Clinical & molecular characterization of human TT virus in different liver diseases

TT virus (TTV) is a newly discovered non-enveloped, single stranded DNA virus of high genotypic variability, found frequently in patients with acute or chronic hepatitis of non A-G aetiology. This study was carried out to look for the presence of TTV and its genotypes in patients with different types of liver diseases from northern India.

A total of 262 serum samples from patients of acute viral hepatitis (AVH; n=72), fulminant hepatic failure (FHF; n=49), chronic active hepatitis (CAH; n=93) and liver cirrhosis (LC; n=48), were analyzed for hepatitis A-G viral markers. TTV DNA was detected in all cases by nested polymerase chain reaction (PCR) using the primers from N22 and untranslated (UTR) region. TTV-DNA was also tested in 150 volunteer blood donors. Direct nucleotide sequencing of N22 amplicons were carried out to look into the prevalent TTV genotypes.

TTV-DNA was detected in 73.6, 59.2, 21.5 and 29.1 per cent cases with AVH, FHF, CAH and cirrhosis, respectively. In AVH and FHF groups, TTV showed co-infection with all A-G hepatitis cases whereas in CAH and cirrhosis groups, TTV co-infection observed with HBV, HCV and HGV. TTV-DNA was detected in 45.3 per cent volunteer blood donors. No statistically significant difference was observed amongst the mean liver function profile of UTR PCR positive and negative cases in different liver disease groups except AVH cases, in whom the various biochemical parameters between TTV positive and TTV negative patients were marginally significant. However, no significant evidence of biochemical or histological deterioration of the liver was observed in TTV positive cases amongst FHF, CAH and cirrhosis. Predominance of genotype 1a was observed in all the cases from north India.

TTV is a frequent virus isolated from patients with various types of liver diseases as well as in healthy individuals from northern India. TTV has no effect on biochemical markers of associated liver diseases. Genotype 1a was the most predominant type in different liver disease groups. The occurrence of TTV did not further influence the course of the disease.