Conjugates of synthetic cyclic peptides elicit bactericidal antibodies against a conformational epitope on a class 1 outer membrane protein of Neisseria meningitidis

Abstract

Bactericidal antibodies directed against surface loops of class 1 outer membrane proteins play a crucial role in protection against meningitis and sepsis caused by Neisseria meningitidis. So far, all efforts to obtain protective antibodies against these apparently conformational epitopes by using linear peptide analogs have been in vain. In this study, conjugates of head-to-tail cyclic peptides encompassing the predicted top of a protective surface loop were used for immunization. A series of 18 cyclic peptides with a ring size ranging from 7 to 17 residues, conjugated to tetanus toxoid, was investigated. Antipeptide and anti-whole-cell immunoglobulin G (IgG) titers elicited by the conjugates were determined. Conjugates of three peptides, containing 14, 15, and 17 amino acid residues (peptides 7, 12, and 13, respectively), induced an anti-whole-cell titer when Quillaja saponin A was used as the adjuvant. When alum was used as the adjuvant, the conjugate of peptide 12 did not elicit an anti-whole-cell response. From the Quillaja saponin A group, some of the sera obtained with conjugates of peptides 7 and 12 and all sera obtained with the peptide 13 conjugate were bactericidal in vitro. None of the sera evoked with alum as the adjuvant showed bactericidal activity. Nonbactericidal sera contained IgG1 primarily, whereas bactericidal sera showed significant titers of IgG2a and IgG2b. Class 1 protein-derived synthetic cyclic peptides which are capable of eliciting bactericidal antibodies, such as peptide 13 derived from meningococcal strain H44/76, represent potential candidates for a (semi)synthetic vaccine against meningococcal disease.

LOSoligosaccharide modification enhances dendritic cell responses to meningococcal native outer membrane vesicles expressing a non‐toxic lipidA

“…It is likely that both Th1 and Th2 responses are important for generating immunity to meningococcus or vaccine components. Th2 is often associated with presence of IL-10 (produced by DC for example) which is important for B cell isotype switching, while Th1 responses promote production of antibody isotypes IgG2a and IgG2b which are known to be important for meningococci complement mediated killing (Hoogerhout et al, 1995;de Kleijn et al, 2001).…”

Identification and characterisation of a novel conserved outer membrane protein from Neisseria meningitidis

“…For Western immunoblot, non-NhhA-speci¢c antibodies were removed by absorbing sera against E. coli expressing MBP [7]. Bactericidal killing assays were performed essentially as previously described by Hoogerhout et al [8].…”

Solid‐phase synthesis and application of double‐fluorescent‐labeled lipopeptides, containing a CTL‐epitope from the measles fusion protein

“…Outline of the synthesis of the 5-carboxytetramethylrhodamine (TMR)-and 5-carboxy¯uorescein (FL)-labeled lipopeptide Pal-K TMR KKKRRYPDAVK FL L (7). (16,17). HPLC analysis (see below) of the crude product showed the presence of two main products with absorbency at 546 nm ( Fig.…”