PSEUDOMONAS-AERUGINOSA OUTER-MEMBRANE PROTEIN OPRF AS AN EXPRESSION VECTOR FOR FOREIGN EPITOPES - THE EFFECTS OF POSITIONING AND LENGTH ON THE ANTIGENICITY OF THE EPITOPE

OprF, the major outer membrane (OM) protein of Pseudomonas aeruginosa, has been proposed to be comprised of a series of beta-strands separat ed by periplasmic or surface-exposed loop regions. In this study, a si mple malarial epitope was used to demonstrate that OprF can be used as an expression vector to present foreign peptide sequences, namely, th e 4-amino-acid (aa) repeating epitope (Asn-Ala-Asn-Pro = NANP) of the circumsporozoite protein of the human malarial parasite Plasmodium fal ciparum. Eight permissive sites, that allowed the expression and surfa ce exposure of the malarial epitope, were identified throughout OprF. Using a monoclonal antibody (mAb) specific for the malarial epitope, w e investigated the effects of positioning and length of the epitope on its antigenicity in the OprF expression vector system. It was demonst rated that the malarial epitope inserted at aa(26) was significantly m ore reactive with the epitope-specific mAb (i.e., more antigenic) when assayed in the context of whole cells whereas those at aa(213) and aa (290) were more antigenic when assayed in the OM. The malarial epitope inserted at aa(188) and aa(196) was moderately antigenic, while this epitope inserted at aa(215) and aa(310) showed low antigenicity with t he same mAb in both whole cell and OM assays. For two insertion sites, aa(26) and aa(213), we demonstrated that the insertion of multiple co pies of the epitope enhanced reactivity with the malarial epitope-spec ific mAb. These data are discussed with respect to the local OprF sequ ences into which the epitope was inserted.