Biology subjects

Turnbull, M. L.

Publications and source records attributed to Turnbull, M. L..

8 recordsLinked to original sources

bioRxiv2025

Spillover of H5 influenza viruses to vampire bats at the marine-terrestrial interface

The highly pathogenic H5N1 avian influenza A virus (IAV) clade 2.3.4.4b has spread globally and spilled over into multiple mammalian species, raising concerns about its pandemic potential. In late 2022, clade 2.3.4.4b viruses devastated seabird and marine mammal populations along the Pacific coast of South America. Here, we report the first evidence of H5 IAV infections in wild bats globally, focusing on common vampire bats (Desmodus rotundus) in coastal areas of Peru. Longitudinal serological screening, stable isotope analysis and metabarcoding revealed repeated exposures to H5 IAVs in vampire bats which feed on coastal wildlife species heavily impacted by the 2.3.4.4b epizootic, but no evidence of infection in populations without access to marine prey. We further report bat gene flow between IAV-exposed and IAV-naive populations, and IAV infections in a vampire bat colony that fed on both marine and terrestrial livestock prey, providing insights into how future IAV epizootics might spread spatially within bats and between marine and terrestrial ecosystems if a bat reservoir were established. Immunohistochemistry demonstrated that the H5 haemagglutinin protein binds to the upper respiratory tract of vampire bats, suggesting bat tissue susceptibility to H5 IAVs. Finally, vampire bat-derived kidney, liver, and lung cells supported entry, replication, and egress of avian and mammalian 2.3.4.4b viruses, confirming cellular infectivity. These results illustrate how combining ecological inference and experimental virology can pinpoint the species origins and biological significance of viral spillover at species interfaces. Recurrent exposures from marine wildlife, tissue and cellular susceptibility to H5N1 IAVs, and connections to other IAV-susceptible terrestrial mammals establish the prerequisite conditions for vampire bats to spread IAVs between marine and terrestrial environments or to form a novel reservoir of highly pathogenic IAVs.

ecology↗

bioRxiv2025

Alternative splicing broadens antiviral diversity at the human OAS2 locus

Interferons (IFN) are cytokines that regulate the expression of hundreds of genes during viral infections to generate a broadly antiviral environment in the stimulated cell. Antiviral breadth is provided by the concurrent expression of many individual IFN-stimulated genes (ISG), each encoding a protein with often exquisite antiviral specificity. Here, we show that mechanistic plasticity at a single genetic locus is a novel mechanism to diversify the antiviral profile of human cells. Through alternative splicing, the OAS2 gene encodes two antiviral molecules with distinct target specificities. The shorter OAS2 p69 isoform blocks the replication of seasonal human coronavirus OC43 (HCoV-OC43), while the longer p71 isoform restricts the replication of picornavirus Cardiovirus A (EMCV). The restriction profile is determined by the variable length OAS2 C-terminal tail. Remarkably, the antiviral mechanisms underlying these distinct antiviral profiles are either RNase L dependent or independent, suggesting that splicing divides classic restriction versus virus sensing systems across two distinct OAS2 polypeptides. Together, our data reveal that the human OAS2 locus uses alternative splicing and mechanistic plasticity to diversify antiviral profiles.

microbiology↗

bioRxiv2024

POLYGENIC DETERMINANTS OF H5N1 ADAPTATION TO BOVINE CELLS

Avian influenza H5N1 clade 2.3.4.4b viruses caused a global panzootic and, unexpectedly, widespread outbreaks in dairy cattle, therefore representing a pandemic threat. To inform effective control strategies, it is critical to determine whether the potential to adapt to bovine cells is a generalised feature of H5N1 viruses, or is specific to clade 2.3.4.4b, or even more restricted to specific genotypes within this clade (e.g., B3.13 and D1.1). Using a large panel of H5N1 viruses representing >60 years of their natural history and other IAV for comparative purposes, we demonstrate that virus adaptation to bovine cells is: (i) highly variable across 2.3.4.4b genotypes, (ii) limited in viruses predating the global expansion of this clade, (iii) determined by the viral internal gene cassette, and (iv) not restricted to udder epithelial cells. Mutations in the PB2 polymerase subunit, particularly M631L, emerge as key determinants of adaptation, although their phenotypic effects are context dependent and have limited enhanced viral polymerase activity in human cells. Bovine B3.13 and some avian genotypes also exhibit enhanced modulation of bovine interferon-induced antiviral responses, determined by at least the viral PB2, nucleoprotein, and the non-structural protein NS1. Our results highlight the polygenic nature of IAV host range and reveal that the potential to cross the species barrier varies during the evolutionary trajectory of H5N1, with some avian viruses more predisposed to spillover than others.

microbiology↗

bioRxiv2022

Zoonotic avian influenza viruses evade human BTN3A3 restriction

Cross-species transmission of avian influenza A viruses (IAVs) into humans could represent the first step of a future pandemic1. Multiple factors limiting the spillover and adaptation of avian IAVs in humans have been identified, but they are not sufficient to explain which virus lineages are more likely to cross the species barrier1,2. Here, we identified human BTN3A33 (butyrophilin subfamily 3 member A3) as a potent inhibitor of avian but not human IAVs. We determined that BTN3A3 is constitutively expressed in human airways and its antiviral activity evolved in primates. We show that BTN3A3 restriction acts at the early stages of virus replication by inhibiting avian IAV vRNA transcription. We identified residue 313 in the viral nucleoprotein (NP) as the genetic determinant of BTN3A3 sensitivity (313F, or rarely 313L in avian viruses) or evasion (313Y or 313V in human viruses). However, several serotypes of avian IAVs that spilled over into humans in recent decades evade BTN3A3 restriction. In these cases, BTN3A3 evasion is due to substitutions (N, H or Q) in NP residue 52 that is adjacent to residue 313 in the NP structure4. Importantly, we identified more than 150 avian IAV lineages with a BTN3A3-resistant genotype. In conclusion, sensitivity or resistance to BTN3A3 is another factor to consider in the risk assessment of the zoonotic potential of avian influenza viruses.

microbiology↗

bioRxiv2021

In vitro evolution of Remdesivir resistance reveals genome plasticity of SARS-CoV-2

Remdesivir (RDV) is used widely for COVID-19 patients despite varying results in recent clinical trials. Here, we show how serially passaging SARS-CoV-2 in vitro in the presence of RDV selected for drug-resistant viral populations. We determined that the E802D mutation in the RNA-dependent RNA polymerase was sufficient to confer decreased RDV sensitivity without affecting viral fitness. Analysis of more than 200,000 sequences of globally circulating SARS-CoV-2 variants show no evidence of widespread transmission of RDV-resistant mutants. Surprisingly, we also observed changes in the Spike (i.e., H69 E484, N501, H655) corresponding to mutations identified in emerging SARS-CoV-2 variants indicating that they can arise in vitro in the absence of immune selection. This study illustrates SARS-CoV-2 genome plasticity and offers new perspectives on surveillance of viral variants. One Sentence SummarySARS-CoV-2 drug resistance & genome plasticity

microbiology↗

bioRxiv2019

TRIM69 inhibits Vesicular Stomatitis Indiana Virus (VSIV)

Vesicular Stomatitis Indiana Virus (VSIV) is a model virus that is exceptionally sensitive to the inhibitory action of interferons. Interferons induce an antiviral state by stimulating the expression of hundreds of interferon stimulated genes (ISGs). These ISGs constrain viral replication, limit tissue tropism, reduce pathogenicity and inhibit viral transmission. Because VSIV is used as a backbone for multiple oncolytic and vaccine strategies, understanding how ISGs restrict VSIV, not only helps in understanding VSIV-pathogenesis, but helps evaluate and understand the safety and efficacy of VSIV-based therapies. Thus there is a need to identify and characterize the ISGs that possess anti-VSIV activity. Using arrayed ISG expression screening, we identified TRIM69 as an ISG that potently inhibits VSIV. This inhibition was highly specific as multiple viruses (including influenza A virus, HIV-1, Rift Valley Fever Virus and dengue virus) were not affected by TRIM69. Indeed, just one amino acid substitution in VSIV can govern sensitivity/resistance to TRIM69. TRIM69 is highly divergent in human populations and exhibits signatures of positive selection that are consistent with this gene playing a key role in antiviral immunity. We propose that TRIM69 is an IFN-induced inhibitor of VSIV and speculate that TRIM69 could be important in limiting VSIV pathogenesis and might influence the specificity and/or efficacy of vesiculovirus-based therapies.\n\nIMPORTANCEVesicular Stomatitis Indiana Virus (VSIV) is a veterinary pathogen that is also used as a backbone for many oncolytic and vaccine strategies. In natural and therapeutic settings, VSIV infection is sensed by the host and host-cells make proteins that protect them from viruses. In the case of VSIV, these antiviral proteins constrain viral replication and protect most healthy tissues from virus infection. In order to understand how VSIV causes disease and how healthy tissues are protected from VSIV-based therapies, it is crucial that we identify the proteins that inhibit VSIV. Here we show that TRIM69 is an antiviral defence that can potently and specifically block VSIV infection.

microbiology↗

bioRxiv2019

Segment 2 from influenza A(H1N1)pdm09 viruses confers temperature sensitive HA yield on candidate vaccine virus growth in eggs that is complemented by PB2 701D

Candidate vaccine viruses (CVVs) for seasonal influenza A virus are made by reassortment of the antigenic virus with a high-yielding egg-adapted strain, typically A/Puerto Rico/8/34 (PR8). Many 2009 H1N1 pandemic (pdm09) high-growth reassortants (HGRs) selected by this process contain pdm09 segment 2 in addition to the antigenic genes. To investigate this, we made CVV mimics by reverse genetics (RG) that were either 6:2 or 5:3 reassortants between PR8 and two pdm09 strains, A/California/7/2009 (Cal7) and A/England/195/2009, differing in the source of segment 2. The 5:3 viruses replicated better in MDCK-SIAT1 cells than the 6:2 viruses, but the 6:2 CVVs gave higher HA antigen yields from eggs. This unexpected phenomenon reflected temperature sensitivity conferred by pdm09 segment 2, as HA yields from eggs for the 5:3 viruses improved substantially when viruses were grown at 35{degrees}C compared with 37.5{degrees}C, whereas 6:2 virus yield did not. Authentic 5:3 pdm09 HGRs, X-179A and X-181, were not markedly temperature-sensitive however, despite their PB1 sequences being identical to that of Cal7, suggestive of compensatory mutations elsewhere in the genome. Sequence comparisons of the PR8-derived backbone genes identified single changes in PB2 and NP, 5 in NS1, and 1 in NS2. PB2 N701D but not NP T130A affected the temperature dependency of viral transcription. Furthermore, introducing the PB2 701D change into a 5:3 CVV mimic improved and drastically reduced the temperature sensitivity of HA yield. We conclude that RG PR8 backbones used for vaccine manufacture in eggs should contain PB2 701D to maximise virus yield.

microbiology↗

bioRxiv2018

Mutation of influenza A virus PA-X decreases pathogenicity in chicken embryos and can increase the yield of reassortant candidate vaccine viruses

The PA-X protein of influenza A virus has roles in host cell shut-off and viral pathogenesis. While most strains are predicted to encode PA-X, strain-dependent variations in activity have been noted. We found that PA-X protein from A/PR/8/34 (PR8) strain had significantly lower repressive activity against cellular gene expression compared with PA-Xs from the avian strains A/turkey/England/50-92/91 (H5N1) (T/E) and A/chicken/Rostock/34 (H7N1). Loss of normal PA-X expression, either by mutation of the frameshift site or by truncating the X-ORF, had little effect on the infectious virus titre of PR8 or PR8 7:1 reassortants with T/E segment 3 grown in embryonated hens eggs. However, in both virus backgrounds, mutation of PA-X led to decreased embryo mortality and lower overall pathology; effects that were more pronounced in the PR8 strain than the T/E reassortant, despite the low shut-off activity of the PR8 PA-X. Purified PA-X mutant virus particles displayed an increased ratio of HA to NP and M1 compared to their WT counterparts, suggesting altered virion composition. When the PA-X gene was mutated in the background of poorly growing PR8 6:2 vaccine reassortant analogues containing the HA and NA segments from H1N1 2009 pandemic viruses or an avian H7N3 strain, HA yield increased up to 2-fold. This suggests that the PR8 PA-X protein may harbour a function unrelated to host cell shut-off and that disruption of the PA-X gene has the potential to improve the HA yield of vaccine viruses.\n\nIMPORTANCEInfluenza A virus is a widespread pathogen that affects both man and a variety of animal species, causing regular epidemics and sporadic pandemics with major public health and economic consequences. A better understanding of virus biology is therefore important. The primary control measure is vaccination, which for humans, mostly relies on antigens produced in eggs from PR8-based viruses bearing the glycoprotein genes of interest. However, not all reassortants replicate well enough to supply sufficient virus antigen for demand. The significance of our research lies in identifying that mutation of the PA-X gene in the PR8 strain of virus can improve antigen yield, potentially by decreasing the pathogenicity of the virus in embryonated eggs.

microbiology↗