Acute systemic inflammatory response to lipopolysaccharide stimulation in pigs divergently selected for residual feed intake

Authors: LIU, HAIBO - Iowa State University; FEYE, KRISTINA - Iowa State University; NGUYEN, YET - Old Dominion University; RAKHSHANDEH, ANOOSH - Texas Tech University; Loving, Crystal; DEKKERS, JACK - Iowa State University; GABLER, NICHOLAS - Iowa State University; TUGGLE, CHRISTOPHER - Iowa State University

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2019
Publication Date: 10/11/2019
Citation: Liu, H., Feye, K.M., Nguyen, Y.T., Rakhshandeh, A., Loving, C.L., Dekkers, J.C., Gabler, N.K., Tuggle, C.K. 2019. Acute systemic inflammatory response to lipopolysaccharide stimulation in pigs divergently selected for residual feed intake. BMC Genomics. 20(728). https://doi.org/10.1186/s12864-019-6127-x.
DOI: https://doi.org/10.1186/s12864-019-6127-x

Interpretive Summary: Pork is an important protein source, and is in high demand globally. The ability of pigs to grow rapidly and efficiently is impacted my many variables including diet and immune activation. Pigs have been selected for breeding based on feed intake and ability to convert the feed to body weight, referred to as feed efficiency. As selection and breeding has occurred based on feed efficiency, unforseen changes in immune defenses may occur secondarly. Thus, pigs from each line were treated with a bacterial compound and immune responses investigated to determine if defense against disease may change with selection based on feed intake. Immune cells in the blood responsed very similarly to the bacterial compound, though there were slight differences depending on the time since exposure to the compound. Overall, selection of pigs for feed efficiency did not dramatically alter the immune response to a conserved bacterial compound. Collectively, the results provide useful information to genetics coompanies and pork producers on secondary impacts on selection.

Technical Abstract: Background: It is unclear whether improving feed efficiency by selection for low residual feed intake (RFI) compromises pigs’ immunocompetence. Here, we aimed at investigating whether pig lines divergently selected for RFI had different inflammatory responses to lipopolysaccharide (LPS) exposure, regarding to clinical presentations and transcriptomic changes in peripheral blood cells. Results: LPS injection induced acute systemic inflammation in both the low-RFI and high-RFI line (n equals 8 per line). At 4 hours post injection (hpi), the low-RFI line had a significantly lower (p equals 0.0075) mean rectal temperature compared to the high-RFI line. However, no significant differences in complete blood count or levels of several plasma cytokines were detected between the two lines. Profiling blood transcriptomes at 0, 2, 6, and 24 hpi by RNA-sequencing revealed that LPS induced dramatic transcriptional changes, with 6,296 genes differentially expressed at at least one time point post injection relative to baseline in at least one line (n equals 4 per line)(log2(fold change)greater than or equal to log2(1.2); q less than 0.05). Furthermore, applying the same cutoffs, we detected 334 genes differentially expressed between the two lines at at least one time point, including 33 genes differentially expressed between the two lines at baseline. But no significant line-by-time interaction effects were detected. Genes involved in protein translation, defense response, immune response, and signaling were enriched in different co-expression clusters of genes responsive to LPS stimulation. The two lines were largely similar in their peripheral blood transcriptomic responses to LPS stimulation at the pathway level, although the low-RFI line had a slightly lower level of inflammatory response than the high-RFI line from 2 to 6 hpi and a slightly higher level of inflammatory response than the high-RFI line at 24 hpi. Conclusions: The pig lines divergently selected for RFI had a largely similar response to LPS stimulation. However, the low-RFI line had a relatively lower-level, but longer-lasting, inflammatory response compared to the high-RFI line. Our results suggest selection for feed efficient pigs does not significantly compromise a pig’s acute systemic inflammatory response to LPS, although slight differences in intensity and duration may occur.