Comparative immunohistological study on using capsaicin, piperine, and okadaic acid for the transepithelial passage of the inactivated viral and bacterial vaccines in fish

The practical difficulty of parenteral application of fish vaccines against devastating fish diseases diverted the interest toward oral vaccination. Search for effective methods to enhance the oral uptake of viral and bacterial vaccines is continuing. The current research focus on a new role of mucosal fish vaccine adjuvants inducing the antigen uptake by enhancing vascularity or increasing intestinal permeability. Some inflammatory substances cause reversible pathology to the intestinal epithelium, which could be employed for the transepithelial passage of vaccine particles. The natural inflammatory substances used were capsaicin, piperine, and okadaic acid as 1 mg, 2 mg, and 1 μg/fish, respectively. Two inactivated vaccines were used as antigens to test the effect of these inflammatory substances in two different fish hosts. Tested vaccines were inactivated redspotted grouper nervous necrosis virus vaccine in sevenband grouper (Epinephelus septemfasciatus) and inactivated Edwardsiella tarda vaccine in red sea bream (Pagrus major) fish models. The inflammatory substances and each vaccine were anally intubated to fish. Capsaicin proved to be effectively aiding the transepithelial passage of vaccine particles more than piperine, while okadaic acid had no detectable effect. Schematic presentation of a trial investigating the possibility of using three natural inflammatory substances: capsaicin, piperine, and okadaic acid to enhance the paracellular permeability of intestinal epithelium of fish for viral and bacterial inactivated vaccines. In which, sevenband grouper (Epinephelus septemfasciatus) and inactivated redspotted grouper nervous necrosis virus vaccine as viral vaccine experimental model, and red sea bream (Pagrus major), and inactivated Edwardsiella tarda vaccine as bacterial vaccine experimental model. The Both inflammatory substances and vaccine were introduced via anal intubation to fish. Capsaicin proved to be effective to aid the transepithelial passage of vaccine particles more than piperine, while okadaic acid had no detectable effect. Capsaicin, piperine, and okadaic acid were investigated for helping fish viral and bacterial inactivated vaccines intestinal uptake. Capsaicin aided the transepithelial passage of vaccine particles more than piperine Okadaic acid did not help.