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Type I interferon responses are impaired in latently HIV infected cells

View Article: PubMed Central - PubMed

ABSTRACT

Background: The latent HIV-1 reservoir represents the primary barrier to the eradication of HIV-1 infection. The design of novel reservoir-clearance strategies, however, is impeded in part by the inability to distinguish latently HIV-infected cells from uninfected cells. Significant impairment of the type I interferon (IFN-I) response is observed during productive HIV-1 infection. Although this remains poorly described in the context of latent HIV-1 infection, presence of potential defects may serve as a novel therapeutic target. Therefore, IFN-I pathways were characterized using two latently HIV-1-infected cell lines, U1 and OM10.1, in comparison to their respective uninfected parental U937 and HL60 cell lines.

Findings: Constitutive expression and induction of important mediators of IFN-I signaling including IFNα/β cytokines, IFNAR1, MHC-I, ISG15, and PKR were evaluated following exogenous IFNα or poly(I:C) treatment. Differences in basal expression of IFNAR1, MHC-I, and PKR were observed between the latently HIV-1 infected and uninfected cell lines. In parallel, significant impairments in the induction of MHC-I, ISG15 and PKR, as well as secretion of IFNα/β cytokines were observed in response to appropriate exogenous stimulation within the two latently HIV-infected U1 and OM10.1 cells, relative to their HIV-uninfected parental cells.

Conclusions: In comparison to the HIV-uninfected U937 and HL60 cell lines, widespread defects in IFN-I responsiveness were observed within the latently HIV-infected U1 and OM10.1 cells. These impairments represent novel therapeutic targets, which may be amenable to strategies currently employed in cancer therapy.

Electronic supplementary material: The online version of this article (doi:10.1186/s12977-016-0302-9) contains supplementary material, which is available to authorized users.

No MeSH data available.


IFNα-induced expression of MHC-I is impaired in latently HIV-infected U1 and OM10.1 cells. Cell lines were stimulated with 10, 100, or 1000 U/mL of exogenous IFNα for 24 h. Following stimulation, cells were collected and surface expression of MHC-I was assessed by flow cytometry. Representative histogram and summary data of IFNα-induced MHC-I expression normalized to unstimulated controls is shown for a U937 and U1 cells (n = 6) and b HL60 and OM10.1 cells (n = 6). †p < 0.0001 by one-way ANOVA and p < 0.05 by pairwise Dunnett’s test compared to unstimulated cells. *p < 0.05; **p < 0.01, and ***p < 0.001 by Two-way ANOVA with Bonferroni post-test for multiple comparisons
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Fig2: IFNα-induced expression of MHC-I is impaired in latently HIV-infected U1 and OM10.1 cells. Cell lines were stimulated with 10, 100, or 1000 U/mL of exogenous IFNα for 24 h. Following stimulation, cells were collected and surface expression of MHC-I was assessed by flow cytometry. Representative histogram and summary data of IFNα-induced MHC-I expression normalized to unstimulated controls is shown for a U937 and U1 cells (n = 6) and b HL60 and OM10.1 cells (n = 6). †p < 0.0001 by one-way ANOVA and p < 0.05 by pairwise Dunnett’s test compared to unstimulated cells. *p < 0.05; **p < 0.01, and ***p < 0.001 by Two-way ANOVA with Bonferroni post-test for multiple comparisons

Mentions: Next, the responsiveness of latently HIV-infected cells to exogenous IFNα was investigated by characterizing the expression of downstream ISGs. MHC-I expression was upregulated in response to IFNα in all cell lines, but was significantly lower in the latently HIV-infected U1 (Fig. 2a) and OM10.1 cells (Fig. 2b) when compared to their respective controls. Similarly, IFNα enhanced the expression of ISG15 in a dose-dependent manner in all cell lines, but the level of ISG15 expression was lower in the latently HIV-infected U1 (Fig. 3a) and OM10.1 cells (Fig. 3b) than in the HIV-uninfected controls. Although no difference in the expression of ISG15 mRNA was observed between U937 and U1 cells following IFNα treatment, a significantly lower level of ISG15 expression was observed in OM10.1 cells relative to HL60 cells (Additional file 2A). Finally, IFNα-induced PKR expression was found to be impaired in OM10.1 cells relative to HL60 cells (Fig. 4b), but did not differ between U1 and U937 cells (Fig. 4a). Consistent with this, lower levels of IFNα-induced PKR gene expression were observed in OM10.1 cells than in HL60 cells, but no difference was observed between U1 and U937 cells (Additional file 2B).Fig. 2


Type I interferon responses are impaired in latently HIV infected cells
IFNα-induced expression of MHC-I is impaired in latently HIV-infected U1 and OM10.1 cells. Cell lines were stimulated with 10, 100, or 1000 U/mL of exogenous IFNα for 24 h. Following stimulation, cells were collected and surface expression of MHC-I was assessed by flow cytometry. Representative histogram and summary data of IFNα-induced MHC-I expression normalized to unstimulated controls is shown for a U937 and U1 cells (n = 6) and b HL60 and OM10.1 cells (n = 6). †p < 0.0001 by one-way ANOVA and p < 0.05 by pairwise Dunnett’s test compared to unstimulated cells. *p < 0.05; **p < 0.01, and ***p < 0.001 by Two-way ANOVA with Bonferroni post-test for multiple comparisons
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5017046&req=5

Fig2: IFNα-induced expression of MHC-I is impaired in latently HIV-infected U1 and OM10.1 cells. Cell lines were stimulated with 10, 100, or 1000 U/mL of exogenous IFNα for 24 h. Following stimulation, cells were collected and surface expression of MHC-I was assessed by flow cytometry. Representative histogram and summary data of IFNα-induced MHC-I expression normalized to unstimulated controls is shown for a U937 and U1 cells (n = 6) and b HL60 and OM10.1 cells (n = 6). †p < 0.0001 by one-way ANOVA and p < 0.05 by pairwise Dunnett’s test compared to unstimulated cells. *p < 0.05; **p < 0.01, and ***p < 0.001 by Two-way ANOVA with Bonferroni post-test for multiple comparisons
Mentions: Next, the responsiveness of latently HIV-infected cells to exogenous IFNα was investigated by characterizing the expression of downstream ISGs. MHC-I expression was upregulated in response to IFNα in all cell lines, but was significantly lower in the latently HIV-infected U1 (Fig. 2a) and OM10.1 cells (Fig. 2b) when compared to their respective controls. Similarly, IFNα enhanced the expression of ISG15 in a dose-dependent manner in all cell lines, but the level of ISG15 expression was lower in the latently HIV-infected U1 (Fig. 3a) and OM10.1 cells (Fig. 3b) than in the HIV-uninfected controls. Although no difference in the expression of ISG15 mRNA was observed between U937 and U1 cells following IFNα treatment, a significantly lower level of ISG15 expression was observed in OM10.1 cells relative to HL60 cells (Additional file 2A). Finally, IFNα-induced PKR expression was found to be impaired in OM10.1 cells relative to HL60 cells (Fig. 4b), but did not differ between U1 and U937 cells (Fig. 4a). Consistent with this, lower levels of IFNα-induced PKR gene expression were observed in OM10.1 cells than in HL60 cells, but no difference was observed between U1 and U937 cells (Additional file 2B).Fig. 2

View Article: PubMed Central - PubMed

ABSTRACT

Background: The latent HIV-1 reservoir represents the primary barrier to the eradication of HIV-1 infection. The design of novel reservoir-clearance strategies, however, is impeded in part by the inability to distinguish latently HIV-infected cells from uninfected cells. Significant impairment of the type I interferon (IFN-I) response is observed during productive HIV-1 infection. Although this remains poorly described in the context of latent HIV-1 infection, presence of potential defects may serve as a novel therapeutic target. Therefore, IFN-I pathways were characterized using two latently HIV-1-infected cell lines, U1 and OM10.1, in comparison to their respective uninfected parental U937 and HL60 cell lines.

Findings: Constitutive expression and induction of important mediators of IFN-I signaling including IFN&alpha;/&beta; cytokines, IFNAR1, MHC-I, ISG15, and PKR were evaluated following exogenous IFN&alpha; or poly(I:C) treatment. Differences in basal expression of IFNAR1, MHC-I, and PKR were observed between the latently HIV-1 infected and uninfected cell lines. In parallel, significant impairments in the induction of MHC-I, ISG15 and PKR, as well as secretion of IFN&alpha;/&beta; cytokines were observed in response to appropriate exogenous stimulation within the two latently HIV-infected U1 and OM10.1 cells, relative to their HIV-uninfected parental cells.

Conclusions: In comparison to the HIV-uninfected U937 and HL60 cell lines, widespread defects in IFN-I responsiveness were observed within the latently HIV-infected U1 and OM10.1 cells. These impairments represent novel therapeutic targets, which may be amenable to strategies currently employed in cancer therapy.

Electronic supplementary material: The online version of this article (doi:10.1186/s12977-016-0302-9) contains supplementary material, which is available to authorized users.

No MeSH data available.