Genotypes of TT virus (TTV) compared between liver disease patients and healthy individuals using a new PCR system capable of differentiating 1a and 1b types from others*

Abstract

TT virus (TTV) lacks obvious pathogenicity; almost all of the infected hosts are symptom-free. A possibility remains, however, that certain strains can cause liver disease while most others are non-pathogenic. Genotypes 1 a and 1 b have been proposed to contain such pathogenic strains. To test this possibility, we constructed a PCR system capable of detecting TTV of the 1 a and 1 b genotypes differentially from the other genotypes, and compared the frequencies of these genotypes between patients with liver disease of unknown etiology (n=42) and healthy individuals (n=50). The assay comprised 3 steps: i) PCR to amplify a 3.2-kb fragment using universal primers; ii) 2nd-round PCR, starting from the 3.2-kb amplicon, for a approximately 280-nt fragment by use of genotype 1-specific primers; and iii) digestion of the approximately 280-nt amplicon with MboI and BanI to discriminate between 1 a and 1 b. Eventually, 40 (95%) of the patients and 47 (94%) of the controls were positive for the 3.2-kb amplicon, and the 1 a, 1 b, 1 a+1 b, and non-1 genotypes of TTV were found in 2 (5%) vs 4 (9 percent), 5 (13%) vs 4 (9%), 1 (3%) vs 1 (2%) and 32 (80%) vs 38 (81%) of the 40 patients and 47 controls, respectively: the distribution was almost identical between the two groups. The hypothesis that the genotype 1 of TTV may be more closely associated with liver disease than other genotypes was not supported by this study.

The Association of Prevalence and Genotypes of Torque Teno Virus (TTV) Among Chronic Hepatitis B and C Patients in Ahvaz, 2012

“…People who are exposed to blood and blood products can be co-infected with multiple strains of TTV (7). TTV is frequently separated from patients with acute or chronic hepatitis.…”

TT Virus Infection in Israeli Patients with Fulminant Hepatic Failure

“…Similarly to our data, TTV infection was found to be common among patients with liver disease in North America, with a prevalence of 27% in patients with idiopathic FHF [12]. TTV DNA was also shown to be present in 47% of idiopathic FHF patients in Japan [7]. Only 1 of our 7 idiopathic FHF patients with TTV DNA in the serum had a history of transfusion prior to sampling.…”

“…Although TTV was suspected to encompass hepatotropism [8], the pathogenesis of TTV infection and its clinical consequences are not yet clearly defined. However, there is now ample evidence to indicate that TTV is very common in healthy individuals and is unlikely to be proven responsible for cases of idiopathic hepatitis [2, 3, 4, 5, 6, 7, 8]. In this study, we sought to determine the prevalence of TTV infection in patients with fulminant hepatic failure (FHF).…”

“…Several reports revealed the presence of TTV DNA not only in patients with a broad spectrum of hepatic disorders such as acute hepatitis, FHF, chronic hepatitis and cryptogenic cirrhosis but also in apparently healthy persons and blood donors [2, 3, 4, 5, 6, 7]. Although TTV was suspected to encompass hepatotropism [8], the pathogenesis of TTV infection and its clinical consequences are not yet clearly defined.…”

Clinicopathological study on TTV infection in hepatitis of unknown etiology

“…The infection rate of TTV DNA varies largely in healthy population and patients with liver diseases, but generally, it is higher in patients than in healthy donors [7,[23][24][25][26] . The discovery of TTV once put a light on the etiological diagnoses of hepatitis cases of unknown etiology, unfortunately, the pathogenicity and clinical significance of TTV remain doubtful at this time [25,[27][28][29] . To clarify the infection status, replication place, pathogenicity and clinical significance of TTV among hepatitis cases, especially in patients of unknown etiology, we conducted the research to test TTV DNA comprehensively among large-sample cases of hepatitis.…”