The Immune Adjuvant Effects of Flounder (Paralichthys olivaceus) Interleukin-6 on E. tarda Subunit Vaccine OmpV.

Ming Guo,Xiuzhen Sheng,Xiaoqian Tang,Wenbin Zhan,Jing Xing

doi:10.3390/ijms18071445

Abstract

Interleukin-6 (IL-6) as a pleiotropic cytokine was widely used as an effective adjuvant for vaccines in mammals. In this study, the immune adjuvant effects of two forms of flounder (Paralichthys olivaceus) IL-6, including recombinant IL-6 (rIL-6) and pcDNA3.1-IL-6 (pcIL-6), were evaluated and comparatively analyzed on E. tarda subunit vaccine recombinant outer membrane protein V (rOmpV). The results showed that the relative percent survivals of flounder vaccinated with rOmpV plus rIL-6 or pcIL-6 were significantly higher than that in the two control groups, rOmpV plus recombinant 6× histidine-tag (rHis) or empty expression vector pcDNA3.1 (pcN3). The levels of specific serum antibodies and surface membrane immunoglobulin-positive (sIg+) lymphocytes in peripheral blood, spleen, and head kidney in the two adjuvant groups were also much higher than that in the two control groups. Compared with the two control groups, higher upregulated expressions of major histocompatibility complex class Iα (MHCIα), cluster of differentiation 8α (CD8α), MHCIIα, CD4-1, interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) were detected in flounder vaccinated with rOmpV plus rIL-6 or pcIL-6 after challenge. In addition, the rOmpV plus rIL-6 could induce significant higher levels of specific serum antibodies, sIg+ lymphocytes and four genes expressions than rOmpV plus pcIL-6. These results demonstrated that both rIL-6 and pcIL-6 used as adjuvants could enhance the immune response and evoke immune protections against E. tarda infection, which has a significant value in controlling diseases using vaccines in flounder.

Highlights

Since vaccines have advantages in safety, environmental friendliness, and long-term efficacy of protection [1], various types of vaccines including attenuated live vaccines, inactivated vaccines, subunit vaccines, and DNA vaccines have been designed for a diverse range of uses in disease prevention in aquaculture [2,3,4]
Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the distinct bands of 27 KDa and 26 KDa were matched to the expected molecular masses of recombinant IL-6 (rIL-6) and recombinant outer membrane protein V (rOmpV), respectively (Figure 1)
ROmpV + rIL-6-vaccinated fish induced higher levels of surface Ig (sIg)+ lymphocytes and specific serum antibodies compared with rOmpV + pcIL-6-vaccinated fish, and higher immune protection was found. These results showed that the humoral immunity enhanced by rIL-6 was much higher in magnitude than that of pcIL-6, suggesting that the stronger humoral immune response was related to higher protective effects

Summary

Introduction

Since vaccines have advantages in safety, environmental friendliness, and long-term efficacy of protection [1], various types of vaccines including attenuated live vaccines, inactivated vaccines, subunit vaccines, and DNA vaccines have been designed for a diverse range of uses in disease prevention in aquaculture [2,3,4]. Many vaccines such as subunit vaccines fail to induce strong immune responses and obtain satisfactory immune protection when administered without adjuvants. There is an urgent need for the safety and effectiveness of novel adjuvants in fish vaccines

Methods

Results

Conclusion