RADIOMETAL LABELING OF RECOMBINANT PROTEINS BY A GENETICALLY-ENGINEERED MINIMAL CHELATION SITE - TC-99M COORDINATION BY SINGLE-CHAIN FV ANTIBODY FUSION PROTEINS THROUGH A C-TERMINAL CYSTEINYL PEPTIDE
Ajt. George et al., RADIOMETAL LABELING OF RECOMBINANT PROTEINS BY A GENETICALLY-ENGINEERED MINIMAL CHELATION SITE - TC-99M COORDINATION BY SINGLE-CHAIN FV ANTIBODY FUSION PROTEINS THROUGH A C-TERMINAL CYSTEINYL PEPTIDE, Proceedings of the National Academy of Sciences of the United Statesof America, 92(18), 1995, pp. 8358-8362
We describe a method to facilitate radioimaging with technetium-99m (T
c-99m) by genetic incorporation of a Tc-99m chelation site in recombin
ant single-chain Fv (sFv) antibody proteins, This method relies on fus
ion of the sFv C terminus with a Gly(4)Cys peptide that specifically c
oordinates Tc-99m, By using analogues of the 26-10 anti-digoxin sFv as
our primary model, we find that addition of the chelate peptide, to f
orm 26-10-1 sFv', does not alter the antigen-binding affinity of sFv,
We have demonstrated nearly quantitative chelation of 0.5-50 mCi of Tc
-99m per mg of 26-10-1 sFv' (1 Ci = 37 GBq), These Tc-99m-labeled sFv'
complexes are highly stable to challenge with saline buffers, plasma,
or diethylenetriaminepentaacetic acid. We find that the Tc-99m-labele
d 741F8-1 sFv', specific for the c-erbB-2 tumor-associated antigen, is
effective in imaging human ovarian carcinoma in a scid mouse tumor xe
nograft model. This fusion chelate methodology should be applicable to
diagnostic imaging with (TC)-T-99m and radioimmunotherapy with Re-186
or Re-188, and its use could extend beyond the sFv' to other engineer
ed antibodies, recombinant proteins, and synthetic peptides.