TTV infection in patients with acute hepatitis of defined aetiology and in acute non-A-E hepatitis

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.

Acute liver failure

Acute liver failure is a rare disorder with high mortality and resource cost. In the developing world, viral causes predominate, with hepatitis E infection recognised as a common cause in many countries. In the USA and much of western Europe, the incidence of virally induced disease has declined substantially in the past few years, with most cases now arising from drug-induced liver injury, often from paracetamol. However, a large proportion of cases are of unknown origin. Acute liver failure can be associated with rapidly progressive multiorgan failure and devastating complications; however, outcomes have been improved by use of emergency liver transplantation. An evidence base for practice is emerging for supportive care, and a better understanding of the pathophysiology of the disorder, especially in relation to hepatic encephalopathy, will probably soon lead to further improvements in survival rates.

Epidemiological characteristics and clinical manifestations of acute non-A-E hepatitis

Background/Aim. Acute non-A, non-B, non-C, non-D, non-E hepatitis (non-A-E AH) is an acute disease of the liver of unknown etiology for which one or more new, so far undetected, hepatotropic viruses may be responsible. The frequency of non-A-E AH ranges from 3.8% to 33.9%, and therefore it has a significant place within current infectology and hepatology. The aim of our study was to establish the frequency, clinical and biochemical characteristics, natural course and outcome of non-A-E AH and compare them with control groups affected by acute viral hepatitis A, B and C. Methods. This descriptive-analytic prospective study included 31 patients with non-A-E AH treated at the Institute of Infectious and Tropical Diseases, Clinical Center of Serbia, Belgrade, from 2003 to 2008. They were followed up during the period not less than 6 months. The controls involved randomly selected patients, treated at the same time with a definite diagnosis of acute viral hepatitis A, B and C. Statistical data analysis used Mann-Whitney Utest, Student's t-test and variance analysis. The value of p < 0.05 was considered statistically significant. Results. The frequency of non-A-E AH was 7.6%. Almost no difference was found between sexes (male/female ratio was 1 : 1.07); it was developed in all age groups, with the highest incidence in the middle age (mean age was 38.32 ? 15.3 years). It appeared equally throughout the whole year. Out of risk factors, inoculation risk was predominant (before all, dental interventions), mostly involving urban population living in comfortable conditions. The duration of incubation varied much ranging from 20 to 180 days (median 60 days). By clinical course, moderate and icteric forms were most common, mostly corresponding to acute hepatitis A and C. On the other hand, by duration of the disease (mean duration was 67.1 ? 27.1) and chronic transformation, non-A-E AH resembled to acute hepatitis B. Progression to chronicity was recorded in 9.68% of the patients. There was no fulminant neither cholestatic form of the disease. Conclusion. Based on the results obtained in this study, it is probable that there are some so far undetected primary hepatotropic viruses in our environment.

Performance of three PCR methods targeting different regions of viral genome for the detection of TTV in Non A-E hepatitis, chronic B and C hepatitis and healthy blood donors

TT virus (TTV) was suggested to be the etiologic agent for non A-E hepatitis but this could not yet be proven due to high detection rates not only in hepatitis but also in healthy persons and sensitivity differences of PCR methods employed. The aim of this study was to evaluate TTV DNA positivity in non A-E hepatitis cases, chronic HBV and HCV hepatitis cases and healthy blood donors via PCR systems that target all regions of the viral genome used for viral detection. 23 non A-E hepatitis, 28 chronic HCV, 21 chronic HBV cases and 56 healthy blood donors were included in the study and evaluated by PCR protocols that target 5′-UTR, 3′-UTR and N22 (ORF1) regions. As a result, 3′-UTR and 5′-UTR PCR had comparable detection rates that were higher than N22 PCR. Differences in detection rates among study groups were not statistically significant for any PCR method. Hepatic enzyme levels of the patients were not correlated with the presence of TTV DNA. Detection rate was significantly higher for Non A-E hepatitis group when positivity rates from all methods were combined. These results suggest an alteration of viral genotypes in Non A-E hepatitis which might be associated with pathogenesis.

TTV infection in children born to mothers infected with TTV but not with HBV, HCV, or HIV

The TT virus (TTV) was isolated recently from the serum of a patient with post-transfusion hepatitis. TTV infection is widespread in the general population, and its prevalence increases continuously with age. The pathogenic role of TTV in liver disease remains controversial, and the source of transmission is still unclear. We investigated the pathogenicity and epidemiology of TTV infection in infants born to TTV DNA-positive mothers. Enrolled in this study were 22 mother-child pairs testing negative for antibodies to hepatitis B, hepatitis C, and the human immunodeficiency viruses (HIVs). The children were followed for 30 months after birth. Serum TTV DNA was detected by N22-PCR, and the PCR products were cloned and sequenced. The prevalence of TTV infection in children increased with age. Of the 22 children, 13 (59%) became positive for TTV DNA during the follow-up period. Of these 13 children, 6 (46%) had elevated levels of serum alanine aminotransferase (ALT), although the elevations were transient and mild. TTV viremia was not associated significantly with the abnormal ALT levels. Children with TTV viremia developed neither severe liver disease nor fulminant hepatitis. Phylogenetic analysis showed that, in 11 (85%) of the 13 pairs, the mother and child had the same genotype at the first PCR-positive time point. Among those 11 mother-child pairs, 6 (55%) had identical TTV nucleotide sequences. However, the genotype of predominant clones changed in 5 (50%) of 10 children who were positive for TTV DNA at two or more time points during the follow-up period. In conclusion, this study did not provide evidence that TTV infection is related to liver disease in children. Although the main source of TTV infection in children is presumed to be their mothers, transmitted via non-parenteral routes in the course of daily contact, intrafamilial carriers may also be sources of TTV infection.

Epidemiological characteristics, risk factors, and clinical manifestations of acute non-A-E hepatitis

A substantial proportion of acute non-A, non-B hepatitis was of unknown etiology and was termed non-A-E hepatitis. Analysis of the clinical features is needed while attempting to identify the causative agent(s). In this study, the clinical and biochemical features of 53 patients who were admitted to hospital with acute non-A-E hepatitis were compared with a cohort of patients with acute hepatitis C (n = 70) and E (n = 5). In acute non-A-E hepatitis, the sex ratio was 34:19, and ages ranged from 21 to 76 years (median 49). Biochemical tests [median (range)] revealed albumin 3.6 (2.2-4.4) g/dl, AST 714 (193-2311) U/l, ALT 896 (310-3,000) U/l, bilirubin 11.2 (0.9-36.3) mg/dl, and prothrombin time > 1.1 (0-11.5) seconds. No patients reported parenteral exposures or household contact. Forty-five percent had severe hepatitis (i.e., albumin < 3 g/dl, bilirubin > 15 mg/dl or prothrombin time > 3 sec), including 3% with fulminant hepatitis. Chronic evolution was noted in 7%. These features were similar to those of hepatitis C or E, except for a significantly high frequency of parenteral exposures (20%), household contact (16%), and chronicity (70%) in hepatitis C. In conclusion, there is no obvious parenteral risk factor identified in acute non-A-E hepatitis. Clinical severity is similar to that of hepatitis C at least in hospitalized patients, but the rate of chronic evolution is much lower.