Association of Sex and ABO-blood Group with Alpha-Gal Sensitization in a Cohort of Military Personnel

IgE antibodies to galactose-alpha-1,3-galactose (alpha-gal) are strongly linked with tick bites and cause a syndrome of mammalian meat allergy. Previous reports suggest that male sex is associated with alpha-gal sensitization, whereas B blood group is protective. We sought to investigate these associations in a large military cohort. Baseline and follow-up serum samples (median 3.5 years) were collected and stored in the Department of Defense Serum Repository from 3000 personnel stationed at 10 military bases in the central/eastern USA. Alpha-gal IgE (cut-off 0.1 kU/L) was measured by ImmunoCAP and ABO-blood group assessed by reverse-typing in a subset of the cohort. Of the 3000 subjects, median age was 19 years (IQR 18-22), 2456 (82%) were male, 179 (6.0%) were sensitized to alpha-gal at baseline and 169 (5.6%) had incident alpha-gal sensitization (defined as subjects who sero-converted or had levels increase from baseline to follow-up). 6.6% of males versus 3.3% of females were sensitized at baseline, p=0.004. Adjusted for age, race and home state the odds ratio for sensitization was 1.8 in males (95%CI 1.1-3.0). Incident alpha-gal IgE was higher in males (6.4%) than females (2.4%), p<0.001. Adjusted for age, race and military branch the odds ratio for incident alpha-gal was 1.7 in males (95%CI 1.0-3.3). Using a nested control cohort (n=169) matched for age, sex, race and geography, incident alpha-gal subjects trended toward a lower frequency of B/AB blood types (12% vs 16%), but this was not significant (p=0.28). Alpha-gal sensitization is significantly associated with male sex, but not ABO-blood group status.