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Research Project: Pathogen Characterization, Host Immune Response and Development of Strategies to Reduce Losses to Disease in Aquaculture

Location: Aquatic Animal Health Research

Title: Expression of immune genes in skin of channel catfish immunized with live theronts of Ichthyophthirius multifiliis

Author
item Moreira, Gabriel - Universidad De Sao Paulo
item Shoemaker, Craig
item Zhang, Dunhua
item Xu, Dehai

Submitted to: Parasite Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2016
Publication Date: 1/19/2017
Citation: Moreira, G.S., Shoemaker, C.A., Zhang, D., Xu, D. 2017. Expression of immune genes in skin of channel catfish immunized with live theronts of Ichthyophthirius multifiliis. Parasite Immunology. 39:e12397.

Interpretive Summary: Channel catfish is a major cultured fish in the USA and the production of catfish suffers great losses ($1.2 million annually in the US alone) caused by the protozoan parasite Ichthyophthirius multifiliis (Ich). Channel catfish surviving natural Ich infections and/or immunized with live Ich theronts (infective stage of Ich) develop strong immune responses. Little is known about which immune genes are induced, how they interact and ultimately result in specific immunity against the parasite. The objective of this study was to evaluate the differential expression of 21 immune genes correlated with innate and adaptive immune response in skin from channel catfish at different times after immunization with live Ich theronts. Most of cytokine genes, inflammatory protein genes, and cell receptor genes (MHCI, CD8+, CD4+, TCR-a TCR-ß) showed a rapid up-regulation at h4 while the MHCII did not show significant up-regulation. Immunoglobulin IgM gene showed up-regulation from h4 until D2 and up-regulation of immunoglobulin IgD gene was only detected at D1 until D10. This study demonstrated that differential expression of genes involved in innate and adaptive immunity to Ich and significant protection against infection by the parasite following live theront vaccination. Results presented in this work will be useful for future development of alternative strategies to control parasite Ich.

Technical Abstract: There is limited information on innate and adaptive immune gene expression in the skin of channel catfish, Ictalurus punctatus immunized with Ichthyophthirius multifiliis (Ich). The objective of this study was to evaluate differential expression of innate and adaptive immune genes, including immunoglobulin, immune cell receptor, cytokine, inflammatory protein, toll-like receptors (TLR) and recombination-activating gene (RAG) in skin from channel catfish at different times after immunization with live theronts of Ich. The gene expression of innate system as cytokines (IL1-ßa, IL1-ßb, IFN-y, TGF1-ß and TNF-a) showed a significant up-regulation at the day 1 (D1) post immunization. Inflammatory protein (NF-KB and INOS 2) expression increased from D1 to D10, and the expression of INOS 1 increased at D1, D6 and D10. Expression of TLR genes exhibited a rapid increase from hour 4 (h4) to D10 post immunization. Genes of the adaptive response such as the cell receptor MHCI, CD8+, CD4+ and TCR-a showed up-regulation at D1, D6 and D10, while the TCR-ß expression increased rapidly at h4 and remained up-regulated until D10. MHCII did not show significant up-regulation. Immunoglobulin IgM up-regulation was detected from h4 until D2 while the IgD was increased from D1 until D10. The gene RAG1 and RAG2 exhibited an increase from D1 to D10 post immunization. This study demonstrated differential expression of genes involved in innate and adaptive immunity to Ich following live theront vaccination and significant protection against infection by Ich.