Development characterizations and evaluation of Poly(-ε-caprolactone)-based microspheres for hepatitis B surface...

The major disadvantage of several currently available vaccines is the need for repeated administrations. The aim of the study was to develop long-acting microspheres based on poly(-ε-caprolactone) (PCL) for delivery of recombinant hepatitis B surface antigen (rHBsAg). PCL microspheres were prepared for induction of humoral and cellular immunity by intramuscular administration. Microspheres were characterized for their size, shape, incorporation efficiency, zeta potential, antigen integrity, antigen conformation and immunogenicity. DSC (Differential Scanning Calorimetry) studies revealed that better encapsulation efficiency between high and low mol wt polymer. The Circular Dichorism spectroscopy (CD) of antigen, released from PCL microspheres revealed that the secondary structure of antigen was unperturbed. Antigen integrity was evaluated by SDS-PAGE. Immunization with HBsAg PCL microspheres resulted in upregulation of specific cellular (IFN-γ and IL-2) as well as IgG response in BALB/c mice. Immune responses were found significantly higher than the conventional alum adjuvant following a single intramuscular immunization. These results highlight the enhanced efficiency of these PCL microspheres as an adjuvant and their prospective use in the prevention of hepatitis B.