Bayer School of Natural and Environmental Sciences
Peter A. Castric
Alan W. Seadler
Joseph R. McCormick
glycoconjugate, glycosylation, pili, Pseudomonas
Pseudomonas aeruginosa expresses type IV pili, which are polymeric fibrous surface appendages extending from the poles of the cell that function in adhesion and surface motility. The monomeric pilus subunit, pilin, of P. aeruginosa 1244 is glycosylated with an oligosaccharide that is structurally identical to the O-antigen repeating unit of this organism. Work presented here identifies the pilin structures necessary for glycosylation. Results suggested that the C-terminal Ser of pilin is the major glycosylation recognition feature, and this residue cannot be substituted at its carboxyl group. While no other specific recognition features are present, the pilin surface must be compatible with the reaction apparatus for glycosylation to occur. Further work was conducted to investigate glycan substrate recognition in the 1244 pilin glycosylation reaction. Data suggested that the pilin glycosylation substrate recognition features lie within the reducing-end moiety of the O-repeat, and structures of the remaining sugars are irrelevant. Additional research was carried out to assess the role of the P. aeruginosa 1244 pilin glycan in pathogenesis. Competition index analysis using a mouse respiratory model comparing strain 1244 and the pilO isogenic knockout strain, 1244G7 indicated that the presence of the pilin glycan allowed for significantly greater survival in the lung environment. This suggested that the pilin glycan is a significant virulence factor and may aid in the establishment of infection. As the pilin glycan and the O-subunit are structurally identical, mice were immunized with strain 1244 glycosylated pili to test if vaccination with these fibers provided O-antigen-specific protection. Using either the mouse respiratory or the thermal injury model, protection from challenge with a pilus-deficient O-antigen-producing 1244 mutant was observed. These results provide evidence that the pilin glycan stimulates a protective response that targets the O-antigen, suggesting that this system could be utilized as a means to develop numerous protective anti-gram-negative bacterial bioconjugate vaccines.
Horzempa, J. (2006). Pseudomonas aeruginosa 1244 pilin glycosylation: substrate specificity, glycan functionality, and application for vaccine development (Doctoral dissertation, Duquesne University). Retrieved from https://dsc.duq.edu/etd/664