IgE and T Cell Reactivity to a Comprehensive Panel of Cockroach Allergens in Relation to Disease

Abstract

IgE sensitization to cockroach allergens is associated with development of allergic diseases, such as asthma. To understand the relevance of different cockroach allergens for diagnosis and immunotherapy, a comprehensive analysis of IgE antibody levels and T cell reactivity to an expanded set of cockroach allergens and their relationship to disease was performed in a cohort of USA cockroach sensitized patients. IgE antibody levels to recombinant chitinase and hemocyanin were measured for 23 subjects by custom-made ImmunoCAPs and compared with IgE levels to eight cockroach allergens we previously reported for the same cohort. Ex vivo T cell activation (Ox40/PDL-1 expression) of PBMCs stimulated with peptide pools derived from 11 German cockroach proteins, including nine official cockroach allergens, plus chitinase and vitellogenin, was determined by flow cytometry. IgE prevalences to chitinase (17%) and hemocyanin (44%) were comparable to values for the other eight allergens that we previously reported (21-57%). Hemocyanin (Bla g 3), was a major allergen (one to which more than 50% of patients with an allergy to its source react) for a sub-group of 15 highly cockroach-sensitized subjects (IgE > 3.5 kU_A/L: 53%). Chitinase was officially named as new allergen Bla g 12. Cockroach-specific IgE levels in plasma showed excellent correlation with the sum of 10 allergen-specific IgE (r = 0.94, p < 0.001). T cell reactivity to 11 proteins was highly variable among subjects, the highest being for vitellogenin, followed by Bla g 3. The main finding was that cockroach allergen-specific IgE and T cell reactivity patterns were unique per subject, and lacked immunodominant allergens and correlation with clinical phenotype/disease severity in the studied cohort. Knowing the subject-specific B/T cell reactivity profiles to a comprehensive panel of cockroach allergens will contribute to diagnosis of cockroach allergy and will be important for planning and assessing allergen immunotherapy outcomes, according to the allergen content in therapeutic cockroach extracts.

Keywords: IgE; T-cell reactivity; asthma; cockroach allergy; diagnosis; immunotherapy; rhinitis.

Figure 1

IgE reactivity to 10 cockroach allergens and cockroach extract in a USA cohort (n = 23). Long and short horizontal lines indicate geometric means and 95% CIs, respectively. The cut-off level for IgE quantification (0.35 kU_A/L) is indicated by the horizontal dotted line. The number of negative results (< 0.35 kU_A/L) is provided for each allergen under the corresponding cluster of symbols. Data obtained with Bla g 3 (blue) and Bla g 12 (red) -measured in an equivalent manner to the values previously reported for the other allergens and the same cohort (4)- were inserted in a plot showing IgE to the other eight allergens (black). IgE levels to the 10 allergens were combined in one plot to facilitate their visual comparison, because IgE levels are consistent for the same sera (properly stored at -20˚C) when measured in different occasions by ImmunoCAP, which has a high allergen capacity (several micrograms per CAP).

Figure 2

Patterns of IgE sensitization to 10 cockroach allergens. Patterns are shown only for 10 (out of the 23 tested) subjects that recognized Bla g 3. Subjects were numbered from 1 (1441) to 23 (1445) (from lowest to highest cockroach-specific IgE levels) as shown in Table 1 . IgE data for Bla g 3 (blue) and Bla g 12 (red) are shown next to data previously measured in an equivalent manner and reported for the other eight allergens (different tones of grey) for comparison (4).

Figure 3

T cell activation in response to short-term allergen peptide pool stimulation. PBMC were stimulated with cockroach allergen-derived peptide pools for 24 h. Subsequently, T cell activation (Ox40/PDL-1 expression) was measured by flow cytometry. (A) Representative FACS plots showing Ox40/PDL-1 expression in response to medium, vitellogenin peptide pool and PHA stimulation. (B, C): Graph bars showing allergen pool-specific T cell reactivity (absolute numbers) (B) and T cell responses expressed as fold increase over medium (C). Frequency of response for each allergen is depicted on top. Each dot represents a donor. Geometric means with 95% CI are shown (n = 14 for Bla g 3, and n = 20 for the other 10 allergens).