Immune responses in mice of β‐galactosidase adsorbed or encapsulated in poly(lactic acid) and poly(lactic‐co‐glycolic acid) microspheres

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Abstract
The immune response induced in mice by β‐galactosidase (β‐gal) adsorbed or encapsulated on poly(lactic acid) (PLA) and poly(lactic‐co‐glycolic acid) (PLGA) microspheres was investigated. The encapsulated protein elicited higher antibody response than the protein adsorbed on the microspheres in the case of the PLA microspheres. However, the encapsulated protein elicited weaker antibody response than the adsorbed protein in the case of the PLGA (50:50) microspheres, probably because, in this case, the encapsulation process adversely affected protein immunogenicity. In the case of adsorbed β‐gal, higher antibody response was obtained with the PLA microspheres than with the PLGA (50:50) microspheres. This may be related to the lower rate of β‐gal desorption from the PLA microspheres. Based on the immunoglobulin G1/immunoglobulin G2a ratios and the stimulation indices for interferon‐γ and interleukin‐4, β‐gal encapsulated or adsorbed on PLA microspheres induced a Th1‐biased immune response whereas β‐gal encapsulated or adsorbed on PLGA (50:50) microspheres induced a Th2‐biased immune response. The results obtained indicate that more potent immune responses are obtained when the protein is encapsulated than adsorbed on the microspheres, providing that the encapsulation process does not adversely affect protein immunogenicity. Also, the type of polymer used to prepare the microspheres, but not the method of protein association with the microspheres, may affect the type of immune response. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 73A: 332–338, 2005