Polyacryl starch microparticles have been developed as an oral vaccine adjuvant capable of inducing strong local and systemic immune responses in mice. In this thesis, the starch microparticles were studied in order to increase basic understanding of their function. In particular, the thesis addressed aspects of the uptake of the particles and their presentation to the immune system after different routes of administration, in correlation with the differentiation of the induced immune response.
When using human serum albumin as a model antigen conjugated to the microparticles, it was found that the route of administration and the use of different combinations of routes, parenteral or oral, affect the profile (Th1/Th2 balance) of the induced immune response. It was also found that oral boosters are needed for the development of a local s-IgA response.
Ligated mouse intestinal loops in combination with confocal laser-scanning microscopy demonstrated that the uptake of the particles by the intestinal mucosa takes place over the follicle-associated epithelium (FAE) that covers the Peyer’s patches. The particles are also taken up in the villus epithelium when conjugated with rCTB, a ligand to the GM1 receptor. This qualitative difference in uptake did not affect the induced immune response. Thus, the addition of rCTB to the microparticles did not improve or influence the profile of the immune response. Chronic stress, known to alter the barrier function of the FAE, increased the cellular response but did not affect the humoral immune response.
Despite positive results in rodents, the particles were not able to boost a humoral immune response in man when tested with diphtheria toxin-cross reacting material (CRM197). Possible methods of improving the adjuvant effect in man are discussed.