Structure and specificity of lamprey monoclonal antibodies

Abstract

Adaptive immunity in jawless vertebrates (lamprey and hagfish) is mediated by lymphocytes that undergo combinatorial assembly of leucine-rich repeat (LRR) gene segments to create a diverse repertoire of variable lymphocyte receptor (VLR) genes. Immunization with particulate antigens induces VLR-B-bearing lymphocytes to secrete antigen-specific VLR-B antibodies. Here, we describe the production of recombinant VLR-B antibodies specific for BclA, a major coat protein of Bacillus anthracis spores. The recombinant VLR-B antibodies possess 8 -10 uniform subunits that collectively bind antigen with high avidity. Sequence analysis, mutagenesis, and modeling studies show that antigen binding involves residues in the ␤-sheets lining the VLR-B concave surface. EM visualization reveals tetrameric and pentameric molecules having a central core and highly flexible pairs of stalk-region ''arms'' with antigenbinding ''hands.'' Remarkable antigen-binding specificity, avidity, and stability predict that these unusual LRR-based monoclonal antibodies will find many biomedical uses.antigen-binding site ͉ leucine-rich repeat ͉ variable lymphocyte receptor

A structural basis for antigen recognition by the T cell-like lymphocytes of sea lamprey

“…It also is noteworthy that HEL-specific VLRBs, derived from the same immunized lamprey as VLRA.R2.1, bound HEL with micromolar K D s (15). However, VLRBs, like IgM antibodies, overcome their low monomeric affinities for antigen by forming high-avidity multimers in plasma (5,11). Such a compensatory mechanism may not exist for VLRAs, whose oligomerization state on the lymphocyte surface is unknown; the absence of a compensatory mechanism might explain their high monomeric affinities, at least for soluble antigens.…”

“…Thus, VLRB lymphocytes respond to antigenic stimulation by proliferating and differentiating into plasmacytes that secrete VLRBs specific for native antigens. Like IgM antibodies, VLRBs overcome their weak monomeric affinities (micromolar K D s) by forming high-avidity multimers (5,11). By contrast, VLRA lymphocytes do not secrete their receptors following antigen activation.…”

High-affinity lamprey VLRA and VLRB monoclonal antibodies

“…Both plasma VLRB and the recombinant antianthrax antibodies formed multimers, comprising 4 or 5 disulfide-linked dimeric subunits, which avidly bound BclA. But monomeric forms of the antianthrax VLRB were weak BclA binders, indicating that high-avidity binding requires oligomerization (11). In another study, lamprey immunized to human blood group O erythrocytes produced anti-H-trisaccharide plasma VLRB, and the crystal structure of this complex was reported (12).…”

“…Within 4-8 weeks after i.p. injection of Bacillus anthracis spores, the lamprey plasma contained VLRB antibodies that reacted specifically with the spores and with their BclA glycoprotein component (5,11). Recombinant VLRBs from anthrax-immunized larvae were cloned and expressed in a mammalian cell line.…”

The Application of Prophylactic Antibodies for Rhinovirus Infections

“…These include aggregation of virions, destabilization/stabilization of virion structure, inhibition of attachment and entry of the virus into target cells by mucosal IgA or receptor blocking IgG, and binding to nascent virions to block their release from the cell surface [43]. By combining modern antibody selection techniques (phage display, B-cell immortalization and single B-cell cloning), alternative Ab scaffolds such as single chain Abs (scFv) or lamprey [44] and camelid Abs [45] with new functional assay formats it may be possible to identify antibodies that target one or more aspects of the RV life cycle. However, due to sequence heterogeneity of RV serotypes, a single pan-serotype neutralizing Ab may be extremely difficult to isolate.…”