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.

Serum lipoprotein allotypes in inbred strains of rabbits

Serum lipoprotein allotypes were examined for 10 males and 10 female rabbits from each of 16 genetically defined strains. The results suggested that the four allotypes, Lpq 1, Lpq2, Lpq3, and Lpq4, were controlled by three closely linked genes, IpqA, IpqB, and IpqC. Gene IpqA, controlling the expression of the Lpq1 and Lpq2 allotypes, and gene IpqB controlling the expression of the Lpq3 allotype, show limited polymorphisms.

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.

Immunoliposome labeling: a sensitive and specific method for cell surface labeling

A simple, one-step procedure for fluorescence labeling of cultured cells with high sensitivity and specificity is described. We term this method immunoliposome labeling. Monoclonal IgG antibody was first covalently coupled with palmitic acid. The palmitoyl IgG was then incorporated into unilamellar liposomes (about 100 nm diameter) containing either N-(4-nitrobenzo-2-oxa-1,3-diazole)- or N-(fluorescein isothiocyanyl)-phosphatidylethanolamine by a detergent-dialysis procedure. A monoclonal antibody to the mouse major histocompatibility antigen, H-2k, was tested as a model system. Fluorescent liposomes with covalently coupled anti-H-2k specifically labeled the mouse L-929 cells (H-2k type), but not the A-31 cells (H-2d type). The degree of labeling was quantitated by a microscope photometer. Cells labeled with fluorescent liposomes showed 4--6-fold stronger fluorescence than cells labeled with either fluorescein-conjugated antibody or with primary antibody followed by fluorescein-conjugated secondary antibody (indirect immunofluorescence). Since different types of label (fluorescent, radioactive, etc.) can be incorporated into liposomes, this specific and sensitive method is potentially very versatile.

Cell-mediated immunity to herpes simplex virus: induction of cytotoxic T lymphocyte responses by viral antigens incorporated into liposomes

The immunogenicity of inactivated herpes simplex virus type 1 (HSV-1) antigens incorporated into liposomes was measured by their ability to induce secondary anti-HSV-1 specific cytotoxic T lymphocyte (CTL) responses in splenocyte cultures from virus-primed mice. Such virus-specific CTL could be induced provided the liposomes contained virus along with plasma membrane antigen of the same H-2 type as that of the virus-primed responser cells. Responses did not occur in cultures stimulated with liposomes containing only viral antigens or with a mixture of liposomes composed respectively of lipid and virus with those composed of lipid and plasma membrane proteins. Moreover F1 responder cells stimulated with liposomes composed of virus and plasma membrane protein of one of the parental haplotypes produced CTL restricted in their cytotoxicity to infected targets of the same haplotype as was used in the liposome. These results show that liposomes can be used to induce anti-HSV-1 CTL with inactivated viral antigens but recognition of both viral and H-2 antigen is required for this process to occur in vitro. The implications of our findings to the preparation of subunit vaccines against HSV-1 are briefly discussed.

Cell-mediated immunity to herpes simplex virus: induction of cytotoxic T lymphocyte responses by viral antigens incorporated into liposomes

The immunogenicity of inactivated herpes simplex virus type 1 (HSV-1) antigens incorporated into liposomes was measured by their ability to induce secondary anti-HSV-1 specific cytotoxic T lymphocyte (CTL) responses in splenocyte cultures from virus-primed mice. Such virus-specific CTL could be induced provided the liposomes contained virus along with plasma membrane antigen of the same H-2 type as that of the virus-primed responser cells. Responses did not occur in cultures stimulated with liposomes containing only viral antigens or with a mixture of liposomes composed respectively of lipid and virus with those composed of lipid and plasma membrane proteins. Moreover F1 responder cells stimulated with liposomes composed of virus and plasma membrane protein of one of the parental haplotypes produced CTL restricted in their cytotoxicity to infected targets of the same haplotype as was used in the liposome. These results show that liposomes can be used to induce anti-HSV-1 CTL with inactivated viral antigens but recognition of both viral and H-2 antigen is required for this process to occur in vitro. The implications of our findings to the preparation of subunit vaccines against HSV-1 are briefly discussed.

Transient permeabilization induced osmotically in membrane vesicles from Torpedo electroplax: a mild procedure for trapping small molecules

During hypoosmotic stress, membrane vesicles enriched in acetylcholine receptors become more permeable to external tracer molecules. When vesicles are immersed in 3 volumes of water containing 22Na+, 50-70% of 22Na+ equilibration is attained within 90 s. On the other hand, the uptake of 22 Na+ is greatly diminished only 6-10 s after an osmotic shock, and vesicle resealing is completed within 15 s. Furthermore, 90 s after osmotic shock, efflux rates are comparable to those of native vesicles, which also indicates that the vesicles have resealed. During osmotic shock, the entry of molecules into the vesicles increases with the strength of the osmotic shock and also depends on the size of the permeant. With a given strength of osmotic shock, the large molecule [3H]inulin (Mr 5000) is taken up less than the smaller molecules 22Na+ and [3H]sucrose. In addition, alpha-bungarotoxin binding latency of the vesicles is not affected by osmotic shock, indicating that the sideness of the vesicles remains unchanged. The acetylcholine receptors in the vesicles remain functional after osmotic shock. For example, 90 s after 22Na+ and [3H]sucrose are loaded into vesicles by osmotic shock, only 22Na+ is released by dilution in a buffer containing carbamoylcholine (carbamylcholine). Also, the influx of 22 Na+ into previously shocked vesicles can be specifically stimulated by carbamoylcholine. Such stimulations in the shocked vesicles can be blocked by d-tubocurarine or alpha-bungarotoxin, and they can be desensitized by preincubation with carbamoylcholine. These results suggest the possibility of using osmotic shock to load molecular probes into these membrane vesicles, which could provide a powerful tool for studying inner surfaces of the intact vesicles.

Monoclonal antibody covalently coupled with fatty acid. A reagent for in vitro liposome targeting

Monoclonal antibody to the mouse histocompatibility antigen, H-2k, was derivatized with palmitic acid using an activated ester of N-hydroxysuccinimide. About 70% of the resulting amphipathic antibody could be incorporated into liposomes by a detergent-dialysis method. The antibody-bound liposomes were about 900 A in diameter and were heterogeneous in terms of the number of antibody molecules per liposome. These liposomes showed specific binding affinity to mouse L-929 cells (H-2k), but not to A-31 cells (H-2d), whereas native liposomes showed no detectable binding to either cell type. The specific binding of anti-H-2k-bound liposomes to L-929 cells could be blocked by a preincubation of cells with an excess of free, underivatized anti-H-2k antibody but not by normal mouse IgG. Using a fluorescent phospholipid, liposomes containing anti-H-2k specifically labeled L-929 cells but not A-31 cells in a mixed culture. Liposomes containing normal mouse IgG did not significantly label either cell type. These results clearly demonstrated the effectiveness of the monoclonal antibody for liposome targeting.

Studies on the insulin mediator. II. Separation of two antagonistic biologically active materials from fraction II

Insulin treatment significantly altered the elution profile of deproteinized muscle extracts chromatographed on Sephadex G-25 columns, particularly in fraction II, which contains the insulin mediator. Further purification of fraction II by high-voltage paper electrophoresis at pH 1.9 and 3.5 resulted in two active fractions. Fraction 1 leads to 4 stimulated the cyclic AMP-dependent protein kinase and inhibited glycogen synthase phosphoprotein phosphatase, and may be a novel substance. Fractions 1 leads to 6 and 3 leads to 6 inhibited the cyclic AMP-dependent protein kinase and stimulated glycogen synthase phosphatase. It is proposed that the insulin mediator is present in fractions 1 leads to 6 and 3 leads to 6.