Each of these vaccine candidates demonstrated the ability of this simple lipid structure to dramatically enhance the immunogenicity of antigens that are otherwise immunologically inert. Nevertheless, the approach introduces complexities into the vaccine manufacturing process due to the requirement for covalent attachment of Pam 2 Cys to an antigen. The use of the anionic lipopeptide E 8 Pam 2 Cys overcomes many of the technical complexities related to this process, especially the use of covalent chemistries, by making use of electrostatic association with antigen [23] .