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Frequent and variable cytotoxic-T-lymphocyte escape-associated fitness costs in the human immunodeficiency virus type 1 subtype B Gag proteins.

ABSTRACT: Cytotoxic-T-lymphocyte (CTL) escape mutations undermine the durability of effective human immunodeficiency virus type 1 (HIV-1)-specific CD8(+) T cell responses. The rate of CTL escape from a given response is largely governed by the net of all escape-associated viral fitness costs and benefits. The observation that CTL escape mutations can carry an associated fitness cost in terms of reduced virus replication capacity (RC) suggests a fitness cost-benefit trade-off that could delay CTL escape and thereby prolong CD8 response effectiveness. However, our understanding of this potential fitness trade-off is limited by the small number of CTL escape mutations for which a fitness cost has been quantified. Here, we quantified the fitness cost of the 29 most common HIV-1B Gag CTL escape mutations using an in vitro RC assay. The majority (20/29) of mutations reduced RC by more than the benchmark M184V antiretroviral drug resistance mutation, with impacts ranging from 8% to 69%. Notably, the reduction in RC was significantly greater for CTL escape mutations associated with protective HLA class I alleles than for those associated with nonprotective alleles. To speed the future evaluation of CTL escape costs, we also developed an in silico approach for inferring the relative impact of a mutation on RC based on its computed impact on protein thermodynamic stability. These data illustrate that the magnitude of CTL escape-associated fitness costs, and thus the barrier to CTL escape, varies widely even in the conserved Gag proteins and suggest that differential escape costs may contribute to the relative efficacy of CD8 responses.

SUBMITTER: Boutwell CL

PROVIDER: S-EPMC3624202 | biostudies-literature | 2013 Apr

REPOSITORIES: biostudies-literature

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Frequent and variable cytotoxic-T-lymphocyte escape-associated fitness costs in the human immunodeficiency virus type 1 subtype B Gag proteins.

Boutwell Christian L CL Carlson Jonathan M JM Lin Tien-Ho TH Seese Aaron A Power Karen A KA Peng Jian J Tang Yanhua Y Brumme Zabrina L ZL Heckerman David D Schneidewind Arne A Allen Todd M TM

Journal of virology 20130130 7

Cytotoxic-T-lymphocyte (CTL) escape mutations undermine the durability of effective human immunodeficiency virus type 1 (HIV-1)-specific CD8(+) T cell responses. The rate of CTL escape from a given response is largely governed by the net of all escape-associated viral fitness costs and benefits. The observation that CTL escape mutations can carry an associated fitness cost in terms of reduced virus replication capacity (RC) suggests a fitness cost-benefit trade-off that could delay CTL escape an ...[more]

PMID: 23365420

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Project description:CD8(+) cytotoxic T lymphocytes (CTL) are strong mediators of human immunodeficiency virus type 1 (HIV-1) control, yet HIV-1 frequently mutates to escape CTL recognition. In an analysis of sequences in the Los Alamos HIV-1 database, we show that emerging CTL escape mutations were more often present at lower frequencies than the amino acid(s) that they replaced. Furthermore, epitopes that underwent escape contained amino acid sites of high variability, whereas epitopes persisting at high frequencies lacked highly variable sites. We therefore infer that escape mutations are likely to be associated with weak functional constraints on the viral protein. This was supported by an extensive analysis of one subject for whom all escape mutations within defined CTL epitopes were studied and by an analysis of all reported escape mutations of defined CTL epitopes in the HIV Immunology Database. In one of these defined epitopes, escape mutations involving the substitution of amino acids with lower database frequencies occurred, and the epitope soon reverted back to the sensitive form. We further show that this escape mutation substantially diminished viral fitness in in vitro competition assays. Coincident with the reversion in vivo, we observed the fixation of a mutation 3 amino acids C terminal to the epitope, coincident with the ablation of the corresponding CTL response. The C-terminal mutation did not restore replication fitness reduced by the escape mutation in the epitope and by itself had little effect on replication fitness. Therefore, this C-terminal mutation presumably impaired the processing and presentation of the epitope. Finally, for one persistent epitope, CTL cross-reactivity to a mutant form may have suppressed the mutant to undetected levels, whereas for two other persistent epitopes, each of two mutants showed poor cross-reactivity and appeared in the subject at later time points. Thus, a viral dynamic exists between the advantage of immune escape, peptide cross-reactivity, and the disadvantage of lost replication fitness, with the balance playing an important role in determining whether a CTL epitope will persist or decline during infection.

Dataset Information

Frequent and variable cytotoxic-T-lymphocyte escape-associated fitness costs in the human immunodeficiency virus type 1 subtype B Gag proteins.

Publications

Frequent and variable cytotoxic-T-lymphocyte escape-associated fitness costs in the human immunodeficiency virus type 1 subtype B Gag proteins.

Similar Datasets

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