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Antigen load and viral sequence diversification determine the functional profile of HIV-1-specific CD8+ T cells.

Streeck H, Brumme ZL, Anastario M, Cohen KW, Jolin JS, Meier A, Brumme CJ, Rosenberg ES, Alter G, Allen TM, Walker BD, Altfeld M - PLoS Med. (2008)

Bottom Line: Virus-specific CD8(+) T lymphocytes play a key role in the initial reduction of peak viremia during acute viral infections, but display signs of increasing dysfunction and exhaustion under conditions of chronic antigen persistence.This exhausted phenotype significantly decreased upon removal of stimulation by antigen, either in response to antiretroviral therapy or by reduction of epitope-specific antigen load in the presence of ongoing viral replication, as a consequence of in vivo selection of cytotoxic T lymphocyte escape mutations in the respective epitopes.Monofunctionality increased in CD8(+) T cell responses directed against conserved epitopes from 49% (95% confidence interval 27%-72%) to 76% (56%-95%) (standard deviation [SD] of the effect size 0.71), while monofunctionality remained stable or slightly decreased for responses directed against escaped epitopes from 61% (47%-75%) to 56% (42%-70%) (SD of the effect size 0.18) (p < 0.05).

View Article: PubMed Central - PubMed

Affiliation: Partners AIDS Research Center, Infectious Disease Unit, Massachusetts General Hospital and Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America.

ABSTRACT

Background: Virus-specific CD8(+) T lymphocytes play a key role in the initial reduction of peak viremia during acute viral infections, but display signs of increasing dysfunction and exhaustion under conditions of chronic antigen persistence. It has been suggested that virus-specific CD8(+) T cells with a "polyfunctional" profile, defined by the capacity to secrete multiple cytokines or chemokines, are most competent in controlling viral replication in chronic HIV-1 infection. We used HIV-1 infection as a model of chronic persistent viral infection to investigate the process of exhaustion and dysfunction of virus-specific CD8(+) T cell responses on the single-epitope level over time, starting in primary HIV-1 infection.

Methods and findings: We longitudinally analyzed the polyfunctional epitope-specific CD8(+) T cell responses of 18 patients during primary HIV-1 infection before and after therapy initiation or sequence variation in the targeted epitope. Epitope-specific CD8(+) T cells responded with multiple effector functions to antigenic stimulation during primary HIV-1 infection, but lost their polyfunctional capacity in response to antigen and up-regulated programmed death 1 (PD-1) expression with persistent viremic infection. This exhausted phenotype significantly decreased upon removal of stimulation by antigen, either in response to antiretroviral therapy or by reduction of epitope-specific antigen load in the presence of ongoing viral replication, as a consequence of in vivo selection of cytotoxic T lymphocyte escape mutations in the respective epitopes. Monofunctionality increased in CD8(+) T cell responses directed against conserved epitopes from 49% (95% confidence interval 27%-72%) to 76% (56%-95%) (standard deviation [SD] of the effect size 0.71), while monofunctionality remained stable or slightly decreased for responses directed against escaped epitopes from 61% (47%-75%) to 56% (42%-70%) (SD of the effect size 0.18) (p < 0.05).

Conclusion: These data suggest that persistence of antigen can be the cause, rather than the consequence, of the functional impairment of virus-specific T cell responses observed during chronic HIV-1 infection, and underscore the importance of evaluating autologous viral sequences in studies aimed at investigating the relationship between virus-specific immunity and associated pathogenesis.

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Reduction in PD-1 Expression on Epitope-Specific CD8+ T Cells after Sequence Evolution in the Respective EpitopesPrimary flow data (for the HLA-A3-restricted epitope A3-RK9 in p17 Gag [left]) and combined data for five individuals (right) for PD-1 expression on epitope-specific CD8+ T cells before (“WT–early”) and after (“variant–late”) the selection of amino acid substitutions within the targeted epitopes are shown. PD-1 is expressed as MFI on tetramer-positive CD8+ T cells. In the graph on the left, data from the early time point are shown by the black tracing, while data for the late time point are shown by grey shading. A fluorescent minus one control is shown in comparison for both stainings. In the graph on the right, grey lines represent changes within patients between time periods (“WT,” early; “variant,” late); the black line represents the median PD-1 expression change on all five studied tetramer-positive CD8+ T cell populations between time periods. The decrease of the PD-1 expression on tetramer-positive CD8+ T cells before and after the development of sequence variations within epitopes was statistically significant (p = 0.006; paired t-test).
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pmed-0050100-g005: Reduction in PD-1 Expression on Epitope-Specific CD8+ T Cells after Sequence Evolution in the Respective EpitopesPrimary flow data (for the HLA-A3-restricted epitope A3-RK9 in p17 Gag [left]) and combined data for five individuals (right) for PD-1 expression on epitope-specific CD8+ T cells before (“WT–early”) and after (“variant–late”) the selection of amino acid substitutions within the targeted epitopes are shown. PD-1 is expressed as MFI on tetramer-positive CD8+ T cells. In the graph on the left, data from the early time point are shown by the black tracing, while data for the late time point are shown by grey shading. A fluorescent minus one control is shown in comparison for both stainings. In the graph on the right, grey lines represent changes within patients between time periods (“WT,” early; “variant,” late); the black line represents the median PD-1 expression change on all five studied tetramer-positive CD8+ T cell populations between time periods. The decrease of the PD-1 expression on tetramer-positive CD8+ T cells before and after the development of sequence variations within epitopes was statistically significant (p = 0.006; paired t-test).

Mentions: Recently it has been shown that PD-1 expression on CD8+ T cells is closely correlated with the functional exhaustion of CD8+ T cells in HIV-1–infected patients, and might serve as a correlate of protective immunity [19,20,39]. Therefore, we hypothesized that reduction in the functional avidity of the interaction between CD8+ T cells with their respective epitope resulting from amino acid substitutions will also affect the expression of PD-1 on those cells, indicating weaker activation of these epitope-specific CD8+ T cells. Sufficient specimens were available to longitudinally investigate CD8+ T cell responses directed against five epitopes by tetramer staining, which contained at the first time point the wild-type viral sequence but showed variation in the viral sequence at the second time point that resulted in reduced recognition of the epitope. CD8+ T cell responses directed against seven epitopes in the same patients that remained conserved were used as controls. While the MFI (± standard deviation [SD]) of PD-1 on epitope-specific tetramer-positive CD8+ T cells increased for the seven conserved epitopes over time (210 ± 156 to 309 ± 334; see Figure S3), PD-1 expression significantly decreased on the five epitope-specific CD8+ T cells that developed a sequence variation in the targeted epitope (399 ± 123 to 248 ± 103, p = 0.006 paired t-test) (Figure 5), but was still higher than the PD-1 negative control. In contrast, the expression of CD127 on epitope-specific cells was very low, as described previously [22,40] and not significantly impacted by viral escape (unpublished data). The reduction of PD-1 expression levels following escape further support our previous results, which indicate a general improvement of epitope-specific CD8+ T cell functionality and quality upon reduction of the specific antigen (epitope) level that is independent of the overall level of viral replication.


Antigen load and viral sequence diversification determine the functional profile of HIV-1-specific CD8+ T cells.

Streeck H, Brumme ZL, Anastario M, Cohen KW, Jolin JS, Meier A, Brumme CJ, Rosenberg ES, Alter G, Allen TM, Walker BD, Altfeld M - PLoS Med. (2008)

Reduction in PD-1 Expression on Epitope-Specific CD8+ T Cells after Sequence Evolution in the Respective EpitopesPrimary flow data (for the HLA-A3-restricted epitope A3-RK9 in p17 Gag [left]) and combined data for five individuals (right) for PD-1 expression on epitope-specific CD8+ T cells before (“WT–early”) and after (“variant–late”) the selection of amino acid substitutions within the targeted epitopes are shown. PD-1 is expressed as MFI on tetramer-positive CD8+ T cells. In the graph on the left, data from the early time point are shown by the black tracing, while data for the late time point are shown by grey shading. A fluorescent minus one control is shown in comparison for both stainings. In the graph on the right, grey lines represent changes within patients between time periods (“WT,” early; “variant,” late); the black line represents the median PD-1 expression change on all five studied tetramer-positive CD8+ T cell populations between time periods. The decrease of the PD-1 expression on tetramer-positive CD8+ T cells before and after the development of sequence variations within epitopes was statistically significant (p = 0.006; paired t-test).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2365971&req=5

pmed-0050100-g005: Reduction in PD-1 Expression on Epitope-Specific CD8+ T Cells after Sequence Evolution in the Respective EpitopesPrimary flow data (for the HLA-A3-restricted epitope A3-RK9 in p17 Gag [left]) and combined data for five individuals (right) for PD-1 expression on epitope-specific CD8+ T cells before (“WT–early”) and after (“variant–late”) the selection of amino acid substitutions within the targeted epitopes are shown. PD-1 is expressed as MFI on tetramer-positive CD8+ T cells. In the graph on the left, data from the early time point are shown by the black tracing, while data for the late time point are shown by grey shading. A fluorescent minus one control is shown in comparison for both stainings. In the graph on the right, grey lines represent changes within patients between time periods (“WT,” early; “variant,” late); the black line represents the median PD-1 expression change on all five studied tetramer-positive CD8+ T cell populations between time periods. The decrease of the PD-1 expression on tetramer-positive CD8+ T cells before and after the development of sequence variations within epitopes was statistically significant (p = 0.006; paired t-test).
Mentions: Recently it has been shown that PD-1 expression on CD8+ T cells is closely correlated with the functional exhaustion of CD8+ T cells in HIV-1–infected patients, and might serve as a correlate of protective immunity [19,20,39]. Therefore, we hypothesized that reduction in the functional avidity of the interaction between CD8+ T cells with their respective epitope resulting from amino acid substitutions will also affect the expression of PD-1 on those cells, indicating weaker activation of these epitope-specific CD8+ T cells. Sufficient specimens were available to longitudinally investigate CD8+ T cell responses directed against five epitopes by tetramer staining, which contained at the first time point the wild-type viral sequence but showed variation in the viral sequence at the second time point that resulted in reduced recognition of the epitope. CD8+ T cell responses directed against seven epitopes in the same patients that remained conserved were used as controls. While the MFI (± standard deviation [SD]) of PD-1 on epitope-specific tetramer-positive CD8+ T cells increased for the seven conserved epitopes over time (210 ± 156 to 309 ± 334; see Figure S3), PD-1 expression significantly decreased on the five epitope-specific CD8+ T cells that developed a sequence variation in the targeted epitope (399 ± 123 to 248 ± 103, p = 0.006 paired t-test) (Figure 5), but was still higher than the PD-1 negative control. In contrast, the expression of CD127 on epitope-specific cells was very low, as described previously [22,40] and not significantly impacted by viral escape (unpublished data). The reduction of PD-1 expression levels following escape further support our previous results, which indicate a general improvement of epitope-specific CD8+ T cell functionality and quality upon reduction of the specific antigen (epitope) level that is independent of the overall level of viral replication.

Bottom Line: Virus-specific CD8(+) T lymphocytes play a key role in the initial reduction of peak viremia during acute viral infections, but display signs of increasing dysfunction and exhaustion under conditions of chronic antigen persistence.This exhausted phenotype significantly decreased upon removal of stimulation by antigen, either in response to antiretroviral therapy or by reduction of epitope-specific antigen load in the presence of ongoing viral replication, as a consequence of in vivo selection of cytotoxic T lymphocyte escape mutations in the respective epitopes.Monofunctionality increased in CD8(+) T cell responses directed against conserved epitopes from 49% (95% confidence interval 27%-72%) to 76% (56%-95%) (standard deviation [SD] of the effect size 0.71), while monofunctionality remained stable or slightly decreased for responses directed against escaped epitopes from 61% (47%-75%) to 56% (42%-70%) (SD of the effect size 0.18) (p < 0.05).

View Article: PubMed Central - PubMed

Affiliation: Partners AIDS Research Center, Infectious Disease Unit, Massachusetts General Hospital and Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America.

ABSTRACT

Background: Virus-specific CD8(+) T lymphocytes play a key role in the initial reduction of peak viremia during acute viral infections, but display signs of increasing dysfunction and exhaustion under conditions of chronic antigen persistence. It has been suggested that virus-specific CD8(+) T cells with a "polyfunctional" profile, defined by the capacity to secrete multiple cytokines or chemokines, are most competent in controlling viral replication in chronic HIV-1 infection. We used HIV-1 infection as a model of chronic persistent viral infection to investigate the process of exhaustion and dysfunction of virus-specific CD8(+) T cell responses on the single-epitope level over time, starting in primary HIV-1 infection.

Methods and findings: We longitudinally analyzed the polyfunctional epitope-specific CD8(+) T cell responses of 18 patients during primary HIV-1 infection before and after therapy initiation or sequence variation in the targeted epitope. Epitope-specific CD8(+) T cells responded with multiple effector functions to antigenic stimulation during primary HIV-1 infection, but lost their polyfunctional capacity in response to antigen and up-regulated programmed death 1 (PD-1) expression with persistent viremic infection. This exhausted phenotype significantly decreased upon removal of stimulation by antigen, either in response to antiretroviral therapy or by reduction of epitope-specific antigen load in the presence of ongoing viral replication, as a consequence of in vivo selection of cytotoxic T lymphocyte escape mutations in the respective epitopes. Monofunctionality increased in CD8(+) T cell responses directed against conserved epitopes from 49% (95% confidence interval 27%-72%) to 76% (56%-95%) (standard deviation [SD] of the effect size 0.71), while monofunctionality remained stable or slightly decreased for responses directed against escaped epitopes from 61% (47%-75%) to 56% (42%-70%) (SD of the effect size 0.18) (p < 0.05).

Conclusion: These data suggest that persistence of antigen can be the cause, rather than the consequence, of the functional impairment of virus-specific T cell responses observed during chronic HIV-1 infection, and underscore the importance of evaluating autologous viral sequences in studies aimed at investigating the relationship between virus-specific immunity and associated pathogenesis.

Show MeSH
Related in: MedlinePlus