Torque Teno Mini virus
Torque Teno mini virus (TTMV) belongs to the Betatorquevirus genus of the relatively new family, Anelloviridae. There are 12 species labelled Torque Teno mini virus 1-12.[1] TTMV is the type species of Betatorquevirus and is one of the three human anelloviruses (Torque Teno virus, Torque Teno midi virus, Torque Teno mini virus).
The previous isolate name of TTMV is “TT virus-like mini virus”, abbreviated “TLMV”.[2]
Initial Discovery
The discovery of TTMV, like the original Torque Teno virus (TTV) isolate, was accidental. After TTV was isolated in 1997 from a Japanese patient, primers were created to study TTV in more detail. TTV-specific primers used in PCR of human plasma samples yielded sequences that partially matched that of TTV, but were noticeably shorter.[1][3] TTV was eventually understood to have a genome of 3.6-3.9 kb, while TTMV has a genome of 2.8-2.9 kb. Another TT-like virus later isolated in 2007, Torque teno midi virus or TTMDV, has a genome of 3.2 kb.[3]
Genome and Capsid
TTMV shares similar morphologic features with the other human anelloviruses. The capsid has a T=1 icosahedral symmetry.[1] The virion does not have a lipid envelope and is thus "naked", making it an extremely simple virus. It is estimated that the virion is a little less than 30 nm in diameter.[1][3]
The genome is circular and made of single-stranded DNA of negative polarity. It is 2.86-2.91 kilobases long.[1] Anelloviruses are known for having 3 or 4 overlapping, nested open reading frames; TTMV has 3 ORF's that overlap.[1][4] ORF-2 and ORF-3 overlap with ORF-1 at opposite ends. For TTMV, ORF-1 is about 663 residues and ORF-2 is about 91 residues long.[1] There is a highly conserved 130-nt region just downstream of the TATA box.[3]
Phylogeny & Spread
TTMV is highly divergent.[1][3] The first phylogenetic tree created from TTMV genomic sequences revealed a large cluster of strains; ORF-1 had divergences of over 42% at the nucleotide level and over 67% at the amino acid level.[1]
TTMV is also highly prevalent, like other human anelloviruses. Subsequent research after its discovered has yielded the prevalence of TTMV DNA among blood donors to be 48%–72%.[3] It can likely infect a wide range of tissues, as it has been isolated from various body fluids and tissues, including saliva, feces, plasma/serum, PBMCs, bone marrow, spleen, pancreas, kidneys, nervous tissue, lymph nodes, semen, and cervical swabs.[1][3] Its exact transmission mechanism is unknown, but is thought to be possible by blood-borne, sexual, fecal-oral, and respiratory routes.[1]
Recent studies have shown that humans can have multiple infections of TT viruses.[3][4]
Pathogenesis
Though TTVs are potentially associated with disease, TTMV is not currently known to cause any human disease.[1] The pathogenicity of TTVs has been debated since its discovery.
See also
References
- 1 2 3 4 5 6 7 8 9 10 11 12 Spandole, Sonia; Cimponeriu, Dănuţ; Berca, Lavinia Mariana; Mihăescu, Grigore (April 2015). "Human anelloviruses: an update of molecular, epidemiological and clinical aspects". Archives of Virology. 160 (4): 893–908. doi:10.1007/s00705-015-2363-9.
- ↑ Biagini, P (2009). "Classification of TTV and related viruses (Anelloviruses)". Current Topics in Microbiology and Immunology. 331: 21–33.
- 1 2 3 4 5 6 7 8 Okamoto, H (2009). "History of discoveries and Pathogenicity of TT viruses". Current Topics in Microbiology and Immunology. 331: 1–20.
- 1 2 Zhang, Yu (May 6, 2016). "A novel species of torque teno mini virus (TTMV) in gingival tissue from chronic periodontitis patients". Scientific Reports. 6 (26739). doi:10.1038/srep26739.