Specific Regulation of the Chemokine Response to Viral Hemorrhagic Septicemia Virus at the Entry Site

Abstract

The fin bases constitute the main portal of rhabdovirus entry into rainbow trout (Oncorhynchus mykiss), and replication in this first site strongly conditions the outcome of the infection. In this context, we studied the chemokine response elicited in this area in response to viral hemorrhagic septicemia virus (VHSV), a rhabdovirus. Among all the rainbow trout chemokine genes studied, only the transcription levels of CK10 and CK12 were significantly upregulated in response to VHSV. As the virus had previously been shown to elicit a much stronger chemokine response in internal organs, we compared the effect of VHSV on the gills, another mucosal site which does not constitute the main site of viral entry or rhabdoviral replication. In this case, a significantly stronger chemokine response was triggered, with CK1, CK3, CK9, and CK11 being upregulated in response to VHSV and CK10 and CK12 being down-modulated by the virus. We then conducted further experiments to understand how these different chemokine responses of mucosal tissues could correlate with their capacity to support VHSV replication. No viral replication was detected in the gills, while at the fin bases, only the skin and the muscle were actively supporting viral replication. Within the skin, viral replication took place in the dermis, while viral replication was blocked within epidermal cells at some point before protein translation. The different susceptibilities of the different skin layers to VHSV correlated with the effect that VHSV has on their capacity to secrete chemotactic factors. Altogether, these results suggest a VHSV interference mechanism on the early chemokine response at its active replication sites within mucosal tissues, a possible key process that may facilitate viral entry.

CCR7 Is Mainly Expressed in Teleost Gills, Where It Defines an IgD+IgM− B Lymphocyte Subset

“…We have previously established that at these days postinfection, VHSV induces the transcription of several chemokine genes in both gills and head kidney (28,29). In some fish, the number of mem IgD cells was also assessed.…”

“…The VHSV challenge was performed as previously described (28). Briefly, 12 fish of ∼200 g were transferred to 4 l viral solution containing 5 3 10 5 TCID 50 /ml VHSV strain 0771.…”

Sublethal concentrations of ichthyotoxic alga Prymnesium parvum affect rainbow trout susceptibility to viral haemorrhagic septicaemia virus

“…It might thus be hypothesized that sublethal algal concentrations could further predispose this transmission route through the gills. Later, other transmission routes were identified, through skin and fin bases (Harmache et al 2006, Montero et al 2011 as well as per os (Schönherz et al 2012). Comparative histological studies on the propagation of VHSV in fish exposed to different concentrations of P. parvum are required to determine how this alga affects development of VHS as reported here.…”

DNA vaccination against a fish rhabdovirus promotes an early chemokine-related recruitment of B cells to the muscle

“…Six hundred l of different dilutions of CK5B or CK6 in culture medium were placed at the bottom of the wells, while 100 l of the different leukocyte cell suspensions were loaded to the upper chamber. After 2 h at 20 • C, the number of cells that had migrated to the bottom of the wells was quantified by flow cytometry as previously described [25].…”

“…Reaction mixtures were incubated for 10 min at 95 • C, followed by 40 amplification cycles (30 s at 95 • C and 1 min at 60 • C). For each gene, expression was normalized to that of elongation factor 1␣ (EF-1␣) expression in each sample and expressed as 2 − Ct as described previously [25].…”