Allergenic molecules
Banana contains a large number of different potential allergens such as pathogenesis related (PR) proteins: PR5 thaumatin-like, PR2 endo-β-1,3-glucanase, PR8 class III chitinase in addition to jacalin-related lectin (24).
To date, 6 allergenic proteins from Musa acuminata has been listed officially in the database of the World Health Organization/International Union of Immunological Studies (WHO/IUIS) Allergen Nomenclature Sub-Committee (25).
The table below provides detailed information on the allergenic proteins identified by WHO/IUIS (25):
Allergen |
Biochemical Name |
Molecular Weight (kDa) |
Allergenicity |
---|
Mus a 1 |
Profilin |
15 |
- Specific IgE-binding on immunoblots was found in 44% (7/16 sera) of suspected banana allergic patients (1, 9).
- Sensitive to heat and gastric digestion (1).
- High cross-reactivity with Bet v 2 (birch profilin) and Hev b 8 (latex profilin) (1, 9).
|
Mus a 2 |
Class I chintinase |
33 |
- Major banana allergen (1).
- Two identified isoforms with hevein-like domain (1, 26).
- The two purified isoforms (32 kDa and 34 kDa) gave a positive SPT in more than 50% of banana allergic patients (1, 26).
|
Mus a 3 |
Non-specific lipid transfer protein type 1 (nsLTP1) |
9 |
- PR-14 family of proteins (1).
- IgE immunodetection seen in 20% of 36 sera of banana allergic patients (1, 16).
|
Mus a 4 |
Thaumatin-like protein |
20 |
- Major allergen in pediatric patients (16).
- PR-5 family of proteins and is non-glycosylated (1).
- Specific IgE reactivity seen in 72% of 51 sera and positive SPT in 50% of 12 sera of banana-allergic children (16).
|
Mus a 5 |
Beta-1,3-glucanase |
30 |
- Specific IgE reactivity was seen in 84% of 51 sera while positive SPT in only 20% of 12 sera of banana-allergic children (16).
- Reactivity on ELISA immunoblots was found in 74% of 23 banana-sensitized patients’ sera (27).
|
Mus a 6 |
Ascorbate peroxidase |
27 |
- Most recent reported banana allergen.
- IgE reactivity was seen in 10 of 11 and 7 of 11 sera of banana allergic patients on immunoblots to natural and recombinant protein respectively (1, 25)
|
Allergen |
Biochemical Name |
Molecular Weight (kDa) |
Allergenicity |
---|
Biomarkers of severity
Mus a 5 can be used for component-based diagnosis of banana allergy in patients with negative IgE test with banana extract as reported by a study in 23 banana-allergic patients (27).
Cross-reactivity
Banana allergy has been correlated with latex and/or pollen suggesting that banana is responsible for latex-fruit, pollen-fruit, and latex-pollen-fruit syndrome (6).
Latex-food syndrome is observed in about half of the latex allergic patients and linked to various fruits and vegetables including banana, kiwi, avocado, peach, pineapple, chestnut, tomato, potato, and pepper (16, 29). Individuals developing ‘latex-fruit’ syndrome (commonly seen in health care workers who frequently wear natural rubber latex gloves) are initially sensitized to latex and later become allergic to food due to cross-reacting IgE against allergenic proteins (9, 30). This latex sensitization results in allergic reactions like urticaria, GI, and in severe cases, anaphylaxis or even loss of consciousness (1).
Cross-reactivity of banana with pollens of different trees and weeds including palm, birch, plane tree, olive, ragweed, and hazelnut has also been observed (1, 6, 8, 28, 31, 32). It can lead to the development of banana allergic reactions, such as oral allergy symptoms like itching and swelling of the mouth and throat (1).
The possible cross-reactive molecules responsible for latex-pollen-fruit syndrome are the gluconases such as Hev b 2 from rubber tree latex (Hevea brasilianis), the Mus a 5 from banana (M. acuminata), and Ole e 9 from olive pollen. These molecules showed high sequence homology and have common IgE epitopes (1). Besides, cross reactivity also occurs between profilin of banana (Mus xp 1, M. parasiadica), and profilins of rubber tree latex (Hev b 8), olive pollen (Ole e 2), and fruits like kiwi (Act d 9), and ananas (Ana c1) (28). Furthermore, there is an association between ragweed-melon-banana and the probable cross reacting molecules are either profilins or LTPs, such as Mus xp 1 (profilin) of banana, Amb a 6 (LTP), Amb a 8 (profilin) of ragweed (Ambrosia artemisilifolia), Cit la 2 of watermelon (Citrullus lanatus), Cuc m 2 of muskmelon/cantaloupe (Cucumis melo), Cuc p 2 of zucchini (Cucurbita pepo), and Cuc s 2 of cucumber (Cucumis sativus) (28).
Additionally, the cross-reactivity between banana and fruits like peach and pineapple was studied and it was observed that more than 75% of 36 banana allergic patients recognized the major allergen of peach (Pru p 3, nsLTP) on IgE immunoblots in addition to pineapple bromelain (a marker of cross-reactive carbohydrate determinants, CCD) (16).