PLA and PLGA microspheres of beta-galactosidase: Effect of formulation factors on protein antigenicity and immunogenicity.

The entrapment of beta-galactosidase (Escherichia coli) in PLA and PLGA microspheres using a double emulsion technique resulted to significant reduction of protein antigenicity. The extent of antigenicity loss depended on the conditions of microsphere preparation. Most of antigenicity loss occurred on the first emulsification step. Only the effects of microsphere preparation factors having an important influence on protein antigenicity, such as the type of organic phase (polymer solvent) and homogenization, could be predicted (on a qualitative basis) by antigenicity data obtained after the first emulsification step. The type of polymer and polymer solvent used to prepare the microspheres affected beta-galactosidase immunogenicity. The PLA microspheres prepared using ethyl acetate was the most immunogenic microsphere formulation, eliciting similar total antibody responses as the alum formulation of beta-gal. This formulation was the only microsphere formulation that induced an IgG1/IgG2a ratio lower than 1, indicating an immune response biased towards a Th1 type. The results obtained indicate that large protein molecules with complex tertiary structure such as beta-galactosidase can be entrapped in PLA and PLGA microspheres with retention of protein immunogenic potential, providing that appropriate conditions of microsphere preparation are applied, and that the formulation of microspheres might influence the Th1/Th2 type of immune response against the encapsulated antigen. Copyright 2004 Wiley Periodicals, Inc.