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

TT virus (TTV) lacks obvious pathogenicity; almost all of the infected host s are symptom-free. A possibility remains, however, that certain strains ca n cause liver disease while most others are non-pathogenic. Genotypes 1a an d 1b have been proposed to contain such pathogenic strains. To test this po ssibility, we constructed a PCR system capable of detecting TTV of the 1a a nd 1b genotypes differentially from the other genotypes, and compared the f requencies of these genotypes between patients with liver disease of unknow n 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) 2n d-round PCR, starting from the 3.2-kb amplicon, for a similar to 280-nt fra gment by use of genotype 1-specific primers; and iii) digestion of the simi lar to 280-nt amplicon with MboI and BanI to discriminate between la and Ib . Eventually, 40 (95%) of the patients and 47 (94%) of the controls were po sitive for the 3.2-kb amplicon, and the 1a, 1b, 1a+1b, and non-1 genotypes of TTV were found in 2 (5%) vs 4 (9%), 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 hypothesi s that the genotype 1 of TTV may be more closely associated with liver dise ase than other genotypes was not supported by this study.