Immune response with biodegradable nanospheres and alum: studies in rabbits using staphylococcal enterotoxin B-toxoid

In this study, the adjuvant effect of the sustained release biodegradable n anospheres (100-150 nm in diameter) has been compared with alum. Nanosphere s were formulated using a biodegradable polylactic polyglycolic acid copoly mer (PLGA, 50:50) containing Staphylococcal Enterotoxin B (SEB) toroid as a model vaccine antigen. Systemic immune response of the nanospheres contain ing toroid was studied in rabbits by subcutaneous immunization. The data de monstrated that similar to 30% of the toroid activity was lost following it s encapsulation into nanospheres. Under in vitro conditions, nanospheres de monstrated sustained release of the toroid. However, only 20% of the antige nic toroid was released over the first 2 weeks of the release study. Immuni zation of animals with equal doses of toroid, either using nanospheres or a lum induced a comparable systemic immune response (IgG, IgM and IgA). The i mmune response reached a maximum level at 7 weeks post-immunization, which then gradually declined with time. The booster dose of toroid at 19 weeks, either using alum or nanospheres induced similar immune response in both th e groups, but was greater than the primary immune response. The studies, th us, suggest that biodegradable nanospheres could be used as a vaccine adjuv ant.