THE BIOLOGICAL NATURE OF THE VIRUS-CONTAINING COMPARTMENTS IN HIV-1-INFECTED PRIMARY HUMAN MACROPHAGES: THE ROLE OF TETHERIN Open Access

Chu, Hin (2012)

Permanent URL: https://etd.library.emory.edu/concern/etds/7w62f844w?locale=en
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Abstract


THE BIOLOGICAL NATURE OF THE VIRUS-CONTAINING
COMPARTMENTS IN HIV-1-INFECTED PRIMARY HUMAN
MACROPHAGES: THE ROLE OF TETHERIN

Hin Chu

HIV 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. Despite an extensive amount of
investigation, the precise nature and origin of the virus-containing compartments (VCCs)
in infected macrophages has remained controversial. In this dissertation, we carefully
assessed the biological nature of the VCCs in infected MDMs. In addition, we defined the
role of tetherin in MDMs. Our results indicate that tetherin plays an important role in
HIV accumulation and dissemination in infected MDMs.


We investigated the biological nature of the VCCs by examining the accessibility
of the VCCs from the external environment. Our experiments revealed that antibodies,
cationized ferritin, and low molecular weight dextran were excluded from the majority of
VCCs. At the same time, an endosomal-targeting mutant virus was also targeted to the
VCCs where wildtype virus accumulated. These results indicate that the majority of
VCCs in macrophages are not open to the external environment. In parallel, we
demonstrated that tetherin is highly enriched at the site of HIV particle accumulation or
assembly in infected macrophages, and that tetherin acts as a physical tether in this
compartment as it does on the plasma membrane of T cells. Importantly, depletion of tetherin
markedly diminished the size and altered the distribution of the VCCs, suggesting that
tetherin was required for the formation of VCCs.


Taken together, our result support a model in which tetherin plays a critical role in
the accumulation of HIV-1 in infected human macrophages and in transmission from this
cell type to others. Understanding further mechanistic details of the role of tetherin in
HIV retention or release in macrophages, and of the reduced ability of Vpu to counteract
tetherin in macrophages, will be important in efforts to eradicate potential reservoirs of
HIV in infected individuals and in understanding cell-to-cell transmission events in vivo.

Table of Contents



TABLE OF CONTENTS
ACKNOWLEDGEMENTS ······························································································· i
TABLE OF CONTENTS ··································································································· ii
LIST OF FIGURES ············································································································ iii
LIST OF ABBREVIATIONS ···························································································· iv

I. BACKGROUNDS

i. HIV/AIDS
HIV/AIDS disease ······················································································1
HIV/AIDS epidemic ···················································································3
HIV/AIDS treatment ···················································································3
HIV genome ································································································4

ii. HIV-1 Gag and Host Vesicular Trafficking Pathways
Abstract ·······································································································7
Introduction ·································································································8
Gag and late endosome Compartments/ MVBs ········································ 11
Gag and ESCRT ························································································ 16
Plasma membrane-specific interactions: lipid rafts and PI(4,5)P2············ 18
Role of adaptor protein complexes in HIV assembly ······························· 20
GGAs, Arf proteins, and assembly ··························································· 27
Role of Rab GTPase and host motor proteins in HIV assembly ··············· 27
Conclusions ······························································································· 30

iii.The Nature of the HIV-1 Assembly and Budding Compartments in Human
Macrophages
Introduction ······························································································· 33
Current views on the biological nature of the VCCs ································ 34
Discussions
Where does HIV assemble and bud in macrophages? ·················· 43
What is the biological nature of the VCCs in macrophages? ······· 44
What is the destiny of virions in the VCCs of macrophages? ······ 46
Conclusions ······························································································· 47

iv.The Role of Tetherin in HIV-1 Biology
Expression of tetherin ··············································································· 49

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