IgG subclasses and DNA detection of HHV‐6 and HHV‐7 in healthy individuals

Human herpesvirus 6 (HHV‐6) and 7 (HHV‐7) are common opportunistic agents in immunocompromised hosts, although infection with HHV‐6 and HHV‐7 can also be observed in immunocompetent hosts. Despite similar biology and epidemiology, this study evaluated differences in the IgG subclass distribution associated with HHV‐6 and HHV‐7 in seropositive, healthy persons. The identified subclasses were also compared with the detection of HHV‐6 and HHV‐7 DNA. For these assays, sera, plasma, and saliva samples were obtained from 40 healthy blood donors in Argentina who were seropositive for both HHV‐6 and HHV‐7. HHV‐6 and HHV‐7 DNA were detected in saliva and plasma samples using nested PCR, and specific IgG subclasses were determined using immunofluorescent assays of sera samples. HHV‐7 DNA was detected in 90% of all plasma samples and in 100% of saliva samples. In contrast, HHV‐6 DNA was not detected in any of the plasma samples, and it was detected in only 6 of 40 saliva samples. Determination of IgG subclass distributions showed that HHV‐6 was restricted to IgG1, whereas HHV‐7 IgG subclasses included two groups, one restricted only to IgG1 and the other to IgG1 and IgG3. These results demonstrate the differences between HHV‐6 and HHV‐7 DNA range detection in saliva and plasma samples, as well as the IgG subclass patterns for each virus type, in healthy persons in Argentina. J. Med. Virol. 82:1679–1683, 2010. 2010 Wiley‐Liss, Inc.