Global Diversity within and between Human Herpesvirus 1 and 2 Glycoproteins

Human herpes simplex viruses 1 and 2 (HSV-1 and HSV-2) are large-genome DNA viruses that establish a persistent infection in sensory neurons and commonly manifest with recurring oral or genital erosions that transmit virus. HSV encodes 12 predicted glycoproteins that serve various functions, including cellular attachment, entry, and egress. Glycoprotein G is currently the target of an antibody test to differentiate HSV-1 from HSV-2; however, this test has shown reduced capacity to differentiate HSV strains in East Africa. Until the recent availability of 26 full-length HSV-1 and 36 full-length HSV-2 sequences, minimal comparative information was available for these viruses. In this study, we use a variety of sequence analysis methods to compare all available sequence data for HSV-1 and HSV-2 glycoproteins, using viruses isolated in Europe, Asia, North America, the Republic of South Africa, and East Africa. We found numerous differences in diversity, nonsynonymous/synonymous substitution rates, and recombination rates between HSV-1 glycoproteins and their HSV-2 counterparts. Phylogenetic analysis revealed that while most global HSV-2 glycoprotein G sequences did not form clusters within or between continents, one clade (supported at 60.5%) contained 37% of the African sequences analyzed. Accordingly, sequences from this African subset contained unique amino acid signatures, not only in glycoprotein G, but also in glycoproteins I and E, which may account for the failure of sensitive antibody tests to distinguish HSV-1 from HSV-2 in some African individuals. Consensus sequences generated in the study can be used to improve diagnostic assays that differentiate HSV-1 from HSV-2 in global populations.

Human herpes simplex viruses 1 and 2 (HSV-1 and HSV-2) are large DNA viruses associated with recurring oral or genital erosions that transmit virus. Up to 12 HSV-1 and HSV-2 glycoproteins are involved in HSV cell entry or are required for viral spread in animals, albeit some are dispensable for replication in vitro. The recent availability of comparable numbers of full-length HSV-1 and HSV-2 sequences enabled comparative analysis of gene diversity of glycoproteins within and between HSV types. Overall, we found less glycoprotein sequence diversity within HSV-2 than within the HSV-1 strains studied, while at the same time, several HSV-2 glycoproteins were evolving under less selective pressure. Because HSV glycoproteins are the focus of antibody tests to detect and differentiate between infections with the two strains and are constituents of vaccines in clinical-stage development, these findings will aid in refining the targets for diagnostic tests and vaccines.