Limits...
Efficient BST2 antagonism by Vpu is critical for early HIV-1 dissemination in humanized mice.

Dave VP, Hajjar F, Dieng MM, Haddad É, Cohen ÉA - Retrovirology (2013)

Bottom Line: Interestingly, we also find that efficient HIV-1 release and dissemination are directly related to functional strength of Vpu in antagonizing BST2.Thus, reduced antagonism of BST2 due to β-TrCP binding domain mutations results in decreased plasma viremia and frequency of infected T cells, highlighting the importance of Vpu-mediated β-TrCP-dependent BST-2 degradation for optimal initial viral propagation.Overall, our findings suggest that BST2 antagonism by Vpu is critical for efficient early viral expansion and dissemination during acute infection and as such is likely to confer HIV-1 increased transmission fitness.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Human Retrovirology, Institut de Recherches Cliniques de Montréal (IRCM), 110 Pine avenue west, Montreal, QC H2W 1R7, Canada. eric.cohen@ircm.qc.ca.

ABSTRACT

Background: Vpu is a multifunctional accessory protein that enhances the release of HIV-1 by counteracting the entrapment of nascent virions on infected cell surface mediated by BST2/Tetherin. Vpu-mediated BST2 antagonism involves physical association with BST2 and subsequent mislocalization of the restriction factor to intracellular compartments followed by SCF(β-TrCP) E3 ligase-dependent lysosomal degradation. Apart from BST2 antagonism, Vpu also induces down regulation of several immune molecules, including CD4 and SLAMF6/NTB-A, to evade host immune responses and promote viral dissemination. However, it should be noted that the multiple functions of Vpu have been studied in cell-based assays, and thus it remains unclear how Vpu influences the dynamic of HIV-1 infection in in vivo conditions.

Results: Using a humanized mouse model of acute infection as well as CCR5-tropic HIV-1 that lack Vpu or encode WT Vpu or Vpu with mutations in the β-TrCP binding domain, we provide evidence that Vpu-mediated BST2 antagonism plays a crucial role in establishing early plasma viremia and viral dissemination. Interestingly, we also find that efficient HIV-1 release and dissemination are directly related to functional strength of Vpu in antagonizing BST2. Thus, reduced antagonism of BST2 due to β-TrCP binding domain mutations results in decreased plasma viremia and frequency of infected T cells, highlighting the importance of Vpu-mediated β-TrCP-dependent BST-2 degradation for optimal initial viral propagation.

Conclusions: Overall, our findings suggest that BST2 antagonism by Vpu is critical for efficient early viral expansion and dissemination during acute infection and as such is likely to confer HIV-1 increased transmission fitness.

Show MeSH

Related in: MedlinePlus

Effect of Vpu mutated in the β-TrCP-binding domain on the dynamics of HIV infection in hu-mice. Hu-mice were infected with high dose of HIV-1-WT, HIV-1-∆Vpu, or HIV-1-VpuD52/56 and plasma viral load was determined at different time points. (A) shows kinetics of RNA copy number per ml of plasma (log10) and (B) shows absolute values at 21-dpi in plasma of hu-mice infected with the indicated HIV-1. Please note that x-axis crosses at log10 value of 3.0. (C) shows comparison of the frequency of p24+ T cells in spleen of hu-mice infected with the indicated HIV-1 (n ≥ 7) at 21-dpi. (D) shows type I IFN levels at 21-dpi in plasma of hu-mice infected with the indicated HIV-1. (E) shows impact of Vpu mutations on BST2 and CD4 levels on p24+ and p24- T cells from individual hu-mouse infected with the indicated strain of HIV-1. (F) shows comparison of relative BST2 and CD4 levels on p24+ (closed bar) and p24- (open bar) T cells from spleen of hu-mice infected with the indicated strain of HIV-1 at 21-dpi (n ≥ 4). BST2 and CD4 MFIs on p24-negative uninfected cells were treated as 100%. Error bars represent SD; *, p ≤ 0.05; **, p ≤ 0.005, ***, p ≤ 0.0005, N.S.: non significant.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4226203&req=5

Figure 5: Effect of Vpu mutated in the β-TrCP-binding domain on the dynamics of HIV infection in hu-mice. Hu-mice were infected with high dose of HIV-1-WT, HIV-1-∆Vpu, or HIV-1-VpuD52/56 and plasma viral load was determined at different time points. (A) shows kinetics of RNA copy number per ml of plasma (log10) and (B) shows absolute values at 21-dpi in plasma of hu-mice infected with the indicated HIV-1. Please note that x-axis crosses at log10 value of 3.0. (C) shows comparison of the frequency of p24+ T cells in spleen of hu-mice infected with the indicated HIV-1 (n ≥ 7) at 21-dpi. (D) shows type I IFN levels at 21-dpi in plasma of hu-mice infected with the indicated HIV-1. (E) shows impact of Vpu mutations on BST2 and CD4 levels on p24+ and p24- T cells from individual hu-mouse infected with the indicated strain of HIV-1. (F) shows comparison of relative BST2 and CD4 levels on p24+ (closed bar) and p24- (open bar) T cells from spleen of hu-mice infected with the indicated strain of HIV-1 at 21-dpi (n ≥ 4). BST2 and CD4 MFIs on p24-negative uninfected cells were treated as 100%. Error bars represent SD; *, p ≤ 0.05; **, p ≤ 0.005, ***, p ≤ 0.0005, N.S.: non significant.

Mentions: To assess the effect of abrogating Vpu binding to β-TrCP on BST2 antagonism and early HIV-1 propagation, we infected hu-mice with high dose (~500,000 TCID50) of HIV-1-WT, HIV-1-∆Vpu, or HIV-1-VpuD52/56. Infected mice were bled at 3, 7, 14, and 21-dpi. As described above, infection of hu-mice with high dose of HIV-1-WT but not HIV-1-∆Vpu resulted in high plasma viremia; at 21-dpi HIV-1-WT infected animals showed ~15-fold higher plasma viremia compared to HIV-1-∆Vpu infected animals (Figure 5A-B). Interestingly, despite its strongly attenuated BST2 antagonism phenotype in cell culture assays, HIV-1-VpuD52/56 displayed a plasma viremia that was intermediate between that in WT and ∆Vpu HIV infected hu-mice; at 21-dpi, ~three-fold less HIV-1 viral particles (absolute values) were detected in plasma of hu-mice infected with HIV-1-VpuD52/56 compared to HIV-1-WT infected hu-mice (Figure 5B).


Efficient BST2 antagonism by Vpu is critical for early HIV-1 dissemination in humanized mice.

Dave VP, Hajjar F, Dieng MM, Haddad É, Cohen ÉA - Retrovirology (2013)

Effect of Vpu mutated in the β-TrCP-binding domain on the dynamics of HIV infection in hu-mice. Hu-mice were infected with high dose of HIV-1-WT, HIV-1-∆Vpu, or HIV-1-VpuD52/56 and plasma viral load was determined at different time points. (A) shows kinetics of RNA copy number per ml of plasma (log10) and (B) shows absolute values at 21-dpi in plasma of hu-mice infected with the indicated HIV-1. Please note that x-axis crosses at log10 value of 3.0. (C) shows comparison of the frequency of p24+ T cells in spleen of hu-mice infected with the indicated HIV-1 (n ≥ 7) at 21-dpi. (D) shows type I IFN levels at 21-dpi in plasma of hu-mice infected with the indicated HIV-1. (E) shows impact of Vpu mutations on BST2 and CD4 levels on p24+ and p24- T cells from individual hu-mouse infected with the indicated strain of HIV-1. (F) shows comparison of relative BST2 and CD4 levels on p24+ (closed bar) and p24- (open bar) T cells from spleen of hu-mice infected with the indicated strain of HIV-1 at 21-dpi (n ≥ 4). BST2 and CD4 MFIs on p24-negative uninfected cells were treated as 100%. Error bars represent SD; *, p ≤ 0.05; **, p ≤ 0.005, ***, p ≤ 0.0005, N.S.: non significant.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4226203&req=5

Figure 5: Effect of Vpu mutated in the β-TrCP-binding domain on the dynamics of HIV infection in hu-mice. Hu-mice were infected with high dose of HIV-1-WT, HIV-1-∆Vpu, or HIV-1-VpuD52/56 and plasma viral load was determined at different time points. (A) shows kinetics of RNA copy number per ml of plasma (log10) and (B) shows absolute values at 21-dpi in plasma of hu-mice infected with the indicated HIV-1. Please note that x-axis crosses at log10 value of 3.0. (C) shows comparison of the frequency of p24+ T cells in spleen of hu-mice infected with the indicated HIV-1 (n ≥ 7) at 21-dpi. (D) shows type I IFN levels at 21-dpi in plasma of hu-mice infected with the indicated HIV-1. (E) shows impact of Vpu mutations on BST2 and CD4 levels on p24+ and p24- T cells from individual hu-mouse infected with the indicated strain of HIV-1. (F) shows comparison of relative BST2 and CD4 levels on p24+ (closed bar) and p24- (open bar) T cells from spleen of hu-mice infected with the indicated strain of HIV-1 at 21-dpi (n ≥ 4). BST2 and CD4 MFIs on p24-negative uninfected cells were treated as 100%. Error bars represent SD; *, p ≤ 0.05; **, p ≤ 0.005, ***, p ≤ 0.0005, N.S.: non significant.
Mentions: To assess the effect of abrogating Vpu binding to β-TrCP on BST2 antagonism and early HIV-1 propagation, we infected hu-mice with high dose (~500,000 TCID50) of HIV-1-WT, HIV-1-∆Vpu, or HIV-1-VpuD52/56. Infected mice were bled at 3, 7, 14, and 21-dpi. As described above, infection of hu-mice with high dose of HIV-1-WT but not HIV-1-∆Vpu resulted in high plasma viremia; at 21-dpi HIV-1-WT infected animals showed ~15-fold higher plasma viremia compared to HIV-1-∆Vpu infected animals (Figure 5A-B). Interestingly, despite its strongly attenuated BST2 antagonism phenotype in cell culture assays, HIV-1-VpuD52/56 displayed a plasma viremia that was intermediate between that in WT and ∆Vpu HIV infected hu-mice; at 21-dpi, ~three-fold less HIV-1 viral particles (absolute values) were detected in plasma of hu-mice infected with HIV-1-VpuD52/56 compared to HIV-1-WT infected hu-mice (Figure 5B).

Bottom Line: Interestingly, we also find that efficient HIV-1 release and dissemination are directly related to functional strength of Vpu in antagonizing BST2.Thus, reduced antagonism of BST2 due to β-TrCP binding domain mutations results in decreased plasma viremia and frequency of infected T cells, highlighting the importance of Vpu-mediated β-TrCP-dependent BST-2 degradation for optimal initial viral propagation.Overall, our findings suggest that BST2 antagonism by Vpu is critical for efficient early viral expansion and dissemination during acute infection and as such is likely to confer HIV-1 increased transmission fitness.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Human Retrovirology, Institut de Recherches Cliniques de Montréal (IRCM), 110 Pine avenue west, Montreal, QC H2W 1R7, Canada. eric.cohen@ircm.qc.ca.

ABSTRACT

Background: Vpu is a multifunctional accessory protein that enhances the release of HIV-1 by counteracting the entrapment of nascent virions on infected cell surface mediated by BST2/Tetherin. Vpu-mediated BST2 antagonism involves physical association with BST2 and subsequent mislocalization of the restriction factor to intracellular compartments followed by SCF(β-TrCP) E3 ligase-dependent lysosomal degradation. Apart from BST2 antagonism, Vpu also induces down regulation of several immune molecules, including CD4 and SLAMF6/NTB-A, to evade host immune responses and promote viral dissemination. However, it should be noted that the multiple functions of Vpu have been studied in cell-based assays, and thus it remains unclear how Vpu influences the dynamic of HIV-1 infection in in vivo conditions.

Results: Using a humanized mouse model of acute infection as well as CCR5-tropic HIV-1 that lack Vpu or encode WT Vpu or Vpu with mutations in the β-TrCP binding domain, we provide evidence that Vpu-mediated BST2 antagonism plays a crucial role in establishing early plasma viremia and viral dissemination. Interestingly, we also find that efficient HIV-1 release and dissemination are directly related to functional strength of Vpu in antagonizing BST2. Thus, reduced antagonism of BST2 due to β-TrCP binding domain mutations results in decreased plasma viremia and frequency of infected T cells, highlighting the importance of Vpu-mediated β-TrCP-dependent BST-2 degradation for optimal initial viral propagation.

Conclusions: Overall, our findings suggest that BST2 antagonism by Vpu is critical for efficient early viral expansion and dissemination during acute infection and as such is likely to confer HIV-1 increased transmission fitness.

Show MeSH
Related in: MedlinePlus