The team, led by Jinping Dou and Shuang Wei, who contributed equally to the work, with corresponding authors Xingjian Liu and Yinü Li, worked from GETV-BJ0304, an attenuated strain previously isolated by the group. Attenuated strains are attractive backbones for reverse genetics systems because they can be manipulated under less stringent containment considerations while still recapitulating core features of alphavirus biology. Using a seamless cloning method, the researchers assembled the complete viral genome rapidly, avoiding the restriction-site scars and extraneous sequences that plague older ligation-based approaches. Seamless assembly matters in this context because alphavirus genomes are compact and densely packed; even small insertions of nonviral sequence at junction sites can alter replication kinetics and confound downstream experiments.

Getah virus belongs to the Alphavirus genus within the Togaviridae family, a group characterized by a positive-sense, single-stranded RNA genome of roughly 11 to 12 kilobases. The genome is organized into two open reading frames: the nonstructural polyprotein encoded at the 5′ end, which supplies the replication machinery, and the structural polyprotein at the 3′ end, which is translated from a subgenomic RNA. This subgenomic RNA is produced from an internal promoter, conventionally called the 26S subgenomic promoter (26SGP), which drives very high levels of structural protein expression during infection. That architecture creates two natural insertion points for a reporter gene, and each comes with distinct trade-offs that the Beijing team set out to quantify.

The first strategy exploits the 2A self-cleaving peptide, a short sequence, originally described in picornaviruses, that induces ribosomal skipping during translation. When a reporter gene such as enhanced green fluorescent protein (EGFP) is fused to a viral polyprotein through a 2A sequence, the translating ribosome ‘skips’ a peptide bond at the 2A motif, releasing the reporter as a largely separate protein while leaving the viral polyprotein essentially intact. The elegance of this approach is that the reporter is expressed from the same mRNA as the viral protein, so reporter output tracks faithfully with viral gene expression, and the viral genome length increases only modestly. The second strategy inserts an additional copy of the 26S subgenomic promoter upstream of the reporter gene, creating a second subgenomic RNA dedicated to reporter translation. This duplicated-promoter design can drive very high reporter expression, but it adds substantial sequence to the genome and introduces an extra promoter element that the viral replication machinery must recognize and that recombination can act upon.

Which strategy wins has often been assumed rather than tested, particularly for attenuated alphavirus backbones where genomic flexibility may differ from that of virulent laboratory strains. The researchers constructed reporter viruses carrying EGFP through both routes and then subjected the resulting recombinants to a battery of characterization assays. The results were decisive: for the GETV-BJ0304 backbone, the 2A self-cleaving peptide strategy proved highly efficient and stable. The recombinant virus, designated GETV-2A/EGFP, displayed high infection efficiency and, importantly, maintained its reporter over serial passages, a property that many reporter alphaviruses lose as deletion or mutation of the foreign sequence confers a replicative advantage.

Genetic stability is the quiet battleground of reporter virology. A reporter virus that sheds its fluorescent cargo after a few rounds of replication is worse than useless, because it silently biases experiments: the cells that remain fluorescent are those infected by the fittest, reporter-retaining variants, which may not represent the population the researcher intends to study. By demonstrating that GETV-2A/EGFP retains high-level EGFP expression through extended passaging, the study provides a technical platform whose fluorescence can be taken as a reliable proxy for infection. That reliability underpins quantitative applications ranging from neutralization assays and antiviral screening to single-cell analyses of viral spread, where fluorescence intensity and infected-cell counts feed directly into the analysis.

The comparison also carries broader lessons for alphavirus reverse genetics. The 26S promoter duplication strategy, while capable of strong expression, imposes a larger genomic burden and creates duplicated promoter sequences that are intrinsically recombination-prone. In an attenuated backbone, where replication fidelity and genomic tolerance may already be strained, that burden appears to be decisive. The 2A approach, by contrast, keeps the added sequence short and avoids duplicating regulatory elements, aligning reporter expression with the natural translational output of the viral polyprotein. The finding does not necessarily generalize to every alphavirus or every backbone, but it offers an evidence-based default for researchers constructing reporter clones in attenuated strains, replacing intuition with head-to-head data.

Why does Getah virus warrant this level of technical investment? The virus circulates in a transmission cycle involving mosquitoes and vertebrate hosts, and it has caused notable epizootics in horses, characterized by fever, edema, and urticarial rash, as well as reproductive disease and neurological signs in piglets. Although GETV is not currently a major human pathogen, its recent outbreaks and demonstrated potential for increased virulence have placed it alongside other arboviruses as a public-safety concern. Climate change, expanding mosquito vector ranges, and intensification of livestock production all create conditions favorable to emergence. A robust reverse genetics system is the prerequisite for dissecting which viral proteins and RNA elements drive host range, virulence, and transmission, and for rationally designing attenuated vaccine candidates or antiviral targets rather than discovering them by trial and error.

The platform described in the study enables exactly that dissection. With a stable fluorescent reporter embedded in an otherwise authentic viral genome, researchers can monitor replication in real time, quantify infection in the presence of interfering RNAs or candidate drugs, and screen host genes for factors that restrict or support GETV invasion. The authors frame the system as a crucial technical platform for in-depth analysis of GETV replication and pathogenic mechanisms, as well as for exploring new strategies that help the host resist viral invasion. In practical terms, that means the clone can serve as the starting point for mutant libraries, for structure-function studies of the nonstructural proteins, and for testing how specific mutations alter tropism in mosquito and mammalian cells.

The work, funded by China’s National Key Research and Development Program, the National Natural Sciences Foundation of China, the Agricultural Science and Technology Innovation Program, and the Central Public-interest Scientific Institution Basal Research Fund, arrives as an open-access publication, making the construction logic and characterization data available to laboratories worldwide. As arboviruses continue to test the boundaries of veterinary and public health preparedness, tools of this kind, a rapidly assembled infectious clone paired with a validated, stable reporter strategy, convert an emerging pathogen from an opaque threat into an experimentally tractable one. For Getah virus, the 2A-based design now stands as the benchmark against which future reporter constructs will be measured.

Subject of Research: Construction and comparison of reporter gene insertion strategies in Getah virus reverse genetics systems

Article Title: Comparison and characterization of construction strategies for Getah virus infectious clones with stable, high-level expression of reporter gene

Article References: Dou, J., Wei, S., Gao, X., Wu, T., Zhao, Z., Zhang, Z., Liu, X., & Li, Y. (2026). Comparison and characterization of construction strategies for Getah virus infectious clones with stable, high-level expression of reporter gene. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06457-x

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06457-x

Keywords: Getah virus, alphavirus, reverse genetics, infectious clone, reporter gene, EGFP, 2A self-cleaving peptide, subgenomic promoter, arbovirus, genetic stability, viral replication, veterinary virology

The study, published in Virology Journal, focused on Culex pipiens sensu lato and Culiseta annulata, two species that dominate the UK mosquito fauna and are considered among the most plausible vectors should arboviruses such as West Nile or Usutu virus establish local transmission cycles. Between 2021 and 2022, the team collected adult mosquitoes across the grounds of the two zoological collections, sites chosen deliberately because zoos concentrate large numbers of animals in outdoor enclosures where mosquitoes feed readily. That combination of abundant vectors, diverse vertebrate hosts and regular human visitors makes zoological collections potential interfaces for virus exchange between mosquitoes, animals and people, and therefore valuable sentinel locations for surveillance.

In total, 4,042 mosquitoes were processed and sequenced across 44 pools. The researchers extracted total nucleic acids and applied a metagenomic sequencing strategy designed to capture both RNA and DNA viruses, allowing them to recover viral genomes without relying on prior assumptions about which viruses might be present. Bioinformatic assembly and taxonomic classification of the resulting reads yielded 26 viral genomes, a striking haul for a country whose mosquito viromes have remained comparatively understudied. Nine of these represented entirely novel species, distributed across both RNA and DNA virus families, underscoring how much basic viral diversity in northern European mosquitoes still awaits description.

A consistent pattern emerged across the sampling sites: several viruses were detected in every pool analysed, indicating substantial overlap in virome composition between the two zoos. This shared core of viruses suggests that certain mosquito-associated viruses are widespread and stable components of the local mosquito fauna rather than isolated curiosities confined to a single habitat. Such ubiquity matters for risk assessment, because a virus that maintains itself efficiently across geographically separated mosquito populations has, by definition, the ecological flexibility that emergence requires, even if most of these viruses ultimately prove harmless to vertebrates.

The headline findings are two novel orthobunyaviruses, named Atherstone virus and Deva virus, belonging to the family Peribunyaviridae. Orthobunyaviruses are a genus with a serious pedigree: it includes recognised human and animal pathogens such as Schmallenberg virus, which devastated European ruminant farming after its emergence in 2011, and Oropouche virus, a growing public health concern in the Americas. The tripartite RNA genomes of orthobunyaviruses encode a viral RNA-dependent RNA polymerase on the large segment, surface glycoproteins on the medium segment, and nucleoprotein plus accessory proteins on the small segment. Finding two previously unknown members of this genus in British mosquitoes immediately elevates them to candidates for closer scrutiny.

Not all orthobunyaviruses pose equal risk, and the study went beyond simple detection to ask which of the two new viruses resembles a genuine arbovirus, capable of replicating in both mosquitoes and vertebrate hosts. The team employed MosViR, a machine-learning classification tool trained on known mosquito viruses to predict whether a given virus is likely to be mosquito-restricted or arthropod-borne. For Atherstone virus, detected at both zoos, the prediction pointed towards arbovirus status, a result that alone would justify follow-up. More compelling still was the genomic evidence: Atherstone virus carries an open reading frame encoding a non-structural protein S, or NSs, a well-characterised virulence factor in orthobunyaviruses that antagonises host antiviral responses, including the interferon system, and is a hallmark of pathogenic members of the genus.

Deva virus tells a different story. Its small segment lacks an NSs open reading frame altogether, and MosViR did not predict it to be an arbovirus. The absence of NSs, combined with the absence of a vertebrate-infecting signature, is consistent with Deva virus being an insect-specific virus, locked into replication within mosquito cells and their close relatives. Insect-specific viruses of this kind are increasingly recognised as common and sometimes abundant residents of mosquito viromes. Although they do not infect vertebrates directly, they are far from biologically irrelevant: they can modulate mosquito immunity, compete with arboviruses for cellular resources, and in some cases reduce the ability of mosquitoes to transmit pathogenic viruses, making them subjects of interest both for basic virology and for potential interference-based control strategies.

The broader viral inventory recovered in the study reinforces this picture of a layered virome. Alongside the orthobunyaviruses, the sequencing identified viruses spanning multiple families, including flavivirus-like and other RNA virus groups as well as DNA viruses, with several classified as novel species. Distinguishing arboviruses from insect-specific viruses is one of the central analytical challenges in mosquito metagenomics, because both can be present in the same sample and their genomes can be difficult to interpret from sequence data alone. Tools such as MosViR, combined with comparative genomics against reference databases and catalogues of known arboviruses, provide a probabilistic framework for triage, flagging which discoveries warrant experimental characterisation in cell culture and vertebrate systems and which can be provisionally set aside as likely insect-restricted.

Why does this matter for the United Kingdom specifically? The country sits at the northern edge of the range of many mosquito species, and climate warming, changes in land use and the movement of animals and goods are all expected to alter the dynamics of mosquito-borne disease in temperate Europe. Usutu virus has already established itself in British birds and mosquitoes, and West Nile virus circulates periodically in neighbouring countries. Risk frameworks built around these known threats are essential, but the new study argues that they should be complemented by surveillance for the unknown: viruses already resident in local vectors whose properties have never been tested. A virus that today appears to be insect-specific could, through reassortment with a related pathogen or through evolutionary change, acquire new capabilities. Orthobunyaviruses are particularly notable in this respect because their segmented genomes can reassort when mosquitoes are co-infected with related viruses, generating novel combinations with unpredictable host ranges.

The authors are careful not to overstate the immediate danger. Detection of a viral genome in a mosquito does not demonstrate that the virus infects or harms vertebrates, and neither Atherstone nor Deva virus has been shown to cause disease. What the study provides is a prioritised list of candidates and a demonstration of method: that large-scale metagenomic surveillance of UK mosquitoes is feasible, productive and capable of revealing both the diversity of local viromes and the specific viruses that merit laboratory follow-up. Isolation of Atherstone virus, characterisation of its host range, and serological surveys of animals and humans near the sampling sites would be the logical next steps. In the meantime, the work adds the United Kingdom to the growing map of regions where the viruses closest to home, rather than those arriving from abroad, are proving to be the first order of business for emerging infection surveillance.

Subject of Research: Metagenomic surveillance of mosquito viromes at two UK zoos reveals novel mosquito-associated orthobunyaviruses

Article Title: Emergence risks from within? Metagenomic analysis of mosquito viromes from two zoos reveals mosquito-associated orthobunyaviruses in the UK

Article References: Pilgrim, J., Seechurn, N., Cunningham-Oakes, E., Gillespie, L., Dobbs, P., Lopez, J., Kohl, A., Hughes, G. L., Blagrove, M. S. C., Baylis, M., & Darby, A. C. (2026). Emergence risks from within? Metagenomic analysis of mosquito viromes from two zoos reveals mosquito-associated orthobunyaviruses in the UK. Virology Journal. https://doi.org/10.1186/s12985-026-03305-z

Image Credits: AI Generated

DOI: 10.1186/s12985-026-03305-z

Keywords: orthobunyavirus, mosquito, virome, metagenomics, arbovirus, Culex pipiens, Culiseta annulata, surveillance, zoonotic risk, insect-specific virus, United Kingdom, Peribunyaviridae