Role of Pathogen-Derived Cell Wall Carbohydrates and Prostaglandin E2 in Immune Response and Suppression of Fish Immunity by the Oomycete Saprolegnia parasitica

Rodrigo Belmonte, Tiehui Wang, Gary J Duncan, Ida Skaar, Hugo Mélida, Vincent Bulone, Pieter van West, Christopher J Secombes* (Corresponding Author)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)


Saprolegnia parasitica is a freshwater oomycete that is capable of infecting several species of fin fish. Saprolegniosis, the disease caused by this microbe, has a substantial impact on Atlantic salmon aquaculture. No sustainable treatment against saprolegniosis is available, and little is known regarding the host response. In this study, we examined the immune response of Atlantic salmon to S. parasitica infection and to its cell wall carbohydrates. Saprolegnia triggers a strong inflammatory response in its host (i.e., induction of interleukin-1β1 [IL-1β1], IL-6, and tumor necrosis factor alpha), while severely suppressing the expression of genes associated with adaptive immunity in fish, through downregulation of T-helper cell cytokines, antigen presentation machinery, and immunoglobulins. Oomycete cell wall carbohydrates were recognized by fish leukocytes, triggering upregulation of genes involved in the inflammatory response, similar to what is observed during infection. Our data suggest that S. parasitica is capable of producing prostaglanding E2 (PGE2) in vitro, a metabolite not previously shown to be produced by oomycetes, and two proteins with homology to vertebrate enzymes known to play a role in prostaglandin biosynthesis have been identified in the oomycete genome. Exogenous PGE2 was shown to increase the inflammatory response in fish leukocytes incubated with cell wall carbohydrates while suppressing genes involved in cellular immunity (gamma interferon [IFN-γ] and the IFN-γ-inducible protein [γ-IP]). Inhibition of S. parasitica zoospore germination and mycelial growth by two cyclooxygenase inhibitors (aspirin and indomethacin) also suggests that prostaglandins may be involved in oomycete development.

Original languageEnglish
Pages (from-to)4518-4529
Number of pages12
JournalInfection and Immunity
Issue number11
Early online date7 Oct 2014
Publication statusPublished - Nov 2014

Bibliographical note

Copyright © 2014, American Society for Microbiology. All Rights Reserved.

This work was supported by the European Commission through Marie Curie actions (ITN-SAPRO-238550). We thank J. Dieguez-Uribeondo from the Royal Botanical Gardens (CSIC, Spain) for kindly providing the Saprolegnia diclina VS20 strain. We thank Alan Bowman from the University of Aberdeen for his input into the design of PGE2 purification and analysis.


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