A case of late-onset anaphylaxis to fermented soybeans (natto)

Scallop aquaculture has a potential risk of natto-induced hypersensitivity reactions in a local area of northern Japan

BACKGROUND

Fermented soybean (natto)-induced hypersensitivity reactions (natto allergy) are rare and can result in late-onset anaphylaxis. The allergen in natto is considered to be poly-γ-glutamic acid (PGA), and marine sports are a risk factor for natto allergy due to epicutaneous sensitization to PGA from cnidarian stings. However, no research on natto allergy in fishery workers has yet been performed.

METHODS

We conducted a chart review of inpatients diagnosed with anaphylaxis due to natto at Hokkaido Prefectural Haboro Hospital between April 1, 2009, and August 31, 2020. We also administered self-report questionnaires about food hypersensitivity reactions to Japanese fishery workers, including members of the Kitarumoi Fishery Cooperative Association and part-time workers in this area, from February 1 to May 31, 2021.

RESULTS

We found six inpatients (29 inpatients with food-induced anaphylaxis among approximately 11,000 community-dwelling residents) with late-onset anaphylaxis due to natto; all were involved in scallop aquaculture. The questionnaires revealed that 27 participants had natto allergy. We divided the fishery workers into a scallop aquaculture (Scallop) group (n = 211) and other fishery group (n = 106). The Scallop group was significantly associated with natto allergy after adjustments for confounders (OR: 5.73, 95% CI: 1.46-22.56) by logistic regression analysis. In the Scallop group, older age, experience in repairing nets, and a longer length of work experience were significantly related to participants with natto allergy (n = 23), but not participants without natto allergy (n = 181).

CONCLUSIONS

Our results indicated an association between scallop aquaculture and natto allergy.

Nattokinase, a subtilisin family serine protease, is a novel allergen contained in the traditional Japanese fermented food natto

BACKGROUND

Immediate allergy caused by natto, a popular Japanese food prepared by fermenting soybeans with Bacillus subtilis var. natto, has been reported. Polygamma glutamic acid (PGA) in the sticky substance around natto beans has been reported to be a causative allergen of natto allergy. However, some of our patients with natto allergy were negative for PGA in the skin prick test (SPT). The sticky substance of natto beans contains a subtilisin family serine protease, nattokinase, along with PGA. In this study, we aimed to examine the antigenicity of nattokinase in natto allergy.

METHODS

Eight patients, who developed symptoms after ingesting natto and positively reacted to natto (seven to the sticky substance in natto and one to the whole natto product) in their SPT, were enrolled in this study. To analyze IgE reactivity, we performed immunoblotting, ELISA, and SPT for natto (bean and sticky substance), and/or PGA, and/or nattokinase and/or cultured B. subtilis var. natto extract.

RESULTS

In the SPT, four cases each were PGA-positive and PGA-negative. Immunoblotting of the sera from PGA-negative patients showed a protein band at 30 kDa, which was identified as nattokinase. Three PGA-negative cases, but not three PGA-positive cases, showed a positive reaction to nattokinase in the SPT and had a history of atopic dermatitis. The ELISA for nattokinase revealed a positive reaction of PGA-negative cases and negative reaction of PGA-positive cases in the SPT.

CONCLUSIONS

We identified a subtilisin family serine protease, nattokinase, as a novel allergen in natto allergy patients unsensitized to PGA.

Surfing as a risk factor for sensitization to poly(γ-glutamic acid) in fermented soybeans, natto, allergy

BACKGROUND

Poly(γ-glutamic acid) (PGA) is an allergen in natto, fermented soybeans, which causes late-onset anaphylaxis. We hypothesized that jellyfish stings sensitize adults to PGA because a surfer had allergies to both natto and jellyfish, whose sting contains PGA. The aim of the study was to identify behavioral factors, such as marine sports, associated with PGA sensitization.

METHODS

Outpatients diagnosed with food allergies based on relevant clinical history, positive skin test and/or food challenge test answered a questionnaire during a regular visit in 2016.

RESULTS

Questionnaire data from 140 outpatients were analyzed. These patients were divided into two groups: natto allergy group (13 patients, M:F = 10:3, mean age 40.6 years) and non-natto allergy group (127 patients, M:F = 46:81, mean age 44.5 years). All patients with natto allergy had positive results in skin prick test and basophil activation test with PGA. Of these, 92.3% had a marine sport hobby, especially surfing (84.6%). PGA sensitization was independently associated with marine sports (odds ratio, 278.0, 95 percent confidence interval, 36.9-6315.9, p < 0.001) adjusted for male sex and sea bathing, but not with male sex or sea bathing. In addition, although there was no significant difference in the experience of marine sports between natto and non-natto allergy groups, the natto allergy group participated significantly more frequently in marine sports than the non-natto allergy group (p < 0.001). There was no significant difference between natto consumption amount and PGA sensitization.

CONCLUSIONS

Surfing is a risk factor for PGA sensitization in those with allergy to natto.