Exploring Torque Teno Virus-Host Immune Interactions

Background: Torque Teno Virus (TTV) is a ubiquitous component of human virome, not associated with any disease. TTV ability to establish persistent replication without overt clinical symptoms suggests a complex interaction with the host immune system. Aims & Objectives: As its load increases when the immune system is compromised, such as in kidney transplant (KT) recipients, TTV load monitoring has been proposed as a method to assess immunosuppression. Simultaneously to investigate the interaction between TTV and host immune responses in the context of cytokine production may help to understand complex interaction with the host immune system. Methodology: In this prospective study, TTV load was measured in plasma and urine samples from 42 KT recipients, immediately before KT and in the first 150 days after it. Furthermore, respiratory samples were also collected from 97 patients with respiratory changes caused by viruses to see the trend of TTV viral load and compare it with the cytokine expression also to see the trend across different age demographics. Results: Data obtained suggest that TTV could be a relevant marker for evaluating immune status and could be used as a guide to predict the onset of infectious complications in the follow-up of KT recipients. Nevertheless, the study on cytokine profiling showed a significant positive correlation between TTV and the expression levels of key cytokines such as IFNL1 (p = 0.0416) and IFNL2 (p = 0.0007). Conclusions: Since we observed no differences considering distance from transplantation, while we found a changing trend in days before viral infections, we suggest to consider changes over time in the same subjects, irrespective of time distance from transplantation. Other the other hand the nature of interaction between TTV and cytokines expression is at the moment unknown, this upregulation could contribute to the body defence against other pathogens by priming the immune system.