ABSTRACT
We have previously reported [1] that a murine mAb, designated 11-1F4, prepared against a human Vκ4 fibrils (LEN), reacted specifically with AL amyloid, regardless of the VL subgroup of the protein. In order to determine the molecular bases of this interaction, we have utilized a europium-linked immunoabsorbent assay (EuLISA) to measure the interaction of mAb 11-1F4 with light chain-related proteins. These studies show that this antibody does not recognize native κ and λ chains but, rather, binds with nanomolar affinity to proteins that have been partially denatured, i.e., when coated onto plastic wells used in the assay. EuLISA of peptides derived from proteolytic cleavage of the Vκ4 immunogen revealed that the cryptic epitope was located in a region encompassing the first 59 amino acids. Through epitope mapping of synthetic peptides, this site was placed more precisely within the first (N-terminal) 22 residues that comprise the first framework region (FRI) of Ig light chains, and especially involves those located between positions 1 and 4. Additionally, our finding that mAb11-1F4 inhibited at sub-equimolar concentrations de novo Vl fibrillogenesis suggests that interaction of this antibody with a partially unfolded amyloidogenic intermediate may act to stabilize the molecule and/or sterically inhibit fibril formation. The discovery that mAb 11-1F4 can prevent fibrillogenesis, as well as accelerate amyloidolysis, has provided new information on its immunoreactivity and therapeutic potential for patients with primary (AL) amyloidosis.
