Isolation of human antibodies against the central DNA binding domain of p53 from an individual with colorectal cancer using antibody phage display

Purpose: Serum anti-p53 antibodies are detected in ∼30% of patients with cancer, and most of these antibodies are directed against the NH- and COOH-terminal domains of p53. The aim of this study was to identify individuals with serum reactivity against the central and COOH-terminal domains of p53 and to isolate and characterize these recombinant human antibodies. Experimental Design: The serum of individuals with colorectal cancer was screened for the presence of anti-p53 antibodies. Antibody phage display libraries were constructed from four immunoreactive individuals, and the libraries were panned against the central and COOH-terminal domains of p53. Results: An antibody fragment (1159.8) that was specific for the whole molecule as well as the central domain was isolated from one of the libraries. The serum from the original individual inhibited the binding of this Fab fragment to p53, thus indicating that the antibody reflected the specificity of the in vivo immune response. The VL and VH genes from Fab 1159.8 matched germ-line genes from the VH3 and VK2 families, respectively. Competition analysis with monoclonal antibodies showed that Fab binding could be inhibited most effectively with DO11 and, to a lesser extent, Pab240, indicating an epitope within or adjacent to residues 181-190 of p53. Conclusions: The successful isolation of this human anticentral domain Fab provides additional insight into the nature and specificity of the tumor-specific immune response. This antibody could be used as a reagent for functional studies of p53, or it may be a candidate for use as an anticancer idiotypic vaccine

Generation of anti-p53 Fab fragments from individuals with colorectal cancer using phage display

Although many individuals with malignancy develop Abs against p53, little is currently known of the structural features, V gene usage, and degree of somatic mutation of these Abs. Such information is critical to any meaningful understanding of the nature and significance of this humoral immune response to p53. We have constructed phage display libraries from six individuals with colorectal cancer and a demonstrable serum immune response against p53. Following panning with recombinant p53, a total of 43 binding Fab were identified. Four of these Abs bound with high affinity to wild-type denatured p53 (1.19 x 10 - 1.57 x 10), as determined by BIAcore analysis, and were highly specific for both recombinant and cell line- derived p53, as determined by ELISA and immunoprecipitation. Epitope mapping showed they were reactive with the N terminus of human p53 between residues 27 and 44. Sequence analysis showed that the heavy chains were derived from the V(H)1 gene family, and the light chains from V(L)4. The pattern of replacement and silent mutations in the Fab sequence indicated that negative selection had occurred in the framework regions of all the V(H) genes. We show that lymphocytes from individuals with cancer represent a valuable source of high affinity human Abs against p53. This approach provides an opportunity to examine the genetic structure of these naturally occurring Abs, and to draw inferences regarding the nature of the immune response that produced them. Abs identified in this way have a number of potential therapeutic applications