1. Academic Validation
  2. Simple radiometric method for accurately quantitating epitope densities of hapten-protein conjugates with sulfhydryl linkages

Simple radiometric method for accurately quantitating epitope densities of hapten-protein conjugates with sulfhydryl linkages

  • Bioconjug Chem. 2014 Dec 17;25(12):2112-5. doi: 10.1021/bc500456z.
Eric C Peterson 1 Michael D Hambuchen Rachel L Tawney Melinda G Gunnell James L Cowell Jackson O Lay Jr Bruce E Blough F Ivy Carroll S Michael Owens
Affiliations

Affiliation

  • 1 Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205, United States.
Abstract

Control of small molecule hapten epitope densities on antigenic carrier proteins is essential for development and testing of optimal conditions for vaccines. Yet, accurate determination of epitope density can be extremely difficult to accomplish, especially with the use of small haptens, large molecular weight carrier proteins, and limited amounts of protein. Here we report a simple radiometric method that uses (14)C-labeled cystine to measure hapten epitope densities during sulfhydryl conjugation of haptens to maleimide activated carrier proteins. The method was developed using a (+)-methamphetamine (METH)-like hapten with a sulfhydryl terminus, and two prototype maleimide activated carrier proteins, bovine serum albumin (BSA) and immunocyanin monomers of keyhole limpet hemocyanin. The method was validated by immunochemical analysis of the hapten-BSA conjugates, and least-squares linear regression analysis of epitope density values determined by the new radiometric method versus values determined by matrix-assisted laser desorption/ionization mass spectrometry. Results showed that radiometric epitope density values correlated extremely well with the mass spectrometrically derived values (r(2) = 0.98, y = 0.98x + 0.91). This convenient and simple method could be useful during several stages of vaccine development including the optimization and monitoring of conditions for hapten-protein conjugations, and choosing the most effective epitope densities for conjugate vaccines.

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