Aquabirnavirus-induced Protection of Marine Fish againstPiscine Nodavirus Infection

摘要

Experimental dual-infections with a non-lethal aquabirnavirus ABV and a lethal betanodavirus redspotted grouper nervous necrosis virus: RGNNV were carried out in Japanese flounder Paralichthys olivaceus and sevenband grouper Epinephelus septemfasciatus. In the dual-infection group, ABV was intramuscularly IM injected into fish seven days before the IM-injec-tion with RGNNV. In the experiments with flounder, a high expression of an MX gene, a molecular marker for type I interferons IFN production, occurred in the head kidneys and brains at Day 7 post-ABV injection Although no mortality was found not only in the dual-infected group but also in the single infection group with RGNNV control group, the infective titers of RGNNV in the tissuesof the dual-infected group were significantly lower at any sampling times than those in the control group. In the experiments with grouper, the preceding ABV infection resulted in complete protection against RGNNV infection. The infective titers of RGNNV in the tissues were also lower in the dual-infected group than in the control group throughout the experiments, and finally the virus disappeared from the head kidneys and brains of the dual-infected group at Day 14 and Day 56 post-injections, respectively. These results suggest that an ABV-induced IFNs effectively suppresses the progression of secondary betanodavirus infection.