CF-PA 2 Vtech: a cell-free human protein array technology for antibody validation against human proteins.

Antibodies are widely used for the detection of specific molecules such as peptides, proteins, and chemical compounds. The specificity of an antibody is therefore its most important feature. However, it is very difficult to confirm antibody specificity. Recently, we made a human protein array consisting of 19,712 kinds of recombinant human proteins produced by a wheat cell-free protein production system. Here, we demonstrate a novel protein array technology for antibody validation (CF-PA ² Vtech). Full-length human cDNAs were fused to N-terminal FLAG-GST and then synthesized by the wheat cell-free system. To construct a 20 K human protein array, about 10 to 14 kinds of human proteins were mixed and captured in each well by glutathione-conjugated magnetic beads in 12 plates or one plate with 384- or 1536-well format, respectively, using a strong magnetic device. Using this protein array plate, commercially available anti-HA or anti-PD-1 antibody reacted to 13 or three human proteins, respectively. The cross-reactivity of these proteins was also confirmed by immunoblotting. These proteins have a similar epitope, and alanine mutations of these epitope candidates dissolved the reactivity. These results indicated that CF-PA ² Vtech is very useful for validation of antibodies against human protein.