Liposomes as Immunological Adjuvants: The Immune Response and the Effect of Liposomal Structural Characteristics

Abstract

The need for an effective and safe adjuvant for use in human immunization programs is well recognized (WHO 1976). Many of the antigens are costly or only available in small quantities (e.g. recombinant DNA products) and others, synthetic small peptides for instance, can be weakly or non-immunogenic. Adjuvants presently available, e.g. complete and incomplete Freund’s adjuvants, bacterial endotoxins, polyanions, mineral adsorbents, etc., induce local or systemic toxicity, form unacceptable granulomas, lack efficiency or have short-term effects. Another possible hazard with some of these adjuvants is the production of allergic reactions to the incorporated vaccines in a minority of recipients, especially those already sensitized to the antigen. If adjuvants contain even traces of immunogenic materials such as proteins or glycolipids, the latter may themselves induce allergic or autoallergic reactions. On the other hand, live virus vaccines can initiate persistent infections or malignancy (WHO 1976). Even the vaccinia strategy which employs the original smallpox virus vaccine in a genetically engineered form entails considerable risk (Gregoriadis 1985).