Discovery of seven novel Mammalian and avian coronaviruses in the genus deltacoronavirus supports bat coronaviruses as the gene source of alphacoronavirus and betacoronavirus and avian coronaviruses as the gene source of gammacoronavirus and deltacoronavirus

Identification and characterization of a novel paramyxovirus, porcine parainfluenza virus 1, from deceased pigs

We describe the discovery and characterization of a novel paramyxovirus, porcine parainfluenza virus 1 (PPIV-1), from swine. The virus was detected in 12 (3.1 %) of 386 nasopharyngeal and two (0.7 %) of 303 rectal swab samples from 386 deceased pigs by reverse transcription-PCR, with viral loads of up to 10(6) copies ml(-1). Complete genome sequencing and phylogenetic analysis showed that PPIV-1 represented a novel paramyxovirus within the genus Respirovirus, being most closely related to human parainfluenza virus 1 (HPIV-1) and Sendai virus (SeV). In contrast to HPIV-1, PPIV-1 possessed a mRNA editing function in the phosphoprotein gene. Moreover, PPIV-1 was unique among respiroviruses in having two G residues instead of three to five G residues following the A6 run at the editing site. Nevertheless, PPIV-1, HPIV-1 and SeV share common genomic features and may belong to a separate group within the genus Respirovirus. The presence of PPIV-1 in mainly respiratory samples suggests a possible association with respiratory disease, similar to HPIV-1 and SeV.

The emerging novel Middle East respiratory syndrome coronavirus: the "knowns" and "unknowns"

A novel lineage C betacoronavirus, originally named human coronavirus EMC/2012 (HCoV-EMC) and recently renamed Middle East respiratory syndrome coronavirus (MERS-CoV), that is phylogenetically closely related to Tylonycteris bat coronavirus HKU4 and Pipistrellus bat coronavirus HKU5, which we discovered in 2007 from bats in Hong Kong, has recently emerged in the Middle East to cause a severe acute respiratory syndrome (SARS)-like infection in humans. The first laboratory-confirmed case, which involved a 60-year-old man from Bisha, the Kingdom of Saudi Arabia (KSA), who died of rapidly progressive community-acquired pneumonia and acute renal failure, was announced by the World Health Organization (WHO) on September 23, 2012. Since then, a total of 70 cases, including 39 fatalities, have been reported in the Middle East and Europe. Recent clusters involving epidemiologically-linked household contacts and hospital contacts in the Middle East, Europe, and Africa strongly suggested possible human-to-human transmission. Clinical and laboratory research data generated in the past few months have provided new insights into the possible animal reservoirs, transmissibility, and virulence of MERS-CoV, and the optimal laboratory diagnostic options and potential antiviral targets for MERS-CoV-associated infection.

Alphacoronavirus protein 7 modulates host innate immune response

Innate immune response is the first line of antiviral defense resulting, in most cases, in pathogen clearance with minimal clinical consequences. Viruses have developed diverse strategies to subvert host defense mechanisms and increase their survival. In the transmissible gastroenteritis virus (TGEV) as a model, we previously reported that accessory gene 7 counteracts the host antiviral response by associating with the catalytic subunit of protein phosphatase 1 (PP1c). In the present work, the effect of the absence of gene 7 on the host cell, during infection, was further analyzed by transcriptomic analysis. The pattern of gene expression of cells infected with a recombinant mutant TGEV, lacking gene 7 expression (rTGEV-Δ7), was compared to that of cells infected with the parental virus (rTGEV-wt). Genes involved in the immune response, the interferon response, and inflammation were upregulated during TGEV infection in the absence of gene 7. An exacerbated innate immune response during infection with rTGEV-Δ7 virus was observed both in vitro and in vivo. An increase in macrophage recruitment and activation in lung tissues infected with rTGEV-Δ7 virus was observed compared to cells infected with the parental virus. In summary, the absence of protein 7 both in vitro and in vivo led to increased proinflammatory responses and acute tissue damage after infection. In a porcine animal model, which is immunologically similar to humans, we present a novel example of how viral proteins counteract host antiviral pathways to determine the infection outcome and pathogenesis.

Evolutionary dynamics of bovine coronaviruses: natural selection pattern of the spike gene implies adaptive evolution of the strains

Coronaviruses demonstrate great potential for interspecies transmission, including zoonotic outbreaks. Although bovine coronavirus (BCoV) strains are frequently circulating in cattle farms worldwide, causing both enteric and respiratory disease, little is known about their genomic evolution. We sequenced and analysed the full-length spike (S) protein gene of 33 BCoV strains from dairy and feedlot farms collected during outbreaks that occurred from 2002 to 2010 in Sweden and Denmark. Amino acid identities were >97 % for the BCoV strains analysed in this work. These strains formed a clade together with Italian BCoV strains and were highly similar to human enteric coronavirus HECV-4408/US/94. A high similarity was observed between BCoV, canine respiratory coronavirus (CRCoV) and human coronavirus OC43 (HCoV-OC43). Molecular clock analysis of the S gene sequences estimated BCoV and CRCoV diverged from a common ancestor in 1951, while the time of divergence from a common ancestor of BCoV and HCoV-OC43 was estimated to be 1899. BCoV strains showed the lowest similarity to equine coronavirus, placing the date of divergence at the end of the eighteenth century. Two strongly positive selection sites were detected along the receptor-binding subunit of the S protein gene: spanning amino acid residues 109-131 and 495-527. By contrast, the fusion subunit was observed to be under negative selection. The selection pattern along the S glycoprotein implies adaptive evolution of BCoVs, suggesting a successful mechanism for BCoV to continuously circulate among cattle and other ruminants without disappearance.

Interspecies transmission and emergence of novel viruses: lessons from bats and birds

As exemplified by coronaviruses and influenza viruses, bats and birds are natural reservoirs for providing viral genes during evolution of new virus species and viruses for interspecies transmission. These warm-blooded vertebrates display high species biodiversity, roosting and migratory behavior, and a unique adaptive immune system, which are favorable characteristics for asymptomatic shedding, dissemination, and mixing of different viruses for the generation of novel mutant, recombinant, or reassortant RNA viruses. The increased intrusion of humans into wildlife habitats and overcrowding of different wildlife species in wet markets and farms have also facilitated the interspecies transmission between different animal species.

Genetic characterization of Betacoronavirus lineage C viruses in bats reveals marked sequence divergence in the spike protein of pipistrellus bat coronavirus HKU5 in Japanese pipistrelle: implications for the origin of the novel Middle East respiratory syndrome coronavirus

While the novel Middle East respiratory syndrome coronavirus (MERS-CoV) is closely related to Tylonycteris bat CoV HKU4 (Ty-BatCoV HKU4) and Pipistrellus bat CoV HKU5 (Pi-BatCoV HKU5) in bats from Hong Kong, and other potential lineage C betacoronaviruses in bats from Africa, Europe, and America, its animal origin remains obscure. To better understand the role of bats in its origin, we examined the molecular epidemiology and evolution of lineage C betacoronaviruses among bats. Ty-BatCoV HKU4 and Pi-BatCoV HKU5 were detected in 29% and 25% of alimentary samples from lesser bamboo bat (Tylonycteris pachypus) and Japanese pipistrelle (Pipistrellus abramus), respectively. Sequencing of their RNA polymerase (RdRp), spike (S), and nucleocapsid (N) genes revealed that MERS-CoV is more closely related to Pi-BatCoV HKU5 in RdRp (92.1% to 92.3% amino acid [aa] identity) but is more closely related to Ty-BatCoV HKU4 in S (66.8% to 67.4% aa identity) and N (71.9% to 72.3% aa identity). Although both viruses were under purifying selection, the S of Pi-BatCoV HKU5 displayed marked sequence polymorphisms and more positively selected sites than that of Ty-BatCoV HKU4, suggesting that Pi-BatCoV HKU5 may generate variants to occupy new ecological niches along with its host in diverse habitats. Molecular clock analysis showed that they diverged from a common ancestor with MERS-CoV at least several centuries ago. Although MERS-CoV may have diverged from potential lineage C betacoronaviruses in European bats more recently, these bat viruses were unlikely to be the direct ancestor of MERS-CoV. Intensive surveillance for lineage C betaCoVs in Pipistrellus and related bats with diverse habitats and other animals in the Middle East may fill the evolutionary gap.

Coronaviruses in bats from Mexico

Bats are reservoirs for a wide range of human pathogens including Nipah, Hendra, rabies, Ebola, Marburg and severe acute respiratory syndrome coronavirus (CoV). The recent implication of a novel beta (β)-CoV as the cause of fatal respiratory disease in the Middle East emphasizes the importance of surveillance for CoVs that have potential to move from bats into the human population. In a screen of 606 bats from 42 different species in Campeche, Chiapas and Mexico City we identified 13 distinct CoVs. Nine were alpha (α)-CoVs; four were β-CoVs. Twelve were novel. Analyses of these viruses in the context of their hosts and ecological habitat indicated that host species is a strong selective driver in CoV evolution, even in allopatric populations separated by significant geographical distance; and that a single species/genus of bat can contain multiple CoVs. A β-CoV with 96.5 % amino acid identity to the β-CoV associated with human disease in the Middle East was found in a Nyctinomops laticaudatus bat, suggesting that efforts to identify the viral reservoir should include surveillance of the bat families Molossidae/Vespertilionidae, or the closely related Nycteridae/Emballonuridae. While it is important to investigate unknown viral diversity in bats, it is also important to remember that the majority of viruses they carry will not pose any clinical risk, and bats should not be stigmatized ubiquitously as significant threats to public health.

A mobile genetic element with unknown function found in distantly related viruses

BACKGROUND

The genetic element s2m seems to represent one of very few examples of mobile genetic elements in viruses. The function remains obscure and a scattered taxonomical distribution has been reported by numerous groups.

METHODS

We have searched GenBank in order to identify all viral accessions that have s2m(-like) sequence motifs. Rigorous phylogenetic analyses and constrained tree topology testing were also performed in order to investigate the apparently mobile nature of s2m.

RESULTS

The stem-loop s2m structure can be found in four families of + ssRNA viruses; Astroviridae, Caliciviridae, Picornaviridae and Coronaviridae. In all of these virus families, with the possible exception of Caliciviridae, multiple gains and/or losses of s2m would have to be postulated in order to explain the distribution of this character.

CONCLUSIONS

s2m appears to be a mobile genetic element with a unique evolutionary history in all of the four virus families where it can be found. Based on our findings and a review of the current literature on s2m, a hypothesis implying an RNAi-like function for the s2m element is also outlined.

A case for the ancient origin of coronaviruses

Coronaviruses are found in a diverse array of bat and bird species, which are believed to act as natural hosts. Molecular clock dating analyses of coronaviruses suggest that the most recent common ancestor of these viruses existed around 10,000 years ago. This relatively young age is in sharp contrast to the ancient evolutionary history of their putative natural hosts, which began diversifying tens of millions of years ago. Here, we attempted to resolve this discrepancy by applying more realistic evolutionary models that have previously revealed the ancient evolutionary history of other RNA viruses. By explicitly modeling variation in the strength of natural selection over time and thereby improving the modeling of substitution saturation, we found that the time to the most recent ancestor common for all coronaviruses is likely far greater (millions of years) than the previously inferred range.

Cross-reactive antibodies in convalescent SARS patients' sera against the emerging novel human coronavirus EMC (2012) by both immunofluorescent and neutralizing antibody tests

Objectives

A severe acute respiratory syndrome (SARS)-like disease due to a novel betacoronavirus, human coronavirus EMC (HCoV-EMC), has emerged recently. HCoV-EMC is phylogenetically closely related to Tylonycteris-bat-coronavirus-HKU4 and Pipistrellus-bat-coronavirus-HKU5 in Hong Kong. We conducted a seroprevalence study on archived sera from 94 game-food animal handlers at a wild life market, 28 SARS patients, and 152 healthy blood donors in Southern China to assess the zoonotic potential and evidence for intrusion of HCoV-EMC and related viruses into humans.

Methods

Anti-HCoV-EMC and anti-SARS-CoV antibodies were detected using screening indirect immunofluorescence (IF) and confirmatory neutralizing antibody tests.

Results

Two (2.1%) animal handlers had IF antibody titer of ≥1:20 against both HCoV-EMC and SARS-CoV with neutralizing antibody titer of <1:10. No blood donor had antibody against either virus. Surprisingly, 17/28 (60.7%) of SARS patients had significant IF antibody titers with 7/28 (25%) having anti-HCoV-EMC neutralizing antibodies at low titers which significantly correlated with that of HCoV-OC43. Bioinformatics analysis demonstrated a significant B-cell epitope overlapping the heptad repeat-2 region of Spike protein. Virulence of SARS-CoV over other betacoronaviruses may boost cross-reactive neutralizing antibodies against other betacoronaviruses.

Conclusions

Convalescent SARS sera may contain cross-reactive antibodies against other betacoronaviruses and confound seroprevalence study for HCoV-EMC.

Reservoirs and vectors of emerging viruses

Wildlife, especially mammals and birds, are hosts to an enormous number of viruses, most of which we have absolutely no knowledge about even though we know these viruses circulate readily in their specific niches. More often than not, these viruses are silent or asymptomatic in their natural hosts. In some instances, they can infect other species, and in rare cases, this cross-species transmission might lead to human infection. There are also instances where we know the reservoir hosts of zoonotic viruses that can and do infect humans. Studies of these animal hosts, the reservoirs of the viruses, provide us with the knowledge of the types of virus circulating in wildlife species, their incidence, pathogenicity for their host, and in some instances, the potential for transmission to other hosts. This paper describes examples of some of the viruses that have been detected in wildlife, and the reservoir hosts from which they have been detected. It also briefly explores the spread of arthropod-borne viruses and their diseases through the movement and establishment of vectors in new habitats.

Differential cell line susceptibility to the emerging novel human betacoronavirus 2c EMC/2012: implications for disease pathogenesis and clinical manifestation

The emerging novel human betacoronavirus 2c EMC/2012 (HCoV-EMC) was recently isolated from patients with severe pneumonia and renal failure and was associated with an unexplained high crude fatality rate of 56%. We performed a cell line susceptibility study with 28 cell lines. HCoV-EMC was found to infect the human respiratory tract (polarized airway epithelium cell line Calu-3, embryonic fibroblast cell line HFL, and lung adenocarcinoma cell line A549), kidney (embryonic kidney cell line HEK), intestinal tract (colorectal adenocarcinoma cell line Caco-2), liver cells (hepatocellular carcinoma cell line Huh-7), and histiocytes (malignant histiocytoma cell line His-1), as evident by detection of high or increasing viral load in culture supernatants, detection of viral nucleoprotein expression by immunostaining, and/or detection of cytopathic effects. Although an infected human neuronal cell line (NT2) and infected monocyte and T lymphocyte cell lines (THP-1, U937, and H9) had increased viral loads, their relatively lower viral production corroborated with absent nucleoprotein expression and cytopathic effects. This range of human tissue tropism is broader than that for all other HCoVs, including SARS coronavirus, HCoV-OC43, HCoV-HKU1, HCoV-229E, and HCoV-NL63, which may explain the high mortality associated with this disease. A recent cell line susceptibility study showed that HCoV-EMC can infect primate, porcine, and bat cells and therefore may jump interspecies barriers. We found that HCoV-EMC can also infect civet lung fibroblast and rabbit kidney cell lines. These findings have important implications for the diagnosis, pathogenesis, and transmission of HCoV-EMC.

The new age of virus discovery: genomic analysis of a novel human betacoronavirus isolated from a fatal case of pneumonia

A new human betacoronavirus in lineage c, tentatively called HCoV-EMC, was isolated from a patient from the Kingdom of Saudi Arabia who died from acute severe pneumonia and renal failure. The viral RNA has been detected in eight additional cases. Sequencing and bioinformatic analysis of the viral genomic RNA showed that it is a novel virus not previously detected in any other species and that its closest relatives are two Asian bat coronaviruses. HCoV-EMC may represent a sporadic spillover to humans from an unknown animal reservoir. In a recent article, van Boheemen et al. demonstrated how state-of-the-art sequencing technology and bioinformatic analysis can quickly provide critical insight into the viral genome sequence, phylogeny, replication strategy, and potential drug and vaccine targets and generate tools to evaluate the possible epidemic risk associated with this novel human virus.

Human coronavirus EMC does not require the SARS-coronavirus receptor and maintains broad replicative capability in mammalian cell lines

A new human coronavirus (hCoV-EMC) has emerged very recently in the Middle East. The clinical presentation resembled that of the severe acute respiratory syndrome (SARS) as encountered during the epidemic in 2002/2003. In both cases, acute renal failure was observed in humans. HCoV-EMC is a member of the same virus genus as SARS-CoV but constitutes a sister species. Here we investigated whether it might utilize angiotensin-converting enzyme 2 (ACE2), the SARS-CoV receptor. Knowledge of the receptor is highly critical because the restriction of the SARS receptor to deep compartments of the human respiratory tract limited the spread of SARS. In baby hamster kidney (BHK) cells, lentiviral transduction of human ACE2 (hACE2) conferred permissiveness and replication for SARS-CoV but not for hCoV-EMC. Monkey and human kidney cells (LLC-MK2, Vero, and 769-P) and swine kidney cells were permissive for both viruses, but only SARS-CoV infection could be blocked by anti-hACE2 antibody and could be neutralized by preincubation of virus with soluble ACE2. Our data show that ACE2 is neither necessary nor sufficient for hCoV-EMC replication. Moreover, hCoV-EMC, but not SARS-CoV, replicated in cell lines from Rousettus, Rhinolophus, Pipistrellus, Myotis, and Carollia bats, representing four major chiropteran families from both suborders. As human CoV normally cannot replicate in bat cells from different families, this suggests that hCoV-EMC might use a receptor molecule that is conserved in bats, pigs, and humans, implicating a low barrier against cross-host transmission.

A new human coronavirus (hCoV) emerged recently in the Middle East. The disease resembled SARS (severe acute respiratory syndrome), causing a fatal epidemic in 2002/2003. Coronaviruses have a reservoir in bats and because this novel virus is related to SARS-CoV, we investigated whether it might replicate in bat cells and use the same receptor (angiotensin-converting enzyme 2 [ACE2]). This knowledge is highly critical, because the SARS-CoV receptor influenced pathology, and its localization in the deep respiratory tract is thought to have restricted the transmissibility of SARS. Our data show that hCoV-EMC does not need the SARS-CoV receptor to infect human cells. Moreover, the virus is capable of infecting human, pig, and bat cells. This is remarkable, as human CoVs normally cannot replicate in bat cells as a consequence of host adaptation. Our results implicate that the new virus might use a receptor that is conserved between bats, pigs and humans suggesting a low barrier against cross-host transmission.

Genetic relatedness of the novel human group C betacoronavirus to Tylonycteris bat coronavirus HKU4 and Pipistrellus bat coronavirus HKU5

The recent outbreak of severe respiratory infections associated with a novel group C betacoronavirus (HCoV-EMC) from Saudi Arabia has drawn global attention to another highly probable “SARS-like” animal-to-human interspecies jumping event in coronavirus (CoV). The genome of HCoV-EMC is most closely related to Tylonycteris bat coronavirus HKU4 (Ty-BatCoV HKU4) and Pipistrellus bat coronavirus HKU5 (Pi-BatCoV HKU5) we discovered in 2006. Phylogenetically, HCoV-EMC is clustered with Ty-BatCoV HKU4/Pi-BatCoV HKU5 with high bootstrap supports, indicating that HCoV-EMC is a group C betaCoV. The major difference between HCoV-EMC and Ty-BatCoV HKU4/Pi-BatCoV HKU5 is in the region between S and E, where HCoV-EMC possesses five ORFs (NS3a-NS3e) instead of four, with low (31%–62%) amino acid identities to Ty-BatCoV HKU4/Pi-BatCoV HKU5. Comparison of the seven conserved replicase domains for species demarcation shows that HCoV-EMC is a novel CoV species. More intensive surveillance studies in bats and other animals may reveal the natural host of HCoV-EMC.

Recent transmission of a novel alphacoronavirus, bat coronavirus HKU10, from Leschenault's rousettes to pomona leaf-nosed bats: first evidence of interspecies transmission of coronavirus between bats of different suborders

Although coronaviruses are known to infect various animals by adapting to new hosts, interspecies transmission events are still poorly understood. During a surveillance study from 2005 to 2010, a novel alphacoronavirus, BatCoV HKU10, was detected in two very different bat species, Ro-BatCoV HKU10 in Leschenault's rousettes (Rousettus leschenaulti) (fruit bats in the suborder Megachiroptera) in Guangdong and Hi-BatCoV HKU10 in Pomona leaf-nosed bats (Hipposideros pomona) (insectivorous bats in the suborder Microchiroptera) in Hong Kong. Although infected bats appeared to be healthy, Pomona leaf-nosed bats carrying Hi-BatCoV HKU10 had lower body weights than uninfected bats. To investigate possible interspecies transmission between the two bat species, the complete genomes of two Ro-BatCoV HKU10 and six Hi-BatCoV HKU10 strains were sequenced. Genome and phylogenetic analyses showed that Ro-BatCoV HKU10 and Hi-BatCoV HKU10 represented a novel alphacoronavirus species, sharing highly similar genomes except in the genes encoding spike proteins, which had only 60.5% amino acid identities. Evolution of the spike protein was also rapid in Hi-BatCoV HKU10 strains from 2005 to 2006 but stabilized thereafter. Molecular-clock analysis dated the most recent common ancestor of all BatCoV HKU10 strains to 1959 (highest posterior density regions at 95% [HPDs], 1886 to 2002) and that of Hi-BatCoV HKU10 to 1986 (HPDs, 1956 to 2004). The data suggested recent interspecies transmission from Leschenault's rousettes to Pomona leaf-nosed bats in southern China. Notably, the rapid adaptive genetic change in BatCoV HKU10 spike protein by ~40% amino acid divergence after recent interspecies transmission was even greater than the ~20% amino acid divergence between spike proteins of severe acute respiratory syndrome-related Rhinolophus bat coronavirus (SARSr-CoV) in bats and civets. This study provided the first evidence for interspecies transmission of coronavirus between bats of different suborders.

Identification of a novel bat papillomavirus by metagenomics

The discovery of novel viruses in animals expands our knowledge of viral diversity and potentially emerging zoonoses. High-throughput sequencing (HTS) technology gives millions or even billions of sequence reads per run, allowing a comprehensive survey of the genetic content within a sample without prior nucleic acid amplification. In this study, we screened 156 rectal swab samples from apparently healthy bats (n = 96), pigs (n = 9), cattles (n = 9), stray dogs (n = 11), stray cats (n = 11) and monkeys (n = 20) using a HTS metagenomics approach. The complete genome of a novel papillomavirus (PV), Miniopterus schreibersii papillomavirus type 1 (MscPV1), with L1 of 60% nucleotide identity to Canine papillomavirus (CPV6), was identified in a specimen from a Common Bent-wing Bat (M. schreibersii). It is about 7.5kb in length, with a G+C content of 45.8% and a genomic organization similar to that of other PVs. Despite the higher nucleotide identity between the genomes of MscPV1 and CPV6, maximum-likelihood phylogenetic analysis of the L1 gene sequence showed that MscPV1 and Erethizon dorsatum papillomavirus (EdPV1) are most closely related. Estimated divergence time of MscPV1 from the EdPV1/MscPV1 common ancestor was approximately 60.2–91.9 millions of years ago, inferred under strict clocks using the L1 and E1 genes. The estimates were limited by the lack of reliable calibration points from co-divergence because of possible host shifts. As the nucleotide sequence of this virus only showed limited similarity with that of related animal PVs, the conventional approach of PCR using consensus primers would be unlikely to have detected the novel virus in the sample. Unlike the first bat papillomavirus RaPV1, MscPV1 was found in an asymptomatic bat with no apparent mucosal or skin lesions whereas RaPV1 was detected in the basosquamous carcinoma of a fruit bat Rousettus aegyptiacus. We propose MscPV1 as the first member of the novel Dyolambda-papillomavirus genus.

Isolation and characterization of a novel Betacoronavirus subgroup A coronavirus, rabbit coronavirus HKU14, from domestic rabbits

We describe the isolation and characterization of a novel Betacoronavirus subgroup A coronavirus, rabbit coronavirus HKU14 (RbCoV HKU14), from domestic rabbits. The virus was detected in 11 (8.1%) of 136 rabbit fecal samples by reverse transcriptase PCR (RT-PCR), with a viral load of up to 10(8) copies/ml. RbCoV HKU14 was able to replicate in HRT-18G and RK13 cells with cytopathic effects. Northern blotting confirmed the production of subgenomic mRNAs coding for the HE, S, NS5a, E, M, and N proteins. Subgenomic mRNA analysis revealed a transcription regulatory sequence, 5'-UCUAAAC-3'. Phylogenetic analysis showed that RbCoV HKU14 formed a distinct branch among Betacoronavirus subgroup A coronaviruses, being most closely related to but separate from the species Betacoronavirus 1. A comparison of the conserved replicase domains showed that RbCoV HKU14 possessed <90% amino acid identities to most members of Betacoronavirus 1 in ADP-ribose 1″-phosphatase (ADRP) and nidoviral uridylate-specific endoribonuclease (NendoU), indicating that RbCoV HKU14 should represent a separate species. RbCoV HKU14 also possessed genomic features distinct from those of other Betacoronavirus subgroup A coronaviruses, including a unique NS2a region with a variable number of small open reading frames (ORFs). Recombination analysis revealed possible recombination events during the evolution of RbCoV HKU14 and members of Betacoronavirus 1, which may have occurred during cross-species transmission. Molecular clock analysis using RNA-dependent RNA polymerase (RdRp) genes dated the most recent common ancestor of RbCoV HKU14 to around 2002, suggesting that this virus has emerged relatively recently. Antibody against RbCoV was detected in 20 (67%) of 30 rabbit sera tested by an N-protein-based Western blot assay, whereas neutralizing antibody was detected in 1 of these 20 rabbits.

Genomic characterization of seven distinct bat coronaviruses in Kenya

To better understand the genetic diversity and genomic features of 41 coronaviruses (CoVs) identified from Kenya bats in 2006, seven CoVs as representatives of seven different phylogenetic groups identified from partial polymerase gene sequences, were subjected to extensive genomic sequencing. As a result, 15-16kb nucleotide sequences encoding complete RNA dependent RNA polymerase, spike, envelope, membrane, and nucleocapsid proteins plus other open reading frames (ORFs) were generated. Sequences analysis confirmed that the CoVs from Kenya bats are divergent members of Alphacoronavirus and Betacoronavirus genera. Furthermore, the CoVs BtKY22, BtKY41, and BtKY43 in Alphacoronavirus genus and BtKY24 in Betacoronavirus genus are likely representatives of 4 novel CoV species. BtKY27 and BtKY33 are members of the established bat CoV species in Alphacoronavirus genus and BtKY06 is a member of the established bat CoV species in Betacoronavirus genus. The genome organization of these seven CoVs is similar to other known CoVs from the same groups except for differences in the number of putative ORFs following the N gene. The present results confirm a significant diversity of CoVs circulating in Kenya bats. These Kenya bat CoVs are phylogenetically distant from any previously described human and animal CoVs. However, because of the examples of host switching among CoVs after relatively minor sequence changes in S1 domain of spike protein, a further surveillance in animal reservoirs and understanding the interface between host susceptibility is critical for predicting and preventing the potential threat of bat CoVs to public health.