Basic immunology studies and development of tools to monitor immune responses in cleaner fish

Biological control of salmon lice by use of cleaner fish has attracted renewed attention the last decade, and farming of ballan wrasse and lumpfish for this purpose is increasing. New species in aquaculture necessitate development of new vaccines, and accordingly, it is of interest to gain insight into the immune system of wrasses and lumpfish and develop tools to monitor immune responses in these species. In the first part of the project, IgM of cleaner fish were purified and characterized, and specific antisera against IgM were produced in rabbits. Interestingly, IgM of cleaner fish binds strongly to protein A, implicating that commercial reagents can be used to study IgM. Magnetic beads coated with protein A were used to purify antibodies from skin and gut mucus. Key components of the adaptive immune system in ballan wrasse and lumpfish were identified and characterized by searches in transcriptome databases (and in the genome of ballan wrasse). It was primarily focused on genes encoding the antibody classes IgM, IgD and IgT, and the most important T-cell markers. Analysis of gene expression in a series of tissues showed an extraordinarily high level of IgM in gut, and an elevated immune activity, especially in the hindgut. In collaboration with researchers at UiT and Vaxxinova immune responses to different vaccination strategies were analysed.

The present project will reveal key immune genes and characteristics of the immune system in wrasse and lumpfish by transcriptome and immunohistochemistry studies. Transcriptome analysis of ballan wrasse will be performed on high throughput sequence data generated by a collaborating research group. Samples collected from vaccination trials on lumpfish will be subjected to transcriptome sequencing in the course of the present project (one dip vaccine and one injection vaccine). This experiment will reveal differences in mucosal and systemic immune responses, components of special importance and possible species-specific characteristics of the immune system in lumpfish. Antisera raised against IgM in wrasse and lumpfish, respectively will be further characterized, and T-cell specific antisera will be developed. B- and T-cell specific antisera will be used, in addition to transcriptome analyses, to study humoral and mucosal immune responses. In collaboration with other researchers we will find out whether there is a lymphoid tissue in the gills of cleaner fish; equivalent to ILT in Atlantic salmon.