Structure comparisons of Aedes albopictus densovirus with other parvoviruses.

Parvoviridae is a family of the smallest viruses known with a wide variety of hosts. The capsid structure of the Aedes albopictus C6/36 cell densovirus (C6/36 DNV) at 1.2-nm resolution was obtained by electron cryomicroscopy (cryoEM) and three-dimensional (3D) image reconstruction. Structure comparisons between the C6/36 DNV and other parvoviruses reveal that the degree of structural similarity between C6/36 DNV and the human parvovirus B19 is higher than that between C6/36 DNV and other insect parvoviruses. The amino acid sequence comparisons of structural and non-structural proteins also reveal higher levels of similarity between C6/36 DNV and parvovirus B19 than those between C6/36 DNV and other parvoviruses. These findings indicate that C6/36 DNV is closely related to the human virus B19, and the former might evolve from the human species other than from other insect viruses.

Three-dimensional structure determination of capsid of Aedes albopictus C6/36 cell densovirus.

The three-dimensional structure of capsid of Aedes albopictus C6/36 densovirus was determined to 14-A resolution by electron cryomicroscopy and computer reconstruction. The triangulation number of the capsid is 1. There are 12 holes in each triangular face and a spike on each 5-fold vertex. The validity of the capsid and nucleic acid densities in the reconstructions was discussed.

Genetic, biochemical, and structural characterization of a new densovirus isolated from a chronically infected Aedes albopictus C6/36 cell line.

We report the isolation, sequencing, biochemical, and structural characterization of a previously undescribed virus in a chronically infected Aedes albopictus C6/36 cell line. This virus is identified as a new densovirus under the Densovirinae subfamily of the Parvoviridae based on its biological and morphologic properties as well as sequence homologies, and is tentatively designated A. albopictus C6/36 cell densovirus (C6/36 DNV). Analysis of the 4094 nt of the C6/36 DNV genome revealed that the plus strand had three large open reading frames (ORFs): a left ORF, a right ORF, and a mid-ORF (within the left ORF), whose potential coding capacities are 91.0, 40.8, and 41.2 kDa, respectively. The left ORF likely encodes the nonstructural protein NS-1, which contains NTP-binding and helicase domains. The right ORF likely encodes structural proteins, VP1 and VP2. Our analyses revealed that C6/36 DNV has a similar genomic organization and shares very high homology in nucleotide sequence and amino acid sequences with Aedes aegypti densovirus (AaeDNV) and A. albopictus densovirus (AalDNV), members of the genus Brevidensovirus of the Densovirinae. Similar to other densoviruses, C6/36 DNV has a different genomic organization and no recognizable sequence homology with viruses in the Parvovirinae. The three-dimensional (3D) reconstruction of the C6/36 DNV at 15.6-A resolution by electron cryomicroscopy (cryoEM) revealed distinctive outer surface features not previously seen in other parvoviruses, indicating structural divergence of densoviruses, in addition to its genomic differences, while the inner surface of the C6/36 DNV capsid exhibits features that are conserved among parvoviruses.