TheNeisseria meningitidisouter membrane protein P1 produced inBacillus subtilisand reconstituted into phospholipid vesicles elicits antibodies to native P1 epitopes

Abstract

Class 1 outer membrane protein (P1) ofNeisseria meningitidisgroup B is considered a promising vaccine candidate because P1 subtype–specific antibodies have been shown to be protective in an animal model. We have previously described the production of P1 in the Gram–positiveBacillus subtilisas intracellular inclusion bodies, from which the protein (BacP1) is easily purified (Nurminenet al., Mol. Microbiol., 1992, 2499–2506). We show here that the purified BacP1 can be reconstituted into phospholipid vesicles with the formation of the native immunodominant surface epitopes. The detergent–solubilized, completely denatured BacP1 was fused with phospholipid–detergent micelles during detergent removal by dialysis or gel filtration to yield protein–lipid vesicles (liposomes). When mice were immunized with these liposomes, they produced high titers of antibodies reacting in a P1 subtype–specific manner with meningococcal cells indicating the presence of conformation–dependent P1–specific epitopes in the liposomes. The results suggest that a vaccine candidate for meningococcal disease could be developed from the BacP1–liposomes. They furthermore demonstrate the feasibility of refolding a denatured outer membrane protein, which has never been exposed to lipopolysaccharide, into a native–like conformation.