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of TTV DNA by applying PCR amplification of this conserved region (9, 15, 25, 54; E.-M. de Villiers and K. Gunst, unpublished results).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.,...

Viral infections have been implicated in the pathogenesis of multiple sclerosis. Epstein-Barr virus (EBV) has frequently been investigated as a possible candidate and torque teno virus (TTV) has also been discussed in this context. Nevertheless, mechanistic aspects remain unresolved. We report viral replication, as measured by genome amplification, as well as quantitative PCR of two TTV-HD14 isolates isolated from multiple sclerosis brain in a series of EBV-positive and -negative lymphoblastoid and Burkitt's lymphoma cell lines. Our results demonstrate the replication of both transfected TTV genomes up to day 21 post transfection in all the evaluated cell lines. Quantitative amplification indicates statistically significant enhanced TTV replication in the EBV-positive cell lines, including the EBV-converted BJAB line, in comparison to the EBV-negative Burkitt's lymphoma cell line BJAB. This suggests a helper effect of EBV infections in the replication of TTV. The present study provides information on a possible interaction of EBV and TTV in the etiology and progression of multiple sclerosis.