Staphylococcus aureus is a widespread, persistent human pathogen that has a long-standing and increasingly negative impact on human health. It is a leading cause of nosocomial and community-acquired infections, including several potentially fatal conditions of the circulatory system such as endocarditis and septicemia, as well as infections associated with implanted medical devices, such as intravascular catheters, pacemakers, and delivery pumps. Recent studies have demonstrated that S. aureus expresses several proteins that inhibit the innate and adaptive components of the human immune system and a body of evidence suggests that these proteins are critical to the success of S. aureus as a pathogen. While proper function of the complement system is essential for an efficient immune response against S. aureus, this organism has achieved several powerful and sophisticated mechanisms to attenuate complement function. Together with a newly identified homolog denoted Ehp, the Extracellular Fibrinogen-binding Protein (Efb) defines a novel family of complement inhibitory proteins that disrupt downstream functions of innate immunity by forming a potent complex with the native, unprocessed form of human complement component 3 (C3). However, a detailed understanding of the structure and mechanism of function for these proteins in the immunosuppressive repertoire of this ever more dangerous pathogen is lacking. To address this need during the requested funding period, we propose the following Specific Aims: 1. To Study the Structure/ Function Relationships of the Efb/C3 Complex 2. To Characterize the Structure, Dynamics, and Functions of the Ehp/C3 Complex 3. To Investigate the Structural Basis and Associated functions of Efb and Ehp-mediated Enhancement of Factor H Binding to C3 4. To Investigate the Molecular Basis and Functions of Efb Binding to Fibrinogen By studying the structure and function of these proteins, we will further our understanding of the mechanisms used by S. aureus to evade the immune system. In turn, this will promote our knowledge of the structure and mechanism of C3 recognition and inhibition during pathological situations. In the long term, these studies will provide important insights into the clinical promise for (a) antibacterial preventative measures that are designed to block the functions of immunosuppressive virulence factors from S. aureus, and (b) molecules which mimic their activities by blocking pathological overactivation of the complement system, as is seen in autoimmune and bioincompatibility disorders. Project Narrative: Structure/Function Analysis of Staphylococcal Complement Inhibitors Staphylococcus aureus is a widespread, persistent human pathogen that expresses several proteins that inhibit components of the human immune system. Among these, the Efb-family of secreted proteins has been shown to disrupt downstream function of complement response by binding and inactivating complement component C3. In this work, we propose to study the structure and function of these proteins and their complexes with C3. The results attained will further our understanding of the structure and mechanism of C3 recognition and inhibition of C3 during pathological situations. In addition, study of these S. aureus proteins should provide important insights into the clinical promise for therapeutics that either disrupt or mimic their function.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
Project #
Application #
Study Section
Innate Immunity and Inflammation Study Section (III)
Program Officer
Huntley, Clayton C
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Missouri Kansas City
Anatomy/Cell Biology
Schools of Arts and Sciences
Kansas City
United States
Zip Code
Stapels, Daphne A C; Woehl, Jordan L; Milder, Fin J et al. (2018) Evidence for multiple modes of neutrophil serine protease recognition by the EAP family of Staphylococcal innate immune evasion proteins. Protein Sci 27:509-522
Georgoutsou-Spyridonos, Maria; Ricklin, Daniel; Pratsinis, Haris et al. (2015) Attenuation of Staphylococcus aureus-Induced Bacteremia by Human Mini-Antibodies Targeting the Complement Inhibitory Protein Efb. J Immunol 195:3946-58
Stapels, Daphne A C; Geisbrecht, Brian V; Rooijakkers, Suzan H M (2015) Neutrophil serine proteases in antibacterial defense. Curr Opin Microbiol 23:42-8
Skaff, D Andrew; McWhorter, William J; Geisbrecht, Brian V et al. (2015) Inhibition of bacterial mevalonate diphosphate decarboxylase by eriochrome compounds. Arch Biochem Biophys 566:1-6
Summers, Brady J; Garcia, Brandon L; Woehl, Jordan L et al. (2015) Identification of peptidic inhibitors of the alternative complement pathway based on Staphylococcus aureus SCIN proteins. Mol Immunol 67:193-205
Stapels, Daphne A C; Ramyar, Kasra X; Bischoff, Markus et al. (2014) Staphylococcus aureus secretes a unique class of neutrophil serine protease inhibitors. Proc Natl Acad Sci U S A 111:13187-92
Woehl, Jordan L; Stapels, Daphne A C; Garcia, Brandon L et al. (2014) The extracellular adherence protein from Staphylococcus aureus inhibits the classical and lectin pathways of complement by blocking formation of the C3 proconvertase. J Immunol 193:6161-6171
Ricklin, Daniel; Lambris, John D (2013) Progress and trends in complement therapeutics. Adv Exp Med Biol 735:1-22
Yang, Kun; Deangelis, Robert A; Reed, Janet E et al. (2013) Complement in Action: An Analysis of Patent Trends from 1976 Through 2011. Adv Exp Med Biol 735:301-313
Ricklin, Daniel; Lambris, John D (2013) Progress and Trends in Complement Therapeutics. Adv Exp Med Biol 735:1-22

Showing the most recent 10 out of 31 publications