Figure 5
Comparison of specificities of anti-HER2/ECD antibodies from GH2 antibody library with those from immunized mouse.
(a) Competitions of the representative mouse S316 scFvs (marked by black dots next to the phylogenetic tree in Fig. 2) with the six mouse IgGs for binding to HER2/ECD are shown in the matrix. The competition strengths of the S316 scFvs against the mouse antibodies are color-coded in the matrix element cells: red-white-blue indicates decreasing level of competition between the two binders in the x- and y-axis. The x-axis of the completion matrix shows the 6 representative mouse antibodies, for which three epitope groups are evident (M32-M62, M41-M61 and M63-M64). The y-axis shows that the 90 representative S316 scFvs are clustered into the three corresponding epitope groups. 47/47(m3):0/20(m4):4/23(m6) accounts for the M32-M62 epitope group population; 0/47(m3):20/20(m4):16/23(m6) for M41-M61; 0/47(m3):0/20(m4):3/23(m6) for M63-M64. That is, m3 antibodies bound only to M32-M62 epitope group; m4 antibodies bound only to M41-M61 epitope group; m6 antibodies bound to all three epitope groups. (b) Competitions of the S90 scFvs from GH2 library with the six mouse IgGs for binding to HER2/ECD are shown in the matrix. The y-axis shows that the S90 scFvs are clustered into the three corresponding epitope groups, with three scFvs not belonging to any of the three major epitope groups. (c) EC50 of the 29 GH2 anti-HER2/ECD IgGs (Supplementary Table S4 and S5) are compared with those of 6 affinity-matured mouse anti-HER2/ECD IgGs and trastuzumab. Data for GH2 anti-HER2 IgGs are colored in black; 6 mouse anti-HER2 IgGs are in blue; trastuzumab is in red.
