Characterization of a major house dust mite allergen Der p 22 among Malaysian adult population

Abstract

Background

House dust mites (HDM) are a major trigger factor of allergic diseases worldwide.

Objective

To characterize the group 22 allergen from the HDM Dermatophagoides pteronyssinus among Malaysian atopic adults.

Methods

Recombinant Der p 22 and 33 alanine mutants were expressed in Escherichia coli and purified. Specific IgE levels to group 22 allergens were measured in serum samples from a combined cohort of Malaysian adults (n = 176) and participants from the SMCGES sub-cohort (n = 755), with responses classified by ImmunoCAP classes. Age- and gender-adjusted multivariate logistic regression was used to assess associations between Class 3+ group 22-specific IgE responses (>3.5 IU/mL) and clinical diagnoses of asthma, allergic rhinitis (AR), and atopic dermatitis (AD). IgE inhibition assays were performed to evaluate the presence of unique epitopes in Der p 22 relative to its homologue Der p 2. Epitope mapping was performed using 33 single-alanine substitution mutants of Der p 22. Statistical analyses were carried out using GraphPad Prism and logistic regression models.

Results

Recombinant Der p 22 was expressed and purified as a 17.2 kDa protein. Among 149 atopic Malaysian adults, 54% had detectable sIgE to Der p 22. IgE inhibition assays demonstrated partial cross-reactivity between Der p 22 and Der p 2. High-level group 22-specific IgE responses (Class 3+) were associated with an increased risk of asthma (OR = 1.73, 95% CI = 0.98–3.00, p = 0.0524) and significantly associated with the presence of atopic comorbidities including AR and AD (all p < 0.05). Epitope mapping identified to 6 critical residues, K10, H35, R43, D106, R117 and R130, where alanine substitution led to a marked reduction in IgE binding (median reduction >95%).

Conclusion

Der p 22 is a clinically relevant HDM allergen in the Malaysian adult population. It harbours both unique and shared IgE epitopes with Der p 2, highlighting its value for inclusion in molecular diagnostic panels to improve allergen sensitization profiling. Alanine mutation to 6 amino acid residues of Der p 22 significantly reduced IgE binding, suggesting its potential as a candidate hypoallergen molecule in allergen-specific immunotherapy.