Research ArticlesPharmaceutical and Immunological Evaluation of a Single-Shot Hepatitis B Vaccine Formulated With PLGA Microspheres
Section snippets
INTRODUCTION
The evaluation of controlled-release formulations for protein-based vaccines has become an active area of vaccine pharmaceutical research.1, 2, 3, 4, 5, 6, 7, 8, 9 Currently, parenteral administration of purified protein-based vaccine antigens involves multiple injections to achieve an optimum immune response in humans. For example, recombinant Hepatitis B surface antigen (HBsAg) adsorbed to aluminum adjuvant is typically administered with multiple injections over many months to obtain a
Polymer and HBsAg
Poly(d,l)-lactide-co-glycolide acid (PLGA) with a lactide/glycolide (L/G) ratio of 65/35 (MW 75 000) and PLGA with a L/G ratio of 50/50 (MW 75 000) were purchased from Birmingham Polymers, Inc. In this paper, the corresponding polymers are referenced as PLGA65/35 and PLGA50/50, respectively. Recombinant Hepatitis B surface antigen (HBsAg) S protein was expressed in yeast and purified as outlined previously.41 The purified HBsAg used for PLGA encapsulation was dialyzed and concentrated to 1–2
Physical Characterization of PLGA Microspheres Containing HBsAg
PLGA microsphere preparation by the “double emulsion” method requires the PLGA polymer to be initially dissolved in an organic solvent, mixed and homogenized with an aqueous protein solution to form a w/o emulsion, subsequently mixed in a second solvent to form a w/o/w or double emulsion, followed by collection and drying of the protein-containing microspheres48, 49, 50, 51, 52 (see Materials and Method section). The PLGA microspheres prepared by the double emulsion method in this work were
CONCLUSIONS
The purpose of this study was to pharmaceutically characterize a HBsAg vaccine formulation with PLGA microspheres. HBsAg has been successfully encapsulated in PLGA microspheres and active antigen has been recovered upon release from the microspheres. The in vitro release studies indicate a controlled (delayed) release of HBsAg from PLGA microspheres, but that the in vitro release kinetics can be varied by experimental conditions, such as stirring rate. The biophysical and bioanalytical
Acknowledgements
The authors thank Hongkee Sah for helping to prepare some of the initial PLGA microsphere formulations containing HBsAg, Nirpal Dhanjal and Zheng Luo for carrying out some of the initial HBsAg stability studies and in vitro antigenicity measurements, Su Wang for assisting with the mouse serum analysis, Mei Tang and Mohinder Sadana for performing the amino acid analysis, and Alan Shaw and John Donnelly for helpful discussions.
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