Antigen encapsulated alginate-coated chitosan microspheres stimulate both innate and adaptive immune responses in fish through oral immunization

The potential of alginate-coated chitosan microspheres to act as an antigen carrier through oral vaccination was explored in fish. Among different antigenic formulations such as antigen-loaded alginate-coated and alginate-uncoated chitosan microspheres, empty alginate-coated chitosan microspheres and free whole-cell antigen, only alginate-coated chitosan microspheres gave promising results for stimulating both adaptive and innate immune response up to 6 weeks of post-immunization. In addition, alginate-coated chitosan microspheres modulated antigen-release behavior, maintained structural integrity and stability and gave effective protection to antigens from acidic degradation in vitro for 12 h. However, none of these formulations tested in this study are effective for protecting fish against Aeromonas hydrophila infection under the conditions evaluated in the present work. The enhancement of the immune response observed with the antigen-loaded alginate-coated chitosan microspheres demonstrates its promising effect for oral antigen delivery in fish.