Allergenic molecules
Major allergens such as Jun a 1, Jun a 2, Jun a 3 and Jun a 7 have been identified in various immunoblot analyses, which showed IgE binding to these proteins and listed in the WHO/IUIS database (13).
Allergen |
Biochemical name |
Molecular weight |
Allergenicity |
---|
Jun a 1 |
Pectate lyase |
43 |
- Previously known as Jun s 1
- Major allergen (22).
- IgE reactivity was observed in 71.4% of 14 sera from mountain juniper allergic patients as seen on immunoblot analysis (1).
|
Jun a 2 |
Polygalacturonase |
43 |
- IgE reactivity was observed in all 8 sera of Japanese cypress allergic patients and one mountain juniper allergic patient as seen on immunoblot analysis (23).
|
Jun a 3 |
Thaumatin-like protein |
30 |
- PR-5 protein (16)
- IgE reactivity was observed in 42.9% and 33.3% of 14 sera from mountain juniper allergic patients and 36 sera from Japanese cedar sensitive patients, respectively, as seen on ELISA immunoblots (16).
|
Jun a 7 |
Gibberellin-regulated protein |
7 |
- High IgE levels were detected in 16 sera of peach allergic and cypress pollen sensitized individuals (24).
|
Allergen |
Biochemical name |
Molecular weight |
Allergenicity |
---|
kDa: kilodaltons, IgE: Immunoglobulin E, PR: Pathogenesis-related, ELISA: Enzyme Linked Immunosorbent Assay
Biomarkers of severity
Studies have identified Jun a 1 as the major marker allergen for mountain juniper allergy (22).
Cross-reactivity
Pollen-pollen cross-reactivity
Proteins from the pollen of 12 species of Cupressaceae, including mountain juniper and one Taxodiaceae member Japanese cedar, have exhibited extensive cross-reactivity. Jun a 1, a major allergen of mountain juniper, was responsible for the cross-reactivity with other allergens from Cupressaceae family (40 to 42 kDa), and Japanese cedar (46 kDa). Some of the species reported to be cross-reactive with mountain juniper include Port Orford Cypress (Chamaecyparis lawsonia), red cedar (J. virginiana), Italian cypress (C. sempervirens), Arizona cypress (C. arizonica), one-seed juniper (J. monosperma), redberry juniper (J. pinchotti) and other species of Juniperus (10, 25).
Jun a 1, a major allergen (pectate lyase) of mountain juniper (mountain cedar) was found highly cross-reactive with major allergens of Japanese cypress (Cha o 1), Japanese cedar (Cry j 1), and Arizona cypress (Cup a 1) (16, 20). This cross-reactivity may be attributed to homology (70%-95%) among the amino acid sequences of these proteins since they belong to the same family of tree species (24). A study has also reported high amino acid sequence similarity of 91% between Cup a 1 and Jun a 1 (26).
Further, Jun a 2 is also reported to be highly homologous to Cry j 2 (70.7 %) and Cha o 2 (82.0%), allergens of a Japanese cedar tree (Cryptomeria japonica) and Japanese cypress tree (Chamaecyparis obtuse) pollen respectively (23). Also, Cup s 3 from C. sempervirens species is revealed to have 95% sequence homology and strong cross-reactivity with Jun a 3 (PR-5 protein) (27). In addition, Jun a 7 was found to be 98% homologous to Cup s 7 (Cupressus sempervirens, Italian cypress) (24).
Pollen-food cross-reactivity
Jun a 1, Jun a 2 and Jun a 3 have been observed to have high homology with allergens in fruits. OAS was found in mountain juniper allergic patients due to cross-reactivity with tomato, banana, melon mix and apple. Jun a 2 (Polygalacturonase) was reported to be responsible for cross-reactivity with tomato allergen (Sola 14) (18).
Further, Jun a 3, a thaumatin-like pathogenesis-related protein (PR-5), is closely related to a thaumatin-like protein in bananas (28). Cross-reactivity is expected between Jun a 3 and thaumatin-like proteins in cherry (Pru av 2), apple (Mal d 2), and paprika or bell pepper (Cap a 1) and therefore, sensitization to Jun a 3 may induce symptoms of OAS in mountain juniper sensitized patients (Jun a 3) (29).
Additionally, osmotin (PR-5, thaumatin-like protein) homology has been reported in tomato (Lyc e NP24; 91.87%), kiwi fruit (Act c 2; 75%), cypress (Cup s 3; 61.3%), bell pepper, (Cap a 1; 88.16%), apple (Mal d 2; 40.65%) and mountain juniper (Jun a 3; 63.79%). This sequence homology may cause cross-reactivity between these species (30).
Further, Jun a 7 exhibiting 67% of sequence homology to Pru p 7 (peach) has also been reported in a study (24).
Pollen-Fungal Spores cross-reactivity
Fungi homologous allergens have been reported in allergens from pollen origin such as Jun a 2, Tri a 25 (Wheat), Bet v 7 (Birch), Cry j 2, Pla a 2 (London Plane tree), Hor v 4 (Barley).
This speculates the probability of cross-sensitization between fungi and pollen (31).