Torquetenovirus viremia kinetics after autologous stem cell transplantation are predictable and may serve as a surrogate marker of functional immune reconstitution

BackgroundIt is common experience that retreating patients too early after a course of intensive chemotherapy predisposes to opportunistic infections despite apparently normal lymphocyte levels.ObjectivesThe extent of replication of persistent viruses that cause no obvious disease (and hence need no treatment) might better define when a patient has recovered from functional immune deficiency.Study designWe used real-time polymerase chain reaction to monitor the kinetics of plasma torquetenovirus (TTV) viremia in hematological patients undergoing autologous hematopoietic stem cell transplantation as support to high-dose chemotherapy (HSCT).ResultsIndependently from underlying hematological disease and therapeutic regimen, TTV viremia increased post-HSCT, and this increase paralleled the increase of circulating CD8+CD57+ T lymphocytes, known to represent an indirect marker of functional immune deficiency. Subsequently, within a matter of months, TTV levels returned to baseline values, at a pace that appeared to be constant over time.ConclusionMonitoring of TTV viremia represents a unique opportunity to follow functional immune reconstitution in immunosuppressed patients. Also, the size of the TTV viremia increases resulting from immunosuppressive treatments might be of guidance in determining the appropriate time interval before delivery of a next course of therapy.