Quercetin protects rare minnow Gobiocypris rarus from infection of genotype II grass carp reovirus

Plant-derived quercetin is a major dietary flavonoid and known mammalian transcriptional repressor for heat shock factor 1 (HSF-1), which is responsible for the transcriptional activation of heat shock proteins upon stress stimulation. Our previous studies indicated that Hsp70, the major heat shock protein during heat shock response, is induced to facilitate the infection of grass carp reovirus (GCRV), and quercetin could reduce the replication efficiency of both genotype I and III GCRVs in vitro. Here, we provide in vivo evidence to show that quercetin could effectively increase the survival rate of rare minnow Gobiocypris rarus from genotype II GCRV (GCRV-JX02) infection. Quercetin is shown to be safe for rare minnow in a dosage range of 30–480 μg/fish. Infection of rare minnow with GCRV-JX02 results in typical haemorrhagic symptom and tissue damage in pathological examination, and the semi-lethal dose (LD50) of GCRV-JX-02 is determined to be 6.0 × 102 virus genome copy number through a quantitative real-time RT-PCR assay. Quercetin dose-dependently protects rare minnow from GCRV-JX02 challenge through decreasing progeny virus production and increasing fish survival rate. Thus, quercetin demonstrates anti-aquareovirus activity in vivo and should act as a promising environmentally friendly therapeutic agent for aquaculture.