title: Giant ragweed specific immunotherapy is not effective in a proportion of patients sensitized to short ragweed: analysis of the allergenic differences between short and giant ragweed.
abstract: BACKGROUND
  Short ragweed and giant ragweed pollen allergens are considered largely cross-reactive, and it is generally believed that 1 species is sufficient for skin testing and immunotherapy. However, in the area north of Milan (a zone widely invaded only by short ragweed), about 50% of patients submitted to injection specific immunotherapy with giant ragweed showed little or no clinical response, but showed an excellent outcome if they were shifted to short ragweed specific immunotherapy.
  
  
  OBJECTIVE
  To investigate allergenic differences between short and giant ragweed.
  
  
  METHODS
  IgE reactivity to short ragweed of sera from 16 patients allergic to ragweed was assessed by immunoblot before and after absorption with short and giant ragweed. Moreover, 41 ragweed-monosensitive patients underwent skin prick test with both ragweed species.
  
  
  RESULTS
  In several cases, preabsorption of sera with giant ragweed extract was unable to inhibit IgE reactivity fully against both a 43-kd allergen and other allergens at different molecular weights in short ragweed. On skin prick test, short ragweed induced larger wheals than giant ragweed in the majority of patients, and 6 of 41 (15%) patients were strongly short ragweed-positive but giant ragweed-negative. The immunoblot with the serum from 1 of these subjects showed a strong IgE reactivity to short ragweed at about 43 kd in the absence of any reactivity to giant ragweed.
  
  
  CONCLUSIONS
  Short and giant ragweed are not allergenically equivalent. Allergenic differences involve both the major allergens Amb a 1-2/Amb t 1-2 and some minor allergens. In patients allergic to ragweed, both diagnosis in vivo and immunotherapy should always be performed by using the ragweed species present in that specific geographic area.
authors.affiliation: Ambulatorio di Allergologia, Clinica San Carlo, Paderno Dugnano, MI, Italy. r.asero@libero.it
authors.forename: Riccardo
authors.initials: R
authors.lastname: Asero
authors.forename: Bernhard
authors.initials: B
authors.lastname: Weber
authors.forename: Gianni
authors.initials: G
authors.lastname: Mistrello
authors.forename: Stefano
authors.initials: S
authors.lastname: Amato
authors.forename: Enzo
authors.initials: E
authors.lastname: Madonini
authors.forename: Oliver
authors.initials: O
authors.lastname: Cromwell
mesh_terms: D000293:Adolescent; D000328:Adult; D031164:Ambrosia / Q000145:classification* / Q000276:immunology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000175:diagnosis / Q000628:therapy*; D007114:Immunization; D007073:Immunoglobulin E / Q000097:blood; D007167:Immunotherapy; D008297:Male; D011446:Prospective Studies; D012698:Serologic Tests; D012882:Skin Tests; D013045:Species Specificity; D017211:Treatment Failure
chemical_list: D007073:Immunoglobulin E