Multiple emulsions vaccine adjuvants

Multiple emulsions have been utilized as adjuvants for the delivery of vaccines (Herbert, 1965 Aitken, 1973 Blackall et al, 1992). The incorporation of ovalbumin or other foreign protein has been found to result in higher and more sustained antibody titers compared to those obtained with administration of vaccines in saline solutions. 

Water-in-oil solubilized adjuvant formulations of vaccines containing Clostridium welchii type D toxoid as antigen were prepared first in 1968 and tested in laboratory animals by Coles et al [238]. The adjuvant action of oil-in-water emulsions, multiple emulsions and water in gelled oil emulsions is well known but these varied systems have the disadvantages of high viscosity which makes injection physically difficult. Lin [236] quotes an HLB of 9.7 as the optimum value for water solubilization in mineral oil. Coles et al [238] found a value of 10. While the addition of a small quantity of the lipophilic surfactant Arlacel 80 (sorbitan mono-oleate) to a system of Tween 81 (polyoxyethylene (5)-sorbiton mono-oleate) alio wed increasing amounts of water to be solubilized, when toxoid solution was substituted for water the Arlacel decreased the amount which could... 

Many compounds with adjuvant activity are presently known (shown in Table 12.2) but only a few are applied routinely in human and veterinary vaccines. The application of the novel adjuvants are limited for several reasons, such as disappointing efficacy in the target animal species, insufficient safety, problems with large-scale preparations, and limited stability of the final formulations. Many studies have reported on O/W and W/O emulsions used as adjuvants and delivery systems for immunization (Hilgers et al., 1994a, b, 1999). The adjuvanticity of the W/O/W makes this type of multiple emulsion a suitable delivery system for immunization with prolonged release, and its interesting preparation is presented below. 

Comparisons of antigen carrier systems have been the subject of many studies. The reported antigenic activity depends on the properties of the carrier systems such as their adjuvant effect and/or particle size, and viscosity. For a comparison to be valid, the systems being compared must show similar properties otherwise, the studies are misleading. Based on their properties, already it is evident that emulsion and liposome formulations offer more advantageous results. In our studies we found that multiple emulsions induce more antigenic activity than any cationic particle formulation with the classic subunit vaccine, and they enhance the immunization s efficacy (Bozkir et al, 2004). 

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