Relationships among physico-chemical and biological tests for a synthetic Hib–TT conjugate vaccine

The relationships among physico-chemical and biological tests were evaluated in this study for Cuban Hib vaccine, a tetanus toxoid conjugated with a polysaccharide obtained from chemical synthesis, in order to estimate the biological significance of the relevant physico-chemical assays for lot released. In order to get samples with theoretical different potencies, Hib–TT samples were stored at −20, 4, 25, 37 and 70 °C for 5 weeks and after they were evaluated by HPLC and Orcinol methods and for immunogenicity and bactericidal activity. We found strong relationships between HPLC and free PRP level (r2 = 0.9571), anti-PRP antibodies and bactericidal activity (r2 = 0.9649) and free PRP content and anti-PRP antibodies titres (r2 = 0.7671). A lower correlation was found for HPLC and anti-PRP titres (r2 = 0.5996). We demonstrate that it is possible to monitor this new product combining physico-chemical and biological tests in order to contribute to its characterisation.