Molecular characterisation of key components of the mucosal immune system in Atlantic salmon (Salmo salar L) and transcriptome analysis of responses against the salmon louse (Lepeophtheirus salmonis)

• Published in: Veterinary Immunology and Immunopathology
• Main Author: Tadiso, Tariku Markos
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Bergen 2012
• Subjects: VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920; VDP::Mathematics and natural science: 400::Basic biosciences: 470; Atlantic salmon; Salmo salar
• Online Access: http://hdl.handle.net/1956/5823

Mucosal immunity in mammals is mediated mainly by secretory immunoglobulin A (SIgA), which is produced by IgA plasma cells commonly located in the lamina propria, and a transport system involving the polymeric Ig receptor (pIgR). In teleost fish, IgM plays some roles associated with mucosal defence. Very recent findings indicate that IgT, an antibody exclusive to teleosts, might have a special role in mucosal immune responses, and a possible pIgR counterpart has been identified. The salmon louse (Lepeophtheirus salmonis Krøyer), an ectoparasitic copepod targeting the skin (and the gill to a lesser extent), has been a major challenge to the aquaculture industry. While the first line of defence against this parasite is crucial, equally important, in the context of vaccine development is the generation of information on the adaptive immune system. Based on this line of reasoning, Atlantic salmon IgT and pIgR were selected as targets for further characterization in the present study. Three distinct IgT heavy chain (????) sub-variants, with an identity index of 76-80%, were described. The identity index between ????1 and ????1 (the first constant domains of the IgT and IgM heavy chains, respectively) in Atlantic salmon is 52%. It is plausible to assume that this relatively high similarity is a result of interactions with common light chains. The relative abundance of ????????????????????????and???????? transcripts in a series of tissues revealed an overall expression pattern of IgM >> IgT > IgD. Interestingly, challenge experiments with salmon louse showed 10 fold increase of IgM and IgT mRNA in skin samples, supporting the assumption that these antibodies are involved in mucosal immune responses. The search for pIgR homologues in Atlantic salmon resulted in two pIgR-like candidates: Salsal pIgR and Salsal pIgRL. Meanwhile, a comparative evaluation was made to a series of CD300-like molecules (CMRF-35 like molecules, CLM) reported to the databanks. Salsal pIgR and Salsal pIgRL were identified on the basis of similarity to homologous genes, ...