The role of Vpu and tetherin in HIV/AIDS pathogenesis

Lead Research Organisation: King's College London
Department Name: Immunology Infection and Inflam Diseases

Abstract

Human Immunodeficiency Virus type 1 (HIV-1) is the cause of the worldwide AIDS epidemic. In the absence of an effective vaccine, understanding the mechanisms by which the virus replicates has provided several targets for the design of potent antiviral drugs. HIV-1 encodes a number of accessory genes whose function is to subvert host defence systems that have evolved to combat viral infections. We have shown that one such accessory protein, Vpu, is required by the virus to overcome the action of a human protein known as tetherin or CD317. Tetherin levels in cells are activated by viral infection. HIV-1 viruses that lack a Vpu gene are blocked in their replication because tetherin prevents new virus particles leaving the cell, thereby inhibiting the spread of the virus. However, the importance of Vpu and tetherin in the pathogenesis of HIV-1 disease in infected individuals has not been studied.
This grant proposal aims to study the role of Vpu and tetherin in patients by using samples stored in the King?s College Infectious Disease BioBank. We will isolate Vpu genes from the blood of HIV positive individuals with different rates of disease progression and examine their ability to counteract tetherin, to see if variation in Vpu function is associated with clinical outcomes. We will also examine the regulation of tetherin expression in various primary cells that HIV-1 targets, and if genetic variations in and around the tetherin gene can affect these expression levels. Finally, we will use functional Vpu variants isolated from patients as tools to identify cellular proteins required for its ability to overcome tetherin. These studies will achieve the following objectives: (1) To determine whether Vpu and tetherin functions affect the susceptibility of patients to faster rates of disease progression; (2) Identification of mutant Vpu genes that encode non-functional proteins will allow us understand the basis for its anti-tetherin function; (3) Finally, determining an in vivo role of Vpu and tetherin in HIV/AIDS pathogenesis will provide compelling rationale to develop strategies to target Vpu function for new antiviral drug design.

Technical Summary

Human Immunodeficiency Virus type 1 (HIV-1), the aetiological agent of pandemic AIDS, encodes a number of accessory genes whose protein products allow the virus to avoid effectors of the innate and adaptive immune response. Understanding the importance of these factors in vivo will highlight whether these accessory proteins will be viable targets for novel antiretroviral therapeutics. The Vpu protein of HIV-1 has recently been shown to overcome the actions of an interferon-induced membrane protein tetherin (CD317) that can be expressed on many HIV-1 primary target cells. In the absence of Vpu, HIV-1 replication is potently inhibited in tetherin expressing cells because new viral particles fail to be released from the plasma membrane. The purpose of this grant is to examine Vpu and tetherin function in HIV-1-infected patients. Using patient material stored in the KCL Infectious Disease BioBank, we will clone Vpu alleles from HIV-1 positive patients defined as rapid progressors and long-term non-progressors/controllers, as well as longitudinal samples from patients from acute to chronic HIV infection. We will assess the function of these Vpu alleles for their ability to antagonize tetherin in vitro, identify the molecular determinants that confer functional variation in Vpu, and assess whether variation in Vpu is associated with any HIV-1 pathogenic outcomes. We will also determine tetherin expression levels on primary HIV-1 target cells, the regulation of these expression levels by proinflammatory stimuli, and the effects of single-nucleotide polymorphisms in the tetherin promoter on its transcriptional regulation. In addition, we will develop methods to isolate tetherin and Vpu interacting factors from host cells in an effort to identify cellular proteins required for their respective functions. These studies will provide in vivo evidence of the importance of Vpu/tetherin interactions in HIV-1 pathogenesis, their suitability as markers for clinical HIV-1 patient management, and rationale for the design of drugs to disrupt Vpu function.

Publications

10 25 50
 
Description ERC starter grant
Amount € 1,500,000 (EUR)
Organisation European Research Council (ERC) 
Sector Public
Country Belgium
Start 12/2011 
End 11/2016
 
Description Senior Research Fellowship
Amount £1,350,000 (GBP)
Funding ID WT098049MA 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2013 
End 12/2017
 
Title Functional Vpu mutants 
Description We have made a panel of mutants in the the Vpu transmembrane domain that have defects in tetherin-binding and antagonism. 
Type Of Material Technology assay or reagent 
Year Produced 2010 
Provided To Others? Yes  
Impact Publication: Vigan and Neil, J Virol 
 
Description Tetherin, IFITM and ADCC 
Organisation University of Montreal
Department Department Of Microbiology And Immunology
Country Canada 
Sector Academic/University 
PI Contribution Provision of reagents and expertise to assess the role of tetherin in the sentization of HIV-1 infected cells to antibody dependent cytotoxicity
Collaborator Contribution Use of said reagents, and supply of HIV-1 envelope constructs for IFITM studies in our lab.
Impact Foster et al, 2016 Cell Host and Microbe Richard et al, 2017 J Virol (in press)
Start Year 2015
 
Description Use of the MACS HIV cohort to study Vpu functional variation 
Organisation Northwestern University
Department Department of Microbiology-Immunology
Country United States 
Sector Academic/University 
PI Contribution We have used this collaboration to access the MACS cohort and sequence Vpu alleles from patients with different pathogenic HIV outcomes.
Collaborator Contribution Access to the largest bank of stored samples of HIV+ individuals in the US
Impact A library of Vpu sequences from HIV infected patients that we are now functionally evaluating
Start Year 2009
 
Description Vpu and Vpr, stress and sensing 
Organisation University College London
Country United Kingdom 
Sector Academic/University 
PI Contribution Joint investigations into the role of Vpu and Vpr and antagonising cellular stress and pattern recognition responses
Collaborator Contribution as above
Impact Publications in preparation
Start Year 2016
 
Description Vpu targets 
Organisation University of Cambridge
Department Department of Zoology
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaboration with Paul Lehner to identify novel Vpu targets. we produce constructs and infected cell samples for LC/MS, and partner in the characterisation of the hits.
Collaborator Contribution They perform the LC/MS and partner in the characterisation of the hits
Impact Identification of SNAT1 as a Vpu target (Matheson et al, 2015)
Start Year 2010
 
Description Channel 5 interview 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Interview on Channel 5 about the Zika outbreak in Brazil
Year(s) Of Engagement Activity 2016
 
Description Interview for Newsnight 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact interviews about COVID19 response
Year(s) Of Engagement Activity 2020
 
Description NASMR 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Undergraduate students
Results and Impact Webcast for NASMR to highlight research intercalated BSc at KCL in immunobiology
Year(s) Of Engagement Activity 2016
 
Description Walworth Academy teaching of 6th formers 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Invited to speak to 6th formers at Walworth Academy, Bermondsey about why we haven't cured HIV yet
Year(s) Of Engagement Activity 2018