High-risk groups for alpha-gal sensitization.

BACKGROUND

Tick bite-induced IgE-mediated reactions to the oligosaccharide galactose α-1,3-galactose (alpha-gal) are increasingly recognized. This study investigated alpha-gal sensitization in three groups with different tick bite exposure.

MATERIALS AND METHODS

Specific IgE antibodies to alpha-gal and total IgE were investigated in 485 patients with Lyme borreliosis with different disease manifestations and compared to a control group of 200 randomly selected patients without increased exposure to tick bites. A group of 232 hunters and forest workers served as a model for multiple tick bites.

RESULTS

Specific IgE (sIgE) antibodies to alpha-gal (> 0.1 kU/L) were found in 12.6% of all borreliosis samples compared to the control group with 9% (relative risk 1.4; 95% CI 0.85 - 2.3; not significant (n.s.). The highest prevalence of sIgE to alpha-gal was observed in hunters and forest service employees (22.8%, relative risk 2.5; 95% CI 1.5 - 4.2; p < 0.001). Higher age and elevated total IgE were also associated with alpha-gal sensitization.

CONCLUSION

IgE sensitization to alpha-gal tends to be more frequent in tick-exposed patients with borreliosis than in controls (n.s.). Moreover, hunters and forest workers show an even higher rate of elevated IgE to alpha-gal. Thus, frequent tick contact may result in alpha-gal sensitization. In the area of Munich, the prevalence of alpha-gal sensitization appears lower than in the state of Baden-Württemberg and lower than in the USA, which may be due to the difference in tick species or the frequency of tick exposure. This study could show that alpha-gal sensitization and presumably alpha-gal syndrome does not seem to be a modern problem but existed already more than 30 years ago.

Informations de copyright

© Dustri-Verlag Dr. K. Feistle.

Déclaration de conflit d'intérêts

TB was investigator for Thermo Fisher Scientific and reports non-financial support (laboratory material and analytical support) from Thermo Fisher Scientific. All other authors report no conflict of interest in relation to this work. Table 1.Borreliosis stage and elevated specific IgE antibodies against alpha-gal with a threshold of > 0.1 kU/L; population at high risk for tick bites divided into forest workers from 1988 and forest service employees, hunters, and members of hunting societies, and patients (acute borreliosis: erythema migrans; chronic borreliosis: acrodermatitis chronica atrophicans). PopulationNumber of patients0,1 – 0.69 CAP 0 – 1 n0.70 – 3.49 CAP 2 n3.50 – 17.49 CAP 3 n17,50 – 49,99 CAP 4 n50.0 – 99.99 CAP 5 n> 100 kU/L CAP 6 nn (% of total)Acute borreliosis3652812200042 (11.5%)Chronic borreliosis120132400019 (15.8%)Total: 61 (12.6%)Forest workers 19885653300112 (21.4%)Forest service employees 2016176238721041 (23.3%)Total 53 (22.8%)Control group2001620000Total 18 (9%)sIgE = specific IgE. Figure 1Prevalence of elevated specific IgE antibodies to alpha-gal in the tested populations. The prevalence of specific IgE to alpha-gal was significantly higher in hunters/forest workers than in borreliosis patients and controls. **p < 0.01, ***p < 0.001. Continuous numerical variables were calculated as medians and interquartile ranges and compared by the non-parametric Mann-Whitney test for independent variables. The Kruskal-Wallis test was applied to compare continuous numerical variables between the groups. Table 2.Comparison of the relative sensitization risk in two tick-exposed populations. Tick bite-exposed groups show different increased relative risk for developing alpha-gal sensitization compared to controls. RR95% CIpBorreliosis group1.40.85 – 2.3(n.s.)Hunters2.51.5 – 4.2p < 0.001RR = relative risk; 95% CI = 95% confidence interval; n.s. = not significant. Figure 2Age distribution among borreliosis patients (a) and control group (b). Specific IgE to alpha-gal > 0.1 kU/L, absolute numbers. An increased sensitization in patients older than 50 years was observed in both groups.