Whole genome deep sequencing of HIV-1 reveals the impact of early minor variants upon immune recognition during acute infection.

Deep sequencing technologies have the potential to transform the study of highly variable viral pathogens by providing a rapid and cost-effective approach to sensitively characterize rapidly evolving viral quasispecies. Here, we report on a high-throughput whole HIV-1 genome deep sequencing platform that combines 454 pyrosequencing with novel assembly and variant detection algorithms. In one subject we combined these genetic data with detailed immunological analyses to comprehensively evaluate viral evolution and immune escape during the acute phase of HIV-1 infection. The majority of early, low frequency mutations represented viral adaptation to host CD8+ T cell responses, evidence of strong immune selection pressure occurring during the early decline from peak viremia. CD8+ T cell responses capable of recognizing these low frequency escape variants coincided with the selection and evolution of more effective secondary HLA-anchor escape mutations. Frequent, and in some cases rapid, reversion of transmitted mutations was also observed across the viral genome. When located within restricted CD8 epitopes these low frequency reverting mutations were sufficient to prime de novo responses to these epitopes, again illustrating the capacity of the immune response to recognize and respond to low frequency variants. More importantly, rapid viral escape from the most immunodominant CD8+ T cell responses coincided with plateauing of the initial viral load decline in this subject, suggestive of a potential link between maintenance of effective, dominant CD8 responses and the degree of early viremia reduction. We conclude that the early control of HIV-1 replication by immunodominant CD8+ T cell responses may be substantially influenced by rapid, low frequency viral adaptations not detected by conventional sequencing approaches, which warrants further investigation. These data support the critical need for vaccine-induced CD8+ T cell responses to target more highly constrained regions of the virus in order to ensure the maintenance of immunodominant CD8 responses and the sustained decline of early viremia.

Acute HIV-1 infection: what's new? Where are we going?

This supplemental issue of the Journal of Infectious Diseases is devoted to the important topic of primary human immunodeficiency virus type 1 (HIV-1) infection. It was prompted by the planning of the Acute HIV-1 Infection Meeting in Boston in September 2009, at which leading scientists and practitioners gathered to discuss new insights into the early, critical events of HIV-1 infection. The reviews that follow underline the current state of the field with regard to transmission biology of HIV-1; the clinical presentation, diagnosis, and management of primary HIV-1 infection; the pathogenesis of primary HIV-1 infection; and innate and adaptive immune responses to the virus. We trust that these findings have the potential to influence the development of effective vaccine strategies.

Differential regulation of toll-like receptor pathways in acute and chronic HIV-1 infection.

OBJECTIVE AND DESIGN: The objective of this study was to determine changes in toll-like receptor (TLR) responses of monocytes, myeloid dendritic cells and plasmacytoid dendritic cells during primary and chronic HIV-1 infection. TLRs serve as important innate receptors to sense pathogens, and have been implicated in mediating immune activation in HIV-1 infection. Studies assessing the consequences of HIV-1 infection on the ability of innate immune cells to respond to TLR stimulation have come to varying conclusions. METHODS: Using intracellular flow cytometry, cytokine production by cryopreserved peripheral blood mononuclear cells from healthy controls and HIV-1-infected individuals were examined after TLR stimulation. RESULTS: We observed that the effect of HIV-1 infection on TLR responses not only depended on the stage of HIV-1 infection, but was also dependent on the individual receptor and cell type examined. Monocyte and myeloid dendritic cell responses to TLR8 stimulation were associated with HIV-1 viral load and CD4 T-cell count, whereas plasmacytoid dendritic cell responses to TLR7 stimulation were not. Responses to TLR2 stimulation were not affected by HIV-1 infection, whereas responses to TLR9 stimulation were universally decreased in all HIV-1-infected individuals examined regardless of treatment or clinical parameters. CONCLUSION: Responsiveness to TLR7/8 stimulation, which have been shown to recognize HIV-1 ssRNA, did not decrease in chronic infection, and may represent a contributing factor to ongoing T-cell immune activation in the setting of chronic viremic HIV-1 infection.