g10 Johnson grass

Allergens within Grass Pollens

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  • Latin name: Sorghum halepense
  • Family: Poaceae (Gramineae)
  • Subfamily: Panicoideae
  • Tribe: Andropogoneae
  • Common names: Johnson grass, Johnsongrass, Sorghum
  • Source material: Pollen
Synonyms: S. controversum, S. miliaceaum, Holcus halapensis, Holcus halepensis
 
Do not confuse this plant with its close relation, S. bicolor (Common Wild Sorghum).
 
A grass species producing pollen, which often induces hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution
Johnson grass is a robust perennial native to North Africa, South Asia, and southern Europe, in a range from 55°N to 45°S. It has been reported as a weed in 30 crops in 53 countries, and in all major agricultural areas in the world. Introduced to the United States around 1830 from Turkey, it occurs in most states and as far north as Ontario.
 
Johnson grass is a warm-season graminoid. It differs from other Sorghumspecies in being a perennial that spreads by vigorous, extensive rhizomes, which can be as much as 1cm in diameter and 2 m long. Stems are typically 0.5 to 1.5 m high, occasionally reaching heights of 3 to 3.5 m. Its purplish panicles are 10 to 50 cm long with sessile spikelets 4.5 to 5.5 mm long, and the numerous slender leaves are 10 to 50 cm long. The awned, ovoid seeds are brown.
 
Growth is very vigorous, and 2 or 3 crops of hay may be harvested in a season. The flowering times are highly variable, as they depend crucially on temperature. In the Mediterranean area, Johnson grass flowers between June and August. In other parts of Europe the season is from July to September. In the US, it usually flowers from May to July or in the extreme south from December to January. The flowers are hermaphrodite (have both male and female organs) and are pollinated by wind. Johnson grass recolonises by its large quantity of seed as well as by its creeping rhizomes.
 
Environment
Johnson grass grows in sandy and rugged soils. It is cultivated for livestock feeding around the Mediterranean. It can be found in cultivated beds but more often invades open or scrubby places such as irrigation ditches, waste and disturbed areas, roadsides, and crop fields; especially places subjected to unnatural frequent flooding. It often becomes a troublesome weed, difficult to eradicate.
 
Though Johnson grass is primarily a hay and pasture grass, humans eat the seed raw or cooked. It can be used whole in a similar manner to that of rice or millet, or it can be ground into a flour and used as a cereal in making bread, cakes, etc. In some places the root is used as a substitute for sarsaparilla. Johnson grass is used as a folk remedy.
 
Allergens
  • Sor h 1 (1)

Potential Cross-Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected, as well as to a certain degree among members of the family Poaceae. Cross-reactivity between Bahia grass (g17), Johnson grass (g10) and Maize pollen (g202), which are related through the sub-species Panicoideae, is likely. (2-3) 
 
This grass contains one of the Group 1 allergens, which are glycoprotein isoallergens shared by many species of grass (4). Group 1 allergens are highly homologous, but not all of the antigenic epitopes are crossreactive (5). For example, Group 1 allergens from 8 different clinically important grass pollens of the Pooideae (Rye grass, Canary grass, Meadow grass, Cocksfoot and Timothy), Chloridoideae (Bermuda grass) and Panicoideae (Johnson grass, Maize) were isolated, and IgE binding to an allergic human serum pool was conducted to determine the degree of antigenic and IgE-binding similarities. The highest IgE-binding similarity was observed between Cocksfoot and Rye grass (53%) and between Rye grass and Canary grass (43%). No IgE-binding similarity was observed between Maize and other grasses. The highest antigenic similarity was also observed between Rye grass and Cocksfoot grass (76%), and the lowest similarity between Maize (23%) and Bermuda (10%) (6). 
 
A study to explore common antigenic/allergenic components of 5 important grass pollens of India, a tropical country, was conducted. In India, to explore cross-reactivity, intradermal tests and specific sera IgE tests were performed with pollen extracts of Cenchrus (English Bunch grass), Cynodon (Bermuda grass), Imperata (Cottonwool grass), Pennisetum (Kikuyu), and Sorghum (Johnson grass) in patients with nasobronchial allergy. Among 133 patients, Cynodon extract elicited markedly positive skin reactivity in most patients, followed by Pennisetum, Imperata, Cenchrus, and Sorghum. ELISA inhibition experiments showed different degrees of cross-reactivity among the grass pollens studied (7).
 
On the basis of RAST inhibition tests, Johnson grass appeared to share allergenicity with both Northern grasses (Timothy, Meadow, Rye, Redtop, Meadow Fescue, and Sweet Vernal) and Bermuda grass (8).

Clinical Experience

IgE mediated reactions
Johnson grass pollen often induces asthma, allergic rhinitis and allergic conjunctivitis in sensitised individuals (7).
 
Farmers exposed to grain Sorghum and grain Sorghum dust were more likely to experience respiratory symptoms like cough or chest tightness, as well as an acute febrile illness, than were farmers exposed to other types of grain (9).
 
In Thailand, specific IgE tests with 14 selected local aeroallergens on 100 asthmatic children aged 0-16 years demonstrated Johnson grass to be a common aeroallergen, with 14% of the study group sensitised to it (10). In 100 older patients with allergic rhinitis, Johnson grass was shown to be the most prevalent aeroallergen, with 21% of this group positive on specific IgE determination (11). 
 
Johnson grass is also a common aeroallergen in Turkey, as demonstrated by specific IgE testing of 614 respiratory allergic patients (12).
 
In Cape Town, South Africa, pollen from Johnson grass was reported to be a clinically important allergen (13).
 
Other reactions
RAST of sera from subjects sensitised to Wheat and Rye flour indicates that significant cross-reactions occur between seed extracts of 12 cereals (Wheat, Durum Wheat, Triticale, Cereal Rye, Barley, Rye grass, Oats, Canary grass, Rice, Maize, Sorghum and Johnson grass) (14). A common allergen between Johnson grass pollen and Johnson grass seed has not been demonstrated to date.

Compiled by Dr Harris Steinman, harris@zingsolutions.com

References:

    1. Avjioglu, A., M. Singh, R.B. Knox. Sequence analysis of Sor h I, the group I allergen of Johnson grass pollen and it comparison to rye-grass Lol p I (abst). J Allergy Clin Immunol 1993;91:340 
    2. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09 
    3. Yman L. Pharmacia: Allergenic Plants. Systematics of common and rare allergens. Version 1.0. CD-ROM. Uppsala, Sweden: Pharmacia Diagnostics, 2000. 
    4. Hiller KM, Esch RE, Klapper DG. Mapping of an allergenically important determinant of grass group I allergens. J Allergy Clin Immunol 1997;100(3):335-40 
    5. Esch RE, Klapper DG. Cross-reactive and unique Group I antigenic determinants defined by monoclonal antibodies. J Allergy Clin Immunol 1987;78:489-95 
    6. Suphioglu C, Singh MB, Knox RB. Peptide mapping analysis of group I allergens of grass pollens. Int Arch Allergy Immunol 1993;102(2):144-51 
    7. Sridhara S, Singh BP, Kumar L, Verma J, Gaur SN, Gangal SV. Antigenic and allergenic relationships among airborne grass pollens in India. Ann Allergy Asthma Immunol 1995;75(1):73-9 
    8. Martin BG, Mansfield LE, Nelson HS. Cross-allergenicity among the grasses. Ann Allergy 1985;54(2):99-104 
    9. Von Essen S, Fryzek J, Nowakowski B, Wampler M. Respiratory symptoms and farming practices in farmers associated with an acute febrile illness after organic dust exposure. Chest 1999;116(5):1452-8 
    10. Kongpanichkul A, Vichyanond P, Tuchinda M. Allergen skin test reactivities among asthmatic Thai children. J Med Assoc Thai 1997;80(2):69-75 
    11. Pumhirun P, Towiwat P, Mahakit P. Aeroallergen sensitivity of Thai patients with allergic rhinitis. Asian Pac J Allergy Immunol 1997;15(4):183-5 
    12. Guneser S, Atici A, Cengizler I, Alparslan N. Inhalant allergens: as a cause of respiratory allergy in east Mediterranean area, Turkey. Allergol Immunopathol (Madr) 1996;24(3):116-9 
    13. Potter PC, Berman D, Toerien A, Malherbe D, Weinberg EG. Clinical significance of aero-allergen identification in the western Cape. S Afr Med J 1991;79(2):80-4 
    14. Baldo BA, Krilis S, Wrigley CW. Hypersensitivity to inhaled flour allergens. Comparison between cereals. Allergy 1980;35(1):45-56

2002



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