Functional and structural characterization and immune response evaluation of a recombinant serine protease from Crotalus durissus collilineatus modified by PEGylation

Abstract

The snakes belonging to genus Crotalus are classified, phylogenetically, in the superfamily Colubroidea, family Viperidae and subfamily Crotalinae. This genus is comprised of approximately 29 species and, in South America, the specimens belong to Crotalus durissus species. The venom is composed mainly of crotoxin, possessing a neurotoxic action, and other toxins, such as metalloproteases, serine proteases, growth factors, among others. Snake Venom Serine Proteases (SVSPs) own the capability of affecting the prey's hemostatic system, due to the resemblance between these toxins and endogenous enzymes present in the blood coagulation, fibrinolytic and platelet aggregation pathways. In this way, they are considered promising therapeutic agents, as well as biotechnological tools. The expression of toxins in heterologous systems are an important step in the transition of one toxin to therapeutic agent, since it permits the obtainment of these proteins in large quantities, allowing their full characterization studies as well as their commercialization. On the other hand, it is well known the immunogenicity of exogenous proteins in diverse organisms, causing the destruction of the biopharmaceutical and, consequently, a drop in the therapeutic activity. The PEGylation, process in which a Polyethylene Glycol (PEG) is attached to proteins, aims to reduce the degradation process of these molecules in living organisms, as well as their innate immunogenicity. In this context, this project aims the purification of one SVSP from Crotalus durissus collilineatus venom, together with its heterologous expression and purification, followed by their PEGylation, using a PEG-derived molecule, m-PEG-Maleimide. Studies regarding the functional biochemical characterization and the determination of the specificity of enzymatic subsites will be employed as a way to elucidate the functional properties of these enzymes. The immune response triggered by the enzyme, in its recombinant and PEGylated-recombinant forms will be evaluated, in order to determine if the PEGylation process is capable of reducing in vivo immunogenicity. Additionally, in vitro studies concerning the activation of complement system by these enzymes will also be analyzed. Regarding the structural characterization, three-dimensional models will be proposed for the native and recombinant forms, as well as the determination of their glycosylation patterns. (AU)