Method for the high level expression, purification and refolding of the outer membrane group B porin proteins from Neisseria meningitidis

A method for the high level expression of the outer membrane meningococcal group B porin protein or fusion protein thereof in an E. coli host cell having a deleted omp.DELTA. gene (.DELTA.ompA), comprising:

• (a) transforming the E. coli .DELTA.ompA host cell with a vector comprising a selectable marker and a gene coding for a protein selected from the group consisting of:
• (i) a mature porin protein, and
• (ii) a fusion protein which is a mature porin protein fused to amino acids 1 to 22 of the T7 gene .phi.10 capsid protein;
• wherein said gene is operably linked to the T7 promoter;
• (b) growing the transformed host cell in a culture medium containing a selection agent, and
• (c) inducing expression of said protein;
• wherein the protein so expressed comprises more than about 2% of the total protein expressed in the host cell.