RESUMEN
The effect of adjusting the pH of a model ovalbumin (iep = 4.7) and aluminum hydroxide adjuvant (iep = 11.5) vaccine or a model lysozyme (iep = 11.4) and aluminum phosphate adjuvant (iep = 5.0) vaccine to values ranging from 3 to 11 was studied. The model vaccine prepared at pH 7.4 served as the reference. Additional adsorption of ovalbumin occurred in the pH range 7.4 to 4.1. Elution of ovalbumin occurred when the pH was adjusted to values above 7.4 or below 4.1. Maximum elution occurred at pH 2.9 and 11.0. Elution of lysozyme from aluminum phosphate adjuvant occurred when the pH was adjusted to any value other than the reference pH of 7.4. More lysozyme was eluted at pH 2.9 than at pH 11.0. The adsorption/elution behavior could be explained by the effect of pH on: (1) the ionization state of the protein, 2) the solubility of the adjuvant, and (3) the electrostatic interaction between the protein and adjuvant. Copyright 1998 Academic Press.
RESUMEN
The elutability of proteins from adjuvants in model vaccines composed of ovalbumin adsorbed by aluminum hydroxide adjuvant or lysozyme adsorbed by aluminum phosphate adjuvant following treatment with surfactant solutions was studied. Nonionic (Triton X-100, lauryl maltoside), zwitterionic (lauryl sulfobetaine), anionic (sodium dodecyl sulfate), and cationic (cetylpyridinium chloride, dodecyltrimethylammonium chloride) surfactants were investigated. Cetylpyridinium chloride produced the greatest degree of elution (60%) of ovalbumin from aluminum hydroxide adjuvant. Sodium dodecyl sulfate completely eluted lysozyme from aluminum phosphate adjuvant. The effectiveness of surfactants in removing preadsorbed proteins was directly related to their ability to denature the protein. Micellar solubilization and electrostatic repulsion may also contribute to desorption. Copyright 1998 Academic Press. Copyright 1998Academic Press
RESUMEN
The moisture sorption isotherm of amorphous spray-dried aluminum hydroxycarbonate (SDAHC) at 25°C revealed that moisture sorption increased sharply when the relative humidity exceeded 80%. The physical and chemical stability of SDAHC was studied for 1 year at 25°C and 0, 11, 54, 84, or 100% RH. The results were interpreted to reveal that two mechanisms affect the properties of SDAHC at 25°C. The sample stored at 0% RH did not exhibit any significant changes during the 1-year study period. The surface area and rate of acid neutralization decreased when samples were stored at 11 or 54% RH, but the material remained amorphous. This change is believed to be due to aggregation and cementation of particles. Much larger changes in surface area and the rate of acid neutralization occurred in the samples aged at 84 or 100% RH. Under these humidity conditions, polymorphic transformations occurred in addition to aggregation and cementation. X-ray diffraction indicated that microcrystalline boehmite was an intermediate phase. The stable polymorph was bayerite, which is believed to form due to the high surface pH produced by water sorption at 84 or 100% RH. The moisture sorption isotherm was useful in identifying the humidity conditions which resulted in high moisture sorption. Polymorphic transformations were only detected when the SDAHC was aged under these humidity conditions.
