Novel CD43 specific phage antibodies react with early stage colorectal tumours.

Two panning strategies have been used to isolate phage antibody clones that recognise an intracellular epitope of CD43. Firstly, a naive scFv library was panned against a 15-mer CD43 synthetic peptide (RGGKRNGVVDAWAGP), and secondly the naive library was panned against native CD43, isolated from whole cell lysate of Colo205 cells, followed by selection with the synthetic CD43 peptide. Four phage antibodies (HapE8, F2, G9 and G11) were isolated and used in a preliminary immunohistochemistry study of CD43 expression on frozen colorectal adenoma and carcinoma tissue. The three antibodies HapE8, F2 and G11 showed a similar reactivity pattern, staining all adenomas and Dukes' A carcinomas, but only 2/4 Dukes' B and 1/9 Dukes' C. Antibody HapG9 similarly bound to 5/5 adenomas, but only 1/5 Dukes' A carcinoma and no tumours of a more advanced stage. No reactivity with normal colonic epithelium was observed but cross-reactivity with stromal lymphocytes was seen. These new anti-CD43 antibodies are likely to prove useful as screening tools in the detection of colorectal adenomas.