The acronym TTV. Transfusion transmitted virus

Low prevalence of transfusion transmitted virus (TTV)-like DNA sequences in cystadenolymphoma and pleomorphic adenoma of the salivary glands

Titers of transfusion transmitted virus (TTV)-like DNA in saliva samples have been reported 100-1,000 times higher than those of the corresponding sera, suggesting viral transmission by saliva droplets. The present study was conducted to determine whether TTV-like DNA sequence elements play a role in the pathogenesis of cystadenolymphoma or pleomorphic adenoma and if the parotid or the submandibular gland is a major source of TTV persistence. Sixty-two archival salivary gland samples (16 cystadenolymphomas, 13 pleomorphic adenomas, and 33 controls) and 23 corresponding saliva samples were examined using a polymerase chain reaction (PCR) for TTV DNA. All PCR products that displayed DNA bands were sequenced. Leder's stain and immunohistochemistry (anti-CD8, anti-CD20, anti-CD45R0, anti-CD68, and anti-Ki67/MiB1) were applied to detect possible changes associated with findings of TTV-like DNA sequences. Tissue displayed TTV-like DNA sequences in 8.1% (5/62; saliva: 47.8%, 11/23). Tissue that contained TTV-like DNA sequences was histologically indistinguishable from samples lacking such DNA. TTV appears to be only a bystander in cystadenolymphoma, pleomorphic adenoma, and other salivary gland affections. Neither of the glands seems to be a major source of TTV persistence.

Effects of HAART on hepatitis C, hepatitis G, and TT virus in multiply coinfected HIV-positive patients with haemophilia

In multiply coinfected human immunodeficiency virus (HIV)-positive patients, we investigated the effects of high-activity antiretroviral therapy (HAART) using HIV protease inhibitors on three other viruses: hepatitis C virus (HCV), hepatitis G virus (HGV), and TT virus (TTV). Viral concentrations were measured serially by polymerase chain reaction methods in five patients with quadruple infection (HIV, HCV, HGV, and TTV) and in two patients with triple infection (HIV, HCV, and HGV) before and during HAART. In addition, CD4+ cell counts and serum alanine aminotransferase (ALT) levels were measured serially. Generally we observed no difference in serum HCV RNA, HGV RNA, or TTV DNA concentrations between samples obtained before and after initiation of HAART, whereas HIV RNA concentration decreased and CD4 counts increased in most patients. However, two patients had markedly decreased concentrations of HCV RNA and HGV RNA, respectively, more than 12 months after beginning HAART. Normalization of serum ALT levels was observed in a patient with decline of HCV RNA concentrations. No interactions were observed among these four viruses. HAART had no apparent direct effects on HCV, HGV, or TTV. Further studies will be required to elucidate whether the restoration of immune status through suppression of HIV replication by HAART may affect HCV or HGV RNA concentrations.

TT virus genotype changes frequently in multiply transfused patients with hemophilia but rarely in patients with chronic hepatitis C and in healthy subjects

BACKGROUND

TT virus (TTV), a novel DNA virus, was originally thought to be transmitted by transfusion. However, nonparenteral transmission is recently suspected to be a major mode of transmission. To investigate the possibility of reinfection with TTV in multiply transfused patients and to evaluate the significance of transfusion transmission of TTV in patients with hemophilia, serial changes in TTV genotype were investigated in three groups.

STUDY DESIGN AND METHODS

Serial changes in TTV genotype were investigated in 16 multiply transfused patients with hemophilia, 16 age-matched patients with chronic hepatitis C, and 16 age-matched healthy subjects.

RESULTS

Mixed infection with multiple TTV genotypes was common in all groups. However, changes in TTV genotype were frequent in patients with hemophilia (15/16; 93.8%) but rare in patients with chronic hepatitis C and in healthy subjects (each group: 1/16; 6.3%).

CONCLUSION

Changes in TTV genotype were frequently observed in multiply transfused patients with hemophilia but not in patients with chronic hepatitis or in healthy subjects without risk of transfusion transmission. This difference may suggest that exposure to TTV or even reinfection occurs frequently in patients with hemophilia, which could be evidence of transfusion transmission of TTV in this population.

Seroepidemiology of TT virus, GBC-C/HGV, and hepatitis viruses B, C, and E among women in a rural area of Tanzania

The seroprevalence and determinants of hepatitis B, C, and E virus infection, and of GBV-C/hepatitis G virus and TT virus infection were investigated among women from a rural area of northeastern Tanzania. High seroprevalence rates were found for TTV (74%), HBV (74%), and GBV-C/HGV (35%), whereas 7% of the women had evidence of HCV and HEV infection. The majority of TTV DNA sequences in the study population belonged to the genotypes 1 or 2. One sequence seems to represent a new subtype of genotype 4. The GBV-C/HGV sequences either belonged to the genomic Group 1b or to the recently described Group 4. In multivariate analysis, the detection of TTV DNA was associated significantly with a larger number of children in the household and with older age. A history of injections of contraceptive hormones was an independent risk factor for HCV infection. The findings on TTV are consistent with fecal-oral transmission, and recurrent infections may occur in adults.

Biliary excretion of TT virus (TTV)

A novel DNA virus (TT virus; TTV) was isolated from a patient with post-transfusion hepatitis of unknown etiology. If TTV replicates in the liver, TTV may appear in the bile. In the present study, to clarify whether fecal-oral infection occur via biliary excretion, the presence of TTV DNA was assessed in paired serum and bile samples collected from 28 patients with obstructive jaundice without parenchymal liver disease. TTV DNA was detected by polymerase chain reaction (PCR) using semi-nested primers, and quantified by Real Time Detection PCR (RTD-PCR). The nucleotide sequence of isolates TTV DNAs was also determined and the sequences were compared between serum and bile samples. Among 28 patients, 7 were positive for TTV DNA in both samples, and 3 and 2 were positive in serum and bile respectively. Of 7 patients positive for TTV DNA in both samples, the TTV DNA titer was higher in serum of 4 patients and in bile of 1 patient. Among 7 patients positive for TTV DNA in serum and bile, 6 had the same sequence in both samples. Multiple distinct types of TTV DNA clones were isolated from serum in 2 patients and from bile in 4 patients. In conclusion, TTV DNA is detected frequently in bile from patients with obstructive jaundice, suggesting a fecal-oral route of infection and high prevalence of asymptomatic TTV carriers. TTV DNA was detected only in serum from some patients, suggesting that replication of TTV may occur in other organs as well as in the liver.

TT virus infection in human immunodeficiency virus type 1 infected mothers and their infants

Serum TT virus (TTV) DNA was determined in 83 human immunodeficiency virus type 1 (HIV 1) infected mothers [46 intravenous drug user and 37 non-intravenous drug user women] and their infants. Twenty-nine (34.9%) mothers were TTV infected. Infection was more frequent among intravenous drug user than non-intravenous drug user mothers [21/46 (45.6%) vs. 8/37 (21.6%); relative risk (RR): 2.1; 95% confidence limits (95% CL): 1.1-4.2; P = 0.023] and among intravenous drug users who carried on injecting than in those who had given it up [10/14 (71.4%) vs. 11/32 (34.3%); RR: 2.1 (95%CL: 1.2-3.7); P = 0. 021]. Infection was not related to age, CD4-positive T-lymphocyte counts, HIV 1 load, hepatitis B (HBV), G/GB-C (GBV-C/HGV), C (HCV) virus exposure. Eight (27.5%) infants born to TTV infected (but none of those born to TTV uninfected) mothers were TTV infected at a median age of 1.5 (range: 0.6-2.8) months. Infants born by vaginal/emergency caesarean delivery were more frequently infected than those born by elective caesarean delivery [7/16 (43.7%) vs. 1/13 (7.6%); RR: 2.1; 95%CL: 1.2-3.5; P = 0.033]. Infection in infants was not related to maternal CD4-positive T-lymphocyte counts, HIV 1 load, and HIV 1, HBV, GBV-C/HGV, or HCV transmission. No infant became TTV infected thereafter. No TTV infected child [follow-up: 31 (median; range: 6-60) months] showed signs of liver disease; five infants cleared TTV DNA after 22 (median; range: 6-60) months. TTV infection in HIV 1 infected women is prevalently related to intravenous drug user. The findings suggest that infants may acquire TTV at birth. Infection may persist without evident liver disease.

TT virus as a human pathogen: significance and problems

In 1997 TTV was detected using representational difference analysis (RDA) in serum of a patient with posttransfusion hepatitis unrelated to known hepatitis viruses. The genome of TTV is a circular single-stranded DNA molecule of 3852 nt with negative polarity. TTV possibly can be grouped either into the existing family Circoviridae or into a recently established virus family "Circinoviridae". Analysis of the complete DNA nucleotide sequence of TTV identified three partially overlapping open reading frames (ORFs). Neither DNA nucleotide nor corresponding amino acid sequences of TTV do show significant homologies to known sequences. TTV DNA nucleotide sequences amplified by PCR from sera of different patients show considerable sequence variations. Although the natural route of transmission of TTV is still unknown, there is clear evidence for a transmission of TTV through blood and blood products. TTV DNA can be detected in the feces of infected individuals suggesting that it may be possible to attract TTV infection from environmental sources. Since the discovery of TTV, numerous studies have investigated the prevalence of TTV infections in different human population groups all over the world. All these studies are based on PCR detection systems, but the technical aspects of the PCR systems vary significantly between the different investigators. The results of the epidemiological studies do not show a clear picture. The discovery of TTV as a viral agent and particularly the identification of a high percentage of infected carriers in the healthy human population raises the following questions: Firstly, what is the origin and molecular relatedness of TT virus. Secondly, what is the significance of TTV as a human pathogen. And thirdly, what are the exact molecular mechanisms of viral replication. To answer these questions it will be necessary to determine the primary structure and the coding capacity of several TTV patient isolates.

Prevalence and risk factor analysis of TTV infection in prostitutes

TTV, a DNA virus, has been isolated from patients with non-A to non-E post-transfusion hepatitis. In the past it was assumed that TTV was transmitted parenterally. It is unclear whether sexual contact leads to transmission of this virus. In this study, two sets of TTV-specific polymerase chain reaction primers were used to detect serum TTV DNA in 140 prostitutes and 136 controls. The prevalence of TTV DNA in prostitutes was significantly higher than in the control group (46/140 [32.9%] vs. 29/136 [21.3%]; P = 0.043). There was no significant difference in the prevalence of positive antibody to hepatitis A virus (anti-HAV) in either group (87.8% for prostitutes, 85.3% for controls). No particular risk factor was significantly associated with positive TTV DNA in prostitutes. In summary, TTV is highly prevalent in prostitutes. Transmission of TTV via sexual contact is not as efficient as transmission of hepatitis C and D viruses and GB virus-C hepatitis G virus. The high prevalence of TTV in controls indicates that there are diverse routes of transmission of this virus.

TT virus infection in patients with chronic hepatitis B or C: influence on clinical, histological and virological features

Concomitant infection with TT virus and hepatitis B virus (HBV) or hepatitis C virus (HCV) is common. However, the effect of TTV infection on chronic hepatitis B or C is unknown. The prevalence of TTV infection, the effect of TTV infection on the clinical, histological and virological features of patients with chronic hepatitis B or C, and the influence of TTV infection on the HCV response to interferon alfa therapy were studied. A total of 100 asymptomatic hepatitis B surface antigen carriers, 220 patients with HBV-related chronic liver diseases, and 110 patients with chronic hepatitis C treated with interferon alfa (3 million units subcutaneously three times a week for 24 weeks) were enrolled. Serum HCV RNA and serum TTV DNA were detected by the polymerase chain reaction (PCR). Serum HBV DNA and serum HCV RNA level were quantified by branched DNA assays. Infection with TTV was detected in 21.5% of HBV carriers and 37% of HCV carriers. TTV infection had little effect on the clinicopathological course of chronic HBV infection. In chronic hepatitis C, clinical features, histological severity, serum HCV RNA levels, and the response to interferon alfa therapy did not differ between those with and without TTV infection. The loss of serum TTV DNA did not correlate with the biochemical response as did in the loss of serum HCV RNA. In conclusion, TTV infection is found frequently in patients with chronic hepatitis B or C in Taiwan; however, coinfection with TTV does not affect the clinicopathological course of chronic hepatitis B or C and the response to interferon alfa therapy.

[The virus isolated from patient TT (TTV): still an orphan 2 years after its discovery]

TTV is the acronym for a virus isolated two years ago from a patient whose initials were T.T. It is a naked virus probably belonging to the Circoviridae family. TTV has a particle size of 30-50 nm and possesses a single-strand circular DNA. Epidemiologic data are derived from studies looking for the viral DNA by the polymerase chain reaction (PCR). Important differences between early and recent studies appear to be due to the use of PCR assays based on primers located in different regions of the genome. Based on the most recent studies, the prevalence of TTV infections seems very high in the general population. TTV is present in the feces and would be transmitted through the fecal-oral route. It appears to be a ubiquitous virus, also present in various animal species, from chickens to chimpanzees. No association to any pathology has been identified so far, and TTV infection does not have a significant effect on liver disease.