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The impact on immunogenicity of the degree of adsorption of three Streptococcus pneumoniae (Sp) vaccine antigens to aluminum adjuvants was studied. The three antigens evaluated (Sp1, Sp2 and Sp3) were highly adsorbed by aluminum hydroxide adjuvant, but not adsorbed by aluminum phosphate adjuvant. All of the Sp antigens adjuvanted with aluminum hydroxide elicited higher antibody responses in mice than formulations prepared with aluminum phosphate or non-adjuvanted antigen. Varying the percent aluminum-bound Sp antigen in the formulated vaccine affected the observed antibody responses. These observations suggest that the antibody response observed for Sp antigens in this study is stimulated by a depot effect of the antigen bound to an aluminum adjuvant.

A reversibly immobilized enzyme (glucose oxidase EC 1 . 1 . 3 . 4 ) reactor coupled to a continuous flow system is used in the determination of serum glucose. The soluble enzyme is first covalently attached to an antibody. This conjugate is then introduced into a microreactor containing an immobilized antigen. The resulting immunological reaction produces an immobilized enzyme. Injection of glucose yields hydrogen peroxide, which is detected electrochemically. The reactor can be regenerated in the event of a loss of enzyme activity to within & 3 % of the original reactor activity in < 30 min by eluting the immobilized enzyme and reacting a fresh aliquot of the enzyme-labelled antibody with the same reactor. The lifetime of the reactor is more than one year, during which time the antigen remains active in binding. The sample throughout is ca. 20-30 samples per hour and the accuracy is in the order of f 3 % . The linear dynamic range for glucose is 0.01-10 mg cm-3 for a sample size of 20 mm3.

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The adsorption of three Streptococcus pneumoniae (Sp) vaccine antigens by aluminumcontaining adjuvants was studied. The antigens showed high binding affinity isotherms with aluminum hydroxide adjuvant described by the Langmuir equation but virtually no binding to aluminum phosphate adjuvant. The effects of ionic strength and ethylene glycol were evaluated to determine whether electrostatic or hydrophobic interactions were responsible for the observed binding to aluminum hydroxide, but no significant change in the adsorptive capacity was observed at either high ionic strength nor high concentrations of ethylene glycol for any of the antigens. This indicates that neither electrostatic nor hydrophobic interactions appear to be responsible for the observed binding, which means that ligand exchange may be the primary mechanism for this interaction. Further studies to evaluate the ability to elute a Sp antigen from aluminum hydroxide using fibrinogen (adsorptive coefficient 2.2 mL/µg) as a competitive protein resulted in evidence that Sp antigen follows the trend that proteins with higher adsorptive coefficients are able to displace those with lower adsorptive coefficients. It was also noted that the Sp antigens and α-lactalbumin (adsorptive coefficient 1.8 mL/µg) have similar adsorptive coefficients indicative of high affinity binding isotherms but do not contain phosphate, which has previously been used to explain ligand exchange for such proteins as α-casein and hepatitis B surface antigen (HBsAg). Further investigations using α-lactalbumin as a model protein may elucidate the binding interaction between the antigens in this study and aluminum adjuvants.