The in vitro displacement of adsorbed model antigens from aluminium-containing adjuvants by interstitial proteins

Vaccines prepared by adsorbing an antigen onto an aluminium-containing adju vant are usually administered by intramuscular or subcutaneous injection. T he vaccine then comes in contact with interstitial fluid which contains pro teins. In vitro displacement studies were performed to determine whether an tigens, which are adsorbed to aluminium-containing adjuvants, can be displa ced by interstitial proteins. It was found that when previously adsorbed mo del antigens such as lysozyme or myoglobin were exposed to interstitial pro teins such as albumin or fibrinogen that extensive displacement occurred. A factorial study of the displacement of myoglobin from aluminium hydroxide adjuvant by albumin was performed. The displacement occurred rapidly with t he majority of the displacement occurring in less than 15 min. Whether the concentration of the adsorbed myoglobin was above or below the adsorptive c apacity of the aluminium hydroxide adjuvant affected the amount which could be displaced. Less myoglobin was displaced when the concentration was belo w the adsorptive capacity. The age of the model vaccine (1, 2 or 7 days) pr ior to exposure to the interstitial protein did not influence the amount of myoglobin that was displaced. The affinity of model antigens and interstit ial proteins for aluminium hydroxide or aluminium phosphate adjuvant was ch aracterized by the adsorption coefficient in the Langmuir equation. In ever y case studied, the protein having the larger adsorption coefficient was ab le to displace the protein with the smaller adsorption coefficient. (C) 199 9 Published by Elsevier Science Ltd. All rights reserved.