Concentration Determination of a Recombinant Vaccine Antigen Adsorbed onto an Alum Adjuvant by Chemiluminescent Nitrogen Detection

No HeadingPurpose. A chemiluminescent nitrogen detector (CLND) has been evaluated for determining the concentration of an aluminum-adsorbed recombinant vaccine antigen.Methods. Quantification of the antigen was based upon several nitrogen-containing compounds used to calibrate the CLND. All calibrants (6.75–400 g/ml) generated linear standard curves, with slopes being directly proportional to the % nitrogen. The limit of quantification (LOQ) was determined to be 6.75 g/ml based on the performance of the antigen standard curve, and the limit of detection (LOD) was defined by setting the CLND minimum peak area to 40,000 U. The CLND was capable of analyzing antigen-adjuvant suspensions (adsorbed + unbound antigen) without any sample pretreatment. To measure unbound antigen, the suspension was centrifuged and an aliquot of supernatant removed for analysis; the difference between these two measurements was the amount of adsorbed antigen.Results. The adjuvant exhibited no significant matrix effect. Samples were analyzed in triplicate with observed relative standard deviation values ranging from 0.065% to 10.0%. The most accurate concentrations of the antigen were recovered relative to the antigen itself and to glycine as standards.Conclusion. This methodology provides a direct measurement of the concentration of a vaccine antigen adsorbed onto an aluminum adjuvant.