Mountain juniper Pollen
Summary
Mountain juniper, also known as mountain cedar, is an above-average shrub or an undersized tree, which can attain a height of up to 15 m. It is known to have a high pollen-producing capability. The pollination period of this tree falls from December to February. Native to North America, this tree is prevalent in countries like the US and Mexico. Exposure to mountain juniper pollen may induce symptoms such as asthma, allergic rhinitis, allergic rhino-conjunctivitis, and oral allergy syndrome (OAS) in sensitive patients. Jun a 1, Jun a 2, Jun a 3 and Jun a 7 potential allergens have been identified in the IUIS database. Allergen immunotherapy with mountain juniper pollen has been reported to have a significant improvement in patients with allergy symptoms. Mountain juniper has exhibited cross-reactivity with related species like Arizona cypress, Japanese cypress, Port Orford cedar, red cedar, western red cedar, western juniper, Pfitzer juniper etc. and with unrelated species like peach, tomato, apple, kiwi etc.
Epidemiology
Worldwide distribution
Cupressaceae family pollen is recognized as one of the 12 most abundant aeroallergen pollens in Europe. Further, Mountain juniper pollen is highly allergenic and is considered as one of the crucial reasons for allergenic rhinitis (hay fever) in Texas and North America.
Mountain juniper pollinosis is a widespread clinical allergic condition found in Mexico and Texas, US. In contrast, eastern red cedar (Juniperus virginiana) and white cedar (Thuja occidentalis) from the same family Cupressaceae are common allergenic plants in western New York, US. Studies have also identified air pollutants as a risk factor for Cupressaceae pollen and its correlation with the allergy arising from the exposure to the pollen of this family.
In a study conducted in Texas, 34% (80/234) of the patients were mono-sensitized to mountain juniper, and 66% (154/234) were poly-sensitized to other aeroallergens in addition to mountain juniper. Asthma and atopic dermatitis were the commonly observed allergic reactions among the mono-sensitized and polysensitized group.
An Iranian study conducted on 306 patients suffering from allergic rhinitis reported 17.3% of the patients exhibiting positive skin prick test (SPT) towards mountain juniper.
Route Of Exposure
Main
Pollens from mountain juniper can enter the respiratory tract through inhalation.
Clinical Relevance
Mountain juniper pollen allergenicity causes severe seasonal allergic diseases in several parts of the US and northern regions of Mexico. Allergic rhinitis and asthma, occurring due to aeroallergens, particularly mountain juniper, are among the primary reasons for increased morbidity, productivity loss and increased burden on healthcare expenditure. Symptoms like allergic rhinitis and conjunctivitis may cause impairment of sleep, decrease in quality of life and decline in cognitive function in allergic individuals.
Allergic rhinitis (AR) and allergic rhino-conjunctivitis (ARC)
In a US-based study on 234 allergic patients, 34% (n=80) reported mono-sensitization to mountain juniper. Over one-third of these mono-sensitized patients depicted the development of allergic rhinitis and conjunctivitis as their only allergic symptoms.
Further, in another study in Texas (US), 21 out of 26 patients with a history of ARC due to mountain juniper (mountain cedar) were confirmed to have ARC due to mountain juniper (mountain cedar) based on subcutaneous or intradermal testing.
Asthma
In a US-based study, 11% of patients with mountain juniper mono-sensitization and 39% of patients with poly-sensitization to several aeroallergens, including mountain juniper, had asthma or atopic dermatitis. Further, in another study in Texas (US), only 4 patients out of 21 allergic patients due to mountain juniper (mountain cedar) had a history of stable asthma.
Other diseases
Oral Syndrome allergy (OAS)
A study on 28 mountain juniper-sensitized individuals with a suspected food allergy reported cross-reactive IgE binding between mountain juniper pollen and fruit allergen. OAS was observed to have manifested in 53.5% (15/28) of these individuals. The individuals with OAS were found positive towards tomato (11 patients), banana (6 patients) and apple (1 patient) based on SPT. Also, patients with OAS showed stronger in-vitro and cutaneous reactivity to mountain juniper pollen. Jun a 2 was reported as one of the potential allergens to induce OAS due to tomato pollen hypersensitivity. Additionally, it was suggested that co-relation between mountain juniper sensitivity and tomato, banana, and apple sensitivity should be considered during diagnosis.
Prevention And Therapy
Allergen immunotherapy
A randomized study was conducted in Texas (US) on 21 patients with allergic rhino-conjunctivitis (induced by exposure to mountain juniper pollen) to analyze intra-lymphatic immunotherapy in mountain juniper allergic patients. They received intra-lymphatic injections of allergenic extract containing mountain juniper pollen or placebo every three months prior to mountain juniper pollen season. Patients receiving immunotherapy reported having a significant improvement in allergy symptoms and their medication usage, compared to placebo (p < 0.001).
Prevention strategies
Avoidance
One of the preventive measures to be taken is to cut down the amount of pollen entering the respiratory system. During pollen season, allergic patients are suggested to stay indoors or wear masks outdoors to keep away from pollen allergens. In worse situations, patients may be suggested to move to a non-pollen area.
Other measures like removing all diseased trees from surrounding areas as they produce 2 to 3 times more pollens than the healthy ones; trimming windbreaks during autumn season to remove the male cones, can help.
One of the important aspects of pollen-related food allergy management is the detection and avoidance of cross-reactive allergy-related food products. Patients may be advised to avoid raw and processed fruits and vegetables from the diet.
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.
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). 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. A study has also reported high amino acid sequence similarity of 91% between Cup a 1 and Jun a 1.
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. 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). In addition, Jun a 7 was found to be 98% homologous to Cup s 7 (Cupressus sempervirens, Italian cypress).
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).
Further, Jun a 3, a thaumatin-like pathogenesis-related protein (PR-5), is closely related to a thaumatin-like protein in bananas. 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).
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.
Further, Jun a 7 exhibiting 67% of sequence homology to Pru p 7 (peach) has also been reported in a study.
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.
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