Preformulation study of the vaccine candidate P64k against Neisseria meningitidis

We have previously isolated, cloned and expressed in Escherichia coil the I pdA gene coding for a high-molecular-mass protein (P64k) common to many men ingococcal strains. P64k is an outer membrane lipoamide dehydrogenase that is highly immunogenic in animals. Here we describe a preformulation study o f the recombinant protein as a vaccine candidate against Neisseria meningit idis, in which six variants containing the candidate were tested. Three ass ays were used to identify the most suitable variant for further evaluation: percentage of adsorption, identification of P64k by SDS/PAGE, and immunoge nicity in mice. All the preformulation variants studied showed more than 98 % of adsorption of P64k on the aluminium gel. After desorption, P64k was al so identified by SDS/PAGE in the six preformulation variants. Seroconversio n was attained in all groups analysed. On the basis of these results, the m ost effective variant consisted of 20 mu g/ml P64k plus 0.5 mg/ml aluminium hydroxide.