Potentiation of the immune response with aluminum-containing adjuvants: I. Distribution of adsorbed antigen in mono-valent and combination vaccines; II. Role of antigen adsorption in antigen internalization by dendritic cells.

摘要

The distribution of antigens in mono-valent and combination vaccines was studied by conjugating green and red fluorescent probes to model antigens. The model antigens were alpha-casein, bovine serum albumin (BSA), and myoglobin. Recombinant protective antigen (rPA), the antigen in the 2 nd generation anthrax vaccine, was also investigated. In the mono-valent vaccine systems, antigen adsorption occurred within 1 minute and uniform surface coverage of the adjuvant aggregates was observed within one hour. Content uniformity in all systems was achieved through the cycle of de-aggregation and re-aggregation of the aluminum hydroxide adjuvant aggregates caused by mixing.; For the combination vaccines, both antigens were adsorbed separately to aluminum hydroxide adjuvant prior to combination. Following combination, as in the mono-valent systems, cycles of aggregation and de-aggregation occurred due to mixing, which led to uniform distribution of both antigens. In conclusion, content uniformity should not be an issue during production of mono-valent or combination vaccines as long as adequate mixing procedures are followed.; The efficiency of antigen internalization by dendritic cells through pinocytosis and phagocytosis was compared. Dendritic cells were incubated with either a solution of alpha-casein or alpha-casein adsorbed to aluminum hydroxide adjuvant. Internalization through phagocytosis resulted in 4 times the fluorescence intensity within the dendritic cell as pinocytosis. Therefore, it is desirable for the antigen to remain adsorbed to aluminum hydroxide adjuvant following administration to take advantage of the phagocytosis mechanism of internalization by dendritic cells.; Dendritic cells were also incubated with alpha-casein adsorbed to aluminum phosphate adjuvant and two levels of phosphate-treated aluminum hydroxide adjuvant. All three treatments resulted in greater internalization efficiency when compared to aluminum hydroxide adjuvant with aluminum phosphate adjuvant having the highest internalization efficiency. The increase in internalization efficiency over aluminum hydroxide adjuvant is most likely due to the smaller aggregate size resulting from these treatments. In conclusion, maximum antigen internalization by dendritic cells occurs when antigen remains adsorbed to an aluminum-containing adjuvant following administration and the aggregate size of the adjuvant is optimum for phagocytosis.