E. Rene Rodriguez

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Infective endocarditis is a life-threatening infection of heart valves and adjacent structures characterized by vegetations on valves and other endocardial surfaces, with tissue destruction and risk of embolization. We used high-resolution mass spectrometry to define the proteome of staphylococcal and non-staphylococcal vegetations and Terminal Amine Isotopic Labeling of Substrates (TAILS) to define their proteolytic landscapes. These approaches identified over 2000 human proteins in staphylococcal and non-staphylococcal vegetations. Individual vegetation proteomes demonstrated comparable profiles of quantitatively major constituents that overlapped with serum, platelet, and neutrophil proteomes. Staphylococcal vegetation proteomes resembled one another more than the proteomes of non-staphylococcal vegetations. TAILS demonstrated extensive proteolysis within vegetations, with numerous previously undescribed cleavages. Several proteases and pathogen-specific proteins, including virulence factors, were identified in most vegetations. Proteolytic peptides in fibronectin and complement C3 were identified as potential infective endocarditis biomarkers. Overlap of staphylococcal and non-staphylococcal vegetation proteomes suggests a convergent thrombotic and immune response to endocardial infection by diverse pathogens. However, the differences between staphylococcal and non-staphylococcal vegetations and internal variance within the non-staphylococcal group indicate that additional pathogen- or patient-specific effects exist. Pervasive proteolysis of vegetation components may arise from vegetation-intrinsic proteases and destabilize vegetations, contributing to embolism.

Large vessel vasculitis (LVV) covers a spectrum of primary vasculitides predominantly affecting the aorta and its major branches. The two main subtypes are giant cell arteritis (GCA) and Takayasu arteritis (TA). Less commonly LVV occurs in various other diseases. Clinical manifestations result from vascular stenosis, occlusion, and dilation, sometimes complicated by aneurysm rupture or dissection. Occasionally LVV is discovered unexpectedly on pathological examination of a resected aortic aneurysm. Clinical evaluation is often unreliable in determining disease activity. Moreover, the diagnostic tools are imperfect. Acute phase reactants can be normal at presentation and available imaging modalities are more reliable in delineating vascular anatomy than in providing reliable information on degree of vascular inflammation. Glucocorticoids are the mainstay of therapy of LVV. Patients may develop predictable adverse effects from long-term glucocorticoid use. Several steroid-sparing agents have also shown some promise and are currently in use. Endovascular revascularization procedures and open surgical treatment for aneurysms and dissections are sometimes necessary, but results are not always favorable and relapses are common. This article, the first in a series of two, will be devoted to GCA and isolated (idiopathic) aortitis, while TA will be covered in detail in the next article.