Biosensing Extracellular Vesicle Subpopulations in Neurodegenerative Disease Conditions.

Extracellular vesicles (EVs) are secreted nanoparticles that are involved in intercellular communication and that modulate a wide range of biological processes in normal and disease conditions. However, EVs are highly heterogeneous in terms of origin in the cell, size, and density. As a result, complex protocols are required to identify and characterize specific EV subpopulations, limiting biomedical applications, notably in diagnostics. Here, we show that combining quartz crystal microbalance with dissipation (QCM-D) and nanoplasmonic sensing (NPS) provides a facile method to track the viscoelastic properties of small EVs. We applied this multisensing strategy to analyze small EVs isolated by differential ultracentrifugation from knock-in mouse striatal cells expressing either a mutated allele or wild-type allele of huntingtin (Htt), the Huntington's disease gene. Our results validate the sensing strategy coupling QCM-D and NPS and suggest that the mass and viscoelastic dissipation of EVs can serve as potent biomarkers for sensing the intercellular changes associated with the neurodegenerative condition.

Extracellular vesicles produced by human and animal Staphylococcus aureus strains share a highly conserved core proteome.

Staphylococcus aureus is an important opportunistic pathogen of humans and animals. It produces extracellular vesicles (EVs) that are involved in cellular communication and enable inter-kingdom crosstalk, the delivery of virulence factors and modulation of the host immune response. The protein content of EVs determines their biological functions. Clarifying which proteins are selected, and how, is of crucial value to understanding the role of EVs in pathogenesis and the development of molecular delivery systems. Here, we postulated that S. aureus EVs share a common proteome containing components involved in cargo sorting. The EV proteomes of five S. aureus strains originating from human, bovine, and ovine hosts were characterised. The clustering of EV proteomes reflected the diversity of the producing strains. A total of 253 proteins were identified, 119 of which composed a core EV proteome with functions in bacterial survival, pathogenesis, and putatively in EV biology. We also identified features in the sequences of EV proteins and the corresponding genes that could account for their packaging into EVs. Our findings corroborate the hypothesis of a selective sorting of proteins into EVs and offer new perspectives concerning the roles of EVs in S. aureus pathogenesis in specific host niches.

Author Correction: Exfoliative toxin E, a new Staphylococcus aureus virulence factor with host-specific activity.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Exfoliative toxin E, a new Staphylococcus aureus virulence factor with host-specific activity.

Exfoliative toxins (ETs) are secreted virulence factors produced by staphylococci. These serine proteases specifically cleave desmoglein 1 (Dsg1) in mammals and are key elements in staphylococcal skin infections. We recently identified a new et gene in S. aureus O46, a strain isolated from ovine mastitis. In the present study, we characterized the new et gene at a genetic level and the enzymatic activity of the deduced protein. The S. aureus O46 genome was re-assembled, annotated and compared with other publicly available S. aureus genomes. The deduced amino acid sequence of the new et gene shared 40%, 53% and 59% sequence identity to those of ETA, ETB and ETD, respectively. The new et gene shared the same genetic vicinity and was similar in other S. aureus strains bearing this gene. The recombinant enzyme of the new et gene caused skin exfoliation in vivo in neonatal mice. The new et-gene was thus named ete, encoding a new type (type E) of exfoliative toxin. We showed that ETE degraded the extracellular segments of Dsg1 in murine, ovine and caprine epidermis, as well as in ovine teat canal epithelia, but not that in bovine epidermis. We further showed that it directly hydrolyzed human and swine Dsg1 as well as murine Dsg1α and Dsg1ß, but not canine Dsg1 or murine Dsg1γ. Molecular modeling revealed a correlation between the preferred orientation of ETE docking on its Dsg1 cleavage site and species-specific cleavage activity, suggesting that the docking step preceding cleavage accounts for the ETE species-specificity. This new virulence factor may contribute to the bacterial colonization on the stratified epithelia in certain ruminants with mastitis.

Serological proteome analysis of Corynebacterium pseudotuberculosis isolated from different hosts reveals novel candidates for prophylactics to control caseous lymphadenitis.

Caseous lymphadenitis (CLA) is a highly prevalent disease in goats and sheep worldwide, which is caused by Corynebacterium pseudotuberculosis. Although several prophylactic methods against CLA have been proposed previously, the identification of new C. pseudotuberculosis proteins that are really produced during the infectious process is still needed to improve efficiency and accuracy in vaccines and diagnostics. In this study, we used optimized conditions for serological proteome analysis (SERPA) in order to identify new immune-reactive proteins in C. pseudotuberculosis culture supernatants of two strains, 1002 and C231, isolated from goats and sheep, respectively. Using a sheep and goat serum pool, 13 novel immune-reactive exoproteins common to the two strains were identified. Four of these proteins present known functions and were already described as immune-reactive proteins in other microorganisms, whereas the other nine are of unknown function and show low similarity with proteins from other bacterial species. These data reveal promising targets for immunoprophylactic methods against CLA.