title: Development and use of a novel in vitro assay for testing of diphtheria toxoid in combination vaccines.
abstract: Testing of diphtheria vaccines for routine lot release relies heavily on the use of in vivo potency assays. However, consistency of production is also recognised as an important feature of vaccine manufacture, and in vitro assays are superior to in vivo assays for providing this information. In adsorbed vaccines, antigen and adjuvant are the major components contributing to immunogenicity and are therefore critical factors to be evaluated as part of consistency testing. Here we describe a simple and sensitive Enzyme Linked Immunosorbent Assay (ELISA) which has been developed to quantify diphtheria toxoid antigen in combined vaccine products and can also be used to monitor the degree of adsorption. This assay can be applied to a variety of multi-component vaccines and is robust, specific and highly sensitive, with a limit of quantification of approximately 0.005 Lf/ml. The antigen assay is an excellent test to characterise vaccines and monitor trends in production. For well established vaccines, the antigen assay could be used alongside other in vitro methods to provide a more informative product profile, with the ultimate aim of reducing the requirement for in vivo potency assays and therefore the number of animals required for routine batch release testing.
authors.affiliation: Division of Bacteriology, National Institute for Biological Standards and Control, Health Protection Agency, South Mimms, Potters Bar, Hertfordshire EN6 3QG, UK.
authors.forename: Laura
authors.initials: L
authors.lastname: Coombes
authors.forename: Paul
authors.initials: P
authors.lastname: Stickings
authors.forename: Rob
authors.initials: R
authors.lastname: Tierney
authors.forename: Peter
authors.initials: P
authors.lastname: Rigsby
authors.forename: Dorothea
authors.initials: D
authors.lastname: Sesardic
mesh_terms: D000818:Animals; D004168:Diphtheria Toxoid / Q000032:analysis* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000592:standards; D006168:Guinea Pigs; D006801:Humans; D051381:Rats; D012680:Sensitivity and Specificity; D017778:Vaccines, Combined / Q000032:analysis / Q000276:immunology
chemical_list: D004168:Diphtheria Toxoid; D017778:Vaccines, Combined