OBJECTIVETo construct a prokaryotic vector of ZCH-7-2F9 single chain antibody (ScFv2F9) and to obtain the ScFv2F9 protein with biological activity for further studies.

METHODSPrimers were synthesized according to the gene sequence of ScFv2F9, four tandem glycin and one serine (G4S) 3linker and multiple cloning site(MCS) of pIVEX2.3-MCS vector, which included NdeI and SmaI enzyme cleaving sites. ScFv2F9 gene was amplified through splicing by overlap extension (SOE) using the high fidelity Taq polymerase. Then the gene was cloned to pGEM-T easy and pIVEX2.3-MCS vectors. Positive recombinants (pIVEX2.3-MCS/ScFv2F9) were identified through enzyme cleaving and sequenced before expression. The recombinant plasmids were transfected into E.coli BL21star(DE3)plysS for expression. After purification with Ni+resin and renaturation in vitro, the relative molecular mass (Mr) and the binding activity of the interesting protein were determined by SDS-PAGE and flow cytometry (FCM), respectively.

RESULTThe cloned ScFv2F9 gene was identified to be functional by sequencing and expressing. The interesting protein was detected in inclusion body with a Mr of 31 000. The blocking test showed that the positive cell percentage, the mean fluorescence intensity (MFI) and the peak of channel (peak Ch) were reduced by 11.73%, 11.96% and 31.57%, respectively after once blockage by scFv2F9 protein, and 26.44 %, 21.75 % and 42.11 % after blockage twice.

CONCLUSIONThe ScFv2F9 against human CD14 antigen has been successfully expressed in prokaryotic cells with partial biological activity, which lays the foundation for further studies on its immunotoxin and other kinds of engineered antibodies.