Identification of a novel CCR7 gene in rainbow trout with differential expression in the context of mucosal or systemic infection

• Published in: Developmental and comparative immunology Vol. 38; no. 2; pp. 302 - 311
• Main Authors: Ordás, M. Camino, Castro, Rosario, Dixon, Brian, Sunyer, J. Oriol, Bjork, Sarah, Bartholomew, Jerri, Korytar, Tomas, Köllner, Bernd, Cuesta, Alberto, Tafalla, Carolina
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.10.2012
• Subjects: Animals; B-lymphocytes; bacteria; CCR7; CCR7 receptor; Ceratomyxa; Ceratomyxa shasta; chemokine CCL19; chemokine CCL21; Chemokine receptors; Chemokines; Fish Diseases - immunology; Fish Proteins - genetics; Fish Proteins - immunology; Gastrointestinal Tract - immunology; gene expression; gene expression regulation; genes; gills; hindgut; intestinal mucosa; kidneys; Leukocytes - immunology; lymph nodes; Lymphocytes; mammals; messenger RNA; Mucosal immunity; Mucous Membrane - immunology; Myxozoa; Novirhabdovirus; Oncorhynchus mykiss; Oncorhynchus mykiss - genetics; Oncorhynchus mykiss - immunology; Organ Specificity; Parasitic Diseases, Animal - immunology; Phylogeny; population; Rainbow trout; Receptors, CCR7 - genetics; Receptors, CCR7 - immunology; Rhabdoviridae Infections - immunology; Rhabdoviridae Infections - veterinary; spleen; T-lymphocytes; thymus gland; Transcriptome; Viral hemorrhagic septicemia virus; viruses; CCR7; Mucosal immunity; Lymphocytes; Chemokines; Chemokine receptors; Rainbow trout
• ISSN: 0145-305X; 1879-0089
• DOI: 10.1016/j.dci.2012.07.001

► A CCR7 orthologue has been identified in rainbow trout (Oncorhynchus mykiss). ► CCR7 is strongly transcribed in thymus and spleen T cells. ► CCR7 transcription is down-regulated in head kidney and spleen of VHSV-infected fish. ► VHSV bath infection induces significant changes in CCR7 transcription in the gills. ► CCR7 is up-regulated in B cells recruited to the gut in response to Ceratomyxa shasta. In mammals, CCR7 is the chemokine receptor for the CCL19 and CCL21 chemokines, molecules with a major role in the recruitment of lymphocytes to lymph nodes and Peyer’s patches in the intestinal mucosa, especially naïve T lymphocytes. In the current work, we have identified a CCR7 orthologue in rainbow trout (Oncorhynchus mykiss) that shares many of the conserved features of mammalian CCR7. The receptor is constitutively transcribed in the gills, hindgut, spleen, thymus and gonad. When leukocyte populations were isolated, IgM+ cells, T cells and myeloid cells from head kidney transcribed the CCR7 gene. In blood, both IgM+ and IgT+ B cells and myeloid cells but not T lymphocytes were transcribing CCR7, whereas in the spleen, CCR7 mRNA expression was strongly detected in T lymphocytes. In response to infection with viral hemorrhagic septicemia virus (VHSV), CCR7 transcription was down-regulated in spleen and head kidney upon intraperitoneal infection, whereas upon bath infection, CCR7 was up-regulated in gills but remained undetected in the fin bases, the main site of virus entry. Concerning its regulation in the intestinal mucosa, the ex vivo stimulation of hindgut segments with Poly I:C or inactivated bacteria significantly increased CCR7 transcription, while in the context of an infection with Ceratomyxa shasta, the levels of transcription of CCR7 in both IgM+ and IgT+ cells from the gut were dramatically increased. All these data suggest that CCR7 plays an important role in lymphocyte trafficking during rainbow trout infections, in which CCR7 appears to be implicated in the recruitment of B lymphocytes into the gut.