Designing liposomes as vaccine adjuvants

The most important perquisite in modern-day prophylactic vaccine development is the production of safe, nonreverting vaccines. To do this there has been a distinct move towards peptide or protein antigen-based vaccines, which are incapable of becoming virulent or mutating. However, whilst such vaccines appear desirable on paper, they are generally poorly immunogenic. Consequently, there has been intense development in the field of adjuvants and delivery systems, which are capable of fulfilling two important functions: firstly that antigen is delivered to an immunologically relevant cell, and secondly that antigen is recognised as being immunogenic and subsequently processed.Whilst many adjuvants are successful at ticking one of these parameters, few can act as the combined immunostimulatory delivery systems. Liposomes are among some of the successful formulations, which have been pursued as clinically relevant adjuvants (equally there are many liposome formulations which have been ignored due to their inability to be both delivery vehicle and immunostimulatory). However, in this chapter we will focus on the successful design of adjuvantal liposomes, which are of interest to vaccine developers focusing on life-threatening diseases of both the developing and developed world. Particular emphasis will be given to structural considerations and how varying these have an effect on the observed immunological outcome, measured in either in vitro, in vivo or ex vivo studies.