Immunization with synthetic peptides containing epitopes of the class 1 outer-membrane protein of Neisseria meningitidis: production of bactericidal antibodies on immunization with a cyclic peptide

Abstract

The class 1 outer-membrane protein of Neisseria menigitidis is the target for subtype-specific, bactericidal monoclonal antibodies (mAbs). The epitopes recognized by these antibodies have been mapped previously to linear peptides corresponding to the sequences thought to be exposed at the apices of surface-exposed loops of the protein.In this work several synthetic peptides containing the subtype P1.16b epitope have been synthetized with the aim of inducing a polyclonal immune response resembling the reactivity of the mAbs. Initially, peptides of 9 and 15 amino acid residues were synthesized and used for immunization after coupling to a carrier protein. The reactivity of the resulting antisera, with synthetic linear decapeptides, resembled that seen in previous epitope mapping experiments with the protective mAbs. However, despite the induction of antibodies having the desired specificity, the antisera reacted poorly with the native protein in outer membranes, and were non-bactericidal. A 36mer peptide, consisting of the entire surface-exposed loop 4 of the class 1 protein was then synthesized and used for immunization as (i) free peptide, (ii) peptide coupled to carrier and (iii) peptide subjected to cyclization, in an attempt to restrict it to conformations that might more closely resemble the native loop structure. In contrast to antisera raised against linear peptides, antibodies raised by immunization with the 36mer cyclic peptide, did not react with linear peptides recognized by the mAbs, but instead appeared to recognize conformational determinants. This antiserum promoted complement-mediated bactericidal killing of the homologous meningococcal strain, demonstrating the potential of synthetic peptide immunogens for inducing a protective immune response against group B meningococci.

Structural comparison and epitope analysis of outer-membrane protein PIA from strains of Neisseria gonorrhoeae with differing serovar specificities

“…The current study confirms the accessibility of this region to antibody attack and identifies additional potential immunogens. In addition, the localization of epitopes at the apices of the predicted loops suggests that, as has been demonstrated with meningococcal class 1 protein (Christodoulides et al, 1993), modification of peptides to mimic more accurately the loop structure of the native protein, may result in a considerably more effective immune response.…”

“…The epitope mapping studies of PIB and class 1 protein have lead to the production of bactericidal antibodies following immunization with synthetic peptides containing the epitopes Christodoulides et al, 1993). A recent study involving immunization with a synthetic peptide containing part of loop 1 from PIA produced sera which were bactericidal for several strains when tested at relatively high concentrations (Elkins et al, 1992).…”

Immunogenicity of Peptide-vaccine Candidates Predicted by Molecular Dynamics Simulations

“…In contrary, free molecular dynamics simulations proved to be capable of assessing the competence of the peptide designs correctly. Contrary to previous trial-and-error work on this epitope, 5,6 this method could select a peptide as having optimal conformational properties. This peptide A was the only peptide that induced a high, cross-reactive and bactericidal antibody titer in an immunization experiment in mice.…”

“…For this subtype, immunogenic, cyclic peptides of 15 -35 amino acid residues have been discovered by empirical research. 5,6 The crystal structure of a Fab fragment from a bactericidal antibody specific for this subtype in complex with a linear peptide ( P1 TKDTNNNL P8 , corresponding , as observed in complex with a Fab fragment from a bactericidal antibody against N. meningitidis subtype P1.16 in a crystal structure. 17 Peptide-vaccine candidates were designed to mimic this conformation; designs are represented schematically using the one-letter code for amino acids in (c); asterisks indicate the site for attachment to carrier protein tetanus toxoid.…”

Meningococcal disease: -- A review based on a symposium held on 11 July 1992 at the Liverpool School of Tropical Medicine

“…Epitope mapping experiments with synthetic peptides reveal that the protective MAbs recognise antigenic determinants at the tips of these loops, which are the longest and, hence, most accessible to the immune lg9 This detailed knowledge of the structure and immunochemistry of the class 1 protein has permitted studies designed to target the immune response directed to these protective epitopes. 200 Short peptides have been chemically synthesised to contain the epitope at the top of loop 4, coupled to carrier protein and used for immunisation. Despite inducing a good immune response to the immunising agent the resulting antisera reacted poorly with the native outer membranes and were nonbactericidal.…”