Expression of inducible CC chemokines in rainbow trout (Oncorhynchus mykiss) in response to a viral haemorrhagic septicemia virus (VHSV) DNA vaccine and interleukin 8.

In rainbow trout (Oncorhynchus mykiss), at least three CXC chemokines and eighteen CC chemokine sequences have been discovered in the past years, although no studies concerning their bioactivity have been performed yet. We have studied the expression of five different CC chemokines that cluster into the group of inducible chemokines (CK5A, CK5B, CK6, CK7A and CK7B) in trout injected with a plasmid coding for the glycoprotein G gene (pMCV1.4-G) of viral haemorrhagic septicemia virus (VHSV). In a previous work, we had demonstrated that a plasmid coding for the CXC chemokine interleukin 8 (IL-8, pIL8+) when co-administered with pMCV1.4-G was able to modulate the expression of induced pro-inflammatory cytokines, therefore, we have also studied the expression of these inducible CC chemokines in fish injected with pMCV1.4-G in the presence of pIL8+, study that will also help establish the relations among the different chemokine groups. All chemokines were induced in the head kidney of fish injected with the DNA vaccine, and the co-administration of pIL8+ together with the vaccine modulated the expression of all CC chemokines studied. In this sense, expression of the inducible CC chemokines was also studied in trout head kidney leucocytes treated with supernatants from EPC cells transfected with pIL8+. In this case, all CC chemokines studied except for CK5B were significantly induced by rainbow trout IL-8.