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Biomedical subjects

L Thibodeau

Publications and source records attributed to L Thibodeau.

32 records · Page 2Linked to original sources
PubMed1987

The association of the rabies glycoprotein with liposome (immunosome) induces an in vitro specific release of interleukin 2.

BALB/c mice were primed by receiving a unique intraperitoneal injection of rabies virus antigens presented as complete inactivated virus (P.V. strain) or as purified glycoproteins either in the aggregated form or in physical combination with liposomes (i.e., in the form of "immunosomes"). The splenocytes of these mice were restimulated, 6-15 days after priming, in culture with rabies virus antigens, and antigen-specific IL-2 production was measured. It was found that rabies antigens presented as immunosomes were as active as the inactivated virus, whereas equivalent amounts of purified glycoproteins were inactive. The optimal amounts of rabies immunosomes used for priming was found to be 0.5 to 0.05 micrograms per mouse.

Animals↗
PubMed1986

Specific adherence of thymocytes to a thymic medullary epithelial cell line.

TMF, a glycoprotein found preferentially at the contact points between thymocytes and thymic medullary epithelial cells, was investigated for its participation in adherence between these two cell types. It was found that thymocytes adhere specifically to a TMF+ cell line, that anti-TMF antibody can inhibit the adherence and that extraneous TMF can effectively compete with the adherence reaction. It is concluded that TMF is indeed involved in the temporary contact which occurs between thymocytes and medullary epithelial cells.

Animals↗
PubMed1985

Mouse response to influenza immunosomes.

Immunosome preparations consisting of surface glycoproteins, extracted from five influenza virus strains and anchored onto performed liposomes, were tested in mice. Serum antibody responses were essentially similar to those elicited by whole virus vaccines and higher than responses induced by subunit preparations. Antibody titres were assessed by haemagglutination-inhibition technique. Survival of mice immunized with 6 micrograms haemagglutinin of attenuated, inactivated, subunit or immunosome A/Aichi/2/68 vaccines and later challenged with variants of the same subtype was also assessed. All vaccine preparations induced similar percentage survival when mice were challenged with variants prevalent from 1968 to 1977. However, the attenuated vaccine induced a significant higher protection level against the 1979 variant.

Animals↗
PubMed1985

Rabies immunosome (subunit vaccine) structure and immunogenicity. Pre- and post-exposure protection studies.

Rabies immunosomes (glycoprotein anchored on pre-formed liposomes) have been prepared in order to study their structural, biological and immunological properties. The glycoprotein molecules appear to have the same orientation on the immunosome as on the viral particle: (1) electron microscopy analysis shows particles of 40 to 70 nm with spikes protruding outward, (2) one particular epitope shows the same accessibility to a neutralizing monoclonal antibody as on the viral particle. When injected into animals, rabies immunosomes are cleared from the organism by a process different from that for the liposomes used to anchor the glycoprotein: a higher rate of transition through the spleen is observed with immunosomes than with purified glycoprotein or liposomes. Immunosomes induce high levels of neutralizing antibodies and protect animals against challenge with virulent strains. This protective activity is not altered after several months of storage at 4 degrees C. Furthermore, rabies immunosomes were shown to be efficient in post-exposure treatment of laboratory animals that had been experimentally infected with a lethal dose of a rabies wild strain.

Animals↗
PubMed1985

Structural and immunogenic characteristics of rabies immunosomes.

Rabies immunosomes are prepared by the anchorage of glycoprotein molecules to preformed liposomes. Virosomes are associations of glycoprotein molecules with viral or non viral lipids. Virosomes can be obtained spontaneously after removal of the detergent used for lipids solubilization. Under the electron microscope immunosomes look like homogenous spherical vesicles (50-60 nm) evenly covered with spikes, although glycoprotein molecule orientation in virosomes is not yet clearly established. In addition, the size of virosomes is very heterogeneous. When glycoprotein molecules are in immunosome form, their accessibility to a lectin (WGA) is identical to that of the purified virus. Under the same conditions with virosomes accessibility is weaker. Protection induced in mice is ten to twenty fold higher with rabies immunosomes than with purified glycoprotein or virosomes. The results presented here and previous reports (10) show that immunosomes have structural and immunogen characteristics closer to those of purified and inactivated virus than does any other form of glycoprotein lipids association.

Animals↗
PubMed1984

Studies of the antigenic variation in poliovirus type 1. Selection and analysis of variant strains with monoclonal antibodies by neutralization.

Nine neutralizing monoclonal antibodies were used in a preliminary study of the antigenic variation of poliovirus type 1. Six antigenic variants were selected and five distinct epitopes involved in neutralization were identified. Four of these epitopes are thought to be clustered within a single antigenic site. In kinetic studies, the neutralization of poliovirus by monoclonal antibodies was shown to be a single hit process.

Animals↗
PubMed1980

Purification and properties of the major apurinic/apyrimidinic endodeoxyribonuclease of rat-liver chromatin.

Two nucleases active on alkylated-depurinated DNA have been extracted from rat liver chromatin with 1 M KCl. The major enzyme was purified to near homogeneity; it has a molecular weight of 12 500 (although some dimerization might occur), needs Mg2+ or Mn2+ for activity. The endonuclease activity is specific for apurinic/apyrimidinic sites in DNA; the enzyme has no associated exonuclease activity.

Animals↗
PubMed1980

Cellular localization of the apurinic/apyrimidinic endodeoxyribonucleases in rat liver.

A method has been developed to purify rat liver nuclei; the isolated nuclei keep both nuclear membranes and retain more than 90% of the cell apurinic/apyrimidinic (AP) endodeoxyribonuclease activity. The nuclear enzyme is located mostly in chromatin non-histones; there is also an important amount of activity in the nuclear sap and some in the nuclear membranes. The cytoplasmic AP endodeoxyribonuclease activity is shared between mitochondria, cytosol and membranes. Different cell compartments appear to contain different AP endodeoxyribonuclease species: the membrane enzyme is activated by Triton whereas the other enzymes are rather inhibited; the nuclear sap enzyme has a higher molecular weight and a higher thermal resistance than the chromatin enzyme. A hypothesis is formulated according to which: (1) the chromatin enzyme is the only species important for nuclear DNA repair; (2) the species present in the other cell compartments might be precursors of the chromatin AP endodeoxyribonuclease.

Animals↗
PubMed1977

Purification and properties of a plant endonuclease specific for apurinic sites.

An endonuclease which hydrolyzes depurinated DNA has been isolated from Phaseolus multiflorus enbryos; it has a molecular weight around 40,000. The enzyme is specific for apurinic sites; it has no action on normal DNA strands or on alkylated sites, and is without exonulcease activity. The rate of phosphoester bond hydrolysis near apurinic sites is far greater in native than in denatured DNA. The endonuclease is not inactivated by 10 mM EDTA, but is activity is however stimulated by Mg2+ or Mn2+. Its optimum pH is 7.5 to 8.0, and its optimum temperature 40degrees although, at this temperature, it is rapidly denatured; even low NaCl concentrations inhibit the enzyme activity. The endonuclease for apurinic sites of P. multiflorus is a non-histone protein of chromatin; the properties (like thermosensitivity of susceptibility to ionic strength) of the enzyme in situ, working on chromatin DNA, might be different from those described for the isolated endonuclease in homogenous aqueous solution.

Alkylation↗
PubMed1976

Inactivation of the T7 coliphage by monofunctional alkylating agents. Action of phage adsorption and injection of its DNA.

Alkylation by ethyl or methyl methanesulfonate to an extent that inactivates more than 99.5% of T7 coliphages has no effect on phage adsorption on Escherichia coli B cells, but decreases the amount of phage DNA injected into the host cells. Depurination interferes with the injection of the phage DNA. Failure to inject the whole phage genome thus appears to be a cause of the immediate as well as of the delayed inactivation of the T7 coliphage treated by monofunctional alkylating agents; the hypothesis that it is the only cause of inactivation, although not very likely, cannot be excluded at the present time.

Binding Sites↗