Polyreactivity of antibodies from different B cell subpopulations is determined by distinct sequence patterns of variable region

An antibody molecule that is able to bind to multiple distinct antigens is defined as polyreactive. In the present study we performed statistical analyses to assess sequence correlates of polyreactivity of >600 antibodies cloned from different B cell types of healthy humans. The data reveled a number of sequence patterns of variable regions of heavy and light immunoglobulin chains that determine polyreactivity. The most prominent identified patterns were increased number of basic amino acid residues, reduced frequency of acidic residues, increased number of aromatic and hydrophobic residues, as well as longer length of CDR L1. Importantly, our study revealed that antibodies isolated from different B cell population used distinct sequence patterns (or combinations of them) for polyreactive antigen binding. Furthermore, we combined the data from sequence analyses with molecular modeling of selected polyreactive antibodies, and demonstrate that human antibodies can use multiple pathways for achieving antigen binding promiscuity. These data reconcile some contradictions in literature regarding the determinants of antibody polyreactivity. Moreover, our study demonstrates that mechanism of polyreactivity of antibodies evolves during immune response and might be tailored to specific functional properties of different B cell compartments. Finally, these data can be of use for efforts in development and engineering of therapeutic antibodies.