Serum Torque Teno Virus DNA Titer in Idiopathic Pulmonary Fibrosis Patients with Acute Respiratory Worsening

Objective Acute respiratory worsening is defined as the unexpected rapid deterioration of idiopathic pulmonary fibrosis (IPF), and idiopathic acute respiratory worsening is known as an acute exacerbation of IPF. Torque teno virus (TTV) is a circular single-stranded DNA virus whose pathological significance remains unclear. The aim of the present study was to investigate the prevalence and titer of TTV DNA in IPF patients with acute respiratory worsening. Methods The serum TTV DNA titer was measured using real-time PCR in nine IPF patients (two treated with steroids and immunosuppressants; seven treated without steroids or immunosuppressants) who developed acute worsening, including five patients with acute exacerbation. The serum TTV DNA titer was also measured in eight stable IPF cases and four IPF cases of lung cancer. In addition, in order to examine time course changes in the TTV DNA titer, the titer was measured more than once, with an interval of four weeks or longer, in eight patients. Results Among the nine IPF patients with acute worsening, the TTV DNA titer was above 1×106 copies/mL in two subjects without acute exacerbation who had been continuously treated with steroids and immunosuppressants. Meanwhile, the mean TTV DNA titer was 2.4±2.6 (×104 copies/mL) in the five patients with acute exacerbation and 3.1±3.4 (×104 copies/mL) in the eight patients with stable IPF. Moreover, the TTV DNA titers were increased in all three IPF patients who started treatment with steroids and immunosuppressants. Conclusion Our results suggest that it is unlikely that TTV is directly involved in the onset of acute exacerbation of IPF and that the serum TTV DNA titer potentially reflects the immunosuppressive state of the host due to treatment.