Proteomics of bacterial pathogenicity: therapeutic implications

Is the exoproteome important for bacterial pathogenesis? Lessons learned from interstrain exoprotein diversity in Listeria monocytogenes grown at different temperatures

Bacterial exoproteomes vary in composition and quantity among species and within each species, depending on the environmental conditions to which the cells are exposed. This article critically reviews the literature available on exoproteins synthesized by the foodborne pathogenic bacterium Listeria monocytogenes grown at different temperatures. The main challenges posed for exoproteome analyses and the strategies that are being used to overcome these constraints are discussed. Over thirty exoproteins from L. monocytogenes are considered, and the multifunctionality of some of them is discussed. Thus, at the host temperature of 37°C, good examples are provided by Lmo0443, a potential marker for low virulence, and by the virulence factors internalin C (InlC) and listeriolysin O (LLO). Based on the reported LLO-induced mucin exocytosis, a model is proposed for the involvement of extracellular LLO in optimizing the conditions for InlC intervention in the invasion of intestinal epithelial cells. At lower growth temperatures, exoproteins such as flagellin (FlaA) and oligopeptide permease (OppA) may explain the persistence of particular strains in the food industry environment, eventually allowing the development of new tools to eradicate L. monocytogenes, a major concern for public health.

Identifying potential therapeutic targets of methicillin-resistant Staphylococcus aureus through in vivo proteomic analysis

BACKGROUND

Detailed knowledge on protein repertoire of a pathogen during host infection is needed for both developing a better understanding of the pathogenesis and defining potential therapeutic targets. Such data, however, have been missing for Staphylococcus aureus, a major human pathogen.

METHODS

We determined the surface proteome of methicillin-resistant S. aureus (MRSA) clone usa300 derived directly from murine systemic infectiON.

RESULTS

The majority of the in vivo-expressed surface-associated proteins were lipoproteins involved in nutrient acquisition, especially uptake of metal ions. Enzyme-linked immunosorbent assay (ELISA) of convalescent human serum samples revealed that proteins that were highly produced during murine experimental infection were also produced during natural human infection. We found that among the 7 highly abundant lipoproteins only MntC, which is the manganese-binding protein of the MntABC system, was essential for MRSA virulence during murine systemic infection. Moreover, we show that MntA and MntB are equally important for MRSA virulence.

CONCLUSIONS

Besides providing experimental evidence that MntABC might be a potential therapeutic target for the development of antibiotics, our in vivo proteomics data will serve as a valuable basis for defining potential antigen combinations for multicomponent vaccines.

Surface proteome of "Mycobacterium avium subsp. hominissuis" during the early stages of macrophage infection

"Mycobacterium avium subsp. hominissuis" is a robust and pervasive environmental bacterium that can cause opportunistic infections in humans. The bacterium overcomes the host immune response and is capable of surviving and replicating within host macrophages. Little is known about the bacterial mechanisms that facilitate these processes, but it can be expected that surface-exposed proteins play an important role. In this study, the selective biotinylation of surface-exposed proteins, streptavidin affinity purification, and shotgun mass spectrometry were used to characterize the surface-exposed proteome of M. avium subsp. hominissuis. This analysis detected more than 100 proteins exposed at the bacterial surface of M. avium subsp. hominissuis. Comparisons of surface-exposed proteins between conditions simulating early infection identified several groups of proteins whose presence on the bacterial surface was either constitutive or appeared to be unique to specific culture conditions. This proteomic profile facilitates an improved understanding of M. avium subsp. hominissuis and how it establishes infection. Additionally, surface-exposed proteins are excellent targets for the host adaptive immune system, and their identification can inform the development of novel treatments, diagnostic tools, and vaccines for mycobacterial disease.