Comparative proteome analysis of cellular proteins extracted from highly virulent Francisella tularensis ssp. tularensis and less virulent F. tularensis ssp. holarctica and F. tularensis ssp. mediaasiatica

Abstract

Francisella tularensis is the causative agent of the zoonotic disease tularemia. Four subspecies of this pathogen, namely ssp. tularensis, mediaasiatica, holarctica, and novicida are spread throughout the northern hemisphere. Although there are marked variations in their virulence to mammals, the subspecies are difficult to identify as they are closely genetically related. We carried out the comparative proteome analysis of cellular extracts from isolates representing the highly virulent subspecies tularensis, and the less virulent subspecies mediaasiatica and holarctica in order to identify new diagnostic markers and putative factors of virulence. We identified 27 protein spots that were either specifically present or at significantly higher abundance in ssp. tularensis strains, 22 proteins in ssp. mediaasiatica strains, and 26 proteins in ssp. holarctica strains. Subspecies tularensis-specific proteins might represent putative virulence factors. Of 27 identified tularensis-specific spots 17 represented charge and mass variants of proteins occurring in other subspecies, 7 spots were found to be present at higher abundance, and 3 spots were specifically present in tularensis strains. Amongst them, PilP protein, as a component necessary for the biogenesis of the type IV pilus, virulence and adhesion factor for many human pathogen, was identified. Furthermore, the identification of additional 27 proteins common for ssp. tularensis and mediaasiatica, and 19 proteins shared by ssp. mediaasiatica and holarctica documented apparent closer genetic similarity between ssp. tularensis and mediaasiatica.

Comparative proteomic study of Edwardsiella tarda strains with different degrees of virulence

“…A nonsynonymous variant can alter protein structure or function, however these changes can be profitable or even neutral if the changes do not affect the protein folding or the active site. Previous works associating this different electrophoretic mobility with the pathogenic potential, demonstrated that the proteins showing shifts from more acidic position are in less virulent strains [32,33]. In the present study, the electrophoretic changes did not follow a fixed pattern; the enzymes related to the virulent strain sometimes were more basic and other times more acidic.…”

Modulation of virulence factors in Francisella tularensis determines human macrophage responses

“…Previous Francisella proteomics studies have catalogued LVS protein profiles [29,30], immune reactive proteins [31], or stress response proteins [32]. A proteomic comparison of three Francisella strains has been performed, identifying many protein differences [33]. However, most of these were mass and charge variants of proteins present in all three strains [33].…”

Current and emerging assays for Francisella tularensis detection: a review

“…The protein can then be identified by means of mass spectrometry. Such an approach was used for comparison between the three subspecies of F. tularensis and there were several protein spots characteristic of each subspecies (Hubalek et al, 2004). In combination with statistical methods such as principal component analysis, this method can be used for the identification of subspecies.…”

“…The advantage of well-characterized protein spots on the gel led to the investigation of immunogenicity of Francisella proteins in the host (Hubalek et al 2004). The resulting list of proteins points out to potential targets of immunoassays or subunit vaccines.…”