PLoS One. 2016 Mar 18;11(3):e0150320. doi: 10.1371/journal.pone.0150320. eCollection 2016.

Streptococcus pneumoniae Cell-Wall-Localized Phosphoenolpyruvate Protein Phosphotransferase Can Function as an Adhesin: Identification of Its Host Target Molecules and Evaluation of Its Potential as a Vaccine.

Mizrachi Nebenzahl Y1,2,3, Blau K1,2,3, Kushnir T1,2,3, Shagan M1,2,3, Portnoi M1,2,3, Cohen A1,2,3, Azriel S1,2,3, Malka I1,2,3, Adawi A1,2,3, Kafka D1,2,3, Dotan S4, Guterman G1,2,3, Troib S1,2,3, Fishilevich T1,2,3, Gershoni JM5, Braiman A2, Mitchell AM6, Mitchell TJ5, Porat N1,2,3, Goliand I7,8,Chalifa Caspi V7, Swiatlo E9, Tal M4, Ellis R4, Elia N7,8, Dagan R3.

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Abstract

In Streptococcus pneumonia, phosphoenolpyruvate protein phosphotransferase (PtsA) is an intracellular protein of the monosaccharide phosphotransferase systems. Biochemical and immunostaining methods were applied to show that PtsA also localizes to the bacterial cell-wall. Thus, it was suspected that PtsA has functions other than its main cytoplasmic enzymatic role. Indeed, recombinant PtsA and anti-rPtsA antiserum were shown to inhibit adhesion of S. pneumoniae to cultured human lung adenocarcinoma A549 cells. Screening of a combinatorial peptide library expressed in a filamentous phage with rPtsA identified epitopes that were capable of inhibiting S. pneumoniae adhesion to A549 cells. The insert peptides in the phages were sequenced, and homologous sequences were found in human BMPER, multimerin1, protocadherin19, integrinβ4, epsin1 and collagen type VIIα1 proteins, all of which can be found in A549 cells except the latter. Six peptides, synthesized according to the homologous sequences in the human proteins, specifically bound rPtsA in the micromolar range and significantly inhibited pneumococcal adhesion in vitro to lung- and tracheal-derived cell lines. In addition, the tested peptides inhibited lung colonization after intranasal inoculation of mice with S. pneumoniae. Immunization with rPtsA protected the mice against a sublethal intranasal and a lethal intravenous pneumococcal challenge. In addition, mouse anti rPtsA antiserum reduced bacterial virulence in the intravenous inoculation mouse model. These findings showed that the surface-localized PtsA functions as an adhesin, PtsA binding peptides derived from its putative target molecules can be considered for future development of therapeutics, and rPtsA should be regarded as a candidate for vaccine development.

PMID: 26990554 [PubMed - in process]