In previous works, our research group has successfully proved the use of subcellular
vaccines based on
poly(epsilon-caprolactone) (PEC) microparticles containing an antigenic extract of Brucella ovis (HS) against experimental
brucellosis in both mice and rams. However, the successful exploitation of
pharmaceutical products, and therefore of this product as veterinary
vaccine, requires preservation of both
biological activity and native structure in all steps of development from purification to storage. In this context, we have carried out an accelerated stability study to evaluate the relative stability of HS when loading in PEC microparticles. For this purpose, freeze-dried microparticles were stored at 40 +/- 1 degrees C and 75% RH as a preliminary analysis of a stability testing. The results showed that both physico-chemical (size, morphology,
antigen content, release profile) and
biological (integrity and antigenicity of the HS) properties were preserved after 6 months of storage. On the contrary, after 1 year of storage, the HS release profile was dramatically affected probably due to a progressive loss of the
polymer microstructure. In addition, the degradation and loss of the antigenicity of the HS components was also evident by SDS-PAGE and immunoblotting analysis. In fact, after 12 months of storage, only the integrity and antigenicity of two of the major protective
proteins of the HS antigenic complex were preserved.