Polyacryl starch microparticles as adjuvant in oral immunisation, inducing mucosal and systemic immune responses in mice.

A new vaccine adjuvant for oral administration has been examined in mice. Polyacryl starch microparticles (2-3 mum in diameter) are prepared from a water-in oil-emulsion with stabilising hydrocarbon chains. A model antigen, human serum albumin (HSA), which is not binding to the gut epithelium, was covalently coupled to the highly porous starch particles. Upon oral administration, the HSA-microparticles induced a good, diversified immune response without any signs of tolerance development. A strong cellular response can be detected as a delayed-type hypersensitivity reaction. The Th1/Th2 ratio increased with the number of doses and time during the immunisation procedure as indicated by the subclass distribution of the systemic, humoral response. Furthermore, the mucosal response was very strong in the groups that received HSA-microparticles, while the groups receiving soluble HSA did not have any detectable s-IgA in faeces. The specificity was confirmed in an ELISPOT assay. These findings indicate that starch microparticles can be an interesting candidate as an oral vaccine adjuvant. The possible causes of the strong immune responses and the possible role of the dendritic cells in the diversified immune response are discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.