Solid fat nanoemulsions as vaccine delivery vehicles

DETAILED DESCRIPTION The present invention provides pharmaceutical compositions comprising nanoemulsions of particles comprising a lipid core composed of a lipid which is in a solid or liquid crystalline phase at at least 25.
degree.
C.
, stabilized by at least one phospholipid envelope, for the parenteral, oral, ocular, rectal, vaginal, intranasal, or topical delivery of both fat-soluble and water-soluble immunogens.
The new entity is a particulate vehicle which is denoted herein as a solid fat nanoemulsion or "emulsome.
" These compositions have features which are intermediate between liposomes and oil-in-water emulsions.
Emulsome particles contain a hydrophobic core, as in standard oil-in-water emulsions, but surrounded and stabilized by one or more bilayers or envelopes of phospholipid molecules, as in liposomes (FIGS.
1A, 1B and 1C).
A key feature of these particles is that the core is composed of a lipid which in bulk form is in a solid or liquid crystalline phase, rather than an oil in a fluid phase.
Lipid compositions of the core are characterized as being in the solid or liquid crystal phase at at least 25.
degree.
C.
when measured in bulk form.
Emulsomes, having the characteristics of both liposomes and emulsions, provide the advantages of high loading of hydrophobic bioactive compounds in the internal solid lipid core and the ability to encapsulate water-soluble antigens in the aqueous compartments of surrounding phospholipid layers.
The present pharmaceutically stable solid fat nanoemulsions or emulsomes may be formulated in the absence of any ionic or non-ionic nonnatural synthetic surfactants or cosurfactants such as polyoxamers, deoxycholate, polysorbates, tyloxapol, or emulphor.
They are stabilized by the combination of relatively high lecithin content and the use of solid lipid compositions as the core.
The particle size distribution of emulsomes, based on differential weight percents, is in the range of 10-250 nm, making them suitable for parenteral administration.
The emulsome technology represents a new type of lipid-based encapsulation technology that has potential usefulness as carriers of vaccines and adjuvants enhancing the immunogenicity of antigens incorporated intrinsically or extrinsically into the particles