Preparation and identification of Fab fragment against IL-2 by genenic engineering technology / 解放军医学杂志

ABSTRACT

Objective To prepare human Fab fragment antibodies against Interleukin-2 and identify their antigenic specificity and combining activities with antigens. Methods The specific Anti-interleukin-2 clones were screened from a natural human Fab fragment antibodies phage display library against the immobilized interleukin-2 antigens. Then the phagemid DNA from the specific clones was digested with Spe I and Nhe I to delete gⅢ (about 660bp). The digested 4.7kb DNA, which was purified after separation of bands from agarose gel using purification kit, was ligated with T4-DNA ligase and the ligated reaction mixture were transformed to the BL21 (DE3) pLysS. Positive clones on the LB agar plates were inoculated to liquid LB culture medium, and when the bacteria were grown to OD600≈0.5 at 37℃ with continuous shaking, IPTG was added to induce the expression of soluble Fab fragment antibodies at 30℃. The expressed products containing Fab fragment antibodies were determined by SDS-PAGE, Western blot and ELISA. Results The soluble products were identified as containing human Fab fragment antibodies against Interleukin-2 by Western blot and formed a Mr 47?103 band under non-reducing condition on SDS-PAGE. The band was then proved as anti-human Fab fragment antibodies by Western blotting. ELISA demonstrated that Fab fragments possessed good antigenic specificity as well as excellent combining activity with interleukin-2 antigens, and the fragments did not react with bovine serum albumin and IL-4 in ELISA. Conclusions The soluble human anti-interleukin-2 Fab fragment antibodies have been highly expressed and successfully identified, and an effective way has been searched out for constructing the engineering antibodies. All of the results may lay a potentially good foundation for engineering human Fab antibodies, and for the clinical application of the antibodies on the immunotherapy of tumor diseases.