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Type I interferon upregulates Bak and contributes to T cell loss during human immunodeficiency virus (HIV) infection.

Fraietta JA, Mueller YM, Yang G, Boesteanu AC, Gracias DT, Do DH, Hope JL, Kathuria N, McGettigan SE, Lewis MG, Giavedoni LD, Jacobson JM, Katsikis PD - PLoS Pathog. (2013)

Bottom Line: We therefore examined the effect of IFNα/β on T cell death and viremia in HIV infection.Apoptosis sensitivity and Bak expression were primarily increased in effector memory T cells.This sensitization by HIV-1 was due to an indirect effect on T cells, as it occurred in peripheral blood mononuclear cell cultures but not purified CD4+ T cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Center for Immunology and Vaccine Science, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America.

ABSTRACT
The role of Type I interferon (IFN) during pathogenic HIV and SIV infections remains unclear, with conflicting observations suggesting protective versus immunopathological effects. We therefore examined the effect of IFNα/β on T cell death and viremia in HIV infection. Ex vivo analysis of eight pro- and anti-apoptotic molecules in chronic HIV-1 infection revealed that pro-apoptotic Bak was increased in CD4+ T cells and correlated directly with sensitivity to CD95/Fas-mediated apoptosis and inversely with CD4+ T cell counts. Apoptosis sensitivity and Bak expression were primarily increased in effector memory T cells. Knockdown of Bak by RNA interference inhibited CD95/Fas-induced death of T cells from HIV-1-infected individuals. In HIV-1-infected patients, IFNα-stimulated gene expression correlated positively with ex vivo T cell Bak levels, CD95/Fas-mediated apoptosis and viremia and negatively with CD4+ T cell counts. In vitro IFNα/β stimulation enhanced Bak expression, CD95/Fas expression and CD95/Fas-mediated apoptosis in healthy donor T cells and induced death of HIV-specific CD8+ T cells from HIV-1-infected patients. HIV-1 in vitro sensitized T cells to CD95/Fas-induced apoptosis and this was Toll-like receptor (TLR)7/9- and Type I IFN-dependent. This sensitization by HIV-1 was due to an indirect effect on T cells, as it occurred in peripheral blood mononuclear cell cultures but not purified CD4+ T cells. Finally, peak IFNα levels and viral loads correlated negatively during acute SIV infection suggesting a potential antiviral effect, but positively during chronic SIV infection indicating that either the virus drives IFNα production or IFNα may facilitate loss of viral control. The above findings indicate stage-specific opposing effects of Type I IFNs during HIV-1 infection and suggest a novel mechanism by which these cytokines contribute to T cell depletion, dysregulation of cellular immunity and disease progression.

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CD95/Fas-induced apoptosis of T cells exposed to HIV-1 is Type I IFN-dependent.(A) TLR7/9 inhibitors inhibit HIV-1Ba-L-induced production of IFNα in infected PBMC from healthy donors. PBMC were exposed to 105 TCID50/ml HIV-1Ba-L in the presence or absence of a TLR7/9 antagonist for 24 hours (n = 13) and IFNα in supernatants was measured by ELISA. Bars indicate mean ± standard error. P values were calculated by using the Wilcoxon signed rank test for paired samples. (B) HIV-1Ba-L exposure increases CD95/Fas apoptosis of T cells, which is inhibited by a TLR7/9 antagonist and anti-IFNα/β receptor blocking antibodies. Sensitivity to CD95/Fas-induced apoptosis shown for CD4+ T cells and CD8+ T cells from healthy donors following a 72 hour exposure to HIV-1Ba-L in the presence or absence of anti-IFNα/β receptor blocking antibodies or a TLR7/9 antagonist (n = 5). Bars depict mean ± standard error. P values were calculated by using the Student's t-test for paired samples. (C) Representative flow cytometry plots from one out of three healthy donors depicting the sensitivity of CD4+ T cells to CD95/Fas-mediated apoptosis following exposure to non-infectious (AT-2 treated) HIV-1Ba-L for 72 hours in the presence or absence of an isotype control antibody, anti-IFNα/β receptor blocking antibody, and a TLR7/9-specific antagonist. Numbers indicate the percentage of apoptosis.
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ppat-1003658-g006: CD95/Fas-induced apoptosis of T cells exposed to HIV-1 is Type I IFN-dependent.(A) TLR7/9 inhibitors inhibit HIV-1Ba-L-induced production of IFNα in infected PBMC from healthy donors. PBMC were exposed to 105 TCID50/ml HIV-1Ba-L in the presence or absence of a TLR7/9 antagonist for 24 hours (n = 13) and IFNα in supernatants was measured by ELISA. Bars indicate mean ± standard error. P values were calculated by using the Wilcoxon signed rank test for paired samples. (B) HIV-1Ba-L exposure increases CD95/Fas apoptosis of T cells, which is inhibited by a TLR7/9 antagonist and anti-IFNα/β receptor blocking antibodies. Sensitivity to CD95/Fas-induced apoptosis shown for CD4+ T cells and CD8+ T cells from healthy donors following a 72 hour exposure to HIV-1Ba-L in the presence or absence of anti-IFNα/β receptor blocking antibodies or a TLR7/9 antagonist (n = 5). Bars depict mean ± standard error. P values were calculated by using the Student's t-test for paired samples. (C) Representative flow cytometry plots from one out of three healthy donors depicting the sensitivity of CD4+ T cells to CD95/Fas-mediated apoptosis following exposure to non-infectious (AT-2 treated) HIV-1Ba-L for 72 hours in the presence or absence of an isotype control antibody, anti-IFNα/β receptor blocking antibody, and a TLR7/9-specific antagonist. Numbers indicate the percentage of apoptosis.

Mentions: Because TLR7 and TLR9 recognition of HIV-1 and SIV in pDC triggers Type I IFN production [9], [34], [35], we next evaluated whether HIV-1 exposure of PBMC from healthy individuals would lead to Type I IFN production and a subsequent increase in T cell apoptosis sensitivity. Although pDC are present at very low frequency in the blood, they produce 100 times more Type I IFN per cell than monocytes [36]. We exposed healthy PBMC to virus in the presence or absence of a TLR7/9-specific antagonist and IFNα/β receptor blocking antibodies and analyzed CD95/Fas-mediated apoptosis. PBMC exposed to 105 TCID50/ml of HIV-1Ba-L for 24 hours secreted IFNα, and this production was significantly reduced in the presence of a phosphorthioate-based TLR7/9 antagonist (Figure 6A). The TLR antagonistic properties of the phosphorothioate deoxyribose compound that was used does not depend on a specific immunoregulatory DNA sequence [37] and can selectively suppress TLR7/9 activation, with no apparent cross-reactivity involving other TLRs [38]. The mechanism of TLR inhibition may be attributed to the ability of the inhibitor to bind TLR7 and TLR9 specifically [38], or its capacity to physically interact with cognate TLR7/9 ligands [37]. This ultimately prevents receptor triggering, MyD88 activation [39] and downstream signaling.


Type I interferon upregulates Bak and contributes to T cell loss during human immunodeficiency virus (HIV) infection.

Fraietta JA, Mueller YM, Yang G, Boesteanu AC, Gracias DT, Do DH, Hope JL, Kathuria N, McGettigan SE, Lewis MG, Giavedoni LD, Jacobson JM, Katsikis PD - PLoS Pathog. (2013)

CD95/Fas-induced apoptosis of T cells exposed to HIV-1 is Type I IFN-dependent.(A) TLR7/9 inhibitors inhibit HIV-1Ba-L-induced production of IFNα in infected PBMC from healthy donors. PBMC were exposed to 105 TCID50/ml HIV-1Ba-L in the presence or absence of a TLR7/9 antagonist for 24 hours (n = 13) and IFNα in supernatants was measured by ELISA. Bars indicate mean ± standard error. P values were calculated by using the Wilcoxon signed rank test for paired samples. (B) HIV-1Ba-L exposure increases CD95/Fas apoptosis of T cells, which is inhibited by a TLR7/9 antagonist and anti-IFNα/β receptor blocking antibodies. Sensitivity to CD95/Fas-induced apoptosis shown for CD4+ T cells and CD8+ T cells from healthy donors following a 72 hour exposure to HIV-1Ba-L in the presence or absence of anti-IFNα/β receptor blocking antibodies or a TLR7/9 antagonist (n = 5). Bars depict mean ± standard error. P values were calculated by using the Student's t-test for paired samples. (C) Representative flow cytometry plots from one out of three healthy donors depicting the sensitivity of CD4+ T cells to CD95/Fas-mediated apoptosis following exposure to non-infectious (AT-2 treated) HIV-1Ba-L for 72 hours in the presence or absence of an isotype control antibody, anti-IFNα/β receptor blocking antibody, and a TLR7/9-specific antagonist. Numbers indicate the percentage of apoptosis.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3795023&req=5

ppat-1003658-g006: CD95/Fas-induced apoptosis of T cells exposed to HIV-1 is Type I IFN-dependent.(A) TLR7/9 inhibitors inhibit HIV-1Ba-L-induced production of IFNα in infected PBMC from healthy donors. PBMC were exposed to 105 TCID50/ml HIV-1Ba-L in the presence or absence of a TLR7/9 antagonist for 24 hours (n = 13) and IFNα in supernatants was measured by ELISA. Bars indicate mean ± standard error. P values were calculated by using the Wilcoxon signed rank test for paired samples. (B) HIV-1Ba-L exposure increases CD95/Fas apoptosis of T cells, which is inhibited by a TLR7/9 antagonist and anti-IFNα/β receptor blocking antibodies. Sensitivity to CD95/Fas-induced apoptosis shown for CD4+ T cells and CD8+ T cells from healthy donors following a 72 hour exposure to HIV-1Ba-L in the presence or absence of anti-IFNα/β receptor blocking antibodies or a TLR7/9 antagonist (n = 5). Bars depict mean ± standard error. P values were calculated by using the Student's t-test for paired samples. (C) Representative flow cytometry plots from one out of three healthy donors depicting the sensitivity of CD4+ T cells to CD95/Fas-mediated apoptosis following exposure to non-infectious (AT-2 treated) HIV-1Ba-L for 72 hours in the presence or absence of an isotype control antibody, anti-IFNα/β receptor blocking antibody, and a TLR7/9-specific antagonist. Numbers indicate the percentage of apoptosis.
Mentions: Because TLR7 and TLR9 recognition of HIV-1 and SIV in pDC triggers Type I IFN production [9], [34], [35], we next evaluated whether HIV-1 exposure of PBMC from healthy individuals would lead to Type I IFN production and a subsequent increase in T cell apoptosis sensitivity. Although pDC are present at very low frequency in the blood, they produce 100 times more Type I IFN per cell than monocytes [36]. We exposed healthy PBMC to virus in the presence or absence of a TLR7/9-specific antagonist and IFNα/β receptor blocking antibodies and analyzed CD95/Fas-mediated apoptosis. PBMC exposed to 105 TCID50/ml of HIV-1Ba-L for 24 hours secreted IFNα, and this production was significantly reduced in the presence of a phosphorthioate-based TLR7/9 antagonist (Figure 6A). The TLR antagonistic properties of the phosphorothioate deoxyribose compound that was used does not depend on a specific immunoregulatory DNA sequence [37] and can selectively suppress TLR7/9 activation, with no apparent cross-reactivity involving other TLRs [38]. The mechanism of TLR inhibition may be attributed to the ability of the inhibitor to bind TLR7 and TLR9 specifically [38], or its capacity to physically interact with cognate TLR7/9 ligands [37]. This ultimately prevents receptor triggering, MyD88 activation [39] and downstream signaling.

Bottom Line: We therefore examined the effect of IFNα/β on T cell death and viremia in HIV infection.Apoptosis sensitivity and Bak expression were primarily increased in effector memory T cells.This sensitization by HIV-1 was due to an indirect effect on T cells, as it occurred in peripheral blood mononuclear cell cultures but not purified CD4+ T cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Center for Immunology and Vaccine Science, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America.

ABSTRACT
The role of Type I interferon (IFN) during pathogenic HIV and SIV infections remains unclear, with conflicting observations suggesting protective versus immunopathological effects. We therefore examined the effect of IFNα/β on T cell death and viremia in HIV infection. Ex vivo analysis of eight pro- and anti-apoptotic molecules in chronic HIV-1 infection revealed that pro-apoptotic Bak was increased in CD4+ T cells and correlated directly with sensitivity to CD95/Fas-mediated apoptosis and inversely with CD4+ T cell counts. Apoptosis sensitivity and Bak expression were primarily increased in effector memory T cells. Knockdown of Bak by RNA interference inhibited CD95/Fas-induced death of T cells from HIV-1-infected individuals. In HIV-1-infected patients, IFNα-stimulated gene expression correlated positively with ex vivo T cell Bak levels, CD95/Fas-mediated apoptosis and viremia and negatively with CD4+ T cell counts. In vitro IFNα/β stimulation enhanced Bak expression, CD95/Fas expression and CD95/Fas-mediated apoptosis in healthy donor T cells and induced death of HIV-specific CD8+ T cells from HIV-1-infected patients. HIV-1 in vitro sensitized T cells to CD95/Fas-induced apoptosis and this was Toll-like receptor (TLR)7/9- and Type I IFN-dependent. This sensitization by HIV-1 was due to an indirect effect on T cells, as it occurred in peripheral blood mononuclear cell cultures but not purified CD4+ T cells. Finally, peak IFNα levels and viral loads correlated negatively during acute SIV infection suggesting a potential antiviral effect, but positively during chronic SIV infection indicating that either the virus drives IFNα production or IFNα may facilitate loss of viral control. The above findings indicate stage-specific opposing effects of Type I IFNs during HIV-1 infection and suggest a novel mechanism by which these cytokines contribute to T cell depletion, dysregulation of cellular immunity and disease progression.

Show MeSH
Related in: MedlinePlus