Genome of a novel circovirus of starlings, amplified by multiply primed rolling-circle amplification

Abstract

The genusCircoviruscomprises small non-enveloped viruses with a circular single-stranded DNA genome. By using PCR with degenerate primers, a novel circovirus (starling circovirus, StCV) was detected in spleen samples of wild starlings (Sturnus vulgarisandSturnus unicolor) found dead during an epidemic outbreak of septicaemic salmonellosis in northeastern Spain. Using a specific PCR, StCV was also detected in apparently healthy birds from the same population. The genome was amplified using multiply primed rolling-circle amplification and cloned. Open reading frames (ORFs) with similarities to the replication-associated protein and the capsid protein of circoviruses as well as an additional ORF encoding a protein of 106 aa were evident from the sequence. Phylogenetic analysis of circovirus genomes revealed the highest degree of similarity (67·1 %) between StCV and canary circovirus. A similar analysis of the evolutionarily conserved cytochromebgene of the circovirus host species revealed a strict co-evolution of circoviruses with their hosts; however, the circoviruses showed about a threefold higher genetic divergence than their hosts.