Abstract
<title>Abstract</title> <p> Canine leishmaniasis (CanL), caused by <italic>Leishmania infantum</italic> , is a chronic zoonotic disease characterized by a strong humoral immune response that is typically associated with an inability to control infection, leading to progression to severe symptomatic disease. The exacerbated response leads to overproduction of antibodies, which often occurs in the presence of high antigen load, leading to the formation of circulating immune complexes (CIC). These CIC are central to the immunopathogenesis of CanL, as their deposition in tissues contributes to vasculitis, uveitis, dermatitis, glomerulonephritis, and renal failure. Quantification of CIC by a specific ELISA has shown that dogs with advanced clinical signs exhibit significantly higher CIC concentrations in their serum than asymptomatic or early-stage cases. Recent studies have demonstrated a positive correlation between CIC levels and disease severity, suggesting their potential as biomarkers for diagnosis, staging, and monitoring treatment responses in the management of CanL. Beyond their levels, the protein composition of CIC may also reflect the stage of the disease. Therefore, the aim of this study was to characterize the protein composition of CIC and evaluate its association with disease severity. The results have demonstrated that CIC composition varies according to disease stage in dogs with CanL, reflecting the immune status of the host. </p>