Retrospective Study of the Upsurge of Enterovirus D68 Clade D1 among Adults (2014-2018)

Enterovirus D68 (EV-D68) has emerged as an agent of epidemic respiratory illness and acute flaccid myelitis in the paediatric population but data are lacking in adult patients. We performed a 4.5-year single-centre retrospective study of all patients who tested positive for EV-D68 and analysed full-length EV-D68 genomes of the predominant clades B3 and D1. Between 1 June 2014, and 31 December 2018, 73 of the 11,365 patients investigated for respiratory pathogens tested positive for EV-D68, of whom 20 (27%) were adults (median age 53.7 years [IQR 34.0-65.7]) and 53 (73%) were children (median age 1.9 years [IQR 0.2-4.0]). The proportion of adults increased from 12% in 2014 to 48% in 2018 (p = 0.01). All adults had an underlying comorbidity factor, including chronic lung disease in 12 (60%), diabetes mellitus in six (30%), and chronic heart disease in five (25%). Clade D1 infected a higher proportion of adults than clades B3 and B2 (p = 0.001). Clade D1 was more divergent than clade B3: 5 of 19 amino acid changes in the capsid proteins were located in putative antigenic sites. Adult patients with underlying conditions are more likely to present with severe complications associated with EV-D68, notably the emergent clade D1.

Respiratory and intestinal epithelial cells exhibit differential susceptibility and innate immune responses to contemporary EV-D68 isolates

Enterovirus D68 (EV-D68) has been implicated in outbreaks of severe respiratory illness and is associated with acute flaccid myelitis (AFM). EV-D68 is often detected in patient respiratory samples but has also been detected in stool and wastewater, suggesting the potential for both respiratory and enteric routes of transmission. Here, we used a panel of EV-D68 isolates, including a historical pre-2014 isolate and multiple contemporary isolates from AFM outbreak years, to define the dynamics of viral replication and the host response to infection in primary human airway cells and stem cell-derived enteroids. We show that some recent EV-D68 isolates have decreased sensitivity to acid and temperature compared with earlier isolates and that the respiratory, but not intestinal, epithelium induces a robust type III interferon response that restricts infection. Our findings define the differential responses of the respiratory and intestinal epithelium to contemporary EV-D68 isolates and suggest that a subset of isolates have the potential to target both the human airway and gastrointestinal tracts.

Seroepidemiology of enterovirus D68 in a healthy population in Beijing, China, between 2012 and 2017: A retrospective study

To investigate the seroepidemiological features of enterovirus D68 (EV-D68) in the healthy population from 2012 to 2017 in Beijing, China. A retrospective cross-sectional investigation was conducted using serum specimens collected from healthy individuals in Beijing from 2012 to 2017. These samples were tested for neutralization antibodies (NtAbs) against EV-D68. The sera from six EV-D68 infected patients in the acute or convalescent phase were used to determine the protection level of NtAbs against EV-D68. The geometric means of the titers (GMT) of EV-D68 NtAbs in 2012 and 2017 were 92.82 and 242.91, respectively; the seroprevalences of EV-D68 were 89.43% and 98.43%, respectively. The GMT reached its peak in the 11 to 15 age group in 2012, while in 16 to 20 age group in 2017. We also observed that EV-D68 NtAbs titers of six sera from the acute phase were all less than equal to  1:64 and that of three sera from the convalescent phase were all more than 1:64. Anti-EV-D68 NtAbs in the population remained low from 2012 to 2016 but increased significantly in 2017. Although most of the EV-D68 infections remain undetected in Beijing, the risk of a large outbreak of EV-D68 exists and should be taken seriously.

Outbreak of Enterovirus D68 Among Children in Japan-Worldwide Circulation of Enterovirus D68 Clade B3 in 2018

BACKGROUND

Enterovirus D68 (EV-D68) causes asthma-like respiratory infection in children. Several EV-D68 outbreaks have been reported worldwide since the largest outbreak occurred in the United States in 2014. We experienced an accumulation of pediatric cases with asthma-like respiratory illness in Niigata, Japan, in 2018.

STUDY DESIGN

To determine whether EV-D68 was responsible for the case accumulation, this prospective observational study evaluated children hospitalized in 1 of 8 hospitals with asthma-like respiratory illness in Niigata, Japan, during October and November 2018. Diagnoses were made by EV-D68-specific RT-PCR using nasopharyngeal samples. The clade was identified by sequence analyses, and a phylogenetic tree was created. To evaluate seasonal variation, data from pediatric cases with asthma-like respiratory illness in 2018 were retrospectively analyzed.

RESULTS

In 2018, 114 children were hospitalized with asthma-like respiratory illness in October and November, and 47 nasopharyngeal samples were collected. EV-D68 was detected in 22/47 (47%) patients during the study period. The phylogenetic tree revealed that all strains belonged to the clade B3 branch, which has been detected worldwide every 2 years since 2014.

CONCLUSIONS

EV-D68 was the associated pathogen for asthma-like respiratory illness in children in Japan in 2018. Clade B3, the dominant clade in outbreaks worldwide, was responsible for the outbreak. Detection and detailed virologic analysis of EV-D68 is important as part of worldwide surveillance, as it will aid in understanding the epidemiologic characteristics of EV-D68 infection.

Enterovirus D68 molecular and cellular biology and pathogenesis

In recent years, enterovirus D68 (EV-D68) has advanced from a rarely detected respiratory virus to a widespread pathogen responsible for increasing rates of severe respiratory illness and acute flaccid myelitis (AFM) in children worldwide. In this review, we discuss the accumulating data on the molecular features of EV-D68 and place these into the context of enterovirus biology in general. We highlight similarities and differences with other enteroviruses and genetic divergence from own historical prototype strains of EV-D68. These include changes in capsid antigens, host cell receptor usage, and viral RNA metabolism collectively leading to increased virulence. Furthermore, we discuss the impact of EV-D68 infection on the biology of its host cells, and how these changes are hypothesized to contribute to motor neuron toxicity in AFM. We highlight areas in need of further research, including the identification of its primary receptor and an understanding of the pathogenic cascade leading to motor neuron injury in AFM. Finally, we discuss the epidemiology of the EV-D68 and potential therapeutic approaches.

Low Circulation of Subclade A1 Enterovirus D68 Strains in Senegal during 2014 North America Outbreak

To retrospectively investigate enterovirus D68 circulation in Senegal during the 2014 US outbreak, we retrieved specimens from 708 persons, mostly children, who had acute respiratory symptoms during September-December 2014. Enterovirus D68 was detected in 14 children (2.1%); most cases occurred in October. Phylogenetic analysis revealed that all strains clustered within subclade A1.

Molecular and Clinical Comparison of Enterovirus D68 Outbreaks among Hospitalized Children, Ohio, USA, 2014 and 2018

Enterovirus D68 (EV-D68) causes respiratory tract infections and neurologic manifestations. We compared the clinical manifestations from 2 EV-D68 outbreaks in 2014 and 2018 and a low-activity period in 2016 among hospitalized children in central Ohio, USA, and used PCR and sequencing to enable phylogenetic comparisons. During both outbreak periods, infected children had respiratory manifestations that led to an increase in hospital admissions for asthma. The 2018 EV-D68 outbreak appeared to be milder in terms of respiratory illness, as shown by lower rates of pediatric intensive care unit admission. However, the frequency of severe neurologic manifestations was higher in 2018 than in 2014. During the same period in 2016, we noted neither an increase in EV-D68 nor a significant increase in asthma-related admissions. Phylogenetic analyses showed that EV-D68 isolates from 2018 clustered differently within clade B than did isolates from 2014 and are perhaps associated with a different EV-D68 subclade.

Genetic and phenotypic characterization of recently discovered enterovirus D type 111

Members of the species Enterovirus D (EV-D) remain poorly studied. The two first EV-D types (EV-D68 and EV-D70) have regularly caused outbreaks in humans since their discovery five decades ago but have been neglected until the recent occurrence of severe respiratory diseases due to EV-D68. The three other known EV-D types (EV-D94, EV-D111 and EV-D120) were discovered in the 2000s-2010s in Africa and have never been observed elsewhere. One strain of EV-D111 and all known EV-D120s were detected in stool samples of wild non-human primates, suggesting that these viruses could be zoonotic viruses. To date, EV-D111s are only known through partial genetic sequences of the few strains that have been identified so far. In an attempt to bring new pieces to the puzzle, we genetically characterized four EV-D111 strains (among the seven that have been reported until now). We observed that the EV-D111 strains from human samples and the unique simian EV-D111 strain were not phylogenetically distinct, thus suggesting a recent zoonotic transmission. We also discovered evidences of probable intertypic genetic recombination events between EV-D111s and EV-D94s. As recombination can only happen in co-infected cells, this suggests that EV-D94s and EV-D111s share common replication sites in the infected hosts. These sites could be located in the gut since the phenotypic analysis we performed showed that, contrary to EV-D68s and like EV-D94s, EV-D111s are resistant to acid pHs. We also found that EV-D111s induce strong cytopathic effects on L20B cells, a cell line routinely used to specifically detect polioviruses. An active circulation of EV-D111s among humans could then induce a high number of false-positive detection of polioviruses, which could be particularly problematic in Central Africa, where EV-D111 circulates and which is a key region for poliovirus eradication.

Current Understanding of Human Enterovirus D68

Human enterovirus D68 (EV-D68), a member of the species Enterovirus D of the Picornaviridae family, was first isolated in 1962 in the United States. EV-D68 infection was only infrequently reported until an outbreak occurred in 2014 in the US; since then, it has continued to increase worldwide. EV-D68 infection leads to severe respiratory illness and has recently been reported to be linked to the development of the neurogenic disease known as acute flaccid myelitis (AFM), mostly in children, seriously endangering public health. Hitherto, treatment options for EV-D68 infections were limited to supportive care, and as yet there are no approved, specific antiviral drugs or vaccines. Research on EV-D68 has mainly focused on its epidemiology, and its virologic characteristics and pathogenesis still need to be further explored. Here, we provide an overview of current research on EV-D68, including the genotypes and genetic characteristics of recent epidemics, the mechanism of infection and virus-host interactions, and its relationship to acute flaccid myelitis (AFM), in order to broaden our understanding of the biological features of EV-D68 and provide a basis for the development of effective antiviral agents.

Neutralizing Antibody against Enterovirus D68 in Children and Adults before 2014 Outbreak, Kansas City, Missouri, USA1

We evaluated enterovirus D68 seroprevalence in Kansas City, Missouri, USA, from samples obtained during 2012-2013. Neutralizing antibodies against Fermon and the dominant 2014 Missouri isolate were universally detected. Titers increased with age. Widespread circulation of enterovirus D68 occurred before the 2014 outbreak. Research is needed to determine a surrogate of protection.

A cross-sectional seroepidemiology study of EV-D68 in China

Enterovirus 68 (EV-D68) is associated with respiratory diseases, such as acute upper respiratory tract infections (URTIs), lower respiratory tract infections (LRTIs), pneumonia, neurological diseases, and acute flaccid myelitis (AFM). In recent years, there have been global outbreaks of EV-D68 epidemics. However, there is no effective vaccine against EV-D68, and the understanding of the seroprevalence characteristics of EV-D68 is limited. To evaluate the epidemiological features of this emerging infection in mainland China, serum samples from 20 pairs of pregnant women and their neonates, 405 infants and children (ages 1 month-15 years), and 50 adults were collected to measure EV-D68 neutralizing antibodies (NtAbs). The results showed that the geometric mean titers (GMTs) of pregnant women and their neonates were 168 (95%CI: 93.6-301.7) and 162.3 (95%CI: 89.9-293.1), respectively. The seroprevalence rate of EV-D68 antibodies was negatively correlated with age in 1-month-old to 12-month-old infants (84% for 1-month-old infants vs 10% for 1-year-old infants), whereas it was positively correlated with age for 1-year-old to 15-year-old children (10% for 1-year-old children vs 92% for 15-year-old children). This study evaluated maternal antibodies against EV-D68 in neonates. Our results showed that if mothers had high levels of anti-EV-D68 NtAbs, the NtAbs titers in their neonates were also high. The GMTs and seroprevalence rates of each age group indicated that EV-D68 infection was very common in China. Periodical EV-D68 seroprevalence surveys and vaccination campaigns should be the top priority for preventing EV-D68 infection.

Enterovirus D68-Associated Acute Flaccid Myelitis in Immunocompromised Woman, Italy

In Italy in 2016, acute flaccid myelitis developed in a woman who had received a hematopoietic stem cell transplant. Enterovirus D68 viral genome was detected in respiratory and cerebrospinal fluid samples, and the viral protein 1 sequence clustered with lineage B3. Immunocompromised adults may be at risk for enterovirus D68-associated neurologic complications.

Enterovirus-D68 (EV-D68) in pediatric patients with respiratory infection: The circulation of a new B3 clade in Italy

BACKGROUND

In recent years, several outbreaks due to Enterovirus D-68 (EV-D68) have been reported, and it was confirmed that the virus can cause upper and lower respiratory tract diseases and be associated with the development of neurological problems.

OBJECTIVES

The main aim of this research was to study the genetic characteristics of EV-D68 strains that were circulating in Italy identified during an outbreak of an EV-D68 infection that occurred in Italy during the period March-October 2016.

STUDY DESIGN

A retrospective study of the circulation of different types and subtypes of EV-D68 was performed. Nasopharyngeal swabs were collected from March 2016 through October 2016 in children admitted to the Emergency Room with respiratory diseases.

RESULTS

Among 390 children, 22 (59.1% males; mean age 47 months) were found to be infected by EV-D68 and most of them were immunocompetent (72.7%). Pneumonia was diagnosed in 12 (54.5%) children. Phylogenetic analysis of the VP1 region showed that all the strains identified in this study belonged to clade B3. Within B3 subclade, the Italian EV-D68 strains were most closely related to strains detected in Southern China in 2015 as well as to strains detected in US and the Netherlands in 2016.

CONCLUSIONS

These results showed that EV-D68 infections are a common cause of lower respiratory illness in pediatric age. The circulation of one EV-D68 lineage has been proven in Italy and in the European region during 2016. However, further studies are required to investigate whether some strains or lineages may possess a higher affinity for the lower airway or central nervous system.

Distinct genetic clades of enterovirus D68 detected in 2010, 2013, and 2015 in Osaka City, Japan

The first upsurge of enterovirus D68 (EV-D68), a causative agent of acute respiratory infections (ARIs), in Japan was reported in Osaka City in 2010. In this study, which began in 2010, we surveyed EV-D68 in children with ARIs and analyzed sequences of EV-D68 strains detected. Real-time PCR of 19 respiratory viruses or subtypes of viruses, including enterovirus, was performed on 2,215 specimens from ARI patients (<10 years of age) collected between November 2010 and December 2015 in Osaka City, Japan. EV-D68 was identified in 18 enterovirus-positive specimens (n = 4 in 2013, n = 1 in 2014, and n = 13 in 2015) by analysis of viral protein 1 (VP1) or VP4 sequences, followed by a BLAST search for similar sequences. All EV-D68 strains were detected between June and October (summer to autumn), except for one strain detected in 2014. A phylogenetic analysis of available VP1 sequences revealed that the Osaka strains detected in 2010, 2013, and 2015 belonged to distinct clusters (Clades C, A, and B [Subclade B3], respectively). Comparison of the 5' untranslated regions of these viruses showed that Osaka strains in Clades A, B (Subclade B3), and C commonly had deletions at nucleotide positions 681-703 corresponding to the prototype Fermon strain. Clades B and C had deletions from nucleotide positions 713-724. Since the EV-D68 epidemic in 2010, EV-D68 re-emerged in Osaka City, Japan, in 2013 and 2015. Results of this study indicate that distinct clades of EV-D68 contributed to re-emergences of this virus in 2010, 2013, and 2015 in this limited region.

Upsurge of Enterovirus D68, the Netherlands, 2016

In June and July 2016, we identified 8 adults and 17 children with respiratory enterovirus D68 infections. Thirteen children required intensive care unit admission because of respiratory insufficiency, and 1 had concomitant acute flaccid myelitis. Phylogenetic analysis showed that all of 20 sequences obtained belong to the recently described clade B3.

The Genomic Characterization of Enterovirus D68 from 2011 to 2015 in Beijing, China

A retrospective surveillance study on enterovirus D68 was performed in Beijing, China, following the largest and most widespread EV-D68 infection, which occurred in the USA. From January 2011 to July 2015, EV-D68 was identified in 12 individuals with respiratory infections in Beijing, China. The phylogenetic relationships based on the genomic sequence alignment showed that there were two lineages circulating in Beijing from 2011 to 2015. Eight EV-D68 strains belonged to group 1 and four belonged to group 3. All EV-D68 strains from Beijing in 2014 were separately clustered into subgroup II of group 1. Based on these results, we concluded that the Beijing EV-D68 strains had little association with the EV-D68 strains circulating in the 2014 USA outbreak.

Respiratory infections associated with enterovirus D68 from 2011 to 2015 in Beijing, China

Enterovirus D68 (EV-D68) is an emergent viral pathogen associated with mild to severe respiratory infections. In this study, we describe respiratory infections associated with EV-D68 in Beijing over a 4 year period. Total nucleic acid was extracted from 7,945 clinical specimens collected between January 5, 2011 and July 30, 2015 in Beijing and used for detecting EV-D68 and other enteroviruses by real-time PCR. Overall, 555/7,945 (6.99%) specimens were enterovirus positive: 12/7,945 (0.2%) specimens were EV-D68 positive. Of these patients, 11 were pediatric patients and 1 was a 76-year-old man. The main symptoms for the 12 EV-D68 positive patients were fever (10/12, 83.3%) and cough (6/12, 50%). Ten EV-D68 infection cases were identified in autumn or winter season. The phylogenetic relationships of the 12 EV-D68 viral strains with other strains were analyzed based on the sequences of viral protein 1(VP1). The EV-D68 strains from 2011 to 2013 belonged to groups 1 or 3, while all strains in 2014 were clustered into group 1 together with the strains circulating in the USA. In conclusion, EV-D68 played a role in respiratory infections in Beijing during this period. In addition, the most common EV-D68 strain detected was similar to that circulating in the USA in 2014. J. Med. Virol. 88:1529-1534, 2016. © 2016 Wiley Periodicals, Inc.

[Molecular Detection and Genomic Characterization of Enterovirus D68 among Children with Severe Acute Respiratory Infection in Beijing and Shanghai]

To understand the prevalence and molecular typing of enterovirus D68 among children with severe acute respiratory infection(SARI)in Beijing and Shanghai,259 respiratory samples were collected from in Beijing during 2008-2010,and 441 respiratory samples were collected in Shanghai city between 2013and2014.All the samples were used for the screening of EV-D68 by nest RT-PCR and sequencing, and then EV-D68-positive samples were used for the complete genome sequencing through overlapping PCR. All available EV-D68full-length genomes collected from GenBank were used for phylogenetic analysis and comparison of EV-D68 types prevalent in China and America. One(0.4%)from 259 respiratory samples in Beijing was positive for EV-D68,and 4(0.9%)among the 441 samples from Shanghai were positive for EV-D68.Phylogenetic analysis of full length genome indicated that the EV-D68 prevalent in Beijing belong to Clade A2 and Clade B2,different from the American popular strains(Clade A1,Clade B1,Clade B4 and Clade B5).Partial sequence analysis declared phylogenetic conflict among different gene sequences. We concluded that the prevalence rate of EV-D68 among SARI Children in Beijing and Shanghai currently was lower(5/700;<1%),and the EV-D68 genotype prevalent in China and America belong to different clusters. Partial sequence analysis indicated that intratypic recombinant events may occur in EV-D68 prevalent in China.

Prevalence and phylogenetic characterization of human enterovirus D68 among children with respiratory infection in Hong Kong

This is the first report on the prevalence of human enterovirus D68 (EV-D68) among children with respiratory infection in Hong Kong. Among 1461 respiratory samples taken in 2014, EV-D68 was identified in 24 (1.64%) of them with a unusual seasonal pattern. Phylogenetic analysis indicated that all EV-D68 detected in this study belong to clade B.

Low-level Circulation of Enterovirus D68-Associated Acute Respiratory Infections, Germany, 2014

We used physician sentinel surveillance to identify 25 (7.7%) mild to severe infections with enterovirus D68 (EV-D68) in children and adults among 325 outpatients with acute respiratory infections in Germany during August–October 2014. Results suggested low-level circulation of enterovirus D68 in Germany. Viruses were characterized by sequencing viral protein (VP) 1 and VP4/VP2 genomic regions.

Genetic diversity of human enterovirus 68 strains isolated in Kenya using the hypervariable 3'-end of VP1 gene

Reports of increasing worldwide circulation of human enterovirus-68 (EV68) are well documented. Despite health concerns posed by resurgence of these viruses, little is known about EV68 strains circulating in Kenya. In this study, we characterized 13 EV68 strains isolated in Kenya between 2008 and 2011 based on the Hypervariable 3'-end of the VP1 gene. Viral RNA was extracted from the isolates and partial VP1 gene amplified by RT-PCR, followed by nucleotide sequencing. Alignment of deduced amino acid sequences revealed substitutions in Kenyan EV68 isolates absent in the prototype reference strain (Fermon). The majority of these changes were present in the BC and DE-loop regions, which are associated with viral antigenicity and virulence. The Kenyan strains exhibited high sequence homology with respect to those from other countries. Natural selection analysis based on the VP1 region showed that the Kenyan EV68 isolates were under purifying selection. Phylogenetic analysis revealed that majority (84.6%) of the Kenyan strains belonged to clade A, while a minority belonged to clades B and C. Overall, our results illustrate that although EV68 strains isolated in Kenya were genetically and antigenically divergent from the prototype strain (Fermon), they were closely related to those circulating in other countries, suggesting worldwide transmissibility. Further, the presence of shared mutations by Kenyan EV68 strains and those isolated in other countries, indicates evolution in the VP1 region may be contributing to increased worldwide detection of the viruses. This is the first study to document circulation of EV68 in Kenya.

Molecular epidemiology and evolution of human enterovirus serotype 68 in Thailand, 2006-2011

Background

Publications worldwide have reported on the re-occurrence of human enterovirus 68 (EV68), a rarely detected pathogen usually causing respiratory illness. However, epidemiological data regarding this virus in particular on the Asian continent has so far been limited.

Methodology/Findings

We investigated the epidemiology and genetic variability of EV68 infection among Thai children with respiratory illnesses from 2006–2011 (n = 1810). Semi-nested PCR using primer sets for amplification of the 5′-untranslated region through VP2 was performed for rhino-enterovirus detection. Altogether, 25 cases were confirmed as EV68 infection indicating a prevalence of 1.4% in the entire study population. Interestingly, the majority of samples were children aged >5 years (64%). Also, co-infection with other viruses was found in 28%, while pandemic H1N1 influenza/2009 virus was the most common co-infection. Of EV68-positive patients, 36% required hospitalizations with the common clinical presentations of fever, cough, dyspnea, and wheezing. The present study has shown that EV68 was extremely rare until 2009 (0.9%). An increasing annual prevalence was found in 2010 (1.6%) with the highest detection frequency in 2011 (4.3%). Based on analysis of the VP1 gene, the evolutionary rate of EV68 was estimated at 4.93×10⁻³ substitutions/site/year. Major bifurcation of the currently circulating EV68 strains occurred 66 years ago (1945.31 with (1925.95–1960.46)95% HPD). Among the current lineages, 3 clusters of EV68 were categorized based on the different molecular signatures in the BC and DE loops of VP1 combined with high posterior probability values. Each cluster has branched off from their common ancestor at least 36 years ago (1975.78 with (1946.13–1984.97)95% HPD).

Conclusion

Differences in epidemiological characteristic and seasonal profile of EV68 have been found in this study. Results from Bayesian phylogenetic investigations also revealed that EV68 should be recognized as a genetically diverse virus with a substitution rate identical to that of enterovirus 71 genotype B (4.2×10⁻³ s/s/y).

Emergence and epidemic occurrence of enterovirus 68 respiratory infections in The Netherlands in 2010

Following an increase in detection of enterovirus 68 (EV68) in community surveillance of respiratory infections in The Netherlands in 2010, epidemiological and virological analyses were performed to investigate the possible public health impact of EV68 infections. We retrospectively tested specimens collected from acute respiratory infections surveillance and through three children cohort studies conducted in The Netherlands from 1994 through 2010. A total of 71 of 13,310 (0.5%) specimens were positive for EV68, of which 67 (94%) were from symptomatic persons. Twenty-four (34%) of the EV68 positive specimens were collected during 2010. EV68-positive patients with respiratory symptoms showed significantly more dyspnea, cough and bronchitis than EV68-negative patients with respiratory symptoms. Phylogenetic analysis showed an increased VP1 gene diversity in 2010, suggesting that the increased number of EV68 detections in 2010 reflects a real epidemic. Clinical laboratories should consider enterovirus diagnostics in the differential diagnosis of patients presenting with respiratory symptoms.

Enterovirus 94, a proposed new serotype in human enterovirus species D

The genus Enterovirus (family Picornaviridae) contains five species with strains isolated from humans: Human enterovirus A (HEV-A), HEV-B, HEV-C, HEV-D and Poliovirus. In this study, a proposed new serotype of HEV-D was characterized. Four virus strains were isolated from sewage in Egypt and one strain from acute flaccid paralysis cases in the Democratic Republic of the Congo. The complete genome of one environmental isolate, the complete coding sequence of one clinical isolate and complete VP1 regions from the other isolates were sequenced. These isolates had 66.6–69.4 % nucleotide similarity and 74.7–76.6 % amino acid sequence similarity in the VP1 region with the closest enterovirus serotype, enterovirus 70 (EV70), suggesting that the isolates form a new enterovirus type, tentatively designated enterovirus 94 (EV94). Phylogenetic analyses including sequences of the 5′ UTR, VP1 and 3D regions demonstrated that EV94 isolates formed a monophyletic group within the species HEV-D. No evidence of recombination was found between EV94 and the other HEV-D serotypes, EV68 and EV70. Further biological characterization showed that EV94 was acid stable and had a wide cell tropism in vitro. Attempts to prevent replication with protective antibodies to known enterovirus receptors (poliovirus receptor, vitronectin α v β 3 receptor and decay accelerating factor) were not successful. Seroprevalence studies in the Finnish population revealed a high prevalence of this virus over the past two decades.

Genetic clustering of all 102 human rhinovirus prototype strains: serotype 87 is close to human enterovirus 70

Human rhinoviruses (HRV), common agents of respiratory infections, comprise 102 designated serotypes. The genetic relationships of HRV prototype strains and the possibility of using genetic identification of a given HRV field strain were studied. Genomic sequences in the VP4/VP2 region were obtained from all 102 prototype strains. Phylogenetic analysis included 61 recently isolated Finnish field strains. Seventy-six out of the 102 prototype strains clustered in the HRV genetic group A and 25 in group B. Serotype 87 clustered separately and together with human enterovirus 70. The 'percentage' interserotypic differences were generally similar to those between different enterovirus serotypes, but for six pairs of HRV serotypes they were less than 10%. The maximum variation in genetic group A was 41% at the nucleotide level and 28% at the amino acid level, and in genetic group B 34% and 20%, respectively. Judging from the observed interserotypic differences, the 61 Finnish field isolates might represent as many as 19 different serotypes. One cluster of the field strains did not directly associate with any of the prototype strains and might represent a new serotype. However, larger numbers of field isolates of known serotype need to be characterized, possibly also in the VP1 region, to evaluate the feasibility of genetic typing of HRV strains.