Abstract
The V-antigen, a virulence-associated protein, was first identified in Yersinia pestis more than half a century ago. Since then, other V-antigen homologs and orthologs have been discovered and are now considered as critical molecules for the toxic effects mediated by the type III secretion system during infections caused by various pathogenic Gram-negative bacteria. After purifying recombinant V-antigen proteins, including PcrV from Pseudomonas aeruginosa, LcrV from Yersinia, LssV from Photorhabdus luminescens, AcrV from Aeromonas salmonicida, and VcrV from Vibrio parahaemolyticus, we developed an enzyme-linked immunoabsorbent assay to measure titers against each V-antigen in sera collected from 186 adult volunteers. Different titer-specific correlation levels were determined for the five V-antigens. The anti-LcrV and anti-AcrV titers shared the highest correlation with each other with a correlation coefficient of 0.84. The next highest correlation coefficient was between anti-AcrV and anti-VcrV titers at 0.79, while the lowest correlation was found between anti-LcrV and anti-VcrV titers, which were still higher than 0.7. Sera from mice immunized with one of the five recombinant V-antigens displayed cross-antigenicity with some of the other four V-antigens, supporting the results from the human sera. Thus, the serum anti-V-antigen titer measurement system may be used for epidemiological investigations of various pathogenic Gram-negative bacteria.
Highlights
The type III secretion system (TTSS) plays a major role in the virulence of many Gram-negative bacteria [1,2,3]
The coding regions of the V-antigens were amplified by polymerase chain reaction (PCR) with specific primers containing restriction enzyme sites for insertion into a protein expression vector
Yersinia LcrV has been recognized as a V-antigen with immunoprotective characteristics in Yersinia infections since the 1950s [4, 5, 7, 8]
Summary
The type III secretion system (TTSS) plays a major role in the virulence of many Gram-negative bacteria [1,2,3]. Through the TTSS, Gram-negative bacteria inject their effector molecules to target eukaryotic cells and induce a favorable environment for their infections. Translocation is a mechanism through which effector molecules of the TTSS pass through the targeted eukaryotic cell membrane. Three bacterial proteins form a translocational pore structure called the ‘translocon’ [1,2,3]. A cap protein in the secretion apparatus of the type III secretion needle is one type of translocon protein, which is called the V-antigen in Yersinia spp. for historical reasons [4,5,6,7,8].
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