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.