ß-glucans: Innate immune system response in shrimp and fish

For a long time, the most common method for dealing with the occurrence of bacterial infections in aquaculture was the administration of antibiotics. However, aquaculture faces serious problems due to various adverse effects of these drugs such as accumulation in the tissue and resistance in environmental microbial flora. On the other hand, to use antibiotic or vaccine for fish is expensive and in many farms unavailable (Yousefian and Amiri, 2009), however, the use of substances or nutrients incorporated into the feed to improve the survival rate, disease resistance and growth of fish and shrimp have been used more and more and successfully.

Fish, similar to mammals, have the innate and the adaptive immune systems, with the innate being responsible for primary responses, where the response is fast, non-specific, and with no memory against recontaminations, and the adaptive system is responsible for specific responses, in other words, intense response with specific antibodies for each pathogen. However, shrimp are apparently entirely dependent on a non-specific immune mechanism to resist infections (Hertrampf and Mishra, 2006).

The most well-known cells of the innate immune system are the macrophages, neutrophils, dendritic cells, and natural killer cells (Sharma, 2003). Toll-like receptors, located on the surface of immunological cells, recognize microbial patterns and induce an immediate innate immune response. After this activation and phagocytosis, the phagocyte presents a processed fragment of the pathogen to the adaptive immune system and stimulates an anti-pathogen response. Therefore the phagocytes are called antigen-presenting cells. The recognition of pathogens by the innate immune system triggers immediate innate defenses and activation of the adaptive immune response (Lee & Iwasaki, 2007).

ImmunoWall® from ICC Brazil is a product composed of cell walls from Saccharomyces cerevisiae yeast, originating from sugarcane fermentation process for ethanol production, and contains around 35% of β-glucans and 20% of mannan oligosaccharides (MOS). β-glucans are known as immune system modulators or stimulants because when they come in contact with the phagocytes, which recognize the β-1,3 and 1,6 bindings (Petravic-Tominac et al., 2010), phagocytes are stimulated and produce some cytokines, which start a chain reaction inducing an immunomodulation and improving the response capacity of the innate immune system.

This type of response is especially important in animals in an initial growth phase, reproductive phase, stress periods, and during environmental challenges by acting as a prophylactic agent to increase disease resistance and minimize further damage (such as a drop in performance or high mortality rates). Intensive animal production is a highly challenging environment. Thus the strengthening of the immunological system can be one of the keys toward greater productivity.

ImmunoWall® also contains MOS, known for its capacity for agglutination of pathogens with type 1 fimbria, such as diverse Gram-negative strains. MOS offers a binding site for pathogens, preventing the colonization of the intestinal epithelium, and these agglutinated bacteria are excreted together with the indigestible part of the fiber and other fecal matter.

Several studies have been published about benefits of ImmunoWall® supplementation in aquaculture.  Ebrahimi et al. (2011) studying common carp fingerlings (Cyprinus carpio) infected with Aeromonas hydrophila found a significant increase in survival rates number of leucocytes and improvement in feed conversion ratio results in groups fed diets with ImmunoWall® from 1 to 2.5%. Ebrahimi (2010) reported a decrease in total bacteria counts in the intestine and an increase in survival rate and fed conversion ratio improvement of Rutilus frisii Kutum fingerlings fed with ImmunoWall from 0.5 to 2.5%.  Karimzadeh et al. (2013) studying Rutilus kutum larvae found an improvement in survival rate, final body weight, and feed conversion ratio, as well as a decrease in total bacteria counts in the intestine at 0.5%  ImmunoWall® supplementation.

Others research has been conducted to prove the beneficial effects of ImmunoWall® in shrimp production. Jintasataporn et al. (2016) showed an improvement in survival rates of Litopeneaus vannamei infected with V. harveyi and in some immunity parameters under disease challenge conditions by V. harveyi or V. parahemolyticus (cause of Early Mortality Syndrome) fed a diet with 1% ImmunoWall®. Another trial conducted by Jintasataporn (2014 - unpublished data) also studied the effects of ImmunoWall® on the response of Litopeneaus vannamei infected with V. parahemolyticus, and the results showed an improvement in disease resistance against virulent bacteria (in immunity parameters and survival rates), mainly under high salinity conditions.

To enhance and modulate the innate immune system may be one of the strategies to combat contamination, reduce mortality, and improve productivity. If dietary yeast cell walls are supplied in advance to the fish or shrimps, the immune system will be modulated and alert to any infections or contaminations. The action of yeast β-glucan is on the innate immune system, in other words, the first immune response to pathogen contamination, avoiding a greater expenditure of energy to mobilize the adaptive immune system (fish), or decreases in production, or high rates of mortality (fish and shrimp).

 

Ebrahimi, G. (2010) Effects of prebiotic supplementation on survival, growth performance and feed utilization of Kutum, Rutilus frisii (Kamenskii), fingerlings. Research Journal of Animal Science, 4 (6): 125-129.

Ebrahimi, G., Ouraji, H., Khalesi, M.K., Sudagar, M., Barari, A., Zarei Dangesaraki, M. and Jani Khalili, K.H. (2012) Effects of a prebiotic, Immunogen, on feed utilization, body composition, immunity and resistance to Aeromonas hydrophila infection in the common carp Cyprinus carpio (Linnaeus) fingerlings. Journal of Animal Physiology and Animal Nutrition, 96: 591–599.

Hertrampf, J.W. and Mishra, S.K. (2006). Benefits of nucleotides in shrimp farming. Feed Tech. Vol. 10.9, pp. 27-30. www.AllAboutFeed.net

Jintasataporn, O., Bonato, M.A., Santos, G.D. and Hooge, D.M. (2016) Saccharomyces cerevisiae cell wall supplementation on growth performance and immunity status of white shrimp (Litopeneaus vannamei). Journal of Modern Agricultural Science and Technology. Accepted for publication.

Karimzadeh, S., Amirkolaie, A.K., Molla, A.E. (2013) Effects of Different Levels of Immunogen on Growth Performance, Intestinal Bacteria Colonization and Survival Rate in Rutilus kutum Larvae. World Journal of Fish and Marine Sciences 5 (6): 664-669.

Lee, H. K., A. (2007) Iwasaki. Innate control of adaptive immunity: dendritic cells and beyond. Semin. Immunol., n. 19, p.48-55.