Mucosal delivery of fish vaccines: Local and systemic immunity following mucosal immunisations.

Abstract Fish mucosal organs are directly exposed to aquatic environment, which is suited to the colonization and growth of microorganisms, and thus are considered to play an important role in maintaining homeostasis and preventing entry of invading pathogens. Researches on fish mucosal immunity have shown that mucosal organs in fish such as gill, skin, intestine, olfactory organs harbour lymphoid cells including T and B cells as well as dendritic-like cells. The findings on immune responses following direct administration with antigens into the mucosal organs will help to shed light on developing fish mucosal vaccines. The present review highlighted vaccine deliveries via mucosal organs, especially focusing on methods other than typical mucosal vaccine platforms, such as oral and immersion vaccines. In addition, we proposed a hypothesis that mucosal tissues are important sites for generating cell-mediated immunity following vaccination with extracellular antigens.