Torque Teno Virus (TTV) in Renal Transplant Recipients: Species Diversity and Variability

Torque Teno Virus (TTV) is a nonpathogenic and ubiquitous ssDNA virus, a member of the Anelloviridae family. TTV has been postulated as a biomarker in transplant patients. This study aimed to determine the TTV species diversity and variability in renal transplant recipients and to associate species diversity with the corresponding TTV viral load. From 27 recipients, 30 plasma samples were selected. Viral load was determined using two real-time PCR assays, followed by RCA-NGS and ORF1 phylogenetic analysis. The TTV diversity was determined in all samples. Variability was determined in three patients with two sequential samples (pre- and post-transplantation). Most of the samples presented multiple TTV species, up to 15 different species were detected. In the pre-transplant samples (n = 12), the most prevalent species were TTV3 (75%) and TTV13 (75%), and the median number of species per sample was 5 (IQR: 4-7.5). TTV3 was also the most prevalent (56%) in the post-transplant samples (n = 18), and the median number of species was 2 (IQR: 1.8-5.5). No significant correlation between the number of species and viral load was found. The number and type of TTV species showed total variability over time. We report high TTV species diversity in Argentinian recipients, especially in pre-transplant period, with total intra-host variability. However, we found no significant correlation between this high diversity and TTV viral load.

Early start hemodialysis with a catheter may be associated with greater mortality: A propensity score analysis

INTRODUCTION

Deciding when and how to initiate hemodialysis (HD) is still controversial. An early start (ES) seems to show a lack of benefit. "Lead time bias" and comorbidities have been associated with different outcomes in ES groups. On the other hand, it is well accepted that the impact the type of vascular access (VA) has on patient survival. Our aim was to evaluate survival with early start (ES) versus late start (LS) on HD, taking into account the vascular access (VA) used.

METHODS

Between 01/1995 and 06/2018, 503 incidental patients initiated HD at our Dialysis Unit. eGFR was estimated by the CKD-EPI equation. Diabetes mellitus (DM), coronary disease (CD), and peripheral vascular disease (PVD) were considered comorbid conditions. According to eGFR and VA, patients were divided into four groups: G1: ES (eGFR > 7 mL/min) with catheter (ES + C), G2: ES with fistula or graft (F/G) (ES + F/G), G3: LS (eGFR< 7 mL/min) with catheter (LS + C), and G4: LS with F/G (LS + F/G). The cut-off value to define ES or LS was based on median eGFR for these 503 patients. We compared patient's survival rates by Kaplan-Meier and log-rank test. The four groups were compared before and after matching with propensity scores (PS). Cox analysis was performed to determine the impact of predictors of mortality.

RESULTS

Median eGFR was 7 (5.3-9.5) mL/min/1.73 m2 , median follow-up time was 30.9 (13-50) months, 52.1% had F/G access at entry, and 46.9% died during the observation period. Among the four groups, the ES + C were significantly older, and there were more diabetics and comorbid conditions, while phosphatemia, iPTH, albumin, and hemoglobin were significantly higher in the LS groups. Before propensity score (PS) matching, the ES + C group had a poor survival rate (p < 0.0001), while LS + F/G access had the best survival. After PS, a total of 180 patients were selected in the same four groups and ES + C kept showing a statistically significant poorer survival. Multivariate analysis revealed that ES + C was an independent predictor of mortality.

CONCLUSION

In this retrospective study, ES + C on HD was associated with a higher mortality rate than LS. This association persisted after PS matching.

Prospective cohort study of Torque Teno Virus (TTV) viral load kinetics and the association with graft rejection in renal transplant patients

INTRODUCTION

Graft survival is mainly determined by rejections and infectious complications in transplant recipients. Torque Teno Virus (TTV), a nonpathogenic and ubiquitous single-stranded DNA virus, has been proposed as a biomarker of the immune status in transplant patients. This study aimed to determine the correlation between a Home-Brew TTV PCR and R-GENE®PCR; the TTV viral load kinetics in renal transplant recipients and the association with graft rejection.

MATERIALS AND METHODS

Prospective cohort study on 107 adult renal transplant recipients. TTV viral load was determined in 746 plasma samples collected before and after renal transplantation by a Home-Brew PCR and a commercial PCR (R-GENE®PCR). Associations of TTV viral load with graft rejections were analyzed.

RESULTS

Agreement of both PCR assays was 93.2% and Pearson correlation coefficient was r: 0.902 (95%CI: 0.8881-0.9149, p < 0.0001). TTV viral load kinetics showed an initial gradual increase reaching a peak at 3 months. This highest value was followed by a slight decrease, reaching a plateau significantly higher than the initial baseline at 6 months (p < 0.0001). Between (181-270) days post-transplantation, TTV median viral load in patients with graft rejection was significantly lower, 3.59 Log₁₀ copies/mL (by Home-Brew PCR) and 3.10 Log₁₀ copies/mL (by R-GENE®PCR) compared to patients without graft rejection (6.14 and 5.96 Log₁₀ copies/mL, respectively).

CONCLUSIONS

Significantly lower TTV viral load was observed in patients with renal rejection occurring at a median of 243 days post-transplantation. Given the dynamic behavior of TTV viral load post-transplantation, cut-off values for risk stratification to predict rejection might be determined in relation to the post-transplant period.