PhD Student, La Trobe University
Characterising and utilising the immuno-modulatory capabilities of Viperin
Viperin is a unique and highly evolutionarily conserved protein that is able to restrict many diverse viruses. As a prominent member of our early innate immune system, viperin utilises multiple mechanisms to fight off viral invaders. Of these mechanisms, many involve the protein’s direct interaction and inhibition of viruses such as Hepatitis C Virus (HCV) and Human Immunodeficiency Virus (HIV), but more recently have involved an indirect mode of viral inhibition.
My research focuses on these indirect mechanisms of viperin’s restriction of viruses. For the first time I have been able to show that viperin achieves its inhibition of a collection of viruses by interacting with key immune molecules. Acting a sort of scaffold, viperin pulls together these key immune molecules to aid their signalling activation which leads to an enhanced transduction of the immune signal. In doing this viperin has been shown to increase the production of the potent anti-viral cytokine, interferon beta, and upregulate other anti-viral proteins. Not only does this action help us to eliminate viruses that have already infiltrated our cells, but it also primes neighbouring uninfected cells to more effectively fight off viruses.
The next stage of my research will involve delivering recombinant viperin protein into an infection model to determine its use as an alternative anti-viral therapeutic agent against a wide range of viruses. The need for such alternative anti-viral treatments has never been greater with the high prevalence of emergent viral diseases, such as Zika, Ebola and Swine Flu to which we have no treatment. Viperin’s potential application as a potent anti-viral treatment offers promise as an effective pan-viral treatment that does not have the high costs or long development time associated with typical vaccine development. In addition to this, due to its action on the patient and not the virus, this therapeutic approach is less susceptible to the generation of viral resistance. My research highlights the necessity of better understanding the intricate and complex actions of our immune system to develop better treatments against viral diseases.
Abstract: Zika virus (ZIKV) infection has emerged as a global health threat and infection of pregnant women causes intrauterine growth restriction, spontaneous abortion and microcephaly in newborns. Here we show using biologically relevant cells of neural and placental origin that following ZIKV infection, there is attenuation of the cellular innate response characterised by reduced expression of IFN-β and associated interferon stimulated genes (ISGs). One such ISG is viperin that has well documented antiviral activity against a wide range of viruses. Expression of viperin in cultured cells resulted in significant impairment of ZIKV replication, while MEFs derived from CRISPR/Cas9 derived viperin(-/-) mice replicated ZIKV to higher titers compared to their WT counterparts. These results suggest that ZIKV can attenuate ISG expression to avoid the cellular antiviral innate response, thus allowing the virus to replicate unchecked. Moreover, we have identified that the ISG viperin has significant anti-ZIKV activity. Further understanding of how ZIKV perturbs the ISG response and the molecular mechanisms utilised by viperin to suppress ZIKV replication will aid in our understanding of ZIKV biology, pathogenesis and possible design of novel antiviral strategies.
Pub.: 02 Jul '17, Pinned: 31 Jul '17
Abstract: Macrophages are key target cells for HIV-1. HIV-1(BaL) induced a subset of interferon-stimulated genes in monocyte-derived macrophages (MDMs), which differed from that in monocyte-derived dendritic cells and CD4 T cells, without inducing any interferons. Inhibition of type I interferon induction was mediated by HIV-1 inhibition of interferon-regulated factor (IRF3) nuclear translocation. In MDMs, viperin was the most up-regulated interferon-stimulated genes, and it significantly inhibited HIV-1 production. HIV-1 infection disrupted lipid rafts via viperin induction and redistributed viperin to CD81 compartments, the site of HIV-1 egress by budding in MDMs. Exogenous farnesol, which enhances membrane protein prenylation, reversed viperin-mediated inhibition of HIV-1 production. Mutagenesis analysis in transfected cell lines showed that the internal S-adenosyl methionine domains of viperin were essential for its antiviral activity. Thus viperin may contribute to persistent noncytopathic HIV-1 infection of macrophages and possibly to biologic differences with HIV-1-infected T cells.
Pub.: 09 Jun '12, Pinned: 31 Jul '17
Abstract: The host protein viperin is an interferon stimulated gene (ISG) that is up-regulated during a number of viral infections. In this study we have shown that dengue virus type-2 (DENV-2) infection significantly induced viperin, co-incident with production of viral RNA and via a mechanism requiring retinoic acid-inducible gene I (RIG-I). Viperin did not inhibit DENV-2 entry but DENV-2 RNA and infectious virus release was inhibited in viperin expressing cells. Conversely, DENV-2 replicated to higher tires earlier in viperin shRNA expressing cells. The anti-DENV effect of viperin was mediated by residues within the C-terminal 17 amino acids of viperin and did not require the N-terminal residues, including the helix domain, leucine zipper and S-adenosylmethionine (SAM) motifs known to be involved in viperin intracellular membrane association. Viperin showed co-localisation with lipid droplet markers, and was co-localised and interacted with DENV-2 capsid (CA), NS3 and viral RNA. The ability of viperin to interact with DENV-2 NS3 was associated with its anti-viral activity, while co-localisation of viperin with lipid droplets was not. Thus, DENV-2 infection induces viperin which has anti-viral properties residing in the C-terminal region of the protein that act to restrict early DENV-2 RNA production/accumulation, potentially via interaction of viperin with DENV-2 NS3 and replication complexes. These anti-DENV-2 actions of viperin show both contrasts and similarities with other described anti-viral mechanisms of viperin action and highlight the diverse nature of this unique anti-viral host protein.
Pub.: 03 May '13, Pinned: 31 Jul '17
Abstract: Viral infection of the cell is able to initiate a signaling cascade of events that ultimately attempts to limit viral replication and prevent escalating infection through expression of host antiviral proteins. Recent work has highlighted the importance of the host antiviral protein viperin in this process, with its ability to limit a large variety of viral infections as well as play a role in the production of type I interferon and the modulation of a number of transcription factor binding sites. Viperin appears to have the ability to modulate varying conditions within the cell and to interfere with proviral host proteins in its attempts to create an unfavorable environment for viral replication. The study of the mechanistic actions of viperin has come a long way in recent years, describing important functional domains of the protein for its antiviral and immune modulator actions as well as demonstrating its role as a member of the radical SAM enzyme family. However, despite the rapid expansion of knowledge regarding the functions of this highly conserved and ancient antiviral protein, there still remains large gaps in our understanding of the precise mechanisms at play for viperin to exert such a wide variety of roles within the cell.
Pub.: 26 Oct '13, Pinned: 31 Jul '17