Monitoring of human herpesvirus-6 and-7 genomes in saliva samples of healthy adults by competitive quantitative PCR

Human herpesviruses-6 and -7 (HHV-6 and HHV-7) are thought to be transmitte d during early infancy through saliva. However, the kinetics of the virus s hedding in saliva of healthy adults, from whom children are assumed to acqu ire the viruses, is mostly unknown. This study was conducted to determine h ow many copies of the genome are secreted in saliva of healthy adults and t o clarify the relationship between viral DNA load and virus isolation of HH V-6 and HHV-7. Competitive PCR was performed using primer sets in the U42 g ene of each viral genome. In saliva samples from 29 healthy adults, HHV-6 a nd HHV-7 DNA was detected in 41.4% and 89.7%, respectively. The average cop y number of the HHV-7 genome in the positive samples was higher than that o f the HHV-6 genome. Follow-up studies of six seropositive individuals for 3 months showed that the amount of HHV-7 DNA was constant in each individual and that "high producers" and "low producers" could be distinguished. By c ontrast, the amount of HHV-6 DNA varied drastically over time in each indiv idual. Although HHV-6 was never isolated from the saliva of any of the six individuals during the follow-up period, HHV-7 was isolated from each indiv idual several times. The amount of HHV-7 DNA tended to be higher at the tim es when the virus was isolated than at the times when the virus was not iso lated. These data demonstrate a striking contrast between HHV-6 and HHV-7 i n the kinetics of genome and virus shedding. (C) 2000 Wiley-Liss, Inc.