The purpose of this study was to develop a new combined vaccine. Aluminium hydroxide gel (AH) at fixed concentration of 1.67%w/v, pH 6.5 was individually adsorbed with diphtheria toxoid (DT), tetanus toxoid (TT) or JE antigen at various processing variables: temperature 5, 15, 25 and 37C; mixing speed 200, 300, 400 and 500 rpm; mixing time 1, 5, 12 and 24 hours It indicated that the optimal percentage of adsorption of each antigen on AH was at temperature 5C; mixing speed 400 rpm; mixing time 5 hours. The antigen contents and physical stability of combined preparations were evaluated after storage at 2-8 C for 4 months. The antigen contents of combined preparations analyzed by ELISA showed more DT, PT and JE content from formulation of separate adsorption than that of competitive method but more TT content from formulation of competitive adsorption than that of separate method. Adsorption process affected the antigen content of DT and JE but did not affect TT and PT content. Morphology of adsorbed AH by two adsorption processes by SEM showed spherical complex particle and had small fragment likely to be antigens attached on the surface of AH. After storage for 4 months, the particle sizes were decreased because the structure of AH was broken while the principle peaks of adsorbed AH demonstrated by IR spectra and X-ray diffractograms probable appeared which indicated that the two adsorption processes had no effect on their chemical structures.
