Peptides That Bind Specifically to an Antibody from a Chronic Lymphocytic Leukemia Clone Expressing Unmutated Immunoglobulin Variable Region Genes
Chronic lymphocytic leukemia (CLL) is a clonal disease of a subset of human B lymphocytes. Although the cause of the disease is unknown, its development and evolution appear to be promoted by signals delivered when B-cell receptors (BCRs) engage (auto)antigens. Here, using a peptide phage display library of enhanced size and diverse composition, we examined the binding specificity of a recombinant monoclonal antibody (mAb) constructed with the heavy chain and light chain variable domains of a CLL BCR that does not exhibit somatic mutations. As determined by testing the peptides identified in the selected peptide phage pool, this CLL-associated unmutated mAb bound a diverse set of sequences, some of which clustered in families based on amino acid sequence. Synthesis of these peptides and characterization of binding with the CLL-associated mAb revealed that mAb-peptide interactions were generally specific. Moreover, the mAb-peptide interactions were of lower affinities (micromolar KD), as measured by surface plasmon resonance, than those observed with a CLL mAb containing somatic mutations (nanomolar KD) and with immunoglobulin heavy chain variable (IGHV)-mutated antibodies selected by environmental antigens. This information may be of value in identifying and targeting B lymphocytes expressing specific BCRs in CLL patients and healthy subjects with monoclonal B lymphocytosis.
This work was supported in part by grants from the United States National Institutes of Health (CA81554 to N Chiorazzi and CA155472 to JR Lai), and by startup funds from the Albert Einstein College of Medicine (to JR Lai). The Karches Foundation, the Nash Family Foundation, the Marks Foundation, the Jerome Levy Foundation, the Leon Levy Foundation and the Mildred and Frank Feinberg Foundation also provided support (to KR Rai and N Chiorazzi). We thank Gregory Weiss (University of California — Irvine) for providing the pVIII library, Samantha Wilner for technical assistance with peptide purification and Huiyong Cheng for assistance with SPR experiments.
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