Phylogenetic approach to recover integration dates of latent HIV sequences within-host

Significance

Studies characterizing within-host latent HIV sequence diversity have yielded insight into reservoir dynamics and persistence. Our understanding of these processes, however, can be further enhanced if reservoir diversity is interpreted in context of HIV’s within-host evolutionary history. Approaches to infer the original establishment (i.e., integration) dates of individual within-host latent HIV lineages would be particularly useful in this regard. We describe a phylogenetic framework to infer latent HIV ages from viral sequence information and apply it to latent HIV sequences sampled up to 10 y on suppressive therapy to yield insights into HIV reservoir dynamics. The ability to infer within-host latent HIV ages from sequence information has broad potential applications that may advance us toward an HIV cure.

Abstract

Given that HIV evolution and latent reservoir establishment occur continually within-host, and that latently infected cells can persist long-term, the HIV reservoir should comprise a genetically heterogeneous archive recapitulating within-host HIV evolution. However, this has yet to be conclusively demonstrated, in part due to the challenges of reconstructing within-host reservoir establishment dynamics over long timescales. We developed a phylogenetic framework to reconstruct the integration dates of individual latent HIV lineages. The framework first involves inference and rooting of a maximum-likelihood phylogeny relating plasma HIV RNA sequences serially sampled before the initiation of suppressive antiretroviral therapy, along with putative latent sequences sampled thereafter. A linear model relating root-to-tip distances of plasma HIV RNA sequences to their sampling dates is used to convert root-to-tip distances of putative latent lineages to their establishment (integration) dates. Reconstruction of the ages of putative latent sequences sampled from chronically HIV-infected individuals up to 10 y following initiation of suppressive therapy revealed a genetically heterogeneous reservoir that recapitulated HIV’s within-host evolutionary history. Reservoir sequences were interspersed throughout multiple within-host lineages, with the oldest dating to >20 y before sampling; historic genetic bottleneck events were also recorded therein. Notably, plasma HIV RNA sequences isolated from a viremia blip in an individual receiving otherwise suppressive therapy were highly genetically diverse and spanned a 20-y age range, suggestive of spontaneous in vivo HIV reactivation from a large latently infected cell pool. Our framework for reservoir dating provides a potentially powerful addition to the HIV persistence research toolkit.