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Analysis of the entire genomes of fifteen torque teno midi virus variants classifiable into a third group of genus Anellovirus.

Division of Virology, Department of Infection and Immunity, Jichi Medical University School of Medicine, Tochigi, Japan.
Archives of Virology (Impact Factor: 2.28). 02/2007; 152(11):1961-75. DOI: 10.1007/s00705-007-1046-6
Source: PubMed

ABSTRACT Recently, we identified a novel human virus with a circular DNA genome of 3.2 kb, tentatively designated as torque teno midi virus (TTMDV), with a genomic organization resembling those of torque teno virus (TTV) of 3.8-3.9 kb and torque teno mini virus (TTMV) of 2.8-2.9 kb. To investigate the extent of genomic variability of TTMDV genomes, the full-length sequence was determined for 15 TTMDV isolates obtained from viremic individuals in Japan. The 15 TTMDV isolates comprised 3175-3230 bases and shared 67.0-90.3% identities with each other, and were only 68.4-73.0% identical to the 3 reported TTMDV isolates over the entire genome. TTMDV possessed a genomic organization with four open reading frames (ORF1-ORF4) with characteristic sequence motifs and stem and loop structures with high GC content, similar to TTV and TTMV. The total of 18 TTMDV genomes differed by up to 60.7% from each other in the amino acid sequence of ORF1 (658-677 amino acids), but segregated phylogenetically into the same cluster, which was distantly related to the TTVs and TTMVs. These results indicate that TTMDV with a circular DNA genome of 3.2 kb, has an extremely high degree of genomic variability, and is classifiable into a third group in the genus Anellovirus.

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    • "TTV is very often detected in blood; the prevalence of TTV DNA in the blood of healthy individuals is approximately 70-90% [119]. A single TTV infection may persist for years and cause chronic viremia [120] [121] [122]. Simultaneous infections by different TTV variants may also occur. "
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    • "ORF2 encodes 111 amino acids and shares no amino acid sequence identity with proteins in GenBank. ORF2 lacks the motif W-X 7 -H-X 3 -C- X 1 -C-X 5 -H that is conserved among TTVs, TTMVs and TTMDVs (Hijikata et al., 1999; Ninomiya et al., 2007, 2009; Okamoto et al., 2000; Takahashi et al., 2000). ORF3 encodes 204 amino acids, and shares weak amino acid sequence identity (16 %) with ZcAV ORF3 only, indicating that SealAV could be more closely related to ZcAV than to Fig. 1. "
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    • "In the case of TTMV, full-length genomic sequences of 17 isolates have been determined thus far, and four highly divergent genetic groups have been proposed (Biagini et al., 2001b, 2007; Okamoto et al., 2000b; Takahashi et al., 2000). Upon analysing more TTMDV sequences, we noticed that they formed a large swarm of isolates differing in length (3175–3230 nt) and in sequence (33 % divergence over the entire genomic sequence) (Ninomiya et al., 2007b). Our previous study using a newly developed PCR method revealed high frequencies of viraemia with TTV (99.2 %), TTMDV (82.4 %) and TTMV (89.7 %) among apparently healthy subjects of 1–81 years of age. "
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