Abstract
Fish red blood cells (RBCs), are integral in several biologic processes relevant to immunity, such as pathogen recognition, pathogen binding and clearance, and production of effector molecules and cytokines. So far, one of the best strategies to control and prevent viral diseases in aquaculture is DNA immunization. DNA vaccines (based on the rhabdoviral glycoprotein G [gpG] gene) have been shown to be effective against fish rhabdoviruses. However, more knowledge about the immune response triggered by DNA immunization is necessary to develop novel and more effective strategies. In this study, we investigated the role of fish RBCs in immune responses induced by DNA vaccines. We show for the first time that rainbow trout RBCs express gpG of viral hemorrhagic septicaemia virus (VHSV) (GVHSV) when transfected with the DNA vaccine ex vivo and modulate the expression of immune genes and proteins. Functional network analysis of transcriptome profiling of RBCs expressing GVHSV revealed changes in gene expression related to G-protein coupled receptor (GPCR)-downstream signaling, complement activation, and RAR related orphan receptor α (RORA). Proteomic profile functional network analysis of GVHSV-transfected RBCs revealed proteins involved in the detoxification of reactive oxygen species, interferon-stimulated gene 15 (ISG15) antiviral mechanisms, antigen presentation of exogenous peptides, and the proteasome. Conditioned medium of GVHSV-transfected RBCs conferred antiviral protection and induced ifn1 and mx gene expression in RTG-2 cells infected with VHSV. In summary, rainbow trout nucleated RBCs could be actively participating in the regulation of the fish immune response to GVHSV DNA vaccine, and thus may represent a possible carrier cells for the development of new vaccine approaches.
Highlights
The fish immune system is characterized by an active innate immune system that is of primary importance in combating infections [1]
We show for the first time that rainbow trout red blood cells (RBCs) can express the glycoprotein G (gpG) of viral hemorrhagic septicaemia virus (VHSV) (GVHSV) and modulate the expression of genes related to interferon, such as interferoninducible myxovirus resistance gene, interferon-inducible RNA-dependent protein kinase, and interferon-induced protein with tetratricopeptide repeats 5
Perinuclear expression of GVHSV was observed in pmTFP1GVHSV-transfected RBCs (Figure 2B), which is in contrast to the nuclear and cytoplasmic expression observed in pmTFP1-transfected RBCs (Figure 2A)
Summary
The fish immune system is characterized by an active innate immune system that is of primary importance in combating infections [1]. A particular area of interest is the role that nucleated red blood cells (RBCs) play as immune cell mediators [2,3,4]. RBCs contain transcriptome machinery that plays an active role in the immune response against viral infections [2]. The involvement of nucleated RBCs in the immune response has been demonstrated both in vivo and in vitro. Nucleated RBCs are able to develop specific responses to different pathogen-associated molecular patterns (PAMPs) [4] and can modulate leukocyte activity by producing soluble factors [4, 7]. It has been demonstrated that fish RBCs are involved in the immune response to viral infections [7,8,9,10]
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