transduction pathways which induces gene activation and an antiviral state. Both IFN and IL-6 activate Jak/Tyk protein tyrosine kinases and the STAT (signal transducer and activator of transcription) family proteins. We showed that 12S E1A repressed IL-6 signals activating the junB promoter and the two IL-6 response elements (REs), JRE-IL6 and type II IL-6 RE (also called acute phase response element), required for IL-6-induced activation of the junB promoter and the type II acute phase reactant genes, respectively, in hepatocytes. Conserved region 1 of the 12S E1A was responsible for the repression. Target molecules of the repression by E1A appeared to be IL-6-inducible DNA-binding proteins acting on the IL-6 REs. In a rat 3Y1 cell line stably expressing E1A, the levels of IL-6-induced IL-6 RE binding proteins were severely reduced compared with those in a parental 3Y1 cell line. Moreover, we found that the levels of the STAT family proteins including Stat1-alpha (p91), Stat1-beta (p84), Stat2 (p113), and Stat3 were decreased by the stable expression of adenovirus E1A. The E1A-induced reduction in the amount of DNA-binding proteins seemed to be partly responsible for the decreased transcriptional activity of the IL-6 RE-driven gene expression in response to IL-6. This repression mechanism may be applicable to the E1A repression of IFN-gamma-induced gene activation.

Adenovirus E1A Proteins↗
PubMed1991

Nonconventional (TL-encoded) major histocompatibility complex molecules present processed viral antigen to cytotoxic T lymphocytes.

A large number of class I-like genes are located distal to the K and D regions of the murine major histocompatibility complex (MHC) within the Q and TL region. The function of the molecules encoded within this region is obscure since unlike conventional MHC gene products, these molecules have not been reported to present processed environmental antigens to T cells. In the present report, we demonstrate that a peptide corresponding to processed influenza virus hemagglutinin can be recognized by CD8+ T cell receptor alpha/beta-positive cytotoxic T lymphocytes (CTL) in association with a MHC class I-like product encoded within the TL region. Thus, nonconventional class I MHC molecules can bind and present processed environmental antigens, and TCR-alpha/beta CTL directed to such peptide MHC complexes are represented in the mature T cell pool. Our data imply that Q/TL region products may be charged by peptides generated through an antigen processing and presentation pathway distinct from the pathway used by conventional MHC molecules and not normally available to environmental antigens.

Amino Acid Sequence↗
PubMed1982

Participation of the major histocompatibility complex in antibody recognition of viral antigens expressed on infected cells.

The capacity of the antibody repertoire to recognize complex antigens on viral-infected cells was investigated at the level of monoclonal B cell responses. A majority of primary B cells responsive to PR8(H1N1)-infected H-2 syngeneic cells produced antibody that bound viral determinants only in the context of infected cells and not the isolated virion. An examination of the fine specificity of such antibodies revealed that most could be distinguished by a panel of cells infected with closely related heterologous H1 influenza strains. Indeed, most antibodies bound hemagglutinin determinants of PR8 exclusively, and few were broadly cross-reactive. An examination of the same antibodies for their recognition of cell surface antigens revealed that the majority recognized MHC-encoded antigenic determinants. Thus, most BALB.K (H-2k) primary B cells responsive to PR8-L919 (H-2k) cells produced monoclonal antibodies that bound PR8-antigens only in the context of H-2Dk-infected cells. Most C57BL/10 (H-2b) B cells responsive to PR8-EL4 (H-2b) cells produced monoclonal antibodies that bound PR8 antigens only in the context of H-2Kb-infected cells. These latter antibodies were further shown to recognize that H-2Kb molecule by virtue of their capacity to be discriminated by a panel of PR8-infected H-2Kb mutant cells. These findings demonstrate that much of the antibody repertoire is capable of highly specific complex recognition of viral antigenic determinants in the context of the appropriate MHC alloantigen.

Animals↗
PubMed2004

Intracellular localization and protein interactions of the gene 1 protein p28 during mouse hepatitis virus replication.

Coronaviruses encode the largest replicase polyprotein of any known positive-strand RNA virus. Replicase protein precursors and mature products are thought to mediate the formation and function of viral replication complexes on the surfaces of intracellular double-membrane vesicles. However, the functions of only a few of these proteins are known. For the coronavirus mouse hepatitis virus (MHV), the first proteolytic processing event of the replicase polyprotein liberates an amino-terminal 28-kDa product (p28). While previous biochemical studies have suggested that p28 is associated with viral replication complexes, the intracellular localization and interactions of p28 with other proteins during the course of MHV replication have not been defined. We used immunofluorescence confocal microscopy to show that p28 localizes to viral replication complexes in the cytoplasm during early times postinfection. However, at late times postinfection, p28 localizes to sites of M accumulation distinct from the replication complex. Furthermore, by yeast two-hybrid and coimmunoprecipitation analyses, we demonstrate that p28 specifically binds to p10 and p15, two coronavirus replicase proteins of unknown function. Deletion mutagenesis experiments determined that the carboxy terminus of p28 is not required for its interactions with p10 and p15. These results suggest that p28 may play a part at the replication complex by interacting with p10 and p15. Moreover, our findings highlight a potential role for p28 at virion assembly sites.

Animals↗
PubMed1982

Monoclonal radioimmunoassays for hepatitis B surface antigen: demonstration of hepatitis B virus DNA or related sequences in serum and viral epitopes in immune complexes.

High-affinity monoclonal IgM and IgG antibodies (anti-HBs) to hepatitis B surface antigen (HBsAg) have recently been developed and used by us in the construction of highly sensitive radioimmunoassays for the detection of HBsAg-associated determinants in serum. We now report that selected serum samples demonstrating monoclonal immunoreactive material also contain nucleic acid sequences complementary to hepatitis B virus (HBV) DNA by molecular hybridization analysis. In addition, monoclonal radioimmunoassays can detect viral determinants in HBsAg-anti-HBs immune complexes formed in anti-HBs excess; such determinants are undetectable by commercial radioimmunoassay. These and our previous studies suggest that there are HBV or "HBV-related" agents present in human serum that are detected by monoclonal antibodies but are not identified by conventional polyvalent antibodies.

Antibodies, Monoclonal↗