New Respiratory Viruses and the Elderly

Jartti, Laura; Langen, Henriikka; Söderlund-Venermo, Maria; Vuorinen, Tytti; Ruuskanen, Olli; Jartti, Tuomas

Torque teno virus DNA has been recovered from many tissues and secretions but whether this observation is causally related to clinical symptoms or not has not been demonstrated [14, [113] [114] [115] . TTV is possibly able to replicate in airway tissues [116, 117] and many other tissues e.g. liver and bone marrow [118] . The airways might be the primary route of transmission. TTV is very often detected in blood; the prevalence of TTV DNA in the blood of healthy individuals is approximately 70-90% [119] . A single TTV infection may persist for years and cause chronic viremia [120] [121] [122] . Simultaneous infections by different TTV variants may also occur. TTV might also aggravate the symptoms caused by other respiratory viruses, or then TTV may be an indicator of the disease process as implied by the findings that TTV concentrations in nasal secretions or plasma have a positive correlation with markers of eosinophilic inflammation and a negative correlation with pulmonary function in asthma [15] . Also, the severity of bronchiectasis and of idiopathic pulmonary fibrosis correlate with high TTV concentrations [115] . The association between TTV and disease, could be based on a direct viral effect or be mediated by inflammatory processes that predispose to virus replication. Indeed, TTV replication kinetics have been used as a marker of immune reconstitution after suppression [123] . Although multiple TTV variants cause problems in detection, the diagnosis of TTV infections is based on PCR; serology will apparently not be developed in the near future [124] .