Differential alpha-gal expression during Amblyomma hebraeum and Rhipicephalus evertsi tick feeding and development: A driver for the development of alpha-gal syndrome in South Africa

TL;DR

This study explores how alpha-gal, a sugar molecule in tick saliva, is expressed in South African ticks and may trigger allergic reactions in humans.

Contribution

The study identifies differential alpha-gal expression in ticks and its potential role in sensitization to alpha-gal syndrome in South Africa.

Findings

Alpha-gal–containing proteins increase in tick salivary glands with feeding time.

IgE and IgG4 levels to tick proteins are elevated in alpha-gal–allergic individuals.

Bovine thyroglobulin inhibits human anti–alpha-gal IgE binding to tick proteins.

Abstract

The presence of galactose-α-1,3-galactose (alpha-gal) in tick salivary antigens has been implicated to initiate host IgE responses resulting in sensitization to alpha-gal.

We sought to investigate the presence of alpha-gal in different anatomic locations in native South African tick species at different feeding and developmental stages and the ability of sera from our allergic cohort to bind to these tick proteins.

Alpha-gal–containing proteins in laboratory-reared ticks at different feeding and developmental stages were detected through Western blotting and immunohistochemical staining. IgE and IgG4 toward the tick proteins were analyzed via ELISA.

There is differential expression of alpha-gal in endemic South African ticks Amblyomma hebraeum and Rhipicephalus evertsi. Immunoblotting demonstrated an increase in the prominence of alpha-gal–containing protein bands in salivary glands to be proportional to feeding time. Alpha-gal in both fed and unfed ticks was localized in the salivary acini and testes. IgE and IgG4 to A hebraeum antigens were significantly raised in alpha-gal–allergic individuals. There was a correlation between anti–A hebraeum IgE and anti–alpha-gal IgE in the alpha-gal–allergic group. Inhibition of human serum anti–alpha-gal IgE to A hebraeum and R evertsi proteins was significantly reduced by the addition of bovine thyroglobulin.

We anticipate repeated exposure to differentially expressed A hebraeum and R evertsi alpha-gal–containing salivary proteins during feeding to cause alpha-gal sensitization.

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