CpG ODN 1668 as TLR9 agonist mediates humpback grouper (Cromileptes altivelis) antibacterial immune responses

Xiaojuan Chen; Panpan Zhang; Pengshuo Li; Guotao Wang; Jianlong Li; Ying Wu; Zhenjie Cao; Yongcan Zhou; Yun Sun

doi:10.1016/j.fsi.2023.108839

CpG ODN 1668 as TLR9 agonist mediates humpback grouper (Cromileptes altivelis) antibacterial immune responses

Fish Shellfish Immunol. 2023 Jul:138:108839. doi: 10.1016/j.fsi.2023.108839. Epub 2023 May 18.

Authors

Xiaojuan Chen¹, Panpan Zhang², Pengshuo Li³, Guotao Wang², Jianlong Li¹, Ying Wu¹, Zhenjie Cao¹, Yongcan Zhou¹, Yun Sun⁴

Affiliations

¹ Collaborative Innovation Center of Marine Science and Technology, State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, Haikou, 570228, China; Hainan Provincial Key Laboratory for Tropical Hydrobiology and Biotechnology, College of Marine Science, Hainan University, Haikou, 570228, China.
² Sanya Nanfan Research Institute, Hainan University, Sanya, 572022, China; Collaborative Innovation Center of Marine Science and Technology, State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, Haikou, 570228, China.
³ Sanya Nanfan Research Institute, Hainan University, Sanya, 572022, China; Hainan Provincial Key Laboratory for Tropical Hydrobiology and Biotechnology, College of Marine Science, Hainan University, Haikou, 570228, China.
⁴ Sanya Nanfan Research Institute, Hainan University, Sanya, 572022, China; Collaborative Innovation Center of Marine Science and Technology, State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, Haikou, 570228, China; Hainan Provincial Key Laboratory for Tropical Hydrobiology and Biotechnology, College of Marine Science, Hainan University, Haikou, 570228, China. Electronic address: syshui207@126.com.

PMID: 37207883
DOI: 10.1016/j.fsi.2023.108839

Abstract

Cromileptes altivelis (humpback grouper) is the main farmed species in the southern coastal area of China owing to its important economic value. Toll-like receptor 9 (TLR9) belongs to the toll-like receptor (TLR) family and functions as a pattern recognition receptor, recognising unmethylated oligodeoxynucleotides containing the CpG motif (CpG ODNs) in bacterial and viral genomes, thereby activating host immune response. In this study, the C. altivelis TLR9 (CaTLR9) ligand CpG ODN 1668 was screened and found to significantly enhance the antibacterial immunity of humpback grouper in vivo and head kidney lymphocytes (HKLs) in vitro. In addition, CpG ODN 1668 also promoted the cell proliferation and immune gene expression of HKLs and strengthened the phagocytosis activity of head kidney macrophages. However, when the CaTLR9 expression was knocked down in the humpback group, the expression levels of TLR9, myeloid differentiation factor 88 (Myd88), tumour necrosis factor-α (TNF-α), interferon γ (IFN-γ), interleukin-1β (IL-1β), IL-6, and IL-8 were significantly reduced, and the antibacterial immune effects induced by CpG ODN 1668 were mostly abolished. Therefore, CpG ODN 1668 induced antibacterial immune responses in a CaTLR9-dependent pathway. These results enhance the knowledge of the antibacterial immunity of fish TLR signalling pathways and have important implications for exploring natural antibacterial molecules in fish.

Keywords: Antibacterial immunity; CaTLR9; CpG ODN 1668; Cromileptes altivelis.

MeSH terms

Adjuvants, Immunologic / pharmacology
Animals
Bass* / genetics
Bass* / metabolism
Immunity
Oligodeoxyribonucleotides / pharmacology
Toll-Like Receptor 9* / genetics
Toll-Like Receptor 9* / metabolism

Substances

Toll-Like Receptor 9
Adjuvants, Immunologic
Oligodeoxyribonucleotides