Torque Teno Virus Load Is Associated With Subclinical Alloreactivity in Kidney Transplant Recipients: A Prospective Observational Trial.

BACKGROUND: Nonpathogenic torque teno viruses (TTVs) are highly prevalent in transplant recipients and associated with immunosuppression. Studies in kidney transplant patients have proposed assessment of TTV load for risk stratification of clinically overt graft rejection. The value of TTV quantification in the context of subclinical rejection has not been evaluated. METHODS: In this prospective trial, 307 consecutive kidney transplant recipients were subjected to per-protocol monitoring of plasma TTV. TTV was analyzed in the context of protocol biopsies (n = 82), scheduled 1 year posttransplantation. RESULTS: TTV load at the time of biopsy was lower in recipients with rejection (n = 19; according to Banff, including borderline changes suspicious for acute T cell-mediated rejection) than those without rejection (n = 63) whereby each log increase in TTV copies/mL decreased the risk for rejection by 9% (risk ratio 0.91, 95% confidence interval, 0.85-0.97; P = 0.004). Development of chronic lesions (cg, cv, ci, ct, ah, ptcml) was associated with the number of days with a TTV load <1 × 106 copies/mL between months 3 and 12 posttransplant (ß 0.07, 95% confidence interval, 0.01-0.14; P = 0.02). CONCLUSIONS: This trial demonstrates an association between TTV and subclinical graft rejection in kidney transplant recipients. A TTV load <1 × 106 copies/mL suggests suboptimal immunosuppression.

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 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.

Torque teno virus viral load is related to age, CMV infection and HLA type but not to Alzheimer's disease.

Torque teno virus (TTV) is an unenveloped, circular, single stranded DNA virus with a genome size of approximately 3.8 kb. Previous studies have demonstrated varying grades of association between TTV DNA levels and immune deficiencies related to age, chronic infections and cancer. Alzheimer's disease (AD) has been related to persistent viral infections such as HSV-1 and CMV, but it is not known whether TTV viral load could serve as a functional biomarker of cellular immunity in this setting. Therefore, the objective of this study was to investigate whether TTV infection and viral load is related to AD status, CMV immunity, systemic inflammation or HLA types connected to anti-viral immunity. A total of 50 AD subjects and 51 non-demented controls were included in the study. AD subjects were diagnosed according to NINCDS-ADRDA and DSM-IV criteria and neuroradiologic findings were consistent with the diagnosis. TTV viral load was analyzed in plasma samples using a quantitative real-time PCR. Using a cut-off for TTV status at 200 copies/ml, 88% (89/101) of the study subjects were classified as TTV positive. TTV viral load significantly increased with age (beta 0.049 per year, p<0.001) but significantly decreased in relation to CMV IgG levels (beta -0.022 per 1000 units, p = 0.005) and HLA-B27 positivity (beta -0.53, p = 0.023). In conclusion, TTV immune control is not significantly affected by AD status, but appears related to age, CMV humoral immune response and HLA type.

Prevalence and Loads of Torquetenovirus in the European MARK-AGE Study Population.

Torquetenovirus (TTV) viremia has been associated with increased mortality risk in the elderly population. This work aims to investigate TTV viremia as a potential biomarker of immunosenescence. We compared levels of circulating TTV in 1813 participants of the MARK-AGE project, including human models of delayed (offspring of centenarians [GO]) and premature (Down syndrome [DS]) immunosenescence. The TTV load was positively associated with age, cytomegalovirus (CMV) antibody levels, and the Cu/Zn ratio and negatively associated with platelets, total cholesterol, and total IgM. TTV viremia was highest in DS and lowest in GO, with intermediate levels in the SGO (spouses of GO) and RASIG (Randomly Recruited Age-Stratified Individuals From The General Population) populations. In the RASIG population, TTV DNA loads showed a slight negative association with CD3+T-cells and CD4+T-cells. Finally, males with ≥4log TTV copies/mL had a higher risk of having a CD4/CD8 ratio<1 than those with lower viremia (odds ratio [OR] = 2.85, 95% confidence interval [CI]: 1.06-7.62), as well as reduced CD3+ and CD4+T-cells compared to males with lower replication rates (<4log), even after adjusting for CMV infection. In summary, differences in immune system preservation are reflected in the models of delayed and premature immunosenescence, displaying the best and worst control over TTV replication, respectively. In the general population, TTV loads were negatively associated with CD4+ cell counts, with an increased predisposition for an inverted CD4/CD8 ratio for individuals with TTV loads ≥4log copies/mL, thus promoting an immune risk phenotype.

Torque Teno Virus Is Associated With the State of Immune Suppression Early After Liver Transplantation.

The development of noninvasive biomarkers that reflect the state of immunosuppression (IS) remains an unmet need in liver transplantation (LT). Torque Teno virus (TTV) is a highly prevalent, nonpathogenic DNA virus whose plasma levels may be associated with the immune status of the host. The aim of this study was to assess the role of TTV as a biomarker of IS in LT recipients. TTV DNA in plasma was quantified by real-time polymerase chain reaction at different time points during the first year after transplant in a prospectively followed cohort of 63 de novo LT recipients, and any correlation between TTV DNA and biopsy-proven acute cellular rejection (ACR) and opportunistic infections was then evaluated. In addition, TTV DNA was studied in 10 longterm LT recipients in monotherapy with tacrolimus, 10 tolerant recipients, and 10 healthy controls. TTV was detected in the plasma of all patients. Among the 63 LT recipients, 20 episodes of ACR were diagnosed, and there were 28 opportunistic infections, 26 of them being cytomegalovirus (CMV) infections. TTV viremia was significantly lower during ACR (4.41 versus 5.95 log10 copies/mL; P = 0.002) and significantly higher during CMV infections (5.79 versus 6.59 log10 copies/mL; P = 0.009). The area under the receiver operating characteristic curve of TTV viral load for the diagnosis of moderate ACR was 0.869, with a sensitivity and negative predictive value of 100%, respectively, for a cutoff point of 4.75 log10 copies/mL. There were no statistically significant differences in TTV DNA in either longterm or tolerant patients and healthy controls. In conclusion, plasma TTV DNA levels are associated with immune-related events after LT and could constitute a potential biomarker of the state of IS during the first months after transplant.

Torque Teno Virus Load-Inverse Association With Antibody-Mediated Rejection After Kidney Transplantation.

BACKGROUND: Antibody-mediated rejection (AMR) represents one of the cardinal causes of late allograft loss after kidney transplantation, and there is great need for noninvasive tools improving early diagnosis of this rejection type. One promising strategy might be the quantification of peripheral blood DNA levels of the highly prevalent and apathogenic Torque Teno virus (TTV), which might mirror the overall level of immunosuppression and thus help determine the risk of alloimmune response. METHODS: To assess the association between TTV load in the peripheral blood and AMR, 715 kidney transplant recipients (median, 6.3 years posttransplantation) were subjected to a systematical cross-sectional AMR screening and, in parallel, TTV quantification. RESULTS: Eighty-six of these recipients had donor-specific antibodies and underwent protocol biopsy, AMR-positive patients (n = 46) showed only 25% of the TTV levels measured in patients without AMR (P = 0.003). In a generalized linear model, higher TTV levels were associated with a decreased risk for AMR after adjustment for potential confounders (risk ratio 0.94 per TTV log level; 95% confidence interval 0.90-0.99; P = 0.02). CONCLUSIONS: Future studies will have to clarify whether longitudinal assessment of TTV load might predict AMR risk and help guide the type and intensity of immunosuppression to prevent antibody-mediated graft injury.

Development of an Immunoassay for Detection of Torque Teno Virus (TTV) Antibodies Using the N22 Expression Product from TTV Genotype 2.

AIMS: This study describes an immunoassay to detect anti-torque teno virus (TTV) antibodies using a peptide obtained from expression of the N22 region of TTV genotype 2. METHODS: The N22 region (∼500 bp) of TTV genotype 2 was cloned in a pET-28a(+) vector and expressed in ZYM-5052 autoinduction medium. Following metal affinity chromatography, a purified polypeptide was used as an antigen for the development of an immunoassay to detect anti-TTV antibodies in human sera. RESULTS: Recombinant protein (∼25-kDa) was obtained after 24 h of incubation at 25°C in ZYM-5052 autoinduction medium. A blot assay developed using this polypeptide as an antigen and TTV-positive sera as the primary antibody produced a distinct spot on the nitrocellulose membrane. Serum samples from 36 of 42 patients with renal disease and 29 of 48 patients with liver diseases produced a positive signal using this immunoassay. Simultaneously, 18 of 48 healthy controls were also detected to be positive for anti-TTV antibodies. These results were found to be comparable with TTV detection using PCR, and the assay showed a high sensitivity and specificity (i.e., 97.44 and 91.67%, respectively). Moreover, this assay could detect TTV infection irrespectively of the genotype, including cases of mixed infection. CONCLUSION: The present immunoassay using the N22 expression product may be used as an alternative to PCR to detect TTV infection in large populations.

Lack of strong anti-viral immune gene stimulation in Torque Teno Sus Virus1 infected macrophage cells.

While recent findings suggest that swine TTVs (TTSuVs) can act as primary or co-infecting pathogens, very little is known about viral immunity. To determine whether TTSuVs downregulate key host immune responses to facilitate their own survival, a swine macrophage cell line, 3D4/31, was used to over-express recombinant TTSuV1 viral particles or the ORF3 protein. Immune gene expression profiles were assessed by a quantitative PCR panel consisting of 22 immune genes, in cell samples collected at 6, 12, 24 and 48h post-transfection. Despite the upregulation of IFN-ß and TLR9, interferon stimulated innate genes and pro-inflammatory genes were not upregulated in virally infected cells. The adaptive immune genes, IL-4 and IL-13, were significantly downregulated at 6h post-transfection. The ORF3 protein did not appear do not have a major immuno-suppressive effect, nor did it stimulate anti-viral immunity. Data from this study warrants further investigation into the mechanisms of TTV related immuno-pathogenesis.

Immune gene expression in swine macrophages expressing the Torque Teno Sus Virus1 (TTSuV1) ORF-1 and 2 proteins.

Torque Teno viruses (TTVs) are small DNA viruses which are ubiquitous in nature. Recent reports indicate that swine torque teno viruses (TTSuVs) can act as primary pathogens or play a role in exacerbating co-infections. However, very little is known about the TTSuV host-viral interaction or how they so successfully establish chronic infections in the host. To determine whether the major viral proteins can modulate host immunity, recombinant TTSuV1 ORF1 and 2 proteins were expressed in a swine macrophage cell line (3D4/31). The differential expression of a panel of innate, adaptive, regulatory and inflammatory immune genes was studied by quantitative PCR; using cDNA samples collected at 6, 12, 24 and 48h post-transfection. The ORF1 protein induced an early anti-viral response. However, at 6h post-transfection it also upregulated IL-10, PD-1 and SOCS-1, the suppressors of T cell mediated immunity. An ensuing diminishment of the early protective response was noted. The TTSuV1 ORF2 protein suppressed IFN-ß and IL-13 responses but did not significantly influence anti-viral immunity otherwise. These findings indicate that the TTSuV1 ORF1 protein plays a significant but dual role in viral immunity.

Development of an indirect ELISA assay for the detection of IgG antibodies against the ORF1 of Torque teno sus viruses 1 and 2 in conventional pigs.

Torque teno sus viruses (TTSuV, family Anelloviridae) cause long lasting and persistent infection in pigs under subclinical scenarios, and are potentially linked to several economically important swine diseases. Currently, little is known about swine immune response against TTSuV infections. In this study, an ELISA assay was developed based on the ORF1-A recombinant protein of two known TTSuVs, namely TTSuV1 (genus Iotatorquevirus) and TTSuV2 (genus Kappatorquevirus). The assay was used to study the development of the humoral immune response against TTSuV1 and TTSuV2 in longitudinally sampled clinically healthy pigs and their dams. Anti ORF1-A IgG was found in serum of pigs and sows for both TTSuVs. From 15 sows, 15 (100%) and 13 (83%) had anti ORF1-A IgG against TTSuV1 and TTSuV2, respectively. Pig sero-prevalences at the first sampling (4 weeks of age) were 65% (24/37) and 5% (2/37) for TTSuV1 and TTSuV2, respectively. For TTSuV1, the highest anti ORF1-A IgG prevalence was observed at weeks 21 and 25, with 68% (25/37) sero-positive pigs. Quantitative PCR (qPCR) results at week 21 revealed that 26 out of 32 (81%) pigs were positive for TTSuV1. In the case of TTSuV2, the highest anti ORF1-A IgG prevalence was observed at week 21, with 84% (31/37) pigs being sero-positive. At the same week, 92% (34/37) of pigs were qPCR positive. In summary, anti ORF1-A IgGs were detected in both sows and piglets at different ages, indicating that these animals could mount a humoral immune response against both TTSuVs. However, the high percentage of viremic pigs in presence of anti ORF1-A IgG suggests that these antibodies are not able to remove TTSuVs from circulation.

The APOBEC3B deletion polymorphism is associated with prevalence of hepatitis B virus, hepatitis C virus, Torque Teno virus, and Toxoplasma gondii co-infection among HIV-infected individuals.

BACKGROUND: Data regarding the influence of the APOBEC3B deletion on infectious diseases remain limited and shown discrepancies. OBJECTIVES: To characterize the APOBEC3B deletion polymorphism status and its association with prevalence of co-infection with blood-borne pathogens in Indonesian HIV-infected individuals. MATERIALS AND METHODS: A total of 597 HIV-positive blood samples were tested for the hepatitis B virus (HBV), hepatitis C virus (HCV), Torque Teno virus (TTV), GB virus-C (GBV-C), and Toxoplasma gondii. Nucleic acid was extracted from plasma samples and used for the molecular detection of HIV RNA, HBV DNA, HCV RNA, TTV DNA, and GBV-C RNA, whereas HBsAg, anti-HCV, IgM and IgG anti-T. gondii were detected through serological testing. The APOBEC3B deletion polymorphism was genotyped by polymerase chain reaction (PCR). RESULTS: The deletion genotype was associated with HCV viremia (p<0.001) as well as elevated IgG anti-T. gondii (adjusted OR [aOR]=3.4). The deletion genotype was also associated with decreased levels of HBsAg (aOR=0.03), and anti-HCV (aOR=0.1). D/D was frequently found in HIV-infected individuals with CD4+T cells<14% (aOR=5.8). The intact genotype was associated with a reduced likelihood of a CD4+T cell count<200 cells/µL (aOR=0.2) but a higher prevalence of TTV co-infection (aOR=8.6). CONCLUSIONS: The APOBEC3B deletion polymorphism was found to be associated with HBV, HCV, TTV, and T. gondii co-infection in Indonesian HIV-infected individuals.

Vaccination of pigs reduces Torque teno sus virus viremia during natural infection.

Anelloviruses are a group of single-stranded circular DNA viruses infecting several vertebrate species. Four species have been found to infect swine, namely Torque teno sus virus (TTSuV) 1a and 1b (TTSuV1a, TTSuV1b; genus Iotatorquevirus), TTSuVk2a and TTSuVk2b (genus Kappatorquevirus). TTSuV infection in pigs is distributed worldwide, and is characterized by a persistent viremia. However, the real impact, if any, on the pig health is still under debate. In the present study, the impact of pig immunization on TTSuVk2a loads was evaluated. For this, three-week old conventional pigs were primed with DNA vaccines encoding the ORF2 gene and the ORF1-A, ORF1-B, and ORF1-C splicing variants and boosted with purified ORF1-A and ORF2 Escherichia coli proteins, while another group served as unvaccinated control animals, and the viral load dynamics during natural infection was observed. Immunization led to delayed onset of TTSuVk2a infection and at the end of the study when the animals were 15 weeks of age, a number of animals in the immunized group had cleared the TTSuVk2a viremia, which was not the case in the control group. This study demonstrated for the first time that TTSuV viremia can be controlled by a combined DNA and protein immunization, especially apparent two weeks after the first DNA immunization before seroconversion was observed. Further studies are needed to understand the mechanisms behind this and its impact for pig producers.

[Serological tests of the truncated TTSuV2 ORF1 recombinant proteins with the porcine sera].

OBJECTIVE: We studied the serological response between the special regions on the Torque teno sus virus 2 (TTSuV2) ORF1 coded protein and the porcine sera from conventional pigs. METHODS: Based on a Chinese TTSuV2 strain from Guangdong province, two overlapped virus proteins were expressed from Escherichia coli. Then, purified recombinant TTSuV2 ORF1a and TTSuV2 ORF1ab proteins were used as the antigens in the Western Blotting and ELISA assay. RESULTS: The recombinant TTSuV2 ORF1a and TTSuV2 ORF1ab proteins were identified with the special tag monoclonal antibody. The results of the ELISA tests shown that there were significant relationships between two groups of dates from the recombinant TTSuV2 ORF1a and TTSuV2 ORF1ab proteins antigenic assay. The results of the following Western Blotting assay indicated that the TTSuV2-specific IgG antibodies were contained in pig sera. CONCLUSION: The truncated TTSuV2 ORF1a protein (positions 168 to 346 corresponding to TTSuV2 GDIMA1) contains important B cell epitopes which can stimulate immune system antibody secretion. The truncated TTSuV2 ORF1a protein could be effective in TTSuV2 immunodiagnosis.

Short-term kinetics of torque teno virus viraemia after induction immunosuppression confirm T lymphocytes as the main replication-competent cells.

Torque teno virus (TTV) is increasingly considered a universal marker of global immune function. The virus is supposed to replicate in lymphocytes, but poor information is available about fluctuations of viraemia after administration of anti-lymphocyte agents. We studied TTV kinetics in a cohort of 70 kidney±pancreas recipients receiving one of two different anti-T-cell induction immunosuppressants. During the first 30 days after anti-T-cell antibody administration, we report kinetics of TTV viraemia compatible with replication in T lymphocytes, and highly dependent on the potency of the anti-T-cell drug administered.

Cloning and expression of N22 region of Torque Teno virus (TTV) genome and use of peptide in developing immunoassay for TTV antibodies.

BACKGROUND: Torque Teno Virus (TTV) is a DNA virus with high rate of prevalence globally. Since its discovery in 1997, several studies have questioned the role of this virus in causing disease. However, it still remains an enigma. Although methods are available for detection of TTV infection, there is still a need for simple, rapid and reliable method for screening of this virus in human population. Present investigation describes the cloning and expression of N22 region of TTV-genome and the use of expressed peptide in development of immunoassay to detect anti-TTV antibodies in serum. Since TTV genotype-1 is more common in India, the serum positive for genotype-1 was used as source of N22 for expression purpose. METHODS: Full length N22 region of ORF1 from TTV genotype-1 was amplified and cloned in pGEM®-T Easy vector. After cloning, the amplicon was transformed and expressed as a fusion protein containing hexa-histidine tag in pET-28a(+) vector using BL21 E. coli cells as host. Expression was conducted both in LB medium as well as ZYP-5052 auto-induction medium. The expressed peptide was purified using metal-chelate affinity chromatography and used as antigen in developing a blot immunoassay. RESULTS: Analysis of translated product by SDS-PAGE and western blotting demonstrated the presence of 25 kDa polypeptide produced after expression. Solubility studies showed the polypeptide to be associated with insoluble fraction. The use of this peptide as antigen in blot assay produced prominent spot on membrane treated with sera from TTV-infected patients. Analysis of sera from 75 patients with liver and renal diseases demonstrated a successful implication of N22 polypeptide based immunoassay in screening sera for anti-TTV antibodies. Comparison of the immunoassay developed using expressed N22 peptide with established PCR method for TTV-DNA detection showed good coherence between TTV-DNA and presence of anti-TTV antibodies in the sera analysed. CONCLUSIONS: This concludes that TTV N22 region may be expressed and safely used as antigen for blot assay to detect anti-TTV antibodies in sera.

Identification of two new antigen epitopes on the putative capsid protein encoded by torque teno sus virus type 1 ORF1.

Torque teno sus virus type 1 (TTSuV1) ORF1 is considered to encode the viral capsid (Cap) protein, which is crucial for the induction of TTSuV1-specific antibodies and protective immunity in the host. Eight monoclonal antibodies (mAbs) directed against the Cap protein were generated and biologically characterized. The immunoreactivity of the Cap protein expressed in transfected 293T cells for these mAbs was determined with an immunoperoxidase monolayer assay. The antigen epitopes of the Cap protein were mapped using these mAbs and truncated Cap proteins expressed in Escherichia coli. Fine epitope mapping was then performed with a panel of synthesized polypeptides. All the mAbs reacted with the Cap protein C fragment expressed in E. coli. One antigenic epitope of the Cap protein, which reacted with seven mAbs, had the polypeptide sequence (536)HPKYAGQGGGYTT(548), whereas another epitope recognized by the 1E9 mAb had the polypeptide sequence (549)EIGHQGITAASLR(561). It is interesting that the two new epitopes are adjacent, but mutually independent. This study should facilitate further investigation of the antigenic differences and enable the differential diagnosis of the virus.

Preliminary epitope mapping of Torque teno sus virus 1 and 2 putative capsid protein and serological detection of infection in pigs.

The aim of this work is to identify antigenic regions within the ORF1 protein of Torque teno sus virus 1 (TTSuV1) and Torque teno virus sus 2 (TTSuV2) that could be used as antigens to detect virus-specific antibodies following infection in pigs. Protein sequences of TTSuV ORF1 genes were analysed to predict linear antigenic epitopes. Synthesized peptides were analysed for serological reactivity with swine sera. Such an antigenic region was identified at the C terminus of the ORF1 protein of both viruses and showed serological reactivity with 78 % (TTSuV1) and 88 % (TTSuV2) of swine sera. An ELISA with an immunodominant peptide as antigen was used to examine the sera of piglets, aged 4-20 weeks, and adults. Results indicated that TTSuV1- and TTSuV2-specific antibodies were detectable at 4 weeks. Antibody titres increased from week 10 and peaked at week 20. A relatively high antibody titre persisted to adulthood.

Antigenic diversity and seroprevalences of Torque teno viruses in children and adults by ORF2-based immunoassays.

Torque teno viruses (TTVs) circulate widely among humans, causing persistent viraemia in healthy individuals. Numerous TTV isolates with high genetic variability have been identified and segregated into 29 species of five major phylogenetic groups. To date, the diversity of TTV sequences, challenges in protein expression and the subsequent lack of serological assays have hampered TTV seroprevalence studies. Moreover, the antigenic relationships of different TTVs and their specific seroprevalences in humans remain unknown. For five TTV strains--belonging to different species of four genogroups--we developed, using recombinant glutathione S-transferase (GST)-fused TTV ORF2 proteins, glutathione-GST capture enzyme immunoassays (EIAs) detecting antibodies towards conformational epitopes. We then analysed serum samples from 178 healthy adults and 108 children; IgG reactivities were observed either towards a single strain or towards multiple strains, which pointed to antigenic distinction of TTV species. The overall seroprevalence for the five TTVs peaked at 43 % (18 of 42) in children 2-4 years of age, subsequently declined, and again reached 42 % (74 of 178) among adults. TTV6 species-specific IgG predominated in children, whereas that for TTV13 predominated in adults. During a 3 year follow-up of the same children, both species-specific seroconversions and seroreversions occurred. This is the first EIA-based study of different TTVs, providing a new approach for seroepidemiology and diagnosis of TTV infections. Our data suggest that different TTVs in humans may differ in antiviral antibody profiles, infection patterns and epidemiology.

Emergence of exhausted B cells in asymptomatic HIV-1-infected patients naïve for HAART is related to reduced immune surveillance.

Alterations of B cell subpopulations have been described up to date as characterizing advanced stage of HIV-1 infection. However, whether such defects are relevant in subjects with a preserved number of CD4⁺ T cells (>350 cells/µL) is unclear. In a cross-sectional study, we investigated if signs of B cells exhaustion and impaired viral immune surveillance are present in a cohort of 43 asymptomatic HIV-1-infected patients with preserved CD4⁺ T cell counts (>350 cells/µL) and highly active antiretroviral therapy (HAART) untreated. A dramatic expansion of exhausted tissue-like memory B cells (CD10⁻CD21(low)CD27⁻) was observed. B cells alteration was related to an increase in Torque teno virus (TTV) load, used as surrogate marker of immune function. Successfully HAART-treated patients showed normalization of B cell subpopulations frequency and TTV load. These results provide new insights on B cell in HIV-1 infection and show that development of B cell abnormalities precedes CD4⁺ T cell decline.