Loss of viral fitness and cross-recognition by CD8+ T cells limit HCV escape from a protective HLA-B27–restricted human immune response
Eva Dazert, … , Ralf Bartenschlager, Robert Thimme
Eva Dazert, … , Ralf Bartenschlager, Robert Thimme
Published January 12, 2009
Citation Information: J Clin Invest. 2009;119(2):376-386. https://doi.org/10.1172/JCI36587.
View: Text | PDF
Research Article Virology

Loss of viral fitness and cross-recognition by CD8+ T cells limit HCV escape from a protective HLA-B27–restricted human immune response

Abstract

There is an association between expression of the MHC class I molecule HLA-B27 and protection following human infection with either HIV or HCV. In both cases, protection has been linked to HLA-B27 presentation of a single immunodominant viral peptide epitope to CD8+ T cells. If HIV mutates the HLA-B27–binding anchor of this epitope to escape the protective immune response, the result is a less-fit virus that requires additional compensatory clustered mutations. Here, we sought to determine whether the immunodominant HLA-B27–restricted HCV epitope was similarly constrained by analyzing the replication competence and immunogenicity of different escape mutants. Interestingly, in most HLA-B27–positive patients chronically infected with HCV, the escape mutations spared the HLA-B27–binding anchor. Instead, the escape mutations were clustered at other sites within the epitope and had only a modest impact on replication competence. Further analysis revealed that the cluster of mutations is required for efficient escape because a combination of mutations is needed to impair T cell recognition of the epitope. Artificially introduced mutations at the HLA-B27–binding anchors were found to be either completely cross-reactive or to lead to substantial loss of fitness. These results suggest that protection by HLA-B27 in HCV infection can be explained by the requirement to accumulate a cluster of mutations within the immunodominant epitope to escape T cell recognition.

Authors

Eva Dazert, Christoph Neumann-Haefelin, Stéphane Bressanelli, Karen Fitzmaurice, Julia Kort, Jörg Timm, Susan McKiernan, Dermot Kelleher, Norbert Gruener, John E. Tavis, Hugo R. Rosen, Jaqueline Shaw, Paul Bowness, Hubert E. Blum, Paul Klenerman, Ralf Bartenschlager, Robert Thimme

×

Figure 2

Clustering of mutations at TCR contact sites is required for efficient escape from the WT-specific T cell response.

Options: View larger image (or click on image) Download as PowerPoint
Clustering of mutations at TCR contact sites is required for efficient e...
(A) PBMCs from 6 HLA-B27+ individuals with HCV infection that resolved either spontaneously or through therapy were cultured for 14 days in the presence of WT peptide NS5B2841–2849. Cells were then tested for IFN-γ production after 5 hours stimulation with WT or variant peptides at a concentration of 10–5 M. Variants with single or clustered substitutions are grouped. A plus indicates that this mutation occurs in vivo, while a minus indicates that this mutation was not found in vivo. ND, not done. (B) Representative dot blots corresponding to Figure 2A (subject 2) are shown, including titration of the peptides in different concentrations as indicated. Percentages indicate IFN-γ+CD8+ T cells. (C) Levels of cross-recognition observed for each single and clustered escape variant of the HLA-B27–restricted NS5B2841–2849 epitope are compared with the levels of cross-recognition of a number of single or clustered escape variants in HLA-B27– patients described previously by our group (29). The level of cross-recognition for each variant was calculated by dividing the response to the variant peptide at a concentration of 10–5 M by the response to WT peptide at a concentration of 10–5 M. P values were calculated using Mann-Whitney U test. Bars denote mean.