Gut Associated Lymphoid Tissue (GALT) primary cells and stable cell lines as predictive models for intestinal health in rainbow trout (Oncorhynchus mykiss)

Abstract

The use of functional feeds for farmed fish is now regarded as a key factor in improving fish health and performance against infectious disease. However, the mechanisms by which these nutritional components modulate the immune response are not fully understood. The present study was undertaken to identify the suitability of both primary gut-associated lymphoid tissue (GALT) leucocyte cells and established rainbow trout cell lines as potential alternative methods to test functional feed ingredients prior to full fish feeding trials that can take months to complete. In addition to the primary GALT culture cells, the two rainbow cell lines RTS11 and RTgutGC which are from macrophage and gut epithelial cells, respectively. The cells were stimulated with a variety of pathogen associated molecular patterns (PAMPs) (PHA and Poly I:C) and recombinant rainbow trout IL-1β (rIL-1β), a proinflammatory cytokine, additionally two forms of β-glucan, a prebiotic commonly used aquafeeds were used as stimulants. From this, the suitability of cell models as a health screen for functional feeds was assessed. GALT leucocytes were deemed most effective to act as a health screen over the 4hr time point demonstrating responses to Poly I:C, PHA, and rIL-1β. RTS11 and RTgutGC also responded to the stimulants but did not give a strong T-cell response, most likely reflecting the nature of the cell type as opposed to the mixed cell populations from the primary GALT cell cultures. When stimulated with both forms of β-glucan, GALT leucocytes demonstrated a strong proinflammatory and T-cell response.

Catch of the Day: New Serum Amyloid A (SAA) Antibody Is a Valuable Tool to Study Fish Health in Salmonids

“…There were high levels of endogenous rainbow trout SAA detected in the expected ~12 kDa size range in IL-1β-stimulated RTS-11 cell supernatants at between 24 and 72 h post-stimulation, with no detectable SAA in control cell supernatants ( Figure 6 A,B). Our reported high SAA protein expression following IL-1β stimulation is in line with previous reports on the transcriptomic level [ 34 , 35 ].…”

“…IL-1β is known to induce SAA transcription in rainbow trout cells [ 34 , 35 ]. However, SAA protein levels have not been studied in any salmonid cell lines.…”

“…The rainbow trout monocyte/macrophage-like RTS-11 cell line has been widely used to study immune gene expression [ 44 , 45 ], including SAA transcripts [ 34 , 35 ]. Our study is the first to characterise secreted SAA protein in a salmonid cell line.…”

Deciphering the Immunostimulatory Effects of β-Glucan on a Rainbow Trout (Oncorhynchus mykiss) Macrophage-like Cell Line (RTS11) by Whole Transcriptome Analysis

“…This study further highlights the immune modulatory effect of β-glucans in rainbow trout by demonstrating the modulation of the innate immune system through the direct interaction with macrophage-like cells. This work expands on previous studies where targeted gene expression has been carried out by limited gene sets using real-time PCR in RTS11 cells [10,12]. Here, we clearly demonstrate that β-glucans cause the distinct immunomodulation of innate immune pathways relating to the proinflammatory response, most likely by binding to cellular receptors and resulting in multiple signalling pathways, rather than changes in the cellular metabolism.…”

“…β-glucans are complex polysaccharides, made up of repeating units of glucose linked by glycosidic bonds, and are sourced from the cell walls of plants, yeast, or fungi. β-glucan’s immunostimulatory properties are well characterised in fish, with β-glucan supplementation causing the upregulation of proinflammatory genes such as IL-1β, TNFα, and COX-2 [ 7 , 10 , 11 , 12 ]. However, to date, there is little information regarding the mechanisms of action of these important molecules in fish [ 13 , 14 ].…”