Parameters to evaluate the immunostimulant effect of Zymosan A in head kidney leucocytes (HKL) of salmonids
The interest in characterizing fish immune responses against pathogens or discovering new immunostimulant molecules requires the use of mass screening techniques. The classical model has been the challenge in 1000 L tanks, using a high number of fishes, resulting in high economic cost. In this work, the purpose was to minimize the costs of such tests using in vitro cellular models. In primary cultures of head kidney leucocytes (HKL) immune response to Zymosan A, a type of β-glucan, was evaluated. The quantification and detection of pro-inflammatory cytokines was done based on both enzymatic activity and ELISA. The activity of phagocyte oxidase and inducible nitric oxide synthase (iNOS) was measured indirectly through NBT reduction by reactive oxygen species and Griess reaction to nitric oxide, respectively. For detecting pro-inflammatory cytokines such as TNF-α, IL-6 and IL-Ιβ, monospecific antibodies generated in our laboratory were used by indirect ELISA. The immune parameters were evaluated at different concentration of Zymosan A and the evolution of the immune response over time was established. The results suggest the better time for evaluating the immunostimulant capacity of glucans and the appropriate dose of it, which is required to demonstrate the activation of macrophages (ROS and iNOS) and the production of pro-inflammatory molecules, both as indicators of good immune response. Currently, work is being conducted improving these methods, creating an ELISA sandwich and generating antibodies against total proteins of HKL for pre-absorption of induced samples. In particular, the implementation of ELISA for the characterization of cytokine secretion profiles is a biotechnological contribution in aquaculture, which has not been implemented before this work.