A rapid method for selecting suitable animal species for studying pathogen interactions with plasma protein ligands invivo.

Clément Naudin,Ariane Schumski,Outi M H Salo‐Ahen,Emanuel Smeds,Heiko Herwald

doi:10.1111/1751-7915.12601

Clément Naudin, Ariane Schumski + Show 3 more

Open Access

https://doi.org/10.1111/1751-7915.12601

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Abstract

SummarySpecies tropism constitutes a serious problem for developing relevant animal models of infection. Human pathogens can express virulence factors that show specific selectivity to human proteins, while their affinity for orthologs from other species can vary significantly. Suitable animal species must be used to analyse whether virulence factors are potential targets for drug development. We developed an assay that rapidly predicts applicable animal species for studying virulence factors binding plasma proteins. We used two well‐characterized Staphylococcus aureus proteins, SSL7 and Efb, to develop an ELISA‐based inhibition assay using plasma from different animal species. The interaction between SSL7 and human C5 and the binding of Efb to human fibrinogen and human C3 was studied. Affinity experiments and Western blot analyses were used to validate the assay. Human, monkey and cat plasma interfered with binding of SSL7 to human C5. Binding of Efb to human fibrinogen was blocked in human, monkey, gerbil and pig plasma, while human, monkey, gerbil, rabbit, cat and guinea pig plasma inhibited the binding of Efb to human C3. These results emphasize the importance of choosing correct animal models, and thus, our approach is a rapid and cost‐effective method that can be used to prevent unnecessary animal experiments.

Highlights

The total number of proteins in blood plasma is not known, but a fairly recent study using mass spectrometric analyses suggests that human plasma contains around 2000 different proteins (Farrah et al, 2011)
Bacterial pathogens such as Staphylococcus aureus (S. aureus) have different cell wall-anchored or secreted proteins that bind to various human plasma proteins, such as fibrinogen (Fg), complement and antibodies (Serruto et al, 2010; Sidorin and Solov’eva, 2011)
The selectivity is highly variable and sometimes the binding appears to be human specific, such as the interaction of S. aureus bone sialoprotein binding protein (Bbp) with human fibrinogen, which is highly specific as Fg from other species tested is not bound by Bbp (Vazquez et al, 2011)

Summary

Species tropism constitutes a serious problem for developing relevant animal models of infection. Human pathogens can express virulence factors that show specific selectivity to human proteins, while their affinity for orthologs from other species can vary significantly. Suitable animal species must be used to analyse whether virulence factors are potential targets for drug development. We developed an assay that rapidly predicts applicable animal species for studying virulence factors binding plasma proteins. We used two well-characterized Staphylococcus aureus proteins, SSL7 and Efb, to develop an ELISA-based inhibition assay using plasma from different animal species. The interaction between SSL7 and human C5 and the binding of Efb to human fibrinogen and human C3 was studied. Affinity experiments and Western blot analyses were used to validate the assay. Monkey and cat plasma interfered with binding of SSL7 to human C5

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