The research group from the University of Virginia reported in 2009 a new form of delayed anaphylaxis to red meat related to IgE antibodies to the oligosaccharide galactose-α-1,3-galactose (alpha-gal). Most of these patients had tolerated meat for many years previously. They suspected that some exposure in adult life had stimulated the production of the IgE antibodies. The research focused on tick bites, which are common in the region.
3 patients showed an increase in levels of IgE to alpha-gal of 20-fold or greater after tick bites. IgE antibodies were common in areas where the tick Amblyomma americanum is common.
There was a correlation between IgE antibodies to alpha-gal and IgE antibodies to proteins derived from A americanum.
The results provided evidence that tick bites are a cause, possibly the only cause, of IgE specific for alpha-gal in this area. This is supposedly the first example of a response to an ectoparasite giving rise to an important form of food allergy.
The senior author of the article, Dr. Thomas Platts-Mills, has said during allergy society meetings that he has the alpha-gal issue himself.
The A. americanum tick is associated with subsequent delayed reactions to beef/pork via alpha-gal. There is cat-pork syndrome, which is related to IgE to Fel d2 (cat albumin), which cross-reacts with pork, dog and beef albumin.
Most patients allergic to red meat are sensitized to gelatin. Alpha-Gal IgE might be the target of reactivity to gelatin (JACI, 2012).
In this interview, JACI Associate Editor Dr. Scott Sicherer talks to author Dr. Scott Commins regarding his article "Delayed clinical and ex vivo response to mammalian meat in patients with IgE to galactose-alpha-1,3-galactose":
The reactions are delayed. There is a commercial test for diagnosis. This represents a paradigm in shift in food allergy for 2 reasons:
- reactions are not immediate, they are delayed, despite the presence of IgE antibody. Most IgE-mediated food allergic reactions are immediate.
- the antigen is carbohydrate. Most food allergies are triggered by protein antigens.
The relevance of tick bites to the production of IgE antibodies to the mammalian oligosaccharide galactose-α-1,3-galactose. Commins SP, James HR, Kelly LA, Pochan SL, Workman LJ, Perzanowski MS, Kocan KM, Fahy JV, Nganga LW, Ronmark E, Cooper PJ, Platts-Mills TA. J Allergy Clin Immunol. 2011 Mar 29.
Anaphylactic reactions to oligosaccharides in red meat: a syndrome in evolution http://goo.gl/qQXxe
Ectoparasite-induced Galactose-α-1,3-Galactose–Specific IgE Is Associated with Anaphylaxis but Not Asthma http://goo.gl/tq86r
"Ticks causing mysterious meat allergy" story hits the mainstream with CNN report: http://goo.gl/cDOLM
Image source: Giant Microbes Tick (Ixodes Scapularis) Plush Toy.
Comments from Twitter:
Nathan Hare M.D. @AllergyTalk: @Allergy Nice summary!