Two novel circo-like viruses detected in human feces: complete genome sequencing and electron microscopy analysis.

Abstract

The application of viral metagenomic techniques and a series of PCRs in a human fecal sample enabled the detection of two novel circular unisense DNA viral genomes with 92% nucleotide similarity. The viruses were tentatively named circo-like virus-Brazil (CLV-BR) strains hs1 and hs2 and have genome lengths of 2526 and 2533 nucleotides, respectively. Four major open reading frames (ORFs) were identified in each of the genomes, and differences between the two genomes were primarily observed in ORF 2. Only ORF 3 showed significant amino acid similarities to a putative rolling circle replication initiator protein (Rep), although with low identity (36%). Our phylogenetic analysis, based on the Rep protein, demonstrated that the CLV-BRs do not cluster with members of the Circoviridae, Nanoviridae or Geminiviridae families and are more closely related to circo-like genomes previously identified in reclaimed water and feces of a wild rodent and of a bat. The CLV-BRs are members of a putative new family of circular Rep-encoding ssDNA viruses. Electron microscopy revealed icosahedral (~23 nm) structures, likely reflecting the novel viruses, and rod-shaped viral particles (~65-460 × 21 × 10 nm in length, diameter, and axial canal, respectively). Circo-like viruses have been detected in stool samples from humans and other mammals (bats, rodents, chimpanzees and bovines), cerebrospinal fluid and sera from humans, as well as samples from many other sources, e.g., insects, meat and the environment. Further studies are needed to classify all novel circular DNA viruses and elucidate their hosts, pathogenicity and evolutionary history.

• Authors: Silvana Beres Castrignano, Teresa Keico Nagasse-Sugahara, Jonas José Kisielius, Marli Ueda-Ito, Paulo Eduardo Brandão, Suely Pires Curti
• Journal: Virus research (Virus Res) Vol. 178 Issue 2 Pg. 364-73 (Dec 26 2013) ISSN: 1872-7492 [Electronic] Netherlands
• PMID: 24055464 (Publication Type: Case Reports, Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2013 Elsevier B.V. All rights reserved.

Chemical References

• DNA, Viral

Topics

• Brazil
• Circoviridae (classification, genetics, isolation & purification, ultrastructure)
• Cluster Analysis
• DNA, Viral (chemistry, genetics)
• Feces (virology)
• Female
• Genome, Viral
• Humans
• Microscopy, Electron
• Middle Aged
• Molecular Sequence Data
• Open Reading Frames
• Phylogeny
• Sequence Analysis, DNA
• Sequence Homology, Amino Acid
• Virion (ultrastructure)