Alpha-gal allergy

Alpha-gal allergy, also known as meat allergy or mammalian meat allergy (MMA), is a reaction to galactose-alpha-1,3-galactose (alpha-gal), whereby the body is overloaded with immunoglobulin E (IgE) antibodies on contact with the carbohydrate. Anti-gal is a human natural antibody that interacts specifically with the mammalian carbohydrate structure gal alpha 1-3Gal beta 1-4GlcNAc-R, termed, the alpha-galactosyl epitope. The alpha-gal molecule is found in all mammals except apes (including humans) and Old World monkeys. Alpha-gal allergy, also known as meat allergy or mammalian meat allergy (MMA), is a reaction to galactose-alpha-1,3-galactose (alpha-gal), whereby the body is overloaded with immunoglobulin E (IgE) antibodies on contact with the carbohydrate. Anti-gal is a human natural antibody that interacts specifically with the mammalian carbohydrate structure gal alpha 1-3Gal beta 1-4GlcNAc-R, termed, the alpha-galactosyl epitope. The alpha-gal molecule is found in all mammals except apes (including humans) and Old World monkeys. Bites from certain ticks, such as the lone star tick in the US, and the paralysis tick in Australia, which can transfer this carbohydrate to a victim, have been implicated in the development of this delayed allergic response to consumption of mammalian meat products. Despite myths to the contrary, individuals with alpha-gal allergy do not need to become vegetarians, because poultry, fish, and in some people, lean meat such as venison do not trigger a reaction. Alpha-gal allergy has been reported in 17 countries on all 6 continents where humans are bitten by ticks, particularly the United States and Australia. In the US, the allergy most often occurs in the central and southern regions, which corresponds to the distribution of the lone star tick. In the Southern United States, where the tick is most prevalent, allergy rates are 32% higher than elsewhere. However, as doctors are not required to report the number of patients with alpha-gal allergy, the true number of affected individuals is unknown. A typical allergic reaction to alpha-gal has a delayed onset, occurring 3–8 hours after the consumption of mammalian meat products, in contrast to the typical rapid onset of most food allergies. After the delayed onset, the allergic response is like most food allergies, and especially an IgE-mediated allergy, including severe whole-body itching, hives, angioedema, gastrointestinal upset, and possible anaphylaxis. In 70% of cases the reaction is accompanied by respiratory distress and as such is particularly harmful to those with asthma. Alpha-gal allergies are the first known food allergies that present the possibility of delayed anaphylaxis. It is also the first known food-related allergy associated with a carbohydrate, rather than a protein. Alpha-gal allergies develop after a person has been bitten by the lone star tick in the United States, the European castor bean tick, the paralysis tick and Ixodes (Endopalpiger) australiensis in Australia and a currently unknown tick in South Africa. Alpha-gal is not naturally present in apes, Old World monkeys, or humans, but is in all other mammals. If a tick feeds on another mammal, the alpha-gal remains in its alimentary tract. The tick then injects the alpha-gal into a person's skin, which causes the immune system to release a flood of IgE antibodies to fight the foreign carbohydrate. Researchers still do not know which specific component of tick saliva causes the reaction. A 2012 preliminary study found unexpectedly high rates of alpha-gal allergy in the Western and North Central parts of the United States. This suggests that unknown tick species may spread the allergy. The study even found alpha-gal allergy cases in Hawaii, where no ticks identified with the allergies live. Human factors were suggested, but no specific examples were provided. Alpha-gal is present in the anticancer drug cetuximab, as well as the intravenous fluid replacements Gelofusine and Haemaccel. Blood thinners derived from porcine intestine and replacement heart valves derived from porcine tissue may also contain alpha-gal. At least one instance of a man with an alpha-gal allergy going into anaphylaxis after receiving a heart valve transplant has been reported. Some researchers have suggested that the alpha-gal in pig's tissue that surgeons use for xenografts might contribute to organ rejection.