Exploiting Antigenic Diversity for Vaccine Design

Abstract

We present an interdisciplinary approach that, by incorporating a range of experimental and computational techniques, allows the identification and characterization of functional/immunogenic domains. This approach has been applied to ArtJ, an arginine-binding protein whose orthologs in Chlamydiae trachomatis (CT ArtJ) and pneumoniae (CPn ArtJ) are shown to have different immunogenic properties despite a high sequence similarity (60% identity). We have solved the crystallographic structures of CT ArtJ and CPn ArtJ, which are found to display a type II transporter fold organized in two ␣-␤ domains with the arginine-binding region at their interface. Although ArtJ is considered to belong to the periplasm, we found that both domains contain regions exposed on the bacterial surface. Moreover, we show that recombinant ArtJ binds to epithelial cells in vitro, suggesting a role for ArtJ in host-cell adhesion during Chlamydia infection. Experimental epitope mapping and computational analysis of physicochemical determinants of antibody recognition revealed that immunogenic epitopes reside mainly in the terminal (D1) domain of both CPn and CT ArtJ, whereas the surface properties of the respective binding-prone regions appear sufficiently different to assume divergent immunogenic behavior. Neutralization assays revealed that sera raised against CPn ArtJ D1 partially reduce both CPn and CT infectivity in vitro, suggesting that functional antibodies directed against this domain may potentially impair chlamydial infectivity. These findings suggest that the approach presented here, combining functional and structure-based analyses of evolutionary-related antigens can be a valuable tool for the identification of crossspecies immunogenic epitopes for vaccine development.

Structural and Biochemical Characterization of NarE, an Iron-containing ADP-ribosyltransferase from Neisseria meningitidis

“…Epitope Mapping with Monoclonal Antibodies-The epitope mapping protocols are based on the approach described by Peter and Tomer (27), which we adapted in two different protocols used here (28).…”

Induction of protective immunity against Chlamydia muridarum intravaginal infection with the chlamydial immunodominant antigen macrophage infectivity potentiator

“…Some of these antigens, either alone or in combination with other chlamydial antigens and immunostimulatory adjuvants, have been tested in various model systems and found to induce partial protection against chlamydial challenge infection [22,25,26,37–39]. However, the protection efficacy by some of these antigens against both lower genital tract infection and upper genital tract pathology has not been systematically evaluated using the C. muridarum urogenital infection mouse model.…”

EsiB, a Novel Pathogenic Escherichia coli Secretory Immunoglobulin A-Binding Protein Impairing Neutrophil Activation

“…Secretory IgA was coupled onto the surface of Dynabeads, and these were then used to capture the epitope-containing peptide. Peptide mixtures of EsiB were obtained by partial digestion with trypsin and GluC, independently, in 100 mM ammonium bicarbonate buffer at 37°C for 3 h. The immunocapturing procedure was carried out as described previously (26). Briefly, a 25-µl suspension of SIgA-coated beads was washed twice with PBS using a magnet and resuspended to the initial volume.…”