Abstract

Recent studies have demonstrated that immune-related recombinant proteins can enhance immune function, increasing host survival against infectious diseases in salmonids. This research evaluated inclusion bodies (IBs) of antimicrobial peptides (CAMPIB and HAMPIB) and a cytokine (IL1 beta IB and TNF alpha IB) as potential immunostimulants in farmed salmonids. For this purpose, we produced five IBs (including iRFPIB as a control), and we evaluated their ability to modulate immune marker gene expression of three IBs in the RTS11 cell line by RT-qPCR. Additionally, we characterized the scale-up of IBs production by comparing two different scale systems. The results showed that CAMPIB can increase the upregulation of tnf alpha, il1 beta, il8, and il10, HAMPIB significantly increases the upregulation of tnf alpha, inos, and il10, and IL1 beta IB significantly upregulated the expression of tnf alpha, il1 beta, and cox2. A comparison of IL1 beta IB production showed that the yield was greater in shake flasks than in bioreactors (39 +/- 1.15 mg/L and 14.5 +/- 4.08 mg/L), and larger nanoparticles were produced in shake flasks (540 +/- 129 nm and 427 +/- 134 nm, p < 0.0001, respectively). However, compared with its shake flask counterpart, the IL1 beta IB produced in a bioreactor has an increased immunomodulatory ability. Further studies are needed to understand the immune response pathways activated by IBs and the optimal production conditions in bioreactors, such as a defined medium, fed-batch production, and mechanical bacterial lysis, to increase yield.