It is estimated that food allergies affect nearly 8% of children and 5% of adults worldwide. Previous studies have found that certain seaweed varieties contain polysaccharides with anti-asthmatic and anti-allergy effects. Scientists reporting in the ACS’ Journal of Agricultural and Food Chemistry have now found that a commercial variety of red algae, Gracilaria lemaneiformis (GLSP), may also counteract food allergies. Shellfish allergy in the Asia Pacific region ranks amongst the highest in the world. In China, 16.7% of the rural population is sensitised to shellfish, with tropomyosin (TM) being the major allergen.
To investigate the anti-food allergic activity of GLSP, Liu et al. isolated polysaccharides from red algae. Twenty-four TM sensitised mice were randomly assigned to four groups: a PBS group, a TM group, a GLSP-preventative group, and a GLSP treatment group.
All mice were fed 10 mg TM in 200 µL of phosphate-buffered saline (PBS) every other day from day 28 to 38. The GLSP-preventive group mice were also fed GLSP (5mg/mouse in 200 µL of PBS) daily from day 27, the day before being fed TM, to day 40. The GLSP treatment group had already received 3 doses of TM before they were given GLSP daily (5mg/mouse in 200 µL of PBS) from day 33 to day 40. The PBS group, the negative control group, only received PBS during the study.
An hour after each intake of TM, the scientists reported any anaphylactic symptoms and episodes of diarrhoea. After the final intake of TM, temperature was recorded and histamine and mMCP-1 levels in serum measured. On day 41 the mice were sacrificed and TM-specific immunoglobulin E (IgE- antibodies), IgG1 and IgG2a (IgE subclasses) were measured. Mesenteric lymph node cells were isolated from the mice and analysed for cytokines.
The scientists report that in both the GLSP-preventative and GLSP-treatment groups, daily doses of GLSP moderately decreased the scores of the anaphylactic response and diarrhoea for 1 hr after the third-sixth intake of TM.
The daily administration of GLSP in the GLSP-preventative group was reported to significantly reduce TM-specific IgE and IgG1 serum levels but not anti-TM IgG2a. GLSP was shown to diminish the increase of the concentration of serum histamine concentration and mMCP-1 after the sixth intake of TM in the GLSP-preventative group. Liu et al. report that these findings suggest that “the anti-food allergic symptoms activity of GLSP in the GLSP-preventative group was more pronounced than that in the GLSP-treatment group.”
Compared to the TM mice, the GLSP suppressed TH2 cell polarisation, and promoted the function of regulatory T (Treg) cells. Treg cells are a subpopulation of T cells which modulate the immune system, maintain tolerance to self-antigens, and abrogate autoimmune disease. The authors indicate that this finding suggests that the anti-allergic activity of GLSP in TM-sensitised mice could be through immunosuppression. GLSP intake was also was found to inhibit the function of RBL-2H3 cells, and inhibit the activation of KU812 (cells which release histamine).
In conclusion Liu et al. state that “GLSP may provide insight into the preventative of food allergy induced-anaphylaxis and may be used as a functional food component to prevent food allergic diseases.”
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