Submitted to: Entomology and Applied Science Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/2014
Publication Date: 12/18/2014
Citation: Mattison, C.P., Dowd, P.F., Tarver, M.R., Grimm, C.C. 2014. Induction of glutathione S-Transferase in Helicoverpa zea fed cashew flour. Entomology and Applied Science Letters. 1:60-69.
Interpretive Summary: The frequency of peanut and tree nut allergy has increased during the past decade, and the only accepted management practice for food allergy sufferers is to strictly avoid the allergy causing food. Food allergies are caused by proteins in the foods we eat. Insects have adapted over millions of years to efficiently digest plant foods, and they have specialized enzymes that can break down plant proteins. We are searching for novel insect enzymes that can be used in food processing steps to reduce or eliminate the ability of these proteins to cause food allergy. We found that some insect proteins are increased in abundance when the corn earworm (Helicoverpa zea) is fed a diet including cashew nut protein. Continued research in this area could identify additional insect enzymes that may be useful in enzymatic processing steps to reduce or eliminate nut allergens, and may have application in the food industry or health fields.
Technical Abstract: H. zea and other insects have evolved strategies to counteract the plant protective proteins and defensive compounds they may encounter during feeding. We sought to take advantage of this phenomenon by identifying proteins upregulated in H. zea in response to the inclusion of cashew nut flour in their diet. Tree nut and peanut seed storage proteins can act as defensive compounds protecting the tissue from insect damage by inhibiting digestion. When ingested by humans, these proteins can act as potent food allergens that may cause harmful physiological responses in food allergy affected individuals. Cashew allergens, such as the 2S albumin Ana o 3, have homology to protease or amylase inhibitors that inhibit digestion. Insects, such as the corn earworm, Helicoverpa zea, feed on various plant species that contain similar protease or amylase inhibitors and additional defensive compounds. Here, we compared the intestinal protein profile of H. zea fed on media containing pinto bean, cashew, or peanut. Through comparative feeding studies, mass-spectrometry, and glutathione binding assays, we demonstrate that Glutathione S-transferases (GST) are specifically induced in the larvae of H. zea when cashew protein is included in their diet. We assessed the ability of purified H. zea GST proteins to break the disulfide bonds of cashew extract proteins and the purified Ana o 3 allergen. Continued research in this area could identify insect enzymes that may be useful in enzymatic processing steps to reduce or eliminate nut allergens, and may have application in the food industry or health fields.