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Biomedical subjects

L Huang

Publications and source records attributed to L Huang.

At least 757 records · Page 42Linked to original sources
PubMed1983

Interactions of immunoliposomes with target cells.

We have covalently attached a monoclonal antibody (11-4.1) against the murine major histocompatibility antigen, H-2Kk, on the surface of liposomes. The interaction of these antibody-coated liposomes (immunoliposomes) with target cells, RDM-4 lymphoma (H-2Kk), was investigated. About 90% of the immunoliposomes taken up by target cells at 4 degrees C could be removed by a mild protease treatment of the cells, whereas only 30% of the uptake at 37 degrees C was labile to the same treatment. Furthermore, the uptake of immunoliposomes at 37 degrees C was inhibitable by cytochalasin B or by a combination of 2-deoxyglucose and NaN3. These results suggest that immunoliposome binding to the target cell surface is the primary uptake event at 4 degrees C and that the surface-bound liposomes are rapidly internalized by the cells at 37 degrees C, probably via an endocytic pathway. Studies with fluorescence microscopy of target cells treated with immunoliposomes containing carboxyfluorescein also supported this conclusion. If endocytosis is the mechanism by which immunoliposomes gain entry into target cells, the efficacy of a cytotoxic drug encapsulated would depend on the resistance of the drug to lysosomal inactivation and its ability to escape from the lysosomal system. Consistent with this notion, we observed that methotrexate encapsulated in liposomes bearing 11-4.1 antibody specifically inhibited deoxy[6-3H]uridine incorporation into DNA in target RDM-4 cells but not in P3-X63-Ag8 myeloma cells (H-2Kd) at the same doses. The observed cytotoxic effect of encapsulated methotrexate could be reversed by the treatment of cells with a lysosomotropic amine, chloroquine, which has been shown to increase the intralysosomal pH of mammalian cells. On the other hand, cytosine-beta-D-arabinofuranoside encapsulated in immunoliposomes showed no target-specific killing, probably because the drug is readily inactivated in the lysosomal system. These results are discussed in terms of the drug carrier potential of immunoliposomes.

Animals↗
PubMed1983

Incorporation of acylated wheat germ agglutinin into liposomes.

Purified wheat germ agglutinin (WGA) was derivatized with palmitic acid at an average stoichiometry of one fatty acid per dinner. Palmitoyl WGA was readily incorporated into liposomes with a cholate-dialysis method. Liposome-bound WGA caused agglutination of red blood cells at a concentration eight-fold lower than that of the native lectin. Furthermore, enhanced binding of liposome-bound WGA to mouse spleen cells was also observed. Potential applications of the liposome-bound lectin are discussed.

Animals↗
PubMed1983

A novel cytochemical marker for liposome decomposition in lysosomes.

The endocytosis of large unilamellar liposomes composed of phosphatidylcholine by the cultured Chinese hamster V-79 cells is demonstrated with electron microscopy cytochemistry. A novel cytochemical marker, 5-Br,4-Cl,3-indolylphosphate (BCIP) is used. This marker is a soluble and colorless substrate for the lysosomal acid phosphatase and can be readily entrapped in liposomes. The product of the enzymatic reaction, 5-Br,4-Cl,3-hydroxy indole, rapidly self-condenses and becomes an insoluble derivative of indigo blue. In thin section transmission electron microscopy, the condensed product appears as electron-dense deposits in the lysosomes. Since the electron-dense deposit only appears when the endocytosed liposomes are delivered to the lysosomes as the result of phagosome-lysosome fusion, this marker provides a unique cytochemical means to reveal those liposomes that are lysosomotropic and are actually decomposed within the lysosomes. No electron-dense deposits are found in the liposome-treated cells in the presence of chloroquine, or a combination of NaN3 and deoxyglucose. As a comparison, we have also used horseradish peroxidase entrapped in liposomes to confirm the endocytic uptake of liposomes. Using a radioactive marker, 125I-labeled lysozyme, entrapped in liposomes, it is shown that about 20-30% of liposome uptake by V-79 cells is due to endocytosis.

Animals↗
PubMed1982

An improved method for covalent attachment of antibody to liposomes.

A rapid and simple method is described for the incorporation of monoclonal antibody coupled with palmitic acid into liposomes prepared by the reverse-phase evaporation method (Szoka, F. and Papahadjopoulos, D. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 4194-4198). Palmitoyl antibody in 0.15% deoxycholate is added to a liposome suspension after the majority of the organic solvent has been removed by evaporation. Efficient incorporation (over 80%) of palmitoyl antibody occurred without leakage of the encapsulated drug. Native, unmodified antibody did not incorporate under identical conditions. About 50% of the incorporated antibodies could be readily digested by protease, while most of an internal protein marker was not, suggesting that about half of the antibodies were exposed on the outer surfaces of liposomes. Target-specific binding of antibody-liposomes has also been demonstrated in vitro with the RDM-4 lymphoma cells. This method offers a rapid and highly efficient attachment of functional antibody molecules to liposomes with high capture efficiency of drugs, and therefore should be useful in target-specific delivery of drugs mediated by liposomes.

Animals↗
PubMed1982

In vivo induction of anti-herpes simplex virus immune response by type 1 antigens and lipid A incorporated into liposomes.

To establish the requirements for a potential subunit vaccine against herpes simplex virus (HSV), we analyzed the effects on immunogenicity of incorporating detergent-extracted glycoprotein-enriched HSV type 1 (HSV-1) antigens into liposomes alone or with the adjuvant lipid A. Incorporating HSV-1 antigens into liposomes enhanced their immunogenicity for antibody production as detected by radioimmunoassay. Antibody levels to free and liposome-bound antigens were enhanced by administering lipid A as an adjuvant. The maximum immunogenic effect was obtained by incorporating lipid A into liposomes containing the HSV-1 proteins. Such liposomes induced secondary antibody responses higher than those engendered by virus infection. Whereas infectious virus induced cell-mediated immunity detectable by the delayed-type hypersensitivity reactions and cytotoxic T lymphocyte production, none of the liposome preparations induced cell-mediated immunity.

Adjuvants, Immunologic↗