Amb a 1
Summary
Amb a 1 is a pectate lyase from short ragweed (Ambrosia artemisiifolia) pollen. Amb a 1 is a marker of sensitization to ragweed pollen. It displays limited cross-reactivity mainly within the Asteraceae pollen, with pectate lyase Art v 6 from mugwort (Artemisia vulgaris) and Hel a 6 from sunflower pollen.
Epidemiology
Worldwide distribution
Ambrosia sp pollen is a frequent and increasing cause of weed pollinosis in Europe, North America, and China [1, 2]. Ragweed sensitization is reported in up to 45% of North American atopic subjects [3]. Among the twelve A. artemisiifolia (short ragweed) allergens present in the IUIS/WHO database [4], Amb a 1 is a major allergen and a marker of sensitization to Ambrosia sp pollen [1].
Amb a 1 sensitization is observed in 95% - 97% of ragweed-allergic patients [1, 5]. In areas with high exposure to both Ambrosia sp and Artemisia sp (mugwort), the prevalence of Amb a 1 sensitization may be unrelated to the prevalence of sensitization to the corresponding pollen extract, because of primary sensitization to Artemisia and cross-reactivity between the whole allergen extracts [1].
In areas with low exposure to ragweed pollen, the prevalence of Amb a 1 sensitization is low, even among physician-diagnosed patients with allergic rhinitis (AR), as demonstrated in German and Czech studies [6, 7].
Clinical Relevance
Detailed information regarding A. artemisiifolia pollinosis, which manifests itself mainly as allergic rhinitis, rhinoconjunctivitis and asthma, is available in the whole allergen section.
Disease severity and prediction
In patients with a case history evocative of Ambrosia sp pollinosis and sensitization to Ambrosia whole allergen extract, the demonstration of Amb a 1 IgE confirms sensitization to this pollen [1].
Cross-reactive molecules
Amb a 1 cross-reactivity is mainly observed within the pectate lyase family. Cross-reactivity has been reported with homologues from other Ambrosia species [1], such as Art v 6, a minor allergen of Artemisia vulgaris [13] and Hel a 6 [14], a major allergen of Helianthus annuus (sunflower) pollen [14]. Amb a 1 also shows a degree of cross-reactivity with the unrelated major grass allergen Phl p 4 [1].
Diagnostics
Marker allergen for sensitization to Ambrosia sp pollen
Amb a 1 sensitization is found in 95-97% of patients with A. artemisiifolia pollinosis [1]. In areas of concomitant sensitization to Artemisia vulgaris or other weeds and overlapping pollination seasons, Amb a 1 assists with the identification of the primary sensitizer [1, 9, 12]. Amb a 1
Cross-Reactivity
Amb a 1 does not cross-react with pectate lyases from Cupressaceae pollen: Cup a 1/Jun a 1 and Cry j 1 [9]. Its reactivity is limited to pectate lyases from Asteraceae pollen (Art v 6, Hel a 6) and Phl p 4 [1, 9, 14].
AIT Prescription
Amb a 1 is a marker of A. artemisiifolia sensitization and can therefore aid in the decision process for AIT prescription [1]. On the therapeutic side, Amb a 1 was described as early as 1968 as an efficient AIT molecule [3].
Exposure
The main route of exposure is through inhalation of A. artemisiifolia pollen, especially at high levels of exposure [1].
References
- Matricardi, P.M., et al., EAACI Molecular Allergology User's Guide. Pediatr Allergy Immunol, 2016. 27 Suppl 23: p. 1-250.
- Li, Y., et al., Prevalence of sensitization to specific allergens in allergic patients in Beijing, China: A 7-year retrospective study. Asian Pac J Allergy Immunol, 2021.
- Pomes, A. and V. Schulten, Cross-reactivity in allergy: A double-edged sword. Allergy, 2020. 75(1): p. 9-11.
- IUIS/WHO. IUIS/WHO Ambrosia artemisiifolia. 2022 January 8 2022]; Available from: http://allergen.org/search.php?allergenname=&allergensource=Ambrosia+artemisiifolia&TaxSource=&TaxOrder=&foodallerg=all&bioname=.
- Adolphson, C., L. Goodfriend, and G.J. Gleich, Reactivity of ragweed allergens with IgE antibodies. Analyses by leukocyte histamine release and the radioallergosorbent test and determination of cross-reactivity. J Allergy Clin Immunol, 1978. 62(4): p. 197-210.
- Panzner, P., et al., A comprehensive analysis of middle-European molecular sensitization profiles to pollen allergens. Int Arch Allergy Immunol, 2014. 164(1): p. 74-82.
- Hoflich, C., et al., Management of patients with seasonal allergic rhinitis: Diagnostic consideration of sensitization to non-frequent pollen allergens. Clin Transl Allergy, 2021. 11(8): p. e12058.
- Cecchi, L., et al., Allergenicity at component level of sub-pollen particles from different sources obtained by osmolar shock: A molecular approach to thunderstorm-related asthma outbreaks. Clin Exp Allergy, 2021. 51(2): p. 253-261.
- Pichler, U., et al., Pectate lyase pollen allergens: sensitization profiles and cross-reactivity pattern. PLoS One, 2015. 10(5): p. e0120038.
- Choi, Y.J., et al., Chamber and Field Studies demonstrate Differential Amb a 1 Contents in Common Ragweed Depending on CO(2) Levels. Allergy Asthma Immunol Res, 2018. 10(3): p. 278-282.
- Gentili, R., et al., Ambrosia artemisiifolia L. temperature-responsive traits influencing the prevalence and severity of pollinosis: a study in controlled conditions. BMC Plant Biol, 2019. 19(1): p. 155.
- Asero, R., et al., Concomitant sensitization to ragweed and mugwort pollen: who is who in clinical allergy? Ann Allergy Asthma Immunol, 2014. 113(3): p. 307-13.
- Jahn-Schmid, B., et al., Humoral and cellular cross-reactivity between Amb a 1, the major ragweed pollen allergen, and its mugwort homolog Art v 6. J Immunol, 2012. 188(3): p. 1559-67.
- Ghosh, N., et al., Purification and biochemical characterization of Hel a 6, a cross-reactive pectate lyase allergen from Sunflower (Helianthus annuus L.) pollen. Sci Rep, 2020. 10(1): p. 20177.
- Wolf, M., et al., Endolysosomal protease susceptibility of Amb a 1 as a determinant of allergenicity. J Allergy Clin Immunol, 2018. 141(4): p. 1488-1491 e5.
- Wurtzen, P.A., et al., Diverse and highly cross-reactive T-cell responses in ragweed allergic patients independent of geographical region. Allergy, 2020. 75(1): p. 137-147.
- Wolf, M., et al., Amb a 1 isoforms: Unequal siblings with distinct immunological features. Allergy, 2017. 72(12): p. 1874-1882.
- Christensen, L.H., et al., Short ragweeds is highly cross-reactive with other ragweeds. Ann Allergy Asthma Immunol, 2015. 115(6): p. 490-495 e1