Aeromonas salmonicida Infection Only Moderately Regulates Expression of Factors Contributing to Toll-Like Receptor Signaling but Massively Activates the Cellular and Humoral Branches of Innate Immunity in Rainbow Trout (Oncorhynchus mykiss).
Toll-like receptors (TLRs) are known to detect a defined spectrum of microbial structures. However, the knowledge about the specificity of teleost Tlr factors for distinct pathogens is limited so far. We measured baseline expression profiles of 18 tlr genes and associated signaling factors in four immune-relevant tissues of rainbow trout Oncorhynchus mykiss. Intraperitoneal injection of a lethal dose of Aeromonas salmonicida subsp. salmonicida induced highly increased levels of cytokine mRNAs during a 72-hour postinfection (hpi) period. In contrast, only the fish-specific tlr22a2 and the downstream factor irak1 featured clearly increased transcript levels, while the mRNA concentrations of many other tlr genes decreased. Flow cytometry quantified cell trafficking after infection indicating a dramatic influx of myeloid cells into the peritoneum and a belated low level immigration of lymphoid cells. T and B lymphocytes were differentiated with RT-qPCR revealing that B lymphocytes emigrated from and T lymphocytes immigrated into head kidney. In conclusion, no specific TLR can be singled out as a dominant receptor for A. salmonicida. The recruitment of cellular factors of innate immunity rather than induced expression of pathogen receptors is hence of key importance for mounting a first immune defense against invading A. salmonicida.
Leibniz Institute for Farm Animal Biology (FBN), Institute of Genome Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
Andreas
A
Brietzke
Friedrich Loeffler Institute, Federal Research Institute for Animal Health, Institute of Immunology, Südufer 10, Insel Riems, 17493 Greifswald, Germany ; Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104, USA.
Tomáš
T
Korytář
Friedrich Loeffler Institute, Federal Research Institute for Animal Health, Institute of Immunology, Südufer 10, Insel Riems, 17493 Greifswald, Germany.
Joanna
J
Jaros
Friedrich Loeffler Institute, Federal Research Institute for Animal Health, Institute of Immunology, Südufer 10, Insel Riems, 17493 Greifswald, Germany.
Bernd
B
Köllner
Leibniz Institute for Farm Animal Biology (FBN), Institute of Genome Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
Tom
T
Goldammer
Leibniz Institute for Farm Animal Biology (FBN), Institute of Genome Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
Hans-Martin
HM
Seyfert
Leibniz Institute for Farm Animal Biology (FBN), Institute of Genome Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
Alexander
A
Rebl
D048409:Aeromonas salmonicida / Q000276:immunology*; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D005393:Fish Diseases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D015870:Gene Expression; D016905:Gram-Negative Bacterial Infections / Q000235:genetics / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D007113:Immunity, Innate; D007962:Leukocytes / Q000276:immunology / Q000473:pathology; D022423:Myeloid Cells / Q000276:immunology / Q000378:metabolism; D009928:Organ Specificity / Q000235:genetics; D010537:Peritoneum / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction; D013154:Spleen / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D051193:Toll-Like Receptors / Q000235:genetics / Q000378:metabolism*
D016207:Cytokines; D051193:Toll-Like Receptors