Antigen uptake and retention in the nasal cavity of rainbow trout (Onchorhynchus mykiss): implications for vaccine development 2815

Description The mucosal surfaces of fish, including the nasal cavity, skin, gills, and gastrointestinal tract, serve as the first line of defense against pathogens in aquatic environments and act as locations for both immune surveillance and immune response induction. The organized nasopharynx-associated lymphoid tissue (O-NALT) is a structure in the teleost nasal cavity that expresses markers of mammalian germinal centers and is a putative inductive site. The goal of this study is to determine whether nasal antigens are taken up in the O-NALT, using juvenile rainbow trout and intranasally-delivered antigens. Anti-MHC II staining in control animals showed that the O-NALT is rich in cells expressing high levels of MHC II, many of which appear to be in the B cell zone of the O-NALT. Confocal microscopy showed that antigens delivered intranasally, including live bacteria, were taken up and stored in the O-NALT. By flow cytometry, intranasally delivered dextran was rapidly taken up by both lymphoid and myeloid cells in the O-NALT and increased over time until at least 4 hours. Confocal imaging at later time points showed that dextran localized in fibroblasts in the connective tissue underneath the O-NALT, storing it for multiple days. Our findings indicate that O-NALT are capable of antigen uptake and storage, furthering our understanding of teleost mucosal immunology.