At the U.S. National Center for Cool and Cold Water Aquaculture, we have selected a line of rainbow trout with increased innate resistance against bacterial cold water disease (BCWD) caused by Flavobacterium psychrophilum (Fp). After five generations of sele ction, 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 on day 6 following injection challenge. Pooled plasma from unhandled , PBS-injected, and Fp -injected groups were simultaneously analyzed using a TMT 6-plex label and 513 proteins were identified and compared . Differentially abundant proteins included tissue-damage proteins, acute phase proteins, protease inhibitors and chemotactic factors . Novel ELISA and Spatial Proximity Analyte Reagent Capture Luminescence (SPARCLTM) assays were developed to confirm differential abundance . In the susceptible line, a secreted C1q family member (designated complement C1q- like protein 3; C1q-LP3) was upregulated over 20-fold while only modestly upregulated, 1.8-fold, in the resistant line . Skeletal muscle troponin C (STNC) , cathelcidin 2 (CATH2), haptoglobin, leptin, and growth and differentiation factor 15 (GDF-15) exhibited elevated concentration in susceptible-line plasma. Complement factor h like-1 (CFHL-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 study furthers the understanding of the differential host response to Fp and identifies salmonid biomarkers that may have use for genetic line evaluation and on-farm health monitoring.
Acknowledgements: This work was supported by the US Department of Agriculture, Agricultural Research Service [Project number 8082-32000-007 ]. Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S Department of Agriculture