Biology subjects

Hurt, A. C.

Publications and source records attributed to Hurt, A. C..

11 recordsLinked to original sources

bioRxiv2022

A new concept in antiviral drug design

Contemporary antiviral development, whether by rational drug design or forward pharmacology, primarily strives to produce lock and key inhibitors. While the technology to identify druggable targets and create compounds to bind them has improved dramatically over the last century it has always been constrained by the finite availability of suitable binding sites that antiviral compounds can occupy. Here we present a new approach to drug design that utilizes compounds devised to alter the microenvironment of the virion surface making it incompatible with virus entry and illustrate this strategy with inhibitors of influenza virus. We show that compounds that produce a proton-rich mantle above the virion surface induce a conformational change in the viral hemagglutinin (HA) rendering the virus unable to interact with cellular receptors and gain entry to the cell. The compounds show exceptional antiviral activity both in vitro and in vivo and protect against influenza illness in mice and ferrets after a single dose, either therapeutically or prophylactically. The work presented here lays the foundation for a brand-new category of inhibitors that could be engineered to counter many different viruses and potentially other pathogens.

microbiology↗

bioRxiv2022

Robustness of the ferret model for influenza risk assessment studies: a cross-laboratory exercise

Ferrets represent the preferred animal model for assessing the transmission potential of newly emerged zoonotic influenza viruses. However, heterogeneity among established experimental protocols and facilities across different laboratories may lead to variable results, complicating interpretation of transmission experimental data. Between 2018-2020, a global exercise was conducted by 11 participating laboratories to assess the range of variation in ferret transmission experiments using two common stock H1N1 influenza viruses that possess different transmission characteristics in ferrets. Inoculation route, dose, and volume were standardized, and all participating laboratories followed the same experimental conditions for respiratory droplet transmission, including a strict 1:1 donor:contact ratio. Additional host and environmental parameters likely to affect influenza transmission kinetics were monitored throughout. Overall transmission outcomes for both viruses across 11 laboratories were concordant, suggesting the robustness of the ferret model for zoonotic influenza risk assessment. To attain high confidence in identifying zoonotic influenza viruses with moderate-to-high or low transmissibility, our analyses support that as few as three but as many as five laboratories, respectively, would need to independently perform viral transmission experiments with concordant results. This exercise facilitates the development of a more homogenous protocol for ferret transmission experiments that are employed for the purposes of risk assessment.

microbiology↗

bioRxiv2022

Strong phylogenetic and ecological effects on host competency for avian influenza in Australian wild birds

Host susceptibility to parasites is mediated by intrinsic and external factors such as genetics, age or season. While key features have been revealed for avian influenza A virus (AIV) in waterfowl of the Northern Hemisphere, the role of host phylogeny has received limited attention. Herein, we analysed 12339 oropharyngeal and cloacal swabs and 10826 serum samples collected over 11 years from wild birds in Australia. As well as describing species-level differences in prevalence and seroprevalence, we reveal that host phylogeny is a key driver in susceptibility. We confirm the role of age in AIV seroprevalence and viral prevalence. Seasonality effects appear less pronounced than in the Northern Hemisphere, while annual variations are potentially linked to El Nino- Southern Oscillation. Taken together, our study provides new insights into evolutionary ecology of AIV in its avian hosts, defining distinctive processes on the continent of Australia and expanding our understanding of AIV globally.

microbiology↗

bioRxiv2021

Australia as a global sink for the genetic diversity of avian influenza A virus

Most of our understanding of the ecology and evolution of avian influenza A virus (AIV) in wild birds is derived from studies conducted in the northern hemisphere on waterfowl, with a substantial bias towards dabbling ducks. However, relevant environmental conditions and patterns of avian migration and reproduction are substantially different in the southern hemisphere. Through the sequencing and analysis of 333 unique AIV genomes collected from wild birds collected over 15 years we show that Australia is a global sink for AIV diversity and not integrally linked with the Eurasian gene pool. Rather, AIV are infrequently introduced to Australia, followed by decades of isolated circulation and eventual extinction. The number of co-circulating viral lineages varies per subtype. AIV haemagglutinin (HA) subtypes that are rarely identified at duck-centric study sites (H8-12) had more detected introductions and contemporary co-circulating lineages in Australia. Combined with a lack of duck migration beyond the Australian-Papuan region, these findings suggest introductions by long-distance migratory shorebirds. In addition, we found no evidence of directional or consistent patterns in virus movement across the Australian continent. This feature corresponds to patterns of bird movement, whereby waterfowl have nomadic and erratic rainfall-dependant distributions rather than consistent intra-continental migratory routes. Finally, we detected high levels of virus gene segment reassortment, with a high diversity of AIV genome constellations across years and locations. These data, in addition to those from other studies in Africa and South America, clearly show that patterns of AIV dynamics in the Southern Hemisphere are distinct from those in the temperate north. Author SummaryA result of the ever-growing poultry industry is a dramatic global increase in the incidence of high pathogenicity avian influenza virus outbreaks. In contrast, wild birds are believed to be the main reservoir for low pathogenic avian influenza A virus. Due to intensive research and surveillance of AIV in waterfowl in the Northern Hemisphere, we have a better understanding of AIV ecology and evolution in that region compared to the Southern Hemisphere, which are characterised by different patterns of avian migration and ecological conditions. We analysed 333 unique AIV genomes collected from wild birds in Australia to understand how Australia fits into global AIV dynamics and how viruses are maintained and dispersed within the continent of Australia. We show that the Southern Hemisphere experiences differing evolutionary dynamics to those seen in Northern Hemisphere with Australia representing a global sink for AIV.

evolutionary biology↗

bioRxiv2021

A novel and highly divergent Canine Distemper Virus lineage causing distemper in ferrets in Australia

Canine distemper virus (CDV) is a highly contagious systemic viral disease of dogs, that regularly spills-over into other animal species. Despite widespread vaccination, CDV remains endemic in many parts of the world. In this study we report an outbreak of distemper in ferrets in two independent research facilities in Australia. We found that disease severity varied, although most animals had mild to moderate disease signs. Histopathology results of animals with severe disease presented the typical profile of distemper pathology with multi-system virus replication. Through the development of a discriminatory PCR paired with full genome sequencing we revealed that the outbreak at both facilities was caused by a single, novel lineage of CDV. This lineage was highly divergent across the H gene, F signal peptide and full genome and had less than 93% similarity across the H gene to other described lineages, including the vaccine strain. Molecular analysis indicates that this strain belongs to a distinct lineage that diverged from other clades approximately 140 to 400 years ago, and appears to be unique to Australia. Given the differences in key viral proteins of this novel CDV strain, a review of the efficacy of the CDV vaccines currently in use in Australia is warranted to ensure maximum protection of dogs and other vulnerable species. In addition, enhanced surveillance to determine the prevalence of CDV in ferrets, dogs and other at-risk species in Australia would be useful to better understand the diversity of CDV in Australia. ImportanceCanine distemper virus (CDV) is highly contagious and while dogs are the main reservoir, it may spill over into a number of other animal species. In this study we report an outbreak of distemper in ferrets in two research facilities in Australia. Outcomes of pathology and histopathology suggest ferrets have widespread multi-systemic infection, consistent with previously reported distemper infections in ferrets and dogs. Critically, through sequencing and phylogenetic analysis, we revealed that the outbreak at both facilities was caused by a single, novel and highly divergent lineage of CDV. This virus had less than 93% nucleotide similarity to other described lineages and the vaccine strain. This manuscript adds considerably to the epidemiology, ecology and evolution of this virus, and is one of few reports of distemper in Australia in the literature.

microbiology↗

bioRxiv2021

Predicting potentially permissive substitutions that improve the fitness of A(H1N1)pdm09 viruses bearing the H275Y NA substitution

Oseltamivir-resistant influenza viruses arise due to amino-acid mutations in key residues, but these changes often reduce their replicative and transmission fitness. Widespread oseltamivir-resistance has not yet been observed in A(H1N1)pdm09 viruses. However, it is known that permissive mutations in the neuraminidase (NA) of former seasonal A(H1N1) viruses from 2007-2009 buffered the detrimental effect of the NA H275Y mutation, resulting in fit oseltamivir-resistant viruses that circulated widely. This study explored two approaches to predict permissive mutations that may enable a fit H275Y A(H1N1)pdm09 variant to arise. A computational approach used phylogenetic and in silico protein stability analyses to predict potentially permissive mutations, which were then evaluated by in vitro NA enzyme activity and expression analysis, followed by in vitro replication. The second approach involved the generation of a virus library which encompassed all possible individual 2.9 x 104 codon mutations in the NA whilst keeping H275Y fixed. To select for variant viruses with the greatest fitness, the virus library was serially passaged in ferrets (via contact and aerosol transmission) and resultant viruses were deep sequenced. The computational approach predicted three NA permissive mutations, and even though they only offset the in vitro impact of H275Y on NA enzyme expression by 10%, they could restore replication fitness of the H275Y variant in A549 cells. In our experimental approach, a diverse virus library (97% of 8911 possible single amino-acid substitutions were sampled) was successfully transmitted through ferrets, and sequence analysis of resulting virus pools in nasal washes identified three mutations that improved virus transmissibility. Of these, one NA mutation, I188T, has been increasing in frequency since 2017 and is now present in 90% of all circulating A(H1N1)pdm09 viruses. Overall, this study provides valuable insights into the evolution of the influenza NA protein and identified several mutations that may potentially facilitate the emergence of a fit H275Y A(H1N1)pdm09 variant.

microbiology↗

bioRxiv2020

Evaluating the fitness of PA/I38T-substituted influenza A viruses with reduced baloxavir susceptibility in a competitive mixtures ferret model

Baloxavir is approved in several countries for the treatment of uncomplicated influenza in otherwise-healthy and high-risk patients. Treatment-emergent viruses with reduced susceptibility to baloxavir have been detected in clinical trials, but the likelihood of widespread occurrence depends on replication capacity and onward transmission. We evaluated the fitness of A/H3N2 and A/H1N1pdm09 viruses with the polymerase acidic I38T-variant conferring reduced susceptibility to baloxavir relative to wild-type (WT) viruses, using a competitive mixture ferret model, recombinant viruses and patient-derived virus isolates. The A/H3N2 I38T virus showed a reduction in within-host fitness but comparable between-host fitness to the WT virus, while the A/H1N1pdm09 I38T virus had broadly similar within-host fitness but substantially lower between-host fitness. Although I38T viruses replicate and transmit between ferrets, our data suggest that viruses with this amino acid substitution have lower fitness relative to WT and this relative fitness cost was greater in A/H1N1pdm09 viruses than in A/H3N2 viruses.

microbiology↗

bioRxiv2020

Host age shapes virome abundance and diversity in birds

Host age influences the ecology of many microorganisms. This is evident in one-host - one virus systems, such as influenza A virus in Mallards, but also in community studies of parasites and microbiomes. We used a meta-transcriptomic approach to assess whether host age is associated with differences in the abundance and diversity of avian viromes. We used samples from cohabiting Ruddy Turnstones (Arenaria interpres) across three age groups, collected at two contrasting points in their annual migratory cycle. Overall, we identified 14 viruses that likely infect birds, 11 of which were novel, including members of the Reoviridae, Astroviridae, Picornaviridae, and Phenuiviridae. Strikingly, 12 of the viruses identified were from juvenile birds sampled in the first year of their life, compared to only two viruses in adult birds. Similarly, both viral abundance and alpha diversity were higher in juvenile than adult birds. Notably, time of sampling had no association with virome structure such that the migratory period may not play a major role in structuring avian viromes. As well as informing studies of virus ecology, that host age impacts viral assemblages is a critical consideration for the future surveillance of novel and emerging viruses.

microbiology↗

bioRxiv2018

High levels of antibiotic resistance gene expression among birds living in a wastewater treatment plant

Antibiotic resistance is rendering common bacterial infections untreatable. Wildlife can incorporate and disperse antibiotic resistant bacteria in the environment, such as water systems, which in turn serve as reservoirs of resistance genes for human pathogens. We used bulk RNA-sequencing (meta-transcriptomics) to assess the diversity and expression levels of functionally active resistance genes in the microbiome of birds with aquatic behavior. We sampled birds across a range of habitats, from penguins in Antarctica to ducks in a wastewater treatment plant in Australia. This revealed 81 antibiotic resistance genes in birds from all localities, including {beta}-lactam, tetracycline and chloramphenicol resistance in Antarctica, and genes typically associated with multidrug resistance plasmids in areas with high human impact. Notably, birds feeding at a wastewater treatment plant carried the greatest resistance gene burden, suggesting that human waste, even if it undergoes treatment, contributes to the spread of antibiotic resistance genes to the wild. Differences in resistance gene burden also reflected the birds ecology, taxonomic group and microbial functioning. Ducks, which feed by dabbling, carried a higher abundance and diversity of resistance genes than turnstones, avocets and penguins, that usually prey on more pristine waters. In sum, this study helps to reveal the complex factors explaining the distribution of resistance genes and their exchange routes between humans and wildlife.

ecology↗

bioRxiv2018

A divergent hepatitis D-like agent in birds

Hepatitis delta virus (HDV) is currently only found in humans, and is a satellite virus that depends on hepatitis B virus (HBV) envelope proteins for assembly, release and entry. Using meta-transcriptomics, we identified the genome of a novel HDV-like agent in ducks. Sequence analysis revealed secondary structures that were shared with HDV, including self-complementarity and ribozyme features. The predicted viral protein shares 32% amino acid similarity to the small delta antigen of HDV and comprises a divergent phylogenetic lineage. The discovery of an avian HDV-like agent has important implications for the understanding of the origins of HDV and subviral agents.\n\nImportanceHepatitis delta virus (HDV) is currently only found in humans, and coinfections of HDV and Hepatitis B virus (HBV) in humans result in severe liver disease. There are a number of hypotheses for the origin of HDV, although a key component of all is that HDV only exists in humans. Here, we describe a novel deltavirus-like agent identified in wild birds. Although this agent is genetically divergent, it exhibits important similarities to HDV, such as the presence of ribosymes and self-complementarity. The discovery of an avian HDV-like agent challenges our understanding of both the origin and the co-evolutionary relationships of subviral agents with helper viruses.

molecular biology↗

bioRxiv2018

Characterization of influenza B virus variants with reduced neuraminidase inhibitor susceptibility

Treatment options for influenza B virus infections are limited to neuraminidase inhibitors (NAIs) which block the neuraminidase (NA) glycoprotein on the virion surface. The development of NAI resistance would therefore result in a loss of antiviral treatment options for influenza B infections. This study characterized two contemporary influenza B viruses with known resistance-conferring NA amino acid substitutions, D197N and H273Y, detected during routine surveillance. The D197N and H273Y variants were characterized in vitro by assessing NA enzyme activity and affinity, as well as replication in cell culture compared to NAI-sensitive wild-type viruses. In vivo studies were also performed in ferrets to assess the replication and transmissibility of each variant. Mathematical models were used to analyse within-host and between-host fitness of variants relative to wild-type viruses. The data revealed that the H273Y variant had similar NA enzyme function relative to its wild-type but had slightly reduced replication and transmission efficiency in vivo. The D197N variant had impaired NA enzyme function but there was no evidence of reduction in replication or transmission efficiency in ferrets. Our data suggest that the influenza B variant with H273Y NA substitution had a more notable reduction in fitness compared to wild-type viruses than the influenza B variant with the D197N NA substitution. Although a D197N variant is yet to become widespread, it is the most commonly detected NAI-resistant influenza B virus in surveillance studies. Our results highlight the need to carefully monitor circulating viruses for the spread of influenza B viruses with the D197N NA substitution.

microbiology↗