Immunological aspects of controlled antigen delivery

Recent advances in controlled delivery systems for protein pharmaceuticals such as microspheres, liposomes, pumps and implants, have provided a new avenue for delivery of vaccine antigens. There has, however, been considerable confusion over the way in which continuous antigen delivery affects the outcome of an immune response. To date, there has been little systematic study of the influence of varying antigen exposure times and release profiles on the phenotype of the immune response, or indeed the balance between immunity and tolerance as most studies have concentrated on optimising responses to a particular antigen of interest in a single model system. As these delivery systems would find particular advantages in management of livestock species, where the use of a single administration vaccine would significantly enhance management practices, it is important to understand the relationship between controlled antigen delivery and immunity. This paper describes how existing controlled antigen delivery studies have contributed to our understanding of the development of the immune response and demonstrates how continuous antigen delivery is useful, and possibly advantageous in the generation of immunity, the maturation of the immune response and the extension of the effector response.