Genome Wide Association Study of E. coli O157:H7 Vaccine Response in Beef Cattle

A genome wide association study (GWAS) was completed on 483 crossbred beef calves to identify SNPs associated with variation in Escherichia coli O157:H7 vaccine response. Calves were part of the USMARC Germplasm Evaluation herd, which consists of various proportions of 16 different breeds.  Calves (n=642) were administered a commercially available Escherichia coli (E. Coli) O157:H7 vaccine (Epitopix, Willmar, MN) at 74 to 171 days old (d0) and a booster vaccination three weeks later (d21).  Plasma antibodies that were specific for siderophore receptor and porin (SRP) proteins in the vaccine were measured with an ELISA at d0 and d21.  To adjust for ELISA plate-to-plate variation, sample-to-positive (S/P) ratios were calculated from ELISA optical density values for each sample.  Calves with S/P ratios > 0.14 at d0 were removed (n=159).  Vaccine response was derived as the difference between antibodies at d21 and d0.  Calves were genotyped with the Bovine HD GGP chip. A linear model with fixed effects sex, birth location, and genotype and covariates heterosis and calf age at initial vaccination was used.  At the 5% genome wide significance level, two SNP were significantly associated with vaccine response: ARS-BFGL-NGS-95268; BTA4 with additive effect 0.23 ± 0.040 and dominance effect 0.19 ± 0.043, and BovineHD1000027842; BTA10 with additive effect 0.00 ± 0.013 and dominance effect -0.08 ± 0.016.  At the 5% false discovery rate (FDR), one additional SNP was significantly associated with vaccine response (ARS-BFGL-NGS-107725; BTA19 with additive effect 0.03 ± 0.011 and dominance effect 0.05 ± 0.014).