Development of Anti-Peptide Antibody Specific for IgM Heavy Chain of Oryzias latipes and Its Application to Assay of Immune Response Triggered by BSA-Coated Microplastics

Teleost Immunoglobulin M (IgM) is a crucial molecule in the adaptive immune response in teleost fish. Therefore, specific antibodies against IgM are essential tools for studying immune responses and evaluating vaccine efficacy across various teleost species. Producing antibodies using synthetic peptide antigens is a convenient approach when the IgM sequence is known. However, anti-peptide antibodies often fail to recognize natural antigens in either their denatured or native form, limiting their utility for antigen detection. In the present study, we identified a highly antigenic amino acid sequence stretch between the CH3 and CH4 domains of the IgM heavy chain. Using medaka fish (Oryzias latipes) as a model, we generated anti-peptide antibodies and tested their specificity and reactivity against native serum IgM. Based on in silico analysis, we hypothesize that this antigenic site is also applicable to other teleost species. Using this antibody, we successfully assessed systemic and mucosal antibody response following medaka exposure to bovine serum albumin-coated microplastics via immersion.