One Fish, One Health: Biochemistry, infectivity and immunogenicity of a novel salmonid bafinivirus

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Aquaculture, the intensive water rearing of fish, molluscs and crustaceans, presents unique challenges in contrast to all other intensive animal production systems in that the aquatic farmed and wild animals occur in the same water column, and the aquatic environmental parameters cannot be very closely controlled as for captive livestock agriculture. Consequently both farmed and wild aquatic animals in the same water column are exposed to the same viral pathogens, and absolute bio­containment cannot be attained, hence our mantra “One Fish, One Health”. The viral genetic features that account for the emergence, virulence and persistence of aquatic viruses are not well studied. This research program is on a novel salmonid coronavirus, Atlantic salmon bafinivirus (ASBV), we isolated from farmed Atlantic salmon. Nidoviruses that infect fish are classified in the genus Bafinivirus, family Coronaviridae, and order Nidovirales. Nidovirus particles are enveloped with long single-stranded RNA genomes of positive polarity. Members of the genus Bafinivirus have been isolated primarily from freshwater cyprinid species, for example White bream virus and Fathead minnow nidovirus. Chinook salmon bafinivirus (CSBV) from wild Chinook salmon in Ontario, Canada, was the first isolated salmon bafinivirus. While the clinical significance of CSBV in wild fish is unknown, it is uncertain how it would threaten farmed fish. Moreover, molecular studies of the biology of bafiniviruses may help identify major drivers of evolution of nidoviruses. The focus of this research program is primarily on the viral envelope spike (S) glycoprotein, which is predicted to play a key role in the infectivity and immunogenicity of this virus. The long-term goal of this research program is to gain a detailed molecular understanding of how ASBV emerged and its precise mechanisms of pathogenesis. The short-term objectives are:1) determine the prevalence of this novel virus and its impact on fish health; 2) map the receptor-binding domain in the S1 subunit of the ASBV S protein and its cognate host cell surface receptor(s) and investigate the host range potential of this virus; 3) study the ASBV S protein priming during replication in different fish cell lines and establish its role in tissue and cell tropism, host range and pathogenesis; 4) develop vaccines and antiviral drugs against ASBV. The proposed studies will advance our understanding of the evolution of virus-cell and virus-host interactions of Salmon bafinivirus. The outcomes of this research will not only have important practical applications for the aquaculture industry and for wild fish conservation, but will also be of significant topical virological interest since nidoviruses are a globally emerging and re-emerging group of viruses that can mutate to extend their host range in aquatic animals, and in terrestrial - farmed, pet, and wild - animals, and in humans.