Parasite-related IgE Antibodies, Including IgE to Galactose-alpha-1,3-galactose, in Sera from Virginia and Ecuador

Rationale IgE antibodies to galactose-alpha-1,3-galactose (alpha-gal) have become increasingly prevalent in the southeastern United States. These antibodies have recently been linked to bites from the tick Amblyomma americanum, but the possibility of a role for other parasites remains. Methods Assays for IgE were performed on patients with delayed urticaria or anaphylaxis to meat and controls in Virginia (n=125), as well as a cohort from Esmeraldas Province, Ecuador (n=295) where Echinococcus is not endemic. Results The significant association between IgE antibodies to alpha-gal and IgE to Echinococcus was strongest in Virginia (r=0.74 vs r=0.62 for Ecuador, both p<0.001). Further, only 3/37 Echinococcus IgE-positive subjects in Virginia were not positive for IgE to alpha-gal. In Ecuador, 118/223 Ascaris-positive sera were negative for IgE to alpha-gal; by contrast, in Virginia 52/79 alpha-gal positive sera were negative for Ascaris and only one sera was Ascaris-positive and alpha-gal negative. Virginia sera with IgE to Echinococcus (class 2 and 3) were absorbed with alpha-gal linked to Sepharose beads, which removed all detectable IgE to Echinococcus. Conclusions We think that the limited number of positive assays for Echinococcus and Ascaris in Virginia can be explained by cross-reactivity with alpha-gal, which may also be relevant for Echinococcus in Esmeraldas. By contrast, many sera in Ecuador had high titer IgE to Ascaris with negative responses to alpha-gal. None of these IgE antibodies were significantly associated with asthma in the United States, while IgE to Ascaris was significantly associated with asthma in Ecuador