Structural and functional characterization of the chemokine enhancing activity ofvaricella zoster virus (VZV) glycoprotein C

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Varicella zoster virus (VZV) is a highly prevalent human pathogen that establishes latency in peripheral neurons. VZV causes varicella during primary infection and zoster following reactivation. Zoster is characterized by acute pain and may be followed by post herpetic neuralgia (PHN), the second most common type of neuropathic pain worldwide. Despite the existence of licensed vaccines, VZV associated pain still represents a major health problem that causes an important economic burden. Moreover, VZV can also cause pathologies associated with high mortality and morbidity such as encephalitis and vasculitis when infecting the central nervous system.During natural infection VZV productively infects leukocytes and this infection event is essential for VZV spread throughout the host to the skin and neurons and also for subsequent pathogenesis. Leukocyte migration to the site of infection is orchestrated by chemokines and several viruses express viral chemokine binding proteins (vCKBP) to modulate chemokine activity. We have recently shown that VZV glycoprotein C (gC) is a vCKBP that enhances chemokine activity resulting in increased leukocyte migration - a phenotype that likely contributes to VZV spread, in contrast to the majority of vCKBP that inhibit leukocyte migration. Crystal structures have been reported for inhibitory vCKBP in complex with chemokines, but no such structural information is available for enhancing vCKBP. Finally, chemokines and viral proteins that interact with the chemokine/chemokine receptor pair induce pain. Therefore, in view of its chemokine-enhancing activity it is plausible to assume that gC plays an important role in VZV associated pain.The goal of this project is to further investigate the role of VZV gC in viral pathogenesis and in particular in the development of VZV associated pain. For this purpose, we will employ a combination of protein biochemistry and cell biology approaches. We will first set out to crystallize the minimal functionally-active soluble gC ectodomain alone and in complex with a chemokine and determine its X-ray structure(s). As glycoproteins are often difficult to crystallize and antibody fragments often facilitate crystallization in such difficult cases (i.e., they serve as "crystallization chaperones"), we will generate an antibody library targeting gC. In parallel, we will determine the mechanistic role of gC by analyzing its impact on chemokine receptor usage, clustering and signalling. Eventually, we will investigate the role of gC in the development of chemokine-mediated pain using an animal model and α-gC antibodies targeting the gC-chemokine interaction as specific control. Our results will contribute to understanding of the differences between inhibitory and enhancing vCKBP, to determine the role of gC in VZV pathogenesis and pave the way for novel therapeutic approaches to inhibit VZV spread and to combat VZV associated pain.