Mouse blood protein survives degradation in Ixodes ricinus ticks after moulting and starvation for up to five months

BACKGROUND: The alpha-Gal syndrome (AGS) is characterized by a delayed allergic response to mammalian meat and by-products. Numerous studies have confirmed that hard ticks are the source of α-Gal sensitization. However, the source of the α-Gal carrying sensitizing molecules remains controversial as α-Gal could either originate from endogenous production or residual host blood proteins. OBJECTIVE: To study the kinetics of host blood protein degradation in fully engorged Ixodes ricinus larvae upon prolonged starvation after moulting into nymphs. METHOD: 1200 I. ricinus larvae were fed on BALB/c mice under laboratory conditions. Fully engorged larvae moulted into nymphs and underwent starvation for 0, 10, and 20 weeks. Protein extracts from nymphs and larvae were analysed with LC-MS/MS mass spectrometry. RESULTS: Although 1200 larvae were fed on mice, only 249 engorged and 197 (79.12%) of the engorged larvae survived and moulted into nymphs. Overall, the global tick protein profile was similar for all stages except immediately after moulting (0 week). Peptides originating from 22 host-derived mouse proteins were detected, out of which 9 proteins were detected across all time-points post-moulting (serum albumin, hemoglobin subunits, cytosolic carboxypeptidase 2, protein KRI1 homolog, serine protease inhibitors 1c and 3k, and SH3 domain-containing protein 21). A sequence coverage of 76% was observed for mouse serum albumin, and more than 85% for hemoglobin subunits, suggesting the persistence of largely preserved host-derived mouse protein structures at all stages. CONCLUSION: Under controlled conditions, mouse blood proteins survive moulting and are passed onto the next developmental stage in I. ricinus ticks, from larvae to nymphs. These proteins are detectable up to five months post-moulting.