key: cord-297579-ohpm5ys0 authors: Netzler, Natalie E.; Enosi Tuipulotu, Daniel; White, Peter A. title: Norovirus antivirals: Where are we now? date: 2018-12-25 journal: Med Res Rev DOI: 10.1002/med.21545 sha: doc_id: 297579 cord_uid: ohpm5ys0 Human noroviruses inflict a significant health burden on society and are responsible for approximately 699 million infections and over 200 000 estimated deaths worldwide each year. Yet despite significant research efforts, approved vaccines or antivirals to combat this pathogen are still lacking. Safe and effective antivirals are not available, particularly for chronically infected immunocompromised individuals, and for prophylactic applications to protect high‐risk and vulnerable populations in outbreak settings. Since the discovery of human norovirus in 1972, the lack of a cell culture system has hindered biological research and antiviral studies for many years. Recent breakthroughs in culturing human norovirus have been encouraging, however, further development and optimization of these novel methodologies are required to facilitate more robust replication levels, that will enable reliable serological and replication studies, as well as advances in antiviral development. In the last few years, considerable progress has been made toward the development of norovirus antivirals, inviting an updated review. This review focuses on potential therapeutics that have been reported since 2010, which were examined across at least two model systems used for studying human norovirus or its enzymes. In addition, we have placed emphasis on antiviral compounds with a defined chemical structure. We include a comprehensive outline of direct‐acting antivirals and offer a discussion of host‐modulating compounds, a rapidly expanding and promising area of antiviral research. risk and vulnerable populations in outbreak settings. Since the discovery of human norovirus in 1972, the lack of a cell culture system has hindered biological research and antiviral studies for many years. Recent breakthroughs in culturing human norovirus have been encouraging, however, further development and optimization of these novel methodologies are required to facilitate more robust replication levels, that will enable reliable serological and replication studies, as well as advances in antiviral development. In the last few years, considerable progress has been made toward the development of norovirus antivirals, inviting an updated review. This review focuses on potential therapeutics that have been reported since 2010, which were examined across at least two model systems used for studying human norovirus or its enzymes. In addition, we have placed emphasis on antiviral compounds with a defined chemical structure. We include a comprehensive outline of directacting antivirals and offer a discussion of host-modulating compounds, a rapidly expanding and promising area of antiviral research. although the same high prevalence of this strain was not reflected in other parts of the world, with lower levels detected in Australasia, Europe, and North America compared to the Asian outbreaks during that same period. [31] [32] [33] The human norovirus positive-sense, single-stranded RNA genome is 7.5 to 7.7 kb ( Figure 1 Karst et al 36 ) . ORF2 and ORF3 encode the proteins VP1 and VP2, respectively; VP1 is the major capsid protein and VP2 is the minor capsid protein, likely involved in capsid assembly and genome encapsidation. 37 The VP1 protein structure comprises the shell (S) and protruding (P) domains; the S domain encloses the viral RNA, while the antigenically variable P domain forms the outer surface of VP1, and is also involved in cell attachment. 38, 39 The VP1 protein can be expressed in baculovirus which then self-assembles into virus-like particles (VLPs). These VLPs are antigenically and structurally indistinguishable to virions produced by the complete virus. 40 Despite the clinical significance of norovirus infection, antiviral studies have been hindered, because until recently, human norovirus could not be successfully propagated in cell culture. Recent breakthroughs have enabled human norovirus to be cultured in B cells 41 and intestinal enteroids, 42 which represent milestones in the field of norovirus biology. However, the modest replication levels generated by these new systems (≤3.5 log increase in B cells 41, 43 F I G U R E 1 Schematic of the human norovirus genome. The norovirus genome is a positive-sense, singlestranded RNA genome comprising three ORFs that encode the nonstructural proteins: p48/N-terminal (NS1/2), NTPase (NS3), p22 (NS4), VPg (NS5), protease (NS6), and RNA polymerase (NS7); and the structural proteins: and ≤3.8 log increase in enteroids 42 ) means that they require optimization before widespread use for antiviral screening and development. The GI.1 (Norwalk virus) norovirus replicon system has been used to assess antiviral candidates against the human virus in lieu of a viral culture system ( Figure 2 ). The Norwalk replicon consists of an intact ORF1, ORF3, and genomic 3′ end, however, ORF2 is disrupted by a neomycin gene, engineered into the VP1-encoding region. As such, while the subgenomic promoter is preserved, the expression of an intact VP1 is disrupted. Self-replicating and stably expressed in Huh-7 cells or BHK-21 cell lines, 44 the Norwalk replicon has proven itself as a useful tool to screen potential antiviral compounds (Table 1) . However, replication levels of the Norwalk replicon are relatively low (approximately 1 × 10 3 Norwalk RNA copies per cell 44 ) , when compared to other replicon systems such as those for hepatitis C virus (HCV). The HCV replicons typically yield more than 1 × 10 4 copies per cell (AA Eltahla, 2018 personal communication), and have been used to identify many successful antiviral candidates. Moreover, they are amenable to high-throughput antiviral screening (reviewed in Horscroft et al 45 ) , which has directly led to many of the direct-acting antivirals (DAAs) used to treat HCV infections today (reviewed in Asselah et al 46 ) . Other models have also been used to study antiviral efficacy against norovirus ( Figure 2 ). For example, researchers have used in vitro enzyme activity assays, such as viral polymerase assays 47 and protease assays 48 (Figure 2 ) to screen compounds for antiviral activity in a high-throughput format. 49 In addition, X-ray crystallography and in silico modeling can be used to examine ligand and viral protein interactions, to further elucidate antiviral mechanisms. 50 F I G U R E 2 Current methods for the identification and characterization of norovirus antivirals. A flow chart depicting the methods and tools available for assessing the effectiveness of norovirus antivirals. Panels in green involve a combination of in silico and in vitro methods. Panels in blue and yellow represent in vitro and in vivo methods, respectively. The purple panel represents clinical testing in human patients. CRFK, Crandell Rees feline kidney; IC 50 , half maximal inhibitory concentration; qRT-PCR, quantitative reverse-transcription polymerase chain reaction; RdRp: RNA-dependent RNA polymerase; SAR, structure-activity relationship; TCID50, tissue culture infective dose [Color figure can be viewed at wileyonlinelibrary.com] The replication cycle and antiviral targets for human norovirus. (A), A schematic of the complete norovirus replication cycle is presented and antivirals that have been developed against norovirus are depicted in turquoise circles. The listed compounds represent only those antivirals which have a known target and a more extensive list of antivirals has been described in Table 1 Surrogate viruses from within the Caliciviridae family have also been exploited to screen for inhibitory activity of antiviral candidates across several calicivirus genera ( Figure 2 ). These surrogates include murine norovirus (MNV; Norovirus), feline calicivirus (FCV; Vesivirus), porcine sapovirus (Sapovirus), rabbit hemorrhagic disease virus (RHDV; Lagovirus), and Tulane virus, from the proposed genus Recovirus. 51 MNV, in particular, has been used as the predominant human norovirus surrogate as it is classified within the same genus and can be robustly propagated in cell culture, 52, 53 making it amenable to viral disinfection and sterilization studies. [54] [55] [56] Additional features that make MNV desirable for antiviral screening include its ability to be manipulated through reverse genetics, whilst in vivo studies in mice of many genetic backgrounds are straightforward. 57, 58 Various animal models have also been used for human norovirus challenge studies and include: nonhuman primates such as chimpanzees, macaques, marmosets, and tamarins. [59] [60] [61] Additionally, gnotobiotic or miniature pigs and gnotobiotic calves [62] [63] [64] [65] [66] have also been used, as well as knockout and humanized mice for norovirus infection studies. [67] [68] [69] However, no animal model has been deemed entirely suitable, due to obvious differences in clinical disease, gut physiology, microbiomes, naivety to norovirus infection compared to human populations, and the low genetic diversity of laboratory test animals. 36 Every stage of the human norovirus replication cycle represents a unique target for antiviral development ( Figure 3 ). However, the development of antiviral therapies that target viral replication requires a detailed understanding of norovirus biology and viral gene functionality, much of which is still to be elucidated. An overview of the human norovirus lifecycle and the specific antiviral targets are outlined in Figure 3 . The stages of the replication cycle for antiviral targeting include: host cell attachment, internalization, genome release, viral genome replication mediated by the viral RdRp, translation of the genomic and subgenomic templates using the VPg and host cell machinery, viral protease cleavage of the viral polyprotein to yield mature viral proteins, followed by assembly, packaging, and cell egress (reviewed in Thorne and Goodfellow 70 ). While a number of other norovirus antiviral reports have been published in the last three years, [71] [72] [73] [74] [75] there has been significant recent progress in the field, which now warrants an updated review. Herein we include a comprehensive overview of peer-reviewed studies since 2010, including antiviral candidates examined in at least two different systems (e.g. viral enzyme inhibition assays and MNV cell culture). It should be noted that plant or food extracts that have antinorovirus effects have been omitted from this study when the active antiviral compound is unknown, with this review focusing on compounds that have a defined structure (as outlined in Table 1 ). We include studies using the recently developed human norovirus cell culture system in B cells. 41 We also discuss recently identified broad-spectrum antivirals with antinorovirus activity and provide a more comprehensive overview of host-modulating compounds, which is a recent, novel and exciting area within norovirus antiviral research. Table 1 lists the individual antiviral compounds, or in the case where several very similar derivatives have been studied, it lists the most potent compound of the group as a representative derivative, with relevant citations. Each compound is indexed for clarity throughout the manuscript and in Table 1 . Cell attachment and entry are features of the viral replication cycle that have been extensively investigated as antiviral targets for human immunodeficiency virus (HIV), dengue virus (DENV), and HCV, 76 amongst others. To design compounds capable of targeting viral entry, knowledge of the viral entry receptor/s is usually required. Recently, CD300lf was identified as the entry receptor for MNV, however, the counterpart receptor for human norovirus has yet to be discovered. 77, 78 As such, there is an absence of antivirals that target norovirus entry and a bias toward compounds that prevent norovirus cellular attachment. The most widely studied attachment targets are the histo-blood group antigens (HBGAs). HBGAs are complex carbohydrates that are presented abundantly on the surface of mucosal epithelia of the gastrointestinal tract. They interact with the surface P2 domain of the VP1 capsid protein 79, 80 and are thought to aid viral attachment, and perhaps even entry. [81] [82] [83] HBGAs are determined by host cell genetics (reviewed in Tan and Jiang 82 ) and play an important role in terms of both virus and host interactions, and for noroviruses to initiate infection. 81, 84 In one study, in silico screening was performed on a drug library (>2 million compounds) to identify molecules that interact strongly with HBGAs and prevent norovirus attachment. 85 Potential hits (n = 160) were confirmed in vitro with enzyme-linked immunosorbent assay (ELISA)-based human norovirus VP1/HBGA blocking assays, which revealed that compounds with a cyclopenta-a-dimethyl phenanthrene base structure (n = 4) display potent inhibition (IC 50 < 10 μM) of HBGA-norovirus binding. 85 The most potent compound in this series was 88 In addition, X-ray crystallography has revealed that these HMOs interact directly with the P domain of the capsid, thus providing a clear mechanism for the binding inhibition observed. [86] [87] [88] Despite these advances, attachment inhibitors have only been tested against VLPs from less common genotypes and thus their effectiveness against a broader spectrum of norovirus strains needs to be demonstrated. Passive immunotherapy with monoclonal antibodies (mAbs) or nanobodies (Nbs) is an antiviral strategy to prevent norovirus attachment and entry, which would be particularly useful for immunocompromised patients. The cross-genotypic activity displayed by Nbs illustrates that these molecules have the potential to overcome the narrow antigenic spectrum typically displayed by conventional mAbs. However, despite these findings, mAb and Nb studies have been based mostly on VLP-binding and structural analysis of that binding (Table 1 ) and thus the effects of such compounds against norovirus in cell culture or in vivo need to be explored further before continued development toward clinical application. Of the human norovirus antiviral targets, the RdRp is one with numerous preclinical candidates identified that can inhibit its activity (Table 1) . Critical for viral replication, the RdRp is a highly attractive antiviral target, as it largely NETZLER ET AL. lacks host homologs minimizing the chance of off-target adverse effects. 96 The human norovirus polymerase forms the canonical RdRp structure resembling a closed right hand, with fingers, palm, and thumb domains 97 ( Figure 3B ), likely acting as a homodimer in it active state. [97] [98] [99] The RdRp-targeting antivirals are divided into two major classes; the nucleoside analogs (NAs) and the nonnucleoside inhibitors (NNIs NAs inhibit RNA synthesis through mimicry of incoming nucleoside triphosphates (NTPs), which upon incorporation subsequently cause chain termination, 105 or less commonly, increase mutations during viral genome transcription that results in lethal mutagenesis (also known as error catastrophe). 106 110 Another study reported a similar 2CMC potency for MNV RNA level reduction (6.9 µM), but potency against the Norwalk replicon was found to be 14-fold higher (1.3 µM). 111 This difference was proposed to be due to either varying methodology between studies, or differences in drug purity. 110 In the human norovirus BJAB cell culture system, 2CMC inhibited human norovirus replication with an EC 50 of 0.3 µM. 67 Despite the variation in 2CMC potency observed between these in vitro systems, collectively these studies illustrate that the polymerase is an excellent antiviral target for cross-genogroup inhibition of norovirus replication. The NA 2CMC has also shown promise as a potential norovirus antiviral in mouse model studies. Knockout mice infected with MNV and treated with 2CMC were protected from mortality, diarrhea, and had reduced norovirus genome titers in tissues and stool (1.0-1.5 log 10 reduction), compared to mock-treated animals. 67, 110 Additionally, MNV-infected mice treated with a high dose of 2CMC (100 mg/kg/day for 5-7 days) demonstrated reduced transmission to uninfected sentinel mice caged together, and offered prophylactic protection for up to 18 days. 112 In an attempt to improve the safety and efficacy of 2CMC therapy, several derivatives have been examined for antinorovirus activity, for example, 2′-F-2′-C-methylcytidine (2FCMC). One study evaluated the inhibitory activity of 2CMC, 2FCMC, β-D-N(4)-hydroxycytidine (NHC) and the HBV/HIV NA lamivudine against the replication of MNV and the Norwalk replicon. 111 has potent and pan-genotypic activity against norovirus. 128 CMX521 is reportedly in the recruitment stage of phase I clinical trials to evaluate the safety, tolerability, and pharmacokinetics in less than or equal to 50 healthy adults. No peer-reviewed publications were available when writing this review, with results projected to be released later in 2018. 128 NNIs generally exhibit narrow-spectrum antiviral activity and bind allosterically to block conformational rearrangements of the viral polymerase required to form an active replication complex. 129 Currently, there are three known NNI binding sites on the norovirus RdRp. One binding pocket is within the NTP access path located between the fingers and thumb domains, 130 the second pocket is termed Site A, a positively charged NTP traversal channel with flexible amino acid side chains, 131 and the third pocket is Site B, a highly conserved allosteric binding pocket present across the Caliciviridae and located within the thumb region 131,132 ( Figure 3B ). Despite the promising potency of suramin and its derivatives, including PPNDS, these compounds demonstrate limited bioavailability and exhibit poor cell permeability, 134 greatly reducing their antiviral efficacy in viral culture. 132, 135, 136 While suramin has been shown to inhibit MNV replication in cell culture (EC 50 0.3 µM), the large structure and low cell permeability meant delivery required a liposome system to enter RAW264.7 cells. 135 Similarly, PPNDS was found to be much less potent in MNV cell culture, demonstrating only 20.5% inhibition of MNV replication in a plaque assay at 10 µM, compared to 98.0% inhibition at the same concentration in the RdRp assays. 132 Moreover, PPNDS has been eliminated from other enzyme inhibition studies due to nonspecific, offtarget effects, 137 and is therefore likely to be an unsuitable drug candidate for further antinorovirus development. Much like the RdRp, the norovirus protease (NS6; Figure 3C ) represents a desirable antiviral target since it plays an essential role in viral replication, through cleavage of the NS polyprotein, which is necessary for the production of viral progeny. Norovirus protease inhibitors (PIs) have been tested over a wide range of model antiviral systems ( Figure 2 ) and represent the class of calicivirus antivirals with the most number of compounds (Table 1) 141 Although potent, TS mimics are far less studied than TS inhibitors and represent a small proportion of the compounds described in Table 1 . The first TS inhibitors designed included a series of peptidyl aldehydes that incorporated a glutamine surrogate in their structure, 142 and take advantage of the preference for the norovirus protease to cleave at glutamineglycine peptide sites. 143 of Rupintrivir. 154 The effectiveness of PIs across multiple genera and norovirus genogroups illustrates that the protease is an excellent antiviral candidate for the treatment of norovirus infections. A pitfall of using some DAAs is the emergence of resistance mutations which can undermine their effectiveness, although combinational therapy is a proven option in HIV and HCV therapy to circumvent this. In comparison to DAAs, antivirals that target the host generally have a higher barrier to resistance than some classes of DAAs, 158 However, this initial study revealed that inhibition of MNV in mice was limited to the small intestine due to poor bioavailability of WP1130. 158 To address the poor bioavailability, libraries of WP1130 variants were developed and tested for improved antiviral efficacy. 156 Immunomodulators are an excellent therapeutic option for viral infections due to their ability to induce a powerful host response against intracellular parasites. The best example of immunomodulators are interferons (IFNs) and for over a decade, studies have shown that type I and II IFNs, as well as their receptors, provide protection against murine and human norovirus infections. 44, 52, 53, [163] [164] [165] [166] [167] [168] However, the role of type III IFNs (IFN-λ), in norovirus infection and their potential as norovirus antivirals has only recently been explored. 169 inhibition at 50 U/mL and~50% inhibition of the Norwalk replicon at 100 U/mL. Vitamin A-induced changes in the microflora are thought to be the mechanism responsible for these antiviral effects. 188 Lastly, nitazoxanide (NTZ) [2.5.4 ] (covered in section 3) has shown promise as an antiviral therapy, but the defined mechanism of activity against norovirus has yet to be determined. Most recently NTZ was shown to potently inhibit FCV replication in cell culture with an EC 50 of 0.6 µM, 189 and the GI norovirus replicon at a clinically relevant concentration (5 μg/mL), 190 which was later shown to result in a broad antiviral response. 191 Despite these observations, the latter study also showed that NTZ was ineffective against MNV suggesting that further antiviral investigations are warranted. 189 To date, no norovirus antiviral or vaccine is approved for medical use, and the only norovirus antiviral candidate to complete clinical trials is NTZ. This compound was originally developed in the 1970s, and is currently an FDAapproved therapy for treating Giardia and Crytosporidium infections. 192 NTZ has demonstrated broad-spectrum antimicrobial activity against a range of bacterial, protozoan, and viral infections, including inhibition of the Norwalk replicon (EC 50 1.6 µM) (reviewed in Rossignol 193 ). In phase II randomized double-blind trial, NTZ therapy was administered to 25 of 50 patients (≥ 12 years) that tested positive for rotavirus or norovirus infection. Treatment resulted in a significant reduction in the duration of gastroenteritis symptoms (norovirus, P = 0.0295 and rotavirus, P = 0.0052) from 2.5 to 1.5 days when compared to the placebo. 194 Additional anecdotal studies have supported the efficacy of NTZ treatment for norovirus. NTZ successfully treated one immunosuppressed transplant patient infected with norovirus that had experienced 10 consecutive days of gastroenteritis symptoms. 195 Four days after commencing NTZ treatment, a complete resolution of symptoms was recorded without a reduction in immunosuppressive drugs. 195 NTZ treatment was also shown to resolve diarrheal symptoms and clear norovirus in stool samples from a pediatric patient with chronic norovirus, following kidney transplantation. 196 Although the above-mentioned studies suggest that NTZ is a promising therapy for the treatment of norovirus infections, there is an equal amount of evidence revealing that NTZ is ineffective against norovirus NETZLER ET AL. infections. [197] [198] [199] [200] Despite this contrary evidence, NTZ represents the only therapeutic option currently available apart from RBV, immunoglobulins and supportive care to patients with persistent infections. Human norovirus is a pervasive pathogen that creates a significant social and economic impact and causes hundreds of thousands of deaths each year. Despite intensive research for safe and effective norovirus antivirals, none have yet been clinically approved, and the majority of candidates are still in the early stages of preclinical development. This review outlines recent therapeutic candidate studies to provide an updated overview of the current human norovirus antiviral development pipeline. Optimization of human norovirus culture in enteroid and B cell systems offers the promise that in time, more robust and reliable culture methods will be developed allowing greater replication levels. These improved systems may enhance antiviral studies to provide a stronger platform for effective norovirus antiviral development. The landscape of antiviral development for norovirus is changing. The rapidly developing field of host immunomodulatory therapies is opening the door to potential treatments for many viral infections, with promising results already published for norovirus. Moreover, recent discoveries have reported highly conserved binding pockets on critical viral enzymes, such as the norovirus polymerase, which could allow for the further development of broad-spectrum antivirals. 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regulatory factor 1 in IFN-γ-mediated inhibition of norovirus replication in macrophages Critical role for interferon regulatory factor 3 (IRF-3) and IRF-7 in type I interferon-mediated control of murine norovirus replication Type I and type II interferons inhibit the translation of murine norovirus proteins Interferons and ribavirin effectively inhibit Norwalk virus replication in replicon-bearing cells MDA-5 recognition of a murine norovirus The role of interferon in persistent viral infection: insights from murine norovirus Distinct and overlapping genomic profiles and antiviral effects of Interferon-λ and-α on HCV-infected and noninfected hepatoma cells Dynamic expression profiling of type I and type III interferon-stimulated hepatocytes reveals a stable hierarchy of gene expression IL-28, IL-29 and their class II cytokine receptor IL-28R IFN-λs mediate antiviral protection through a distinct class II cytokine receptor complex Interferon-λ cures persistent murine norovirus infection in the absence of adaptive immunity Expression of Ifnlr1 on intestinal epithelial cells is critical to the antiviral effects of interferon lambda against norovirus and reovirus Interferon lambda (IFN-λ) efficiently blocks norovirus transmission in a mouse model GS-9620, an oral agonist of Toll-like receptor-7, induces prolonged suppression of hepatitis B virus in chronically infected chimpanzees TLR7 agonist GS-9620 is a potent inhibitor of acute HIV-1 infection in human peripheral blood mononuclear cells TLR7 agonists display potent antiviral effects against norovirus infection via innate stimulation Prophylactic efficacy of orally administered Bacillus poly-γ-glutamic acid, a non-LPS TLR4 ligand, against norovirus infection in mice Toll-like receptors: the swiss army knife of immunity and vaccine development Imiquimod for the treatment of genital warts: a quantitative systematic review Antiviral effect of theaflavins against caliciviruses Inhibitory mechanism of five natural flavonoids against murine norovirus Comparison of the antiviral activity of flavonoids against murine norovirus and feline calicivirus Naturally occurring flavonoids against human norovirus surrogates Curcumin shows antiviral properties against norovirus Antiviral effect of vitamin A on norovirus infection via modulation of the gut microbiome Potential therapeutic agents for feline calicivirus infection Opposing effects of nitazoxanide on murine and human norovirus Nitazoxanide inhibits human norovirus replication and synergizes with ribavirin by activation of cellular antiviral response Nitazoxanide: a new thiazolide antiparasitic agent Nitazoxanide: a first-in-class broad-spectrum antiviral agent Nitazoxanide in the treatment of viral gastroenteritis: a randomized double-blind placebo-controlled clinical trial Norovirus gastroenteritis successfully treated with nitazoxanide Successful treatment of chronic norovirus gastroenteritis with nitazoxanide in a pediatric kidney transplant recipient Chronic diarrhea associated with persistent norovirus excretion in patients with chronic lymphocytic leukemia: report of two cases Chronic norovirus infections in cardiac transplant patients: considerations for evaluation and management Nitazoxanide is an ineffective treatment of chronic norovirus in patients with x-linked agammaglobulinemia and may yield false-negative polymerase chain reaction findings in stool specimens Prolonged norovirus infection after pancreas transplantation: a case report and review of chronic norovirus Her project focuses on identifying antiviral compounds for norovirus and other caliciviruses. In particular, her interest lies in the discovery of broad-spectrum antivirals with the potential to rapidly treat several clinically significant viruses for which we currently have no antivirals. During her PhD, Natalie was an author and editor for the book Foodborne Viral Pathogens UNSW and has been a tutor and demonstrator on the 2nd and 3rd year microbiology and virology courses Following graduation, Natalie worked as a research assistant at the biotechnology company, Genesis Research and Development, for several years, investigating ligands involved in plant flowering and siRNA inhibition targeting drug resistance He completed a B.Med Sci with first class Honors majoring in Microbiology and Immunology from the University of New South Wales in 2014 and is currently a PhD candidate at UNSW focusing on the biology of norovirus is also involved in teaching at UNSW, including tutor and demonstration roles biology and microbiology He has a breadth of experience in the development of novel molecular assay systems and next-generation sequencing to investigate viral infections Prof White commenced his postdoctoral research studies at the Macquarie University, Sydney, as a recipient of a Royal Society Fellowship and later worked as Hepatitis Group Leader at the Prince of Wales Hospital until joining the University of New South Wales in 2003. He is also an enthusiastic teacher, having convened the third-year science course Viruses and Disease for 15 years at UNSW. How to cite this article The authors declare that there are no conflicts of interest.