Date: Sun, 2 Jun 2013 05:10:59 -0400 (EDT) From: ProMED-mail <promed@promed.isid.harvard.edu> Subject: PRO/AH/EDR> Hepatitis non-A/B/C/D/E: parvovirus-like hybrid
HEPATITIS NON-A/B/C/D/E: PARVOVIRUS-LIKE HYBRID
The authors report the identification of a virus, designated NIH-CQV, in patients with non-A/B/C/D/E hepatitis. Phylogenetically this virus appears to lie at the interface of parvoviruses and circoviruses. The genome of NIH-CQV has no homology to any known hepatitis viruses. NIH-CQV has a small, compact linear DNA genome with 2 tandemly arranged major ORFs encoding Rep and CP proteins, respectively, and a pair of ITRs at the left and right ends of the genome. NIH-CQV represents a deeply rooted lineage between 2 groups: the human and animal parvoviruses and the insect parvoviruses. Thus, NIH-CQV appears to be a parvovirus-like virus.
However, NIH-CQV also has features shared by members of the Circoviridae family. NIH-CQV exhibits ambisense encoding of sequences a feature shared with members of the Circoviridae family. Therefore, NIH-CQV appears to be a “hybrid” virus, perhaps formed by interfamilial recombination between a parvovirus and a circovirus. This idea is supported further by whole-proteome phylogenetic analysis, which showed NIH-CQV located between the families Parvoviridae and Circoviridae. Parvoviruses (family Parvoviridae) and circoviruses (family Circoviridae) are both ssDNA viruses that infect a wide variety of animal species, including mammals, birds, and insects. However, although horizontal gene transfer and high mutation rates have been documented in these viruses, cross-species viral transfers resulting from interfamilial recombination and leading to a infection in the new host species are not common.
Furthermore NIH-CQV exhibited remarkable genetic heterogeneity within patients, indicating the presence of closely related variants or quasispecies in NIH-CQV-infected individuals. For hepatitis viruses C and E, diversification of quasispecies during infection is driven by the interaction between the viruses and host immune response and may be associated with different clinical outcomes. With a limited number of serial samples from a single individual, the authors were unable to conclude whether quasispecies dynamics of NIH-CQV in patients correlated with disease.