The major outer membrane protein of Chlamydia trachomatis: critical binding site and conformation determine the specificity of antibody binding to viable chlamydiae

Abstract

The major outer membrane protein (MOMP) is the prime candidate for the development of a chlamydial vaccine. Antibodies to the subspecies-specific epitope neutralize chlamydial infection. Monoclonal antibodies (MAbs) to this epitope were prepared either by immunization with whole chlamydiae or with a 16 amino acid synthetic peptide. The critical binding site on the subspecies epitope for these MAbs was determined to single amino acid resolution using several hundred solid-phase peptides. A frame shift of just one amino acid in critical binding site completely prevented antibody binding to viable chlamydiae. A single MAb to whole organisms was capable of spanning both the surface-exposed, conformation-dependent, subspecies epitope and a buried, conformation-independent species epitope some 10 A distant. Immunization with peptide generated an MAb with reduced binding constraints which permitted the antibody to bind with broadened species-specificity at the subspecies binding site. The results show for the first time the importance of both critical binding site and conformation at the subspecies epitope. We suggest that the conformational flexibility of short, epitopic peptide vaccines may in some cases be advantageous, giving rise to extended specificity not attained with the natural protein.

Functional and structural mapping of Chlamydia trachomatis species-specific major outer membrane protein epitopes by use of neutralizing monoclonal antibodies

“…It was observed that the strength of this signal decreased with continued repeat cycling of the peptide-containing pins. A similar observation with certain peptides has been reported by Conlan et al (9).…”

“…The DNA coding for the MOMP of C. trachomatis has been sequenced, and the antigenic determinants of the protein have been mapped with several monoclonal antibodies (MAbs) (1,6,8,9,31). This protein is composed of four variable domains (VDs), which are interspersed between conserved regions (30).…”

“…This protein is composed of four variable domains (VDs), which are interspersed between conserved regions (30). The epitopes for MAbs that are serovar, subspecies, and species specific have been mapped to these VDs (1,6,8,9,31). In general, it is believed that antibodies directed to serovar-and subspecies-specific epitopes are protective, while those recognizing speciesspecific epitopes are not (15,39).…”

Surface-exposed Epitopes on the Major Outer-membrane Protein of Chlamydia trachomatis Defined with Peptide Antisera

“…Epitopic domains within the variable segments of MOMP have been mapped to linear sequences of 9 to 11 amino acids using murine monoclonal antibodies and either free-solution peptides (Stephens et al, 1988) or expressing Agtl 1 recombinants (Baehr et al, 1988). Epitope localization and the structural requirements for antibody binding have been further defined to single amino acid resolution by solid-phase peptide mapping (Conlan et al, 1988(Conlan et al, , 1989. Typespecific epitopes have been demonstrated in both VSl for serovar A (Baehr et d., 1988) and VS2 for serovars B, C, L1 and L2 (Baehr etal., 1988;Conlan et al, 1988;Stephens et al, 1988) whilst subspecies-and species-specific epitopes were consistently found in VS4 (Baehr et al, 1988;Conlan et al, 1988 ;Stephens et al, 1988).…”

“…The critical binding sites of these antibodies were therefore investigated using the Geysen (1984) method of epitope mapping as we have previously described (Conlan et al, 1988(Conlan et al, ,1989. The results are presented in Fig.…”