THE NEISSERIA-MENINGITIDIS OUTER-MEMBRANE PROTEIN P1 PRODUCED IN BACILLUS-SUBTILIS AND RECONSTITUTED INTO PHOSPHOLIPID-VESICLES ELICITS ANTIBODIES TO NATIVE P1 EPITOPES

Class 1 outer membrane protein (Pi) of Neisseria meningitidis group B is considered a promising vaccine candidate because P1 subtype-specifi c antibodies have been shown to be protective in an animal model. We h ave previously described the production of P1 in the Gram-positive Bac illus subtilis as intracellular inclusion bodies, from which the prote in (BacP1) is easily purified (Nurminen et al., Mel. Microbiol., 1992, 2499-2506). We show here that the purified BacP1 can be reconstituted into phospholipid vesicles with the formation of the native immunodom inant surface epitopes. The detergent-solubilized, completely denature d BacP1 was fused with phospholipid-detergent micelles during detergen t removal by dialysis or gel filtration to yield protein-lipid vesicle s (liposomes). When mice were immunized with these liposomes, they pro duced high titers of antibodies reacting in a P1 subtype-specific mann er with meningococcal cells indicating the presence of conformation-de pendent P1-specific epitopes in the liposomes. The results suggest tha t a vaccine candidate for meningococcal disease could be developed fro m the BacP1-liposomes, They furthermore demonstrate the feasibility of refolding a denatured outer membrane protein, which has never been ex posed to lipopolysaccharide, into a native;like conformation.