Modulation of the cellular immune response after oral or subcutaneous immunization with microparticles containing Brucella ovis antigens.

An antigenic extract (HS) from Brucella ovis was encapsulated in either poly-epsilon-caprolactone (PEC) or poly-lactic-co-glycolic acid 75:25 (PLGA) microparticles containing beta-cyclodextrin and Pluronic F-68 as stabilising agents. The resulting microparticles displayed sub-5 microm sizes. Antigen loading was 5.2 and 3.8 microg/mg for HS-PEC and HS-PLGA microparticles, respectively. Specific HS cytokine profiles were determined after subcutaneous and oral immunisation of BALB/c mice. Gut distribution studies of the formulations after oral administration showed that HS-PEC microparticles interacted more strongly with mucosa and Peyer's patches than HS-PLGA. Accordingly, oral immunisation with HS-PLGA induced a negligible immune response, whereas HS-PEC elicited a Th1 response although of low intensity. Subcutaneous immunisation with HS-PEC induced high IFN-gamma and IL-2 release; in contrast, HS-PLGA particles induced a Th2 profile characterized by significant levels of IL-4. Splenic cells from free-HS immunised mice released IFN-gamma and IL-2 but not IL-4. A less intense Th1 pattern was also found from HS stimulated nai;ve splenic cells. These results suggest that the HS itself possesses Th1 immunopotentiating properties, required to control brucellosis, that can be specifically increased by encapsulation in PEC microparticles. In contrast, PLGA microparticles modulate the response toward a Th2 pathway.