Heritability Estimation for Escherichia coli O157:H7 Vaccine Response in Beef Cattle

Abstract Text:

Humoral vaccine response has been shown to be heritable for several bovine vaccines.  However, heritability for response to an E. Coli 0157 vaccine in cattle has not been estimated. Our objective was to estimate the heritability of humoral response to a commercially available E. coli 0157 vaccine.  Crossbred cattle from various proportions of 16 different breeds (Angus, Hereford, Red Angus, Shorthorn, Brahman, Brangus, Beefmaster, Santa Gertrudis, Braunvieh, Charolais, Chiangus, Gelbvieh, Maine Anjou, Limousin, Salers, Simmental) in the USMARC Germplasm Evaluation Program (n=677) were vaccinated with a commercially available E. coli 0157 vaccine (Epitopix, LLC, Willmar, MN) and then received a booster shot one month after the initial vaccination.  Three blood samples were collected: 1) time of initial vaccination (d0), 2) time of booster vaccination (d30), and 3) approximately one month following booster vaccination (d60).  Antibodies present in plasma that were specific for the siderophore receptor and porin (SRP) proteins used in the vaccine were measured with an enzyme-linked immunosorbent assay (ELISA) in parallel with positive and negative controls.  Sample-to-positive (S/P) ratios were calculated from ELISA optical densities for each sample.  Of the 677 calves included in the study, 166 had antibodies circulating in their blood at time of initial vaccination (S/P >0.14).  These 166 animals were not analyzed further because the presence of circulating antibodies at initial vaccination could have interfered with vaccine response.  Vaccine response was defined as the difference between 1) antibodies present at time of booster shot minus antibodies present at time of initial vaccination (initial response), 2) antibodies present one month after booster vaccination minus antibodies present at time of booster vaccination (booster response), and 3) antibodies present one month after booster vaccination minus antibodies present at time of initial vaccination (overall response). The estimated heritability of initial response to the vaccine was 0.29 ± .121 at time of initial vaccination (P=0.0028).  However, we did not find evidence that the booster or overall response to the vaccine was heritable (h²  = .05 ± .084 for booster and h² = 0.03 ± 0.078 for overall response; P>0.05).  We conclude that the initial humoral response to this E. Coli 0157:H7 vaccine is moderately heritable.  If vaccine response is heritable, we may be able to identify cattle that are genetically predisposed towards mounting a more protective immune response.  

Keywords: Heritability; Escherichia coli O157:H7; Vaccine Response