EXPRESSION OF NEISSERIA-MENINGITIDIS CLASS-1 PORIN AS A FUSION PROTEIN IN ESCHERICHIA-COLI - THE INFLUENCE OF LIPOSOMES AND ADJUVANTS ON THE PRODUCTION OF A BACTERICIDAL IMMUNE-RESPONSE

High level expression of meningococcal class 1 protein was achieved in Escherichia coli using the p-GEMEX-1 vector, in which the protein was expressed in inclusion bodies (IB), as a fusion with the bacteriophag e T7 gene 10 capsid protein. The fusion protein (FP) was engineered wi th a factor Xa protease site between the gene 10 and class 1 protein, but treatment with the enzyme resulted in cleavage at additional sites within the class 1 protein. Since it was not possible to remove the l eader protein, the intact FP provided an alternative antigen for immun ization. Antisera raised to FP, solubilized from IB and incorporated i nto liposomes, generated a subtype-specific response which was weakly bactericidal for meningococci. In order to remove any possible effect of E, coli LPS present in IB, the FP was further purified by SDS-PAGE and incorporated into liposomes, either alone or in combination with t he adjuvants monophosphoryl lipid A or muramyl dipeptide. The incorpor ation of adjuvants in liposomes resulted in stimulation of the overall immune response to FP, but the resulting antisera were not bactericid al. However an effective bactericidal response was obtained with the p urest preparation of FP in liposomes, without any additional adjuvants , revealing that attempts to increase further the immunogenicity of su ch antigens must not be at the expense of interfering with optimal pro tein folding. (C) 1996 Academic Press Limited