Torque Teno Virus Viral Load as a Marker of Immune Function in Allogeneic Haematopoietic Stem Cell Transplantation Recipients.

Torque teno virus (TTV) has been proposed as a surrogate biomarker of T-cell function in allogeneic-haematopoietic-stem-cell transplantation (allo-HSCT). Conflicting data exists regarding the value of TTV to assess the degree of immunosuppression. The aim of the present study was to investigate the correlation between TTV viral load and immune function. Using samples from a prospective cohort composed of healthy-volunteers (HV) and allo-HSCT recipients at 6 months post-transplantation, we assessed the correlation between TTV viraemia and immune cell counts or T-cell proliferation capacity post-phytohaemagglutinin stimulation. TTV viraemia was detected in 68% of HV (n = 80) and 100% of allo-HSCT recipients (n = 41; p < 0.001); it was significantly higher in allo-HSCT recipients (3.9 vs. 2.1 Log copies/mL, p < 0.001). There was no correlation between T-cell function and CD3+T-cell count (rho: 0.002) suggesting that T-cell count can normalise without full functional recovery. Furthermore, no significant correlation was observed between TTV viraemia and absolute total/subset lymphocyte counts (rho: <0.13). The highest correlation was observed between TTV viral load and T-cell proliferation capacity (rho: -0.39). We therefore report an inverse correlation between T-cell function and TTV viraemia that is independent of T-cell count. Monitoring of TTV viraemia could be a fast suitable option to objectively assess the competence of immune function in at-risk populations.

Torque Teno Virus as a Potential Biomarker for Complications and Survival After Allogeneic Hematopoietic Stem Cell Transplantation.

Impaired immune reconstitution after allogeneic hematopoietic stem cell transplantation (HSCT) contributes to increased risk of cancer relapse and infection resulting in significant morbidity and mortality. Unfortunately, effective strategies to functionally assess the quality of immune reconstitution are still missing. Quantification of in vivo replication of the ubiquitous, non-pathogenic virus Torque Teno Virus (TTV) has been reported in small series as a test to functionally evaluate the quality of post-transplant immune reconstitution. In the present study, we analyzed by quantitative PCR TTV titers in plasma samples from a large cohort of 168 allogeneic HSCT recipients. Our analysis confirms that TTV titers peaked at 100 days post-transplant, followed by progressive normalization thereafter. Negative correlation of TTV titers with T cell absolute numbers during the first year post-transplant points to the restoration of an active anti-TTV immunity. Univariable and multivariable linear regression analysis demonstrated that donor CMV positive serostatus, donor type and immune suppression resulting from GVHD treatment affected the restoration of anti-TTV immunity. Importantly, higher TTV titers at 100 days after transplantation were associated with worse overall survival and higher risk of acute GVHD and infections. Our results provide new insights into the factors affecting the dynamics of TTV replication and indicate that TTV is a potentially useful biomarker to assess immune reconstitution and to predict complications and outcomes of allogeneic HSCT.

Torque teno virus: an improved indicator for viral pathogens in drinking waters.

BACKGROUND: Currently applied indicator organism systems, such as coliforms, are not fully protective of public health from enteric viruses in water sources. Waterborne disease outbreaks have occurred in systems that tested negative for coliforms, and positive coliform results do not necessarily correlate with viral risk. It is widely recognized that bacterial indicators do not co-occur exclusively with infectious viruses, nor do they respond in the same manner to environmental or engineered stressors. Thus, a more appropriate indicator of health risks from infectious enteric viruses is needed. PRESENTATION OF THE HYPOTHESIS: Torque teno virus is a small, non-enveloped DNA virus that likely exhibits similar transport characteristics to pathogenic enteric viruses. Torque teno virus is unique among enteric viral pathogens in that it appears to be ubiquitous in humans, elicits seemingly innocuous infections, and does not exhibit seasonal fluctuations or epidemic spikes. Torque teno virus is transmitted primarily via the fecal-oral route and can be assayed using rapid molecular techniques. We hypothesize that Torque teno virus is a more appropriate indicator of viral pathogens in drinking waters than currently used indicator systems based solely on bacteria. TESTING THE HYPOTHESIS: To test the hypothesis, a multi-phased research approach is needed. First, a reliable Torque teno virus assay must be developed. A rapid, sensitive, and specific PCR method using established nested primer sets would be most appropriate for routine monitoring of waters. Because PCR detects both infectious and inactivated virus, an in vitro method to assess infectivity also is needed. The density and occurrence of Torque teno virus in feces, wastewater, and source waters must be established to define spatial and temporal stability of this potential indicator. Finally, Torque teno virus behavior through drinking water treatment plants must be determined with co-assessment of traditional indicators and enteric viral pathogens to assess whether correlations exist. IMPLICATIONS OF THE HYPOTHESIS: If substantiated, Torque teno virus could provide a completely new, reliable, and efficient indicator system for viral pathogen risk. This indicator would have broad application to drinking water utilities, watershed managers, and protection agencies and would provide a better means to assess viral risk and protect public health.

High torquetenovirus loads are correlated with bronchiectasis and peripheral airflow limitation in children.

BACKGROUND: The aim of the study was to evaluate the prevalence of torquetenovirus (TTV) infection in a group of children with recurrent lower respiratory tract infections and radiologic evidence of bronchiectasis. Correlations between TTV loads and severity of bronchiectasis and between TTV loads and lung function were evaluated. METHODS: In 38 subjects, high-resolution computed tomography (HRCT) and plasma tests for TTV detection and quantification were done. In 21/38 subjects, spirometry was also performed. RESULTS: TTV was found in 31/38 (81.6%) patients. The correlation between TTV loads and severity of bronchiectasis was statistically significant (r = 0.548; P = 0.01). TTV loads showed inverse correlation with FEF25-75% (r = -0.541; P = 0.011), and FEF25-75%/FVC (r = -0.512; P = 0.018). Inverse correlation was found also between severity of bronchiectasis and functional lung parameters: FEF25-75% (r = -0.635; P = 0.002), FEV1/FVC (r = -0.541; P = 0.011), and FEF25-75%/FVC (r = -0.645; P = 0.002). CONCLUSIONS: This study demonstrated the high prevalence of TTV infection in children with bronchiectasis. Moreover, we have shown a significant correlation between TTV loads and airflow limitation within the peripheral airways, as well as between severity of bronchiectasis and decrease of lung function.

Human circoviruses.

TT virus (TTV) and TTV-like mini virus (TLMV) represent the first described human circoviruses. They do not show significant sequence homology with any other animal circovirus identified to date. They are both detected with high prevalences in various body fluids. The spread mode may include the parenteral way, the transmission by saliva droplets and the fecal-oral route. Genetic variability within a viral group is high and the co-infection by distinct viral strains is common in a given individual. The description of several messenger RNAs obtained after multiple splicing revealed a specific transcription profile. Despite apparent asymptomatic infections, the possible association of variants of TTV and TLMV with a given pathology cannot be formally ruled out.

Transfusion-associated TT virus co-infection in patients with hepatitis C virus is associated with type II mixed cryoglobulinemia but not with B-cell non-Hodgkin lymphoma.

OBJECTIVE: To assess the prevalence of TT virus (TMV) infection in a series of patients with chronic hepatitis C virus (HCV) infection, with or without benign (mixed cryoglobulinemia) or malignant (B-cell non-Hodgkin lymphoma (B-NHL)) lymphoproliferative disease. METHODS: Sixty-six HCV patients were studied, including patients with mixed cryoglobulinemia (n=30), B-NHL (n=15), and no mixed cryoglobulinemia or B-NHL (n=21). All HCV patients had increased transaminase levels and were HCV RNA positive. Patients were considered to have mixed cryoglobulinemia if two successive determinations of their serum cryoglobulin level were above 0.05 g/L. Mixed cryoglobulinemia-negative patients never had mixed cryoglobulins in their serum on multiple determinations. Subjects without HCV infection included 79 patients with histologically proven B-NHL, and 50 healthy blood donors. Serum samples were analyzed for TTV DNA by nested polymerase chain reaction, with two couples of primers in different regions of the genome, in two independent laboratories. RESULTS: In the group of HCV-positive patients, TTV DNA was found in one of 15 (6.7%) patients with B-NHL, and in nine of 51 (17.6%, P = 0.43) of those without B-NHL. Among HCV-positive patients without B-NHL, TTV DNA was more frequently found in those with type II mixed cryoglobulinemia vasculitis than in those without it (six of 16 (37.5%) versus two of 21 (9.5%), P = 0.05). In subjects without HCV infection, TTV DNA was present in 10 of 79 (12.7%) patients with B-NHL and in seven of 50 (14.0%, P = 0.82) blood donors. CONCLUSION: In patients chronically infected with HCV, TTV co-infection: (1) is not associated with the presence of B-NHL; and (2) is more frequently found in patients presenting a type II mixed cryoglobulinemia vasculitis.

TT virus has a ubiquitous diffusion in human body tissues: analyses of paired serum and tissue samples.

The tissue tropism and possible correlation with liver disease of the TT virus (TTV) as well as its prevalence and genotype distribution remain undefined. TTV-DNA was investigated in paired sera and tissue samples from 144 patients, and sera and cerebrospinal fluids (CSF) from additional six subjects. Of the 144 tissue samples, 128 were liver biopsy specimens from subjects with hepatic disease while 16 were surgically obtained nonliver specimens from patients with extrahepatic disease. TTV cloning, sequencing and genotype analyses were performed on isolates from sera, tissue specimens and peripheral blood mononuclear cells of two patients with hepatic and four patients with extrahepatic pathologies, as well as from sera and CSFs of two subjects. TTV was found in 100% of the examined tissues and in 60.1 and 50% of sera from patients with hepatic and extrahepatic pathologies, respectively. Moreover, TTV was detected in four of the six CSFs analysed but only in two correspondent sera. Genotyping revealed the coexistence of multiple TTV genotypes and genetic variants in each infected individual, and the analysis of TTV mRNA showed the presence of transcripts in all the six different tissues studied. These results indicate that the entire adult population in our area is more likely infected by TTV, although several subjects are not viraemic and that TTV infects many different human tissues and is able to invade the central nervous system.

Molecular epidemiology of TT virus in Italy and phylogenesis of viral isolates from subjects at different risk for parenteral exposure.

The prevalence and genotype distribution of human TT virus (TTV) in Italy were analysed in 593 subjects at different risk of parenteral infection who included blood donors, patients with chronic type C hepatitis (HCV), thalassemic patients, patients on haemodialysis, human immunodeficiency virus type 1 (HIV-1)-negative intravenous drug users (IVDUs), and HIV-1-infected subjects (IVDUs, heterosexual contacts and homosexual males). Plasma TTV-DNA was detected using nested PCR with primers deduced from the N22 region of the open reading frame 1 (ORF-1) and from the untranslated region (UTR) of the viral genome. Phylogenetic analysis of the sequences obtained from ORF-1 was also undertaken. A high prevalence of plasma TTV-DNA was observed using the UTR primers, with rates varying from 83-100% in the study groups. Using the N22 primers, HIV-1 positive IVDUs and homosexual males, haemodialysed patients and thalassemic patients had a significantly higher TTV prevalence (range: 23.0-86.1%) than blood donors, who displayed a high frequency of positivity (10.6%). Sequence analysis of 127 N22-positive isolates revealed that 42.5% were of type 1, 53.5% of type 2, 2.4% of type 3, and that two isolates (1.6%) were closely related to genotypes 1-2 but distinct from the other major genotypes. TTV-2 was significantly more prevalent in patients at high risk for parenteral infection and in HIV-1 positive homosexuals. In sequential samples from 15 TTV-infected subjects, N22 sequences were detectable persistently in 12 (80.0%) and UTR sequences persisted in all 15 patients over a mean period of 29.6 months. This data indicates that TTV is widespread in Italy in parenterally exposed subjects, and that the infection frequently persists.

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.