Torque Teno Virus (TTV)

Causative Agents

TTV is a non-enveloped small virus containing a circular single-stranded negative-sense DNA genome. TTV has several genotypes and the genome length varies among these genotypes, with an 3.8 kb average. Because of the divergence between the TTV genotypes, the virus classification is controversial, through the literature TTV are classified either into Circoviridae family or into a new floating genus, Anellovirus. TTV is found to be related with fulminant hepatitis and chronic liver disease of unknown etiology. In addition it is assumed that TTV may cause some cryptogenic liver diseases. But the pathogenesis of the TTV remains to be established. (1, 2)

Epidemiology

Torque Teno Virus is very common in populations, 50% prevalent in world population, 100% prevalent in some countries and 10 % of blood donors in UK and U.S. TTV does not cause hepatitis on its own, but it was found 46% of fulminant hepatitis patients and 47% of chronic liver disease of unknown etiology. (2, 3)

Modes of Transmission

Torque Teno Virus is a transfusion transmitted group of viruses. In addition the virus can be transmitted via parenteral, sexual, mother to child and others. In addition, TTV has been detected in saliva, throat swabs, semen, tears, breast milk, hair skin. (4, 5)

Diagnosis

Diagnosis and monitoring of TTV is still under investigation. Because of the variability of the TTV genotypes sequences, detection of the all genotypes with a single method is still being examined. SDS-PAGE and immunoblotting techniques are utilized for TTV detection. On the other hand, PCR based methods are also used for diagnosis of TTV. Especially, Real Time PCR method is the most appropriate, reliable and sensitive technique for diagnosis and genotyping of TTV. The studies in which only a single PCR primer pair was used may have significantly underestimated the true prevalence of TTV.  (1, 6)

Annotated Bibliography

1. 1-Transfusion Transmitted Virus, retrieved from http://olddoc.tmu.edu.tw/chiaungo/profes/TTV.htm
2. 2-TTV — a virus searching for a disease, Cossard Y., Journal of Clinical Virology, Volume 17, Issue 1, Pages 1-3, 2000.
3. 3-Torque Teno Virus (TTV) is Prevalent in Brazilian Non-human Primates and Chickens (Gallus gallus domesticus), Catroxo, M. H. B., Nishiya, A., Sabino, E., Teixeira, P. S., Petrella, S., Milanelo, L., Vieira, J.C.F. and Diaz, R. S., Int. J. Morphol., 26(2):363-372, 2008.
4. 4-Torque Teno Virus (TTV) distribution in healthy Russian population, Vasilyev E.V., Trofimov D.Y., Tonevitsky A.G., Ilinsky V.V., Korostin D.O. and Rebrikov D.V., Virology Journal 2009, 6:134.
5. 5-Sexual Transmission of Transfusion-Transmitted Virus, Rezza G., Zaccarelli M., Giuliani M., Calcaterra S.,Garbuglia A.R., Catalani C., Benvenuti M., Di Carlo A., Antinori A.,  Sexually Transmitted Diseases: May 2001 - Volume 28 - Issue 5 - pp 298-299
6. 6-Comparison of systems performance for TT virus detection using PCR primer sets located in non-coding and coding regions of the viral genome, Biagini P, Gallian P, Attoui H, Cantaloube JF, Touinssi M, de Micco P, de Lamballerie X., J.Clin.Virol. 2001a Aug;22(1):91-99.