Production and evaluation of monospecific antibodies for a processing-independent sequence of human progastrin

We have produced a series of monospecific antibodies in five rabbits by immunization with a peptide corresponding to the preprogastrin sequence 76-88. Both antibody titres (0.2 to 3.0 x 10(6)), indexes of heterogeneity (approximately 1.0), and binding affinities (Koeff approximately 0.2 to 3.7 x 10(12) 1 x mol-1) were very high. The specificity for the N-terminus of the progastrin fragment was unique because even a conservative amino acid substitution five positions from the centre of binding diminished the binding by 90% for all antibodies. We conclude that these monospecific antibodies are well suited for development of a processing-independent analysis of progastrin and its products.