site-specific pegylation of recombinant immunotoxin dab389il-2: structural and functional assessment

Background: dab389il2 is considered a fusion immunotoxin and it is used for the ctcl therapy. dab389il2 includes of two distinct portions; the catalytic domain of diphtheria toxin and il2. dab389il2 duo to the presence of a free cysteine residue (cys 513 in il2 part) is prone to unwanted intramolecular and intermolecular disulfide bonds formation and aggregation problems. aggregation is considered as the most common physical instability. pegylation is an effective approach to increase the stability and halflife of therapeutic proteins.materials and methods: in this study, the pegylation of recombinant dab389il2 was performed by mpegvinylsulfone, through partial denaturation condition at 4 0c for 24 h. to confirm the pegylation reaction, sdspage and dynamic light scattering (dls) was used. the structure of dab389il2 and pegylated immunotoxin dab389il2 was analyzed using the circular dichroism (cd) and fluorescence methods. also, k562 cells line were treated with various concentrations of dab389il2 and conjugated form. in the following, the nuclease activity of dab389il2 and pegylated form was determined. results: the sdspage result confirmed the sitespecific pegylation of dab389il2. spectroscopy results exhibited that the pegylation doesn rsquo;t affect the protein native structure. also, cytotoxicity assay and nuclease activity test confirmed that pegylated protein induces death in k562 cells line and dna degradation respectively. conclusion: it is concluded that the pegylated immunotoxin dab389il2 has a proper structure and function; thus, pegylated immunotoxin requires more survey due its unique properties.