Page 50 - Spring2020

The tick associated with immediate allergic reactions, Nonetheless, most researchers have embraced
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hypothesis these investigators’ patients were exhibiting the notion that the presence of alpha-gal IgE
delayed symptoms—usually several or more is at the root of the cetuximab and red meat
rapidly hours after ingestion of the offending food. hypersensitivity reactions.
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became Moreover, although the National Institute of Al-
unquestioned lergy and Infectious Diseases (NIAID) defines ENTER THE TICK
Suspecting an environmental trigger,
food allergies as “a specific immune response
orthodoxy, that occurs reproducibly on exposure to a given what alpha-gal researchers needed next was an
although food” [emphasis added], individuals with the explanation as to “what causes or leads to the
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researchers new form of anaphylaxis were showing hit-or- development of the IgE response to α-gal” to
miss reactions not just to meat but also to dairy begin with. Ticks offered a ready scapegoat.
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even now and other mammalian-origin products. Some Admittedly, ticks are a nuisance, and since the
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admit that individuals were able to get by with an “alpha- advent of Lyme disease in the 1970s, they are
they do not gal-reduced” diet that included small quantities easy to cast in the role of villainous disease
of red meat.
vector. The U.S. paper published in 2009 tenta-
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understand Ordinarily, food allergies “are overwhelm- tively launched the tick hypothesis, mentioning
what ingly caused by proteins.” The allergy literature that about 80 percent of the study cohort had
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mechanism has not supported the notion that carbohydrate reported a tick bite prior to onset of symptoms.
The Australian paper (also published in 2009)
antigens “contribute significantly to the induc-
links tick tion of allergic reactions,” and yet alpha-gal then took the tick hypothesis further, postulating
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bites to an is a carbohydrate. Conceding that “the IgE “a novel association between tick bite reactions
IgE response. response to alpha-gal is different from typical and red meat allergy” and hypothesizing that
components of tick saliva were “cross-reactive
IgE responses directed towards protein aller-
gens,” alpha-gal researchers have, therefore, with proteins found in various red meats.”
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hypothesized that alpha-gal somehow “changes In 2015, two of the newly-made alpha-gal
the immune response. . . so that it is possible to experts in the U.S. shored up the tick hypothesis
have these allergic reactions.” by citing a tenuous evidentiary trail dating back
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One reason that investigators chose to to 1989, noting that professionals in Georgia
zero in on alpha-gal antibodies was that other had “collected ten cases of delayed reactions
research had previously described a severe and to mammalian meat and made a connection
sometimes fatal hypersensitivity reaction in up with the occurrence of tick bites several weeks
to 20 percent of patients receiving a recombinant or months prior to the first episode of hives
(genetically engineered) cancer drug called or anaphylaxis.” The Georgia professionals
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cetuximab, a drug produced in a mammalian reportedly presented their information to the
(murine) cell culture in which alpha-gal is pres- state’s Allergy Society as well as to the Centers
ent. The cetuximab research found that IgE for Disease Control and Prevention (CDC), but
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antibodies specific for alpha-gal were present the tick-meat allergy “connection” remained
in most of the people who went on to react to unpublished and unheeded, sitting on the shelf
the drug. for over two and a half decades before alpha-
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The French authors writing in 2009 were gal researchers apparently decided they could
not entirely convinced of the “clinical rel- make use of it.
evance” of the IgE antibodies against alpha-gal, The tick hypothesis rapidly became unques-
describing their relevance as “unclear.” A new tioned orthodoxy, although researchers even
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report in the International Archives of Allergy now admit that they do not understand what
and Immunology suggests that for some, this is mechanism links tick bites to an IgE response.
still the case; the article states that the diagnostic Nor do “all tick bite[s] per se or a tick bite from
value of alpha-gal IgE antibodies “has yet to be one particular species result in the problem.”
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clarified” and that a finding of positive antibod- A close reading of the 2009 Australian paper
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ies generally “has limited predictive value for underscores the wobbly underlying logic:
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the characteristics or severity of this allergy.” 1. First, the Australian study participants’
50 Wise Traditions SPRING 2020