Wj. Ball et al., Selection of peptidic mimics of digoxin from phage-displayed peptide libraries by anti-digoxin antibodies, J MOL BIOL, 301(1), 2000, pp. 101-115
Since the initial report of the development of methodology to generate high
-affinity digitalis-specific (digoxin) antibodies, these antibodies have pr
oven extremely useful tools to monitor digoxin levels in digitalized patien
ts and, as Fab fragments, to reverse toxic digoxin effects in life-threaten
ing digoxin overdoses. These antibodies (both digoxin-specific and ouabain-
specific) have been used extensively by investigators for the identificatio
n and characterization of putative endogenous digitalis-like factors. In th
is study, we used two well-characterized mouse anti-digoxin monoclonal anti
bodies (mAbs), designated 26-10 and 45-20, as binding templates with which
to select short bacteriophage-displayed (pIII protein inserted) peptides th
at are capable of binding to these mAbs and mimicking the conformational st
ructure of digoxin. Selective enrichment from two phage-displayed random pe
ptide Libraries enabled us to isolate and identify distinct 15 and 26 amino
acid residue peptide inserts that bind with high avidity and idiotypic spe
cificity to the selecting mAbs. Among these displayed inserts a subset was
identified whose mAb binding is inhibited by digoxin and whose correspondin
g synthetic peptides inhibit phage binding. They, therefore, appear to bind
at the mAbs digoxin-binding sites. These data provide the first clear evid
ence that short polypeptides can serve as surrogates for the low molecular
mass hapten digoxin. (C) 2000 Academic Press.