Sicpin

Sicpin is an immunomodulatory salivary protein isolated from the blackfly *Simulium nigrimanum*. It acts as a complement inhibitor, targeting complement component 3 (C3) to block all three pathways of complement activation (classical, lectin, and alternative). By binding to C3, Sicpin induces a conformational change that prevents its interaction with C3 convertase, thereby inhibiting downstream complement protein deposition and complement-mediated lysis and inflammation. Additionally, Sicpin has been shown to bind to the CD4 receptor and reduce T and B cell proliferation. In preclinical animal models of acute lung injury and sepsis, Sicpin has demonstrated anti-inflammatory activity and enhanced survival, suggesting potential therapeutic utility in complement-mediated inflammatory disorders.