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Fish Shellfish Immunol. 2017 Dec;71:160-170. doi: 10.1016/j.fsi.2017.10.001. Epub 2017 Oct 5.

More than just antibodies: Protective mechanisms of a mucosal vaccine against fish pathogen Flavobacterium columnare.

Author information

1
School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL 36849, USA.
2
Marine Science and Engineering College, Qingdao Agricultural University, Qingdao 266109, China.
3
United States Department of Agriculture, Agricultural Research Service, Aquatic Animal Health Research Unit, Auburn, AL 36832, USA.
4
School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL 36849, USA; Department of Animal Medicine, Faculty of Veterinary Medicine, Assiut University, Assiut 71526, Egypt.
5
School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL 36849, USA. Electronic address: peatmer@auburn.edu.

Abstract

A recently developed attenuated vaccine for Flavobacterium columnare has been demonstrated to provide superior protection for channel catfish, Ictalurus punctatus, against genetically diverse columnaris isolates. We were interested in examining the mechanisms of this protection by comparing transcriptional responses to F. columnare challenge in vaccinated and unvaccinated juvenile catfish. Accordingly, 58 day old fingerling catfish (28 days post-vaccination or unvaccinated control) were challenged with a highly virulent F. columnare isolate (BGSF-27) and gill tissues collected pre-challenge (0 h), and 1 h and 2 h post infection, time points previously demonstrated to be critical in early host-pathogen interactions. Following RNA-sequencing and transcriptome assembly, differential expression (DE) analysis within and between treatments revealed several patterns and pathways potentially underlying improved survival of vaccinated fish. Most striking was a pattern of dramatically higher basal expression of an array of neuropeptides (e.g. somatostatin), hormones, complement factors, and proteases at 0 h in vaccinated fish. Previous studies indicate these are likely the preformed mediators of neuroendocrine cells and/or eosinophilic granular (mast-like) cells within the fish gill. Following challenge, these elements fell to almost undetectable levels (>100-fold downregulated) by 1 h in vaccinated fish, suggesting their rapid release and/or cessation of synthesis following degranulation. Concomitantly, levels of pro-inflammatory cytokines (IL-1b, IL-8, IL-17) were induced in unvaccinated fish. In contrast, in vaccinated catfish, we observed widespread induction of genes needed for collagen deposition and tissue remodeling. Taken together, our results indicate an important component of vaccine protection in fish mucosal tissues may be the sensitization, proliferation and arming of resident secretory cells in the period between primary and secondary challenge.

KEYWORDS:

Attenuated vaccine; Channel catfish; Eosinophilic granular (mast-like) cells; Flavobacterium columnare; Transcriptome

PMID:
28989091
DOI:
10.1016/j.fsi.2017.10.001
[Indexed for MEDLINE]

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