Interdisciplinary Initiatives Program Round 9 - 2018

Ann Arvin, Pediatrics and Microbiology & Immunology
Wah Chiu, Photon Science, Bioengineering, and Microbiology & Immunology

Varicella-zoster virus (VZV) is an alphaherpesvirus that causes chicken pox and shingles. The hallmark of VZV pathogenesis is cell-to-cell fusion. Importantly, the propensity to elicit cell fusion is linked directly to the health effects of VZV because fusion between ganglion neurons and satellite cells during VZV reactivation is associated with debilitating pain called post-herpetic neuralgia. We have found that VZV glycoprotein B (gB) has a critical role in cell fusion which is regulated via the gB C-terminus. This collaboration brings the disciplines of structural biology and virology together, which must be combined to understand the relationship between the structure of this highly fusogenic viral protein and its functions. This effort has general relevance because all herpesviruses express a gB ortholog essential for virion entry into host cells. In addition, a structure-based analysis of full-length gB in its pre- and post-fusion conformations has the potential to advance knowledge about how other fusogenic viral glycoproteins disrupt the normal intrinsic barriers to cell fusion in differentiated host tissues. To define the structure of native full-length gB, including the membrane proximal, transmembrane and carboxyl terminal domains, which have not been resolved for any herpesvirus gB, we will use an innovative purification strategy to recover gB produced in VZV infected cells and advanced single particle cryogenic electron microscopy (cryo-EM). Defining pre-fusion conformations of gB is considered the ‘holy grail’ in the field. Our collaboration will address this longstanding challenge using novel cryo-EM techniques that will be broadly applicable in protein structure studies. Demonstration of the feasibility to detect alternative gB conformations will support a competitive NIH grant application to pursue gB structure-function studies based on our extensive tools to perform gB mutagenesis in the VZV genome, and evaluate their functional consequences in vitro and in our SCID mouse model of VZV pathogenesis in human xenografts in vivo. Ultimately, new knowledge about gB-dependent cell fusion will inform the design of novel antiviral compounds to reduce the burden of human herpesvirus disease.