Dynamic Distribution of Infectious Pancreatic Necrosis Virus (IPNV) Strains of Genogroups 1, 5, and 7 after Intraperitoneal Administration in Rainbow Trout (Oncorhynchus mykiss)

MK-0608 inhibits in vitro and in vivo RNA replication of infectious pancreatic necrosis virus

Infectious pancreatic necrosis virus (IPNV) is an important pathogen that is threatening the worldwide salmon and trout industry. But there is no therapeutic drug available for now. In this study, we demonstrate that MK-0608 is highly efficient against IPNV and low cytotoxic, with a 50 % effective concentration (EC50) of 0.20 μM and selectivity index (SI) of about 268. Time of addition assay illustrated that MK-0608 targeted the early stage of IPNV life cycle. Furthermore, we found that MK-0608 blocked IPNV attachment on the premise of sufficient pre-incubation time but MK-0608 did not influence viral internalization and release. MK-0608 could inhibit IPNV genome synthesis, and combination with ribavirin enhanced the inhibition effect, which might be functional via binding to IPNV RNA dependent RNA polymerase (RdRp), which was predicted by using molecular docking methods. In vivo test showed that IPNV was extremely suppressed in the rainbow trout (Oncorhynchus mykiss) with one single dose of MK-0608, and the higher dosage of 50 mg/kg could cause 3 log decrease of IPNV loads in fish tissues.

Characterization of the activity of 2'-C- methylcytidine against infectious pancreatic necrosis virus replication

Infectious pancreatic necrosis virus (IPNV) is the pathogen of infectious pancreatic necrosis (IPN), which can cause high mortality in salmonids, harm the healthy development of salmon-trout aquaculture, and lead to huge economic losses. However, in China, there is currently neither a commercially available vaccine to prevent IPNV infection nor antiviral drugs to treat IPNV infection. The genome of IPNV consists of two segments of dsRNA named A and B. Segment B encodes the RNA-dependent RNA-polymerase (RdRp) VP1 which is essential for viral RNA replication and is therefore considered an important target for the development of antiviral drugs. In this study, we investigate whether 2'-C-methylcytidine (2CMC), a nucleoside analog which target viral polymerases, has an inhibitory effect on IPNV both in vitro and in vivo. The results show that 2CMC inhibits IPNV infection by inhibiting viral RNA replication rather than viral internalization or attachment. In vivo experiment results showed that 2CMC could inhibit viral RNA replication and reduce viral load in rainbow trout (Oncorhynchus mykiss). In our study, we have revealed that 2CMC has a potent inhibitory effect against IPNV infection. Our data suggest that 2CMC is an attractive anti-IPNV drug candidate which will be highly valuable for the development of potential therapeutics for IPNV.

Characterization of a Novel Infectious Pancreatic Necrosis Virus (IPNV) from Genogroup 6 Identified in Sea Trout (Salmo trutta) from Lake Vänern, Sweden

In November 2016, infectious pancreatic necrosis virus (IPNV) was isolated from a broodstock female of landlocked sea trout (Salmo trutta) in Lake Vänern in Sweden. VP2 gene sequencing placed the IPNV isolate in genogroup 6, for which pathogenicity is largely unknown. Lake Vänern hosts landlocked sea trout and salmon populations that are endangered, and thus the introduction of new pathogens poses a major threat. In this study we characterized the novel isolate by conducting an infection trial on three salmonid species present in Lake Vänern, whole genome sequencing of the isolate, and prevalence studies in the wild sea trout and salmon in Lake Vänern. During the infection trial, the pathogenicity of the Swedish isolate was compared to that of a pathogenic genogroup 5 isolate. Dead or moribund fish were collected, pooled, and analyzed by cell culture to identify infected individuals. In the trial, the Swedish isolate was detected in fewer sample pools in all three species compared to the genogroup 5 isolate. In addition, the prevalence studies showed a low prevalence (0.2-0.5%) of the virus in the feral salmonids in Lake Vänern. Together the data suggest that the novel Swedish IPNV genogroup 6 isolate is only mildly pathogenic to salmonids.