Effect of Selection Genotype on Immune Response to Brucella abortus RB51 in Holstein Cattle

Authors: Sarlo Davila, Kaitlyn; Boggiatto, Paola; Olsen, Steven; Lippolis, John; CROOKER, BRIAN - University Of Minnesota; Putz, Ellie

Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2023
Publication Date: 11/9/2023
Citation: Sarlo Davila, K.M., Boggiatto, P.M., Olsen, S.C., Lippolis, J.D., Crooker, B., Putz, E.J. 2023. Effect of Selection Genotype on Immune Response to Brucella abortus RB51 in Holstein Cattle. Animal Genetics. 55(1):47-54. https://doi.org/10.1111/age.13372.
DOI: https://doi.org/10.1111/age.13372

Interpretive Summary: Brucella abortus is a devastating zoonotic disease seen around the world. In both dairy and beef cattle, B. abortus causes reproductive distress including abortions, weak calves, as well as rebreed issues all of which are important to veterinary health and economic cost to producers. In domestic cattle, the B. abortus modified live vaccine RB51 has been successful in controlling and preventing disease. At the NADC we have two genetically distinct lines of Holstein dairy cattle representing modern dairy genetics as seen in commercial herds, and research animals that have been unselected for milk production since the early 1960s. Previous work has shown these two genetic groups have different immune responses to bacteria. In this study, we collected immune blood cells from modern and unselected dairy cows and challenged them in vitro with RB51 to compare differences in gene expression changes. This work is of interest to dairy producers, veterinarians, and researchers working on Brucella and similar bacterial diseases.

Technical Abstract: Genetic selection for milk production traits in U.S. Holsteins has affected a number of genes associated with reproduction and immunity. This study compares the transcriptomic response of peripheral blood mononuclear cells (PBMC) to in vitro Brucella abortus RB51 strain (RB51) bacterial challenge between contemporary Holsteins and Holsteins that have not been selected for milk production traits since the mid 1960s. Total RNA was extracted from PBMCs from four contemporary and four unselected lactating, primiparous, heifers, respectively after 24hr with or without stimulation with the commercial brucellosis vaccine, RB51. Tools present at galaxy.scinet.usda.gov were utilized to analyze the sequenced reads, which resulted in 412 significantly (FDR P < 0.05, log fold change > |1|) differentially expressed genes. The upregulated genes (genes with higher expression in selected than unselected cattle) were enriched for 19 terms/pathways, including alanine, aspartate, and glutamate metabolism, indicating a cellular stress response. Downregulated genes (genes with higher expression in unselected than selected cattle) were enriched for 37 terms/pathways, representing diverse immune responses, including natural killer cell-mediated immunity, interferon-gamma production, negative regulation of interleukin-10 production, and cytokine receptor activity indicating a broad immune response with an emphasis on immune defense. These results provide evidence that differences exist between the two genotypes in response to in vitro bacterial challenge and suggests that modern cattle that have been heavily selected for milk production at the expense of immune function, may be more genetically limited in their ability to respond to RB51.