Direct sequence analysis of human herpesvirus 6 (HHV-6) sequences from infants and comparison of HHV-6 sequences from mother/infant pairs.

Direct sequence analysis of polymerase chain reaction-amplified DNA fragments from the large tegument protein (LTP) gene of human herpesvirus 6 (HHV-6) was performed with use of uncultured peripheral blood mononuclear cells (PBMCs) from four mother/infant pairs. In two cases, LTP gene sequences were identical in paired mother/infant specimens, thus suggesting that mother-to-infant transmission of HHV-6 may have occurred. The genetic stability of HHV-6 strains was confirmed by the fact that there was no difference between amplified DNA fragments from sequential PBMC samples from two of two infants analyzed. In contrast, a change in the amplified viral strain was detected in an infant who had reinfection with HHV-6 variant B (HHV-6B). Furthermore, HHV-6B strains concurrently amplified from saliva and PBMCs from an adult were found to be different. The data suggest that HHV-6 may be frequently transmitted from mother-to-infant and that reinfection with HHV-6B may occur.