Application of antibody-like Down syndrome cell adhesion molecules isolated from immunized Kuruma shrimp for detection of human pathogens.

Mammalian antibodies are widely used as detection reagents. However, manipulating mammalian antibodies using molecular techniques is challenging, and the costs associated with these reagents are relatively high, because they are synthesized from two different genes. Accumulating evidence supports the existence of an antibody-like protein in crustaceans, known as the Down syndrome cell adhesion molecule (Dscam). Unlike mammalian antibodies, Dscam proteins are produced from a single gene, which makes their isolation, synthesis, and optimization through molecular techniques much easier. In this study, Kuruma shrimp (Marsupenaeus japonicus) were injected with antigens derived from human pathogens including Lassa virus glycoprotein, human immunodeficiency virus type 1 p24, and cholera toxin, as well as with Escherichia coli cells. We successfully constructed plasmids expressing Dscam fused with nano luciferase, enabling the detection of these antigens. The first to fourth immunoglobulin domains were sufficient for antigen binding. A total of 18 Dscam clones were constructed from two shrimp immunized with cholera toxin, and the most abundant sequences exhibited antigen-binding activity. Furthermore, peptidoglycan was identified as the antigen recognized by the Dscam isolated from E. coli-immunized shrimp. Since it is much easier to capture and culture live shrimp than mammals, the production costs for detection reagents are significantly reduced when using the antibody-like Dscam protein from shrimp. This novel biomaterial can be easily isolated via PCR, synthesized, and optimized through gene engineering technology, offering a cost-effective alternative for use as a detection reagent.