Evaluation of allergic sensitivity to Acanthamoeba allergen in patients with chronic cough

Background:

Acanthamoeba and their proteins can elicit severe allergic airway inflammation in experimental mice.

Objective:

Although Acanthamoeba can induce severe allergic airway inflammation in mice, there is no allergenicity data for humans.

Methods:

We performed a skin-prick test on 65 patients with chronic cough by using 54 previously known allergens and Acanthamoeba excretory-secretory proteins and enzyme-linked immunosorbent assay on 34 patients to evaluate Acanthamoeba-specific serum immunoglobulin (Ig) levels. To detect a novel Acanthamoeba allergen, Western blot analysis was performed on serum from patients who reacted positively to Acanthamoeba or some pollen allergens.

Results:

After skin-prick testing, 29 patients (44.6%) showed positive reactions to one or more common aeroallergens. Acanthamoeba allergenicity was evaluated in 4 of 65 subjects (6.1%). An Acanthamoeba-positive reaction was closely related to several pollen allergens, especially willow tree, poplar, elm, oak, velvet grass, and cockroach. Average levels of Acanthamoeba-specific IgG subtypes in patient serum did not differ compared with healthy subjects; however, Acanthamoeba-specific IgE titers of patients were significantly higher than in healthy subjects. IgE antibodies of patients who tested positive in the skin-prick test reacted strongly to the 15 kDa excretory-secretory protein. Moreover, these antigens also reacted with those who tested positive in the skin-prick test to pollens.

Conclusion:

Taken together, our results indicated that some patients with allergy showed a positive response to the skin-prick test and that they also have high IgE serum levels. However, further experimental investigation is warranted because our preliminary findings indicated that Acanthamoeba might be a new allergen in humans.