Collagen minipellet as a controlled release delivery system for tetanus and diphtheria toxoid.

The use of biodegradable polymer matrices as a single-dose vaccine delivery system was investigated using tetanus toxoid (TT) and diphtheria toxoid (DT). BALB/c mice were immunized with TT or DT in different formulations including individual, in minipellet and aluminum hydroxide (alum), and the antibody responses were monitored for 48 weeks. Antigens entrapped in minipellet elicited higher antibody responses compared to those obtained with individual antigens and antigens adsorbed to alum and the antibody levels remained elevated over 48 weeks. In addition, minipellet formulations induced the same subclasses of antibodies induced by alum formulations. These results raise the possibility to obtain optimal and long-lasting immune responses by a single administration of minipellet formulations.