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Placental Hofbauer cells assemble and sequester HIV-1 in tetraspanin-positive compartments that are accessible to broadly neutralizing antibodies.

Johnson EL, Chu H, Byrareddy SN, Spearman P, Chakraborty R - J Int AIDS Soc (2015)

Bottom Line: Following infection, we observed HIV-1 accumulation in potentially acidic compartments, which stained intensely with Lysotracker-Red.Remarkably, these compartments are readily accessible via the cell surface and can be targeted by exogenously applied small molecules and HIV-1-specific broadly neutralizing antibodies.In addition, broadly neutralizing antibodies (4E10 and VRC01) limited viral replication by HIV-1-infected HCs, which may be mediated by FcγRI.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA.

ABSTRACT

Introduction: Within monocyte-derived macrophages, HIV-1 accumulates in intracellular virus-containing compartments (VCCs) that are inaccessible to the external environment, which implicate these cells as latently infected HIV-1 reservoirs. During mother-to-child transmission of HIV-1, human placental macrophages (Hofbauer cells (HCs)) are viral targets, and have been shown to be infected in vivo and sustain low levels of viral replication in vitro; however, the risk of in utero transmission is less than 7%. The role of these primary macrophages as viral reservoirs is largely undefined. The objective of this study is to define potential sites of viral assembly, accumulation and neutralization in HCs given the pivotal role of the placenta in preventing HIV-1 infection in the mother-infant dyad.

Methods: Term placentae from 20 HIV-1 seronegative women were obtained following caesarian section. VCCs were evaluated by 3D confocal and electron microscopy. Colocalization R values (Pearson's correlation) were quantified with colocalization module of Volocity 5.2.1. Replication kinetics and neutralization studies were evaluated using p24 ELISA.

Results: We demonstrate that primary HCs assemble and sequester HIV-1(BaL) in intracellular VCCs, which are enriched in endosomal/lysosomal markers, including CD9, CD81, CD63 and LAMP-1. Following infection, we observed HIV-1 accumulation in potentially acidic compartments, which stained intensely with Lysotracker-Red. Remarkably, these compartments are readily accessible via the cell surface and can be targeted by exogenously applied small molecules and HIV-1-specific broadly neutralizing antibodies. In addition, broadly neutralizing antibodies (4E10 and VRC01) limited viral replication by HIV-1-infected HCs, which may be mediated by FcγRI.

Conclusions: These findings suggest that placental HCs possess intrinsic adaptations facilitating unique sequestration of HIV-1, and may serve as a protective viral reservoir to permit viral neutralization and/or antiretroviral drug entry in utero.

No MeSH data available.


Related in: MedlinePlus

HCs exhibit a distinct and variable morphology in culture. HCs were maintained in complete medium over six days, with or without HIV-1BaL infection. The morphology of uninfected HCs were analyzed over time and presented as (a) bright field images, and (b) the proportion of each phenotype is displayed. Scale bar in panel a=11 µm. To analyze the subcelluar localization of HIV-1 in HCs, at day 0, along with day 2 and 6 post-infection, cells were fixed, permeabilized and labelled with primary antibodies against HIV-1 Gag (green, anti-CA183) and CD9 (red, anti-CD9) (c). Scale bar in panel c for day 0 and day 2=4.30 µm. Scale bar in panel c for day 6=11 µm. Image acquisition was performed with an Applied Precision Deltavision deconvolution microscope. Sections and bars shown represent a minimum of 30 cells for each condition from 10 donors.
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Figure 0001: HCs exhibit a distinct and variable morphology in culture. HCs were maintained in complete medium over six days, with or without HIV-1BaL infection. The morphology of uninfected HCs were analyzed over time and presented as (a) bright field images, and (b) the proportion of each phenotype is displayed. Scale bar in panel a=11 µm. To analyze the subcelluar localization of HIV-1 in HCs, at day 0, along with day 2 and 6 post-infection, cells were fixed, permeabilized and labelled with primary antibodies against HIV-1 Gag (green, anti-CA183) and CD9 (red, anti-CD9) (c). Scale bar in panel c for day 0 and day 2=4.30 µm. Scale bar in panel c for day 6=11 µm. Image acquisition was performed with an Applied Precision Deltavision deconvolution microscope. Sections and bars shown represent a minimum of 30 cells for each condition from 10 donors.

Mentions: HCs were maintained in complete medium over six days. HCs were noted to be 10–20 µm in size and displayed a pleiomorphic phenotype. In uninfected and HIV-1-infected HCs, their shape changed from round vacuolated cells on day 0 to a partially elongated spindle-like appearance over six days (Figure 1a and 1b), characteristic of HCs within the placental villi [19,20]. These cells can evolve from macrophage-like to a unique fibroblast-like morphology [21].


Placental Hofbauer cells assemble and sequester HIV-1 in tetraspanin-positive compartments that are accessible to broadly neutralizing antibodies.

Johnson EL, Chu H, Byrareddy SN, Spearman P, Chakraborty R - J Int AIDS Soc (2015)

HCs exhibit a distinct and variable morphology in culture. HCs were maintained in complete medium over six days, with or without HIV-1BaL infection. The morphology of uninfected HCs were analyzed over time and presented as (a) bright field images, and (b) the proportion of each phenotype is displayed. Scale bar in panel a=11 µm. To analyze the subcelluar localization of HIV-1 in HCs, at day 0, along with day 2 and 6 post-infection, cells were fixed, permeabilized and labelled with primary antibodies against HIV-1 Gag (green, anti-CA183) and CD9 (red, anti-CD9) (c). Scale bar in panel c for day 0 and day 2=4.30 µm. Scale bar in panel c for day 6=11 µm. Image acquisition was performed with an Applied Precision Deltavision deconvolution microscope. Sections and bars shown represent a minimum of 30 cells for each condition from 10 donors.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4308659&req=5

Figure 0001: HCs exhibit a distinct and variable morphology in culture. HCs were maintained in complete medium over six days, with or without HIV-1BaL infection. The morphology of uninfected HCs were analyzed over time and presented as (a) bright field images, and (b) the proportion of each phenotype is displayed. Scale bar in panel a=11 µm. To analyze the subcelluar localization of HIV-1 in HCs, at day 0, along with day 2 and 6 post-infection, cells were fixed, permeabilized and labelled with primary antibodies against HIV-1 Gag (green, anti-CA183) and CD9 (red, anti-CD9) (c). Scale bar in panel c for day 0 and day 2=4.30 µm. Scale bar in panel c for day 6=11 µm. Image acquisition was performed with an Applied Precision Deltavision deconvolution microscope. Sections and bars shown represent a minimum of 30 cells for each condition from 10 donors.
Mentions: HCs were maintained in complete medium over six days. HCs were noted to be 10–20 µm in size and displayed a pleiomorphic phenotype. In uninfected and HIV-1-infected HCs, their shape changed from round vacuolated cells on day 0 to a partially elongated spindle-like appearance over six days (Figure 1a and 1b), characteristic of HCs within the placental villi [19,20]. These cells can evolve from macrophage-like to a unique fibroblast-like morphology [21].

Bottom Line: Following infection, we observed HIV-1 accumulation in potentially acidic compartments, which stained intensely with Lysotracker-Red.Remarkably, these compartments are readily accessible via the cell surface and can be targeted by exogenously applied small molecules and HIV-1-specific broadly neutralizing antibodies.In addition, broadly neutralizing antibodies (4E10 and VRC01) limited viral replication by HIV-1-infected HCs, which may be mediated by FcγRI.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA.

ABSTRACT

Introduction: Within monocyte-derived macrophages, HIV-1 accumulates in intracellular virus-containing compartments (VCCs) that are inaccessible to the external environment, which implicate these cells as latently infected HIV-1 reservoirs. During mother-to-child transmission of HIV-1, human placental macrophages (Hofbauer cells (HCs)) are viral targets, and have been shown to be infected in vivo and sustain low levels of viral replication in vitro; however, the risk of in utero transmission is less than 7%. The role of these primary macrophages as viral reservoirs is largely undefined. The objective of this study is to define potential sites of viral assembly, accumulation and neutralization in HCs given the pivotal role of the placenta in preventing HIV-1 infection in the mother-infant dyad.

Methods: Term placentae from 20 HIV-1 seronegative women were obtained following caesarian section. VCCs were evaluated by 3D confocal and electron microscopy. Colocalization R values (Pearson's correlation) were quantified with colocalization module of Volocity 5.2.1. Replication kinetics and neutralization studies were evaluated using p24 ELISA.

Results: We demonstrate that primary HCs assemble and sequester HIV-1(BaL) in intracellular VCCs, which are enriched in endosomal/lysosomal markers, including CD9, CD81, CD63 and LAMP-1. Following infection, we observed HIV-1 accumulation in potentially acidic compartments, which stained intensely with Lysotracker-Red. Remarkably, these compartments are readily accessible via the cell surface and can be targeted by exogenously applied small molecules and HIV-1-specific broadly neutralizing antibodies. In addition, broadly neutralizing antibodies (4E10 and VRC01) limited viral replication by HIV-1-infected HCs, which may be mediated by FcγRI.

Conclusions: These findings suggest that placental HCs possess intrinsic adaptations facilitating unique sequestration of HIV-1, and may serve as a protective viral reservoir to permit viral neutralization and/or antiretroviral drug entry in utero.

No MeSH data available.


Related in: MedlinePlus