Antimicrobial responses of teleost phagocytes and innate immune evasion strategies of intracellular bacteria

Abstract

During infection, macrophage lineage cells eliminate infiltrating pathogens through a battery of antimicrobial responses, where the efficacy of these innate immune responses is pivotal to immunological outcomes. Not surprisingly, many intracellular pathogens have evolved mechanisms to overcome macrophage defenses, using these immune cells as residences and dissemination strategies. With pathogenic infections causing increasing detriments to both aquacultural and wild fish populations, it is imperative to garner greater understanding of fish phagocyte antimicrobial responses and the mechanisms by which aquatic pathogens are able to overcome these teleost macrophage barriers. Insights into the regulation of macrophage immunity of bony fish species will lend to the development of more effective aquacultural prophylaxis as well as broadening our understanding of the evolution of these immune processes. Accordingly, this review focuses on recent advances in the understanding of teleost macrophage antimicrobial responses and the strategies by which intracellular fish pathogens are able to avoid being killed by phagocytes, with a focus on Mycobacterium marinum.

Keywords: Antimicrobial response; BKD; CFP-10; CFTR; Cytokines; DNA binding proteins from stressed cells; Dps; ECP; ESAT-6; ESX; Erp; FACS; FeSOD; Fish; Fur; IDO; IFNGR; IFNγ; IFNγrel; IL-10; IL-1β; Immune evasion; LAMP1; LPS; M1; M2; MHC; MMP; MX1; Macrophages; Mycobacterium marinum; NO; NRAMP; Pdp; Photobacterium damselae subsp. piscicida; RD-1; RNI; ROI; Rag; SOCS; SOD; Slc11a; T7SS; TGFβ; TLR; TNF-R; TNFα; Tf; TfR1; UTR; WT; bacterial kidney disease; classical/inflammatory macrophages; culture filtrate protein-10; cystic fibrosis transmembrane conductance regulator; early secretory antigenic target 6kDa; early secretory antigenic target-6 secretion system; exported repeat protein; extracellular products; fluorescence activated cell sorter; iNOS; idoleamine 2,3-dioxygenase; inducible nitric oxide synthase; interferon gamma receptor; interferon-gamma; interferon-gamma related; interleukin-1 beta; interleukin-10; iron uptake regulatory protein; iron-cofactored superoxide dismutase; lipopolysaccharide; lysosomal-associated membrane protein-1; major histocompatibility complex; matrix metalloproteinase; myxovirus (influenza virus) resistance-1; natural resistance to infection with intracellular parasites; nitric oxide; non-classical/alternatively activated macrophages; oxidative stress regulator; oxyR; reactive nitrogen intermediates; reactive oxygen intermediates; recombination activating gene; region of difference-1; solute carrier family 11a; superoxide dismutase; suppressor of cytokine signaling; toll-like receptor; transferrin; transferring receptor 1; transforming growth factor-beta; tumor necrosis factor alpha; tumor necrosis factor receptor; type-seven (VII) secretion system; untranslated region; wild type.