INVESTIGATING THE INVOLVEMENT OF THE TICK VECTOR IN THE INDUCTION OF ALPHA-GALACTOSE HYPERSENSITIVITY (ALPHA-GAL SYNDROME, RED MEAT ALLERGY) IN THE UNITED STATES.

Abstract

Alpha-gal syndrome (AGS or sometimes called red meat allergy) is a result of the development of specific IgE antibodies to the oligosaccharide galactose-α-1,3-galactose (α-gal) after a person has had exposure to tick bites. This dissertation investigates four common tick species found in North America: the lone-star tick (Amblyomma americanum), the Gulf-Coast tick (Amblyomma maculatum), the American dog tick (Dermacentor variabilis), and the black-legged tick (Ixodes scapularis) for the presence of α-gal by utilizing a combination of immunoproteomic approaches and carbohydrate analysis techniques. Anti-α-gal IgM antibodies (M86) were used in immunoblotting to detect α-gal in the saliva and salivary glands of both Am. americanum and Ix. scapularis, while Am. maculatum and De. variabilis were found to lack α-gal. Incubation of Am. americanum partially-fed salivary gland protein extracts with PNGase F confirmed the deglycosylation of N-linked α-gal containing glycans from tick salivary glycoproteins. Immunolocalization of α-gal moieties to the tick salivary secretory vesicles of the salivary acini by confocal microscopy also confirmed the likelihood of a secretory nature of α-gal-containing antigens by ticks. Am. americanum ticks were fed mechanically-defibrinated human blood (lacks α-gal) using a silicone membrane system in an attempt to determine the source of the α-gal. N-linked glycan analysis revealed that Am. americanum and Ix. scapularis contain α-gal in their saliva and salivary glands, but Am. maculatum contains no detectable quantity of α-gal. Consistent with the N-glycan profiling and analysis, salivary samples from Am. americanum and Ix. scapularis stimulated activation of basophils that were primed with plasma from α-gal allergic subjects. Proteomic data generated from these experiments offered multiple potential targets for further investigation and RNAi gene silencing. Together, these data support the theory that bites from only some tick species may specifically create an enhanced risk for the development of α-gal-specific IgE and hypersensitivity reactions in humans. The findings within this research have paved the way for future α-gal research in the tick, however, the exact mechanism by which ticks sensitize a host to α-gal continues to remain unknown