Biology subjects

Brown, M. D.

Publications and source records attributed to Brown, M. D..

3 recordsLinked to original sources

bioRxiv2025

Genetic reassortment and diversification of host specificity have driven evolutionary trajectories of lineages of panzootic H5N1 influenza

Since 2021, subclade 2.3.4.4b A(H5N1) high pathogenicity avian influenza (HPAI) viruses have undergone changes in ecology and epidemiology, causing a panzootic of unprecedented scale in wild and domestic birds with spill-over infections and perceptible transmission in a range of mammalian species, raising concern over zoonotic potential. HPAI viruses readily exchange gene segments with low pathogenicity avian influenza viruses via reassortment, a mechanism that facilitates pronounced phenotypic change. Observations suggest changes in the seasonality and host range of panzootic viruses, however, data on the role of reassortment in determining such features are limited. Using phylodynamic approaches, we describe the emergence of the panzootic lineage and using a novel global genotype classification system we describe the subsequent emergence and global structuring of genotypes generated by reassortment. Focusing on evolutionary dynamics in Europe, we show reassortment has produced high fitness genotypes with enhanced capacity for transmission and further we show such advantages can be host-dependent, contrasting successful generalist genotypes with a specialist lineage (EA-2022-BB) adapted to birds of the order Charadriiformes. Experimental investigation of NS1-mediated shutoff indicates this Charadriiformes-specialist does not inhibit host cellular gene expression and hamper the defences of more typical hosts such as water- and land-fowl. We attribute this primarily to variation at position 127 of the NS1 protein. Our results emphasise that reassortment has driven phenotypic change, affected viral fitness, and caused diversification of host specificity and seasonality. Such factors should be considered in studies that seek to identify drivers of HPAI spread and map spillover risk. Additionally, relaxation of host specialisation, ecological diversification, and potential endemicity in atypical host populations present new reassortment opportunities that could result in further novel phenotypes.

microbiology↗

bioRxiv2025

Influenza A virus polymerase co-opts distinct sets of host proteins for RNA transcription or replication

The influenza A virus polymerase, consisting of a heterotrimer of three viral proteins, carries out both transcription and replication of the viral RNA genome. These distinct activities are regulated by viral proteins that vary in abundance during infection, and by various co-opted host cell proteins, which serve as targets for the development of novel antiviral interventions. However, little is known about which host proteins direct transcription and which replication. In this report, we performed a differential interactome screen to identify host proteins co-opted as either transcription-or replication-specific factors. We found that distinct sets of host proteins interact with the influenza polymerase as it carries out the different activities. We functionally characterised HMGB2 and RUVBL2 as replication-specific cofactors and RPAP2 as a transcription-specific cofactor. Our data demonstrate that comparative proteomics can be used as a targeted approach to uncover virus-host interactions that regulate specific stages of the viral lifecycle.

microbiology↗

bioRxiv2025

Polymerase mutations underlie adaptation of H5N1 influenza virus to dairy cattle and other mammals.

In early 2024, an unprecedented outbreak of H5N1 high pathogenicity avian influenza was detected in dairy cattle in the USA1. As of mid-2025 the epidemic is ongoing, resulting in spillbacks into poultry, wild birds and other mammals including humans2. Here, we present molecular and virological evidence that the cattle B3.13 genotype H5N1 viruses rapidly accumulated adaptations in polymerase genes that enabled better replication in bovine cells and tissues, as well as cells of other mammalian species including humans and pigs. We find evidence of several mammalian adaptations gained early in the evolution of these viruses in cattle including PB2 M631L, which is found in all cattle sequences, and PA K497R, which is found in the majority. Structurally, PB2 M631L maps to the polymerase-ANP32 interface, an essential host factor for viral genome replication. We show that this mutation adapts the polymerase to better interact with bovine ANP32 proteins, particularly ANP32A, and thereby enhances virus replication in bovine mammary systems and primary human airway cultures. Importantly, we show that ongoing evolution during 2024 and 2025 in the PB2 gene, including E627K and a convergently arising D740N substitution, further increase polymerase activity and virus replication in a range of mammalian cells. Thus, the continued circulation of H5N1 in dairy cattle not only allows virus adaption improving replicative ability in cattle, but also increases the risk of zoonotic spillover.

microbiology↗