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Number of HIV-1 founder variants is determined by the recency of the source partner infection.

ABSTRACT: During sexual transmission, the high genetic diversity of HIV-1 within an individual is frequently reduced to one founder variant that initiates infection. Understanding the drivers of this bottleneck is crucial to developing effective infection control strategies. Little is known about the importance of the source partner during this bottleneck. To test the hypothesis that the source partner affects the number of HIV founder variants, we developed a phylodynamic model calibrated using genetic and epidemiological data on all existing transmission pairs for whom the direction of transmission and the infection stage of the source partner are known. Our results suggest that acquiring infection from someone in the acute (early) stage of infection increases the risk of multiple-founder variant transmission compared with acquiring infection from someone in the chronic (later) stage of infection. This study provides the first direct test of source partner characteristics to explain the low frequency of multiple-founder strain infections.

SUBMITTER: Villabona-Arenas CJ

PROVIDER: S-EPMC7116289 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Number of HIV-1 founder variants is determined by the recency of the source partner infection.

Villabona-Arenas Ch Julián CJ Hall Matthew M Lythgoe Katrina A KA Gaffney Stephen G SG Regoes Roland R RR Hué Stéphane S Atkins Katherine E KE

Science (New York, N.Y.) 20200701 6499

During sexual transmission, the high genetic diversity of HIV-1 within an individual is frequently reduced to one founder variant that initiates infection. Understanding the drivers of this bottleneck is crucial to developing effective infection control strategies. Little is known about the importance of the source partner during this bottleneck. To test the hypothesis that the source partner affects the number of HIV founder variants, we developed a phylodynamic model calibrated using genetic a ...[more]

PMID: 32631894

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Project description:Identifying recent HIV infection cases has important public health and clinical implications. It is essential for estimating incidence rates to monitor epidemic trends and evaluate the effectiveness of interventions. Detecting recent cases is also important for HIV prevention given the crucial role that recently infected individuals play in disease transmission, and because early treatment onset can improve the clinical outlook of patients while reducing transmission risk. Critical to this enterprise is the development and proper assessment of accurate classification assays that, based on cross-sectional samples of viral sequences, help determine infection recency status. In this work we assess some of the biases present in the evaluation of HIV recency classification algorithms that rely on measures of within-host viral diversity. Particularly, we examine how the time since infection (TSI) distribution of the infected subjects from which viral samples are drawn affect performance metrics (e.g., area under the ROC curve, sensitivity, specificity, accuracy and precision), potentially leading to misguided conclusions about the efficacy of classification assays. By comparing the performance of a given HIV recency assay using six different TSI distributions (four simulated TSI distributions representing different epidemic scenarios, and two empirical TSI distributions), we show that conclusions about the overall efficacy of the assay depend critically on properties of the TSI distribution. Moreover, we demonstrate that an assay with high overall classification accuracy, mainly due to properly sorting members of the well-represented groups in the validation dataset, can still perform notoriously poorly when sorting members of the less represented groups. This is an inherent issue of classification and diagnostics procedures that is often underappreciated. Thus, this work underscores the importance of acknowledging and properly addressing evaluation biases when proposing new HIV recency assays.

Project description:Transmission of multiple founder variants has been associated with faster HIV disease progression. Many studies have attempted to determine the number of founder variants, mainly by analysis of sequence diversity and/or tree topology from acutely HIV-infected individuals. We hypothesized that adding sequence data collected from source partners might improve resolution and characterization of transmission events. Blood plasma samples were collected from both the source and recipient in thirty epidemiologically- and phylogenetically linked transmission pairs. All were men who have sex with men, sampled on average 70 days (range 11-170) after the recipient's estimated date of infection. Next generation sequencing (454 FLX, Roche) of HIV-1 env (C2-V3) was performed for all samples. Inspection of sequence alignments, highlighter plots, phylogenetic tree topologies and sequence diversity were used to determine the multiplicity of founder viruses with and without the inclusion of source data. Using only recipient sequence data, we were able to resolve multiplicity in twenty-six of the thirty transmission pairs (87 percent). Among them, five presented with a high viral diversity at baseline (>0.10 subst/site), consistent with multiple founders. By incorporating sequence data collected from the source partner, we were able to characterize all thirty transmission pairs. Overall, sixteen transmission events (53.3 percent) involved multiple founders. Results obtained by combining sequence data from recipient and source were congruent for nineteen of the twenty-six (73 percent) cases where conclusions were made using only recipient sequence data. The multiplicity of founders was associated with significantly higher HIV RNA levels (P?=?0.04). To further evaluate the transmission bottleneck, we focused on single founder transmissions (fourteen of the thirty), and identified four recipients (28.6 percent) that had founder variants that were inferred to arise from minority viral populations in the source. These source clades ranged from 1.0 to 5.4 percent of the sampled population. Incorporating sequence data from the source increased of the ability to determine the multiplicity of founder variants, reduced misclassification, and allowed us to infer the transmission of minority variants.

Project description:HIV-1 transmission is associated with a severe bottleneck in which a limited number of variants from a pool of genetically diverse quasispecies establishes infection. The IAVI protocol C cohort of discordant couples, female sex workers, other heterosexuals and men who have sex with men (MSM) present varying risks of HIV infection, diverse HIV-1 subtypes and represent a unique opportunity to characterize transmitted/founder viruses (TF) where disease outcome is known. To identify the TF, the HIV-1 repertoire of 38 MSM participants' samples was sequenced close to transmission (median 21 days post infection, IQR 18-41) and assessment of multivariant infection done. Patient derived gag genes were cloned into an NL4.3 provirus to generate chimeric viruses which were characterized for replicative capacity (RC). Finally, an evaluation of how the TF virus predicted disease progression and modified the immune response at both acute and chronic HIV-1 infection was done. There was higher prevalence of multivariant infection compared with previously described heterosexual cohorts. A link was identified between multivariant infection and replicative capacity conferred by gag, whereby TF gag tended to be of lower replicative capacity in multivariant infection (p = 0.02) suggesting an overall lowering of fitness requirements during infection with multiple variants. Notwithstanding, multivariant infection was associated with rapid CD4+ T cell decline and perturbances in the CD4+ T cell and B cell compartments compared to single variant infection, which were reversible upon control of viremia. Strategies aimed at identifying and mitigating multivariant infection could contribute toward improving HIV-1 prognosis and this may involve strategies that tighten the stringency of the transmission bottleneck such as treatment of STI. Furthermore, the sequences and chimeric viruses help with TF based experimental vaccine immunogen design and can be used in functional assays to probe effective immune responses against TF.

Dataset Information

Number of HIV-1 founder variants is determined by the recency of the source partner infection.

Publications

Number of HIV-1 founder variants is determined by the recency of the source partner infection.

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