The effect of ß-1,3-glucan derived from Euglena gracilis (Algamune™) on the innate immunological responses of Nile tilapia (Oreochromis niloticus L.)

Authors: YAMAMOTO, FERNANDO - Texas A&M University; SUTILI, FERNANDO - Texas A&M University; Hume, Michael; GATLIN, DELBERT - Texas A&M University

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2018
Publication Date: 7/27/2018
Citation: Yamamoto, F.Y., Sutili, F.J., Hume, M.E., Gatlin III, D.M. 2018. The effect of ß-1,3-glucan derived from Euglena gracilis (Algamune™) on the innate immunological responses of Nile tilapia (Oreochromis niloticus L.). Journal of Fish Diseases. 41(10):1579-1588. https://doi.org/10.1111/jfd.12871.
DOI: https://doi.org/10.1111/jfd.12871

Interpretive Summary: Algamune is a commercial feed additive derived from the single cell organism Euglena gracilis, providing a rich source of the immune system-enhancing long chain sugar ß-glucan. Isolated white blood cells from Nile tilapia fish were incubated with Algamune and a purified form of ß-glucan in order to gauge their ability to elicit immune responses. Immune responses in white blood cells isolated from Nile tilapia increased as levels of Algamune were increased. Next, fish were given Algamune in the feed over 3 weeks, after which the fish were sampled for white blood cell immune responses. Other fish were injected with a disease-causing bacterium and given Algamune in the feed. White blood cell immune response was greatly increased in fish fed Algamune when compared to fish that were not fed Algamune. Fish given feed containing Algamune had the lowest mortality. In conclusion, Algamune enhanced immune responses in tilapia and protection when exposed to a disease-causing bacterium. This supplement may potentially increase tilapia aquaculture market value by decreasing mortality. These results are of interest to aquaculture researchers and producers seeking alternatives to traditional antibiotics to reduce disease, mortality, and to enhance aquaculture production.

Technical Abstract: Algamune™ is a commercial feed additive derived from Euglena gracilis, providing a rich source of the ß-1,3-glucan paramylon. Isolated kidney phagocytes of Nile tilapia were incubated with graded doses (0, 8, 16, 32, 64, and 128 µg mL-1) of Algamune™ and purified ß-1,3-glucan paramylon to gauge their ability to elicit the production of reactive oxygen species. A linear response was observed for extracellular superoxide anion for both sources and Algamune™ for intracellular superoxide anion. After corroborating the immunostimulant properties ex vivo, a feeding trial was conducted to evaluate the dietary supplementation of Algamune™ (0, 100, 200, 400 and 800 mg kg-1 of diet) for Nile tilapia. Fish were fed twice daily over 3 weeks, after which fish were sampled for blood and head kidney phagocytes. The remaining fish were given a disease challenge with Streptococcus iniae. Macrophage extracellular superoxide anion production was significantly elevated in fish fed diets with 200 mg of Algamune™ kg-1 when compared to fish fed the basal diet. Even though the disease challenge did not show statistical differences due to dietary treatments, fish fed diets supplemented with 100 and 200 mg kg-1 of Algamune™ had the lowest numerical mortality values. In conclusion, Algamune™ enhanced some immune responses of tilapia both in ex vivo and in vivo. This supplement may potentially increase tilapia aquaculture market value by decreasing mortality.