Compositions of HBsAg particles having biologically active molecules contained in the particles, and methods of their use, e.g. in stimulating enhanced immune responses, are described. Antigenic peptides contained in HBsAg particles were found to produce a CTL response where none was elicited by the peptide alone. Encapsulation of immunostimulating molecules, such as cytokines, greatly enhanced the CTL response evoked by the HBsAg particles themselves.