Association of gross virus-associated cell-surface antigen with liposomes

Abstract

Summary.-Gross Cell-Surface Antigen (GCSAa) was obtained from W/Fu (C58NT)D lymphoma cells by Nonidet P40(NP40) or 3M KC1 extraction and further purified by Sephadex G200 filtration. GCSAa was associated with lipids (dipalmitoylphosphatidycholine, cholesterol and dicetylphosphate, in molar ratios of 7:2:1) to form multilamellar liposomes. The amount of protein associated with liposomes was found to be proportional to the protein concentration of the sensitizing cellular extract and to the amount of phospholipids used and, under defined conditions, 22-55% of the protein of the cellular extract could be associated with liposomes. Analysis of disrupted sensitized liposomes showed that the GCSAa-specific activity of the liposome-associated proteins was quite similar to that of the proteins of the sensitizing cellular extract. Ultracentrifugation of disrupted liposomes showed that about 750/0 of the liposome-associated GCSAa activity was firmly associated with lipids and that little GCSAa was trapped within aqueous compartments between lipidic lamellae. 18-8.o0% of the liposome-associated GCSAa was expressed at the liposome surface. No striking differences in degree of GCSAa association were found between liposomes sensitized by NP40 or by 3M KCI extracts. Storage experiments at +4°C showed that GCSAa-sensitized liposomes were fairly stable.

Induction of antibody response to liposome-associated Gross-virus cell-surface antigen (GCSAa)

“…This could be attributed neither to a difference in antigen dose, since the in vitro specific GCSAa activities of both types of cellular extract used in these experiments were comparable, nor to a difference in GCSAa association with liposomes, since it has been shown in a previous work that the liposome composition and the distribution of GCSAa among liposomal structure are almost identical whatever the sensitizing cellular extract used (Sakai et al, 1980). Nevertheless, it may be questioned whether the 2 different antigen-solubilization procedures lead to GCSAa-bearing molecules of identical immunogenicity, since 3M KCI extraction may induce proteolytic cleavage (Mann, 1972) and since detergent solubilization produces micellar association of the solubilized molecules (Helenius & Simons, 1975).…”

“…It cannot be excluded that the adjuvant effect exerted by liposome association of the antigen may be due to a membrane presentation effect since it has been shown that solubilized membrane antigen can stimulate lymphocytes in vitro when exposed on liposomes (Curman et al, 1978;Engelhard et al, 1978). However it is worth noting that the sensitized liposome used here exposed only a small proportion of the associated GCSAa at their surface (Sakai et al, 1980).…”

“…In order to determine whether viable tumour cells could be substituted by soluble cell-surface antigen linked to artificial membrane, in inducing an antitumour response, we have previously included GCSAa, a tumour-associated virus-directed cell-surface antigen, into negatively charged liposomes (Sakai et al, 1980). The purpose of the present work was to compare in syngeneic animals the immunogenicity of soluble GCSAa extracted from W/Fu (C58NT)D lymphoma by two currently used methods to that of the liposome-associated antigen and to that of viable lymphoma cells.…”

Varicella-zoster virus as a live vector for the expression of foreign genes.

“…For instance, glycosylation has been shown to influence the recognition by the immune system of influenza virus hemagglutinin and murine leukemia virus gp7O glycoproteins (40). The presentation of a protein also can greatly influence its immunogenicity (41)(42)(43). While neither processing nor presentation may be necessary for the production of neutralizing antibodies in every case, the epitopes needed for protective immune responses against a particular pathogen may be in question.…”

Immunogenicity of Hapten-Carrier Conjugates Associated with Liposomes

“…According to the technique described by Sakai et al [12], nega tively charged multilamellar liposomes were prepared by dispers ing a film of dipalmitoyphosphatidyl choline, cholesterol and diacetylphosphate in 7:2:1 molar ratio in a solution of DNP-HGG or of DNP-BSA. The liposome suspension was kept 30 min at room temperature, then diluted with cold saline and centrifuged at 30,000 g for 30 min.…”