Development of a modified yeast display system for screening antigen-specific variable lymphocyte receptor B in hagfish (Eptatretus burgeri).

The variable lymphocyte receptor B (VLRB) of jawless vertebrates has a similar function to the antibodies produced by jawed vertebrates, and has been considered as an alternative source to mammalian antibodies for use in biological research. We developed a modified yeast display vector system (pYD8) to display recombinant hagfish VLRB proteins on the extracellular surface of yeast for the isolation of antigen-specific VLRBs. After observing an up-regulation in the VLRB response in hagfish immunized with hemagglutinin 1 of avian influenza virus H9N2 subtype (H9N2-HA1), the antigen-specific VLRBs decorated on the yeast's surface were selected by quantitative library screening through magnetic-activated cell sorting (MACS) and fluorescent-activated cell sorting (FACS). We also demonstrated a strong specificity of the antigen-specific VLRBs, when expressed as a secreted protein using a mammalian expression system. Together, our findings suggest that the pYD8 vector system could be useful for screening antigen-specific hagfish VLRBs, and the specificity of secreted VLRB may have potential for a variety of biological applications.