Co-sensitization to different legumes common but often not clinically relevant

Key takeaways:

• Co-sensitization rates between different types of legumes ranged from 36.7% to 100%.
• Co-allergies for other legumes were not common among patients with peanut and soybean allergies.

Co-sensitization between legumes in different legume-allergic patients was frequent, but large proportions of these co-sensitizations were not clinically relevant, according to a study published in Frontiers in Allergy.

But as legumes become more popular as alternative protein sources, providers should still mind their potential for increased risks for new sensitizations and allergies, Thuy-My Le, MD, PhD, dermatologist, department of dermatology/allergology, University Medical Center Utrecht, and colleagues wrote.

“Both protein consumption and the world’s population are increasing, which leads to an urgent demand for sustainable protein sources. An increase in the consumption of legumes may elicit complaints in already legume allergic patients,” Le said in a press release.

“Therefore, we investigated how often sensitization and allergy to different legumes occurs in these patients,” Le said.

Co-sensitization rates

The researchers examined adults who visited the allergology outpatient clinic at University Medical Center Utrecht for sensitization to 10 different legumes, including peanut, soybean, green pea, chickpea, blue/white lupine, black/green lentil, and fava/white bean.

These patients were categorized into six legume-allergic groups, including peanut (n = 30), soybean (n = 30), green pea (n = 30), lupine (n = 30), lentil (n = 17) and bean (n = 9). The researchers found co-sensitization for each tested legume in all six legume-allergic patient groups.

For example, the bean-allergic patient group had the highest co-sensitization rates, ranging from 77.8% for white bean to 100% for seven of the other tested legumes. The groups with soybean and peanut allergies had co-sensitization rates ranging from 36.7% to 76.7%. Patients with green pea, lupine, lentil or bean allergies were probably also sensitized to other legumes, ranging from 58.8% to 100%.

The researchers noted that degrees of mono-sensitization were limited among the patients who were allergic to soybean (16.7%), peanut (10%) and green pea (3.3%), but there was frequent co-sensitization for all 10 legumes in all the groups of patients allergic to legumes, including peanut (23.3%), soybean (33.3%), green pea (50%), lupine (43.3%), lentil (41.2%) and bean (66.7%).

Also, the researchers said they did not see co-sensitization to fewer than six legumes for patients with allergies to lupine, lentil and bean, compared with the peanut, soybean and green pea allergy groups.

Patients with lupine, lentil and bean allergies, the researchers suggested, were therefore always sensitized to other legumes as well, but patients with peanut and soybean allergies were not.

The researchers further said they observed highly frequent co-sensitization between the 7S and 11S globulin fractions of the 10 legumes, with IgE binding intensity profiles resembling sensitization profiles. Generally, the researchers continued, the frequency of sensitization for the 2S albumin fraction was low, except for peanut.

Similarly, the researchers said the prevalence of co-sensitization for individual 7S and 11S globulins was high among the patients with soybean, green pea, lupine, lentil and bean allergies, which was consistent with high co-sensitization between the 7S and 11S globulin fractions of the various legumes. Co-sensitization between 2S albumins was seen as well, but it was not as prevalent, the researchers continued.

Co-allergy rates

Patients with peanut and soybean allergies had co-allergies for green pea, lupine, lentil and bean 16.7% or less of the time. The most common co-allergy for patients with peanut allergy was soybean (20%), and for patients with soybean allergy it was peanut (63.3%).

Co-allergies for peanut and soybean were also high for patients with green pea, lupine, lentil and bean allergies. These patients had a co-allergy for peanut between 64.7% and 77.8% of the time and a co-allergy for soybean between 50% and 64.7% of the time.

Bean was the least common co-allergy, affecting between 0% and 35.3% patients in each group. Patients with bean allergies, however, had the most frequent co-allergies, ranging from 55.6% to 77.8%.

Co-allergy was less prevalent than co-sensitization across all legume-allergic groups, the researchers said, indicating that a considerable proportion of these co-sensitizations may not be clinically relevant.

“We showed that a large number of patients produced antibodies against more than one legume,” Kitty Verhoeckx, assistant professor, department of dermatology/allergology, University Medical Center Utrecht, said in the press release. “However, clinical data showed that only a small part of these patients had actual symptoms.”

Risks for a peanut co-allergy among patients with soybean, green pea, lupine and lentil allergies were higher with sensitization for the 7S/11S globulin or the 2S albumin fraction from peanut compared with patients without these sensitizations, with odds ratios ranging from 12.89 (95% CI, 1.97-84.12) to 94.71 (95% CI, 4.39-2,041.8).

Patients with peanut or soybean allergies who were sensitized to the 2S albumin fraction from lupine similarly had significantly higher risks for lupine co-allergy compared with patients who did not have these sensitizations, the researchers continued, with odds ratios of 11.18 (95% CI, 1.41-88.95) for both peanut and soybean.

But most of these odds ratios were not statistically significant, the researchers clarified, so these co-sensitizations often were not associated with clinically relevant co-allergy.

In almost all patient groups with legume allergies, the researchers said, there was an association between co-sensitization for 7S/11S globulin or 2S albumin fractions from peanut and clinically relevant co-allergy for peanut, but co-sensitization for 7S/11S or 2S albumin fractions for other legumes was clinically less relevant.

The researchers additionally attributed some inhibition of IgE binding to respective lentil fractions to pre-incubation with peanut 2S or 7S/11S fractions during inhibition assays, but they also noted a lack of inhibition or limited inhibition of IgE binding to 2S albumin and 7S/11S peanut fractions upon pre-incubation with the respective lentil fractions.

To a limited extent, the researchers said, sensitization for peanut fractions was responsible for co-sensitization for lentil fractions, but primary sensitization for lentil fractions did not cause co-sensitization between lentil and peanut.

There also was 79% to 90% inhibition of IgE binding in patients with lentil and pea allergies due to pre-incubation with lentil and green pea 2S albumin or 7S/11S fractions, indicating clinically relevant co-sensitization between green pea and lentil in patients with allergies to both green pea and lentil due to cross-reactivity, the researchers said.

Conclusions

“Legumes are an attractive sustainable protein source, but allergic reactions in the already legume-allergic population cannot be excluded as antibodies in the blood of legume-allergic patients frequently react to different legumes,” Le said.

“However, this reaction does not always lead to a clinically relevant food allergy. Introduction of novel foods into the market should be accompanied by appropriate assessment of the risk of developing (new) food allergies,” Le said.

Overall, the researchers said that co-sensitization between legumes in groups of patients with different legume allergies, but many of these co-sensitizations were not clinically relevant. But since cross-reactive allergic reactions and co-allergies still occurred, the researchers continued, future studies with larger patient groups are needed to confirm these findings.

Reference:

• Common meat-free proteins may trigger soybean and peanut allergies in some people. https://blog.frontiersin.org/2023/03/16/common-meat-free-proteins-may-trigger-soybean-and-peanut-allergies-in-some-people/. Published March 16, 2023. Accessed April 10, 2023.