Transfusion transmitted virus: A review on its molecular characteristics and role in medicine

The present review gives an updated overview of transfusion transmitted virus （TTV）, a novel agent, in relation to its molecular characteristics, epidemiological features, modes of transmission, tissue tropism, pathogenesis, role in various diseases and its eradication from the body. TTV, a DNA virus, is a single stranded, non-enveloped, 3.8 kb long DNA virus with a small and covalently closed circular genome comprising 3852 bases. It was tentatively designated Cirdnoviridae virus.TTV genome sequence is heterogeneous and reveals the existence of six different genotypes and several subtypes. TTV has been reported to transmit not only via parenteral routes, but also via alternate routes. This virus has been detected in different non-human primates as well. At present, TTV is detected by polymerase chain reaction （PCR） with no other available diagnostic assays. It shows its presence globally and was detected in high percent populations of healthy persons as well as in various disease groups. Initially it was supposed to have strong association with liver disease; however, there is little evidence to show its liver tropism and contribution in causing liver diseases. It shows high prevalence in hemodialysis patients, pointing towards its significance in renal diseases. In addition,TTV is associated with several infectious and non-infectious diseases. Though, its exact pathogenesis is not yet clear, TTV virus possibly resides and multiplies in bone marrow cells and peripheral blood mononuclear cells （PBMCs）. Recently, attempts have been made to eradicate this virus with interferon treatment. More information is still needed to extricate various mysteries related to TTV.

Transfusion-transmitted virus co-infection in other types of hepatitis and its genotypes

OBJECTIVE: To identify the influence of transfusion transmitted virus (TTV) co-infection in other virus infected patients and its genotypes. METHODS: A conservative sequence of ORFl in the TTV genome was selected as primers and TTV DNA was measured in students and other hepatitis patients by using microplate nucleic acid hybridization and ELISA. The results were statistically analyzed. Nucleotide sequence of divergence >50% was used as color probe for distinguishing TTV genotypesⅠorⅡ. RESULTS: TTV DNA was detected in the sera from 2 (3.3%) of 60 students, 2 (14.3%) of 14 patients with non A-non E hepatitis, 6 (12%) of 50 patients with chronic hepatitis B, and 4 (16%) of 25 patients with liver cirrhosis, respectively. Statistical difference was observed between the patient group and the student group (P<0.05), but no significant difference in age, gender, serum ALT levels and TBiL between TTV DNA positive and negative patients (P>0.05). TTV genotype Type Ⅰ was by far the most frequent viral genotype (66.7%), followed by type Ⅱ (25%), and mixed infection (8.3%). CONCLUSIONS: These results suggest that the routes of TTV infection may be similar to those of HBV and HCV, and concurrent infection with HBV, HCV are common. TTV co-infection could not affect the clinical features of patients with liver diseases and the pathological process. TTV is not a main causative factor for patients with non A-non E hepatitis. Further study is needed to clarify the role of TTV in patients with non A-non E hepatitis.

THE INVESTIGATION OF DIFFERENT POPULATION'S TRANSFUSION-TRANSMITTED VIRUS-DNA IN SHAANXI PROVINCE

Objective To investigate transfusion transmitted virus (TTV) infection among population of different groups in Shaanxi Province.Methods A nested polymerase chain reaction (PCR) with primers from ORF1 of TTV genome was established to detect TTV DNA in serum of the patients.Results TTV DAN was detected in the sera of 3 of 50 cases of general population(6%), 2 of 30 cases of vocational blood donors(6.7%),21 of 97 cases with Type B hepatitis(21.6%),9 of 35 cases of Type C hepatitis (25.7%),and 23 of 40 cases with non A^non G hepatitis(57 5%).Conclusion There is TTV infection among general population in Shaanxi Province.TTV may be an important agent to cause non A^non G hepatitis .And the patients with HBV or HCV can have overlapping TTV infection.

Clinical Characteristics of Transmitted Transfusion Virus Infection in Children

Clinical characteristics of transmitted transfusion virus (TTV) infection and its pathogenicity in children were evaluated. Serum TTV DNA from 118 children (mean age : 7.8±2 8 years) was detected by nested PCR. The product of PCR was cloned and sequenced. The positive rate for serum TTV DNA in 20 healthy children, 9 cases of acute hepatitis, 51 cases of chronic hepatitis, 24 cases of nephritis or nephrotic syndrome and 14 cases of hypoplastic anemia or acute leukemia was 20 %, 11 %, 29 %, 42 % and 21 % respectively, but there was no significant difference in TTV DNA frequency among them ( P >0.05). Of the 16 patients receiving immunosuppressive agent for a long time, 7 (44 %) were positive for TTV DNA, and of the 17 cases not receiving immunosuppressive agent, 5 (29 %) were positive with the difference being not significant ( P >0.05). Essential characteristics were pathogen carrier or asymtomatic infection in children with TTV infection. Long term employment of immunosuppressive agent did not increase the incidence in TTV infection. There was still high prevalence in TTV infection in healthy children not receiving blood product, suggesting the possibility of non hematogenous transmitted transfusion in TTV transmission.