An ancient lineage of highly divergent parvoviruses infects both vertebrate and invertebrate hosts.

Abstract

Chapparvoviruses are a highly divergent group of parvoviruses (family Parvoviridae) first identified in 2013. Interest in these poorly characterized viruses has been raised by recent studies indicating that they are the cause of chronic kidney disease that arises spontaneously in laboratory mice. In this study, we investigate the biological and evolutionary characteristics of chapparvoviruses via comparative analysis of genome sequence data. Our analysis, which incorporates sequences derived from endogenous viral elements (EVEs) as well as exogenous viruses, reveals that chapparvoviruses are an ancient lineage within the family Parvoviridae, clustering separately from members of both currently established parvoviral subfamilies. Consistent with this, they exhibit a number of characteristic genomic and structural features, i.e. a large number of putative auxiliary protein-encoding genes, capsid protein genes non-homologous to any hitherto parvoviral cap, as well as a putative capsid structure lacking the canonical fifth strand of the ABIDG sheet comprising the luminal side of the jelly roll. Our findings demonstrate that the chapparvovirus lineage infects an exceptionally broad range of host species, including both vertebrates and invertebrates. Furthermore, we observe that chapparvoviruses found in fish are more closely related to those from invertebrates than they are to those that infect amniote vertebrates. This suggests that transmission between distantly related host species may have occurred in the past. Our study provides the first integrated overview of the chapparvovirus group, and revises current views of parvovirus evolution\n\nAUTHOR SUMMARYChapparvoviruses are a recently identified group of viruses about which relatively little is known. However, recent studies have shown that these viruses cause disease in laboratory mice and are prevalent in the fecal virome of pigs and poultry, raising interest in their potential impact as pathogens, and utility as experimental tools. We examined the genomes of chapparvoviruses and endogenous viral elements ( fossilized virus sequences derived from ancestral viruses) using a variety of bioinformatics-based approaches. We show that the chapparvoviruses have an ancient origin and are evolutionarily distinct from all other related viruses. Accordingly, their genomes and virions exhibit a range of distinct characteristic features. We examine the distribution of these features in the light of chapparvovirus evolutionary history (which we can also infer from genomic data), revealing new insights into chapparvovirus biology.