Chronic lymphocytic leukemia monitoring with a Lamprey idiotope-specific antibody.

For antigen recognition, lampreys use leucine-rich repeats (LRR) instead of immunoglobulin V-(D)-J domains to generate variable lymphocyte receptors (VLR) of three types, VLRA, VLRB, and VLRC. VLRB-bearing lymphocytes respond to immunization with proliferation and differentiation into plasmacytes that secrete multivalent VLRB antibodies. Here we immunized lampreys with B cells from patients with chronic lymphocytic leukemia (CLL) to generate recombinant monoclonal VLRB antibodies, one of which, VLR39, was specific for the donor CLL cells. The target epitope of VLR39 was shown to be the complementarity determining region 3 (CDR3) of the heavy chain variable region (VH) of the B cell receptor. Using this antibody to monitor the CLL donor after chemo-immunotherapy-induced remission, we detected VLR39(+) B cells in the patient 51 months later, before significant increase in lymphocyte count or CD5(+) B cells. This indication of reemergence of the leukemic clone was verified by VH sequencing. Lamprey antibodies can exhibit exquisite specificity for a protein epitope, a CLL signature VH CDR3 sequence in this case, and offer a rapid strategy for generating anti-idiotype antibodies for early detection of leukemia recurrence.