Identification of diverse defense mechanisms in trout red blood cells in response to VHSV halted viral replication

Abstract

It has been described that fish nucleated red blood cells (RBCs) Background: generate a wide variety of immune-related gene transcripts when viruses highly replicate inside them and are their main target cell. The immune response and mechanisms of fish RBCs against viruses targeting other cells or tissues has not yet been explored and is the objective of our study.Trout RBCs were obtained from peripheral blood, ficoll purified and Methods: exposed to (VHSV). Immune response Viral Haemorrhagic Septicaemia virus was evaluated by means of RT-qPCR, flow cytometry, immunofluorescence and isobaric tag for relative and absolute quantification (iTRAQ) protein profiling VHSV N gene transcripts incremented early postexposure and were Results: drastically decreased after 6 hours postexposure (hpe). The expression of the type I interferon ( ) gene was significantly downregulated at early ifn1 postexposure (3 hpe), together with a gradual downregulation of interferon-inducible and genes until 72 hpe. Type I IFN protein was mx pkr downregulated and interferon-inducible Mx protein was maintained at basal levels. Co-culture assays of RBCs with TSS (stromal cell line from spleen) revealed the IFN crosstalk between both cell types. On the other hand, anti-microbial peptide β-defensin 1 and neutrophil chemotactic factor interleukin 8 were slightly upregulated in VHSV-exposed RBCs Isobaric tag for relative and absolute quantification (iTRAQ) revealed that VHSV exposure can induce a global protein downregulation in trout RBCs, mainly related to RNA stability and proteasome pathways. The antioxidant/antiviral response is also suggested to be involved in the response of trout RBCs to VHSV.

Infectious pancreatic necrosis virus triggers antiviral immune response in rainbow trout red blood cells, despite not being infective

“…The high basal levels of Mx protein detected inside RBCs ( Figure 2D ), much elevated than those for CHSE-214 cells ( Figure S1 ), could be implicated in the early disappearance of IPNV inside RBCs. A similar hypothesis has been made in the abortive infection of VHSV in the RTS-11 cell line 40 and in rainbow trout RBCs 16 , where upregulation or high constitutive expression of mx genes was speculated to be related to the inhibition of the virus.…”

“…IFN-1 has been reported to inhibit the production of IL-1β 45 , therefore, the cytokine reduction trend observed could have been a result of the related IFN-1 pathway upregulation. In contrast, in rainbow trout RBCs, VHSV rhabdovirus induced phosphorylation of eIF2α and a cell shut-off characterized by the downregulation of the proteome 16 .…”

“…Previously, we have demonstrated that rainbow trout RBCs can respond to VHSV, a ssRNA virus not targeting RBCs, halting its replication, downregulating type I interferon-related genes, showing global protein downregulation in the cell and phosphorylation of the translation initiation factor eIF2α 16 .…”

“…Furthermore, both viruses can induce immune responses in infected RBCs, characterized by the expression of genes related to IFN-1 (type I interferon) pathway. Besides, recently it has been shown that viral hemorrhagic septicemia virus (VHSV) halted replication in rainbow trout RBCs could induce cytokine production 16 .…”

Shape-Shifted Red Blood Cells: A Novel Red Blood Cell Stage?

“…Rainbow trout RBCs take part in the host defenses against fungal infections [ 1 ] and also have membrane receptors for pathogen associated molecular patterns (PAMPs) and produce cytokine transcripts [ 2 , 3 ]. In addition, piscine RBCs produce immune responses when infected by replicating viruses, such as infectious salmon anemia virus (ISAV) [ 4 ] or piscine orthoreovirus (PRV) [ 5 ], or by nonreplicating viruses like viral hemorrhagic septicemia virus (VHSV) [ 6 ] and infectious pancreatic necrosis virus (IPNV) [ 7 , 8 ]. Recently, it was reported that turbot RBCs produce Nk-lysin (Nkl), an antimicrobial peptide involved in the resistance against VHSV [ 9 ].…”