Bates Laboratory for the study of Host:Viral interactions                                             Perelman School of Medicine at the University of Pennsylvania

 

 

 

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Research


Ebolavirus-host cell interactions


Forward genetic screens in human haploid cells


Analysis of the cell-intrinsic immune factor tetherin


 

Ebolavirus-host cell interactions

Ebolavirus infection is associated with a high mortality rate and the public’s fear of ebolavirus infection makes this virus a bioterror concern. There are no effective treatments for Ebola infection. The ongoing research in my lab addresses three important questions regarding ebolavirus glycoprotein (GP) interactions with the host. First, what are the cellular factors required for ebolavirus entry? Second, how does ebolavirus GP antagonize the function of the cellular antiviral factor Tetherin? Third, does ebolavirus GP employ a novel mechanism of steric occlusion to mediate surface protein down-modulation and what is the effect of GP expression on immune recognition? Answers to these questions will provide important new information about how ebolavirus interacts with the host.  In addition, these studies are likely to suggest new therapeutic or prophylactic strategies to combat ebolavirus infection. Finally, the proposed steric shielding model for surface protein down-regulation by ebolavirus represents a novel mechanism for a viral glycoprotein affecting host cell function and may also be informative for cellular mucin proteins involved in metastatic cancer.

We are taking two approaches to identify host factors needed for ebolavirus infection. First, we selected infection resistant, pseudohaploid Chinese Hamster Ovary (CHO) cells utilizing a recombinant Vesicular Stomatitis Virus encoding ebolavirus GP (VSV-EboGP) and identified four cell lines resistant to GP-mediated viral entry. In four lines examined, we found distinct mutations in the Niemann-Pick Type C1 (NPC1) gene, resulting in loss of protein expression. NPC1 mutations that affected cholesterol regulation were not identified in our screen suggesting a more direct requirement for NPC1 in ebolavirus entry. How NPC1 mediates ebolavirus infection is currently under study. In a second approach, human haploid cells mutagenized by insertional inactivation with a retroviral vector have been screened using VSV-EboGP. The mechanism(s) by which these candidate genes impair viral entry are being explored using cell biological and microscopic methods.

We demonstrated that ebolavirus virions are retained by the cellular restriction factor Tetherin and that ebolavirus glycoprotein (GP) relieves this restriction. We are examining the features and mechanisms by which ebolavirus GP counteracts Tetherin.  Several primate lentiviruses and HIV-2 also utilize their envelope glycoproteins to antagonize Tetherin activity and we are comparing their mechanism(s) to that of Ebolavirus GP.

Ebolavirus glycoprotein expression causes an apparent down modulation of host cell surface proteins leading to loss of cellular adhesion and significantly diminished surface levels of MHC and several other host proteins. The striking down-regulation of class I MHC, and a potential role in loss of cell-cell adhesion leading to hemorrhage, suggest a role for GP in the pathology of ebolavirus infection. Surface protein down modulation is caused by a large mucin-like domain within ebolavirus GP. We recently demonstrated that this region within the ebolavirus glycoprotein acts as a steric shield to block surface accessibility. This model is supported by the published X-ray structure of ebolavirus GP.  Importantly, steric occlusion represents a novel mechanism by which a viral glycoprotein impairs recognition of cellular surface proteins and, as we demonstrated, impairs MHC I-mediated immune cell recognition of GP expressing cells. We are currently investigating whether ebolavirus GP steric occlusion occurs on other cells types and affect innate as well as adaptive immune responses.

 

News & Events

 


01.30.14

Ken finally updates website!!


01.30.14

Press release for MJ & Ken's paper!!


12.18.13

MJ & Ken's paper published in PLoS Pathogens!!


06.07.13

Ben Dyer joins the lab for his thesis work! Did I mention he also received an NSF award?! Go Ben!!


05.31.13

MJ Drake completes her prelim exam!


05.16.13

Alexa Nicolas graduates Penn & completes her thesis work!


05.4.13

Ken Briley presents a poster at the 2013 Viruses & Cells Gordon Conference....in Italia!


09.27.12

Luis Cocka publishes his Tetherin work in PLoS Pathogens!


 


 

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