Molecular Evolution of Herpes Simplex Virus 2 Complete Genomes: Comparison between Primary and Recurrent Infections.

Herpes simplex virus 1 (HSV-1) and HSV-2 are large, double-stranded DNA viruses that cause lifelong persistent infections characterized by periods of quiescence and recurrent disease. How HSV evolves within an infected individual experiencing multiple episodes of recurrent disease over time is not known. We determined the genome sequences of viruses isolated from two subjects in the Herpevac Trial for Women who experienced primary HSV-2 genital disease and compared them with sequences of viruses isolated from the subsequent fifth or sixth episode of recurrent disease in the same individuals. Each of the HSV-2 genome sequences was initially obtained using next-generation sequencing and completed with Sanger sequencing. Polymorphisms over the entire genomes were mapped, and amino acid variants resulting from nonsynonymous changes were analyzed based on the secondary and tertiary structures of a previously crystallized protein. A phylogenetic reconstruction was used to assess relationships among the four HSV-2 samples, other North American sequences, and reference sequences. Little genetic drift was detected in viruses shed by the same subjects following repeated reactivation events, suggesting strong selective pressure on the viral genome to maintain sequence fidelity during reactivations from its latent state within an individual host. Our results also demonstrate that some primary HSV-2 isolates from North America more closely resemble the HG52 laboratory strain from Scotland than the low-passage-number clinical isolate SD90e from South Africa or laboratory strain 333. Thus, one of the sequences reported here would be a logical choice as a reference strain for inclusion in future studies of North American HSV-2 isolates.