Mixed cryoglobulinemia (MC) is a systemic leukocytoclastic vasculitis involving small and medium-sized vessels and characterized by the deposition of cold-precipitable IgG-IgM immune complexes, called cryoglobulins. The main cause of MC is chronic hepatitis C virus (HCV) infection, representing 70-90% MC. Of note, conversely, the presence of circulating cryoglobulins is identified in about 50% of HCV-infected patients, although only 5-10% of them have a symptomatic cryoglobulinemic vasculitis. The contribution of endothelial damage and/or coagulation dysfunction to the clinical manifestations of MC, either HCV-associated or essential, has been poorly investigated so far. Our project aims to analyze the possible influence of haemostatic dysfunction in vasculitis development and to find biomarkers able to predict those patients with HCV-associated MC and circulating cryoglobulins at risk for vasculitis development.
In vivo platelet activation (through the measurement of sCD40L and sP-selectin) and markers of endothelial activation, namely PAI-1 and vWF, have been found to be elevated in patients with HCV infection but a possible influence of cryoglobulins in the endothelial damage has not been investigated. Because of the strict correlation of the coagulation cascade and the inflammatory network we will analyze markers of coagulation activation in vivo and bio-humoral markers of inflammation as TNF-alpha and IL-6, C-reactive protein and VCAM-1. This latter molecule has been already found increased in severe forms of HCV-associated MC but never investigated in essential MC.
The results of our project may provide simple and measurable factors that indicate endothelial and/or coagulation system dysfunction possibly able to stratify HCV-infected patients at risk for vasculits and able to shed light in the pathogenesis of leukocytoclastic vasculitis in MC, defining disease-specific haemostatic characteristics in essential or HCV-associated MC.
The pathogenic event triggering leukocytoclastic vasculitis in MC is the binding of cryoprecipitable immune complexes (IC), containing IgM molecules directed against Fc determinants of IgG with anti- HCV reactivity, to the endothelial cell membrane via the C1q receptor (C1q-R). The binding of immune complexes to C1qR globular domain on the surface of endothelial cells generates vasoactive peptides from the complement system and favors the recruitment of inflammatory cells (i.e., neutrophils), which mediate a leukocytoclastic vasculitis (N Engl J Med. 2013 Sep 12;369(11):1035-45).
This process appears only in some patients infected with HCV and with cryoglobulins in their serum and the reason(s) are still obscure. Moreover, in some patients mixed cryoglobulinaemia has an acute onset and presents with multisystem polyarteritis nodosa-like necrotizing vasculitis with prominent cutaneous, neurological and renal involvement.
It would be therefore very important to have the possibility to predict which patients will develop a cryoglobulinemiac-related vasculits and among these who may present with a severe form.
The results of our project may provide simple and measurable factors that indicate endothelial and/or coagulation system dysfunction possibly able to stratify patients at risk.
Moreover, it is possible that pathogenic mechanisms responsible for vasculitis development, to date still obscure, will be elucidated through our findings.
Most of the factors that will be investigated, as in vivo platelet activation markers such as sCD40L and sP-selectin, markers of endothelial activation and markers of coagulation activation in vivo, have been analyzed in HCV patients but the search for cryoglobulins in these patients and their possible influence has never been investigated. Therefore, our project will add new information on the role of endothelial and coagulation dysfunction in the patient with HCV infection. Moreover, the analysis of the same factors in the patient with essential mixed cryoglobulinemia will contribute to define common and disease-specific pathogenetic mechanisms between HCV-associated and essential MC.
Finally, the analysis of these factors in patients with HCV-associated MC vasculitis before and after successful antiviral therapy will contribute to identify the role of HCV infection in vascular damage by evaluating its possible reversion after virus eradication. The innovation of our project relies in the application of simple and repeatable analyses in different categories of patients with similar phenotype (e.g. leukocitoclastic vasculitis) to allow stratification of patients at risk and to possibly untangle involved pathogenic mechanisms.