Gastro-allergic
anisakiasis and Anisakis sensitisation associated
chronic urticaria are diseases which differ in their
IgE and
IgG4 responses against both
crude extract and specific
allergens. Anisakis and Ascaris are closely related nematodes that usually cause problems with specificity in immunodiagnostics. In this study we measured
IgE and
IgG4 antibodies against Anisakis simplex sensu lato (s. l.) and Ascaris suum haemoglobins in sera of 21 gastro-allergic
anisakiasis and 23
chronic urticaria patients. We used a capture ELISA with the anti-Anisakis haemoglobin
monoclonal antibody 4E8g, which also recognises
Ascaris haemoglobin. In addition, we determined specific
IgE and
IgG4 to both nematodes by indirect ELISA and immunoblotting. Anti-A. simplex s. l. haemoglobin
IgE and
IgG4 levels were higher in gastro-allergic
anisakiasis than in
chronic urticaria patients (P=0.002 and 0.026, respectively). Surprisingly, no patient had detectable
IgE levels against A. suum haemoglobin. Finally, we carried out an in silico study of the
B-cell epitopes of both haemoglobin molecules. Five
epitopes were predicted in Anisakis pegreffii and four in A. suum haemoglobin. The
epitope propensity values of Anisakis haemoglobin in the equivalent
IgE binding region of the allergenic haemoglobin Chi t 1 from Chironomus thummi, were higher those of the
Ascaris haemoglobin. In conclusion, we describe A. simplex
haemoglobin as a new major
allergen (Ani
s 13), being recognised by a large number (64.3%) of sensitised patients and up to 80.9% in patients with gastro-allergic
anisakiasis. The presence of a specific
epitope and the different values of
epitope propensity between Anisakis and
Ascaris haemoglobin could explain the lack of cross-reactivity between the two molecules. The absence of
IgE reactivity to
Ascaris haemoglobin in Anisakis patients makes Anisakis haemoglobin (Ani
s 13) a potential candidate for developing more specific diagnosis tools.