Fifteen human herpesvirus 6 (HHV-6) strain variants were analysed by PCR amplifications, restriction enzyme site polymorphism and sequence analyses. Three DNA regions were chosen for study: a fragment of a variable glycoprotein gene (210 bp), the conserved glycoprotein H (gH) gene complete with intergenic sequences (2381 bp) and the 5′ intergenic region with the N-terminal coding sequence of gH up to a polymorphic HI site (427 bp). Infected cell DNA from five laboratory reference strains including GS, U1102, AJ, Z29 and KF were examined together with DNA from peripheral blood blymphocytes infected with HHV-6 reactivated from blood and/or marrow from five bone marrow transplant (BMT) patients. Separate blood and marrow isolates were obtained from four BMT patients. In addition, HHV-6 sequences were examined directly from one of six Hodgkin's lymphomas and six B cell proliferations which contained HHV-6 DNA as detected by PCR amplification. The results show two groups of very closely related but heterogeneous strains which correlate with previous groupings by antigenic and restriction site differences. These are variant A strains (including laboratory strains GS, U1102 and AJ) and variant B strains (including laboratory strains Z29 and KF, the Hodgkin's lymphoma strain, and the nine BMT patient isolates). Variations between the groups were 4 to 6% in nucleotide sequence and 5 to 8.5% in amino acid sequence. Within each group maximum heterogeneity was observed in different genes. Variant A strains differed by 2.0% in the variable glycoprotein gene sequence whereas variant B strains were identical in this region; conversely, variant B strains differed by 2 to 3% in the gH N-terminal and intergenic sequences whereas variant A strains differed there by less than 0.2%. There was evidence for sequence drift independent of selection: relationships between the groups were shown by analyses of amino acid sequence, coding nucleotide sequence as well as intergenic sequence, and the B variant-specific HI site in the gH gene was due to a non-coding nucleotide substitution. There was little evidence for or variation: the gH nucleotide sequence from the uncultured lymphoma strain (first variant B gH gene identified) was almost identical to the gH sequence from four BMT isolates, and matched BMT isolates from blood and marrow were identical or with a single nucleotide substitution. The overall variation observed between the HHV-6 strain groups was similar or less than that seen between human cytomegalovirus strains such as AD169 or Towne, but clearly distinct from the much greater divergence between currently designated herpesvirus species.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error