Lampreys possess an alteative adaptive immune system that uses variable lymphocyte receptors (VLRs) to bind to antigens rather than the immunoglobulin (Ig)-based antigen receptors used by jawed vertebrates [1,2]. Variable lymphocyte receptor B (VLRB) responds to influenza A virus (IAV) by recognizing the major antigenic sites in a surface glycoprotein (HA) globular head domain [3]. Additionally, VLRB responds to human blood type O erythrocytes by forming a VLR-antigen complex that recognizes the dominant H-trisaccharide antigen [4].