post-title What do a cancer drug, food allergies and tick bites have in common? 2014-10-16 16:12:49 yes no Posted by

What do a cancer drug, food allergies and tick bites have in common?

by: Dr. Phillip Rancitelli  In 2006, a drug called cetuximab (trade name Erbitux) entered the market for the treatment metastatic colorectal cancer and some head and neck cancers.  Soon after, allergic reactions, some very severe, were reported during the first administration.  An observation was made that these allergies occurred more commonly in the southern United […]

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by: Dr. Phillip Rancitelli PhillipRancitelli

In 2006, a drug called cetuximab (trade name Erbitux) entered the market for the treatment metastatic colorectal cancer and some head and neck cancers.  Soon after, allergic reactions, some very severe, were reported during the first administration.  An observation was made that these allergies occurred more commonly in the southern United States.

Immunology studies showed that these patients produced IgE (allergic) antibodies against a sugar called galactose–a-1,3-galactose (a-gal), which is present in cetuximab.  Researchers, however, couldn’t explain the geographic distribution of these reactions.

Meanwhile, allergists in Virginia began to encounter a different group of patients with allergic reactions who also demonstrated this allergic antibody.  Many of these patients said their reactions occurred hours after ingestion of beef or pork.  Interestingly, a-gal is a blood group component of nonprimate mammals.  The time course of these reactions made it difficult to understand, because most allergic reactions to foods occur very quickly (not 4-5 hours later).  Subsequent case reports of similar reactions popped up all over the southern United States.

Eventually, an observation was made that the distribution of increased reactions to cetuximab overlapped areas where Rocky Mountain spotted fever (a disease carried by ticks) occurs.  Patients were then questioned about previous tick bites, and further immunologic studies suggested that bites from the lone star tick, Amblyomma americanum, were the source of antibody production against a-gal.

Although the exact mechanisms are unclear at this time, it appears as though tick bites in certain individuals trigger the production of high levels of allergic antibodies against a-gal.  Subsequent exposure to a-gal (i.e. cetuximab or nonprimate mammalian meat) can elicit a severe allergic reaction.  The delay in symptoms with foods hasn’t been fully explained and is an area of great interest among immunologists.

Cases of delayed anaphylaxis to meat have now been reported in northern states and other countries, and the allergists/immunologists at Midwest Allergy are currently screening patients (with a suspicious history) for this type of allergy.

The discovery of this a-gal phenomenon illustrates how complex the immune system is, and how knowledge in the field of allergy and immunology continues to grow at a rapid pace.

Philip N. Rancitelli, M.D., F.A.A.A.A.I.

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