Identification of envelope glycoproteins H and B homologues of human herpesvirus 7.

The genes encoding the envelope glycoprotein H (gH) and gB homologues were identified by sequencing genomic clones of human herpesvirus-7 (HHV-7), strain JI. A gB cDNA clone from HHV-7 strain AL was also identified. The deduced primary translation products of the gH and gB genes are a protein of 690 amino acids, with a predicted mass of 80.4 kD, and a protein of 822 amino acids, with a predicted mass of 93.3 kD, respectively. Both the predicted proteins have the characteristics of transmembrane glycoproteins, containing signal and transmembrane sequence motifs and characterized by the presence of 10 (gH) and 11 (gB) potential motifs for N-glycosylation. Comparison of amino acid sequence of HHV-7 gH and gB with the homologous sequences of the other human herpesviruses reveals closest homology with HHV-6 (38.8% identity for gH, 56.2% identity for the gB). In addition, significant sequence similarity was also observed between the gH and gB of HHV-7 and the homologs encoded by human cytomegalovirus (21.6% identity for gH, 37.6% identity for gB). No significant differences existed between the gB sequence of the two different HHV-7 strains analyzed. The products of the HHV-7 gH and gB expressed transiently in eukaryotic cells were specifically recognized by an HHV-7-reactive human serum in immunofluorescence assays.