Search PubMed⌕ Search

Biomedical subjects

L Leserman

Publications and source records attributed to L Leserman.

27 records · Page 2Linked to original sources
PubMed1990

Antibody-targeted liposomes containing oligodeoxyribonucleotides complementary to viral RNA selectively inhibit viral replication.

Mouse L929 cells were incubated with antibody-targeted liposomes containing oligodeoxyribonucleotides (oligomers). When the oligomer was a 15-mer complementary to the 5'-end region of the mRNA encoding the N protein of vesicular stomatitis virus, the cells became less permissive for multiplication of that virus; greater than 95% reduction of viral multiplication was achieved. Protection was not seen for "empty" liposomes, liposomes containing a random oligomer sequence, or liposomes containing a sequence complementary to the 5' end of c-myc protooncogene mRNA targeted by the same antibody, nor was it seen when the liposomes containing the N-protein antisense oligomer were targeted by an antibody that does not bind to L929 cells. Antibody-bearing liposomes containing antisense oligomers thus have a double specificity: a particular cell selected by the targeting antibody on the liposome and a particular mRNA in the cell selected by sequence complementarity with the liposome-encapsulated oligomer. Nonencapsulated oligomers are sensitive to nucleases and usually must be administered to cells at high concentrations. Oligomers encapsulated in liposomes resist DNase and are active in amounts 1-2 orders of magnitude lower than for those reported for unencapsulated oligomer sequences.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1989

Antibody targeted liposomes containing poly(rI).poly(rC) exert a specific antiviral and toxic effect on cells primed with interferons alpha/beta or gamma.

Double-stranded RNA can stimulate interferon production and mediate an antiproliferative effect on certain cell types. We evaluated the possibility of specifically targeting to cells in vitro the RNA duplex poly(rI).poly(rC) in pharmacologically active form after its encapsulation in small, unilamellar liposomes, to which was covalently coupled protein A. These liposomes became bound to and were endocytosed by murine L929 cells in the presence of protein A-binding monoclonal antibodies specific for an expressed cell surface protein, the H-2K molecule. When L929 cells were preincubated in the presence of low doses of interferon alpha/beta or gamma, they could be activated to produce interferon following exposure to either free poly(rI).poly(rC), or specifically bound liposomes poly(rI).poly(rC), but not the same liposomes in the presence of non-cell binding control antibodies. Specifically bound liposome-encapsulated poly(rI).poly(rC) was toxic to L929 cells at dose levels at least three logs lower than free poly(rI).poly(rC). This toxicity was also dependent on pre-treatment with interferon. These results indicate that liposome-encapsulated poly(rI).poly(rC) can survive endocytosis and can be released in active form to specific cell populations, at concentrations much lower than that required for pharmacologic effects of the same molecule in free form. They suggest that introduction into cells of other nucleic acids might benefit from the antibody-targeted liposome technology described here.

Animals↗
PubMed1988

Inhibition of cell proliferation with antibody-targeted liposomes containing methotrexate-gamma-dimyristoylphosphatidylethanolamine.

We have prepared liposomes containing methotrexate-gamma-dimyristoylphosphatidylethanolamine (MTX-DMPE liposomes), to which protein A was covalently coupled, permitting specific association of these liposomes in vitro with murine cells preincubated with relevant protein A-binding monoclonal antibodies. In the absence of antibody the presence of externally-oriented methotrexate (MTX) in MTX-DMPE liposomes did not result in greater binding to cells than liposomes made without MTX-gamma-DMPE. Derivation of methotrexate with phospholipid permits enhanced drug-liposome association. These liposomes are more resistant than conventional liposomes to repeated cycles of freezing and thawing. MTX-DMPE liposomes are comparable to antibody-targeted liposomes made with encapsulated water-soluble methotrexate both with respect to specific binding to target cells and drug effect. The inhibitory effects of MTX-liposomes, as well as free MTX, were reversible by either thiamin pyrophosphate (Tpp) or N5-formyltetrahydrofolate (F-THF), while the effects of MTX-DMPE liposomes were reversed only by N5-formyltetrahydrofolate. This suggests that the toxicity of non-targeted MTX-liposomes may be due to leakage of the encapsulated MTX. The absence of an effect of thiamin pyrophosphate on non-targeted MTX-DMPE liposomes indicates that they do not enter into the cell via the normal folate transport system.

Ammonium Chloride↗
PubMedDate not supplied

All in the superfamily: presentation of antigen receptors in the context of the major histocompatibility complex.

I propose that the antigen-induced internalization of antigen receptors of B or T lymphocytes serves to assure the interaction of those receptors, in intracellular compartments, with the major histocompatibility complex (MHC)-encoded molecules of the cells, which are themselves internalized constitutively. Antibody and T-cell receptors have conserved regions which promote the association of their unique amino acid sequences ("idiotypes") with MHC molecules as a consequence of exposure to the acidic environment of endocytic vesicles. If the antigen is internalized with the antigen receptor, it may associate with MHC molecules which it encounters after internalization if it has sequences permitting this association. Thus, these cells may express either "idiotype"-MHC or antigen-MHC complexes, or both, after the re-expression at the cell surface of the complexes which form intracellularly, permitting the recognition of these cells by T cells specific for these structures. This mechanism permits the organism to respond to antigens for which it has affinity, in a manner which does not depend on the structure of the antigen, by the use of its own receptors. These molecules co-evolve with the MHC molecules of the species in a way that preserves the possibility of their interaction.

Animals↗
PubMedDate not supplied

Pleiotropic loss of activation pathways in a T-cell receptor alpha-chain deletion variant of a cytolytic T-cell clone.

Untransformed T-cell clones maintained in culture are dependent on signals transmitted through their antigen receptors (Ti; alpha and beta chains associated with the CD3 molecules) for growth and effector function. For cytolytic T cells (CTL), Ti stimulation also activates the killing machinery and induces synthesis of gamma interferon (IFN-gamma) messenger RNA and IFN-gamma secretion. The Thy-1 molecule, expressed on all murine cells of the T-cell lineage, has been suggested to function in transmembrane signalling, based on the ability of some anti-Thy-1 monoclonal antibodies (mAb) to activate T cells. Recently, it was suggested that Thy-1 could function as a signal-transduction molecule when expressed in B-cell lymphomas after transfection of the gene, leading to speculation that the molecule was part of an activation pathway independent of the Ti/CD3 structures. Here we report the immunoselection of a variant CTL clone which has lost expression of mRNA for the alpha-chain of the Ti. The Ti- variant was defective in lectin-mediated activation whether measured by increase in intracytoplasmic Ca2+, CTL effector function or IFN-gamma synthesis. The variant, which expressed normal levels of Thy-1, was also unresponsive to Thy-1 mAb activation as measured by IFN-gamma secretion, whereas it responded to calcium ionophore plus phorbol ester. These results indicate that in a non-transformed, functional mature T-cell, Thy-1 mediated signalling is not an alternative to, but might depend on elements associated with the Ti/CD3-mediated T-cell activation pathway.

Antibodies, Monoclonal↗