Torque teno sus virus

Torque teno sus virus (TTSuV, swine TTV, porcine anellovirus), belonging to the family Anelloviridae, is a group of virus strains that are non-enveloped, with a single-stranded circular DNA genome ranging from 2.6 to 2.8 kb in size.[1] These swine infecting anelloviruses are divided into two genera: genus Iotatorquevirus (TTSuV1) and genus Kappatorquevirus (TTSuV2).[2] Torque Teno Sus Virus has been found in pigs (Sus domesticus) worldwide. TTSuVs are mainly transmitted by fecal-oral route.[3] The prevalence of these viruses is relatively high. For now, there is not known disease caused exclusively by TTSuV. There is the possibility that TTSuV may worsen the progression of other diseases and therefore increase the economic losses for pig industry.[4]

Torque teno sus virus
Informal group of swine viruses
Scientific classification
(unranked): Virus
Realm: incertae sedis
Kingdom: incertae sedis
Phylum: incertae sedis
Class: incertae sedis
Order: incertae sedis
Family: Anelloviridae
Groups included
Cladistically included but traditionally excluded taxa

History

In the nineties, Torque teno virus (TTV) was first found in a Japanese patient. In 2002, the genome of Torque teno sus virus (TTSuV), isolated from swine serum, was first sequenced in Japan.[2]

Taxonomy

TTSuVs belong to the family Anelloviridae. Torque teno sus virus (TTSuV) is subdivided into two genera and four species. The genus Iotatorquevirus (TTSuV1) includes TTSuV1a and TTSuV1b, and the genus Kappatorquevirus (TTSuVk2) comprises TTSuVk2a and TTSuVk2b.[5]

Structure

Torque teno sus virus (TTSuV) is a non‐enveloped virus with a circular single‐stranded DNA genome of negative polarity ranging from 2.6 to 2.8 kb in size.[2][1] The genome has three open reading frames, ORF1 (capsid), ORF2 and ORF3 and a highly conserved untranslated region.[2] Open reading frames (ORFs) encode approximately 500 (ORF1), 100 (ORF2) and 200 (ORF3) aminoacids.[2]

Viral spread

The virus is transmitted mainly by the fecal-oral route. The virus has been detected in a number of tissues including liver, brain, sera, semen, nasal secretion, lymph node, heart, liver, bone marrow, lung or spleen.[3] It was confirmed that the TTSuV can be detected also in bile.[4]

TTSuV is ubiquitous in pig farms worldwide. The prevalence varies between 31 and 90 % for TTSuVk2 and between 17 and 100 % for TTSuV1. Generally, the prevalence increases with the age of animals.[6][4]

Clinical

TTSuV is commonly detected in healthy pigs. For now, there is not known disease caused exclusively by TTSuV. However, the co-infection with other swine pathogens is described. Probably, TTSuV could trigger the development of certain diseases or increase the severity of diseases.[5] Studies have shown that TTSuV could serve as a trigger in the pathogenesis of post-weaning multisystemic wasting syndrome (PMWS) caused by Porcine circovirus type 2 (PCV2).[7] However, it is still unclear whether the co-infection contributes to the PMWS or vice-versa.[8]

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References
  1. Singh P, Ramamoorthy S (August 2016). "Lack of strong anti-viral immune gene stimulation in Torque Teno Sus Virus1 infected macrophage cells". Virology. 495: 63–70. doi:10.1016/j.virol.2016.04.028. PMC 4912913. PMID 27179346.
  2. Okamoto H, Takahashi M, Nishizawa T, Tawara A, Fukai K, Muramatsu U, Naito Y, Yoshikawa A (June 2002). "Genomic characterization of TT viruses (TTVs) in pigs, cats and dogs and their relatedness with species-specific TTVs in primates and tupaias". The Journal of General Virology. 83 (Pt 6): 1291–7. doi:10.1099/0022-1317-83-6-1291. PMID 12029143.
  3. Rogers AJ, Huang YW, Heffron CL, Opriessnig T, Patterson AR, Meng XJ (December 2017). "Prevalence of the Novel Torque Teno Sus Virus Species k2b from Pigs in the United States and Lack of Association with Post-Weaning Multisystemic Wasting Syndrome or Mulberry Heart Disease" (PDF). Transboundary and Emerging Diseases. 64 (6): 1877–1883. doi:10.1111/tbed.12586. hdl:20.500.11820/7b9c4021-82e0-4e74-8378-b623e8ca54fc. PMID 27878979.
  4. Monini M, Vignolo E, Ianiro G, Ostanello F, Ruggeri FM, Di Bartolo I (December 2016). "Detection of Torque Teno Sus Virus in Pork Bile and Liver Sausages". Food and Environmental Virology. 8 (4): 283–288. doi:10.1007/s12560-016-9249-1. PMID 27294982.
  5. Nieto D, Martínez-Guinó L, Jiménez-Melsió A, Segalés J, Kekarainen T (October 2015). "Development of an indirect ELISA assay for the detection of IgG antibodies against the ORF1 of Torque teno sus viruses 1 and 2 in conventional pigs". Veterinary Microbiology. 180 (1–2): 22–7. doi:10.1016/j.vetmic.2015.08.023. PMID 26358897.
  6. de Menezes Cruz AC, Silveira RL, Baez CF, Varella RB, de Castro TX (November 2016). "Clinical aspects and weight gain reduction in swine infected with porcine circovirus type 2 and torque teno sus virus in Brazil". Veterinary Microbiology. 195: 154–157. doi:10.1016/j.vetmic.2016.09.012. PMID 27771061.
  7. Zheng S, Shi J, Wu X, Peng Z, Xin C, Zhang L, et al. (April 2018). "Presence of Torque teno sus virus 1 and 2 in porcine circovirus 3-positive pigs". Transboundary and Emerging Diseases. 65 (2): 327–330. doi:10.1111/tbed.12792. PMID 29285888.
  8. Ozawa M, Kawabata T, Okuya K, Nagano K, Kanda T, Kanazawa N, Tsukiyama-Kohara K, Taneno A, Deguchi E (December 2015). "Full genome sequences of torque teno sus virus strains that coinfected a pig with postweaning multisystemic wasting syndrome in Japan: implications for genetic diversity". Archives of Virology. 160 (12): 3067–74. doi:10.1007/s00705-015-2593-x. PMID 26335893.
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