The secretory immunoglobulin A (SIgA) is the predominant antibody in mucosal surfaces, playing a crucial role in immune defense by interacting with both commensal and pathogenic microbes. The secretory component (SC) is a part of SIgA as well as SIgM (secretory IgM), and facilitates the binding of polymeric IgA and IgM to epithelial cells, allowing their transcytosis and secretion into the lumen. The SC also enhances the stability of SIg by protecting them from proteolytic degradation, aids in their localization in the mucus layer, promotes intralumenal sequestration of bacteria, and performs homeostatic functions in the epithelium. 

This technology is a chimeric secretory immunoglobulin A (cSIgA) where the secretory component (SC) is replaced with a single domain antibody. This bispecific cSIgA can bind its target antigen and additional ligands by the engineered SC portion, such as toxins or surface antigens. This can be applied to treatment for mucosal infections such as Clostridium difficile. Compared to unmodified SIgA, cSlgA exhibits increased neutralization potency against C. difficile toxins, promotes bacterial clumping and cell rupture, and has decreased cytotoxicity. 

Benefits
Bispecific cSIgA binds its target antigen and additional ligands (e.g., toxins or surface antigens)

Applications
 Anti-infective, Diagnostics, Research Tool

Publication
Engineered Secretory Immunoglobulin A provides insights on antibody-based effector mechanisms targeting Clostridiodes difficile
Sonya Kumar Bharathkar, Michael J. Miller, Beth M. Stadtmueller bioRxiv 2023.11.08.566291; doi: https://doi.org/10.1101/2023.11.08.56629 [2]1