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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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HIV-1 replication in iDCs upregulates tetherin in a Nef-dependent manner. (A) Cell lysates from iDCs infected with WT NL(AD8), NL(AD8)ΔNef with (+) or without (-) AZT or mock infected were evaluated at 5 dpi for the expression of HIV-1 Gag (p55 and p24), tetherin and GAPDH by immunoblotting. (B) Flow cytometry analysis of surface tetherin expression in infected DCs at 5 dpi. M, Mock infection; WT, wild-type NL(AD8); ΔNef, NL(AD8)ΔNef. One representative experiment out of three is shown.
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Figure 8: HIV-1 replication in iDCs upregulates tetherin in a Nef-dependent manner. (A) Cell lysates from iDCs infected with WT NL(AD8), NL(AD8)ΔNef with (+) or without (-) AZT or mock infected were evaluated at 5 dpi for the expression of HIV-1 Gag (p55 and p24), tetherin and GAPDH by immunoblotting. (B) Flow cytometry analysis of surface tetherin expression in infected DCs at 5 dpi. M, Mock infection; WT, wild-type NL(AD8); ΔNef, NL(AD8)ΔNef. One representative experiment out of three is shown.

Mentions: A previous study suggested that the upregulation of tetherin surface expression by HIV-1 infection in macrophages appears to be Nef-dependent [59]. To investigate whether tetherin induction by HIV-1 in DCs was dependent on Nef synthesized during viral infection, iDCs were separately infected with WT NL(AD8) and Nef-deleted mutant (ΔNef) in the presence or absence of AZT. The expression of tetherin and HIV-1 Gag in DCs was assessed by immunoblotting at 5 dpi, which represented the peak of HIV-1 replication in iDCs (Figure 2D). WT HIV-1 infection of iDCs induced tetherin expression at 5 dpi, which could be abolished by AZT treatment (Figure 8A). The ΔNef HIV-1 mutant failed to induce tetherin, despite similar Gag production relative to WT HIV-1 infection (Figure 8A). Furthermore, flow cytometry analysis of tetherin expression in infected DCs confirmed that WT HIV-1 but not ΔNef mutant induced tetherin surface expression (Figure 8B). Thus, HIV-1 replication in iDCs induces transient upregulation of tetherin expression due to the production of Nef.


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)

HIV-1 replication in iDCs upregulates tetherin in a Nef-dependent manner. (A) Cell lysates from iDCs infected with WT NL(AD8), NL(AD8)ΔNef with (+) or without (-) AZT or mock infected were evaluated at 5 dpi for the expression of HIV-1 Gag (p55 and p24), tetherin and GAPDH by immunoblotting. (B) Flow cytometry analysis of surface tetherin expression in infected DCs at 5 dpi. M, Mock infection; WT, wild-type NL(AD8); ΔNef, NL(AD8)ΔNef. One representative experiment out of three is shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: HIV-1 replication in iDCs upregulates tetherin in a Nef-dependent manner. (A) Cell lysates from iDCs infected with WT NL(AD8), NL(AD8)ΔNef with (+) or without (-) AZT or mock infected were evaluated at 5 dpi for the expression of HIV-1 Gag (p55 and p24), tetherin and GAPDH by immunoblotting. (B) Flow cytometry analysis of surface tetherin expression in infected DCs at 5 dpi. M, Mock infection; WT, wild-type NL(AD8); ΔNef, NL(AD8)ΔNef. One representative experiment out of three is shown.
Mentions: A previous study suggested that the upregulation of tetherin surface expression by HIV-1 infection in macrophages appears to be Nef-dependent [59]. To investigate whether tetherin induction by HIV-1 in DCs was dependent on Nef synthesized during viral infection, iDCs were separately infected with WT NL(AD8) and Nef-deleted mutant (ΔNef) in the presence or absence of AZT. The expression of tetherin and HIV-1 Gag in DCs was assessed by immunoblotting at 5 dpi, which represented the peak of HIV-1 replication in iDCs (Figure 2D). WT HIV-1 infection of iDCs induced tetherin expression at 5 dpi, which could be abolished by AZT treatment (Figure 8A). The ΔNef HIV-1 mutant failed to induce tetherin, despite similar Gag production relative to WT HIV-1 infection (Figure 8A). Furthermore, flow cytometry analysis of tetherin expression in infected DCs confirmed that WT HIV-1 but not ΔNef mutant induced tetherin surface expression (Figure 8B). Thus, HIV-1 replication in iDCs induces transient upregulation of tetherin expression due to the production of Nef.

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