Molecular Properties, Biology, and Clinical Implications of TT Virus, a Recently Identified Widespread Infectious Agent of Humans

Abstract

TT virus (TTV) was first described in 1997 by representational difference analysis of sera from non-A to non-G posttransfusion hepatitis patients and hence intensively investigated as a possible addition to the list of hepatitis-inducing viruses. The TTV genome is a covalently closed single-stranded DNA of approximately 3.8 kb with a number of characteristics typical of animal circoviruses, especially the chicken anemia virus. TTV is genetically highly heterogeneous, which has led investigators to group isolates into numerous genotypes and subtypes and has limited the sensitivity of many PCR assays used for virus detection. The most remarkable feature of TTV is the extraordinarily high prevalence of chronic viremia in apparently healthy people, up to nearly 100% in some countries. The original hypothesis that it might be an important cause of cryptogenic hepatitis has not been borne out, although the possibility that it may produce liver damage under specific circumstances has not been excluded. The virus has not yet been etiologically linked to any other human disease. Thus, TTV should be considered an orphan virus

Molecular mimicry and immunomodulation by the HRES-1 endogenous retrovirus in SLE

“…TTV was originally named after the initials of first patient TT, then transfusion-transmitted, and recently renamed "torque teno" virus [73]. Due to the high degree of genomic variability of the putative coding regions [74] and difficulties in expression of full-length TTV protein for antibody testing [75,76], the diagnosis of TTV infection has been dependent on PCR detection of viral DNA using primers specific for the noncoding regions [77]. TTV DNA was detected in 120/211 SLE patients and 66/199 healthy control donors (p < 0.0001).…”

First description of Adenovirus, Enterovirus, Rotavirus and Torque teno virus in water samples collected from the Arroio Dilúvio, Porto Alegre, Brazil

“…The most commonly studied species of enteric viruses are enterovirus (EV), adenovirus (AdV), genogroup A rotaviruses (GARV), hepatitis A and E viruses and more recently, norovirus (Leclerc et al, 2002;Abdel-Moety et al, 2008;Gibson et al, 2011). Similarly to enteric viruses, Torque teno virus (TTV), an emerging virus discovered from hepatitis patients and healthy persons as well, has a similar behaviour: it is relatively resistant to heat inactivation and also excreted by the fecal route (Bendinelli et al, 2001).…”

Quantitative Detection of Porcine Torque Teno Virus in Porcine Circovirus-2–Negative and Porcine Circovirus–Associated Disease-Affected Pigs

“…16 After finding the causative viral agent, several studies have been conducted on the biological characteristics, epidemiology, and pathogenicity of TTV in hepatitis and its relation with other diseases in humans. 4 Results of previous studies determined that human TTV possesses a quite stable genome within the same genogroup, shares low nucleotide sequence identity with different genogroups, and has a high prevalence in the human population, which arouses suspicion of possible relationships between TTV and other diseases. 1,7,11 Those previous studies implied a possible clinical implication in TTV, but human TTV and Torque teno mini virus (TTMV) are often referred to as orphan viruses because they are not linked to any specific disease or syndrome.…”