The etiology of cytomegalovirus (CMV), human herpesvirus-6 (HHV-6), and Epstein-Barr virus (EBV) reactivation and the potential for complications following cytotoxic chemotherapy in the absence of allogeneic transplantation are not clearly understood. Patients with adult T cell leukemia (ATL) are susceptible to opportunistic infections. In this study, the incidence, kinetics and clinical significance of reactivation of CMV, HHV-6, and EBV in ATL patients were investigated. Viral DNA in a total of 468 plasma samples from 34 patients was quantified using real-time PCR. The probability of CMV, HHV-6, and EBV reactivation by 100 days after the start of chemotherapy was 50.6%, 52.3%, and 21.6%, respectively. Although most CMV reactivations were self-limited, plasma CMV DNA tended to persist or increase if the CMV DNA levels in plasma reached ≥104copies/ml. CMV reactivation was negatively associated with survival, but the P-value for this association was near the borderline of statistical significance (P=0.052). One patient developed fatal interstitial pneumonia concomitant with peak CMV DNA accumulation (1.6×106copies/ml plasma). Most HHV-6 and EBV reactivations were self-limited, and no disease resulting from HHV-6 or EBV was confirmed. HHV-6 and EBV reactivation were not associated with reduced survival (P=0.35 and 0.11, respectively). These findings demonstrated that subclinical reactivation of CMV, HHV-6, and EBV were common in ATL patients receiving chemotherapy. There were differences in the viral reactivation patterns among the three viruses. A CMV load ≥104copies/ml plasma was indicative of subsequent exacerbation of CMV reactivation and developing serious clinical course.
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