Eight years of experience with molecular identification of human enteroviruses

Construction of an infectious clone for enterovirus A89 and mutagenesis analysis of viral infection and cell binding

Enterovirus A89 (EV-A89) is an unconventional strain belonging to the Enterovirus A species. Limited research has been conducted on EV-A89, leaving its biological and pathogenic properties unclear. Developing reverse genetic tools for EV-A89 would help to unravel its infection mechanisms and aid in the development of vaccines and anti-viral drugs. In this study, an infectious clone for EV-A89 was successfully constructed and recombinant enterovirus A89 (rEV-A89) was generated. The rEV-A89 exhibited similar characteristics such as growth curve, plaque morphology, and dsRNA expression with parental strain. Four amino acid substitutions were identified in the EV-A89 capsid, which were found to enhance viral infection. Mechanistic studies revealed that these substitutions increased the virus's cell-binding ability. Establishing reverse genetic tools for EV-A89 will significantly contribute to understanding viral infection and developing anti-viral strategies.IMPORTANCEEnterovirus A species contain many human pathogens and have been classified into conventional cluster and unconventional cluster. Most of the research focuses on various conventional members, while understanding of the life cycle and infection characteristics of unconventional viruses is still very limited. In our study, we constructed the infectious cDNA clone and single-round infectious particles for the unconventional EV-A89, allowing us to investigate the biological properties of recombinant viruses. Moreover, we identified key amino acids residues that facilitate EV-A89 infection and elucidate their roles in enhancing viral binding to host cells. The establishment of the reverse genetics system will greatly facilitate future study on the life cycle of EV-A89 and contribute to the development of prophylactic vaccines and anti-viral drugs.

Environmental Monitoring for Enteroviruses in Maputo, Mozambique—2018

Due to the possibility of wild poliovirus importation from endemic regions and the high circulation of vaccine-derived poliovirus type 2 in the African region, Mozambique implemented a surveillance program to monitor the circulation of enteroviruses in the environment. From January to November 2018, a period that immediately preceded the cVDPV outbreak in Africa, 63 wastewater samples were collected from different areas in Maputo city. A total of 25 samples (39.7%) were positive based on cell culture isolation. Non-polio enteroviruses were found in 24 samples (24/25; 96%), whereas 1 Sabin-related poliovirus was isolated. Neither wild nor vaccine-derived poliovirus was detected. High circulation of EVB species was detected. Environmental surveillance in the One Health approach, if effectively applied as support to acute flaccid paralysis, can be a powerful aid to the public health system to monitor poliovirus besides non-polio enteroviruses in polio-free areas.

Cytolytic Properties and Genome Analysis of Rigvir® Oncolytic Virotherapy Virus and Other Echovirus 7 Isolates

Rigvir® is a cell-adapted, oncolytic virotherapy enterovirus, which derives from an echovirus 7 (E7) isolate. While it is claimed that Rigvir® causes cytolytic infection in several cancer cell lines, there is little molecular evidence for its oncolytic and oncotropic potential. Previously, we genome-sequenced Rigvir® and five echovirus 7 isolates, and those sequences are further analyzed in this paper. A phylogenetic analysis of the full-length data suggested that Rigvir® was most distant from the other E7 isolates used in this study, placing Rigvir® in its own clade at the root of the phylogeny. Rigvir® contained nine unique mutations in the viral capsid proteins VP1-VP4 across the whole data set, with a structural analysis showing six of the mutations concerning residues with surface exposure on the cytoplasmic side of the viral capsid. One of these mutations, E/Q/N162G, was located in the region that forms the contact interface between decay-accelerating factor (DAF) and E7. Rigvir® and five other isolates were also subjected to cell infectivity assays performed on eight different cell lines. The used cell lines contained both cancer and non-cancer cell lines for observing Rigvir®'s claimed properties of being both oncolytic and oncotropic. Infectivity assays showed that Rigvir® had no discernable difference in the viruses' oncolytic effect when compared to the Wallace prototype or the four other E7 isolates. Rigvir® was also seen infecting non-cancer cell lines, bringing its claimed effect of being oncotropic into question. Thus, we conclude that Rigvir®'s claim of being an effective treatment against multiple different cancers is not warranted under the evidence presented here. Bioinformatic analyses do not reveal a clear mechanism that could elucidate Rigvir®'s function at a molecular level, and cell infectivity tests do not show a discernable difference in either the oncolytic or oncotropic effect between Rigvir® and other clinical E7 isolates used in the study.

Clinical, epidemiological, and molecular aspects of picornaviruses (entero, parecho) in acute gastroenteritis: A study from Pune (Maharashtra), Western India

Among enteric viruses, rotavirus A (RVA), norovirus (NoV), adenovirus, and astrovirus (AstV) are the major etiological agents associated in acute gastroenteritis. The present study highlights, clinical, epidemiological, and molecular aspects with respect to RVA, NoV, enterovirus (EV), and human parechovirus (HPeVs) in sporadic cases (n = 305) of acute gastroenteritis, Pune (Maharashtra), Western India. Detection of RVA was carried out by enzyme-linked immunosorbent assay, NoV, EV, and HPeVs by reverse transcription PCR. Prevalence of 36.06%, 20.32%, 14.09%, 3.93%, respectively was observed for RVA, EV, HPeVs, and NoV along with coinfections. Infections occurred in children less than 2 years old, with peak infections within 12 months age. The disease severity in RV infections was found high (70.90%) with severe disease, followed by EV (62.9%), NoV (58.33%), and HPeV (44.58%). Predominant strains of RV G1P[8], G2P[4] types with unusual G9P[4], NoV Genogroup II of genotype 4 strains and multiple EV types with EV-B species, E14 and E17 and two novel EV-75, EV-107 types were detected. Circulation of heterogeneous HPeV genotypes (HPeV1-5, 7, 8, 13, 14, 16) with predominance of HPeV-1 was noticed. Changing trends in circulation of a rare HPeV-2 genotype, with emerging and reemerging strains was noted. The study highlights association of RVA, NoV, EV, and HPeV and their mono-infections, genotype distribution, and changing trends in acute gastroenteritis, and added more knowledge on rota and nonrota enteric viruses in acute gastroenteritis. More such studies in rota vaccinated era are required across the country, as Indian rotavirus vaccine has been implemented under the National Immunization program.

Microfluidic sample preparation for respiratory virus detection: A review

Techniques used to prepare clinical samples have been perfected for use in diagnostic testing in a variety of clinical situations, e.g., to extract, concentrate, and purify respiratory virus particles. These techniques offer a high level of purity and concentration of target samples but require significant equipment and highly trained personnel to conduct, which is difficult to achieve in resource-limited environments where rapid testing and diagnostics are crucial for proper handling of respiratory viruses. Microfluidics has popularly been utilized toward rapid virus detection in resource-limited environments, where most devices focused on detection rather than sample preparation. Initial microfluidic prototypes have been hindered by their reliance on several off-chip preprocessing steps and external laboratory equipment. Recently, sample preparation methods have also been incorporated into microfluidics to conduct the virus detection in an all-in-one, automated manner. Extraction, concentration, and purification of viruses have been demonstrated in smaller volumes of samples and reagents, with no need for specialized training or complex machinery. Recent devices show the ability to function independently and efficiently to provide rapid, automated sample preparation as well as the detection of viral samples with high efficiency. In this review, methods of microfluidic sample preparation for the isolation and purification of viral samples are discussed, limitations of current systems are summarized, and potential advances are identified.

Aseptic meningitis outbreak associated with echovirus 4 in Northern Europe in 2013-2014

Picornaviruses (family Picornaviridae) are small, nonenveloped, positive-sense, single-stranded RNA viruses. The members of this family are currently classified into 47 genera and 110 species. Of picornaviruses, entero- and parechoviruses are associated with aseptic meningitis. They are transmitted via fecal-oral and respiratory routes, and occasionally, these viruses may cause a brief viremia and gain access to central nervous system (CNS). During the diagnostic screening of entero- and parechovirus types in Finland in year 2013-14, we detected a cluster of echovirus 4 (E4) infections in young adults and adolescents. As E4 is infrequently detected in Finland, we contacted several Northern and Central European laboratories that conduct routine surveillance for enteroviruses and, for those who have had E4 cases, we send a query for E4 sequences and data. Here we report CNS infections caused by E4 in Finland, Sweden, Norway, Denmark, Iceland and Germany in 2013 and 2014, and show that the E4 detected in these countries form a single lineage. In contrast, E4 strains circulating in these countries preceding the year 2013, and those circulating elsewhere in Europe during 2013-2014, formed several independent clusters.

Recombination Events and Conserved Nature of Receptor Binding Motifs in Coxsackievirus A9 Isolates

Coxsackievirus A9 (CVA9) is an enterically transmitted enterovirus and one of the most pathogenic type among human enteroviruses. CVA9 isolates use a distinctive RGD (Arg-Gly-Asp) motif within VP1 capsid protein that defines its ability to bind to integrin receptor(s) for cellular entry. To investigate CVA9 evolution and pathogenicity, genetic relationships and recombination events were analyzed between 54 novel clinical isolates of CVA9, as well as 21 previously published full length CVA9 sequences from GenBank. Samples were investigated by partial sequencing of the novel VP1 and 3Dpol genes, as well as including the corresponding areas from GenBank sequences. Phylogenetic analyses were combined with clinical data in a further attempt to analyze whether sequence evolution reflects CVA9 pathogenicity in the phylogenies. Furthermore, VP1 gene was also analyzed for receptor binding sites including the RGD motif and the putative heparan sulfate (HS) site. Analysis of the 559-nucleotide-long VP1 sequences identified six clades. Although most of the strains within each clade showed geographical clustering, the grouping pattern of the isolates in the analysis of the VP1 gene was strikingly different from grouping of 3Dpol, which suggests that recombination events may have occurred in the region encoding the nonstructural proteins. Inclusion of clinical data did not provide any evidence of symptom based phylogenetic clustering of CVA9 isolates. Amino acid sequence analysis of the VP1 polypeptide demonstrated that the RGD motif was fully conserved among the isolates while the putative HS binding site was only found in one isolate. These data suggest that integrin binding is essential for virus tropism, but do not explain the symptom repertoire.

Complete genome characterization of three enterovirus C96 isolates in China

Enterovirus C96 (EV-C96) is a newer member of the species Enterovirus C. In this study, we determined the complete genome sequences of three EV-C96 isolates, one recovered from domestic sewage in 2013 and the other two isolated during surveillance of acute flaccid paralysis cases in 1991 and 2009, respectively. The complete genome sequences of these isolates were 75.6-84.2% identical to each other, 75.1-81.8% identical to the prototype strain, and 75.0-91.5% identical to other previously reported strains. Phylogenetic analysis of VP1 sequences revealed a high degree of genetic divergence among currently available EV-C96 sequences in the GenBank database, with an overall mean p-distance of 0.176. It is interesting to note that the 1991 strain 127/SD/CHN/1991 is the earliest EV-C96 isolate so far. Although EV-C96 is not frequently isolated during enterovirus surveillance, its great genetic diversity and the above findings suggest that this serotype has been circulating in China for many years.

Assessment of enteroviruses from sewage water and clinical samples during eradication phase of polio in North India

Background

The Enterovirus (EV) surveillance system is inadequate in densely populated cities in India. EV can be shed in feces for several weeks; these viruses are not easily inactivated and may persist in sewage for long periods. Surveillance and epidemiological study of EV-related disease is necessary.

Methods

In this study, we compare the EV found in sewage with clinically isolated samples. Tissue culture was used for isolation of the virus and serotype confirmed by enterovirus neutralization tests.

Results

We found positive cases for enterovirus from clinical and sewage samples and identified additional isolates as echovirus 9, 11, 25 & 30 by sequencing.

Conclusion

There is a close relation among the serotypes of enterovirus shed in stools and isolated from the environment but few serotypes which were detected in sewage samples were not found clinically and the few which were detected clinically not found in sewage because some viruses are difficult to detect by the cell culture method.This study will be helpful for the researchers who are working on polio and nonpolio enterovirus especially in the countries which are struggling for polio eradication.

The emerging sub-genotype C2 of CoxsackievirusA10 Associated with Hand, Foot and Mouth Disease extensively circulating in mainland of China

Coxsackievirus A10 (CV-A10) associated with Hand, foot, and mouth disease (HFMD) cases emerged increasingly in recent years. In this study, the samples from nation-wide HFMD surveillance, including 27 out of 31 provinces in China were investigated, and the continuous and extensive virological surveillance, covered 13 years, were conducted to provide a comprehensive molecular characterization analysis of CV-A10. 855 CV-A10 viruses (33 severe cases included), were isolated from HFMD children patients during 2009 to 2016 in China. 164 representative sequences from these viruses, together with 117 CV-A10 sequences downloaded from GenBank based on entire VP1 were recruited in this study. Two new genotypes (F and G) and two sub-genotypes (C1 and C2) were identified. Among 264 Chinese sequences, 9 of them were genotype B, 8 of them were C1, and the other (247) were C2, the predominant sub-genotype in China since 2012. Chinese C2 viruses showed obvious temporal characteristics and can be divided into 3 clusters (cluster 1~3). Cluster 3 viruses was circulating extensively during 2014 and 2016 with more severe cases. It is very necessary and important to continuously conduct the extensive virological surveillance for CV-A10, and further evolutionary studies will provide more evidence on its evolution and virulence.

Genome Sequences of RIGVIR Oncolytic Virotherapy Virus and Five Other Echovirus 7 Isolates

We report here the nearly complete Illumina-sequenced consensus genome sequences of six isolates of echovirus 7 (E7), including oncolytic virotherapy virus RIGVIR and the Wallace prototype. Amino acid identities within the coding region were highly conserved across all isolates, ranging from 95.31% to 99.73%.

African Non-Human Primates Host Diverse Enteroviruses

Enteroviruses (EVs) belong to the family Picornaviridae and are responsible for mild to severe diseases in mammals including humans and non-human primates (NHP). Simian EVs were first discovered in the 1950s in the Old World Monkeys and recently in wild chimpanzee, gorilla and mandrill in Cameroon. In the present study, we screened by PCR EVs in 600 fecal samples of wild apes and monkeys that were collected at four sites in Gabon. A total of 32 samples were positive for EVs (25 from mandrills, 7 from chimpanzees, none from gorillas). The phylogenetic analysis of VP1 and VP2 genes showed that EVs identified in chimpanzees were members of two human EV species, EV-A and EV-B, and those identified in mandrills were members of the human species EV-B and the simian species EV-J. The identification of two novel enterovirus types, EV-B112 in a chimpanzee and EV-B113 in a mandrill, suggests these NHPs could be potential sources of new EV types. The identification of EV-B107 and EV90 that were previously found in humans indicates cross-species transfers. Also the identification of chimpanzee-derived EV110 in a mandrill demonstrated a wide host range of this EV. Further research of EVs in NHPs would help understanding emergence of new types or variants, and evaluating the real risk of cross-species transmission for humans as well for NHPs populations.

Integrins are not essential for entry of coxsackievirus A9 into SW480 human colon adenocarcinoma cells

Background

Coxsackievirus A9 (CV-A9) is a pathogenic enterovirus type within the family Picornaviridae. CV-A9 infects A549 human epithelial lung carcinoma cells by attaching to the αVβ6 integrin receptor through a highly conserved Arg-Gly-Asp (RGD) motif, which is located at the exposed carboxy-terminus of the capsid protein VP1 detected in all studied clinical isolates. However, genetically-modified CV-A9 that lacks the RGD motif (CV-A9-RGDdel) has been shown to be infectious in some cell lines but not in A549, suggesting that RGD-mediated integrin binding is not always essential for efficient entry of CV-A9.

Methods

Two cell lines, A549 and SW480, were used in the study. SW480 was the study object for the integrin-independent entry and A549 was used as the control for integrin-dependent entry. Receptor levels were quantitated by cell sorting and quantitative PCR. Antibody blocking assay and siRNA silencing of receptor-encoding genes were used to block virus infection. Peptide phage display library was used to identify peptide binders to CV-A9. Immunofluorescence and confocal microscopy were used to visualize the virus infection in the cells.

Results

We investigated the receptor use and early stages of CV-A9 internalization to SW480 human epithelial colon adenocarcinoma cells. Contrary to A549 infection, we showed that both CV-A9 and CV-A9-RGDdel internalized into SW480 cells and that function-blocking anti-αV integrin antibodies had no effect on the binding and entry of CV-A9. Whereas siRNA silencing of β6 integrin subunit had no influence on virus infection in SW480, silencing of β2-microglobulin (β2M) inhibited the virus infection in both cell lines. By using a peptide phage display screening, the virus-binding peptide identical to the N-terminal sequence of HSPA5 protein was identified and shown to block the virus infection in both A549 and SW480 cell lines. HSPA5 was also found to co-localize with CV-A9 at the SW480 cell periphery during the early stages of infection by confocal microscopy.

Conclusions

The data suggest that while αVβ6 integrin is essential for CV-A9 in A549 cell line, it is not required in SW480 cell line in which β2M and HSPA5 alone are sufficient for CV-A9 infection. This suggests that the choice of CV-A9 receptor(s) is dependent on the tissue/cellular environment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0619-y) contains supplementary material, which is available to authorized users.

Direct Detection and Identification of Enteroviruses from Faeces of Healthy Nigerian Children Using a Cell-Culture Independent RT-Seminested PCR Assay

Recently, a cell-culture independent protocol for detection of enteroviruses from clinical specimen was recommended by the WHO for surveillance alongside the previously established protocols. Here, we investigated whether this new protocol will show the same enterovirus diversity landscape as the established cell-culture dependent protocols. Faecal samples were collected from sixty apparently healthy children in Ibadan, Nigeria. Samples were resuspended in phosphate buffered saline, RNA was extracted, and the VP1 gene was amplified using WHO recommended RT-snPCR protocol. Amplicons were sequenced and sequences subjected to phylogenetic analysis. Fifteen (25%) of the 60 samples yielded the expected band size. Of the 15 amplicons sequenced, 12 were exploitable. The remaining 3 had electropherograms with multiple peaks and were unexploitable. Eleven of the 12 exploitable sequences were identified as Coxsackievirus A1 (CVA1), CVA3, CVA4, CVA8, CVA20, echovirus 32 (E32), enterovirus 71 (EV71), EVB80, and EVC99. Subsequently, the last exploitable sequence was identified as enterobacteriophage baseplate gene by nucleotide BLAST. The results of this study document the first description of molecular sequence data on CVA1, CVA8, and E32 strains present in Nigeria. The result further showed that species A enteroviruses were more commonly detected in the region when cell-culture bias is bypassed.

Defining the Enterovirus Diversity Landscape of a Fecal Sample: A Methodological Challenge?

Enteroviruses are a group of over 250 naked icosahedral virus serotypes that have been associated with clinical conditions that range from intrauterine enterovirus transmission withfataloutcome through encephalitis and meningitis, to paralysis. Classically, enterovirus detection was done by assaying for the development of the classic enterovirus-specific cytopathic effect in cell culture. Subsequently, the isolates were historically identified by a neutralization assay. More recently, identification has been done by reverse transcriptase-polymerase chain reaction (RT-PCR). However, in recent times, there is a move towards direct detection and identification of enteroviruses from clinical samples using the cell culture-independent RT semi-nested PCR (RT-snPCR) assay. This RT-snPCR procedure amplifies the VP1 gene, which is then sequenced and used for identification. However, while cell culture-based strategies tend to show a preponderance of certain enterovirus species depending on the cell lines included in the isolation protocol, the RT-snPCR strategies tilt in a different direction. Consequently, it is becoming apparent that the diversity observed in certain enterovirus species, e.g., enterovirus species B(EV-B), might not be because they are the most evolutionarily successful. Rather, it might stem from cell line-specific bias accumulated over several years of use of the cell culture-dependent isolation protocols. Furthermore, it might also be a reflection of the impact of the relative genome concentration on the result of pan-enterovirus VP1 RT-snPCR screens used during the identification of cell culture isolates. This review highlights the impact of these two processes on the current diversity landscape of enteroviruses and the need to re-assess enterovirus detection and identification algorithms in a bid to better balance our understanding of the enterovirus diversity landscape.

Isolation and Characterization of Enteroviruses from Clinical Samples

Enterovirus infections are common in humans worldwide. Enteroviruses are excreted in feces during infection and can be detected from stool specimens by isolation in continuous laboratory cell lines. Characterization of enteroviruses is based on their antigenic and/or genetic properties.

A Novel Recombinant Enterovirus Type EV-A89 with Low Epidemic Strength in Xinjiang, China

Enterovirus A89 (EV-A89) is a novel member of the EV-A species. To date, only one full-length genome sequence (the prototype strain) has been published. Here, we report the molecular identification and genomic characterization of a Chinese EV-A89 strain, KSYPH-TRMH22F/XJ/CHN/2011, isolated in 2011 from a contact of an acute flaccid paralysis (AFP) patient during AFP case surveillance in Xinjiang China. This was the first report of EV-A89 in China. The VP1 coding sequence of this strain demonstrated 93.2% nucleotide and 99.3% amino acid identity with the EV-A89 prototype strain. In the P2 and P3 regions, the Chinese EV-A89 strain demonstrated markedly higher identity than the prototype strains of EV-A76, EV-A90, and EV-A91, indicating that one or more recombination events between EV-A89 and these EV-A types might have occurred. Long-term evolution of these EV types originated from the same ancestor provides the spatial and temporal circumstances for recombination to occur. An antibody sero-prevalence survey against EV-A89 in two Xinjiang prefectures demonstrated low positive rates and low titres of EV-A89 neutralization antibody, suggesting limited range of transmission and exposure to the population. This study provides a solid foundation for further studies on the biological and pathogenic properties of EV-A89.

Sequence specificity for uridylylation of the viral peptide linked to the genome (VPg) of enteroviruses

Enteroviruses (EV) uridylylate a peptide, VPg, as the first step in their replication. VPgpUpU, found free in infected cells, serves as the primer for RNA elongation. The abilities of four polymerases (3D(pol)), from EV-species A-C, to uridylylate VPgs that varied by up to 60% of their residues were compared. Each 3D(pol) was able to uridylylate all five VPgs using polyA RNA as template, while showing specificity for its own genome encoded peptide. All 3D(pol) uridylylated a consensus VPg representing the physical chemical properties of 31 different VPgs. Thus the residues required for uridylylation and the enzymatic mechanism must be similar in diverse EV. As VPg-binding sites differ in co-crystal structures, the reaction is probably done by a second 3D(pol) molecule. The conservation of polymerase residues whose mutation reduces uridylylation but not RNA elongation is compared.

Enterovirus C strains circulating in Nigeria and their contribution to the emergence of recombinant circulating vaccine-derived polioviruses

Between 2005 and 2011, 23 lineages of circulating vaccine-derived polioviruses (cVDPVs) were detected in Nigeria with nonstructural region (NSR) of non-polio enterovirus C (NPEV-C) origin. However, no information exists on NPEV-C strains recombining with oral poliovirus type 2 vaccine strains (OPV2) to make type 2 cVDPVs (cVDPV2s) in Nigeria. This study was therefore designed to investigate the probable contribution of NPEV-Cs recently isolated in the region to the emergence of cVDPV2s. Eleven enterovirus C (EV-C) strains (8 NPEV-Cs and 3 PV2s) previously isolated by the authors were analysed in this study. All 11 isolates were assayed for cell-line-dependent growth restriction in four cell lines (LLC-MK2, MCF-7, RD and L20B). Subsequently, the isolates were subjected to RT-PCR specific for VP1 and 3Dpol/3'-UTR of EV-C. All PCR products were sequenced, and phylogenetic analysis was performed. All eight NPEV-Cs replicated exclusively in the MCF-7 cell line, while the three PV2s replicated in all four cell lines. The eight NPEV-Cs were identified as CVA13 (7 isolates) and CVA20 (1 isolate) by VP1 analysis, while all 11 isolates were confirmed to be EV-Cs by 3Dpol/3'-UTR analysis. In addition, phylogeny violations suggested that some cVDPVs might have recombined with common ancestors of the NPEV-Cs described in this study. This was confirmed by the scatter plot of divergence in VP1 against that of 3Dpol/3'-UTR sequences for pairs of isolates. The results of this study showed that the NSR of unknown origin found in cVDPVs from the region might have come from NPEV-Cs (e.g., CVA13 and CVA20) circulating in Nigeria.

Molecular epidemiology of enterovirus B77 isolated from non polio acute flaccid paralytic patients in Pakistan during 2013

Human enteroviruses are associated with various clinical syndromes and severe neurological disorders. The aim of this study was to determine the molecular epidemiology of non polio enteroviruses and their correlation with acute flaccid paralysis (AFP) patients living in Khyber Pakhtunkhwa (KP) and Federally Administered Tribal Areas (FATA) of Pakistan. The stool samples collected from these patients were used for isolation of non polio enteroviruses (NPEVs). Out of 38 samples, 29 (76.3%) were successfully typed by microneutralization assay into eleven serotypes including echovirus (E)-3 (5.3%), E-7 (2.6%), E-11 (13.2%), E-12 (7.9%), E-13 (10.5%), E-20 (7.9%), E-27 (5.3%), E-29 (10.5%), E-30 (7.9%), E-33 (2.6%), coxsackievirus (CV) B5 (2.6%) and nine isolates (23.7%) remained untyped which were confirmed as NPEVs by real time RT-PCR. Complete VP1 genetic sequencing data characterized untypeable isolates into enterovirus B77 (EV-B77). Moreover, molecular phylogenetic analysis classified these viruses into two new genotypes having high genetic diversity (at least 17.7%) with prototype. This study provides valuable information on extensive genetic diversity of EV-B77 genotypes. Although, its association with neurological disorder has not yet been known but isolation of nine EV-B77 viruses from AFP cases highlights the fact that they may have a contributing role in the etiology of AFP. In addition, it is needed to establish enterovirus surveillance system and laboratory diagnostic facilities for early detection of NPEVs that may cause poliomyelitis like paralysis especially in the situation when we are at the verge of polio eradication.

Molecular characterization of enteroviruses including a new type EV-C99 isolated from Xinjiang students in Shandong, China in 2011

The last case of infection with wild-type poliovirus indigenous to China was reported in 1994. In 2011, a poliomyelitis outbreak caused by imported wide-type poliovirus occurred in Xinjiang Uighur Autonomous Region. Here, we report the results of enterovirus (EV) isolation from Xinjiang students that returned to school in Shandong after summer vacation during this outbreak. Stool specimens from 376 students were collected and 10 EV strains were isolated including 4 polioviruses (All Sabin strains), 1 coxsackievirus (CV) A13, 3 CVA17 and 2 EV-C99. VP1 sequence analysis revealed these CVA13, CVA17 and EV-C99 strains had 71.3–81.8%, 76.5–84.6% and 74.2–82.9% nucleotide similarity with strains from other countries within a serotype, respectively. EV-C99 strains had 82.7–92.8% VP1 similarity with two previously reported Xinjiang strains. Complete genome analysis on EV-C99 strains revealed intra-serotypic genetic recombination events. These findings reflect great genetic divergence between Chinese strains and strains from other countries of the three types, and provide valuable information on monitoring EV transmission over long distance.

Enterovirus infections in England and Wales, 2000-2011: the impact of increased molecular diagnostics

There have recently been significant changes in diagnostic practices for detecting enterovirus (EV) infections across England and Wales. Reports of laboratory-confirmed EV infections submitted by National Health Service (NHS) hospital laboratories to Public Health England (PHE) over a 12-year period (2000-2011) were analysed. Additionally, the PHE Virus Reference Department (VRD) electronic database containing molecular typing data from 2004 onwards was interrogated. Of the 13,901 reports, there was a decline from a peak of 2254 in 2001 to 589 in 2006, and then an increase year-on-year to 1634 in 2011. This increase coincided with increasing PCR-based laboratory diagnosis, which accounted for 36% of reported cases in 2000 and 92% in 2011. The estimated annual incidence in 2011 was 3.9/100,000 overall and 238/100,000 in those aged <3 months, who accounted for almost one-quarter of reported cases (n = 2993, 23%). During 2004-2011, 2770 strains were submitted for molecular typing to the VRD, who found no evidence for a predominance of any particular strain. Thus, the recent increase in reported cases closely reflects the increase in PCR testing by NHS hospitals, but is associated with a lower proportion of samples being submitted for molecular typing. The high EV rate in young infants merits further investigation to inform evidence-based management guidance.

Molecular surveillance of non-polio enterovirus infections in patients with acute gastroenteritis in Western India: 2004-2009

Acute gastroenteritis is a major cause of childhood morbidity and mortality worldwide. Rotavirus (RV) and Norovirus (NoV) are the leading cause of the disease. Despite the use of improved diagnostic methods a significant proportion of gastroenteritis cases remained undiagnosed. Though nonpolio enteroviruses (NPEVs) have been reported frequently in children with acute gastroenteritis, their etiologic role has not been established. To investigate the epidemiology of NPEVs in gastroenteritis cases which remained negative for leading causative agents, 955 RV and NoV negative stool specimens from children hospitalized for acute gastroenteritis were included in the study. A case control study was conducted which includes stool specimens from 450 children with gastroenteritis and 162 asymptomatic control subjects to determine the association of NPEVs with the disease. NPEV detection and typing was carried out by RT-PCR and sequencing. Presence of RV, NoV, Adenovirus, and Astrovirus was confirmed by ELISA or PCR/RT-PCR. Overall 14% NPEV prevalence was noted. The percentage of children with NPEV infection differed significantly between gastroenteritis and non-gastroenteritis patients (13.7% vs. 4.9%). NPEV was more prevalent among patients with gastroenteritis of undetectable etiology as compared to those detected positive for other viruses (17.9% vs. 7%) (P < 0.01). Genotyping of NPEV identified predominance of EV-B species (56.5%) followed by EV-C (16.7%), EV-A (13.8%) species and mixed NPEV infections (13%). These data support the association of NPEVs with acute gastroenteritis and highlights the clinical and epidemiological features of NPEV infections in patients with acute gastroenteritis from western India.

Isolation and identification of enteroviruses from sewage and sewage-contaminated water in Lagos, Nigeria

Studies have confirmed silent circulation of enteroviruses in the environment even in the absence of associated clinical conditions in the community. In this light, 26 samples of sewage and sewage-contaminated water serving selected high-risk communities in Lagos Nigeria were examined between June and September 2010. To concentrate virus particles in the sample, 480 μL of each sample was centrifuged at 3,000 rpm for 1 h at 4 °C. Subsequently, pellets were pooled, chloroform treated and further centrifuged at 1,500 rpm for 20 min at 4 °C. The water phase (concentrate) was then collected and stored at -20 °C. The concentrates were subsequently inoculated into RD and L20B cell lines. Recovered isolates were identified by real-time RT-PCR (rRT-PCR), serotyping, VP1 amplification, sequencing and phylogenetic analysis. Overall, 9 (34.6%) of the samples showed characteristic enterovirus cytopathic effect in RD cell line and were subsequently confirmed by pan-enterovirus rRT-PCR. The isolates were further identified by serotyping to include three E7, one E11 and one E13 isolates whilst four isolates were untypable. Further characterisation by VP1 sequencing confirmed the results of serotyping and rRT-PCR for all but isolate E13. Also, the four previously untypable isolates were identified to include two E19, one E20 and one E7 by VP1 sequencing. Results of the study confirmed circulation of Sub-Saharan Africa-specific enterovirus clades in the region, provide information on their molecular epidemiology and emphasise the need to combine methods of identification to enhance enterovirus surveillance.

Recombination in the evolution of enterovirus C species sub-group that contains types CVA-21, CVA-24, EV-C95, EV-C96 and EV-C99

Genetic recombination is considered to be a very frequent phenomenon among enteroviruses (Family Picornaviridae, Genus Enterovirus). However, the recombination patterns may differ between enterovirus species and between types within species. Enterovirus C (EV-C) species contains 21 types. In the capsid coding P1 region, the types of EV-C species cluster further into three sub-groups (designated here as A–C). In this study, the recombination pattern of EV-C species sub-group B that contains types CVA-21, CVA-24, EV-C95, EV-C96 and EV-C99 was determined using partial 5′UTR and VP1 sequences of enterovirus strains isolated during poliovirus surveillance and previously published complete genome sequences. Several inter-typic recombination events were detected. Furthermore, the analyses suggested that inter-typic recombination events have occurred mainly within the distinct sub-groups of EV-C species. Only sporadic recombination events between EV-C species sub-group B and other EV-C sub-groups were detected. In addition, strict recombination barriers were inferred for CVA-21 genotype C and CVA-24 variant strains. These results suggest that the frequency of inter-typic recombinations, even within species, may depend on the phylogenetic position of the given viruses.

The evolution of Vp1 gene in enterovirus C species sub-group that contains types CVA-21, CVA-24, EV-C95, EV-C96 and EV-C99

Genus Enterovirus (Family Picornaviridae,) consists of twelve species divided into genetically diverse types by their capsid protein VP1 coding sequences. Each enterovirus type can further be divided into intra-typic sub-clusters (genotypes). The aim of this study was to elucidate what leads to the emergence of novel enterovirus clades (types and genotypes). An evolutionary analysis was conducted for a sub-group of Enterovirus C species that contains types Coxsackievirus A21 (CVA-21), CVA-24, Enterovirus C95 (EV-C95), EV-C96 and EV-C99. VP1 gene datasets were collected and analysed to infer the phylogeny, rate of evolution, nucleotide and amino acid substitution patterns and signs of selection. In VP1 coding gene, high intra-typic sequence diversities and robust grouping into distinct genotypes within each type were detected. Within each type the majority of nucleotide substitutions were synonymous and the non-synonymous substitutions tended to cluster in distinct highly polymorphic sites. Signs of positive selection were detected in some of these highly polymorphic sites, while strong negative selection was indicated in most of the codons. Despite robust clustering to intra-typic genotypes, only few genotype-specific ‘signature’ amino acids were detected. In contrast, when different enterovirus types were compared, there was a clear tendency towards fixation of type-specific ‘signature’ amino acids. The results suggest that permanent fixation of type-specific amino acids is a hallmark associated with evolution of different enterovirus types, whereas neutral evolution and/or (frequency-dependent) positive selection in few highly polymorphic amino acid sites are the dominant forms of evolution when strains within an enterovirus type are compared.

Whole genomic sequence and replication kinetics of a new enterovirus C96 isolated from Guangdong, China with a different cell tropism

Enterovirus 96 (EV-C96) is a newly described serotype within the enterovirus C (EV-C) species, and its biological and pathological characters are largely unknown. In this study, we sequenced the whole genome of a novel EV-C96 strain that was isolated in 2011 from a patient with acute flaccid paralysis (AFP) in Guangdong province, China and characterized the properties of its infection. Sequence analysis revealed the close relationship between the EV-C96 strains isolated from the Guangdong and Shandong provinces of China, and suggested that recombination events occurred both between these EV-C96 strains and with other EV-C viruses. Moreover, the virus replication kinetics showed EV-C96 Guangdong strain replicated at a high rate in RD cells and presented a different cell tropism to other strains isolated from Shandong recently. These findings gave further insight into the evolutionary processes and extensive biodiversity of EV-C96.

Enterovirus 74 infection in children

Enterovirus 74 (EV74) is a rarely detected viral infection of children. In 2010, EV74 was identified in New Zealand in a 2 year old child with acute flaccid paralysis (AFP) through routine polio AFP surveillance. A further three cases of EV74 were identified in children within six months. These cases are the first report of EV74 in New Zealand. In this study we describe the near complete genome sequence of four EV74 isolates from New Zealand, which shows only limited sequence identity in the non-structural proteins when compared to the other two known EV74 sequences. As is typical of enteroviruses multiple recombination events were evident, particularly in the P2 region and P3 regions. This is the first complete EV74 genome sequenced from a patient with acute flaccid paralysis.

Complete genome sequences of three strains of coxsackievirus a7

Genomes of three strains (Parker, USSR, and 275/58) of coxsackievirus A7 (CV-A7) were amplified by the long reverse transcription (RT)-PCR method and sequenced. While the sequences of Parker and USSR were identical, the similarities of 275/58 to the CV-A7 reference sequence, accession no. AY421765, were 82.6% and 96.2% for nucleotides and amino acids, respectively.

Structural and functional analysis of coxsackievirus A9 integrin αvβ6 binding and uncoating

Coxsackievirus A9 (CVA9) is an important pathogen of the Picornaviridae family. It utilizes cellular receptors from the integrin αv family for binding to its host cells prior to entry and genome release. Among the integrins tested, it has the highest affinity for αvβ6, which recognizes the arginine-glycine-aspartic acid (RGD) loop present on the C terminus of viral capsid protein, VP1. As the atomic model of CVA9 lacks the RGD loop, we used surface plasmon resonance, electron cryo-microscopy, and image reconstruction to characterize the capsid-integrin interactions and the conformational changes on genome release. We show that the integrin binds to the capsid with nanomolar affinity and that the binding of integrin to the virion does not induce uncoating, thereby implying that further steps are required for release of the genome. Electron cryo-tomography and single-particle image reconstruction revealed variation in the number and conformation of the integrins bound to the capsid, with the integrin footprint mapping close to the predicted site for the exposed RGD loop on VP1. Comparison of empty and RNA-filled capsid reconstructions showed that the capsid undergoes conformational changes when the genome is released, so that the RNA-capsid interactions in the N termini of VP1 and VP4 are lost, VP4 is removed, and the capsid becomes more porous, as has been reported for poliovirus 1, human rhinovirus 2, enterovirus 71, and coxsackievirus A7. These results are important for understanding the structural basis of integrin binding to CVA9 and the molecular events leading to CVA9 cell entry and uncoating.

Isolation and genomic characterization of three enterovirus 90 strains in Shandong, China

Enterovirus 90 (EV90) is a newly identified serotype of the species Human enterovirus A, and few nucleotide sequences of EV90 are available. In this study, three EV90 strains were isolated from acute flaccid paralysis (AFP) cases in Shandong Province, China, in 2001 and 2003. Sequence analysis revealed 96.7-98.0 % VP1 nucleotide identity among themselves and 77.7-92.3 % to other EV90 strains. Complete genome analysis provided evidence of recombination in the non-capsid coding region of strain 01421. This is the first report of EV90 in China, and the low isolation rate suggests that it has not been a prevalent serotype in China.

Intercity spread of echovirus 6 in Shandong Province, China: application of environmental surveillance in tracing circulating enteroviruses

Environmental surveillance is an effective approach in investigating circulating enteroviruses and had been conducted in the cities of Jinan and Linyi since February 2008 and April 2010, respectively. This study analyzed 46 sewage samples collected in the two cities in 2011 and found that echovirus 6 (E6) was the predominant serotype, with 134 isolates (65 in Jinan and 69 in Linyi) from 23 (50%) samples. This differs from the 2010 data that found 29 E6 isolates in Jinan and only 3 in Linyi. Phylogenetic analysis of the VP1 coding region showed that all environmental E6 samples from 2008 to 2011 (n = 167) segregated into two lineages and revealed an increase in VP1 gene diversity in 2011, suggesting that the increased number of E6 detections reflects a real epidemic in the two cities. Most Linyi isolates (n = 61, or 88%) in 2011 segregated into sublineage 1a, together with 18 Jinan isolates in 2011. Interestingly, the ancestral VP1 sequence of sublineage 1a inferred using the maximum-likelihood method had 100% identity with the sequence of one environmental isolate from Jinan in August 2010, suggesting an intercity spread from Jinan to Linyi. By Bayesian phylodynamic methods, the most recent common ancestor of Linyi isolates in sublineage 1a dated back to 24 December 2010, revealing that this sublineage was likely imported into Linyi from August to December in 2010. This study demonstrates that environmental surveillance is a sensitive method in tracing transmission pathways of circulating enteroviruses among different regions and reveals that E6-associated aseptic meningitis is an emerging concern in China.

Acute respiratory infections due to enterovirus 68 in Yamagata, Japan between 2005 and 2010

To clarify the epidemiology of enterovirus 68 (EV68), which is one of the most rarely identified enteroviruses, virus isolation and molecular screening using RT-PCR was performed on 6307 respiratory specimens collected at pediatric clinics in Yamagata, Japan between 2005 and 2010. In the years 2005-2009, 10, 1, 2, 0, and 2 (40) EV68-positive cases, respectively, were identified by RT-PCR. In 2010, 40 cases were identified altogether: 2 by isolation only, 26 by RT-PCR only, and 12 by both isolation and RT-PCR. Phylogenetic analysis indicated that plural genetically distinct clusters co-circulated. These results suggest that that difficulty in EV68 isolation leads to an underestimation of the prevalence of EV68 infections.

Enterovirus co-infections and onychomadesis after hand, foot, and mouth disease, Spain, 2008

Mixed infection of enteroviruses may explain the rare complication of nail shedding.

Onychomadesis after HFMD

Hand, foot, and mouth disease (HFMD), a common disease caused by enteroviruses (EVs), usually affects children. Clustered and sporadic HFMD cases, followed by onychomadesis (nail shedding), occurred during summer and fall 2008 in Valencia, Spain. Fecal samples from onychomadesis patients, who did or did not have previous HFMD, and from healthy children exposed to onychomadesis patients tested positive for EV. The complete viral protein 1 capsid gene sequence was obtained for typing and phylogenetic analysis. Two EV serotypes, coxsackievirus A10 and coxsackievirus B1 (CVB1), were mainly detected as a monoinfection or co-infection in a childcare center where an onychomadesis outbreak occurred. On the basis of our results, and detection of CVB1 in 2 other contemporary onychomadesis outbreaks in childcare centers in Spain, we propose that mixed infection of an EV serotype that causes HFMD, plus the serotype CVB1, could explain the emergence after HFMD of onychomadesis, a rare and late complication.

Structural analysis of coxsackievirus A7 reveals conformational changes associated with uncoating

Coxsackievirus A7 (CAV7) is a rarely detected and poorly characterized serotype of the Enterovirus species Human enterovirus A (HEV-A) within the Picornaviridae family. The CAV7-USSR strain has caused polio-like epidemics and was originally thought to represent the fourth poliovirus type, but later evidence linked this strain to the CAV7-Parker prototype. Another isolate, CAV7-275/58, was also serologically similar to Parker but was noninfectious in a mouse model. Sequencing of the genomic region encoding the capsid proteins of the USSR and 275/58 strains and subsequent comparison with the corresponding amino acid sequences of the Parker strain revealed that the Parker and USSR strains are nearly identical, while the 275/58 strain is more distant. Using electron cryomicroscopy and three-dimensional image reconstruction, the structures of the CAV7-USSR virion and empty capsid were resolved to 8.2-Å and 6.1-Å resolutions, respectively. This is one of the first detailed structural analyses of the HEV-A species. Using homology modeling, reconstruction segmentation, and flexible fitting, we constructed a pseudoatomic T = 1 (pseudo T = 3) model incorporating the three major capsid proteins (VP1 to VP3), addressed the conformational changes of the capsid and its constituent viral proteins occurring during RNA release, and mapped the capsid proteins' variable regions to the structure. During uncoating, VP4 and RNA are released analogously to poliovirus 1, the interfaces of VP2 and VP3 are rearranged, and VP1 rotates. Variable regions in the capsid proteins were predicted to map mainly to the surface of VP1 and are thus likely to affect the tropism and pathogenicity of CAV7.

Comparison of human parechovirus and enterovirus detection frequencies in cerebrospinal fluid samples collected over a 5-year period in edinburgh: HPeV type 3 identified as the most common picornavirus type

Human enteroviruses (EVs) and more recently parechoviruses (HPeVs) have been identified as the principal viral causes of neonatal sepsis-like disease and meningitis. The relative frequencies of specific EV and HPeV types were determined over a 5-year surveillance period using highly sensitive EV and HPeV PCR assays for screening 4,168 cerebrospinal fluid (CSF) specimens collected from hospitalized individuals between 2005 and 2010 in Edinburgh. Positive CSF samples were typed by sequencing of VP1. From the 201 EV and 31 HPeV positive (uncultured) CSF samples on screening, a high proportion of available samples could be directly typed (176/182, 97%). Highest frequencies of EV infections occurred in young adults (n = 43; 8.6%) although a remarkably high proportion of positive samples (n = 98; 46%) were obtained from young infants (<3 months). HPeV infections were seen exclusively in children under the age of 3 months (31/1,105; 2.8%), and confined to spring on even-numbered years (22% in March 2006, 25% in April 2008, and 22% in March 2010). In contrast, EV infections were distributed widely across the years. Twenty different EV serotypes were detected; E9, E6, and CAV9 being found most frequently, whereas all but one HPeVs were type 3. Over this period, HPeV3 was identified as the most prevalent picornavirus type in CNS-related infections with similarly high incidences of EV infection frequencies in very young children. The highly sensitive virus typing methods applied in this study will assist further EV and HPeV screening of sepsis and meningitis cases as well as in future molecular epidemiological studies and population surveillance.

Spatiotemporal phylogenetic analysis and molecular characterization of coxsackievirus A4

Coxsackievirus A4 outbreaks occurred in Taiwan in 2004 and 2006. The spatiotemporal transmission of this error-prone RNA virus involves a continuous interaction between rapid sequence variation and natural selection. To elucidate the molecular characteristics of CV-A4 and the spatiotemporal dynamic changes in CV-A4 transmission, worldwide sequences of the 3' VP1 region (420 nt) obtained from GenBank were analyzed together with sequences isolated in Taiwan from 2002 to 2009. Sequences were characterized in terms of recombination, variability, and selection. Phylogenetic trees were constructed using neighbor-joining, maximum likelihood and Monte Carlo Markov Chain methods. Spatiotemporal dynamics of CV-A4 transmission were further estimated by a Bayesian statistical inference framework. No recombination was detected in the 420 nt region. The estimated evolution rate of CV-A4 was 8.65 × 10(-3) substitutions/site/year, and a purifying selection (d(N)/d(S)=0.032) was noted over the 3' VP1 region. All trees had similar topology: two genotypes (GI and GII), each including two subgenotypes (A and B), with the prototype and a Kenyan strain in separate branches. The results revealed that the virus first appeared in USA in 1950. Since 1998, it has evolved into the Kenya, GI-A (Asia) and GII-A (Asia and Europe) strains. Since 2004, GI-B and GII-B have evolved continuously and have remained prevalent. The co-existence of several positive selection lineages of GI-B in 2006 indicates that the subgenotype might have survived lineage extinction. This study revealed rapid lineage turnover of CV-A4 and the replacement of previously circulating strains by a new dominant variant. Therefore, continuous surveillance for further CV-A4 transmission is essential.

Rapid simultaneous detection of enterovirus and parechovirus RNAs in clinical samples by one-step real-time reverse transcription-PCR assay

Enteroviruses (EVs) are recognized as the major etiological agent in meningitis in children and young adults. The use of molecular techniques, such as PCR, has substantially improved the sensitivity of enterovirus detection compared to that of virus culture methods. PCR-based methods also can detect a much wider range of EV variants, including those within species A, as well as human parechoviruses (HPeVs) that often grow poorly in vitro and which previously have been underdiagnosed by traditional methods. To exploit these developments, we developed a real-time one-step reverse transcription-PCR (RT-PCR) for the rapid and sensitive detection of EV and HPeV in clinical specimens. Two commercially available RT-PCR kits were used (method I, Platinum one-step kit; method II, Express qPCR one-step kit) with primers and probes targeting the EV and HPeV 5'-untranslated regions (5'UTR). Amplification dynamics (threshold cycle [C(T)]values and efficiencies) of absolutely quantified full-length RNA transcripts representative of EV species A to D and HPeV were similar, demonstrating the effectiveness of both assays across the range of currently described human EV and HPeV variants. Probit analysis of multiple endpoint replicates demonstrated comparable sensitivities of the assays for EV and HPeV (method I, approximately 10 copies per reaction for both targets; method II, 20 copies per reaction). C(T) values were highly reproducible on repeat testing of positive controls within assays and between assay runs. Considering the sample turnaround time of less than 3 h, the multiplexed one-step RT-PCR method provides rapid diagnostic testing for EV and HPeV in cases of suspected central nervous system infections in a clinically relevant time frame.

Antibody dependent enhancement infection of enterovirus 71 in vitro and in vivo

BACKGROUND

Human enterovirus 71 (EV71) has emerged as a significant cause of acute encephalitis and deaths in young children. The clinical manifestations caused by EV71 varied from mild hand, foot and mouth disease to severe neurological complications and deaths, but its pathogenesis remains elusive. Antibody dependent enhancement (ADE) infection has been reported in various viruses and has been shown to contribute to disease severity.

RESULTS

In this study, the presence of sub-neutralizing antibody was demonstrated to enhance EV71 infection in THP-1 cells and increase the mortality of EV71 infection in a suckling mouse model. Further, a secondary infection model was established to characterize the correlation between ADE and disease severity, and primary asymptomatic EV71 infection was shown to increase the mortality of the secondary EV71 infection in suckling mice.

CONCLUSIONS

Together, these in vitro and in vivo experiments strongly supported the hypothesis of ADE infection of EV71. The present findings indicate ADE might contribute to the pathogenesis of severe EV71 infection, and raise practical issues of vaccine development and antibody-based therapy.

The complete genome analysis of two enterovirus 96 strains isolated in China in 2005 and 2009

Enterovirus 96 (EV96) is a new member of species Human Enterovirus C (HEV-C). In this report, genomic characterization of two EV96 strains isolated from acute flaccid paralysis surveillance in Shandong province of China in 2005 and 2009 is described. The two strains, designated 05517 and 09228C1, had 82.7% genomic similarity with each other and 75.1-84.2% with other three strains available from GenBank in complete genome sequences. In VP1 coding region, they had 77.6-86.6% nucleotide similarity with other EV96 strains. Interestingly, deletions of 3 nucleotides in the VP3 coding region of strain 09228C1, and of 3 nucleotides in the 3A region of both Shandong strains were observed. Simplot and bootscanning analysis on HEV-C genome sequences were performed, and evidence of recombination in P3 region for Shandong EV96 strains was found. In conclusion, these strains had distant genetic relationship with each other and with other EV96 strains.

Cellular tropism of human enterovirus D species serotypes EV-94, EV-70, and EV-68 in vitro: implications for pathogenesis

Enterovirus 94 (EV-94) is an enterovirus serotype described recently which, together with EV-68 and EV-70, forms human enterovirus D species. This study investigates the seroprevalences of these three serotypes and their abilities to infect, replicate, and damage cell types considered to be essential for enterovirus-induced diseases. The cell types studied included human leukocyte cell lines, primary endothelial cells, and pancreatic islets. High prevalence of neutralizing antibodies against EV-68 and EV-94 was found in the Finnish population. The virus strains studied had wide leukocyte tropism. EV-94 and EV-68 were able to produce infectious progeny in leukocyte cell lines with monocytic, granulocytic, T-cell, or B-cell characteristics. EV-94 and EV-70 were capable of infecting primary human umbilical vein endothelial cells, whereas EV-68 had only marginal progeny production and did not induce cytopathic effects in these cells. Intriguingly, EV-94 was able to damage pancreatic islet β-cells, to infect, replicate, and cause necrosis in human pancreatic islets, and to induce proinflammatory and chemoattractive cytokine expression in endothelial cells. These results suggest that HEV-D viruses may be more prevalent than has been thought previously, and they provide in vitro evidence that EV-94 may be a potent pathogen and should be considered a potentially diabetogenic enterovirus type.

Enterovirus infection induces cytokine and chemokine expression in insulin-producing cells

Despite evidence supporting an association between enterovirus (EV) infection and type 1 diabetes, the etiological mechanism(s) for EV-induced beta cell destruction is(are) not well understood. In this study, the effects of Coxsackievirus B (CVB) 1-6 on cell lysis and cytokine/chemokine expression in the insulinoma-1 (INS-1) beta cell line were investigated. Cytolysis was assessed using tissue culture infectious dose 50 (TCID(50)). Quantitative RT-PCR was used to measure viral RNA and mRNA of cytokines interferon (IFN)-α, IFN-β, IFN-γ, tumor necrosis factor (TNF)-α, and chemokine (C-X-C motif) ligand 10 (CXCL10), chemokine (C-C motif) ligand 2 (CCL2), and chemokine (C-C motif) ligand 5 (CCL5) in infected INS-1 cells. CVB2, 4, 5, and 6 lysed and replicated in INS-1 cells; TCID(50) was lowest for CVB5 and highest for CVB6. IFN-γ, CXCL10, and CCL5 mRNA levels all increased significantly following infection with CVB2, 4, 5, and 6 (P<0.05). CCL2 mRNA increased with CVB2, 5, and 6 (P<0.05), IFN-α mRNA increased with CVB5 infection (P<0.05), while TNF-α mRNA and IFN-β mRNA (P<0.001) increased with CVB2 infection. Dose-dependent effects of infection on cytokine mRNA levels were observed for all (P<0.01) except IFN-γ. Following inoculation of INS-1 cells with CVB1 and 3, viral RNA was not detected and cytokine/chemokine mRNA levels were unchanged. In conclusion, CVB2, 4, 5, and 6 induce dose-dependent cytokine and chemokine mRNA production from INS-1 cells suggesting that pro-inflammatory cytokine and chemokine secretion by beta cells is a potential mechanism for EV-induced beta cell damage in type 1 diabetes.

Evolution of newly described enteroviruses

Several new enterovirus serotypes and a new human rhinovirus species have been characterized in the Enterovirus genus recently, raising a question about the origin of the new viruses. In this article we attempt to outline the general patterns of enterovirus evolution, ultimately leading to the emergence of new serotypes or species. Different evolutionary and epidemiological patterns can be deduced between different enterovirus species, between entero- and rhino-viruses and between different serotypes within a species. This article presents a hypothesis that the divergent evolution leading to a new serotype is likely to involve adaptation to a new ecological niche either within a single host species or due to interspecies transmission. By contrast, evolution within a serotype appears to occur primarily by genetic drift.