Emergence of Getah Virus Infection in Horse With Fever in China, 2018

Rapid Detection of Getah Virus Antibodies in Horses Using a Recombinant E2 Protein-Based Immunochromatographic Strip

The prevalence and impact of Getah virus (GETV) are significant concerns in China. GETV can infect a wide range of animals, including horses, pigs, sheep, cattle, birds, and humans, resulting in substantial losses in the livestock and agricultural industries. GETV infection can cause the development of ulcers and inflammation in the mouth and gums of horses, which result in pain and discomfort and lead to symptoms such as reduced appetite, drooling, and difficulty chewing. As a result, there is a pressing need for efficient and rapid disease diagnosis methods. However, the currently available diagnostic methods have limitations in terms of operational time, equipment, and the experience of the individuals using them. In this study, a rapid, specific, and sensitive detection method was developed using a colloidal gold-based immunochromatographic strip (ICS) for the detection of antibodies against GETV in horses. To prepare the ICS, the antigen domain of the E2 glycoprotein of GETV was expressed using the Escherichia coli expression system after analysis with DNAstar v7.1 software. The nitrocellulose membrane was coated with rE2 protein or SPA to form the test line and control line, respectively. After optimizing the reaction conditions, the sensitivity, specificity, and repeatability of the strip were verified. The results showed that the test strip had a detection limit of up to 1:320 dilutions for GETV-positive serum, with no cross-reactivity observed with other equine-susceptible pathogens such as equine arteritis virus (EAV), equine herpesvirus-1 (EHV-I), equine infectious anemia virus (EIAV), equine influenza virus (EIV), African horse sickness virus (AHSV), and Japanese encephalitis virus (JEV). Furthermore, the ICS exhibited a concordance rate of 94.0% when testing 182 clinical serum samples compared to the virus neutralization test. Overall, this ICS diagnosis method will be an effective tool for the rapid detection of GETV in the field.

Emergence of a novel GIII Getah virus variant in pigs in Guangdong, China, 2023

From May to July of 2023, one pig farm in Heyuan city, Guangdong Province of China, suffered severe piglet death and sow reproductive disorders. The common pig viruses and bacteria tested negative. To uncover the possible cause of the disease, a metagenomic analysis was performed in the pooled small intestine samples from three 8-day-old diseased piglets. The results showed that Getah virus (GETV), an RNA virus, might be the potential pathogen that affects pig health. Subsequently, GETV nucleotide was detected in all of the 15 samples collected from three diseased piglets using quantitative reverse transcription PCR, suggesting GETV as the main pathogen of the disease. A GETV strain, designated as GDHYLC23, was successfully isolated using the swine testicle cell line. Sequence analysis showed that the epidemic strain had a unique 32-nucleotide repeat insertion in the 3' noncoding region. Phylogenetic analysis showed that GDHYLC23 belonged to the pandemic group III. The identification of GETV with new variations implies the continuous evolution of the virus, which poses potential threats to the swine industry.IMPORTANCEPig farms are faced with emerging and re-emerging viruses that may cause substantial economic loss. The identification of potentially pathogenic viruses helps to prevent and control the spread of diseases. In this study, by using metagenomic analysis, we found that a neglected virus, GETV with a unique insertion in the genome, was the main pathogen in one pig farm that suffered severe piglet death and sow reproductive disorders. Although the potential impact of such an insertion on viral pathogenicity is unknown, the surveillance of the continuing evolution of GETV in pig farms cannot be ignored.

A recombinant Getah Virus expressing a GFP gene for rapid neutralization testing and antiviral drug screening assay

Getah virus (GETV) is a re-emerging mosquito-borne RNA virus that induces fever, hind limb edema, swollen submandibular lymph nodes, and urticaria in horses. In pigs, the virus often results in stillbirths among pregnant sows, and neurological symptoms leading to death in piglets. Currently, there are no specific treatments or drugs available for GETV infection. The use of reporter viruses to monitor viral replication and spread in real-time within infected cells and animals provides a powerful tool for targeting antiviral drugs throughout the viral life cycle. Their fluorescence-tracked characteristics greatly facilitate virus neutralization tests (VNTs). In this study, we engineered two recombinant viruses by inserting different reporter protein genes at the 3' end of the structural protein gene, an unreported location that can accommodate exogenous genes. The rGEEiLOV and rGEEGFP viruses demonstrated genetic stability for at least five passages and replicated at a rate similar to that of the parental virus in BHK-21 cells. The rGEEGFP virus facilitated viral neutralization testing. Additionally, we used the reporter virus rGEEGFP to confirm ivermectin, a broad-spectrum antiparasitic agent, as a potential inhibitor of GETV in vitro. Ivermectin appears to inhibit the early replication stages of the virus and can block cell-to-cell viral transmission. In conclusion, rGEEGFP holds significant potential for antiviral screening to identify specific inhibitors against GETV and for use in viral neutralization tests.

Infectivity and pathogenesis characterization of getah virus (GETV) strain via different inoculation routes in mice

In recent years, the epidemiological profile of Getah virus (GETV) has become increasingly serious, posing a huge threat to animal and public health in China. GETV can cause multi-species infection, including horses, pigs, rats, cattle, kangaroos, reptiles and birds. However, there were few reports on the efficiency of the virus entering the host via routes of different systems. In the present study, a GETV strain (SC201807) was obtained from a piglet's blood in 2018 in Sichuan, China. First, we established a quantitative real-time polymerase chain reaction (qRT-PCR) SYBR assay specific to GETV. Then, we evaluated the infection efficiency of different routes using mouse animal model. 108 male mice were randomly divided into four groups as follows: intramuscular, intraoral and intranasal infection routes, and negative control. All mice in the experimental group were inoculated with 4 × 102.85 TCID50 GETV virus. Tissue tropism experiments show that GETV has a wide range of tissue distribution, and intramuscular infection is the first to infect all tissues of the body, and suggest that oral infection may be a new GETV transmission route. Histopathological examination results showed that intramuscular injection of GETV mainly caused different degrees of pathological damage to the tissues, and could rapidly induce a large amount of inflammatory regulatory factors such as IL-6 and TNF-α. Our data may help us to evaluate the risk of transmission of Porcine Getah virus and provide an experimental basis for the prevention and control of Porcine Getah virus.

Development and application of a colloidal-gold immunochromatographic strip for detecting Getah virus antibodies

Getah virus (GETV) is a re-emerging mosquito-borne alphavirus that is highly pathogenic, mainly to pigs and horses. There are no vaccines or treatments available for GETV in swine in China. Therefore, the development of a simple, rapid, specific, and sensitive serological assay for GETV antibodies is essential for the prevention and control of GETV. Current antibody monitoring methods are time-consuming, expensive, and dependent on specialized instrumentation, and these features are not conducive to rapid detection in clinical samples. To address these problem, we developed immunochromatographic test strips (ICTS) using eukaryotically expressed soluble recombinant p62-E1 protein of GETV as a labelled antigen, which has good detection sensitivity and no cross-reactivity with other common porcine virus-positive sera. The ICTS is highly compatible with IFA and ELISA and can be stored for 1 month at 37 °C and for at least 3 months at room temperature. Hence, p62-E1-based ICTS is a rapid, accurate, and convenient method for rapid on-site detection of GETV antibodies. KEY POINTS: • We established a rapid antibody detection method that can monitor GETV infection • We developed colloidal gold test strips with high sensitivity and specificity • The development of colloidal gold test strips will aid in the field serologic detection of GETV.

GETV nsP2 plays a critical role in the interferon antagonism and viral pathogenesis

Getah virus (GETV) was becoming more serious and posing a potential threat to animal safety and public health. Currently, there is limited comprehension regarding the pathogenesis and immune evasion mechanisms employed by GETV. Our study reveals that GETV infection exhibits the capacity for interferon antagonism. Specifically, the nonstructural protein nsP2 of GETV plays a crucial role in evading the host immune response. GETV nsP2 effectively inhibits the induction of IFN-β by blocking the phosphorylation and nuclear translocation of IRF3. Additionally, GETV nsP2 hinders the phosphorylation of STAT1 and its nuclear accumulation, leading to significantly impaired JAK-STAT signaling. Furthermore, the amino acids K648 and R649, situated in the C-terminal region of GETV nsP2, play a crucial role in facilitating nuclear localization. Not only do they affect the interference of nsP2 with the innate immune response, but they also exert an influence on the pathogenicity of GETV in mice. In summary, our study reveals novel mechanisms by which GETV evades the immune system, thereby offering a foundation for comprehending the pathogenic nature of GETV. Video Abstract.

Seroepidemiological investigation of Getah virus in the China-Myanmar border area from 2022-2023

Getah Virus (GETV) is an RNA virus that is transmitted by mosquitoes and can cause disease or death in a variety of vertebrates. Its prevalence is increasingly severe in Asia. This study conducted a GETV epidemiological investigation on 1,300 bovine sera collected in the Honghe Prefecture of Yunnan Province on the China-Myanmar border from 2022 to 2023. The positive rate of GETV antibodies in bovine serum in Honghe Prefecture was determined to be 20.25% through indirect Enzyme-linked immunosorbent test (ELISA) methods. Using Real-time PCR methods to detect GETV RNA in bovine serum, the positive rate was 0.23% (3/1300), and viral nucleic acids were only detected in three bovine sera in Jianshui area in 2022. The YN2305 strain was successfully isolated from mouse neuroblastoma (N2a) cells and the complete gene sequence was obtained. All the above results indicate the existence of GETV infection in cattle in Honghe Prefecture, Yunnan Province. Homology and genetic evolution analysis found that the isolated strain has a high homology with the JL1808 strain isolated from cattle in 2018, with a nucleotide identity of 100%, and a nucleotide identity of 99.8% with the SD17-09 strain isolated from foxes in 2017. Compared with the nucleotides of 44 virus strains published in Genbank, YN2305 has multiple nucleotide site mutations in the structural gene E2 and non-structural gene NS. The nucleotide and amino acid identity of the E2 gene are 94.2-100% and 96.4-100%, respectively. Genetic evolution analysis found that this virus strain is most closely related to the bovine origin JL1808, and it is in gene group III with HuN1, Kochi-01, SD17-09, MI-110-C1, and MI-110-C2 strains that causes significant clinical symptoms in Chinese pig, fox and horse populations, belonging to the same evolutionary branch. This study determined the infection rate, genotype, and main prevalence areas of GETV in bovine sera in the China-Myanmar border area. Therefore, the epidemiological investigation of GETV infection in multiple animal hosts should be further expanded, and research on its pathogenicity and vectors should be carried out.

The roles of 6K protein on Getah virus replication and pathogenicity

Alphavirus is a type of arbovirus that can infect both humans and animals. The amino acid sequence of the 6K protein, being one of the structural proteins of the alphavirus, is not conserved. Deletion of this protein will result in varying effects on different alphaviruses. Our study focuses on the function of the Getah virus (GETV) 6K protein in infected cells and mice. We successfully constructed infectious clone plasmids and created resulting viruses (rGETV and rGETV-Δ6K). Our comprehensive microscopic analysis revealed that the 6 K protein mainly stays in the endoplasmic reticulum. In addition, rGETV-Δ6K has lower thermal stability and sensitivity to temperature than GETV. Although the deletion of the 6K protein does not reduce virion production in ST cells, it affects the release of virions from host cells by inhibiting the process of E2 protein transportation to the plasma membrane. Subsequent in vivo testing demonstrated that neonatal mice infected with rGETV-Δ6K had a lower virus content, less significant pathological changes in tissue slices, and milder disease than those infected with the wild-type virus. Our results indicate that the 6K protein effectively reduces the viral titer by influencing the release of viral particles. Furthermore, the 6K protein play a role in the clinical manifestation of GETV disease.

Transcriptome screening identifies TIPARP as an antiviral host factor against the Getah virus

IMPORTANCE

Alphaviruses threaten public health continuously, and Getah virus (GETV) is a re-emerging alphavirus that can potentially infect humans. Approved antiviral drugs and vaccines against alphaviruses are few available, but several host antiviral factors have been reported. Here, we used GETV as a model of alphaviruses to screen for additional host factors. Tetrachlorodibenzo-p-dioxin-inducible poly(ADP ribose) polymerase was identified to inhibit GETV replication by inducing ubiquitination of the glycoprotein E2, causing its degradation by recruiting the E3 ubiquitin ligase membrane-associated RING-CH8 (MARCH8). Using GETV as a model virus, focusing on the relationship between viral structural proteins and host factors to screen antiviral host factors provides new insights for antiviral studies on alphaviruses.

The Isolation and Characterization of a Novel Group III-Classified Getah Virus from a Commercial Modified Live Vaccine against PRRSV

As an epizootic causative agent, the Getah virus (GETV) can cause moderate illness in horses, lethal disease in foxes, and reproductive disorders and fetal death in pigs. Due to the wide range of hosts and multiple routes of transmission, GETV has become a growing potential threat to the global livestock industry, and even to public health. More attention and research on GETV are urgently needed. In this study, we successfully isolated a novel GETV strain, named BJ0304, from a commercial live vaccine against porcine reproductive and respiratory syndrome virus (PRRSV) and determined its growth kinetics. Then, genetic and phylogenetic analyses were performed. The results revealed that BJ0304 was clustered into Group III, and it was most related to the GETV-V1 strain based on the complete genome sequence. Furthermore, the pathogenicity of the isolate was assessed and found to be a low virulent strain in mice relative to its closest homolog GETV-V1. Finally, mutation and glycosylation analysis showed that a unique mutation (171 T > I) at one amino acid of E2, which affected the glycosylation of E2, may be associated with viral pathogenicity. In summary, the general characteristic of a novel Group III-classified GETV-BJ0304 isolated from commercial live PRRSV vaccine was defined and then mutation/glycosylation-related potential virulence factor was discussed. This study highlights the complexity of GETV transmission routes in swine and the need for more surveillance on commercial animal vaccines, contributes to the understanding of genetic characterization of clinical isolates, provides possible virulence factors in favor of unveiling the viral pathogenesis, and eventually lays the foundation for the prevention and control of GETV.

Evolutionary characterization and pathogenicity of Getah virus from pigs in Guangdong Province of China

Getah virus (GETV) is an emerging zoonotic virus that can infect humans and many mammals through mosquitoes. In this study, a novel pathogenic GETV strain, GDQY2022, was isolated from a pig farm in Guangdong Province, China. Sequence comparisons and phylogenetic analysis showed that GDQY2022 belongs to group III (GIII) and was most closely related to strain HeN202009-2, with 99.78% nucleotide sequence identity. Histopathological examination revealed significant pathological changes, such as widened alveolar septum in the lungs with mild congestion and hemorrhage. Differences in viral load between tissues were assessed by real-time RT-PCR, and significantly higher levels of GETV were found in abdominal lymph nodes and lungs of subclinically and clinically affected pigs (P < 0.01). This study provides valuable data for understanding the risk of GETV infection in the pig industry and a reliable basis for studying the pathogenic mechanisms and diagnostic surveillance of GETV.

The host transcriptome change involved in the inhibitory effect of exogenous interferon-γ on Getah virus replication

Introduction

Getah virus (GETV) has become a growing potential threat to the global livestock industry and public health. However, little is known about the viral pathogenesis and immune escape mechanisms, leading to ineffective control measures.

Methods

In this study, the antiviral activity of exogenous interferons (IFNs) was assessed by using western blotting (WB), real-time quantitative PCR (RT-qPCR) and indirect immunofluorescence assay (IFA). The comparative transcriptomics among mock- and GETV-infected (MOI = 0.1) ST cells with or without IFN-γ was performed by RNA-seq, and then the transcriptome profiling of GETV-infected ST cells and key pathways and putative factors involved in inhibitory effect of IFN-γ on GETV replication were analyzed by bioinformatics methods and RT-qPCR.

Results

The results showed that treatment with IFN-γ could suppress GETV replication, and the inhibitory effect lasted for at least 48 h, while the exogenous IFN-α/ω and IFN-λ3 treatments failed to inhibit the viral infection and early replication in vitro. Furthermore, the blueprint of virus-host interaction was plotted by RNA-seq and RT-qPCR, showing systemic activation of inflammatory, apoptotic, and antiviral pathways in response to GETV infection, indicating viral hijacking and inhibition of innate host immunity such as IFN-I/III responses. Last and most importantly, activation of the JAK-STAT signaling pathway and complement and coagulation cascades may be a primary driver for IFN-γ-mediated inhibition of GETV replication.

Discussion

These findings revealed that GETV possessed the capability of viral immune escape and indicated that IFN-γ aided in the prevention and control of GETV, implying the potential molecular mechanism of suppression of GETV by IFN-γ, all of which warrant emphasis or further clarification.

Development of a recombinant reporter Getah virus for antiviral drug screening assays

Getah virus (GETV), is an often neglected and re-emerging mosquito-borne RNA virus. GETV can cause illness accompanied with high fever, rash, incapacitating arthralgia and chronic arthritis or encephalitic disease in affected animals. Currently, there is no specific treatment or vaccine against GETV infection. In this study, we developed three recombinant viruses by inserting different reporter protein genes between the Cap and pE2 genes. The reporter viruses exhibited high replication capacity similar to the parental virus. The rGECiLOV and rGECGFP viruses were genetically stable within at least ten rounds of passages in BHK-21 cells. We confirmed that the reporter virus, rGECGFP, facilitated the antiviral assays against GETV by testing it with the known inhibitor, ribavirin. It was also found that the compound, doxycycline, showed an inhibitory effect on GETV replication. In addition, rGECGFP was found to be an authentic mimic of the parental virus infection in 3-day-old mice, but with milder pathogenicity. The reporter viruses will contribute to the assessment of viral replication and proliferation, tracking and elucidating of alphavirus-host interactions. In addition, they will help in the screening of potential antiviral compounds.

Evaluating the mosquito host range of Getah virus and the vector competence of selected medically important mosquitoes in Getah virus transmission

BACKGROUND

The Getah virus (GETV) is a mosquito-borne Alphavirus (family Togaviridae) that is of significant importance in veterinary medicine. It has been associated with major polyarthritis outbreaks in animals, but there are insufficient data on its clinical symptoms in humans. Serological evidence of GETV exposure and the risk of zoonotic transmission makes GETV a potentially medically relevant arbovirus. However, minimal emphasis has been placed on investigating GETV vector transmission, which limits current knowledge of the factors facilitating the spread and outbreaks of GETV.

METHODS

To examine the range of the mosquito hosts of GETV, we selected medically important mosquitoes, assessed them in vitro and in vivo and determined their relative competence in virus transmission. The susceptibility and growth kinetics of GETVs in various mosquito-derived cell lines were also determined and quantified using plaque assays. Vector competency assays were also conducted, and quantitative reverse transcription-PCR and plaque assays were used to determine the susceptibility and transmission capacity of each mosquito species evaluated in this study.

RESULTS

GETV infection in all of the investigated mosquito cell lines resulted in detectable cytopathic effects. GETV reproduced the fastest in Culex tritaeniorhynchus- and Aedes albopictus-derived cell lines, as evidenced by the highest exponential titers we observed. Regarding viral RNA copy numbers, mosquito susceptibility to infection, spread, and transmission varied significantly between species. The highest vector competency indices for infection, dissemination and transmission were obtained for Cx. tritaeniorhynchus. This is the first study to investigate the ability of Ae. albopictus and Anopheles stephensi to transmit GETV, and the results emphasize the role and capacity of other mosquito species to transmit GETV upon exposure to GETV, in addition to the perceived vectors from which GETV has been isolated in nature.

CONCLUSIONS

This study highlights the importance of GETV vector competency studies to determine all possible transmission vectors, especially in endemic regions.

Early Genomic Surveillance and Phylogeographic Analysis of Getah Virus, a Reemerging Arbovirus, in Livestock in China

Getah virus (GETV) mainly causes disease in livestock and may pose an epidemic risk due to its expanding host range and the potential of long-distance dispersal through animal trade. Here, we used metagenomic next-generation sequencing (mNGS) to identify GETV as the pathogen responsible for reemerging swine disease in China and subsequently estimated key epidemiological parameters using phylodynamic and spatially-explicit phylogeographic approaches. The GETV isolates were able to replicate in a variety of cell lines, including human cells, and showed high pathogenicity in a mouse model, suggesting the potential for more mammal hosts. We obtained 16 complete genomes and 79 E2 gene sequences from viral strains collected in China from 2016 to 2021 through large-scale surveillance among livestock, pets, and mosquitoes. Our phylogenetic analysis revealed that three major GETV lineages are responsible for the current epidemic in livestock in China. We identified three potential positively selected sites and mutations of interest in E2, which may impact the transmissibility and pathogenicity of the virus. Phylodynamic inference of the GETV demographic dynamics identified an association between livestock meat consumption and the evolution of viral genetic diversity. Finally, phylogeographic reconstruction of GETV dispersal indicated that the sampled lineages have preferentially circulated within areas associated with relatively higher mean annual temperature and pig population density. Our results highlight the importance of continuous surveillance of GETV among livestock in southern Chinese regions associated with relatively high temperatures. IMPORTANCE Although livestock is known to be the primary reservoir of Getah virus (GETV) in Asian countries, where identification is largely based on serology, the evolutionary history and spatial epidemiology of GETV in these regions remain largely unknown. Through our sequencing efforts, we provided robust support for lineage delineation of GETV and identified three major lineages that are responsible for the current epidemic in livestock in China. We further analyzed genomic and epidemiological data to reconstruct the recent demographic and dispersal history of GETV in domestic animals in China and to explore the impact of environmental factors on its genetic diversity and its diffusion. Notably, except for livestock meat consumption, other pig-related factors such as the evolution of live pig transport and pork production do not show a significant association with the evolution of viral genetic diversity, pointing out that further studies should investigate the potential contribution of other host species to the GETV outbreak. Our analysis of GETV demonstrates the need for wider animal species surveillance and provides a baseline for future studies of the molecular epidemiology and early warning of emerging arboviruses in China.

Development and application of an indirect ELISA for detecting equine IgG antibodies against Getah virus with recombinant E2 domain protein

Getah virus (GETV) disease is a mosquito-borne infectious disease that causes fever, aseptic meningitis, and abortion in a variety of animals. Currently, the epidemic trend of GETV disease increases seriously worldwide, especially in China, posing a potential threat to animal safety and public health. However, there are few reports about the epidemiological investigation of GETV disease in China as well as a lack of commercial diagnostic kit for GETV antibody. Therefore, the establishment of a rapid, sensitive and suitable GETV antibody detection method for large-scale samples is an urgent request to fully understand the prevalence of GETV disease. Here, a recombinant plasmid pET22b-GETV-E2d that contained the domain of GETV-E2 (E2d) fused to His-tag was constructed to express recombinant protein E2d (rE2d) in Escherichia coli. The rE2d was mainly expressed in inclusion bodies. And it was purified successfully by nickel affinity column so that it could be used to develop an indirect ELISA (rE2d-ELISA). After optimizing reaction conditions of rE2d-ELISA, the cut-off value was determined as 0.396 with 100 equine sera tested by virus neutralization test (VNT). Furthermore, rE2d-ELISA method showed the positive rate of IgG antibodies against GETV was 54.3% based on testing 646 clinical serum samples obtained in Xinjiang whereas the overall coincidence rate between rE2d-ELISA and VNT was 94.0%, with 98.2% sensitivity and 92.6% specificity. The findings suggest that the developed IgG ELISA employing recombinant E2d promises was an efficient and low-cost type of antibody detection method for horse, which will benefit for prevention of GETV outbreaks in horses.

Establishment of a reverse transcription real-time quantitative PCR method for Getah virus detection and its application for epidemiological investigation in Shandong, China

Getah virus (GETV) is a mosquito-borne, single-stranded, positive-sense RNA virus belonging to the genus Alphavirus of the family Togaviridae. Natural infections of GETV have been identified in a variety of vertebrate species, with pathogenicity mainly in swine, horses, bovines, and foxes. The increasing spectrum of infection and the characteristic causing abortions in pregnant animals pose a serious threat to public health and the livestock economy. Therefore, there is an urgent need to establish a method that can be used for epidemiological investigation in multiple animals. In this study, a real-time reverse transcription fluorescent quantitative PCR (RT-qPCR) method combined with plaque assay was established for GETV with specific primers designed for the highly conserved region of GETV Nsp1 gene. The results showed that after optimizing the condition of RT-qPCR reaction, the minimum detection limit of the assay established in this study was 7.73 PFU/mL, and there was a good linear relationship between viral load and Cq value with a correlation coefficient (R²) of 0.998. Moreover, the method has good specificity, sensitivity, and repeatability. The established RT-qPCR is 100-fold more sensitive than the conventional RT-PCR. The best cutoff value for the method was determined to be 37.59 by receiver operating characteristic (ROC) curve analysis. The area under the curve (AUC) was 0.956. Meanwhile, we collected 2,847 serum specimens from swine, horses, bovines, sheep, and 17,080 mosquito specimens in Shandong Province in 2022. The positive detection rates by RT-qPCR were 1%, 1%, 0.2%, 0%, and 3%, respectively. In conclusion, the method was used for epidemiological investigation, which has extensive application prospects.

Getah Virus (Alphavirus): An Emerging, Spreading Zoonotic Virus

Getah virus (GETV) is a zoonotic virus transmitted by mosquitoes, belonging to the Togaviridae family, Alphavirus genus. It was first isolated from mosquitoes in Malaysia in 1955, being widespread in island countries in the South Pacific region. Since the beginning of the 21st century, GETV expanded its range and geographical distribution from low-latitude tropical regions to 60° north latitude, being isolated from 17 different species of mosquitoes belonging to five genera of Culicidae (Culex, Anopheles, Armigeres, Aedes and Mansonia), as well as from midges in Eurasia. Molecular genetic evolution analysis revealed large molecular differences between the mosquitoes currently circulating Eurasia and those in the South Pacific in 1950s. The number of disease outbreaks caused by GETV in animals is increasing alongside the types of animals infected, from horses and pigs to cattle, blue foxes and red pandas. The disease burden is severely underestimated, and the economic cost to livestock production remains unknown. Herein, we review GETV temporal and spatial distribution, molecular genetic evolution, transmission and data on disease outbreaks. This work provides a reference for public health workers engaged in GETV research and zoonotic disease prevention and control.

Viral metagenomics unveiled extensive communications of viruses within giant pandas and their associated organisms in the same ecosystem

Cross-species transmission events were commonplace, with numerous cases of host-switching during the viral evolutionary history, but relatively little evidence for onward transmission in different species living in the same ecosystem. For understanding the communications of viruses in giant pandas (Ailuropoda melanoleuca) and their associated organisms, based on a large size of samples (N = 2305) collected between 2015 and 2020 from giant panda (N = 776) and other four giant panda-associated organisms in the same ecosystem, red pandas (N = 700), stray cats (N = 32), wild rats (N = 42), and mosquitoes (N = 755), viromics was used for the virus identification and subsequent virus traceability. The results showed that a feline panleukopenia virus (FPV) was found in giant pandas with clinical signs of vomiting and mild diarrhea. Meanwhile, the same FPV strain was also prevalent in the healthy red panda (Ailurus fulgens) population. From the viromes of the five different organisms, 250 virus genomes were determined. Our data revealed that besides FPV, other putative pathogenic viruses, such as red panda amdoparvoviruses (RPAVs) and Getah viruses (GETVs) were responsible for previous disease or death of some red pandas. We also demonstrated that a number of viruses were involved in potential interspecies jumping events between giant pandas and their associated species. Collectively, our results shed light on the genetic diversity and relationship of diverse viral pathogens in 'Giant pandas-Associated animals-Arthropods' and report some cases of possible viral host-switching among these host species living in the same ecosystem.

Getah Virus Infection Rapidly Causes Testicular Damage and Decreases Sperm Quality in Male Mice

Getah virus (GETV) is a zoonotic arbovirus that can cause infection in many animals. It can cause pyrexia and reproductive losses in animals. The objective of the study was to explore the effects of GETV on male reproductive ability. Male mice were injected with 100 × TCID50/0.1 ml in a volume of 100-μL GETV in their hindquarter muscle, resulting in decreased semen quality and testicular histopathological changes, and the virus was detected in the testes. At 0.5 dpi (day post-infection), male mice showed decreased sperm density, motility, and decreased serum testosterone concentration, an increased sperm malformation rate, vacuoles in spermatogonial cells/spermatocytes in spermatogenic tubules, and the highest virus copies in testis. At 2 dpi, the sperm density and motility reached the lowest value of 3.99 × 106/ml and 62.03%, and the malformation rate reached 43.67%. At 28 dpi, the sperm indexes of the experimental group gradually approached that of the control group, but there were still significant differences. Since then, histopathological changes have worsened, with the most severe histopathological changes at 7 dpi and gradual recovery. Up to 14 dpi, the virus was detected by qRT-PCR and immunohistochemistry, which showed that the virus was only present in the testicular interstitium. GETV infection can rapidly enter the testis of mice and reduce the semen quality of mice, which needs to be paid attention to in the prevention and control of GETV.

Construction and characterization of a full-length infectious clone of Getah virus in vivo

Getah virus (GETV) is a mosquito-borne virus of the genus Alphavirus in the family Togaviridae and, in recent years, it has caused several outbreaks in animals. The molecular basis for GETV pathogenicity is not well understood. Therefore, a reverse genetic system of GETV is needed to produce genetically modified viruses for the study of the viral replication and its pathogenic mechanism. Here, we generated a CMV-driven infectious cDNA clone based on a previously isolated GETV strain, GX201808 (pGETV-GX). Transfection of pGETV-GX into BHK-21 ​cells resulted in the recovery of a recombinant virus (rGETV-GX) which showed similar growth characteristics to its parental virus. Then three-day-old mice were experimentally infected with either the parental or recombinant virus. The recombinant virus showed milder pathogenicity than the parental virus in the mice. Based on the established CMV-driven cDNA clone, subgenomic promoter and two restriction enzyme sites (BamHI and EcoRI) were introduced into the region between E1 protein and 3′UTR. Then the green fluorescent protein (GFP), red fluorescent protein (RFP) and improved light-oxygen-voltage (iLOV) genes were inserted into the restriction enzyme sites. Transfection of the constructs carrying the reporter genes into BHK-21 ​cells proved the rescue of the recombinant reporter viruses. Taken together, the establishment of a reverse genetic system for GETV provides a valuable tool for the study of the virus life cycle, and to aid the development of genetically engineered GETVs as vectors for foreign gene expression.

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Generation and recovery of a CMV-driven infectious cDNA clone of GETV isolate, GX201808 (pGETV-GX).

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The recombinant virus showed milder pathogenicity than the parental virus in a mouse model.

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The Getah virus infectious clone can be used as a vector for expressing reporter genes.

Structural Insights into Alphavirus Assembly Revealed by the Cryo-EM Structure of Getah Virus

Getah virus (GETV) is a member of the alphavirus genus, and it infects a variety of animal species, including horses, pigs, cattle, and foxes. Human infection with this virus has also been reported. The structure of GETV has not yet been determined. In this study, we report the cryo-EM structure of GETV at a resolution of 3.5 Å. This structure reveals conformational polymorphism of the envelope glycoproteins E1 and E2 at icosahedral 3-fold and quasi-3-fold axes, which is believed to be a necessary organization in forming a curvature surface of virions. In our density map, three extra densities are identified, one of which is believed a “pocket factor”; the other two are located by domain D of E2, and they may maintain the stability of E1/E2 heterodimers. We also identify three N-glycosylations at E1 N141, E2 N200, and E2 N262, which might be associated with receptor binding and membrane fusion. The resolving of the structure of GETV provides new insights into the structure and assembly of alphaviruses and lays a basis for studying the differences of biology and pathogenicity between arthritogenic and encephalitic alphaviruses.

Molecular and Serological Surveillance of Getah Virus in the Xinjiang Uygur Autonomous Region, China, 2017-2020

The Getah virus (GETV), a mosquito-borne RNA virus, is widely distributed in Oceania and Asia. GETV is not the only pathogenic to horses, pigs, cattle, foxes and boars, but it can also cause fever in humans. Since its first reported case in Chinese mainland in 2017, the number of GETV-affected provinces has increased to seventeen till now. Therefore, we performed an epidemiologic investigation of GETV in the Xinjiang region, located in northwestern China, during the period of 2017–2020. ELISA was used to analyze 3299 serum samples collected from thoroughbred horse, local horse, sheep, goat, cattle, and pigs, with thoroughbred horse (74.8%), local horse (67.3%), goat (11.7%), sheep (10.0%), cattle (25.1%) and pigs (51.1%) being positive for anti-GETV antibodies. Interestingly, the neutralizing antibody titer in horses was much higher than in other species. Four samples from horses and pigs were positive for GETV according to RT-PCR. Furthermore, from the serum of a local horse, we isolated GETV which was designated as strain XJ-2019-07, and determined its complete genome sequence. From the phylogenetic relationships, it belongs to the Group III lineage. This is the first evidence of GETV associated to domestic animals in Xinjiang. Overall, GETV is prevalent in Xinjiang and probably has been for several years. Since no vaccine against GETV is available in China, detection and monitoring strategies should be improved in horses and pigs, especially imported and farmed, in order to prevent economic losses.

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We firstly reported the epidemiology and isolation of GETV infection in livestock in Xinjiang.

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GETV is prevalent in Xinjiang and probably has been for several years.

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Since no vaccine against GETV is available in China, detection and monitoring strategies should be improved in horses and pigs, especially imported and farmed, in order to prevent economic losses.

Origin, genetic diversity, adaptive evolution and transmission dynamics of Getah virus

As a member of the Alphavirus, Getah virus (GETV) was becoming more serious and posing a serious threat to animal safety and public health. However, the circulation, distribution and evolution of GETV is not well understood. Hence, we integrated a variety of bioinformatic methodologies, from genomic alterations to systematic analysis, phylogeography, selection, adaptive analysis, prediction of protein modification, structural biology and molecular dynamics simulations to understand the characteristics of GETV. The results of phylogeography and molecular evolution show that due to the lack of vaccine, GETV is rapidly expanding its host range and geographical distribution at a high evolutionary rate. We also predicted the important modification sites, and identified the adaptive and active selection sites. Finally, the analysis of spatial structure and function showed that six adaptive sites may be related to the structural stability, receptor binding ability, immunogenicity and immune evasion of the virus, respectively. The data from this study have important implications for the understanding of ongoing GETV outbreaks worldwide and will guide future efforts to develop effective preventive and control measures against GETV. In particular, biosafety measures should be strengthened immediately to prevent GETV from becoming a pandemic, especially in China, South Korea and Japan.

Development of a reverse transcription recombinase-aided amplification assay for detection of Getah virus

GETV, an arbo-borne zoonotic virus of the genus Alphavirus, which causes diarrhea and reproduction disorders in swine, lead to serious economic losses to the swine industry in China. At present, the existing methods for GETV detection are time-consuming and low sensitivity, so, a rapid, accurate and sensitive GETV detection method is urgently needed. In this study, a fluorescent reverse transcription recombinase-assisted amplification method (RT-RAA) was successfully established for the rapid detection of GETV. The sensitivity of this method to GETV was 8 copies/reaction and 20 TCID₅₀/reaction. No cross-reaction with other viruses. A total of 118 samples were prepared for GETV detection using fluorescent RT-RAA and SYBR Green I RT-qPCR, the coincidence rate of the two methods was 100%. The results suggest that the RT-RAA method is rapid, sensitive and specific for GETV detection and can be applied in the clinical.

Monitoring Mosquito-Borne Arbovirus in Various Insect Regions in China in 2018

Background

Increases in global travel and trade are changing arbovirus distributions worldwide. Arboviruses can be introduced by travelers, migratory birds, or vectors transported via international trade. Arbovirus surveillance in field-collected mosquitoes may provide early evidence for mosquito-borne disease transmission.

Methods

During the seasons of high mosquito activity of 2018, 29,285 mosquitoes were sampled from seven sentinel sites in various insect regions. The mosquitoes were analyzed by RT-PCR for alphaviruses, flaviviruses, and orthobunyaviruses.

Results

We detected three strains of Japanese encephalitis virus (JEV), five strains of Getah virus (GETV), and 45 strains of insect-specific flaviviruses including Aedes flavivirus (AeFV, 1), Chaoyang virus (CHAOV, 1), Culex flavivirus (CxFV, 17), Hanko virus (HANKV, 2), QuangBinh virus (QBV, 22), and Yunnan Culex flavivirus (YNCxFV, 2). Whole genomes of one strain each of GETV, CxFV, CHAOV, and AeFV were successfully amplified. Phylogenetic analysis revealed that the new JEV strains detected in the Shanghai and Hubei Provinces belong to the GI-b strain and are phylogenetically close to the NX1889 strain (MT134112) isolated from a patient during a JE outbreak in Ningxia in 2018. GETVs were found in Inner Mongolia, Hubei, and Hainan and belonged to Group III. They were closely related to strains isolated from swine. HANKV was recorded for the first time in China and other ISFVs were newly detected at several sentinel sites. The bias-corrected maximum likelihood estimation value for JEV in Jinshan, Shanghai was 4.52/1,000 (range 0.80-14.64). Hence, there is a potential risk of a JEV epidemic in that region.

Conclusion

GI-b is the dominant circulating JEV genotype in nature and poses a health risk to animals and humans. The potential threat of widespread GETV distribution as a zoonosis is gradually increasing. The present study also disclosed the dispersion and host range of ISFVs. These findings highlight the importance of tracing the movements of the vectors and hosts of mosquito-borne pathogens in order to prevent and control arbovirus outbreaks in China.

A Metagenomic Analysis of Mosquito Virome Collected From Different Animal Farms at Yunnan-Myanmar Border of China

Metagenomic analysis of mosquito-borne and mosquito-specific viruses is useful to understand the viral diversity and for the surveillance of pathogens of medical and veterinary importance. Yunnan province is located at the southwest of China and has rich abundance of mosquitoes. Arbovirus surveillance is not conducted regularly in this province particularly at animal farms, which have public health as well as veterinary importance. Here, we have analyzed 10 pools of mosquitoes belonging to Culex tritaeniorhyncus, Aedes aegypti, Anopheles sinensis, and Armigeres subalbatus species, collected from different animal farms located at Yunnan province of China by using metagenomic next-generation sequencing technique. The generated viral metagenomic data reveal that the viral community matched by the reads was highly diverse and varied in abundance among animal farms, which contained more than 19 viral taxonomic families, specific to vertebrates, invertebrates, fungi, plants, protozoa, and bacteria. Additionally, a large number of viral reads were related to viruses that are non-classified. The viral reads related to animal viruses included parvoviruses, anelloviruses, circoviruses, flaviviruses, rhabdoviruses, and seadornaviruses, which might be taken by mosquitoes from viremic animal hosts during blood feeding. Notably, the presence of viral reads matched with Japanese encephalitis virus, Getah virus, and porcine parvoviruses in mosquitoes collected from different geographic sites suggested a potential circulation of these viruses in their vertebrate hosts. Overall, this study provides a comprehensive knowledge of diverse viral populations present at animal farms of Yunnan province of China, which might be a potential source of diseases for humans and domestic animals.

Comparative viromes of Culicoides and mosquitoes reveal their consistency and diversity in viral profiles

The genus Culicoides includes biting midges, some of which are vectors for viruses that cause diseases in humans and animals. Knowledge of the roles of Culicoides in viral ecology is inadequate. We collected ~300 000 samples of Culicoides and mosquitoes in 15 representative regions within Yunnan, China. Using mosquitoes as reference vectors, we designed a comparative virome strategy to study the viral composition, diversity, hosts and spatiotemporal distribution of Culicoides. A map of viromes in Culicoides and mosquitoes in Yunan province, China, was constructed. At the same locations, Culicoides and mosquitoes usually share a similar viral diversity. At least 10 important pathogenic viruses were detected from Culicoides. Many novel viruses were discovered, including 21 segmented viruses of Flaviviridae, 180 viruses of Monjiviricetes and 130 viruses of Bunyavirales. The findings demonstrate that Culicoides is an important part of viral ecology and should be studied and monitored for potentially emerging viruses.

Emergence and Phylogenetic Analysis of a Getah Virus Isolated in Southern China

Getah virus (GETV) has caused many outbreaks in animals in recent years. Monitoring of the virus and its related diseases is crucial to control the transmission of the virus. In the summer of 2018, we conducted routine tests on clinical samples from different pig farms in Guangxi province, South China, and isolated and characterized a GETV strain, named GX201808. Cytopathic effects were observed in BHK-21 cells inoculated with GX201808. The expression of E2 protein of GETV could be detected in virus-infected cells by indirect immunofluorescence assays. Electron microscopic analysis showed that the virus particles were spherical and ~70 nm in diameter with featured surface fibers. The multistep growth curves showed the virus propagated well in the BHK-21 cells. Molecular genetic analysis revealed that GX201808 belongs to Group 3, represented by Kochi-01-2005 isolated in Japan in 2005, and it clustered closely with the recently reported Chinese strains isolated from pigs, cattle, and foxes. A comparison of the identities of nucleotides and amino acids in the coding regions demonstrated that the GX201808 showed the highest amino acid identity (99.6%) with the HuN1 strain, a highly pathogenic isolate resulting in an outbreak of GETV infection in swine herds in Hunan province in 2017. In the present study, GETV was identified and isolated for the first time in Guangxi province of southern China, suggesting that future surveillance of this virus should be strengthened.

Sequencing of Historical Isolates, K-mer Mining and High Serological Cross-Reactivity with Ross River Virus Argue against the Presence of Getah Virus in Australia

Getah virus (GETV) is a mosquito-transmitted alphavirus primarily associated with disease in horses and pigs in Asia. GETV was also reported to have been isolated from mosquitoes in Australia in 1961; however, retrieval and sequencing of the original isolates (N544 and N554), illustrated that these viruses were virtually identical to the 1955 GETV_MM2021 isolate from Malaysia. K-mer mining of the >40,000 terabases of sequence data in the Sequence Read Archive followed by BLASTn confirmation identified multiple GETV sequences in biosamples from Asia (often as contaminants), but not in biosamples from Australia. In contrast, sequence reads aligning to the Australian Ross River virus (RRV) were readily identified in Australian biosamples. To explore the serological relationship between GETV and other alphaviruses, an adult wild-type mouse model of GETV was established. High levels of cross-reactivity and cross-protection were evident for convalescent sera from mice infected with GETV or RRV, highlighting the difficulties associated with the interpretation of early serosurveys reporting GETV antibodies in Australian cattle and pigs. The evidence that GETV circulates in Australia is thus not compelling.

Arthritogenic Alphavirus Vaccines: Serogrouping Versus Cross-Protection in Mouse Models

Chikungunya virus (CHIKV), Ross River virus (RRV), o’nyong nyong virus (ONNV), Mayaro virus (MAYV) and Getah virus (GETV) represent arthritogenic alphaviruses belonging to the Semliki Forest virus antigenic complex. Antibodies raised against one of these viruses can cross-react with other serogroup members, suggesting that, for instance, a CHIKV vaccine (deemed commercially viable) might provide cross-protection against antigenically related alphaviruses. Herein we use human alphavirus isolates (including a new human RRV isolate) and wild-type mice to explore whether infection with one virus leads to cross-protection against viremia after challenge with other members of the antigenic complex. Persistently infected Rag1^-/- mice were also used to assess the cross-protective capacity of convalescent CHIKV serum. We also assessed the ability of a recombinant poxvirus-based CHIKV vaccine and a commercially available formalin-fixed, whole-virus GETV vaccine to induce cross-protective responses. Although cross-protection and/or cross-reactivity were clearly evident, they were not universal and were often suboptimal. Even for the more closely related viruses (e.g., CHIKV and ONNV, or RRV and GETV), vaccine-mediated neutralization and/or protection against the intended homologous target was significantly more effective than cross-neutralization and/or cross-protection against the heterologous virus. Effective vaccine-mediated cross-protection would thus likely require a higher dose and/or more vaccinations, which is likely to be unattractive to regulators and vaccine manufacturers.

Endemic and Emerging Arboviruses in Domestic Ruminants in East Asia

Epizootic congenital abnormalities caused by Akabane, Aino, and Chuzan viruses have damaged the reproduction of domestic ruminants in East Asia for many years. In the past, large outbreaks of febrile illness related to bovine ephemeral fever and Ibaraki viruses severely affected the cattle industry in that region. In recent years, vaccines against these viruses have reduced the occurrence of diseases, although the viruses are still circulating and have occasionally caused sporadic and small-scaled epidemics. Over a long-term monitoring period, many arboviruses other than the above-mentioned viruses have been isolated from cattle and Culicoides biting midges in Japan. Several novel arboviruses that may infect ruminants (e.g., mosquito- and tick-borne arboviruses) were recently reported in mainland China based on extensive surveillance. It is noteworthy that some are suspected of being associated with cattle diseases. Malformed calves exposed to an intrauterine infection with orthobunyaviruses (e.g., Peaton and Shamonda viruses) have been observed. Epizootic hemorrhagic disease virus serotype 6 caused a sudden outbreak of hemorrhagic disease in cattle in Japan. Unfortunately, the pathogenicity of many other viruses in ruminants has been uncertain, although these viruses potentially affect livestock production. As global transportation grows, the risk of an accidental incursion of arboviruses is likely to increase in previously non-endemic areas. Global warming will also certainly affect the distribution and active period of vectors, and thus the range of virus spreads will expand to higher-latitude regions. To prevent anticipated damages to the livestock industry, the monitoring system for arboviral circulation and incursion should be strengthened; moreover, the sharing of information and preventive strategies will be essential in East Asia.