A combination of comparative proteomics and serological proteome analysis to screen for in vivo gene expression of B. pertussis

PEREZ VIDAKOVICS, ML; PABA, J; LAMBERTI YA; RICART CA; DE SOUSA MV; RODRIGUEZ ME

Pilar. Argentina

Congreso; 1st Annual Iberoamerican Proteomics Congress; 2007

To succeed in host colonization bacterial pathogens have to obtain nutrients which are essential for their growth. Iron is usually one of such essential factors, and the main nutritional stress under physiological condition. The ability to scavenge iron is an important virulence trait. Regulation of gene expression in response to local iron concentration is commonly observed in bacterial pathogens. In previous studies we found B. pertussis response to iron limitation to encompass an increase in virulence and immunogenicity. In this study, we used a combination of comparative proteomic and serological proteome analysis to screen for gene expression under iron starvation and selection of new in vivo immunogens, as valuable vaccine candidates.  Whole cell lysates (WCL) and outer membrane fractions (OMF) of bacteria grown either under iron-starvation or iron-excess conditions were analyzed by two-dimensional gel electrophoresis (pH 4-7 and pH 6-11 SDS-PAGE 10%). The resulting average protein maps of WCL and OMF contained 900 (pH 4-7)/ 200 (pH 6-11) and 240 (pH 4-7)/ 300 (pH 6-11) spots, respectively. Statistical analysis of spot volume in paired spots revealed 36 proteins displaying differential expression, 9 with higher expression under iron-excess and 27 with increased expression under iron-starvation. These proteins were subjected to tryptic digestion and MALDI-TOF-MS. Apart from those previously reported we identified new low-iron induced proteins that might help to explain the increased virulence of this phenotype. Additionally, at least four of the differentially expressed proteins proved to specifically react with sera from infected individuals. Further studies are being conducted to gain a better insight into their role in bacterial pathogenesis and to evaluate the cellular and humoral response to differentially expressed proteins with potential as vaccine components.