Genomic characterizations of bat coronaviruses (1A, 1B and HKU8) and evidence for co-infections in Miniopterus bats

Target enrichment metaviromics enables comprehensive surveillance of coronaviruses in environmental and animal samples

The COVID-19 pandemic has underscored the importance of understanding the role of animals in the transmission of coronaviruses (CoVs) and their impact on human health. A One Health approach, integrating human, animal, and environmental health, is essential for effective CoVs control. Next-generation sequencing has played a pivotal role in identifying and monitoring the evolution of novel CoVs strains, like SARS-CoV-2. However, viral occurrence and diversity studies in environmental and animal samples are challenging because of the complexity of viral communities and low abundance of viruses in these samples. Target enrichment sequencing (TES) has emerged as a valuable tool for investigating viral families in challenging samples. This approach involves the specific capture and enrichment of viral genomes using sequence-specific probes, thereby enhancing the efficiency of detection and characterization. In this study, we aimed to develop and validate a TES panel to study CoVs in various complex environmental and animal derived samples. The results demonstrated the panel's effectiveness in capturing and sequencing a wide diversity of CoVs providing valuable insights into their abundance and host diversity in urban wastewater, farm animal corpses lixiviates and bat guano samples. In sewage samples, CoVs were detected solely when TES was employed while in guano samples, sequencing of CoVs species was achieved in 2 out of 4 samples showing an almost three-logarithmic increase in the number of reads obtained in comparison with the untargeted approach. For animal lixiviates, only the TES application enabled the acquisition of CoVs reads. The information obtained can significantly contribute to early detection, surveillance, and control measures for CoVs, including viral discovery and potential spillover events. Additionally, this sequencing panel shows potential for studying other significant viral families and monitoring viral diversity in different animal populations.

Viral Co-Infection in Bats: A Systematic Review

Co-infection is an underappreciated phenomenon in contemporary disease ecology despite its ubiquity and importance in nature. Viruses, and other co-infecting agents, can interact in ways that shape host and agent communities, influence infection dynamics, and drive evolutionary selective pressures. Bats are host to many viruses of zoonotic potential and have drawn increasing attention in their role as wildlife reservoirs for human spillover. However, the role of co-infection in driving viral transmission dynamics within bats is unknown. Here, we systematically review peer-reviewed literature reporting viral co-infections in bats. We show that viral co-infection is common in bats but is often only reported as an incidental finding. Biases identified in our study database related to virus and host species were pre-existing in virus studies of bats generally. Studies largely speculated on the role co-infection plays in viral recombination and few investigated potential drivers or impacts of co-infection. Our results demonstrate that current knowledge of co-infection in bats is an ad hoc by-product of viral discovery efforts, and that future targeted co-infection studies will improve our understanding of the role it plays. Adding to the broader context of co-infection studies in other wildlife species, we anticipate our review will inform future co-infection study design and reporting in bats. Consideration of detection strategy, including potential viral targets, and appropriate analysis methodology will provide more robust results and facilitate further investigation of the role of viral co-infection in bat reservoirs.

Comparative virome analysis of individual shedding routes of Miniopterus phillipsi bats inhabiting the Wavul Galge cave, Sri Lanka

Bats are described as the natural reservoir host for a wide range of viruses. Although an increasing number of bat-associated, potentially human pathogenic viruses were discovered in the past, the full picture of the bat viromes is not explored yet. In this study, the virome composition of Miniopterus phillipsi bats (formerly known as Miniopterus fuliginosus bats in Sri Lanka) inhabiting the Wavul Galge cave, Sri Lanka, was analyzed. To assess different possible excretion routes, oral swabs, feces and urine were collected and analyzed individually by using metagenomic NGS. The data obtained was further evaluated by using phylogenetic reconstructions, whereby a special focus was set on RNA viruses that are typically associated with bats. Two different alphacoronavirus strains were detected in feces and urine samples. Furthermore, a paramyxovirus was detected in urine samples. Sequences related to Picornaviridae, Iflaviridae, unclassified Riboviria and Astroviridae were identified in feces samples and further sequences related to Astroviridae in urine samples. No viruses were detected in oral swab samples. The comparative virome analysis in this study revealed a diversity in the virome composition between the collected sample types which also represent different potential shedding routes for the detected viruses. At the same time, several novel viruses represent first reports of these pathogens from bats in Sri Lanka. The detection of two different coronaviruses in the samples indicates the potential general persistence of this virus species in M. phillipsi bats. Based on phylogenetics, the identified viruses are closely related to bat-associated viruses with comparably low estimation of human pathogenic potential. In further studies, the seasonal variation of the virome will be analyzed to identify possible shedding patterns for particular viruses.

Detection of Alpha- and Betacoronaviruses in Frugivorous and Insectivorous Bats in Nigeria

The rise of bat-associated zoonotic viruses necessitates a close monitoring of their natural hosts. Since the detection of severe acute respiratory syndrome coronavirus (SARS-CoV), it is evident that bats are vital reservoirs of coronaviruses (CoVs). In this study, we investigated the presence of CoVs in multiple bat species in Nigeria to identify viruses in bats at high-risk human contact interfaces. Four hundred and nine bats comprising four bat species close to human habitats were individually sampled from five states in Nigeria between 2019 and 2021. Coronavirus detection was done using broadly reactive consensus PCR primers targeting the RNA-dependent RNA polymerase (RdRp) gene of CoVs. Coronavirus RNA was detected in 39 samples (9.5%, CI 95%: [7.0, 12.8]), of which 29 were successfully sequenced. The identified CoVs in Nigerian bats were from the unclassified African alphacoronavirus lineage and betacoronavirus lineage D (Nobecovirus), with one sample from Hipposideros ruber coinfected with alphacoronavirus and betacoronavirus. Different bat species roosting in similar or other places had CoVs from the same genetic lineage. The phylogenetic and evolutionary dynamics data indicated a high CoV diversity in Nigeria, while host switching may have contributed to CoV evolution. Robust sentinel surveillance is recommended to enhance our knowledge of emerging and re-emerging coronaviruses.

An overview of advancement in aptasensors for influenza detection

INTRODUCTION

The platforms for early identification of infectious diseases such as influenza has seen a surge in recent years as delayed diagnosis of such infections can lead to dreadful effects causing large numbers of deaths. The time taken in detection of an infectious disease may vary from a few days to a few weeks depending upon the choice of the techniques. So, there is an urgent need for advanced methodologies for early diagnosis of the influenza.

AREAS COVERED

The emergence of "Aptasensor" synergistically with biosensors for diagnosis has opened a new era for sensitive, selective and early detection approaches. This review described various conventional as well as advanced methods based on artificial immunogenic nucleotide sequences complementing a part of the virus, i.e., aptamers based aptasensors for influenza diagnosis and the challenges faced in their commercialization.

EXPERT OPINION

Although numerous traditional methods are available for influenza detection but mostly associated with low sensitivity, specificity, high cost, trained personnel, and animals required for virus culture/ antibody raising as the major drawbacks. Aptamers can be manufactured invitro as 'chemical antibodies' at commercial level, no animal required. Following these advantages, aptamers can pave the way for an efficient diagnostic technique as compared to other existing conventional methods..

Ecology, evolution and spillover of coronaviruses from bats

In the past two decades, three coronaviruses with ancestral origins in bats have emerged and caused widespread outbreaks in humans, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since the first SARS epidemic in 2002-2003, the appreciation of bats as key hosts of zoonotic coronaviruses has advanced rapidly. More than 4,000 coronavirus sequences from 14 bat families have been identified, yet the true diversity of bat coronaviruses is probably much greater. Given that bats are the likely evolutionary source for several human coronaviruses, including strains that cause mild upper respiratory tract disease, their role in historic and future pandemics requires ongoing investigation. We review and integrate information on bat-coronavirus interactions at the molecular, tissue, host and population levels. We identify critical gaps in knowledge of bat coronaviruses, which relate to spillover and pandemic risk, including the pathways to zoonotic spillover, the infection dynamics within bat reservoir hosts, the role of prior adaptation in intermediate hosts for zoonotic transmission and the viral genotypes or traits that predict zoonotic capacity and pandemic potential. Filling these knowledge gaps may help prevent the next pandemic.

A Systematic Review on COVID-19 Vaccine Strategies, Their Effectiveness, and Issues

COVID-19 vaccines are indispensable, with the number of cases and mortality still rising, and currently no medicines are routinely available for reducing morbidity and mortality, apart from dexamethasone, although others are being trialed and launched. To date, only a limited number of vaccines have been given emergency use authorization by the US Food and Drug Administration and the European Medicines Agency. There is a need to systematically review the existing vaccine candidates and investigate their safety, efficacy, immunogenicity, unwanted events, and limitations. The review was undertaken by searching online databases, i.e., Google Scholar, PubMed, and ScienceDirect, with finally 59 studies selected. Our findings showed several types of vaccine candidates with different strategies against SARS-CoV-2, including inactivated, mRNA-based, recombinant, and nanoparticle-based vaccines, are being developed and launched. We have compared these vaccines in terms of their efficacy, side effects, and seroconversion based on data reported in the literature. We found mRNA vaccines appeared to have better efficacy, and inactivated ones had fewer side effects and similar seroconversion in all types of vaccines. Overall, global variant surveillance and systematic tweaking of vaccines, coupled with the evaluation and administering vaccines with the same or different technology in successive doses along with homologous and heterologous prime-booster strategy, have become essential to impede the pandemic. Their effectiveness appreciably outweighs any concerns with any adverse events.

The taxonomy, host range and pathogenicity of coronaviruses and other viruses in the Nidovirales order

The frequent emergence of coronavirus (CoV) epidemics has seriously threatened public health and stock farming. The major hosts for CoVs are birds and mammals. Although most CoVs inhabit their specific natural hosts, some may occasionally cross the host barrier to infect livestock and even people, causing a variety of diseases. Since the beginning of the new century, increasing attention has been given to research on CoVs due to the emergence of highly pathogenic and genetically diverse CoVs that have caused several epidemics, including the recent COVID-19 pandemic. CoVs belong to the Coronaviridae family of the Nidovirales order. Recently, advanced techniques for viral detection and viral genome analyses have enabled characterization of many new nidoviruses than ever and have greatly expanded the Nidovirales order with new classification and nomenclature. Here, we first provide an overview of the latest research progress in the classification of the Nidovirales order and then introduce the host range, genetic variation, genomic pattern and pathogenic features of epidemic CoVs and other epidemic viruses. This information will promote understanding of the phylogenetic relationship and infectious transmission of various pathogenic nidoviruses, including epidemic CoVs, which will benefit virological research and viral disease control.

Antiviral performance of graphene-based materials with emphasis on COVID-19: A review

Coronavirus disease-2019 has been one of the most challenging global epidemics of modern times with a large number of casualties combined with economic hardships across the world. Considering that there is still no definitive cure for the recent viral crisis, this article provides a review of nanomaterials with antiviral activity, with an emphasis on graphene and its derivatives, including graphene oxide, reduced graphene oxide and graphene quantum dots. The possible interactions between surfaces of such nanostructured materials with coronaviruses are discussed. The antiviral mechanisms of graphene materials can be related to events such as the inactivation of virus and/or the host cell receptor, electrostatic trapping and physico-chemical destruction of viral species. These effects can be enhanced by functionalization and/or decoration of carbons with species that enhances graphene-virus interactions. The low-cost and large-scale preparation of graphene materials with enhanced antiviral performances is an interesting research direction to be explored.

Characterization of bat coronaviruses: a latent global threat

It has been speculated that bats serve as reservoirs of a huge variety of emerging coronaviruses (CoVs) that have been responsible for severe havoc in human health systems as well as negatively affecting human economic and social systems. A prime example is the currently active severe acute respiratory syndrome (SARS)-CoV2, which presumably originated from bats, demonstrating that the risk of a new outbreak of bat coronavirus is always latent. Therefore, an in-depth investigation to better comprehend bat CoVs has become an important issue within the international community, a group that aims to attenuate the consequences of future outbreaks. In this review, we present a concise introduction to CoVs found in bats and discuss their distribution in Southeast Asia. We also discuss the unique adaptation features in bats that confer the ability to be a potential coronavirus reservoir. In addition, we review the bat coronavirus-linked diseases that have emerged in the last two decades. Finally, we propose key factors helpful in the prediction of a novel coronavirus outbreak and present the most recent methods used to forecast an evolving outbreak.

A database resource and online analysis tools for coronaviruses on a historical and global scale

The recent outbreak of COVID-19 caused by a new zoonotic origin coronavirus (SARS-CoV-2 or 2019-nCoV) has sound the alarm for the potential spread of epidemic coronavirus crossing species. With the urgent needs to assist disease control and to provide invaluable scientific information, we developed the coronavirus database (CoVdb), an online genomic, proteomic and evolutionary analysis platform. CoVdb has brought together genomes of more than 5000 coronavirus strains, which were collected from 1941 to 2020, in more than 60 countries and in hosts belonging to more than 30 species, ranging from fish to human. CoVdb presents comprehensive genomic information, such as gene function, subcellular localization, topology and protein structure. To facilitate coronavirus research, CoVdb also provides flexible search approaches and online tools to view and analyze protein structure, to perform multiple alignments, to automatically build phylogenetic trees and to carry on evolutionary analyses. CoVdb can be accessed freely at http://covdb.popgenetics.net. Hopefully, it will accelerate the progress to develop medicines or vaccines to control the pandemic of COVID-19.

Detection of Alpha- and Betacoronaviruses in Miniopterus fuliginosus and Rousettus leschenaultii, two species of Sri Lankan Bats

Bats are known to be potential reservoirs of numerous human-pathogenic viruses. They have been identified as natural hosts for coronaviruses, causing Severe Acute Respiratory Syndrome (SARS) in humans. Since the emergence of SARS-CoV-2 in 2019 interest in the prevalence of coronaviruses in bats was newly raised. In this study we investigated different bat species living in a sympatric colony in the Wavul Galge cave (Koslanda, Sri Lanka). In three field sessions (in 2018 and 2019), 395 bats were captured (Miniopterus, Rousettus, Hipposideros and Rhinolophus spp.) and either rectal swabs or fecal samples were collected. From these overall 396 rectal swab and fecal samples, the screening for coronaviruses with nested PCR resulted in 33 positive samples, 31 of which originated from Miniopterus fuliginosus and two from Rousettus leschenaultii. Sanger sequencing and phylogenetic analysis of the obtained 384-nt fragment of the RNA-dependent RNA polymerase revealed that the examined M. fuliginosus bats excrete alphacoronaviruses and the examined R. leschenaultii bats excrete betacoronaviruses. Despite the sympatric roosting habitat, the coronaviruses showed host specificity and seemed to be limited to one species. Our results represent an important basis to better understand the prevalence of coronaviruses in Sri Lankan bats and may provide a basis for pursuing studies on particular bat species of interest.

Biodiversity loss and COVID-19 pandemic: The role of bats in the origin and the spreading of the disease

The loss of biodiversity in the ecosystems has created the general conditions that have favored and, in fact, made possible, the insurgence of the COVID-19 pandemic. A lot of factors have contributed to it: deforestation, changes in forest habitats, poorly regulated agricultural surfaces, mismanaged urban growth. They have altered the composition of wildlife communities, greatly increased the contacts of humans with wildlife, and altered niches that harbor pathogens, increasing their chances to come in contact with humans. Among the wildlife, bats have adapted easily to anthropized environments such as houses, barns, cultivated fields, orchards, where they found the suitable ecosystem to prosper. Bats are major hosts for αCoV and βCoV: evolution has shaped their peculiar physiology and their immune system in a way that makes them resistant to viral pathogens that would instead successfully attack other species, including humans. In time, the coronaviruses that bats host as reservoirs have undergone recombination and other modifications that have increased their ability for inter-species transmission: one modification of particular importance has been the development of the ability to use ACE2 as a receptor in host cells. This particular development in CoVs has been responsible for the serious outbreaks in the last two decades, and for the present COVID-19 pandemic.

Genomic recombination events may reveal the evolution of coronavirus and the origin of SARS-CoV-2

To trace the evolution of coronaviruses and reveal the possible origin of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the coronavirus disease 2019 (COVID-19), we collected and thoroughly analyzed 29,452 publicly available coronavirus genomes, including 26,312 genomes of SARS-CoV-2 strains. We observed coronavirus recombination events among different hosts including 3 independent recombination events with statistical significance between some isolates from humans, bats and pangolins. Consistent with previous records, we also detected putative recombination between strains similar or related to Bat-CoV-RaTG13 and Pangolin-CoV-2019. The putative recombination region is located inside the receptor-binding domain (RBD) of the spike glycoprotein (S protein), which may represent the origin of SARS-CoV-2. Population genetic analyses provide estimates suggesting that the putative introduced DNA within the RBD is undergoing directional evolution. This may result in the adaptation of the virus to hosts. Unsurprisingly, we found that the putative recombination region in S protein was highly diverse among strains from bats. Bats harbor numerous coronavirus subclades that frequently participate in recombination events with human coronavirus. Therefore, bats may provide a pool of genetic diversity for the origin of SARS-CoV-2.

Evolutionary dynamics and geographic dispersal of beta coronaviruses in African bats

Bats have been shown to serve as reservoir host of various viral agents including coronaviruses. They have also been associated with the novel coronavirus SARS-CoV-2. This has made them an all important agent for CoV evolution and transmission. Our objective in this study was to investigate the dispersal, phylogenomics and evolution of betacoronavirus (βCoV) among African bats. We retrieved sequence data from established databases such as GenBank and Virus Pathogen Resource, covering the partial RNA dependent RNA polymerase (RdRP) gene of bat coronaviruses from eight African, three Asian, five European, two South American countries and Australia. We analyzed for phylogeographic information relating to genetic diversity and evolutionary dynamics. Our study revealed that majority of the African strains fell within Norbecovirus subgenera, with an evolutionary rate of 1.301 × 10^-3, HPD (1.064 × 10^-3-1.434 × 10^-3) subs/site/year. The African strains diversified into three main subgenera, Norbecovirus, Hibecovirus and Merbecovirus. The time to most common recent ancestor for Norbecovirus strains was 1973, and 2007, for the African Merbecovirus strains. There was evidence of inter species transmission of Norbecovirus among bats in Cameroun and DRC. Phlylogeography showed that there were inter-continental spread of Bt-CoV from Europe, China and Hong Kong into Central and Southern Africa, highlighting the possibility of long distance transmission. Our study has elucidated the possible evolutionary origins of βCoV among African bats; we therefore advocate for broader studies of whole genome sequences of BtCoV to further understand the drivers for their emergence and zoonotic spillovers into human population.

Novel viruses detected in bats in the Republic of Korea

Bats are natural reservoirs for potential zoonotic viruses. In this study, next-generation sequencing was performed to obtain entire genome sequences of picornavirus from a picornavirus-positive bat feces sample (16BF77) and to explore novel viruses in a pooled bat sample (16BP) from samples collected in South Korea, 2016. Fourteen mammalian viral sequences were identified from 16BF77 and 29 from 16BP, and verified by RT-PCR. The most abundant virus in 16BF77 was picornavirus. Highly variable picornavirus sequences encoding 3D^pol were classified into genera Kobuvirus, Shanbavirus, and an unassigned group within the family Picornaviridae. Amino acid differences between these partial 3D^pol sequences were ≥ 65.7%. Results showed that one bat was co-infected by picornaviruses of more than two genera. Retrovirus, coronavirus, and rotavirus A sequences also were found in the BP sample. The retrovirus and coronavirus genomes were identified in nine and eight bats, respectively. Korean bat retroviruses and coronavirus demonstrated strong genetic relationships with a Chinese bat retrovirus (RfRV) and coronavirus (HKU5-1), respectively. A co-infection was identified in one bat with a retrovirus and a coronavirus. Our results indicate that Korean bats were multiply infected by several mammal viruses.

Identification of potential inhibitors of coronavirus hemagglutinin-esterase using molecular docking, molecular dynamics simulation and binding free energy calculation

Abstract

The pandemic outbreak of the Corona viral infection has become a critical global health issue. Biophysical and structural evidence shows that spike protein possesses a high binding affinity towards host angiotensin-converting enzyme 2 and viral hemagglutinin-acetylesterase (HE) glycoprotein receptor. We selected HE as a target in this study to identify potential inhibitors using a combination of various computational approaches such as molecular docking, ADMET analysis, dynamics simulations and binding free energy calculations. Virtual screening of NPACT compounds identified 3,4,5-Trihydroxy-1,8-bis[(2R,3R)-3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl]benzo[7]annulen-6-one, Silymarin, Withanolide D, Spirosolane and Oridonin as potential HE inhibitors with better binding energy. Furthermore, molecular dynamics simulations for 100 ns time scale revealed that most of the key HE contacts were retained throughout the simulations trajectories. Binding free energy calculations using MM/PBSA approach ranked the top-five potential NPACT compounds which can act as effective HE inhibitors.

Graphic abstract

Electronic supplementary material

The online version of this article (10.1007/s11030-020-10135-w) contains supplementary material, which is available to authorized users.

Coronavirus testing indicates transmission risk increases along wildlife supply chains for human consumption in Viet Nam, 2013-2014

Outbreaks of emerging coronaviruses in the past two decades and the current pandemic of a novel coronavirus (SARS-CoV-2) that emerged in China highlight the importance of this viral family as a zoonotic public health threat. To gain a better understanding of coronavirus presence and diversity in wildlife at wildlife-human interfaces in three southern provinces in Viet Nam 2013-2014, we used consensus Polymerase Chain Reactions to detect coronavirus sequences. In comparison to previous studies, we observed high proportions of positive samples among field rats (34.0%, 239/702) destined for human consumption and insectivorous bats in guano farms (74.8%, 234/313) adjacent to human dwellings. Most notably among field rats, the odds of coronavirus RNA detection significantly increased along the supply chain from field rats sold by traders (reference group; 20.7% positivity, 39/188) by a factor of 2.2 for field rats sold in large markets (32.0%, 116/363) and 10.0 for field rats sold and served in restaurants (55.6%, 84/151). Coronaviruses were also detected in rodents on the majority of wildlife farms sampled (60.7%, 17/28). These coronaviruses were found in the Malayan porcupines (6.0%, 20/331) and bamboo rats (6.3%, 6/96) that are raised on wildlife farms for human consumption as food. We identified six known coronaviruses in bats and rodents, clustered in three Coronaviridae genera, including the Alpha-, Beta-, and Gammacoronaviruses. Our analysis also suggested either mixing of animal excreta in the environment or interspecies transmission of coronaviruses, as both bat and avian coronaviruses were detected in rodent feces on wildlife farms. The mixing of multiple coronaviruses, and their apparent amplification along the wildlife supply chain into restaurants, suggests maximal risk for end consumers and likely underpins the mechanisms of zoonotic spillover to people.

Wide Diversity of Coronaviruses in Frugivorous and Insectivorous Bat Species: A Pilot Study in Guinea, West Africa

Zoonoses can constitute a threat for public health that can have a global importance, as seen with the current COVID-19 pandemic of severe acute respiratory syndrome coronavirus (SARS-CoV2). Bats have been recognized as an important reservoir of zoonotic coronaviruses (CoVs). In West Africa, where there is a high diversity of bat species, little is known on the circulation of CoVs in these hosts, especially at the interface with human populations. In this study, in Guinea, we tested a total of 319 bats belonging to 14 genera and six families of insectivorous and frugivorous bats across the country, for the presence of coronaviruses. We found CoVs in 35 (11%) of the tested bats—in three insectivorous bat species and five fruit bat species that were mostly captured close to human habitat. Positivity rates varied from 5.7% to 100%, depending on bat species. A wide diversity of alpha and beta coronaviruses was found across the country, including three sequences belonging to SarbeCoVs and MerbeCoVs subgenera known to harbor highly pathogenic human coronaviruses. Our findings suggest that CoVs are widely spread in West Africa and their circulation should be assessed to evaluate the risk of exposure of potential zoonotic CoVs to humans.

Metagenomic characterisation of avian parvoviruses and picornaviruses from Australian wild ducks

Ducks can shed and disseminate viruses and thus play a role in cross-species transmission. In the current study, we detected and characterised various avian parvoviruses and picornaviruses from wild Pacific black ducks, Chestnut teals, Grey teals and Wood ducks sampled at multiple time points from a single location using metagenomics. We characterised 46 different avian parvoviruses belonging to three different genera Dependoparvovirus, Aveparvovirus and Chaphamaparvovirus, and 11 different avian picornaviruses tentatively belonging to four different genera Sicinivirus, Anativirus, Megrivirus and Aalivirus. Most of these viruses were genetically different from other currently known viruses from the NCBI dataset. The study showed that the abundance and number of avian picornaviruses and parvoviruses varied considerably throughout the year, with the high number of virus reads in some of the duck samples highly suggestive of an active infection at the time of sampling. The detection and characterisation of several parvoviruses and picornaviruses from the individual duck samples also suggests co-infection, which may lead to the emergence of novel viruses through possible recombination. Therefore, as new and emerging diseases evolve, it is relevant to explore and monitor potential animal reservoirs in their natural habitat.

Novel human coronavirus (SARS-CoV-2): A lesson from animal coronaviruses

The recent pandemic caused by the novel human coronavirus, referrred to as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), not only is having a great impact on the health care systems and economies in all continents but it is also causing radical changes of common habits and life styles. The novel coronavirus (CoV) recognises, with high probability, a zoonotic origin but the role of animals in the SARS-CoV-2 epidemiology is still largely unknown. However, CoVs have been known in animals since several decades, so that veterinary coronavirologists have a great expertise on how to face CoV infections in animals, which could represent a model for SARS-CoV-2 infection in humans. In the present paper, we provide an up-to-date review of the literature currently available on animal CoVs, focusing on the molecular mechanisms that are responsible for the emergence of novel CoV strains with different antigenic, biologic and/or pathogenetic features. A full comprehension of the mechanisms driving the evolution of animal CoVs will help better understand the emergence, spreading, and evolution of SARS-CoV-2.

Longitudinal and Cross-Sectional Sampling of Serpentovirus (Nidovirus) Infection in Captive Snakes Reveals High Prevalence, Persistent Infection, and Increased Mortality in Pythons and Divergent Serpentovirus Infection in Boas and Colubrids

The aim of this study of serpentovirus infection in captive snakes was to assess the susceptibility of different types of snakes to infection and disease, to survey viral genetic diversity, and to evaluate management practices that may limit infection and disease. Antemortem oral swabs were collected from 639 snakes from 12 US collections, including 62 species, 28 genera, and 6 families: Pythonidae (N = 414 snakes; pythons were overrepresented in the sample population), Boidae (79), Colubridae (116), Lamprophiidae (4), Elapidae (12), and Viperidae (14). Infection was more common in pythons (38%; 95% CI: 33.1-42.4%), and in boas (10%; 95% CI: 5.2-18.7%) than in colubrids (0.9%, 95% CI: <0.01-4.7%); infection was not detected in other snake families (lamprophiids 0/4, 95% CI: 0-49%; elapids 0/12, 95% CI: 0-24.2%; and vipers 0/14, 95% CI: 0-21.5%), but more of these snakes need to be tested to confirm these findings. Clinical signs of respiratory disease were common in infected pythons (85 of 144). Respiratory signs were only observed in 1 of 8 infected boas and were absent in the single infected colubrid. Divergent serpentoviruses were detected in pythons, boas, and colubrids, suggesting that different serpentoviruses might vary in their ability to infect snakes of different families. Older snakes were more likely to be infected than younger snakes (p-value < 0.001) but males and females were equally likely to be infected (female prevalence: 23.4%, 95% CI 18.7-28.9%; male prevalence: 23.5%, 95% CI 18-30.1%; p-value = 0.144). Neither age (p-value = 0.32) nor sex (p-value = 0.06) was statistically associated with disease severity. Longitudinal sampling of pythons in a single collection over 28 months revealed serpentovirus infection is persistent, and viral clearance was not observed. In this collection, infection was associated with significantly increased rates of mortality (p-value = 0.001) with death of 75% of infected pythons and no uninfected pythons over this period. Offspring of infected parents were followed: vertical transmission either does not occur or occurs with a much lower efficiency than horizontal transmission. Overall, these findings confirm that serpentoviruses pose a significant threat to the health of captive python populations and can cause infection in boa and colubrid species.

Characterization of a New Member of Alphacoronavirus with Unique Genomic Features in Rhinolophus Bats

Bats have been identified as a natural reservoir of a variety of coronaviruses (CoVs). Several of them have caused diseases in humans and domestic animals by interspecies transmission. Considering the diversity of bat coronaviruses, bat species and populations, we expect to discover more bat CoVs through virus surveillance. In this study, we described a new member of alphaCoV (BtCoV/Rh/YN2012) in bats with unique genome features. Unique accessory genes, ORF4a and ORF4b were found between the spike gene and the envelope gene, while ORF8 gene was found downstream of the nucleocapsid gene. All the putative genes were further confirmed by reverse-transcription analyses. One unique gene at the 3’ end of the BtCoV/Rh/YN2012 genome, ORF9, exhibits ~30% amino acid identity to ORF7a of the SARS-related coronavirus. Functional analysis showed ORF4a protein can activate IFN-β production, whereas ORF3a can regulate NF-κB production. We also screened the spike-mediated virus entry using the spike-pseudotyped retroviruses system, although failed to find any fully permissive cells. Our results expand the knowledge on the genetic diversity of bat coronaviruses. Continuous screening of bat viruses will help us further understand the important role played by bats in coronavirus evolution and transmission.

Bat Coronaviruses in China

During the past two decades, three zoonotic coronaviruses have been identified as the cause of large-scale disease outbreaks–Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS), and Swine Acute Diarrhea Syndrome (SADS). SARS and MERS emerged in 2003 and 2012, respectively, and caused a worldwide pandemic that claimed thousands of human lives, while SADS struck the swine industry in 2017. They have common characteristics, such as they are all highly pathogenic to humans or livestock, their agents originated from bats, and two of them originated in China. Thus, it is highly likely that future SARS- or MERS-like coronavirus outbreaks will originate from bats, and there is an increased probability that this will occur in China. Therefore, the investigation of bat coronaviruses becomes an urgent issue for the detection of early warning signs, which in turn minimizes the impact of such future outbreaks in China. The purpose of the review is to summarize the current knowledge on viral diversity, reservoir hosts, and the geographical distributions of bat coronaviruses in China, and eventually we aim to predict virus hotspots and their cross-species transmission potential.

Discovery and Sequence Analysis of Four Deltacoronaviruses from Birds in the Middle East Reveal Interspecies Jumping with Recombination as a Potential Mechanism for Avian-to-Avian and Avian-to-Mammalian Transmission

The emergence of Middle East respiratory syndrome showed once again that coronaviruses (CoVs) in animals are potential source for epidemics in humans. To explore the diversity of deltacoronaviruses in animals in the Middle East, we tested fecal samples from 1,356 mammals and birds in Dubai, The United Arab Emirates. Four novel deltacoronaviruses were detected from eight birds of four species by reverse transcription-PCR (RT-PCR): FalCoV UAE-HKU27 from a falcon, HouCoV UAE-HKU28 from a houbara bustard, PiCoV UAE-HKU29 from a pigeon, and QuaCoV UAE-HKU30 from five quails. Complete genome sequencing showed that FalCoV UAE-HKU27, HouCoV UAE-HKU28, and PiCoV UAE-HKU29 belong to the same CoV species, suggesting recent interspecies transmission between falcons and their prey, houbara bustards and pigeons, possibly along the food chain. Western blotting detected specific anti-FalCoV UAE-HKU27 antibodies in 33 (75%) of 44 falcon serum samples, supporting genuine infection in falcons after virus acquisition. QuaCoV UAE-HKU30 belongs to the same CoV species as porcine coronavirus HKU15 (PorCoV HKU15) and sparrow coronavirus HKU17 (SpCoV HKU17), discovered previously from swine and tree sparrows, respectively, supporting avian-to-swine transmission. Recombination involving the spike protein is common among deltacoronaviruses, which may facilitate cross-species transmission. FalCoV UAE-HKU27, HouCoV UAE-HKU28, and PiCoV UAE-HKU29 originated from recombination between white-eye coronavirus HKU16 (WECoV HKU16) and magpie robin coronavirus HKU18 (MRCoV HKU18), QuaCoV UAE-HKU30 from recombination between PorCoV HKU15/SpCoV HKU17 and munia coronavirus HKU13 (MunCoV HKU13), and PorCoV HKU15 from recombination between SpCoV HKU17 and bulbul coronavirus HKU11 (BuCoV HKU11). Birds in the Middle East are hosts for diverse deltacoronaviruses with potential for interspecies transmission.IMPORTANCE During an attempt to explore the diversity of deltacoronaviruses among mammals and birds in Dubai, four novel deltacoronaviruses were detected in fecal samples from eight birds of four different species: FalCoV UAE-HKU27 from a falcon, HouCoV UAE-HKU28 from a houbara bustard, PiCoV UAE-HKU29 from a pigeon, and QuaCoV UAE-HKU30 from five quails. Genome analysis revealed evidence of recent interspecies transmission between falcons and their prey, houbara bustards and pigeons, possibly along the food chain, as well as avian-to-swine transmission. Recombination, which is known to occur frequently in some coronaviruses, was also common among these deltacoronaviruses and occurred predominantly at the spike region. Such recombination, involving the receptor binding protein, may contribute to the emergence of new viruses capable of infecting new hosts. Birds in the Middle East are hosts for diverse deltacoronaviruses with potential for interspecies transmission.

Newly emerged porcine enteric alphacoronavirus in southern China: Identification, origin and evolutionary history analysis

Coronaviruses have a wide host range and can cause a variety of diseases with varying severity in different animals. Several enteric coronaviruses have been identified that are associated with diarrhea in swine and that have caused substantial economic losses. In this study, a newly emerged porcine enteric alphacoronavirus (PEAV), PEAV-GD-CH/2017, was identified from suckling piglets with diarrhea in southern China, and a full-length genome sequence of PEAV was obtained for systematic analysis. The novel PEAV sequence was most identical to that of bat-HKU2, and the differences between them were comprehensively compared, especially the uniform features of the S protein, which was shown to have a close relationship with betacoronaviruses and to perhaps represent unrecognized betacoronaviruses. In addition, Bayesian analysis was conducted to address the origin of PEAV, and the divergence time between PEAV and bat-HKU2 was estimated at 1926, which indicates that PEAV is not newly emerged and may have circulated in swine herds for several decades since the interspecies transmission of this coronavirus from bat to swine. The evolutionary rate of coronaviruses was estimated to be 1.93 × 10⁻⁴ substitutions per site per year for the RdRp gene in our analysis. For the origin of PEAV, we suspect that it is the result of the interspecies transmission of bat-HKU2 from bat to swine. Our results provide valuable information about the uniform features, origin and evolution of the novel PEAV, which will facilitate further investigations of this newly emerged pathogen.

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Identify and sequence a PEAV strain from suckling piglets with diarrhea

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The S protein of PEAV may recombination from unrecognized beta-CoV.

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The novel PEAV was emerged approximately at 1926 based on Bayesian analysis.

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PEAV origin from the interspecies transmission of bat-HKU2 from bat to swine

Rapid detection of MERS coronavirus-like viruses in bats: pote1ntial for tracking MERS coronavirus transmission and animal origin

Recently, we developed a monoclonal antibody-based rapid nucleocapsid protein detection assay for diagnosis of MERS coronavirus (MERS-CoV) in humans and dromedary camels. In this study, we examined the usefulness of this assay to detect other lineage C betacoronaviruses closely related to MERS-CoV in bats. The rapid MERS-CoV nucleocapsid protein detection assay was tested positive in 24 (88.9%) of 27 Tylonycteris bat CoV HKU4 (Ty-BatCoV-HKU4) RNA-positive alimentary samples of Tylonycteris pachypus and 4 (19.0%) of 21 Pipistrellus bat CoV HKU5 (Pi-BatCoV-HKU5) RNA-positive alimentary samples of Pipistrellus abramus. There was significantly more Ty-BatCoV-HKU4 RNA-positive alimentary samples than Pi-BatCoV-HKU5 RNA-positive alimentary samples that were tested positive by the rapid MERS-CoV nucleocapsid protein detection assay (P < 0.001 by Chi-square test). The rapid assay was tested negative in all 51 alimentary samples RNA-positive for alphacoronaviruses (Rhinolophus bat CoV HKU2, Myotis bat CoV HKU6, Miniopterus bat CoV HKU8 and Hipposideros batCoV HKU10) and 32 alimentary samples positive for lineage B (SARS-related Rhinolophus bat CoV HKU3) and lineage D (Rousettus bat CoV HKU9) betacoronaviruses. No significant difference was observed between the viral loads of Ty-BatCoV-HKU4/Pi-BatCoV-HKU5 RNA-positive alimentary samples that were tested positive and negative by the rapid test (Mann-Witney U test). The rapid MERS-CoV nucleocapsid protein detection assay is able to rapidly detect lineage C betacoronaviruses in bats. It detected significantly more Ty-BatCoV-HKU4 than Pi-BatCoV-HKU5 because MERS-CoV is more closely related to Ty-BatCoV-HKU4 than Pi-BatCoV-HKU5. This assay will facilitate rapid on-site mass screening of animal samples for ancestors of MERS-CoV and tracking transmission in the related bat species.

Discovery of a Highly Divergent Coronavirus in the Asian House Shrew from China Illuminates the Origin of the Alphacoronaviruses

Although shrews are one of the largest groups of mammals, little is known about their role in the evolution and transmission of viral pathogens, including coronaviruses (CoVs). We captured 266 Asian house shrews (Suncus murinus) in Jiangxi and Zhejiang Provinces, China, during 2013 to 2015. CoV RNA was detected in 24 Asian house shrews, with an overall prevalence of 9.02%. Complete viral genome sequences were successfully recovered from the RNA-positive samples. The newly discovered shrew CoV fell into four lineages reflecting their geographic origins, indicative of largely allopatric evolution. Notably, these viruses were most closely related to alphacoronaviruses but sufficiently divergent that they should be considered a novel member of the genus Alphacoronavirus, which we denote Wénchéng shrew virus (WESV). Phylogenetic analysis revealed that WESV was a highly divergent member of the alphacoronaviruses and, more dramatically, that the S gene of WESV fell in a cluster that was genetically distinct from that of known coronaviruses. The divergent position of WESV suggests that coronaviruses have a long association with Asian house shrews. In addition, the genome of WESV contains a distinct NS7 gene that exhibits no sequence similarity to genes of any known viruses. Together, these data suggest that shrews are natural reservoirs for coronaviruses and may have played an important and long-term role in CoV evolution.IMPORTANCE The subfamily Coronavirinae contains several notorious human and animal pathogens, including severe acute respiratory syndrome coronavirus, Middle East respiratory syndrome coronavirus, and porcine epidemic diarrhea virus. Because of their genetic diversity and phylogenetic relationships, it has been proposed that the alphacoronaviruses likely have their ultimate ancestry in the viruses residing in bats. Here, we describe a novel alphacoronavirus (Wénchéng shrew virus [WESV]) that was sampled from Asian house shrews in China. Notably, WESV is a highly divergent member of the alphacoronaviruses and possesses an S gene that is genetically distinct from those of all known coronaviruses. In addition, the genome of WESV contains a distinct NS7 gene that exhibits no sequence similarity to those of any known viruses. Together, these data suggest that shrews are important and longstanding hosts for coronaviruses that merit additional research and surveillance.

Extensive diversity of coronaviruses in bats from China

To help reveal the diversity and evolution of bat coronaviruses we collected 1067 bats from 21 species in China. A total of 73 coronaviruses (32 alphacoronaviruses and 41 betacoronaviruses) were identified in these bats, with an overall prevalence of 6.84%. All newly-identified betacoronaviruses were SARS-related Rhinolophus bat coronaviruses (SARSr-Rh-BatCoV). Importantly, with the exception of the S gene, the genome sequences of the SARSr-Rh-BatCoVs sampled in Guizhou province were closely related to SARS-related human coronavirus. Additionally, the newly-identified alphacoronaviruses exhibited high genetic diversity and some may represent novel species. Our phylogenetic analyses also provided insights into the transmission of these viruses among bat species, revealing a general clustering by geographic location rather than by bat species. Inter-species transmission among bats from the same genus was also commonplace in both the alphacoronaviruses and betacoronaviruses. Overall, these data suggest that high contact rates among specific bat species enable the acquisition and spread of coronaviruses.

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32 alpha-CoVs and 41 beta-CoVs were identified in bats sampled from China.

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SARSr-Rh-BatCoVs from Guizhou province were closely related to SARS-CoV.

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Some of the newly identified CoVs may be novel species in the genus Alphacoronavirus.

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High contact rates among some bat species enable the acquisition and spread of CoVs.

Middle East respiratory syndrome (MERS) coronavirus and dromedaries

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Middle East Respiratory Syndrome (MERS) is a zoonotic viral disease transmissible from dromedaries to human beings.

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MERS coronavirus (MERS-CoV) infection in dromedaries is usually asymptomatic but mild respiratory signs may occur.

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No MERS-CoV or antibodies against the virus have been detected in camelids other than dromedaries.

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Dromedaries acquire MERS-CoV at less than 1 year of age and 100% of adult dromedaries are seropositive for the virus.

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MERS-CoV in dromedaries is detected by virus isolation, quantitative reverse transcriptase-PCR or antigen detection.

Middle East Respiratory Syndrome (MERS) is a zoonotic viral disease that can be transmitted from dromedaries to human beings. More than 1500 cases of MERS have been reported in human beings to date. Although MERS has been associated with 30% case fatality in human beings, MERS coronavirus (MERS-CoV) infection in dromedaries is usually asymptomatic. In rare cases, dromedaries may develop mild respiratory signs. No MERS-CoV or antibodies against the virus have been detected in camelids other than dromedaries. MERS-CoV is mainly acquired in dromedaries when they are less than 1 year of age, and the proportion of seropositivity increases with age to a seroprevalence of 100% in adult dromedaries. Laboratory diagnosis of MERS-CoV infection in dromedaries can be achieved through virus isolation using Vero cells, RNA detection by real-time quantitative reverse transcriptase-PCR and antigen detection using respiratory specimens or serum. Rapid nucleocapsid antigen detection using a lateral flow platform allows efficient screening of dromedaries carrying MERS-CoV. In addition to MERS-CoV, which is a lineage C virus in the Betacoronavirus (betaCoV) genus, a lineage B betaCoV and a virus in the Alphacoronavirus (alphaCoV) genus have been detected in dromedaries. Dromedary CoV UAE-HKU23 is closely related to human CoV OC43, whereas the alphaCoV has not been detected in human beings to date.

Genetic diversity of coronaviruses in bats in Lao PDR and Cambodia

South-East Asia is a hot spot for emerging zoonotic diseases, and bats have been recognized as hosts for a large number of zoonotic viruses such as Severe Acute Respiratory Syndrome (SARS), responsible for acute respiratory syndrome outbreaks. Thus, it is important to expand our knowledge of the presence of viruses in bats which could represent a risk to humans. Coronaviruses (CoVs) have been reported in bat species from Thailand, China, Indonesia, Taiwan and the Philippines. However no such work was conducted in Cambodia or Lao PDR. Between 2010 and 2013, 1965 bats were therefore sampled at interfaces with human populations in these two countries. They were tested for the presence of coronavirus by consensus reverse transcription-PCR assay. A total of 93 samples (4.7%) from 17 genera of bats tested positive. Sequence analysis revealed the presence of potentially 37 and 56 coronavirus belonging to alpha-coronavirus (αCoV) and beta-CoV (βCoV), respectively. The βCoVs group is known to include some coronaviruses highly pathogenic to human, such as SARS-CoV and MERS-CoV. All coronavirus sequences generated from frugivorous bats (family Pteropodidae) (n = 55) clustered with other bat βCoVs of lineage D, whereas one coronavirus from Pipistrellus coromandra fell in the lineage C of βCoVs which also includes the MERS-CoV. αCoVs were all detected in various genera of insectivorous bats and clustered with diverse bat αCoV sequences previously published. A closely related strain of PEDV, responsible for severe diarrhea in pigs (PEDV-CoV), was detected in 2 Myotis bats. We highlighted the presence and the high diversity of coronaviruses circulating in bats from Cambodia and Lao PDR. Three new bat genera and species were newly identified as host of coronaviruses, namely Macroglossus sp., Megaerops niphanae and Myotis horsfieldii

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Coronaviruses detected in bats from Lao PDR and Cambodia.

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High diversity of αCoVs and βCoVs circulating in bats in Cambodia and Lao PDR.

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One strain of βCoV, a new member of the MERS-CoV sister-clade, detected from Pipistrellus coromandra.

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A αCoV strain genetically related to PEDV-CoV, detected from Myotis horsfieldii.

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CoVs detected for the first time in Megaerops niphanae, Myotis horsfieldii and Macroglossus sp.

A Bat-Derived Putative Cross-Family Recombinant Coronavirus with a Reovirus Gene

The emergence of severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002 and Middle East respiratory syndrome coronavirus (MERS-CoV) in 2012 has generated enormous interest in the biodiversity, genomics and cross-species transmission potential of coronaviruses, especially those from bats, the second most speciose order of mammals. Herein, we identified a novel coronavirus, provisionally designated Rousettus bat coronavirus GCCDC1 (Ro-BatCoV GCCDC1), in the rectal swab samples of Rousettus leschenaulti bats by using pan-coronavirus RT-PCR and next-generation sequencing. Although the virus is similar to Rousettus bat coronavirus HKU9 (Ro-BatCoV HKU9) in genome characteristics, it is sufficiently distinct to be classified as a new species according to the criteria defined by the International Committee of Taxonomy of Viruses (ICTV). More striking was that Ro-BatCoV GCCDC1 contained a unique gene integrated into the 3'-end of the genome that has no homologs in any known coronavirus, but which sequence and phylogeny analyses indicated most likely originated from the p10 gene of a bat orthoreovirus. Subgenomic mRNA and cellular-level observations demonstrated that the p10 gene is functional and induces the formation of cell syncytia. Therefore, here we report a putative heterologous inter-family recombination event between a single-stranded, positive-sense RNA virus and a double-stranded segmented RNA virus, providing insights into the fundamental mechanisms of viral evolution.

Detection of Severe Acute Respiratory Syndrome-Like, Middle East Respiratory Syndrome-Like Bat Coronaviruses and Group H Rotavirus in Faeces of Korean Bats

Bat species around the world have recently been recognized as major reservoirs of several zoonotic viruses, such as severe acute respiratory syndrome coronavirus (SARS‐CoV), Middle East respiratory syndrome coronavirus (MERS‐CoV), Nipah virus and Hendra virus. In this study, consensus primer‐based reverse transcriptase polymerase chain reactions (RT‐PCRs) and high‐throughput sequencing were performed to investigate viruses in bat faecal samples collected at 11 natural bat habitat sites from July to December 2015 in Korea. Diverse coronaviruses were first detected in Korean bat faeces, including alphacoronaviruses, SARS‐CoV‐like and MERS‐CoV‐like betacoronaviruses. In addition, we identified a novel bat rotavirus belonging to group H rotavirus which has only been described in human and pigs until now. Therefore, our results suggest the need for continuing surveillance and additional virological studies in domestic bat.

Genetic diversity of coronaviruses in Miniopterus fuliginosus bats

Coronaviruses, such as severe acute respiratory syndrome coronavirus and Middle East respiratory syndrome coronavirus, pose significant public health threats. Bats have been suggested to act as natural reservoirs for both these viruses, and periodic monitoring of coronaviruses in bats may thus provide important clues about emergent infectious viruses. The Eastern bent-wing bat Miniopterus fuliginosus is distributed extensively throughout China. We therefore analyzed the genetic diversity of coronaviruses in samples of M. fuliginosus collected from nine Chinese provinces during 2011–2013. The only coronavirus genus found was Alphacoronavirus. We established six complete and five partial genomic sequences of alphacoronaviruses, which revealed that they could be divided into two distinct lineages, with close relationships to coronaviruses in Miniopterus magnater and Miniopterus pusillus. Recombination was confirmed by detecting putative breakpoints of Lineage 1 coronaviruses in M. fuliginosus and M. pusillus (Wu et al., 2015), which supported the results of topological and phylogenetic analyses. The established alphacoronavirus genome sequences showed high similarity to other alphacoronaviruses found in other Miniopterus species, suggesting that their transmission in different Miniopterus species may provide opportunities for recombination with different alphacoronaviruses. The genetic information for these novel alphacoronaviruses will improve our understanding of the evolution and genetic diversity of coronaviruses, with potentially important implications for the transmission of human diseases.

Coexistence of multiple coronaviruses in several bat colonies in an abandoned mineshaft

Since the 2002–2003 severe acute respiratory syndrome (SARS) outbreak prompted a search for the natural reservoir of the SARS coronavirus, numerous alpha- and betacoronaviruses have been discovered in bats around the world. Bats are likely the natural reservoir of alpha- and betacoronaviruses, and due to the rich diversity and global distribution of bats, the number of bat coronaviruses will likely increase. We conducted a surveillance of coronaviruses in bats in an abandoned mineshaft in Mojiang County, Yunnan Province, China, from 2012–2013. Six bat species were frequently detected in the cave: Rhinolophus sinicus, Rhinolophus affinis, Hipposideros pomona, Miniopterus schreibersii, Miniopterus fuliginosus, and Miniopterus fuscus. By sequencing PCR products of the coronavirus RNA-dependent RNA polymerase gene (RdRp), we found a high frequency of infection by a diverse group of coronaviruses in different bat species in the mineshaft. Sequenced partial RdRp fragments had 80%–99% nucleic acid sequence identity with well-characterized Alphacoronavirus species, including BtCoV HKU2, BtCoV HKU8, and BtCoV1, and unassigned species BtCoV HKU7 and BtCoV HKU10. Additionally, the surveillance identified two unclassified betacoronaviruses, one new strain of SARS-like coronavirus, and one potentially new betacoronavirus species. Furthermore, coronavirus co-infection was detected in all six bat species, a phenomenon that fosters recombination and promotes the emergence of novel virus strains. Our findings highlight the importance of bats as natural reservoirs of coronaviruses and the potentially zoonotic source of viral pathogens.

Detection and characterization of diverse alpha- and betacoronaviruses from bats in China

Bats have been implicated as important reservoir hosts of alpha- and betacoronaviruses. In this study, diverse coronaviruses (CoVs) were detected in 50 of 951 (positive rate 5.3%) intestinal specimens of eight bat species collected in four provinces and the Tibet Autonomous Region of China by pan-coronavirus RT-PCR screening. Based on 400-nt RNA-dependent RNA polymerase (RdRP) sequence analysis, eight belonged to genus Alphacoronavirus and 42 to Betacoronavirus. Among the 50 positive specimens, thirteen gave rise to CoV full-length RdRP gene amplification for further sequence comparison, of which three divergent sequences (two from a unreported province) were subjected to full genome sequencing. Two complete genomes of betacoronaviruses (JTMC15 and JPDB144) and one nearly-complete genome of alphacoronavirus (JTAC2) were sequenced and their genomic organization predicted. The present study has identified additional numbers of genetically diverse bat-borne coronaviruses with a wide distribution in China. Two new species of bat CoV, identified through sequence comparison and phylogenetic analysis, are proposed.

Origins and Evolution of Hepatitis B Virus and Hepatitis D Virus

Members of the family Hepadnaviridae fall into two subgroups: mammalian and avian. The detection of endogenous avian hepadnavirus DNA integrated into the genomes of zebra finches has revealed a deep evolutionary origin of hepadnaviruses that was not previously recognized, dating back at least 40 million and possibly >80 million years ago. The nonprimate mammalian members of the Hepadnaviridae include the woodchuck hepatitis virus (WHV), the ground squirrel hepatitis virus, and arctic squirrel hepatitis virus, as well as a number of members of the recently described bat hepatitis virus. The identification of hepatitis B viruses (HBVs) in higher primates, such as chimpanzee, gorilla, orangutan, and gibbons that cluster with the human HBV, as well as a number of recombinant forms between humans and primates, further implies a more complex origin of this virus. We discuss the current theories of the origin and evolution of HBV and propose a model that includes cross-species transmissions and subsequent recombination events on a genetic backbone of genotype C HBV infection. The hepatitis delta virus (HDV) is a defective RNA virus requiring the presence of the HBV for the completion of its life cycle. The origins of this virus remain unknown, although some recent studies have suggested an ancient African radiation. The age of the association between HDV and HBV is also unknown.

Severe acute respiratory syndrome coronavirus E protein transports calcium ions and activates the NLRP3 inflammasome

Severe acute respiratory syndrome coronavirus (SARS-CoV) envelope (E) protein is a viroporin involved in virulence. E protein ion channel (IC) activity is specifically correlated with enhanced pulmonary damage, edema accumulation and death. IL-1β driven proinflammation is associated with those pathological signatures, however its link to IC activity remains unknown. In this report, we demonstrate that SARS-CoV E protein forms protein–lipid channels in ERGIC/Golgi membranes that are permeable to calcium ions, a highly relevant feature never reported before. Calcium ions together with pH modulated E protein pore charge and selectivity. Interestingly, E protein IC activity boosted the activation of the NLRP3 inflammasome, leading to IL-1β overproduction. Calcium transport through the E protein IC was the main trigger of this process. These findings strikingly link SARS-CoV E protein IC induced ionic disturbances at the cell level to immunopathological consequences and disease worsening in the infected organism.

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SARS-CoV E protein forms calcium ion channels, a novel highly relevant function.

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Transport of calcium ions through E protein channel stimulates the inflammasome.

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Inflammasome derived exacerbated proinflammation causes SARS worsening.

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E protein ion channel and its driven proinflammation may be targets to treat SARS.

Diversity of coronavirus in bats from Eastern Thailand

BACKGROUND

Bats are reservoirs for a diverse range of coronaviruses (CoVs), including those closely related to human pathogens such as Severe Acute Respiratory Syndrome (SARS) CoV and Middle East Respiratory Syndrome CoV. There are approximately 139 bat species reported to date in Thailand, of which two are endemic species. Due to the zoonotic potential of CoVs, standardized surveillance efforts to characterize viral diversity in wildlife are imperative.

FINDINGS

A total of 626 bats from 19 different bat species were individually sampled from 5 provinces in Eastern Thailand between 2008 and 2013 (84 fecal and 542 rectal swabs). Samples collected (either fresh feces or rectal swabs) were placed directly into RNA stabilization reagent, transported on ice within 24 hours and preserved at -80°C until further analysis. CoV RNA was detected in 47 specimens (7.6%), from 13 different bat species, using broadly reactive consensus PCR primers targeting the RNA-Dependent RNA Polymerase gene designed to detect all CoVs. Thirty seven alphacoronaviruses, nine lineage D betacoronaviruses, and one lineage B betacoronavirus (SARS-CoV related) were identified. Six new bat CoV reservoirs were identified in our study, namely Cynopterus sphinx, Taphozous melanopogon, Hipposideros lekaguli, Rhinolophus shameli, Scotophilus heathii and Megaderma lyra.

CONCLUSIONS

CoVs from the same genetic lineage were found in different bat species roosting in similar or different locations. These data suggest that bat CoV lineages are not strictly concordant with their hosts. Our phylogenetic data indicates high diversity and a complex ecology of CoVs in bats sampled from specific areas in eastern regions of Thailand. Further characterization of additional CoV genes may be useful to better describe the CoV divergence.

Diversity of coronavirus in bats from Eastern Thailand

Background

Bats are reservoirs for a diverse range of coronaviruses (CoVs), including those closely related to human pathogens such as Severe Acute Respiratory Syndrome (SARS) CoV and Middle East Respiratory Syndrome CoV. There are approximately 139 bat species reported to date in Thailand, of which two are endemic species. Due to the zoonotic potential of CoVs, standardized surveillance efforts to characterize viral diversity in wildlife are imperative.

Findings

A total of 626 bats from 19 different bat species were individually sampled from 5 provinces in Eastern Thailand between 2008 and 2013 (84 fecal and 542 rectal swabs). Samples collected (either fresh feces or rectal swabs) were placed directly into RNA stabilization reagent, transported on ice within 24 hours and preserved at −80°C until further analysis. CoV RNA was detected in 47 specimens (7.6%), from 13 different bat species, using broadly reactive consensus PCR primers targeting the RNA-Dependent RNA Polymerase gene designed to detect all CoVs. Thirty seven alphacoronaviruses, nine lineage D betacoronaviruses, and one lineage B betacoronavirus (SARS-CoV related) were identified. Six new bat CoV reservoirs were identified in our study, namely Cynopterus sphinx, Taphozous melanopogon, Hipposideros lekaguli, Rhinolophus shameli, Scotophilus heathii and Megaderma lyra.

Conclusions

CoVs from the same genetic lineage were found in different bat species roosting in similar or different locations. These data suggest that bat CoV lineages are not strictly concordant with their hosts. Our phylogenetic data indicates high diversity and a complex ecology of CoVs in bats sampled from specific areas in eastern regions of Thailand. Further characterization of additional CoV genes may be useful to better describe the CoV divergence.

Severe acute respiratory syndrome coronaviruses with mutations in the E protein are attenuated and promising vaccine candidates

Severe acute respiratory syndrome coronavirus (SARS-CoV) causes a respiratory disease with a mortality rate of 10%. A mouse-adapted SARS-CoV (SARS-CoV-MA15) lacking the envelope (E) protein (rSARS-CoV-MA15-ΔE) is attenuated in vivo. To identify E protein regions and host responses that contribute to rSARS-CoV-MA15-ΔE attenuation, several mutants (rSARS-CoV-MA15-E*) containing point mutations or deletions in the amino-terminal or the carboxy-terminal regions of the E protein were generated. Amino acid substitutions in the amino terminus, or deletion of regions in the internal carboxy-terminal region of E protein, led to virus attenuation. Attenuated viruses induced minimal lung injury, diminished limited neutrophil influx, and increased CD4(+) and CD8(+) T cell counts in the lungs of BALB/c mice, compared to mice infected with the wild-type virus. To analyze the host responses leading to rSARS-CoV-MA15-E* attenuation, differences in gene expression elicited by the native and mutant viruses in the lungs of infected mice were determined. Expression levels of a large number of proinflammatory cytokines associated with lung injury were reduced in the lungs of rSARS-CoV-MA15-E*-infected mice, whereas the levels of anti-inflammatory cytokines were increased, both at the mRNA and protein levels. These results suggested that the reduction in lung inflammation together with a more robust antiviral T cell response contributed to rSARS-CoV-MA15-E* attenuation. The attenuated viruses completely protected mice against challenge with the lethal parental virus, indicating that these viruses are promising vaccine candidates.

IMPORTANCE

Human coronaviruses are important zoonotic pathogens. SARS-CoV caused a worldwide epidemic infecting more than 8,000 people with a mortality of around 10%. Therefore, understanding the virulence mechanisms of this pathogen and developing efficacious vaccines are of high importance to prevent epidemics from this and other human coronaviruses. Previously, we demonstrated that a SARS-CoV lacking the E protein was attenuated in vivo. Here, we show that small deletions and modifications within the E protein led to virus attenuation, manifested by minimal lung injury, limited neutrophil influx to the lungs, reduced expression of proinflammatory cytokines, increased anti-inflammatory cytokine levels, and enhanced CD4(+) and CD8(+) T cell counts in vivo, suggesting that these phenomena contribute to virus attenuation. The attenuated mutants fully protected mice from challenge with virulent virus. These studies show that mutations in the E protein are not well tolerated and indicate that this protein is an excellent target for vaccine development.

Identification of an unclassified paramyxovirus in Coleura afra: a potential case of host specificity

Bats are known to harbor multiple paramyxoviruses. Despite the creation of two new genera, Aquaparamyxovirus and Ferlavirus, to accommodate this increasing diversity, several recently isolated or characterized viruses remain unclassified beyond the subfamily level. In the present study, among 985 bats belonging to 6 species sampled in the Belinga caves of Gabon, RNA of an unclassified paramyxovirus (Belinga bat virus, BelPV) was discovered in 14 African sheath-tailed bats (Coleura afra), one of which exhibited several hemorrhagic lesions at necropsy, and viral sequence was obtained in two animals. Phylogenetically, BelPV is related to J virus and Beilong virus (BeiPV), two other unclassified paramyxoviruses isolated from rodents. In the diseased BelPV-infected C. afra individual, high viral load was detected in the heart, and the lesions were consistent with those reported in wild rodents and mice experimentally infected by J virus. BelPV was not detected in other tested bat species sharing the same roosting sites and living in very close proximity with C. afra in the two caves sampled, suggesting that this virus may be host-specific for C. afra. The mode of transmission of this paramyxovirus in bat populations remains to be discovered.

Coronavirus nonstructural protein 1: Common and distinct functions in the regulation of host and viral gene expression

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Novel strategies to inhibit host gene expression by coronavirus nonstructural protein 1.

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Summarizes the conserved and divergent functions of Alpha and Betacoronavirus nsp1.

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Provides a mechanistic insight into the unique properties of SARS coronavirus nsp1.

The recent emergence of two highly pathogenic human coronaviruses (CoVs), severe acute respiratory syndrome CoV and Middle East respiratory syndrome CoV, has ignited a strong interest in the identification of viral factors that determine the virulence and pathogenesis of CoVs. The nonstructural protein 1 (nsp1) of CoVs has attracted considerable attention in this regard as a potential virulence factor and a target for CoV vaccine development because of accumulating evidence that point to its role in the downregulation of host innate immune responses to CoV infection. Studies have revealed both functional conservation and mechanistic divergence among the nsp1 of different mammalian CoVs in perturbing host gene expression and antiviral responses. This review summarizes the current knowledge about the biological functions of CoV nsp1 that provides an insight into the novel strategies utilized by this viral protein to modulate host and viral gene expression during CoV infection.

From SARS to MERS: crystallographic studies on coronaviral proteases enable antiviral drug design

This review focuses on the important contributions that macromolecular crystallography has made over the past 12 years to elucidating structures and mechanisms of the essential proteases of coronaviruses, the main protease (M(pro) ) and the papain-like protease (PL(pro) ). The role of X-ray crystallography in structure-assisted drug discovery against these targets is discussed. Aspects dealt with in this review include the emergence of the SARS coronavirus in 2002-2003 and of the MERS coronavirus 10 years later and the origins of these viruses. The crystal structure of the free SARS coronavirus M(pro) and its dependence on pH is discussed, as are efforts to design inhibitors on the basis of these structures. The mechanism of maturation of the enzyme from the viral polyprotein is still a matter of debate. The crystal structure of the SARS coronavirus PL(pro) and its complex with ubiquitin is also discussed, as is its orthologue from MERS coronavirus. Efforts at predictive structure-based inhibitor development for bat coronavirus M(pro) s to increase the preparedness against zoonotic transmission to man are described as well. The paper closes with a brief discussion of structure-based discovery of antivirals in an academic setting.

Severe acute respiratory syndrome coronavirus envelope protein ion channel activity promotes virus fitness and pathogenesis

Deletion of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) envelope (E) gene attenuates the virus. E gene encodes a small multifunctional protein that possesses ion channel (IC) activity, an important function in virus-host interaction. To test the contribution of E protein IC activity in virus pathogenesis, two recombinant mouse-adapted SARS-CoVs, each containing one single amino acid mutation that suppressed ion conductivity, were engineered. After serial infections, mutant viruses, in general, incorporated compensatory mutations within E gene that rendered active ion channels. Furthermore, IC activity conferred better fitness in competition assays, suggesting that ion conductivity represents an advantage for the virus. Interestingly, mice infected with viruses displaying E protein IC activity, either with the wild-type E protein sequence or with the revertants that restored ion transport, rapidly lost weight and died. In contrast, mice infected with mutants lacking IC activity, which did not incorporate mutations within E gene during the experiment, recovered from disease and most survived. Knocking down E protein IC activity did not significantly affect virus growth in infected mice but decreased edema accumulation, the major determinant of acute respiratory distress syndrome (ARDS) leading to death. Reduced edema correlated with lung epithelia integrity and proper localization of Na⁺/K⁺ ATPase, which participates in edema resolution. Levels of inflammasome-activated IL-1β were reduced in the lung airways of the animals infected with viruses lacking E protein IC activity, indicating that E protein IC function is required for inflammasome activation. Reduction of IL-1β was accompanied by diminished amounts of TNF and IL-6 in the absence of E protein ion conductivity. All these key cytokines promote the progression of lung damage and ARDS pathology. In conclusion, E protein IC activity represents a new determinant for SARS-CoV virulence.

Several highly pathogenic viruses encode small transmembrane proteins with ion-conduction properties named viroporins. Viroporins are generally involved in virus production and maturation processes, which many times are achieved by altering the ion homeostasis of cell organelles. Cells have evolved mechanisms to sense these imbalances in ion concentrations as a danger signal, and consequently trigger the innate immune system. Recently, it has been demonstrated that viroporins are inducers of cytosolic macromolecular complexes named inflammasomes that trigger the activation of key inflammatory cytokines such as IL-1β. The repercussions of this system in viral pathogenesis or disease outcome are currently being explored. SARS-CoV infection induces an uncontrolled inflammatory response leading to pulmonary damage, edema accumulation, severe hypoxemia and eventually death. In this study, we report that SARS-CoV E protein ion channel activity is a determinant of virulence, as the elimination of this function attenuated the virus, reducing the harmful inflammatory cytokine burst produced after infection, in which inflammasome activation plays a critical role. This led to less pulmonary damage and to disease resolution. These novel findings may be of relevance for other viral infections and can possibly be translated in order to find therapies for their associated diseases.

Identification of diverse alphacoronaviruses and genomic characterization of a novel severe acute respiratory syndrome-like coronavirus from bats in China

Although many severe acute respiratory syndrome-like coronaviruses (SARS-like CoVs) have been identified in bats in China, Europe, and Africa, most have a genetic organization significantly distinct from human/civet SARS CoVs in the receptor-binding domain (RBD), which mediates receptor binding and determines the host spectrum, resulting in their failure to cause human infections and making them unlikely progenitors of human/civet SARS CoVs. Here, a viral metagenomic analysis of 268 bat rectal swabs collected from four counties in Yunnan Province has identified hundreds of sequences relating to alpha- and betacoronaviruses. Phylogenetic analysis based on a conserved region of the RNA-dependent RNA polymerase gene revealed that alphacoronaviruses had diversities with some obvious differences from those reported previously. Full genomic analysis of a new SARS-like CoV from Baoshan (LYRa11) showed that it was 29,805 nucleotides (nt) in length with 13 open reading frames (ORFs), sharing 91% nucleotide identity with human/civet SARS CoVs and the most recently reported SARS-like CoV Rs3367, while sharing 89% with other bat SARS-like CoVs. Notably, it showed the highest sequence identity with the S gene of SARS CoVs and Rs3367, especially in the RBD region. Antigenic analysis showed that the S1 domain of LYRa11 could be efficiently recognized by SARS-convalescent human serum, indicating that LYRa11 is a novel virus antigenically close to SARS CoV. Recombination analyses indicate that LYRa11 is likely a recombinant descended from parental lineages that had evolved into a number of bat SARS-like CoVs.

IMPORTANCE

Although many severe acute respiratory syndrome-like coronaviruses (SARS-like CoVs) have been discovered in bats worldwide, there are significant different genic structures, particularly in the S1 domain, which are responsible for host tropism determination, between bat SARS-like CoVs and human SARS CoVs, indicating that most reported bat SARS-like CoVs are not the progenitors of human SARS CoV. We have identified diverse alphacoronaviruses and a close relative (LYRa11) to SARS CoV in bats collected in Yunnan, China. Further analysis showed that alpha- and betacoronaviruses have different circulation and transmission dynamics in bat populations. Notably, full genomic sequencing and antigenic study demonstrated that LYRa11 is phylogenetically and antigenically closely related to SARS CoV. Recombination analyses indicate that LYRa11 is a recombinant from certain bat SARS-like CoVs circulating in Yunnan Province.

A Brief Review: The Z-curve Theory and its Application in Genome Analysis

In theoretical physics, there exist two basic mathematical approaches, algebraic and geometrical methods, which, in most cases, are complementary. In the area of genome sequence analysis, however, algebraic approaches have been widely used, while geometrical approaches have been less explored for a long time. The Z-curve theory is a geometrical approach to genome analysis. The Z-curve is a three-dimensional curve that represents a given DNA sequence in the sense that each can be uniquely reconstructed given the other. The Z-curve, therefore, contains all the information that the corresponding DNA sequence carries. The analysis of a DNA sequence can then be performed through studying the corresponding Z-curve. The Z-curve method has found applications in a wide range of areas in the past two decades, including the identifications of protein-coding genes, replication origins, horizontally-transferred genomic islands, promoters, translational start sides and isochores, as well as studies on phylogenetics, genome visualization and comparative genomics. Here, we review the progress of Z-curve studies from aspects of both theory and applications in genome analysis.

Ecology, evolution and classification of bat coronaviruses in the aftermath of SARS

In 2002/2003, a novel coronavirus (CoV) caused a pandemic, infecting more than 8000 people, of whom nearly 10% died. This virus, termed severe acute respiratory syndrome-CoV was linked to a zoonotic origin from rhinolophid bats in 2005. Since then, numerous studies have described novel bat CoVs, including close relatives of the newly emerging Middle East respiratory syndrome (MERS)-CoV. In this paper we discuss CoV genomic properties and compare different taxonomic approaches in light of the technical difficulties of obtaining full genomic sequences directly from bat specimens. We first present an overview of the available studies on bat CoVs, with details on their chiropteran hosts, then comparatively analyze the increase in bat CoV studies and novel genomic sequences obtained since the SARS pandemic. We then conduct a comprehensive phylogenetic analysis of the genera Alpha- and Betacoronavirus, to show that bats harbour more CoV diversity than other mammalian hosts and are widely represented in most, but not all parts of the tree of mammalian CoVs. We next discuss preliminary evidence for phylogenetic co-segregation of CoVs and bat hosts encompassing the Betacoronavirus clades b and d, with an emphasis on the sampling bias that exists among bat species and other mammals, then present examples of CoVs infecting different hosts on the one hand and viruses apparently confined to host genera on the other. We also demonstrate a geographic bias within available studies on bat CoVs, and identify a critical lack of information from biodiversity hotspots in Africa, Asia and Latin America. We then present evidence for a zoonotic origin of four of the six known human CoVs (HCoV), three of which likely involved bats, namely SARS-CoV, MERS-CoV and HCoV-229E; compare the available data on CoV pathogenesis in bats to that in other mammalian hosts; and discuss hypotheses on the putative insect origins of CoV ancestors. Finally, we suggest caution with conclusions on the zoonotic potential of bat viruses, based only on genomic sequence data, and emphasize the need to preserve these ecologically highly relevant animals. This paper forms part of a symposium in Antiviral Research on "from SARS to MERS: 10years of research on highly pathogenic human coronaviruses".

A decade after SARS: strategies for controlling emerging coronaviruses

Two novel coronaviruses have emerged in humans in the twenty-first century: severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), both of which cause acute respiratory distress syndrome (ARDS) and are associated with high mortality rates. There are no clinically approved vaccines or antiviral drugs available for either of these infections; thus, the development of effective therapeutic and preventive strategies that can be readily applied to new emergent strains is a research priority. In this Review, we describe the emergence and identification of novel human coronaviruses over the past 10 years, discuss their key biological features, including tropism and receptor use, and summarize approaches for developing broadly effective vaccines.

Detection of coronaviruses in bats of various species in Italy

Bats are natural reservoirs for many mammalian coronaviruses, which have received renewed interest after the discovery of the severe acute respiratory syndrome (SARS) and the Middle East respiratory syndrome (MERS) CoV in humans. This study describes the identification and molecular characterization of alphacoronaviruses and betacoronaviruses in bats in Italy, from 2010 to 2012. Sixty-nine faecal samples and 126 carcasses were tested using pan-coronavirus RT-PCR. Coronavirus RNAs were detected in seven faecal samples and nine carcasses. A phylogenetic analysis of RNA-dependent RNA polymerase sequence fragments aided in identifying two alphacoronaviruses from Kuhl's pipistrelle (Pipistrellus kuhlii), three clade 2b betacoronaviruses from lesser horseshoe bats (Rhinolophus hipposideros), and 10 clade 2c betacoronaviruses from Kuhl's pipistrelle, common noctule (Nyctalus noctula), and Savi's pipistrelle (Hypsugo savii). This study fills a substantive gap in the knowledge on bat-CoV ecology in Italy, and extends the current knowledge on clade 2c betacoronaviruses with new sequences obtained from bats that have not been previously described as hosts of these viruses.