Molecular Profiles Of IgE To Timothy Grass Allergens In Patients Screened For Grass Tablet Immunotherapy

Background: Serum specific IgE levels to individual allergen components may vary depending on pollen exposure and allergen cross-reactivity. Regional differences in allergen exposure may induce different sensitization patterns. The objective of this post hoc analysis was to describe the IgE sensitization pattern in a SPT-positive patient population reporting Timothy grass allergy screened in 6 regions of North America. Specific IgE levels to a panel of 113 different allergens were measured using a microarray specific IgE method.

Methods: 1922 subject sera from the P08067 (NCT01385371) study were collected in Canada and 5 regions of the USA (Mid-Atlantic [MA], North Central [NC], Northeast [NE], South [S], West [W]). Serum specific IgE was measured using the Phadia ISAC microchip method in grass-pollen−allergic patients who consented to the analysis. Approval was obtained from appropriate IRBs.

Results: Most subjects were multi-sensitized with detectable (≥0.35 kU/L) serum specific IgE to grass and other common allergens, including tree (56%), weed (44%), animal dander (43%), mites (26%), foods (23%), and mold (22%). Out of 1922 subjects with a positive skin test to Timothy grass and history of grass pollen allergy, 1584 (82%) had measurable specific IgE to at least one of several Timothy grass allergen components (Phl p). Most subjects were sensitized to Phl p 1 (73%) and Phl p 5 (50%). The highest proportions of Phl p 1- and Phl p 5-positive subjects were found in Canada and the western part of the USA. The highest mean IgE levels against Phl p 1 and Phl p 5 occurred in sera from subjects in Canada  and the West.

Conclusions: Most subjects were sensitized to Phl p 1 (73%) and Phl p 5 (50%). The highest mean IgE levels and proportion of Phl p 1- and Phl p 5-positive subjects were found in Canada and the western part of the USA, corresponding to regions where Timothy grass (Phleum pratense) is most prevalent.

Allergen	Canada	MA	NC	NE	S	W	Grand Mean (kU/L)
Phl p 1	14.41	9.37	11.21	4.83	9.19	20.91	14.32
Phl p 5	10.24	6.42	6.25	1.40	6.26	15.96	10.01
Phl p 2	4.26	2.26	2.80	0.92	2.05	7.86	4.52
Phl p 4	2.02	1.27	0.84	0.22	0.93	3.23	1.89
Phl p 6	4.19	2.32	2.02	0.24	0.66	5.31	3.38
Phl p 7	0.15	0.11	0.04	0.00	0.06	0.46	0.21
Phl p 11	1.75	0.63	0.77	0.44	1.31	3.13	1.72
Phl p 12	0.43	0.56	0.42	0.10	0.16	0.38	0.41