Mimotopes of the Vi Antigen ofSalmonella entericaSerovar Typhi Identified from Phage Display Peptide Library

Abstract

The capsular polysaccharide Vi antigen (ViCPS) is an essential virulence factor and also a protective antigen of Salmonella enterica serovar Typhi. A random 12-mer phage-displayed peptide library was used to identify mimotopes (epitope analogues) of this antigen by panning against a ViCPS-specific monoclonal antibody (MAb) ATVi. Approximately 75% of the phage clones selected in the fourth round carried the peptide sequence TSHHDSHGLHRV, and the rest of the clones harbored ENHSPVNIAHKL and other related sequences. These two sequences were also obtained in a similar panning process by using pooled sera from patients with a confirmed diagnosis of typhoid fever, suggesting they mimic immunodominant epitopes of ViCPS antigens. Binding of MAb ATVi to the mimotopes was specifically blocked by ViCPS, indicating that they interact with the same binding site (paratope) of the MAb. Data and reagents generated in this study have important implications for the development of peptide-base diagnostic tests and peptide vaccines and may also provide a better understanding of the pathogenesis of typhoid fever.

A phage-displayed cyclic peptide that interacts tightly with the immunodominant region of hepatitis B surface antigen

“…There are many examples demonstrating the potential of phage-born peptides as potential diagnostic reagents. These include a 9-mer peptide fused to the gpVIII protein for the detection of cucumber mosaic virus (Gough et al, 1999), a cyclic heptapeptide on the gpIII protein for the pathotyping of Newcastle disease virus (Ramanujam et al, 2004) and a 12-mer gpIII protein for the identification of the anti-Vi antigen of Salmonella enerica Serovar Typhi (Tang et al, 2003). These together with the results in this study demonstrate that phage displayed peptides show promise as reagents for detection of biological samples.…”

Immunological evaluation of Vi capsular polysaccharide of Salmonella enterica subsp. Typhi vaccine by serum bactericidal assay

“…The classical typhoid+paratyphoid A+paratyphoid B (TAB) vaccine and oral Salmonella enterica subsp. Typhi (S. Typhi) Ty21a vaccine offer good immunity production in humans, but neither is a complete and ideal vaccine, resulting in the necessity for further studies (Mastroeni & Ménager, 2003;Tang et al, 2003). It has been shown that the S. Typhi Vi capsular polysaccharide (Vi-CPS) subunit vaccine can prevent typhoid fever.…”

“…It has been shown that the S. Typhi Vi capsular polysaccharide (Vi-CPS) subunit vaccine can prevent typhoid fever. A single intramuscular injection of this vaccine conferred about 65 and 72 % protection in South Africa and Nepal, respectively (Acharya et al, 1987;Klugman et al, 1987;Szu et al, 1994;Tang et al, 2003;Chibber & Bhardwaj, 2004). The Vi-CPS vaccine has now been licensed in .93 countries worldwide, although it is not commonly used as part of vaccination programmes in developing countries.…”

“…The antibody response to the Vi-CPS vaccine is measured using various serological methods. Serum bactericidal antibody activity has shown that there is a direct correlation between application of the Vi-CPS vaccine and the induction of both natural and vaccine-induced immunity to typhoid fever (Yang et al, 2001;Tang et al, 2003;Canh et al, 2004;Fadeel et al, 2004;Wain et al, 2005). The induction of complement-dependent bactericidal antibodies after vaccination with Vi-CPS has been widely accepted as evidence of the potential efficacy of this vaccine (WHO, 1981).…”

Purification of bacteriophage M13 by anion exchange chromatography

“…Currently, bacteriophage M13 has been used widely in phage display technology and many peptides and proteins have been displayed successfully on the surface of the particle [6]. The displayed peptides and proteins have been applied in various fields of study including protein-protein interactions [7][8][9], identification of mimotopes for the development of vaccines [10,11], investigation of immune response [12,13], evaluation of small molecules drug candidates [14,15], identifying of peptide ligands for a variety of receptor ligands [16], and development of diagnostic reagents [6,[17][18][19][20]. Recently, M13 has been studied for its uses in nanostructures and nanotechnology for developing nanowires, nanosized energy storage unit and biocomposite fibers [21][22][23].…”