Plasma proteomic profiling of bacterial cold-water disease resistant and susceptible rainbow trout lines and biomarker discovery

Authors: Wiens, Gregory - Greg; MARANCIK, DAVID - St George'S University; CHADWICK, CHRISTOPHER - Life Diagnostics, Inc; Osbourn, Keira; REID, ROSS - US Department Of Agriculture (USDA); Leeds, Timothy - Tim

Submitted to: Frontiers in Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2023
Publication Date: 10/20/2023
Citation: Wiens, G.D., Marancik, D.P., Chadwick, C.C., Osbourn, K.E., Reid, R.M., Leeds, T.D. 2023. Plasma proteomic profiling of bacterial cold-water disease resistant and susceptible rainbow trout lines and biomarker discovery. Frontiers in Immunology. 14. https://doi.org/10.3389/fimmu.2023.1265386.
DOI: https://doi.org/10.3389/fimmu.2023.1265386

Interpretive Summary: Flavobacterium psychrophilum is the causative agent for bacterial cold water disease and is responsible for considerable losses in U.S. rainbow trout aquaculture. How rainbow trout respond to infection with this pathogen at the protein level is poorly understood. We analyzed plasma protein levels in infected fish to better understand host pathway differences between selectively bred resistant and susceptible rainbow trout lines. The relative abundance of 513 proteins were determined and compared to gene expression profiles. Important differences in protein abundance profiles between the resistant and susceptible rainbow trout lines were identified, and these differentially-abundant proteins can be grouped into 3 categories. First, some proteins were constitutively expressed, meaning that differences in protein abundance between lines existed even in the absence of infection. Second, the abundance of some proteins were infection-regulated and thus represent an acute phase response to the pathogen, and in most cases the protein abundance increased as a result of infection. Finally, some differentially-abundant intracellular proteins were identified, suggesting these proteins are released into plasma following pathogen-induced tissue damage. The disease biomarker assays developed in this study are commercially available and can be used to monitor rainbow trout and Atlantic salmon population health during grow-out.

Technical Abstract: Genetic variation for disease resistance is present in salmonid fish; however, the molecular basis is poorly understood, and biomarkers of disease susceptibility/resistance are unavailable. Previously, we selected a line of rainbow trout for high survival following standardized challenge with Flavobacterium psychrophilum (Fp), the causative agent of bacterial cold water disease. The resistant line (ARS-Fp-R) exhibits over 60 percentage points higher survival compared to a reference susceptible line (ARS-Fp-S). To gain insight into the differential host response between genetic lines, we compared the plasma proteomes from day 6 after intramuscular challenge. Pooled plasma from unhandled, PBS-injected, and Fp-injected groups were simultaneously analyzed using a TMT 6-plex label and the relative abundance of 513 proteins were determined. Data are available via ProteomeXchange, with identifier PXD041308, and the relative protein abundance values were compared to mRNA measured from a prior, whole-body RNA-seq dataset. A subset of differentially abundant proteins was identified, including troponin and myosin, that were intracellular and not transcriptionally regulated, suggesting these proteins were released into plasma following pathogen-induced tissue damage. A separate subset of high abundance, secreted proteins were transcriptionally regulated in infected fish. The highest differentially expressed protein was a C1q family member (designated complement C1q-like protein 3; C1q-LP3) that was upregulated over 20-fold in the infected susceptible line while only modestly upregulated, 1.8-fold, in the infected resistant line. Validation of biomarkers were performed using immunoassays and C1q-LP3, skeletal muscle troponin C, cathelcidin 2, haptoglobin, leptin, and growth and differentiation factor 15 exhibited elevated concentration in susceptible line plasma. Complement factor h like-1 exhibited higher abundance in the resistant line compared to the susceptible line in both control and challenged fish and thus was a baseline differentiator between lines. C1q-LP3 and STNC were elevated in Atlantic salmon plasma following experimental challenge with Fp. In summary, this dataset furthers the understanding of the differential host response to Fp and identifies salmonid biomarkers associated with disease resistance and susceptibility that may have use for genetic line evaluation and on-farm health monitoring.