Abstract
BackgroundTorque Teno Virus (TTV) was the first single stranded circular DNA virus to be discovered that infects humans. Although there have been numerous reports regarding the prevalence of TTV from other countries of South Asia, there is severe lack of information regarding its prevalence in Pakistan. Thus the present study compiles the first indigenous report to comprehensively illustrate the incidence of the virus in uninfected and hepatitis infected population from Pakistan. Another aim of the study was to present the sequence of full length TTV genome from a local isolate and compare it with the already reported genome sequences from other parts of the world.MethodsTTV DNA was screened in the serum of 116, 100 and 40 HBV infected, HCV infected and uninfected individuals respectively. Nearly full length genome of TTV was cloned from a HBV patient. The genome sequence was subjected to in-silico analysis using CLC Workbench, ClustalW, ClustalX and TreeView. Statistical analysis was carried out in SPSS v17.0.ResultsOur results report that 89.7%, 90.0% and 92.5% of HBV, HCV patients and healthy control population were positive for TTV infection. TTV genome of 3603 bp was also cloned from a local isolate and given the identity of TPK01. The TTV genome sequence mentioned in this paper is submitted in the GenBank/EMBL/DDBJ under the accession number JN980171. Phylogenetic analysis of TPK01 revealed that the Pakistani isolate has sequence similarities with genotype 23 and 22 (Genogroup 2).ConclusionThe results of the current study indicate that the high frequency of TTV viremia in Pakistan conforms to the reports from other areas of the world, wherever screening of TTV DNA was performed against 5′-UTR of the genome. The high sequence diversity among TTV genome sequences and the high frequency of prevalence makes it harder to study this virus in cellular systems.
Highlights
Torque Teno Virus (TTV) was the first single stranded circular DNA virus to be discovered that infects humans
TTV is unique in many ways, it is the first single stranded circular DNA virus to be discovered that infects humans [3]
Reports regarding prevalence of TTV in blood show immense disparity, from a viremia rate of 2-23% [6] to its frequency in blood rising as high as 90% [7,8]
Summary
Torque Teno Virus (TTV) was the first single stranded circular DNA virus to be discovered that infects humans. TTV is unique in many ways, it is the first single stranded circular DNA virus to be discovered that infects humans [3]. Reports regarding prevalence of TTV in blood show immense disparity, from a viremia rate of 2-23% [6] to its frequency in blood rising as high as 90% [7,8] This variation in the rate of positive detection depends on the choice of target site of amplification in PCR, as the UTRs of the genome are more conserved as compared to the ORFs primers from UTR will crossmatch a large number of genotypes [9] and will give a higher rate of detection
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