Preparation and characterization of fusion proteins L19–IL-2 and D1.3–IL-2.

(A) Schematic representation of scFv L19–IL-2 and D1.3–IL-2 cDNA constructs. The scFv L19 or D1.3 and IL-2 cDNA were genetically fused by inserting a DNA linker (—) encoding for 15 amino acids (SSSSG)₃ and cloned into the pcDNA3 mammalian expression vector using the HindIII and BamHI restriction sites.16 The hatched box represents the CMV promoter sequence; the filled box, the genomic sequence of the signal secretion leader peptide ( is the intron inside the genomic sequence); and white boxes, the V_H or V_L of scFV L19 or D1.3 and IL-2 sequences. (B) Four percent to 18% SDS-PAGE gradient of scFv L19, L19–IL-2, and D1.3–IL-2 proteins after purification on ED-B/Sepharose affinity column. The values reported on the left indicate the molecular masses, in kilodaltons, of the standards. The fusion proteins L19–IL-2 and D1.3–IL-2 showed an apparent molecular mass of about 43 and 45 kd, respectively, in accordance with their expected sizes.