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Tetherin does not significantly restrict dendritic cell-mediated HIV-1 transmission and its expression is upregulated by newly synthesized HIV-1 Nef.

Coleman CM, Spearman P, Wu L - Retrovirology (2011)

Bottom Line: High levels of tetherin were transiently expressed in LPS- and IFNα-induced mature DCs, while HIV-1 localized into distinct patches in these DCs.Intriguingly, we found that HIV-1 replication in immature DCs induced significant tetherin expression in a Nef-dependent manner.Nef-dependent tetherin induction in HIV-1-infected immature DCs suggests an innate immune response of DCs to HIV-1 infection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Retrovirus Research, Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA.

ABSTRACT

Background: Dendritic cells (DCs) are among the first cells to encounter HIV-1 and play important roles in viral transmission and pathogenesis. Immature DCs allow productive HIV-1 replication and long-term viral dissemination. The pro-inflammatory factor lipopolysaccharide (LPS) induces DC maturation and enhances the efficiency of DC-mediated HIV-1 transmission. Type I interferon (IFN) partially inhibits HIV-1 replication and cell-cell transmission in CD4+ T cells and macrophages. Tetherin is a type I IFN-inducible restriction factor that blocks HIV-1 release and modulates CD4+ T cell-mediated cell-to-cell transmission of HIV-1. However, the role of type I IFN and tetherin in HIV-1 infection of DCs and DC-mediated viral transmission remains unknown.

Results: We demonstrated that IFN-alpha (IFNα)-induced mature DCs restricted HIV-1 replication and trans-infection of CD4+ T cells. Tetherin expression in monocyte-derived immature DCs was undetectable or very low. High levels of tetherin were transiently expressed in LPS- and IFNα-induced mature DCs, while HIV-1 localized into distinct patches in these DCs. Knockdown of induced tetherin in LPS- or IFNα-matured DCs modestly enhanced HIV-1 transmission to CD4+ T cells, but had no significant effect on wild-type HIV-1 replication in mature DCs. Intriguingly, we found that HIV-1 replication in immature DCs induced significant tetherin expression in a Nef-dependent manner.

Conclusions: The restriction of HIV-1 replication and transmission in IFNα-induced mature DCs indicates a potent anti-HIV-1 response; however, high levels of tetherin induced in mature DCs cannot significantly restrict wild-type HIV-1 release and DC-mediated HIV-1 transmission. Nef-dependent tetherin induction in HIV-1-infected immature DCs suggests an innate immune response of DCs to HIV-1 infection.

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Pro-inflammatory stimuli upregulate tetherin expression in DCs. Tetherin expression on iDCs, mDC-LPS and mDC-IFNα from two different donors was assessed by (A) flow cytometry and (B) immunoblotting. (C) TNF-α treatment of DCs modestly upregulates tetherin expression compared with mDC-LPS and mDC-IFNα. Tetherin expression was detected by immunoblotting. (D) HEK293T and HeLa cells were used as negative and positive controls, respectively. Numbers shown in flow cytometry plots are % positive (top) and the geometric mean values of fluorescence intensity (bottom) for each histogram.
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Figure 3: Pro-inflammatory stimuli upregulate tetherin expression in DCs. Tetherin expression on iDCs, mDC-LPS and mDC-IFNα from two different donors was assessed by (A) flow cytometry and (B) immunoblotting. (C) TNF-α treatment of DCs modestly upregulates tetherin expression compared with mDC-LPS and mDC-IFNα. Tetherin expression was detected by immunoblotting. (D) HEK293T and HeLa cells were used as negative and positive controls, respectively. Numbers shown in flow cytometry plots are % positive (top) and the geometric mean values of fluorescence intensity (bottom) for each histogram.

Mentions: The above results indicated that HIV-1 replication and release were restricted in IFNα and LPS-induced mature DCs relative to iDCs, which might be attributed to the induction of HIV-1 restriction factors in mature DCs, such as tetherin. We have reported that pro-inflammatory stimuli (such as LPS) induce DC maturation and modulate the efficiency of DC-mediated HIV-1 transmission [6]. To examine whether pro-inflammatory stimuli upregulate tetherin expression in DCs, DCs from different donors were treated with IFNα and LPS and analyzed for tetherin expression on the surface and in whole cell lysates by flow cytometry and immunoblotting, respectively. Cell surface tetherin in iDCs was low or undetectable (Figure 3A, donor 1 and 2, respectively), which correlated well with the levels of tetherin detected in whole cell lysates (Figure 3B). By contrast, high levels of surface tetherin were detected in mDC-LPS (Figure 3A), which correlated well with high levels of tetherin observed in whole cell lysates (Figure 3B). Although the surface tetherin was low or undetectable in mDC-IFNα, indicating donor variation of tetherin expression in DCs (Figure 3A), high levels of tetherin were detected in whole cell lysates (Figure 3B), suggesting that the tetherin localization in mDC-IFNα is mainly intracellular.


Tetherin does not significantly restrict dendritic cell-mediated HIV-1 transmission and its expression is upregulated by newly synthesized HIV-1 Nef.

Coleman CM, Spearman P, Wu L - Retrovirology (2011)

Pro-inflammatory stimuli upregulate tetherin expression in DCs. Tetherin expression on iDCs, mDC-LPS and mDC-IFNα from two different donors was assessed by (A) flow cytometry and (B) immunoblotting. (C) TNF-α treatment of DCs modestly upregulates tetherin expression compared with mDC-LPS and mDC-IFNα. Tetherin expression was detected by immunoblotting. (D) HEK293T and HeLa cells were used as negative and positive controls, respectively. Numbers shown in flow cytometry plots are % positive (top) and the geometric mean values of fluorescence intensity (bottom) for each histogram.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108291&req=5

Figure 3: Pro-inflammatory stimuli upregulate tetherin expression in DCs. Tetherin expression on iDCs, mDC-LPS and mDC-IFNα from two different donors was assessed by (A) flow cytometry and (B) immunoblotting. (C) TNF-α treatment of DCs modestly upregulates tetherin expression compared with mDC-LPS and mDC-IFNα. Tetherin expression was detected by immunoblotting. (D) HEK293T and HeLa cells were used as negative and positive controls, respectively. Numbers shown in flow cytometry plots are % positive (top) and the geometric mean values of fluorescence intensity (bottom) for each histogram.
Mentions: The above results indicated that HIV-1 replication and release were restricted in IFNα and LPS-induced mature DCs relative to iDCs, which might be attributed to the induction of HIV-1 restriction factors in mature DCs, such as tetherin. We have reported that pro-inflammatory stimuli (such as LPS) induce DC maturation and modulate the efficiency of DC-mediated HIV-1 transmission [6]. To examine whether pro-inflammatory stimuli upregulate tetherin expression in DCs, DCs from different donors were treated with IFNα and LPS and analyzed for tetherin expression on the surface and in whole cell lysates by flow cytometry and immunoblotting, respectively. Cell surface tetherin in iDCs was low or undetectable (Figure 3A, donor 1 and 2, respectively), which correlated well with the levels of tetherin detected in whole cell lysates (Figure 3B). By contrast, high levels of surface tetherin were detected in mDC-LPS (Figure 3A), which correlated well with high levels of tetherin observed in whole cell lysates (Figure 3B). Although the surface tetherin was low or undetectable in mDC-IFNα, indicating donor variation of tetherin expression in DCs (Figure 3A), high levels of tetherin were detected in whole cell lysates (Figure 3B), suggesting that the tetherin localization in mDC-IFNα is mainly intracellular.

Bottom Line: High levels of tetherin were transiently expressed in LPS- and IFNα-induced mature DCs, while HIV-1 localized into distinct patches in these DCs.Intriguingly, we found that HIV-1 replication in immature DCs induced significant tetherin expression in a Nef-dependent manner.Nef-dependent tetherin induction in HIV-1-infected immature DCs suggests an innate immune response of DCs to HIV-1 infection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Retrovirus Research, Department of Veterinary Biosciences, The Ohio State University, Columbus, OH 43210, USA.

ABSTRACT

Background: Dendritic cells (DCs) are among the first cells to encounter HIV-1 and play important roles in viral transmission and pathogenesis. Immature DCs allow productive HIV-1 replication and long-term viral dissemination. The pro-inflammatory factor lipopolysaccharide (LPS) induces DC maturation and enhances the efficiency of DC-mediated HIV-1 transmission. Type I interferon (IFN) partially inhibits HIV-1 replication and cell-cell transmission in CD4+ T cells and macrophages. Tetherin is a type I IFN-inducible restriction factor that blocks HIV-1 release and modulates CD4+ T cell-mediated cell-to-cell transmission of HIV-1. However, the role of type I IFN and tetherin in HIV-1 infection of DCs and DC-mediated viral transmission remains unknown.

Results: We demonstrated that IFN-alpha (IFNα)-induced mature DCs restricted HIV-1 replication and trans-infection of CD4+ T cells. Tetherin expression in monocyte-derived immature DCs was undetectable or very low. High levels of tetherin were transiently expressed in LPS- and IFNα-induced mature DCs, while HIV-1 localized into distinct patches in these DCs. Knockdown of induced tetherin in LPS- or IFNα-matured DCs modestly enhanced HIV-1 transmission to CD4+ T cells, but had no significant effect on wild-type HIV-1 replication in mature DCs. Intriguingly, we found that HIV-1 replication in immature DCs induced significant tetherin expression in a Nef-dependent manner.

Conclusions: The restriction of HIV-1 replication and transmission in IFNα-induced mature DCs indicates a potent anti-HIV-1 response; however, high levels of tetherin induced in mature DCs cannot significantly restrict wild-type HIV-1 release and DC-mediated HIV-1 transmission. Nef-dependent tetherin induction in HIV-1-infected immature DCs suggests an innate immune response of DCs to HIV-1 infection.

Show MeSH
Related in: MedlinePlus