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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

Low-molecular-weight dextrans can access the VCCs in HIV-1-infected HCs. HIV-1-infected HCs were incubated with Texas Red Dextran, 3000 MW, at 4°C or 37°C for 30 minutes. Cells were then fixed and stained for Gag (green). (a) Representative images of cells incubated at 4°C. (b) Representative image of cells incubated at 37°C. Scale bar=11 µm. Sections shown represent a minimum of 30 cells for each condition from 10 donors.
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Figure 0004: Low-molecular-weight dextrans can access the VCCs in HIV-1-infected HCs. HIV-1-infected HCs were incubated with Texas Red Dextran, 3000 MW, at 4°C or 37°C for 30 minutes. Cells were then fixed and stained for Gag (green). (a) Representative images of cells incubated at 4°C. (b) Representative image of cells incubated at 37°C. Scale bar=11 µm. Sections shown represent a minimum of 30 cells for each condition from 10 donors.

Mentions: We examined the ability of fluorescent low-molecular-weight dextran to access the VCC in unfixed HCs. HIV-1-infected HCs were incubated at 4°C or 37°C with Texas Red Dextran (Dex-TR, 3000 MW) prior to fixation, permeabilization and staining as before. Staining at 4°C to reduces membrane movement and phagocytosis, while labelling at 37°C allows for active uptake. HCs incubated at 4°C and 37°C demonstrated strong colocalization of dextran and Gag in intracellular compartments (Figure 4a and 4b). These results indicate that the majority of VCCs are accessible to the external environment.


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)

Low-molecular-weight dextrans can access the VCCs in HIV-1-infected HCs. HIV-1-infected HCs were incubated with Texas Red Dextran, 3000 MW, at 4°C or 37°C for 30 minutes. Cells were then fixed and stained for Gag (green). (a) Representative images of cells incubated at 4°C. (b) Representative image of cells incubated at 37°C. Scale bar=11 µm. Sections 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 0004: Low-molecular-weight dextrans can access the VCCs in HIV-1-infected HCs. HIV-1-infected HCs were incubated with Texas Red Dextran, 3000 MW, at 4°C or 37°C for 30 minutes. Cells were then fixed and stained for Gag (green). (a) Representative images of cells incubated at 4°C. (b) Representative image of cells incubated at 37°C. Scale bar=11 µm. Sections shown represent a minimum of 30 cells for each condition from 10 donors.
Mentions: We examined the ability of fluorescent low-molecular-weight dextran to access the VCC in unfixed HCs. HIV-1-infected HCs were incubated at 4°C or 37°C with Texas Red Dextran (Dex-TR, 3000 MW) prior to fixation, permeabilization and staining as before. Staining at 4°C to reduces membrane movement and phagocytosis, while labelling at 37°C allows for active uptake. HCs incubated at 4°C and 37°C demonstrated strong colocalization of dextran and Gag in intracellular compartments (Figure 4a and 4b). These results indicate that the majority of VCCs are accessible to the external environment.

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