Alpha-Gal Syndrome: Involvement of Amblyomma americanum α-D-Galactosidase and β-1,4 Galactosyltransferase Enzymes in α-Gal Metabolism

Alpha-Gal Syndrome (AGS) is an IgE-mediated delayed-type hypersensitivity reaction to the oligosaccharide galactose-α-1, 3-galactose (α-gal) injected into humans from the lone-star tick (Amblyomma americanum) bite. Indeed, α-gal is discovered in salivary glands of lone-star tick; however, the tick’s specific intrinsic factors involved in endogenous α-gal production and presentation to host during hematophagy are poorly understood. This study aimed to investigate the functional role of two tick enzymes, α-D-galactosidase (ADGal) and β-1,4 galactosyltransferases (β-1,4GalT), in endogenous α-gal production, carbohydrate metabolism, and N-glycan profile in lone-star tick. The ADGal enzyme cleaves terminal α-galactose moieties from glycoproteins and glycolipids, whereas β-1,4GalT transfers α-galactose to a β1,4 terminal linkage acceptor sugars—GlcNAc, Glc, and Xyl—in various processes of glycoconjugate synthesis. An RNA interference approach was utilized to silence ADGal and β-1,4GalT in Am. americanum to examine their function in α-gal metabolism in tick and AGS onset. Silencing of ADGal led to the significant downregulation of genes involved in galactose metabolism and transport in Am. americanum. Immunoblot and N-glycan analysis of the Am. americanum salivary glands showed a significant reduction in α-gal levels in silenced tissues. However, there was no significant difference in the level of α-gal in β-1,4GalT-silenced tick salivary glands. A basophil-activation test showed a decrease in the frequency of activated basophil by ADGal-silenced salivary glands. These results provide an insight into the roles of ADGal and β-1,4GalT in α-gal production and presentation in ticks and the probable involvement in the onset of AGS.

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Alpha-Gal Syndrome: Involvement of Amblyomma americanum α-D-galactosidase and α-1,4 Galactosyltransferase enzymes in α-gal metabolism

10.1101/2021.09.13.460140 ◽

2021 ◽

Author(s):

Surendra Raj Sharma ◽

Gary Crispell ◽

Ahmed Mohamed ◽

Cameron Cox ◽

Joshua Lange ◽

...

Keyword(s):

Salivary Glands ◽

Functional Characterization ◽

Basophil Activation Test ◽

Amblyomma Americanum ◽

Delayed Type Hypersensitivity ◽

Galactose Metabolism ◽

Significant Difference ◽

Ige Mediated

AbstractAlpha-Gal Syndrome (AGS) is an IgE-mediated delayed-type hypersensitivity reaction to the oligosaccharide galactose-⍰-1,3-galactose (α-gal) injected into humans from the lone star tick (Amblyomma americanum) bite. This study aims at the functional characterization of two tick enzymes, α-D-galactosidase (ADGal) and α-1,4 galactosyltransferase (β-1,4GalT) in α-gal metabolism. The ADGal enzyme cleaves terminal α-galactose moieties from glycoproteins and glycolipids, whereas β-1,4GalT transfers α-galactose to a β1,4 terminal linkage acceptor sugars: GlcNAc, Glc, and Xyl in various processes of glycoconjugate synthesis. An RNA interference approach was utilized to silence ADGal and β-1,4GalT in Am. americanum to examine their functional role in α-gal metabolism and AGS onset. Silencing of ADGal led to the significant down regulation of genes involved in galactose metabolism and transport in Am. americanum. Immunoblot and N-glycan analysis of the Am. americanum salivary glands showed a significant reduction in ⍰-gal levels in silenced tissues. However, there was no significant difference in the level of ⍰-gal in β-1,4GalT silenced tick salivary glands. A basophil-activation test showed a decrease in the frequency of activated basophil by ADGal silenced salivary glands. These results provide an insight into the role of α-D galactosidase & β-1,4GalT in tick biology and the probable involvement in the onset of AGS.

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Origin of arachidonic acid in the salivary glands of the lone star tick, Amblyomma americanum

Insect Biochemistry and Molecular Biology ◽

10.1016/0965-1748(94)00059-q ◽

1995 ◽

Vol 25 (2) ◽

pp. 225-233 ◽

Cited By ~ 14

Author(s):

Alan S. Bowman ◽

John R. Sauer ◽

Paul A. Neese ◽

Jack W. Dillwith

Keyword(s):

Arachidonic Acid ◽

Salivary Glands ◽

Amblyomma Americanum ◽

Lone Star Tick

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Determining the Extracellular Fluid Volume (Inulin Space) of Salivary Glands of the Lone Star Tick, Amblyomma americanum (L.)1

Annals of the Entomological Society of America ◽

10.1093/aesa/67.6.994 ◽

1974 ◽

Vol 67 (6) ◽

pp. 994-996

Author(s):

J. H. Frick ◽

D. J. Brown ◽

J. R. Sauer

Keyword(s):

Salivary Glands ◽

Extracellular Fluid ◽

Amblyomma Americanum ◽

Fluid Volume ◽

Extracellular Fluid Volume ◽

Lone Star Tick ◽

Inulin Space

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Alpha-Gal and Cross-Reactive Carbohydrate Determinants in the N-Glycans of Salivary Glands in the Lone Star Tick, Amblyomma americanum

Vaccines ◽

10.3390/vaccines8010018 ◽

2020 ◽

Vol 8 (1) ◽

pp. 18 ◽

Cited By ~ 8

Author(s):

Yoonseong Park ◽

Donghun Kim ◽

Gunavanthi Boorgula ◽

Kristof De Schutter ◽

Guy Smagghe ◽

...

Keyword(s):

Salivary Glands ◽

Molecular Mimicry ◽

Amblyomma Americanum ◽

Pathogen Transmission ◽

Tick Saliva ◽

Bioactive Materials ◽

Male And Female ◽

Lone Star Tick ◽

Meat Allergy ◽

Animal Pathogens

Ticks are important ectoparasites and vectors of numerous human and animal pathogens. Ticks secrete saliva that contains various bioactive materials to evade the host defense system, and often facilitates the pathogen transmission. In addition, the Lone star tick saliva is thought to be the sensitizer in red meat allergy that is characterized by an allergic reaction to glycan moieties carrying terminal galactose-alpha-1,3-galactose (aGal). To assess N-glycome of Amblyomma americanum, we examined the N-glycan structures in male and female salivary glands at three different feeding stages and in carcasses of partially fed lone star ticks. We also surveyed the genes involved in the N-glycosylation in the tick species. The aGal epitopes and cross-reactive carbohydrate determinants (CCD) increases over time after the onset of blood feeding in both male and female A. americanum. These CCDs include xylosylation of the core mannose, 1,3-mono and 1,3- and 1,6-difucosylations of the basal GlcNac and mono- or diantennary aGal. Combinations of both xylosylation and aGal and fucosylation and aGal were also found on the N-glycan structures. While the enzymes required for the early steps of the N-glycosylation pathway are quite conserved, the enzymes involved in the later stages of N-glycan maturation in the Golgi apparatus are highly diverged from those of insects. Most of all, we propose that the aGal serves as a molecular mimicry of bioactive proteins during tick feedings on mammalian hosts, while it contributes as a sensitizer of allergy in atypical host human.

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