Biodegradable lamellar particles of poly(lactide) induce sustained immune responses to a single dose of adsorbed protein

The adjuvanticity of lamellar particles of poly(L-lactide) (PLA) towards ad sorbed ovalbumin (OVA) was investigated. The aim of vaccine formulation was to maximise the amount of antigen retained on the particles and the time o f retention during incubation of the formulations in PBS at 37 degrees C. U nmodified PLA lamellae were capable of adsorbing large quantities of OVA (u p to 12.5% w/w) but major and rapid desorption occurred in PBS at 37 degree s C (80% released in 24 h). Retention of OVA on PLA lamellae was improved ( 25% released in 24 h) by precipitating the particles using aqueous sodium d eoxycholate solution (DOC-modified PLA lamellae and lyophilising the lamell ae-protein preparation after adsorption. Sustained immune responses were el icited in mice to a single sub-cutaneous injection of OVA adsorbed onto DOC -modified PLA lamellae. The level of antibodies induced and the pattern of response was similar to that induced by an alum-adsorbed OVA formulation. N ormally boosting is required to obtain high levels of antibody when OVA is adsorbed on poly(DL-lactide co-glycolide) (PLC) microspheres. The lamellar forms of PLA. may function as an efficient immunomodulator by effectively r etaining adsorbed antigen and by activating immune cells due to their irreg ular shape. PLA lamellae have potential to stimulate enhanced immune respon ses to a variety of adsorbed antigens. (C) 1999 Elsevier Science Ltd. All r ights reserved.