The aim of this study is to determine whether human herpesvirus 6 (HHV-6) and HHV-7 might play an important role in causing interstitial pneumonia in patients who have not undergone transplantation. HHV-6 and HHV-7 DNAs were quantitated by real-time polymerase chain reaction (PCR) in paraffin embedded lung tissues collected from 24 patients having the disease. Control tissues (without fibrosis) were also collected from 19 of the 24 patients. Statistical analysis was carried out by the Wilcoxon signed rank test or the Mann-Whitney U-test. HHV-6 DNA was detected in 3 (12.5%) of the 24 target tissues and 3 (15.8%) of the 19 control tissues, respectively. In contrast, HHV-7 DNA was detected in 19 (79.2%) of the 24 target tissues and 11 (57.9%) of the 19 control tissues. Neither HHV-6 DNA load (P = 0.6395) nor HHV-7 DNA load (P = 0.5966) in target tissues differed between males and females. Neither HHV-6 DNA load (P = 0.9589) nor HHV-7 DNA load (P = 0.7419) in target tissues differed between cases with and without underlying collagen disease. While HHV-6 DNA load did not differ between the target and control tissues (P > 0.9999), the HHV-7 DNA load was significantly higher in the target tissue than in the control tissue (P = 0.0298). This study suggests that HHV-7 may play an important role in causing interstitial pneumonia in patients who are not transplant recipients.
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