Safety and preliminary immunogenicity of the recombinant outer membrane protein P64k of Neisseria meningitidis in human volunteers

P64k is a meningococcal protein from Neisseria meningitidis that has been o btained by recombinant DNA technology. Recombinant P64k has been extensivel y characterized by physicochemical and immunological methods. Lately this p rotein has been found to act as a versatile immunological carrier for weak antigens in mice. In the present work, a Phase I clinical trial was carried out in healthy volunteers who received three inoculations of either placeb o or recombinant P64k (20 or 50 mug). No severe adverse events occurred dur ing the trial. Only mild adverse events in ten volunteers were observed. At I month after the third dose, 15 out of 18 volunteers (83.3%) who received the recombinant antigen had a P64k-specific antibody titre greater than or equal to 1 : 100, as detected by ELISA. A fourth dose, given 9 months afte r the third one, elicited a potent booster immune response in P64k vaccinee s. Accordingly, these P64k formulations were considered safe and immunogeni c in healthy human volunteers.