The Diversity of Torque Teno Viruses: In Vitro Replication Leads to the Formation of Additional Replication-Competent Subviral Molecules

Abstract

The family Anelloviridae includes torque teno viruses (TTVs), TT-midiviruses (TTMDV), and TT-miniviruses (TTMV), the majority originating from samples of human origin (2,37,39,41,56). The plurality of this family of singlestranded DNA (ssDNA) viruses is reflected not only in DNA sequence, but also in genome size and organization.Infections occur within the first days of life, with close to 100% of infants being infected at 1 year of age. The primary route of infection, however, remains unclear (23,38,48). The ubiquitous nature of TTV infections has hampered efforts to associate it with the pathogenesis of disease (9,15,25,41). A possible etiological association with diseases of the liver (reviewed in reference 36) and respiratory tract (3,30,31,49), hematopoietic malignancies (9,10,13,15,25,53,59), and autoimmune diseases (9, 26, 28, 54) have been reported.The presence of a variety of intragenomic rearranged TTV subviral molecules (TTV) in serum samples and the in vitro transcription of a subviral molecule constituting only 10% of the complete genome initiated the discussion whether TTVs may share similarities to the plantvirus family Geminiviridae (8, 23). Both mono-and bipartite geminiviruses associate with single-stranded DNA satellites to form disease-inducing complexes (16,36,46,47,52,55).Multiple attempts have been made to find a suitable in vitro system for the replication and propagation of TTVs. Replicative forms of its DNA have been demonstrated in bone marrow cells and in the liver (22,42,44,45). Peripheral blood acts as reservoir for TTVs (43), and replication in vivo seems to occur preferably in activated mononuclear cells (27,29,33). Although in vitro transcription has been investigated in a variety of cell lines (18-21, 35, 50), long-term replication leading to virus production has been difficult to achieve (25).More than 200 genomes of TTVs have been isolated. The isolates grouping in the genus Alphatorquevirus (ca. 3.8 kb in size) share very low DNA sequence homology and differ in their genome organizations. A short stretch (71 bp) of the intergenic region is highly conserved among all human TTV isolates (48) and is widely used to demonstrate TTV infection. We have analyzed samples from a broad spectrum of diseases for the presence of TTV DNA by applying PCR amplification of this conserved region (9, 15, 25, 54; E.-M. de Villiers and K. Gunst, unpublished results). Identification of individual TTV types, however, requires the amplification of full-length genomes. We have thus far isolated 93 full-length genomes of TTVs (ca 3.8 kb) from human samples (9, 15, 25; present study). These included samples obtained from healthy individuals and patients with leukemia and lymphoma, rheumatoid arthritis, multiple sclerosis, and kidney disease. The present study describes the in vitro replication and transcription of 12 isolates after initial transfection of the genomic DNA and followed by propagation using frozen infected cells or culture supernatant. Intragenomic rearranged subviral molecules (TTV; i.e.,...

Local Virus Extinctions following a Host Population Bottleneck

“…Anelloviruses, first characterized in 1997 (53), have been reported in a high proportion of human adults (54,55), where they show a very high level of genetic diversity (56)(57)(58). Anelloviruses are under immunological control, since induced or inborn immunodeficiency is associated with increases in viral loads (59)(60)(61)(62)(63).…”

Revisiting the taxonomy of the family Circoviridae: establishment of the genus Cyclovirus and removal of the genus Gyrovirus

“…Similar to CAV, anellovirus genomes have a negative-sense organization with overlapping ORFs with similar relative sizes [3,12,54,79]. In addition, anellovirus and CAV genomes contain GC-rich stretches in non-coding regions where replication is thought to initiate due to the presence of potential stem-loop structures [2,13]. The non-coding or untranslated region of CAV and some anellovirus genomes also contains similar regulatory elements and share high identity within a 36-nt stretch [25,54].…”

Serological Profile of Torque Teno Sus Virus Species 1 (TTSuV1) in Pigs and Antigenic Relationships between Two TTSuV1 Genotypes (1a and 1b), between Two Species (TTSuV1 and -2), and between Porcine and Human Anelloviruses

“…The diversity of anelloviruses was exhibited not only in the nucleotide sequence, genomic size, and animal hosts but also in the presence of a number of intragenomic rearranged subviral molecules in a single individual according to a study of human TTV reported previously (7,20). It was also hypothesized that human TTV should display a high level of antigenic diversity due to extensive genetic heterogeneity (21).…”