Fate of Antigens and Post Injection Response in Teleost Fish, Using Zebrafish (Danio rerio [L]) as a Model Species.

The world of fish immunology and vaccination has been constantly changing since the first forays in the late 1930s. During this time, one of the most important discoveries was the identification of IgZ, a teleost fish exclusive mucosa associated immunoglobulin. As immunoglobulins like IgZ are essential for mounting an immune response, this pilot study focused on the reaction of IgZ and other commonly used immune response genes to track how the immune system processes antigens that get to the host at the surface layer (intradermal) or at a deeper level (intraperitoneal). Using two antigens, Bovine Serum Albumin (BSA) and whole yeast cells, a two-fold view into antigen uptake and response is visualized by whole mount slides stained via immunohistochemistry and quantification of gene expression is shown utilizing qPCR. Immunohistochemistry results revealed the presence of antigen in a multitude of locations from both intraperitoneal and intradermal delivery routes, including the liver, kidney, intraperitoneal cavity, and nares. Comparison of injection methods for each antigen resulted in a p value of 0.02 for yeast and 0.69 for BSA (significant result if p ≤ 0.05). Gene expression results showed no significant (p = 0.05) difference between intraperitoneal and intradermal injections across three different genes upregulated during infections (IgZ, IgM, and il8). Because this study is a pilot study, it is suggested that a more in depth run of this experiment be done after more optimization, as the results are not conclusive enough to determine the effectiveness of intradermal injection in comparison to intraperitoneal injection. If the trend shown here continues, however, there is a possibility of being able to use the intradermal route for vaccine delivery, if it is of a similar level of efficacy when compared to the current standard for injection vaccination, intraperitoneal delivery.