Temperature modulates the immunological response of the sub-antarctic notothenioid fish Eleginops maclovinus injected with Piscirickettsia salmonis

Eleginops maclovinus is a eurythermic fish that under natural conditions lives in environments with temperatures ranging from 4 to 18 degrees C and can be usually captured near salmon farming areas. The aim of this study was to evaluate the effect of temperature over the innate and adaptive immune response of E. maclovinus challenged with Piscirickettsia salmonis following different treatments: C- (control injection with culture medium at 12 degrees C), C+ (bacterial injection at 12 degrees C), 18 degrees C c/A + B (injection with culture medium in acclimation at 18 degrees C), 18 degrees C c/A + B (bacterial injection in acclimation at 18 degrees C), 18 degrees C s/A + M (injection with culture medium without acclimation at 18 degrees C) and 18 degrees C s/A + B (bacterial injection without acclimation at 18 degrees C). Each injection had 100 mu L of culture medium or with 100 mu L at a concentration 1 x 10(8) of live bacteria, sampling six fish per group at 4, 8, 12, 16 and 20 days post-injection (dpi). Expression of the mRNA related with the innate immune response gene (TLR1, TLR5, TLR8, NLRC3, NLRC5, MyD88 and IL-1 beta) as well as the adaptive immune response gene (MHCI, MHCII, IgMs and IgD) were measured in spleen and head kidney. Gene expression profiles were treatment-type and time dependent. Levels of Immunoglobulin M (IgM) increased in challenged groups with P. salmonis from day 8-20 post challenge, which suggest activation of B cells IgM + through P. salmonis epitope detection. Additionally, a rise in temperature from 12 degrees C (C+) to 18 degrees C (with/without acclimation) also resulted in antibody increment detected in serum with significant differences between 18 degrees C c/A + B and 18 degrees C s/A + B groups. This is the first study that evaluates the effect of temperature changes and mRNA expression related with immune system gene over time on E. maclovinus, a native wild life fish that cohabits in the salmon farming environment.