Animal Protection and Structural Studies of a Consensus Sequence Vaccine Targeting the Receptor Binding Domain of the Type IV Pilus of Pseudomonas aeruginosa

Abstract

One of the main obstacles in the development of a vaccine against Pseudomonas aeruginosa is the requirement that it is protective against a wide range of virulent strains. We have developed a synthetic-peptide consensus-sequence vaccine (Cs1) that targets the host receptor-binding domain (RBD) of the type IV pilus of P. aeruginosa. Here, we show that this vaccine provides increased protection against challenge by the four piliated strains that we have examined (PAK, PAO, KB7 and P1) in the A.BY/SnJ mouse model of acute P. aeruginosa infection. To further characterize the consensus sequence, we engineered Cs1 into the PAK monomeric pilin protein and determined the crystal structure of the chimeric Cs1 pilin to 1.35 Å resolution. The substitutions (T130K and E135P) used to create Cs1 do not disrupt the conserved backbone conformation of the pilin RBD. In fact, based on the Cs1 pilin structure, we hypothesize that the E135P substitution bolsters the conserved backbone conformation and may partially explain the immunological activity of Cs1. Structural analysis of Cs1, PAK and K122-4 pilins reveal substitutions of non-conserved residues in the RBD are compensated for by complementary changes in the rest of the pilin monomer. Thus, the interactions between the RBD and the rest of the pilin can either be mediated by polar interactions of a hydrogen bond network in some strains or by hydrophobic interactions in others. Both configurations maintain a conserved backbone conformation of the RBD. Thus, the backbone conformation is critical in our consensus-sequence vaccine design and that crossreactivity of the antibody response may be modulated by the composition of exposed side-chains on the surface of the RBD. This structure will guide our future vaccine design by focusing our investigation on the four variable residue positions that are exposed on the RBD surface.

Type IV Pilin Proteins: Versatile Molecular Modules

“…To explain how D regions with diverse sequences can provide similar functions, their adhesive properties were attributed to main chain-rather than side chain-based interactions (172). Those data led to a focus on development of anti-P. aeruginosa vaccines containing peptides corresponding to the D region (71,72,75,162,216). Newer information showing that the minor pilins are present in sheared pilus fractions (154,416) and that the orthologous PilC1 or PilC2 (Neisseria and Kingella) and PilY1 (Pseudomonas) proteins are potentially pilus associated and required for adherence to-and manipulation of-the host (174,204,217,288,289,384) suggests that additional studies are needed to unequivocally identify all T4aP adhesins.…”

Pili in Gram-negative and Gram-positive bacteria — structure, assembly and their role in disease

“…Goluszko et al [182] used purified E. coli Dr fimbrial antigen to vaccinate C3H/HeJ mice against an experimental UTI and demonstrated reduced mortality in vaccinated animals. Kao et al [183] have developed a synthetic-peptide consensus-sequence vaccine (Cs1) that targets the host receptor-binding domain of the Type IV pilus of P. aeruginosa. The vaccine provided increased protection against challenge by the four piliated strains PAK, PAO, KB7 and P1 in the A.BY/ SnJ mouse model of acute P. aeruginosa infection.…”

Epitope mapping immunodominant regions of the PilA protein of nontypeable Haemophilus influenzae (NTHI) to facilitate the design of two novel chimeric vaccine candidates

“…This is particularly essential when one is attempting to design a vaccine candidate for a group of microorganisms as heterogeneous as NTHI, and when there is a history for difficulties encountered using Tfp-derived strategies in vaccine development strategies for other infectious agents (i.e. N. gonorrhoea, Pseudomonas aeruginosa, Burkholderia mallei ) [16–19]. …”