Assessment of prevalence and load of torquetenovirus viremia in a large cohort of healthy blood donors

Abstract Objectives Torquetenovirus (TTV) is an emerging marker of functional immune competence with the potential to predict transplant-related adverse events. A large-scale epidemiological study was performed to understand how basal values vary in healthy subjects according to age and gender. Methods We tested plasma from 1017 healthy blood donors aged 18-69 years. The presence and load of TTV were determined by a real-time PCR assay. A sub-cohort of 384 donors was tested for anti-cytomegalovirus IgG antibodies, and 100 subjects were also tested for TTV viremia on a paired whole blood sample. Results The overall prevalence of TTV was 65% (657/1017) with a mean (±standard deviation, SD) growth of 5 ± 4% every 10 years of age increase, but stably higher in males (465/690, 67%) than in females (192/327, 59%). Mean (±SD) TTV load was 2.3 ± 0.7 Log copies/ml with no sex difference. TTV viremia showed modest increases along 10-years age intervals (mean ± SD: 0.3 ± 0.1). TTV viremia in donors sampled two years later remained stable (mean ± SD: 2.3 ± 0.8 versus 2.2 ± 0.7 Log copies between samples). Twenty-six percent (9/34) of blood donors with TTV-negative plasma scored positive when whole blood was tested, and the donors with positive plasma showed a mean (±SD) 1.4 ± 0.5 Log increase in copy numbers when whole blood was tested. Conclusions This study establishes the mean value of TTV viremia in plasma in healthy blood subjects and suggests that ageing causes only minimal increases in TTV viremia.