Arch Virol (1997) 142: 103—123
Genetic content of a 20.9 kb segment of human herpesvirus 6B
strain Z29 spanning the homologs of human herpesvirus 6A
genes U40—57 and containing the origin
of DNA replication
G. J. Lindquester
, J. J. O’Brian
, E. D. Anton
, C. A. Greenamoyer
P. E. Pellett
, and T. R. Dambaugh
Department of Biology, Rhodes College, Memphis, Tennessee, U.S.A.
National Center for Infectious Diseases, Centers for Disease Control
and Prevention, Atlanta, Georgia, U.S.A. DuPont Merck Pharmaceuticals,
Experimental Station, Wilmington, Delaware, U.S.A.
Accepted July 30, 1996
Summary. A continuous 20.9 kb sequence from human herpesvirus 6 variant
B (HHV-6B) strain Z29 (GenBank accession number L16947) is genetically
colinear with a discrete segment of the human cytomegalovirus (HCMV) UL
region and with HHV-6 variant A (HHV-6A). Short nucleotide sequence deter-
minations at multiple sites within an 8.5 kb region immediately 3 to the 20.9 kb
contig revealed additional colinearity between HHV-6B, HCMV and HHV-6A.
Homology studies with the predicted peptide sequences from 11 complete and 12
partial HHV-6B open reading frames (ORFs) revealed that most encode proteins
conserved to varying degrees in all previously sequenced primate herpesviruses.
HHV-6B homologs were identiﬁed for the HSV-1 ICP18.5, ICP8, UL52, UL24,
UL25 and major capsid protein. Several HHV-6B proteins had limited amino
acid similarity to their positional homologs in other herpesviruses. Each gene
identiﬁed is highly homologous to its HHV-6A counterpart, including two
unique HHV-6 genes predicted to encode membrane-associated glycoproteins.
However, two regions of substantial divergence were noted, one spanning the
origin of replication and the other encoding one of the putative HHV-6-speciﬁc
glycoprotein genes. Substitutions in the latter region lead to predicted diﬀerences
in reading frames and protein lengths among HHV-6 isolates.
Human herpesvirus 6 (HHV-6) was ﬁrst isolated from patients with various
immunodeﬁciencies including AIDS. The virus is ubiquitous in human popula-
tions as a result of seroconversion during early childhood. In addition to its