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The route of HIV escape from immune response targeting multiple sites is determined by the cost-benefit tradeoff of escape mutations.

ABSTRACT: Cytotoxic T lymphocytes (CTL) are a major factor in the control of HIV replication. CTL arise in acute infection, causing escape mutations to spread rapidly through the population of infected cells. As a result, the virus develops partial resistance to the immune response. The factors controlling the order of mutating epitope sites are currently unknown and would provide a valuable tool for predicting conserved epitopes. In this work, we adapt a well-established mathematical model of HIV evolution under dynamical selection pressure from multiple CTL clones to include partial impairment of CTL recognition, [Formula: see text], as well as cost to viral replication, [Formula: see text]. The process of escape is described in terms of the cost-benefit tradeoff of escape mutations and predicts a trajectory in the cost-benefit plane connecting sequentially escaped sites, which moves from high recognition loss/low fitness cost to low recognition loss/high fitness cost and has a larger slope for early escapes than for late escapes. The slope of the trajectory offers an interpretation of positive correlation between fitness costs and HLA binding impairment to HLA-A molecules and a protective subset of HLA-B molecules that was observed for clinically relevant escape mutations in the Pol gene. We estimate the value of [Formula: see text] from published experimental studies to be in the range (0.01-0.86) and show that the assumption of complete recognition loss ([Formula: see text]) leads to an overestimate of mutation cost. Our analysis offers a consistent interpretation of the commonly observed pattern of escape, in which several escape mutations are observed transiently in an epitope. This non-nested pattern is a combined effect of temporal changes in selection pressure and partial recognition loss. We conclude that partial recognition loss is as important as fitness loss for predicting the order of escapes and, ultimately, for predicting conserved epitopes that can be targeted by vaccines.

SUBMITTER: Batorsky R

PROVIDER: S-EPMC4214571 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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The route of HIV escape from immune response targeting multiple sites is determined by the cost-benefit tradeoff of escape mutations.

Batorsky Rebecca R Sergeev Rinat A RA Rouzine Igor M IM

PLoS computational biology 20141030 10

Cytotoxic T lymphocytes (CTL) are a major factor in the control of HIV replication. CTL arise in acute infection, causing escape mutations to spread rapidly through the population of infected cells. As a result, the virus develops partial resistance to the immune response. The factors controlling the order of mutating epitope sites are currently unknown and would provide a valuable tool for predicting conserved epitopes. In this work, we adapt a well-established mathematical model of HIV evoluti ...[more]

PMID: 25356981

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Project description:BackgroundAmong HIV+ patients, alcohol use is a highly prevalent risk factor for both HIV transmission and poor adherence to HIV treatment. The large-scale implementation of effective interventions for treating alcohol problems remains a challenge in low-income countries with generalized HIV epidemics. It is essential to consider an intervention's cost-effectiveness in dollars-per-health-outcome, and the long-term economic impact -or "return on investment" in monetary terms.MethodsWe conducted a cost-benefit analysis, measuring economic return on investment, of a task-shifted cognitive-behavioral therapy (CBT) intervention delivered by paraprofessionals to reduce alcohol use in a modeled cohort of 13,440 outpatients in Kenya. In our base-case, we estimated the costs and economic benefits from a societal perspective across a six-year time horizon, with a 3% annual discount rate. Costs included all costs associated with training and administering task-shifted CBT therapy. Benefits included the economic impact of lowered HIV incidence as well as the improvements in household and labor-force productivity. We conducted univariate and multivariate probabilistic sensitivity analyses to test the robustness of our results.ResultsUnder the base case, total costs for CBT rollout was $554,000, the value of benefits were $628,000, and the benefit-to-cost ratio was 1.13. Sensitivity analyses showed that under most assumptions, the benefit-to-cost ratio remained above unity indicating that the intervention was cost-saving (i.e., had positive return on investment). The duration of the treatment effect most effected the results in sensitivity analyses.ConclusionsCBT can be effectively and economically task-shifted to paraprofessionals in Kenya. The intervention can generate not only reductions in morbidity and mortality, but also economic savings for the health system in the medium and long term. The findings have implications for other countries with generalized HIV epidemics, high prevalence of alcohol consumption, and shortages of mental health professionals.Trial registrationThis paper uses data derived from "Cognitive Behavioral Treatment to Reduce Alcohol Use Among HIV-Infected Kenyans (KHBS)" with ClinicalTrials.gov registration NCT00792519 on 11/17/2008; and preliminary data from "A Stage 2 Cognitive-behavioral Trial: Reduce Alcohol First in Kenya Intervention" ( NCT01503255 , registered on 12/16/2011).

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The route of HIV escape from immune response targeting multiple sites is determined by the cost-benefit tradeoff of escape mutations.

Publications

The route of HIV escape from immune response targeting multiple sites is determined by the cost-benefit tradeoff of escape mutations.

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