The Intracellular Virus-Containing Compartments in Primary Human Macrophages Are Largely Inaccessible to Antibodies and Small Molecules

• Type of Material: Article
• Authors: Hin Chu, Emory University and Children’s Healthcare of Atlanta; Jaang-Jiun Wang, Emory University; Mingli Qi, Emory University and Children’s Healthcare of Atlanta; Jeong-Joong Yoon, Emory University and Children’s Healthcare of Atlanta; Xiaoyun Wen, Emory University and Children’s Healthcare of Atlanta; Xuemin Chen, Emory University; Lingmei Ding, Emory University and Children’s Healthcare of Atlanta; Paul Spearman, Emory University
• Language: English
• Date: 2012-05-02
• Publisher: Public Library of Science
• Publication Version: Final Published Version
• Copyright Statement: © 2012 Chu et al.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0035297
• Title of Journal or Parent Work: PLoS ONE
• ISSN: 1932-6203
• Volume: 7
• Issue: 5
• Start Page: e35297
• End Page: e35297
• Grant/Funding Information: This work was supported by National Institutes of Health (NIH) AI058828 and NIH AI40338 and by funds from Children’s Healthcare of Atlanta.; The work was partly supported by the flow cytometry/cell sorting core of Children’s Healthcare of Atlanta, by the Emory Center for AIDS Research (P30 AI050409), and by the Robert P. Apkarian Integrated Electron Microscopy Core Laboratory of Emory University.
• Research Categories: Health Sciences, Public Health

Abstract

HIV-1 assembly and release occurs at the plasma membrane of human T lymphocytes and model epithelial cell lines, whereas in macrophages intracellular sites of virus assembly or accumulation predominate. The origin of the intracellular virus-containing compartment (VCC) has been controversial. This compartment is enriched in markers of the multivesicular body, and has been described as a modified endosomal compartment. Several studies of this compartment have revealed the presence of small channels connecting to the plasma membrane, suggesting that instead of an endosomal origin the compartment is a modified plasma membrane compartment. If the compartment is accessible to the external environment, this would have important implications for antiviral immune responses and antiviral therapy. We performed a series of experiments designed to determine if the VCC in macrophages was open to the external environment and accessible to antibodies and small molecules. The majority of VCCs were found to be inaccessible to exogenously-applied antibodies to tetraspanins in the absence of membrane permeabilization, while tetraspanin staining was readily observed following membrane permeabilization. Cationized ferritin was utilized to stain the plasma membrane, and revealed that the majority of virus-containing compartments were inaccessible to ferritin. Low molecular weight dextrans could access only a very small percentage of VCCs, and these tended to be more peripheral compartments. We conclude that the VCCs in monocyte-derived human macrophages are heterogeneous, but the majority of VCCs are closed to the external environment.