The preparation and characterization of polymeric antigen delivery systems for oral administration.

Although polymeric delivery systems are well established for the oral administration of conventional drugs, they have not yet been commercially developed for vaccine delivery. The problems inherent with the oral route of delivery, including low pH, gastric enzymes, rapid transit and poor absorption of large molecules, has made the goal of oral delivery of antigens very challenging. Nevertheless, several polymeric delivery systems for the oral administration of vaccines are currently being evaluated, including microencapsulation in poly(lactide-co-glycolides), alginates, polyanhydrides, starch, polymethacrylates, polyamino acids and enteric coating polymers. These approaches are designed to protect the antigen in the gut, to target the antigen to the gut-associated lymphoid tissue, or to increase the residence time of the antigen in the gut through bioadhesion. Each of these approaches is discussed in relation to antigen encapsulation and integrity, process reproducibility, ease of preparation and encapsulation efficiency. Potential problems associated with the scale-up of these approaches are also briefly addressed. Of particular relevance are the prospects for the application of these formulation processes for commercial development.