High-programmed death-1 levels on hepatitis C virus-specific T cells during acute infection are associated with viral persistence and require preservation of cognate antigen during chronic infection - PubMed (original) (raw)

Comparative Study

. 2008 Dec 15;181(12):8215-25.

doi: 10.4049/jimmunol.181.12.8215.

Stuart C Ray, Jacquie Astemborski, Jordana Levine, Lin Liu, Kimberly A Dowd, Shalyn Clute, Changyu Wang, Alan Korman, Alessandro Sette, John Sidney, Drew M Pardoll, Andrea L Cox

Affiliations

Comparative Study

High-programmed death-1 levels on hepatitis C virus-specific T cells during acute infection are associated with viral persistence and require preservation of cognate antigen during chronic infection

Alleluiah Rutebemberwa et al. J Immunol. 2008.

Abstract

Hepatitis C virus (HCV) is an important human pathogen that represents a model for chronic infection given that the majority of infected individuals fail to clear the infection despite generation of virus-specific T cell responses during the period of acute infection. Although viral sequence evolution at targeted MHC class I-restricted epitopes represents one mechanism for immune escape in HCV, many targeted epitopes remain intact under circumstances of viral persistence. To explore alternative mechanisms of HCV immune evasion, we analyzed patterns of expression of a major inhibitory receptor on T cells, programmed death-1 (PD-1), from the time of initial infection and correlated these with HCV RNA levels, outcome of infection, and sequence escape within the targeted epitope. We show that the level of PD-1 expression in early HCV infection is significantly higher on HCV-specific T cells from subjects who progress to chronic HCV infection than from those who clear infection. This correlation is independent of HCV RNA levels, compatible with the notion that high PD-1 expression on HCV-specific CD8 T cells during acute infection inhibits viral clearance. Viral escape during persistent infection is associated with reduction in PD-1 levels on the surface of HCV-specific T cells, supporting the necessity of ongoing antigenic stimulation of T cells for maintenance of PD-1 expression. These results support the idea that PD-1 expression on T cells specific for nonescaped epitopes contributes to viral persistence and suggest that PD-1 blockade may alter the outcome of HCV infection.

PubMed Disclaimer

Figures

Figure 1

Figure 1. PD-1 staining patterns for two representative subjects

PD-1 expression on HCV-specific T cells was essentially uniformly positive and generally unimodal. Therefore, the mean levels of PD-1 expression (mean fluorescence intensity, MFI) on the entire multimers positive population of T cells rather than percentage positivity was used as an unbiased estimate of PD-1 expression. The numbers in the top boxes indicate the percentage of isotype control (top row) or PD-1 positive (bottom row) CD8 positive HCV-specific T cells.

Figure 2

Figure 2. PD-1 expression on HCV-specific T cells is higher than on influenza-specific T cells and the general CD8 T cell population regardless of outcome of infection or the phase of infection

The MFI of PD-1 on the T cell surface was compared between HCV specific T cells from subjects with either outcome of infection, control specific T cells and the general CD8 population in the first 180 days of HCV infection (HCV+ acute to chronic or cleared, 2a) and at time points following 180 days of HCV infection (HCV+ chronic or cleared, 2b). The level of PD-1 expression is also higher in acute infection on HCV specific T cells from subjects who remain persistently infected than those who clear HCV infection. Each data point represents the MFI of the PD-1 level on a specific tetramer positive population within an individual.

Figure 3

Figure 3. PD-1 expression on HCV specific T cells stratified by HCV RNA level during early and late infection

HCV RNA levels at the time the T cells were acquired are indicated by colored symbols. Red: >100,000 copies/mL Yellow: 600–100,000 copies/mL Green: <600 copies/mL. Acute infection was defined as time points less than 180 days from initial viremia. PD-1 levels are highly variable in chronic infection. Some HCV-specific T cells from subjects with chronic infection expressed low PD-1 levels in the setting of high circulating HCV RNA levels (Red dots at low PD-1 MFI values).

Figure 4

Figure 4. PD-1 upregulation requires maintenance of intact antigen and restoration of intact antigen following escape is associated with an increase in PD-1 levels

Viral sequence was assessed at initial infection and at multiple subsequent time points at which T cells specific for known antigens were detectable, including those surrounding the time at which the PD-1 levels were found to be low relative to initial PD-1 levels. Levels of PD-1 on T cells specific for epitopes that either underwent substitutions that impaired T cell recognition or remained constant are shown. Time points at which the substituted epitopes were present are indicated with open circles and points at which the initial viral sequence was present are indicated with closed circles. A. Subject 17 recognized three epitopes: 880TL10 and B35-135 underwent substitution in the first six months of infection and 140G remained intact. PD-1 levels decline three and ten fold following substitution of 880TL10 and B35-135, respectively. T cells recognizing 140G demonstrated a three fold increase in PD-1 expression. B. Subject 13 had one HCV specific T cell response that underwent substitution with an associated drop of nearly three fold in PD-1 expression. C. In Subject 175, HCV levels transiently fell to below the limit of quantitation with a decline in PD-1 levels followed by reemergence of high viral titers and an increase in PD-1 levels on T cells specific for the epitope. D. Subject 30. Sequence escape at epitope C63B is associated with a five-fold decline in PD-1 levels. C63B reverted back to the original sequence in association with a six-fold increase in PD-1 expression on the cognate T cells. A2-61 does not undergo substitution and the level of PD-1 expression varies less than two fold. PD-1 levels are maintained constant or increase over time in the absence of viral sequence variation. (E–H) Levels of PD-1 on T cells specific for epitopes that remained constant are shown for four different HCV infected subjects who recognized at least one T cell epitope for which multimers were available. For all four subjects, PD-1 expression on HCV-specific T cells decreases less than two-fold or increases over time.

Figure 4

Figure 4. PD-1 upregulation requires maintenance of intact antigen and restoration of intact antigen following escape is associated with an increase in PD-1 levels

Viral sequence was assessed at initial infection and at multiple subsequent time points at which T cells specific for known antigens were detectable, including those surrounding the time at which the PD-1 levels were found to be low relative to initial PD-1 levels. Levels of PD-1 on T cells specific for epitopes that either underwent substitutions that impaired T cell recognition or remained constant are shown. Time points at which the substituted epitopes were present are indicated with open circles and points at which the initial viral sequence was present are indicated with closed circles. A. Subject 17 recognized three epitopes: 880TL10 and B35-135 underwent substitution in the first six months of infection and 140G remained intact. PD-1 levels decline three and ten fold following substitution of 880TL10 and B35-135, respectively. T cells recognizing 140G demonstrated a three fold increase in PD-1 expression. B. Subject 13 had one HCV specific T cell response that underwent substitution with an associated drop of nearly three fold in PD-1 expression. C. In Subject 175, HCV levels transiently fell to below the limit of quantitation with a decline in PD-1 levels followed by reemergence of high viral titers and an increase in PD-1 levels on T cells specific for the epitope. D. Subject 30. Sequence escape at epitope C63B is associated with a five-fold decline in PD-1 levels. C63B reverted back to the original sequence in association with a six-fold increase in PD-1 expression on the cognate T cells. A2-61 does not undergo substitution and the level of PD-1 expression varies less than two fold. PD-1 levels are maintained constant or increase over time in the absence of viral sequence variation. (E–H) Levels of PD-1 on T cells specific for epitopes that remained constant are shown for four different HCV infected subjects who recognized at least one T cell epitope for which multimers were available. For all four subjects, PD-1 expression on HCV-specific T cells decreases less than two-fold or increases over time.

Figure 4

Figure 4. PD-1 upregulation requires maintenance of intact antigen and restoration of intact antigen following escape is associated with an increase in PD-1 levels

Viral sequence was assessed at initial infection and at multiple subsequent time points at which T cells specific for known antigens were detectable, including those surrounding the time at which the PD-1 levels were found to be low relative to initial PD-1 levels. Levels of PD-1 on T cells specific for epitopes that either underwent substitutions that impaired T cell recognition or remained constant are shown. Time points at which the substituted epitopes were present are indicated with open circles and points at which the initial viral sequence was present are indicated with closed circles. A. Subject 17 recognized three epitopes: 880TL10 and B35-135 underwent substitution in the first six months of infection and 140G remained intact. PD-1 levels decline three and ten fold following substitution of 880TL10 and B35-135, respectively. T cells recognizing 140G demonstrated a three fold increase in PD-1 expression. B. Subject 13 had one HCV specific T cell response that underwent substitution with an associated drop of nearly three fold in PD-1 expression. C. In Subject 175, HCV levels transiently fell to below the limit of quantitation with a decline in PD-1 levels followed by reemergence of high viral titers and an increase in PD-1 levels on T cells specific for the epitope. D. Subject 30. Sequence escape at epitope C63B is associated with a five-fold decline in PD-1 levels. C63B reverted back to the original sequence in association with a six-fold increase in PD-1 expression on the cognate T cells. A2-61 does not undergo substitution and the level of PD-1 expression varies less than two fold. PD-1 levels are maintained constant or increase over time in the absence of viral sequence variation. (E–H) Levels of PD-1 on T cells specific for epitopes that remained constant are shown for four different HCV infected subjects who recognized at least one T cell epitope for which multimers were available. For all four subjects, PD-1 expression on HCV-specific T cells decreases less than two-fold or increases over time.

Figure 4

Figure 4. PD-1 upregulation requires maintenance of intact antigen and restoration of intact antigen following escape is associated with an increase in PD-1 levels

Viral sequence was assessed at initial infection and at multiple subsequent time points at which T cells specific for known antigens were detectable, including those surrounding the time at which the PD-1 levels were found to be low relative to initial PD-1 levels. Levels of PD-1 on T cells specific for epitopes that either underwent substitutions that impaired T cell recognition or remained constant are shown. Time points at which the substituted epitopes were present are indicated with open circles and points at which the initial viral sequence was present are indicated with closed circles. A. Subject 17 recognized three epitopes: 880TL10 and B35-135 underwent substitution in the first six months of infection and 140G remained intact. PD-1 levels decline three and ten fold following substitution of 880TL10 and B35-135, respectively. T cells recognizing 140G demonstrated a three fold increase in PD-1 expression. B. Subject 13 had one HCV specific T cell response that underwent substitution with an associated drop of nearly three fold in PD-1 expression. C. In Subject 175, HCV levels transiently fell to below the limit of quantitation with a decline in PD-1 levels followed by reemergence of high viral titers and an increase in PD-1 levels on T cells specific for the epitope. D. Subject 30. Sequence escape at epitope C63B is associated with a five-fold decline in PD-1 levels. C63B reverted back to the original sequence in association with a six-fold increase in PD-1 expression on the cognate T cells. A2-61 does not undergo substitution and the level of PD-1 expression varies less than two fold. PD-1 levels are maintained constant or increase over time in the absence of viral sequence variation. (E–H) Levels of PD-1 on T cells specific for epitopes that remained constant are shown for four different HCV infected subjects who recognized at least one T cell epitope for which multimers were available. For all four subjects, PD-1 expression on HCV-specific T cells decreases less than two-fold or increases over time.

Figure 5

Figure 5. Amino acid substitutions in T cell epitopes reduce recognition by cognate T cells, validating them as escape mutations

PBMC were cultivated in the presence of the peptide present at initial infection (closed circle) or at the point where PD-1 levels decreased (open circle) in Subject 17 (A) or Subject 30 (B). After 20 days of stimulation with the peptide present in initial infection (left panels) or the variant peptide (right panels), cells were tested for recognition of both peptides in serial dilutions in an IFN-γ Elispot assay. The number of spot forming colonies (SFC) per 30,000 cells is shown at each peptide dilution. In both cases, the variant peptide was less well recognized than the initial peptide by T cells expanded with the initial peptide (left panels). Stimulation with either of the variant peptides also resulted in reduced recognition of either the initial or variant peptides (right panels) and in reduced expansion of T cells as measured by T cell numbers (data not shown) compared to stimulation with the initial peptide. These substitutions were thus deemed escape mutations.

Similar articles

Cited by

References

    1. Weiss RA, McMichael AJ. Social and environmental risk factors in the emergence of infectious diseases. Nat.Med. 2004;10:S70–S76. - PMC - PubMed
    1. World Health Organization. Hepatitis C: global prevalence. Weekly Epidemiological Record. 1997:341–348. - PubMed
    1. Alter MJ. Epidemiology of hepatitis C in the West. Semin Liver Dis. 1995;15:5–14. - PubMed
    1. Centers for Disease Control and Prevention. Recommendations for prevention and control of hepatitis C virus (HCV) infection and HCV-related chronic disease. MMWR. 1998;47:1–39. (No. RR-19) - PubMed
    1. Villano SA, Vlahov D, Nelson KE, Cohn S, Thomas DL. Persistence of viremia and the importance of long-term follow-up after acute hepatitis C infection. Hepatology. 1999;29:908–914. - PubMed

Publication types

MeSH terms

Substances

Grants and funding

LinkOut - more resources