Multimodal imaging of bacterial-host interface in mice and piglets with Staphylococcus aureus endocarditis

Abstract

Acute bacterial endocarditis is a rapid, difficult to manage, and frequently lethal disease. Potent antibiotics often cannot efficiently kill Staphylococcus aureus that colonizes the heart’s valves. S. aureus relies on virulence factors to evade therapeutics and the host’s immune response, usurping the host’s clotting system by activating circulating prothrombin with staphylocoagulase and von Willebrand factor–binding protein. An insoluble fibrin barrier then forms around the bacterial colony, shielding the pathogen from immune cell clearance. Targeting virulence factors may provide previously unidentified avenues to better diagnose and treat endocarditis. To tap into this unused therapeutic opportunity, we codeveloped therapeutics and multimodal molecular imaging to probe the host-pathogen interface. We introduced and validated a family of small-molecule optical and positron emission tomography (PET) reporters targeting active thrombin in the fibrin-rich environment of bacterial colonies. The imaging agents, based on the clinical thrombin inhibitor dabigatran, are bound to heart valve vegetations in mice. Using optical imaging, we monitored therapy with antibodies neutralizing staphylocoagulase and von Willebrand factor–binding protein in mice with S. aureus endocarditis. This treatment deactivated bacterial defenses against innate immune cells, decreased in vivo imaging signal, and improved survival. Aortic or tricuspid S. aureus endocarditis in piglets was also successfully imaged with clinical PET/magnetic resonance imaging. Our data map a route toward adjuvant immunotherapy for endocarditis and provide efficient tools to monitor this drug class for infectious diseases.

Staphylococcus aureus and Neutrophil Extracellular Traps: The Master Manipulator Meets Its Match in Immunothrombosis

“…In particular, CD11b-positive cells accumulate outside the bacteria-rich environment. 86 In the presence of such a physical barrier, neutrophils and their released NETs may not be able to reach their target and carry out their bactericidal function. Additionally, DNase treatment in rats with endocarditis lesions reduced the size of the vegetation and the number of colonizing bacteria.…”

“…Finally, monoclonal antibodies against Coa and VWbp, which reduce the amount of fibrin surrounding the bacteria-rich environment and make bacteria more accessible to neutrophils, improved survival in mice with endocarditis. 86 Treatment with these antibodies also allowed neutrophils to better interact with S. aureus in a femoral artery vegetation model. 86 …”

“… 86 Treatment with these antibodies also allowed neutrophils to better interact with S. aureus in a femoral artery vegetation model. 86 …”

Native valve, prosthetic valve, and cardiac device-related infective endocarditis: A review and update on current innovative diagnostic and therapeutic strategies

“…(E) LA-ICP-MS imaging makes it possible to produce a quantitative distribution map (min to max, blue to red) of elemental distribution (Ca, Mg, Mn, Fe, Cu, or Zn) within female C57BL/6 mice heart tissue infected by bacteria ( Schwarz et al, 2022 ). (F) Visualization of myeloid cells’ (green) inability to interact with bacteria (white) due to a fibrin barrier (red) in endocarditis in mice ( Panizzi et al, 2020 ). (G) Visualization of S. epidermidis on aortic valve tissue with bacteria after incubation with a FISH probe (yellow) and DAPI (blue) ( Lauten et al, 2021 ).…”

“…Dabigatran, a thrombin inhibitor, has been extensively studied in preclinical IE in vivo studies with promising results ( Lerche et al, 2021 ). Panizzi et al was able to develop a targeted imaging agent based on this thrombin inhibitor ( Panizzi et al, 2020 ). The radioisotope fluorine-18 was coupled to dabigatran to produce a PET imaging agent, or a fluorochrome was attached to synthesize a near-infrared imaging agent for intravital microscopy.…”