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© 2016, The Author(s).Previously, we showed that CD206-targeted liposomal delivery of co-encapsulated immunodominant myelin basic protein (MBP) sequences MBP46–62, MBP124–139 and MBP147–170 (Xemys) suppressed experimental autoimmune encephalomyelitis in dark Agouti rats. The objective of this study was to assess the safety of Xemys in the treatment of patients with relapsing-remitting multiple sclerosis (MS) and secondary progressive MS, who failed to achieve a sustained response to first-line disease-modifying therapies. In this phase I, open-label, dose-escalating, proof-of-concept study, 20 patients with relapsing-remitting or secondary progressive MS received weekly subcutaneously injections with ascending doses of Xemys up to a total dose of 2.675 mg. Clinical examinations, including Expanded Disability Status Scale score, magnetic resonance imaging results, and serum cytokine concentrations, were assessed before the first injection and for up to 17 weeks after the final injection. Xemys was safe and well tolerated when administered for 6 weeks to a maximum single dose of 900 μg. Expanded Disability Status Scale scores and numbers of T2-weighted and new gadolinium-enhancing lesions on magnetic resonance imaging were statistically unchanged at study exit compared with baseline; nonetheless, the increase of number of active gadolinium-enhancing lesions on weeks 7 and 10 in comparison with baseline was statistically significant. During treatment, the serum concentrations of the cytokines monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, and interleukin-7 decreased, whereas the level of tumor necrosis factor-α increased. These results provide evidence for the further development of Xemys as an antigen-specific, disease-modifying therapy for patients with MS.

Cationic liposomes, consisting of synthetic amphiphiles and a so-called helper lipid, rapidly form complexes with DNA, known as lipoplexes. When incubated with cells in culture, the DNA can be delivered into the cell and becomes expressed. Because of these properties, lipoplexes are considered a useful alternative for viral vectors for in vivo genetherapy. Yet, many hurdles have still to be taken. These an illustrated in the present overview, which briefly describes the critical steps involved in overall gene delivery in vitro, ranging from lipoplex formation to nuclear penetration and delivery of the desired gene.

We have investigated the possibility of a T-cell epitope peptide providing help for a B-cell epitope peptide when both peptides are co-entrapped in the same liposomes. Epitope models used were a 28 amino acid peptide from the S region of the hepatitis B surface antigen (HBsAg) (subtype adw) containing an H-2s Th-cell epitope, and a 33 amino acid peptide from the pre-S1 region of the HBsAg (subtype adw) designed to exclude an adjacent H-2s T-cell epitope, the latter (pre-S1) peptide being recognized by SJL (H-2s) mice as a B-cell epitope. SJL(H-2s) mice were immunized twice intramuscularly with S or pre-S1 peptide alone, co-entrapped in the same liposomes or entrapped in separate liposomes which were mixed before injection. Analysis of sera for anti-peptide IgG1 antibodies revealed that the Th-cell peptide provided help for the pre-S1 peptide only when the two peptides were co-entrapped in the same vesicles. This helper effect was found to correlate with the ability of S peptide (co-entrapped with the pre-S1) to stimulate T-cell proliferation in vitro. There was no IgG1 response against pre-S1 peptide in mice immunized with a mixture of the free peptides or a mixture of separately entrapped peptides. A helper effect, albeit much weaker, was also observed in mice immunized with the two peptides emulsified in incomplete Freund's adjuvant. Antisera from mice immunized with both peptides co-entrapped in liposomes were found to bind to full length (pre-S1 containing) recombinant HBsAg. Moreover, binding values were much higher than those seen with antisera from animals immunized with the liposomal S peptide above, presumably because of full access of anti-pre-S1 antibodies to the pre-S1 region of the rHBsAg. It is concluded that liposomes could serve not only as an immunological adjuvant for peptides but also as a carrier for Th- and B-cell epitopes thus eliminating the need for covalent linkage to a carrier protein.

It is well established that after intravenous injection large-size liposomes are rapidly cleared from the blood and taken up by cells belonging to the reticulo-endothelial system (RES). Particularly, fixed macrophages in liver (Kupffer cells) and spleen are actively involved in the uptake of the vesicles.1–5 Uptake occurs by way of endocytosis followed by intralysosomal degradation of liposomal lipids and release of entrapped substances.5 The natural affinity of liposomes for macrophages has been exploited in the application of liposomes as a drug delivery system to this cell type. For example, liposomes have been used as carriers of antimicrobial agents in the treatment of intracellular infections such as experiental leishmaniasis,6 candidiasis7,8 or listeriosis.9 In these infections the microorganisms are lodged in the lysosomes of tissue macrophages, precisely the site where the liposomes end up after intravenous injection. Thus, encapsulation of relevant antibiotic drugs within liposomes results in an increased therapeutic index of these drugs when administered intravenously.

The effect of various manipulations of liposomes composed of equimolar phospholipid and cholesterol on immune responses to the incorporated immunopurified tetanus toxoid was investigated in BALB/c mice. In studies designed to establish proper dosage for immunization and to reveal the roles of the liposomal phospholipid to toxoid mass ratio, gel-liquid crystalline transition temperatures (Tc) of the liposomal phospholipids and mode of antigen incorporation into liposomes on immune responses, animals were injected intramuscularly with various amounts of the toxoid, free, entrapped in multilamellar dehydration-rehydration vesicles (DRV) or covalently linked to the surface of multilamellar vesicles (MLV) prepared by the classical procedure. Two identical injections separated by 4 weeks were given and IgG1 and IgG2b antibodies specific for the toxoid assayed in sera by an enzyme-linked immunosorbent assay. Results suggest that the adjuvant effect of liposomes is improved considerably when liposomal phospholipid to toxoid mass ratios are as high as 2049:1; however, adjuvanticity is reduced to reach very low levels for much higher ratios (e.g. 90,361:1); antibody responses are similar for liposomes (phospholipid to toxoid mass ratios: 14.3-33.1) made of a variety of phospholipids with Tcs ranging from -32 degrees to 41.5 degrees but are low or non-existent when liposomes are made of distearoyl phosphatidylcholine (Tc, 54 degrees) (however, see Discussion); there are no differences in antibody responses between liposomes with entrapped and surface-linked toxoid.