Characterization of a virulence-modifying protein of Leptospira interrogans identified by shotgun phage display

Leptospiral adhesins: from identification to future perspectives

Leptospirosis is a significant zoonosis worldwide, with disease severity ranging from a mild non-specific illness to multi-organ dysfunction and hemorrhage. The disease is caused by pathogenic bacteria of the genus Leptospira, which are classified into pathogenic and saprophytic clades. Bacterial binding to host molecules and cells, coordinated by adhesin proteins, is an important step in pathogenesis. While many leptospiral adhesins have been identified, the vast majority have not been characterized in vivo. Herein, we present an overview of the current methodologies and successes in identifying adhesins in Leptospira, including known biological roles in vivo. We will also identify and discuss potential areas for future research.

Review of phage display: A jack-of-all-trades and master of most biomolecule display

Phage display was first described by George P. Smith when it was shown that virus particles were capable of presenting foreign proteins on their surface. The technology has paved the way for the evolution of various biomolecules presentation and diverse selection strategies. This unique feature has been applied as a versatile platform for numerous applications in drug discovery, protein engineering, diagnostics, and vaccine development. Over the decades, the limits of biomolecules displayed on phage particles have expanded from peptides to proteomes and even alternative scaffolds. This has allowed phage display to be viewed as a versatile display platform to accommodate various biomolecules ranging from small peptides to larger proteomes which has significantly impacted advancements in the biomedical industry. This review will explore the vast array of biomolecules that have been successfully employed in phage display technology in biomedical research.

Production and Purification of Cysteine-Rich Leptospiral Virulence-Modifying Proteins with or Without mCherry Fusion

Recombinant fluorescent fusion proteins are fundamental to advancing many aspects of protein science. Such proteins are typically used to enable the visualization of functional proteins in experimental systems, particularly cell biology. An important problem in biotechnology is the production of functional, soluble proteins. Here we report the use of mCherry-fusions of soluble, cysteine-rich, Leptospira-secreted exotoxins in the PF07598 gene family, the so-called virulence modifying (VM) proteins. The mCherry fusion proteins facilitated the visual detection of pink colonies of the VM proteins (LA3490 and LA1402) and following them through lysis and sequential chromatography steps. CD-spectroscopy analysis confirmed the stability and robustness of the mCherry-fusion protein, with a structure comparable to AlphaFold structural predictions. LA0591, a unique member of the PF07598 gene family that lacks N-terminal ricin B-like domains, was produced without mCherry tag that strengthens the recombinant protein production protocol without fusion protein as well. The current study provides the approaches for the synthesis of 50-125 kDa soluble, cysteine-rich, high-quality fast protein liquid chromatography (FPLC)-purified protein, with and without a mCherry tag. The use of mCherry-fusion proteins enables a streamlined, efficient process of protein production and qualitative and quantitative downstream analytical and functional studies. Approaches for troubleshooting and optimization were evaluated to overcome difficulties in recombinant protein expression and purification, demonstrating biotechnology utility in accelerating recombinant protein production.