Modification of house dust mite allergens by monomethoxypolyethylene glycol. Allergenicity measured by in vitro and in vivo methods.

In animal models, allergen modification by coupling to monomethoxypolyethylene glycol (mPEG) molecules can reduce allergenicity of the extract and makes the allergen capable of suppressing boosted IgE response. To investigate in a human system the degree of attenuation implied by a mPEG modification of a house dust mite (Dermatophagoides pteronyssinus) extract, 55 adults with asthma caused by house dust mites were tested by skin prick test (SPT) and histamine release assay (HR). RAST inhibition was performed on sera from 6 additional patients. Modified extract containing 0.42 mmol mPEG/g protein was used for the analyses. In order to get the same response of the two extracts when assessed by HR and SPT, a median increase in concentration of 10-fold of the mPEG-modified extract compared to the unmodified extract was needed. Interindividual variation was limited. Sixty-four to 72% needed a dose increase within +/- half a decade from this value. In 42-49% of the patients, results from SPT and HR deviated less than half a decade. The relative potency of the modified extract as measured by RAST inhibition was reduced to 17-78% (mean 39%). Reduced allergenicity would by itself mean less side effects in immunotherapy. When planning such therapy it is important to know that mPEG modification reduces the allergenicity to a similar extent in a majority of patients.