Genetic variations of human herpesvirus 7 by analysis of glycoproteins B and H, and R2‐repeat regions

Abstract

Clinical isolates of human herpesvirus 7 (HHV-7) from the saliva of healthy individual were investigated for genetic variations in the regions of two immediate-early (IE) genes, the glycoprotein B (gB) and glycoprotein H (gH) genes, and in R2-repeat. The genomic DNA of 24 isolates from citizens of Thailand, Japan, and the United States was amplified to detect size variations in the IE-1 and IE-2 loci, but none was observed, suggesting that there was no deletion or insertion in these genes, in contrast with an IE gene of human herpesvirus 6 (HHV-6). The sequences of the gB gene from isolates acquired from 5 Japanese and 8 Thai subject were then compared with those of American strains JI and RK with respect to codons that are known to differentiate gB alleles. All the isolates were found to have gB allele C except for the JI strain, which has allele F. Variability was also observed in five specific gH codons, resulting in 6 different groups. The HHV-7 isolates might be classified into two major genetic variants by combining their gB and gH allelic groupings. In the present study, only JI belonged to variant 1, while the rest of the isolates appeared to belong to variant 2. In the R2-repeat region, size heterogeneities were observed among the 24 isolates, due to different repeat numbers (17, 15, 14, 13, or 12 repeats). Therefore, we used the R2-repeat to identify the origins of isolates in a study of HHV-7 transmission, and found HHV-7 to be transmitted within a family from both mothers and fathers to their children.

Genetic variation of glycoproteins B and H of human herpesvirus 7 in Hong Kong

“…Therefore, these glycoproteins are expected to be a major target for immunologic response, and to be under a strong selection pressure for genetic diversity [Banks et al, 1989;Urban et al, 1992;Liu et al, 1993;Takeda et al, 1996]. The available data, however, although still limited, suggest that the gB and gH of HHV-7 are highly conserved [Franti et al, 1998[Franti et al, , 1999Thawaranantha et al, 2002]. We verified this finding by examining a series of isolates collected in Hong Kong, and the overall results were in line with results published previously.…”

“…They were designated gH-HK-1 to gH-HK-6 based on their frequency of occurrence. According to the classification system proposed by Thawaranantha et al [2002], gH-HK-1, HK-3, HK-4, HK-5, and HK-6 belonged to gH allele group B, whereas gH-HK-2 belonged to gH allele group C (Table II).…”

“…Sequencing reactions were carried out according to the manufacturer's protocol (BigDye Terminator Cycle Sequencing Kit version 3.1; Applied Biosystems, Foster City, CA), and run on the ABI Prism 3100 Genetic Analyzer (Applied Biosystems). This fragment comprising codons 108-420 was selected for nucleotide sequence analysis as it contains all signature codons important for allele group determination [Franti et al, 1998;Thawaranantha et al, 2002].…”

“…The entire HHV-7 DNA sequences for two strains, JI [Nicholas, 1996] and RK [Megaw et al, 1998] have been reported. To date, only a few studies have examined genetic variability on selected regions of the genome [Franti et al, 1998[Franti et al, , 1999Thawaranantha et al, 2002]. Previous data from Franti et al [1999] and Thawaranantha et al [2002] indicated the potential of using the genetic variations at glycoprotein B (gB) and glycoprotein H (gH) as markers for studying population movement.…”

“…To date, only a few studies have examined genetic variability on selected regions of the genome [Franti et al, 1998[Franti et al, , 1999Thawaranantha et al, 2002]. Previous data from Franti et al [1999] and Thawaranantha et al [2002] indicated the potential of using the genetic variations at glycoprotein B (gB) and glycoprotein H (gH) as markers for studying population movement. In addition, a thorough understanding of the genetic variability of HHV-7 genome is crucial for designing diagnostic assays as well as for conducting epidemiologic investigations.…”