Clinical implications of TT virus superinfection in patients with chronic hepatitis C

Torque teno virus in liver diseases: On the way towards unity of view

The review presents the data accumulated for more than 20 years of research of torque teno virus (TTV). Its molecular genetic structure, immunobiology, epidemiology, diagnostic methods, possible replication sites, and pathogenicity factors are described. TTV is a virus that is frequently detectable in patients with different viral hepatitides, in cases of hepatitis without an obvious viral agent, as well as in a healthy population. There is evidence suggesting that biochemical and histological changes occur in liver tissue and bile duct epithelium in TTV monoinfection. There are sufficient histological signs of liver damage, which confirm that the virus can undergo a replicative cycle in hepatocytes. Along with this, cytological hybridization in TTV-infected cells has shown no substantial cytopathic (cell-damaging) effects that are characteristic of pathogenic hepatotropic viruses. Studying TTV has led to the evolution of views on its role in the development of human pathology. The first ideas about the hepatotropism of the virus were gradually reformed as new data became available on the prevalence of the virus and its co-infection with other viruses, including the viruses of the known types of hepatitides. The high prevalence of TTV in the human population indicates its persistence in the body as a virome and a non-pathogenic virus. It has recently been proposed that the level of TTV DNA in the blood of patients undergoing organ transplantation should be used as an endogenous marker of the body’s immune status. The available data show the polytropism of the virus and deny the fact that TTV can be assigned exclusively to hepatitis viruses. Fortunately, the rare detection of the damaging effect of TTV on hepatic and bile duct epithelial cells may be indirect evidence of its conditionally pathogenic properties. The ubiquity of the virus and the variability of its existence in humans cannot put an end to its study.

Hepatitis C -- identifying patients with progressive liver injury

Hepatitis C follows a variable course with some patients developing progressive liver fibrosis, cirrhosis and hepatocellular carcinoma, while others have minimal or no significant liver disease after decades of infection. Studies have identified both host and viral factors associated with disease progression. The importance of general factors such as age at infection, gender, immune status and alcohol consumption has long been recognized; however recently, polymorphisms in a wide array of genes have also been shown to be associated with progressive fibrosis. How specific viral proteins may contribute to disease progression has also been studied. This review highlights what is currently known about the factors associated with progressive liver injury in patients with hepatitis C. A greater understanding of the determinants of disease progression will hopefully lead to improved utilization of existing treatments and ultimately may aid in identification of new therapeutic targets.

Co-infections with hepatitis G and TT virus in patients with chronic hepatitis C in Hungary

The significance of co-infections with novel hepatitis viruses Hepatitis G (GBV-C, HGV) and TT virus (TTV) in chronic hepatitis C is not clear. We determined the prevalence of HGV RNA and TTV DNA in chronic hepatitis C patients and in asymptomatic hepatitis C virus (HCV) carriers, and assessed the influence of these agents on the course of HCV infection. Seventy-seven patients with chronic hepatitis C--50 of them treated with interferon (IFN)--and 33 HCV carriers with normal alanine aminotransferase have been investigated. Previous HBV infection was detected by testing serum HBsAg and aHBc. HGV RNA and TTV DNA were detected by PCR. In the healthy population, the prevalence of anti-HCV was 0.3%, HGV RNA 8.0% and TTV DNA 18.5%. In chronic hepatitis C HGV RNA occurred in 9.09% and TTV DNA in 40.25% of cases. In IFN-treated patients with sustained remission, the frequency of TTV was 20% vs. 45.7% found in non-responders. Among asymptomatic HCV-carriers, the prevalence of HGV RNA was 9.09% and TTV DNA 75.7%. Neither HGV RNA nor TTV DNA had apparent effect on the HCV infection. TTV was detected with the lowest frequency in persons with sustained remission due to IFN, suggesting antiviral effect of IFN on TTV.

Coinfection of TT virus and response to interferon therapy in patients with chronic hepatitis B or C

AIM

To investigate the serum positive percentage of TT virus (TTV) in patients with chronic hepatitis B or C and the response of the coinfected TTV to interferon (IFN) during IFN therapy for chronic hepatitis B and C.

METHODS

We retrospectively studied the serum samples of 70 patients with chronic hepatitis who had received IFN-alpha therapy from January 1997 to June 2000, which included 40 cases of hepatitis B and 30 hepatitis C. All the patients had been followed up for at least 6 months after the end of IFN therapy. The serum TTV DNA was detected using the polymerase chain reaction (PCR) before and every month during the course of IFN treatment.

RESULTS

TTV infection was detected in 15% (6/40) of the chronic hepatitis B group and 30% (9/30) of the chronic hepatitis C group. Loss of serum TTV DNA during IFN therapy occurred in 3 of 6 patients (50%) and 6 of 9 (67%) of hepatitis B and C groups, respectively. Seronegativity of TTV was found all during the first month of IFN therapy in the 9 patients. There was no correlation between the seroconversion of TTV and the biochemical changes of the patients.

CONCLUSION

TTV is not infrequently coinfected in patients with chronic hepatitis B and C in Taiwan, and more than half of the TTV infections are IFN-sensitive. However, the loss of serum TTV DNA does not affect the clinical course of the patients with chronic hepatitis B or C.

In situ polymerase chain reaction detection of transfusion-transmitted virus in liver biopsy

The potential role of transfusion-transmitted virus (TTV) infection in determining liver damage is poorly understood and no information exists about TTV replication within hepatocytes. In this study, we assess TTV in situ PCR in liver tissue. Twenty-one patients with different degrees of liver damage were studied by both serum TTV-DNA detection and in situ TTV PCR analysis and extractive PCR in liver biopsy paraffin sections (FFPE). Extractive PCR and in situ PCR detected TTV-DNA both in serum and liver tissue of five patients. The presence of TTV in serum matched with that found in the liver and TTV sequences were never found independently in liver or serum. Four out of five TTV-DNA-positive patients have not other known cause of liver damage while in one a coinfection from HCV was observed. Our data indicate that in situ PCR appears to be a reliable tool for the detection of TTV-DNA in FFPE, and may help detecting unknown origin of liver damage.

Are hepatitis G virus and TT virus involved in cryptogenic chronic liver disease?

BACKGROUND

Hepatitis G virus can cause chronic infection in man but the role of this agent in chronic liver disease is poorly understood. Little is known about the relation of another newly discovered agent, the TT virus, with chronic liver disease.

AIM

To investigate the rate of infection with hepatitis G virus and TT virus in patients with cryptogenic chronic liver disease.

PATIENTS

A total of 23 subjects with chronically raised alanine transaminase and a liver biopsy in whom all known causes of liver disease had been excluded, and 40 subjects with hepatitis C virus-related chronic liver disease.

METHODS

Evaluation of anti-hepatitis G virus by enzyme immunoassay. Hepatitis G virus-RNA by polymerase chain reaction with primers from the 5' NC and NS5a regions. TT virus-DNA by nested polymerase chain reaction with primers from the ORF1 region. Results. Hepatitis G virus-RNA was detected in 4 out of 23 patients with cryptogenic chronic hepatitis and in 6 out of 40 with hepatitis C virus chronic hepatitis (17.4% vs 15% p=ns). At least one marker of hepatitis G virus infection (hepatitis G virus-RNA and/or anti-hepatitis G virus, mostly mutually exclusive) was present in 6 out of 23 patients with cryptogenic hepatitis and 16 out of 40 with hepatitis C virus liver disease (26. 1% vs 40% p=ns). T virus-DNA was present in serum in 3 subjects, 1 with cryptogenic and 2 with hepatitis C virus-related chronic liver disease. Demographic and clinical features, including stage and grade of liver histology, were comparable between hepatitis G virus-infected and uninfected subjects. Severe liver damage [chronic hepatitis with fibrosis or cirrhosis) were significantly more frequent in subjects with hepatitis C virus liver disease.

CONCLUSIONS

In Southern Italy, hepatitis G virus infection is widespread among patients with chronic hepatitis, independently of parenteral risk factors. Its frequency in subjects with cryptogenic liver disease parallels that observed in hepatitis C virus chronic liver disease, thus ruling out an aetiologic role of hepatitis G virus. TT virus infection is uncommon in patients with cryptogenic or hepatitis C virus-related liver disease who do not have a history of parenteral exposure.

The response of hepatitis C virus and TT virus to high dose and long duration interferon-alpha therapy in naïve chronic hepatitis C patients

To investigate responses of hepatitis C virus (HCV) and TT virus (TTV) to high dose and long duration interferon-alpha (IFN-alpha) therapy (540 million units in 36 weeks) and factors associated with the viral clearance, sera of 165 Taiwanese naïve chronic hepatitis C patients were tested for alanine aminotransferase, HCV RNA levels, HCV genotypes and TTV DNA. With 41.8% of TTV DNA prevalence, TTV viremia was significantly associated with history of blood transfusion (P<0.01). After IFN therapy, HCV complete response was achieved in 60 (36.4%) patients and significantly associated with lower pretreatment levels of HCV RNA (P<0.01) and HCV genotype non-1b (P<0.05). Fifty-three patients with concurrent TTV infection were evaluated for TTV response. TTV sustained clearance was achieved in 24 (48%) patients and significantly associated with loss of TTV DNA at the end point of treatment. In conclusion, concurrent TTV infection is highly prevalent, related to blood transfusion and independent of HCV infection. After high dose and long duration IFN-alpha therapy, HCV and TTV clearance are achieved among more than one-third and around one-half patients. HCV RNA levels and HCV genotypes are predictors for HCV response and no clinical factors are observed to be associated with TTV clearance.

Viral hepatitis

Viral hepatitis constitutes the most common entity seen in hepatology practice. Hepatitis A vaccination is recommended for patients with chronic hepatitis. Both lamivudine and interferon are established therapies against chronic hepatitis B, with other treatments not equally effective. Adefovir dipivoxil is a promising new treatment for lamivudine-resistant hepatitis B mutants. Lamivudine and hepatitis B immunoglobulin are effective in preventing recurrence of hepatitis B after transplantation. The combination of interferon and ribavirin has been shown to be effective for treatment of hepatitis C. Studies support the antiviral, antifibrotic, and antineoplastic effect of interferon therapy. Recurrence of hepatitis C after transplantation has been associated with more rapid progression to cirrhosis. Other major advances in the field of viral hepatitis during the past year are highlighted.