An inactivated whole-virion vaccine for Enterovirus D68 adjuvanted with CpG ODN or AddaVax elicits potent protective immunity in mice

Enterovirus D68 (EV-D68), a pathogen that causes respiratory symptoms, mainly in children, has been implicated in acute flaccid myelitis, which is a poliomyelitis-like paralysis. Currently, there are no licensed vaccines or treatments for EV-D68 infections. Here, we investigated the optimal viral inactivation reagents, vaccine adjuvants, and route of vaccination in mice to optimize an inactivated whole-virion (WV) vaccine against EV-D68. We used formalin, β-propiolactone (BPL), and hydrogen peroxide as viral inactivation reagents and compared their effects on antibody responses. Use of any of these three viral inactivation reagents effectively induced neutralizing antibodies. Moreover, the antibody response induced by the BPL-inactivated WV vaccine was enhanced when adjuvanted with cytosine phosphoguanine oligodeoxynucleotide (CpG ODN) or AddaVax (MF59-like adjuvant), but not with aluminum hydroxide (alum). Consistent with the antibody response results, the protective effect of the inactivated WV vaccine against the EV-D68 challenge was enhanced when adjuvanted with CpG ODN or AddaVax, but not with alum. Further, while the intranasal inactivated WV vaccine induced EV-D68-specific IgA antibodies in the respiratory tract, it was less protective against EV-D68 challenge than the injectable vaccine. Thus, an injectable inactivated EV-D68 WV vaccine prepared with appropriate viral inactivation reagents and an optimal adjuvant is a promising EV-D68 vaccine.

Detection of enterovirus D68 among children with severe acute respiratory infection in Myanmar

BACKGROUND

Enterovirus D68 (EV-D68) is an important reemerging pathogen that causes severe acute respiratory infection and acute flaccid paralysis, mainly in children. Since 2014, EV-D68 outbreaks have been reported in the United States, Europe, and east Asia; however, no outbreaks have been reported in southeast Asian countries, including Myanmar, during the previous 10 years.

METHODS

EV-D68 was detected in nasopharyngeal swabs from children with acute lower respiratory infections in Myanmar. The samples were previously collected from children aged 1 month to 12 years who had been admitted to the Yankin Children Hospital in Yangon, Myanmar, between May 2017 and January 2019. EV-D68 was detected with a newly developed EV-D68-specific real-time PCR assay. The clade was identified by using a phylogenetic tree created with the Bayesian Markov chain Monte Carlo method.

RESULTS

During the study period, nasopharyngeal samples were collected from 570 patients. EV-D68 was detected in 42 samples (7.4 %)-11 samples from 2017 to 31 samples from 2018. The phylogenetic tree revealed that all strains belonged to clade B3, which has been the dominant clade worldwide since 2014. We estimate that ancestors of currently circulating genotypes emerged during the period 1980-2004.

CONCLUSIONS

To our knowledge, this is the first report of EV-D68 detection in children with acute lower respiratory infections in Yangon, Myanmar, in 2017-2018. Detection and detailed virologic analyses of EV-D68 in southeast Asia is an important aspect of worldwide surveillance and will likely be useful in better understanding the worldwide epidemiologic profile of EV-D68 infection.

Predicting the impact of COVID-19 non-pharmaceutical intervention on short- and medium-term dynamics of enterovirus D68 in the US

Recent outbreaks of enterovirus D68 (EV-D68) infections, and their causal linkage with acute flaccid myelitis (AFM), continue to pose a serious public health concern. During 2020 and 2021, the dynamics of EV-D68 and other pathogens have been significantly perturbed by non-pharmaceutical interventions against COVID-19; this perturbation presents a powerful natural experiment for exploring the dynamics of these endemic infections. In this study, we analyzed publicly available data on EV-D68 infections, originally collected through the New Vaccine Surveillance Network, to predict their short- and long-term dynamics following the COVID-19 interventions. Although long-term predictions are sensitive to our assumptions about underlying dynamics and changes in contact rates during the NPI periods, the likelihood of a large outbreak in 2023 appears to be low. Comprehensive surveillance data are needed to accurately characterize future dynamics of EV-D68. The limited incidence of AFM cases in 2022, despite large EV-D68 outbreaks, poses further questions for the timing of the next AFM outbreaks.

Multimodal Surveillance Model for Enterovirus D68 Respiratory Disease and Acute Flaccid Myelitis among Children in Colorado, USA, 2022

Surveillance for emerging pathogens is critical for developing early warning systems to guide preparedness efforts for future outbreaks of associated disease. To better define the epidemiology and burden of associated respiratory disease and acute flaccid myelitis (AFM), as well as to provide actionable data for public health interventions, we developed a multimodal surveillance program in Colorado, USA, for enterovirus D68 (EV-D68). Timely local, state, and national public health outreach was possible because prospective syndromic surveillance for AFM and asthma-like respiratory illness, prospective clinical laboratory surveillance for EV-D68 among children hospitalized with respiratory illness, and retrospective wastewater surveillance led to early detection of the 2022 outbreak of EV-D68 among Colorado children. The lessons learned from developing the individual layers of this multimodal surveillance program and how they complemented and informed the other layers of surveillance for EV-D68 and AFM could be applied to other emerging pathogens and their associated diseases.

A novel mucosal bivalent vaccine of EV-A71/EV-D68 adjuvanted with polysaccharides from Ganoderma lucidum protects mice against EV-A71 and EV-D68 lethal challenge

BACKGROUND

Human enteroviruses A71 (EV-A71) and D68 (EV-D68) are the suspected causative agents of hand-foot-and-mouth disease, aseptic meningitis, encephalitis, acute flaccid myelitis, and acute flaccid paralysis in children. Until now, no cure nor mucosal vaccine existed for EV-A71 and EV-D68. Novel mucosal bivalent vaccines are highly important for preventing EV-A71 and EV-D68 infections.

METHODS

In this study, formalin-inactivated EV-A71 and EV-D68 were used as antigens, while PS-G, a polysaccharide from Ganoderma lucidum, was used as an adjuvant. Natural polysaccharides have the characteristics of intrinsic immunomodulation, biocompatibility, low toxicity, and safety. Mice were immunized intranasally with PBS, EV-A71, EV-D68, or EV-A71 + EV-D68, with or without PS-G as an adjuvant.

RESULTS

The EV-A71 + EV-D68 bivalent vaccine generated considerable EV-A71- and EV-D68-specific IgG and IgA titres in the sera, nasal washes, saliva, bronchoalveolar lavage fluid, and feces. These antibodies neutralized EV-D68 and EV-A71 infectivity. They also cross-neutralized infections by different EV-D68 and EV-A71 sub-genotypes. Furthermore, compared with the PBS group, EV-A71 + EV-D68 + PS-G-vaccinated mice exhibited an increased number of EV-D68- and EV-A71-specific IgA- and IgG-producing cells. In addition, T-cell proliferative responses, and IFN-γ and IL-17 secretion in the spleen were substantially induced when PS-G was used as an adjuvant with EV-A71 + EV-D68. Finally, in vivo challenge experiments demonstrated that the immune sera induced by EV-A71 + EV-D68 + PS-G conferred protection in neonate mice against lethal EV-A71 and EV-D68 challenges as indicated by the increased survival rate and decreased clinical score and viral RNA tissue expression. Taken together, all EV-A71/EV-D68 + PS-G-immunized mice developed potent specific humoral, mucosal, and cellular immune responses to EV-D68 and EV-A71 and were protected against them.

CONCLUSIONS

These findings demonstrated that PS-G can be used as a potential adjuvant for EV-A71 and EV-D68 bivalent mucosal vaccines. Our results provide useful information for the further preclinical and clinical development of a mucosal bivalent enterovirus vaccine against both EV-A71 and EV-D68 infections.

In vitro and in vivo models for the study of EV-D68 infection

Enterovirus D68 (EV-D68) is one of hundreds of non-polio enteroviruses that typically cause cold-like respiratory illness. The first EV-D68 outbreak in the United States in 2014 aroused widespread concern among the public and health authorities. The infection was found to be associated with increased surveillance of acute flaccid myelitis, a neurological condition that causes limb paralysis in conjunction with spinal cord inflammation. In vitro studies utilising two-dimensional (2D) and three-dimensional (3D) culture systems have been employed to elucidate the pathogenic mechanism of EV-D68. Various animal models have also been developed to investigate viral tropism and distribution, pathogenesis, and immune responses during EV-D68 infection. EV-D68 infections have primarily been investigated in respiratory, intestinal and neural cell lines/tissues, as well as in small-size immunocompetent rodent models that were limited to a young age. Some studies have implemented strategies to overcome the barriers by using immunodeficient mice or virus adaptation. Although the existing models may not fully recapitulate both respiratory and neurological disease observed in human EV-D68 infection, they have been valuable for studying pathogenesis and evaluating potential vaccine or therapeutic candidates. In this review, we summarise the methodologies and findings from each experimental model and discuss their applications and limitations.

First Detection of Enterovirus D68 in Korean Children, September 2022

BACKGROUND

Enterovirus D68 (EV-D68) is a re-emerging pathogen that is particularly common in children and may cause asthma-like respiratory infection and acute flaccid myelitis. However, in Korea, EV-D68 has never been reported thus far. This study aimed to identify EV-D68 from nasopharyngeal aspirates (NPAs) in Korean children with a respiratory tract infection.

MATERIALS AND METHODS

The EV-D68 reference strain was purchased and blindly used to assess the detection ability of three commercial and one in-house mRT-PCR kit in 2018. Then, we selected children whose specimens were positive for human rhinovirus (HRV) and/or enterovirus (EV) by Allplex mRT-PCR (Seegene, Inc., Seoul, Korea) from April to December 2022. Total RNA was extracted from NPAs, and a partial 5'-UTR gene was amplified and sequenced for the identification of HRV/EV species. Additionally, PCR targeting the VP1 gene was performed to assess EV-D68-positive NPAs, followed by sequencing. Phylogenetic analysis and comparison of amino acid sequence alignments were performed using a partial VP1 gene of our and recent international EV-D68 strains.

RESULTS

Among the mRT-PCR kits tested, only the in-house kit was able to detect EV-D68 in 2018. However, we detected three EV-D68 strains among children hospitalized with fever and/or respiratory symptoms in September - December 2022 who tested positive for EV by the Allplex kit. Two of them were healthy toddlers with lower respiratory infections accompanied by new-onset wheezing but no neurologic complications. Among 34 children with lower respiratory infection who tested positive for HRV during the same period, EV-D68 was not detected. Phylogenetic analysis revealed that the first Korean EV-D68 belonged to subclade B3. Amino acid sequence alignment of international subclade B3 EV-D68 strains also showed that our strain is genetically more related to those from Europe than those from Japan.

CONCLUSION

We first detected EV-D68 in three Korean children who had EV detected by the Allplex mRT-PCR kit in 2022. EV-D68 also circulated in Korea in fall 2022, but the prevalence and severity seemed to be lower than those in previous reports from other countries.

Clinical and molecular characteristics of the 2022 Enterovirus-D68 outbreak among hospitalized children, Ohio, USA

BACKGROUND

Enterovirus-D68 (EV-D68) has appeared biennially in the United States following the 2014 outbreak. It has gained epidemiologic and clinical relevance and was identified as an important pathogen associated with severe respiratory and central nervous system diseases. We aim to describe the clinical and molecular characteristics of the post-pandemic 2022 Enterovirus-D68 outbreak in children evaluated in a tertiary pediatric hospital in Columbus, Ohio.

METHODS

EV-D68 RT-PCR was performed on nasopharyngeal specimens collected during Jun-Nov 2022 from children (<18 years), identified by 1) physician-order or 2) random selection of 10-15 specimens weekly that were Rhinovirus/Enterovirus-positive by physician-ordered respiratory virus panel. Patients who tested positive for EV-D68 were identified and clinical data and outcomes were analyzed. Partial viral VP1 region was sequenced and characterized.

RESULTS

Forty-four children positive for EV-D68 were identified, among which 88.6 % of patients presented with respiratory symptoms and 61.4 % required PICU admission. Two patients presented with AFM that was attributed to EV-D68. EV-D68 sequences from 2022 clustered within the B3 subclade.

CONCLUSIONS

A significant proportion of children identified with EV-D68 during the 2022 outbreak had respiratory compromise requiring PICU admission. As the virus continues evolving, it is important to monitor the activity of EV-D68, characterizing these strains clinically and genetically, which will help to understand the viral pathogenicity and virulence.

Duration of Enterovirus D68 RNA Shedding in the Upper Respiratory Tract and Transmission among Household Contacts, Colorado, USA

Enterovirus D68 (EV-D68) causes cyclical outbreaks of respiratory disease and acute flaccid myelitis. EV-D68 is primarily transmitted through the respiratory route, but the duration of shedding in the respiratory tract is unknown. We prospectively enrolled 9 hospitalized children with EV-D68 respiratory infection and 16 household contacts to determine EV-D68 RNA shedding dynamics in the upper respiratory tract through serial midturbinate specimen collections and daily symptom diaries. Five (31.3%) household contacts, including 3 adults, were EV-D68-positive. The median duration of EV-D68 RNA shedding in the upper respiratory tract was 12 (range 7-15) days from symptom onset. The most common symptoms were nasal congestion (100%), cough (92.9%), difficulty breathing (78.6%), and wheezing (57.1%). The median illness duration was 20 (range 11-24) days. Understanding the duration of RNA shedding can inform the expected rate and timing of EV-D68 detection in associated acute flaccid myelitis cases and help guide public health measures.

Molecular epidemiology and recombination of enterovirus D68 in China

Enterovirus D68 (EV-D68), a member of Enterovirus genus of the Picornaviridae family, mainly causes respiratory system-related diseases as well as neurological complications in some patients. At present, there is no effective vaccine or treatment for the virus. The aim of this research was to systematically analyse the molecular epidemiology, recombination and changes in the epitope of EV-D68 in China from 2008 to 2022. Through phylogenetic analysis based on VP1 sequences, it was found that there was limited information about EV-D68 infection before 2011 and that EV-D68 infection was dominated by the A2 gene subtype from 2011 to 2013 and the B3 genotype from 2014 to 2018, during which A2 and B3 were coprevalent and alternately prevalent. We also constructed a phylogenetic tree using the EV-D68 full-length genome sequences, and the genotype of each sequence was consistent with that of the VP1 sequence evolutionary tree. Recombination analysis showed that MH341715 underwent intertypic recombination with the A2 genotype MH341729 at the 5' untranslated region (5'UTR) and that P1-P3 underwent recombination with the B3 genotype MH341712. The capsid protein VP1 is one of the most important structural proteins. In VP1, the BC-loop (89-105 amino acids) and DE-loop (140-152 amino acids) are the most variable domains on the surface of the virus and are associated with epitopes. In this study, it was found that the dominant amino acid composition of the BC-loop and DE-loop continued to change with the epidemic of the virus; the amino acid composition also differed in different regions of the same genotypes. The ongoing genomic and molecular epidemiology of EV-D68 remains important for predicting emergence of new viruses and preventing major outbreaks of respiratory diseases.

Insights into the molecular evolution of enterovirus D68

Enterovirus D68 (EV-D68) is a respiratory virus that primarily affects children and has been associated with sporadic outbreaks of respiratory illness worldwide. In the present study, temporal spreading and molecular evolution of EV-D68 clades (A1, A2, B, B1, B2, B3, and C) were evaluated. Bayesian coalescent analysis was performed to study viral evolution. Data from 976 whole-genome sequences (WGSs) collected between 1977 and 2022 were evaluated. For A1, the most recent common ancestor was dated to 2005-04-17 in the USA; for A2 it was 2003-12-23 in China; for B, it was 2003-07-06 in China; for B1, it was 2010-03-21 in Vietnam; for B2, it was 2006-11-25 in Vietnam; for B3, it was 2011-01-15 in China; and for C, it was 2000-06-27 in the USA. The molecular origin of EV-D68 was in Canada in 1995, and later it was disseminated in France in 1997, the USA in 1999, Asia in 2008, the Netherlands in 2009, New Zealand in 2010, Mexico in 2014, Kenya in 2015, Sweden in 2016, Switzerland in 2018, Spain in 2018, Belgium in 2018, Australia in 2018, and Denmark in 2019. In 2022, this virus circulated in the USA. In conclusion, EV-D68 originated in Canada in the 1990s and spread to Europe, Asia, Oceania, Latin America, and Africa.

Seroprevalence of Enterovirus D68 Infection among Humans: A Systematic Review and Meta-Analysis

INTRODUCTION

Human enterovirus D68 (EV-D68), which belongs to enteroviruses of the small RNA family, is a type of enterovirus that can cause acute respiratory tract infection and central nervous system diseases. This study systematically analysed and summarized EV-D68 antibody studies in databases and identified the seropositivity rates of different regions, ages, and sexes.

METHODS

Meta-analysis was performed using STATA 16.0 software. I2 and Q tests were used to analyse the heterogeneity of the included studies. Meta-regression analysis was performed for different groups, and Egger's linear regression analysis was used to evaluate publication bias.

RESULTS

The results of multiple studies indicated that the serological prevalence range of EV-D68 antibody was 17.78-96.69%. The results of the meta-analysis showed that the seropositivity rate of EV-D68 antibody was 76% (95% confidence interval [CI]: 67-84%), among which that of the Chinese population was 74% (95% CI: 61-86%) and that of other countries was 79% (95% CI: 65-91%). At the same time, a subgroup analysis was conducted. The seroprevalence of EV-D68 antibody was related to age but not sex or region.

CONCLUSION

The seropositivity rate was lower in the below 5-year age group; however, it gradually increased with age. The results of this study showed that EV-D68 infection was widespread in the population, and the current clinical infection situation could not reflect the actual epidemic situation of the virus, among which children under 5 years old were vulnerable to infection, which should be given greater attention for epidemic prevention and control.

Serostatus of echovirus 11, coxsackievirus B3 and enterovirus D68 in cord blood: The implication of severe newborn enterovirus infection

BACKGROUND

Maternal transplacental antibody is an important origins of passive immunity against neonatal enterovirus infection. Echovirus 11 (E11) and coxsackievirus B3 (CVB3) are important types causing neonatal infections. There were few investigations of enterovirus D68 (EVD68) infection in neonates. We aimed to investigate the serostatus of cord blood for these three enteroviruses and evaluate the factors associated with seropositivity.

METHODS

We enrolled 222 parturient (gestational age 34-42 weeks) women aged 20-46 years old between January and October 2021. All participants underwent questionnaire investigation and we collected the cord blood to measure the neutralization antibodies against E11, CVB3 and EVD68.

RESULTS

The cord blood seropositive rates were 18% (41/222), 60% (134/232) and 95% (211/222) for E11, CVB3 and EVD68, respectively (p < 0.001). Geometric mean titers were 3.3 (95% CI 2.9-3.8) for E11, 15.9 (95% CI 12.5-20.3) for CVB3 and 109.9 (95% CI 92.4-131.6) for EVD68. Younger parturient age (33.8 ± 3.6 versus 35.2 ± 4.4, p = 0.04) was related to E11 seropositivity. Neonatal sex, gestational age and birth body weight were not significantly different between the seropositive group and the seronegative group.

CONCLUSION

Cord blood seropositive rate and geometric mean titer of E11 were very low, so a large proportion of newborns are susceptible to E11. The circulation of E11 was low after 2019 in Taiwan. A large cohort of immune naïve newborns existed currently due to lack of protective maternal antibodies. It is imminent to monitor the epidemiology of neonates with enterovirus infections and strengthen the relevant preventive policies.

Neutralizing activity of intravenous immune globulin products against enterovirus D68 strains isolated in Japan

BACKGROUND

Enterovirus D68 (EV-D68), belonging to Enterovirus D, is a unique human enterovirus mainly associated with common respiratory diseases. However, EV-D68 can cause severe respiratory diseases, and EV-D68 endemic is epidemiologically linked to current global epidemic of acute flaccid myelitis.

METHODS

In this study, we measured neutralizing antibody titers against six clinical EV-D68 isolates in nine intravenous immune globulin (IVIG) products commercially available in Japan to assess their potential as therapeutic options for severe EV-D68 infection.

RESULTS

Seven IVIG products manufactured from Japanese donors contained high neutralizing antibody titers (IC₅₀ = 0.22-85.01 µg/mL) against all six EV-D68 strains. Apparent differences in neutralizing titers among the six EV-D68 strains were observed for all IVIG products derived from Japanese and non-Japanese blood donors.

CONCLUSIONS

High levels of EV-D68-neutralizing antibodies in IVIG products manufactured from Japanese donors suggest that anti-EV-D68 antibodies are maintained in the Japanese donor population similarly as found in foreign blood donors. Apparent differences in neutralizing antibody titers against the six EV-D68 strains suggest distinct antigenicity among the strains used in this study regardless of the genetic similarity of EV-D68.

Changes in transmission of Enterovirus D68 (EV-D68) in England inferred from seroprevalence data

The factors leading to the global emergence of Enterovirus D68 (EV-D68) in 2014 as a cause of acute flaccid myelitis (AFM) in children are unknown. To investigate potential changes in virus transmissibility or population susceptibility, we measured the seroprevalence of EV-D68-specific neutralising antibodies in serum samples collected in England in 2006, 2011, and 2017. Using catalytic mathematical models, we estimate an approximately 50% increase in the annual probability of infection over the 10-year study period, coinciding with the emergence of clade B around 2009. Despite such increase in transmission, seroprevalence data suggest that the virus was already widely circulating before the AFM outbreaks and the increase of infections by age cannot explain the observed number of AFM cases. Therefore, the acquisition of or an increase in neuropathogenicity would be additionally required to explain the emergence of outbreaks of AFM. Our results provide evidence that changes in enterovirus phenotypes cause major changes in disease epidemiology.

Development of RT-qPCR for quantification of human enterovirus D68 in vitro

The common cold is the most frequent viral infectious disease of the upper respiratory tract with different intensities based on the serotype and the characteristics of the virus. Numerous human rhinoviruses have been identified and classified. Human rhinovirus 87 (HRV87), also known as enterovirus D68 (EV-D68), is one of the common viruses causing respiratory infections. In this study, a reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assay was developed, optimized, and validated for the detection of EV-D68. Method development also covers specificity, sensitivity, efficiency, and inter-and-intra-assay variations. Overall, this one-step qPCR assay will permit quantitative assessments of human enterovirus D68 RNA.•Enterovirus D68 is a reemerging viral agent causing respiratory infection.•RT-qPCR assay developed for detection of human enterovirus D68.•In this article validation to secure reproducibility is done according to MIQE guidelines.

Qualitative detection of enterovirus D68 from PrimeStore® molecular transport medium: implications for home- and self-collection

To ensure proper specimen handling for detecting pathogens, like Enterovirus D68 (EV-D68), from home- and self-collection, alternative techniques are needed to ensure safe transport and reliable testing. PrimeStore® Molecular Transport Medium (MTM) may be an option since it does not require cold storage and inactivates virus while preserving RNA for detection. The purpose of this validation study was to demonstrate the ability to detect EV-D68 via rRT-PCR in MTM. Using a quantified EV-D68 positive control standard, MTM limit of detection for EV-D68 RNA is 10⁴ cp/mL and RNA remains stable up to 30 days unfrozen. Positive and negative residual respiratory specimens from the 2018 EV-D68 outbreak were used for clinical testing. There was an 80% positive and 100% negative agreement with samples in MTM compared to reference. This study demonstrates the feasibility of EV-D68 detection from respiratory specimens collected and stored in PrimeStore® MTM, with implications for home- and self-collection.

Pediatric acute flaccid myelitis: Evaluation of diagnostic criteria and differentiation from other causes of acute flaccid paralysis

BACKGROUND

Acute flaccid paralysis (AFP) is characterized by rapidly progressive limb weakness with low muscle tone. It has a broad differential diagnosis, which includes acute flaccid myelitis (AFM), a rare polio-like condition that mainly affects young children. Differentiation between AFM and other causes of AFP may be difficult, particularly at onset of disease. Here, we evaluate the diagnostic criteria for AFM and compare AFM to other causes of acute weakness in children, aiming to identify differentiating clinical and diagnostic features.

METHODS

The diagnostic criteria for AFM were applied to a cohort of children with acute onset of limb weakness. An initial classification based on positive diagnostic criteria was compared to the final classification, based on application of features suggestive for an alternative diagnosis and discussion with expert neurologists. Cases classified as definite, probable, or possible AFM or uncertain, were compared to cases with an alternative diagnosis.

RESULTS

Of 141 patients, seven out of nine patients initially classified as definite AFM, retained this label after further classification. For probable AFM, this was 3/11, for possible AFM 3/14 and for uncertain 11/43. Patients initially classified as probable or possible AFM were most commonly diagnosed with transverse myelitis (16/25). If the initial classification was uncertain, Guillain-Barré syndrome was the most common diagnosis (31/43). Clinical and diagnostic features not included in the diagnostic criteria, were often used for the final classification.

CONCLUSION

The current diagnostic criteria for AFM usually perform well, but additional features are sometimes required to distinguish AFM from other conditions.

Enterovirus D68 in Hospitalized Children, Barcelona, Spain, 2014-2021

To determine molecular epidemiology and clinical features of enterovirus D68 (EV-D68) infections, we reviewed EV-D68–associated respiratory cases at a hospital in Barcelona, Spain, during 2014–2021. Respiratory samples were collected from hospitalized patients or outpatients with symptoms of acute respiratory tract infection or suggestive of enterovirus infection. Enterovirus detection was performed by real-time multiplex reverse transcription PCR and characterization by phylogenetic analysis of the partial viral protein 1 coding region sequences. From 184 patients with EV-D68 infection, circulating subclades were B3 (80%), D1 (17%), B2 (1%), and A (<1%); clade proportions shifted over time. EV-D68 was detected mostly in children (86%) and biennially (2016, 2018, 2021). In patients <16 years of age, the most common sign/symptom was lower respiratory tract infection, for which 11.8% required pediatric intensive care unit admission and 2.3% required invasive mechanical ventilation; neurologic complications developed in 1. The potential neurotropism indicates that enterovirus surveillance should be mandatory.

Transcriptomic Profiling Reveals a Role for TREM-1 Activation in Enterovirus D68 Infection-Induced Proinflammatory Responses

Increasing cases related to the pathogenicity of Enterovirus D68 (EV-D68) have made it a growing worldwide public health concern, especially due to increased severe respiratory illness and acute flaccid myelitis (AFM) in children. There are currently no vaccines or medicines to prevent or treat EV-D68 infections. Herein, we performed genome-wide transcriptional profiling of EV-D68-infected human rhabdomyosarcoma (RD) cells to investigate host-pathogen interplay. RNA sequencing and subsequent experiments revealed that EV-D68 infection induced a profound transcriptional dysregulation of host genes, causing significantly elevated inflammatory responses and altered antiviral immune responses. In particular, triggering receptor expressed on myeloid cells 1 (TREM-1) is involved in highly activated TREM-1 signaling processes, acting as an important mediator in EV-D68 infection, and it is related to upregulation of interleukin 8 (IL-8), IL-6, IL-12p70, IL-1β, and tumor necrosis factor alpha (TNF-α). Further results demonstrated that NF-κB p65 was essential for EV-D68-induced TREM-1 upregulation. Moreover, inhibition of the TREM1 signaling pathway by the specific inhibitor LP17 dampened activation of the p38 mitogen-activated protein kinase (MAPK) signaling cascade, suggesting that TREM-1 mainly transmits activation signals to phosphorylate p38 MAPK. Interestingly, treatment with LP17 to inhibit TREM-1 inhibited viral replication and infection. These findings imply the pathogenic mechanisms of EV-D68 and provide critical insight into therapeutic intervention in enterovirus diseases.

High throughput sequencing of whole transcriptome and construct of ceRNA regulatory network in RD cells infected with enterovirus D68

Background

With the advancement of sequencing technologies, a plethora of noncoding RNA (ncRNA) species have been widely discovered, including microRNAs (miRNAs), circular RNAs (circRNAs), and long ncRNAs (lncRNAs). However, the mechanism of these non-coding RNAs in diseases caused by enterovirus d68 (EV-D68) remains unclear. The goal of this research was to identify significantly altered circRNAs, lncRNAs, miRNAs, and mRNAs pathways in RD cells infected with EV-D68, analyze their target relationships, demonstrate the competing endogenous RNA (ceRNA) regulatory network, and evaluate their biological functions.

Methods

The total RNAs were sequenced by high-throughput sequencing technology, and differentially expressed genes between control and infection groups were screened using bioinformatics method. We discovered the targeting relationship between three ncRNAs and mRNA using bioinformatics methods, and then built a ceRNA regulatory network centered on miRNA. The biological functions of differentially expressed mRNAs (DEmRNAs) were discovered through GO and KEGG enrichment analysis. Create a protein interaction network (PPI) to seek for hub mRNAs and learn more about protein–protein interactions. The relative expression was verified using RT-qPCR. The effects of Fos and ARRDC3 on virus replication were confirmed using RT-qPCR, virus titer (TCID₅₀/ml), Western blotting.

Results

375 lncRNAs (154 upregulated and 221 downregulated), 33 circRNAs (32 upregulated and 1 downregulated), 96 miRNAs (49 upregulated and 47 downregulated), and 239 mRNAs (135 upregulated and 104 downregulated) were identified as differently in infected group compare to no-infected group. A single lncRNA or circRNA can be connected with numerous miRNAs, which subsequently coregulate additional mRNAs, according to the ceRNA regulatory network. The majority of DEmRNAs were shown to be connected to DNA binding, transcription regulation by RNA polymerase II, transcription factor, MAPK signaling pathways, Hippo signal pathway, and apoptosis pathway, according to GO and KEGG pathway enrichment analysis. The hub mRNAs with EGR1, Fos and Jun as the core were screened through PPI interaction network. We preliminarily demonstrated that the Fos and ARRDC3 genes can suppress EV-D68 viral replication in order to further verify the results of full transcriptome sequencing.

Conclusion

The results of whole transcriptome analysis after EV-D68 infection of RD cells were first reported in this study, and for the first time, a ceRNA regulation network containing miRNA at its center was established for the first time. The Fos and ARRDC3 genes were found to hinder viral in RD cells. This study establishes a novel insight host response during EV-D68 infection and further investigated potential drug targets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-021-01686-x.

The expression of IFN-β is suppressed by the viral 3D polymerase via its impact on PGAM5 expression during enterovirus D68 infection

Enterovirus D68 (EV-D68) belongs to the Picornaviridae family and can lead to severe clinical manifestations in the respiratory system. The 3D-polymerase (3D^poly) is an important nonstructural protein during EV-D68 replication, but few studies have addressed its interaction with the host antiviral response during EV-D68 infection. Here, we used human bronchial epithelial cells to investigate the impact of the 3D^poly on the mitochondrial dynamics and innate immune response. The results showed that the number and morphology of the mitochondria in 16HBE cells was affected during the early stage of infection, and these effects included the cellular apoptosis. Moreover, we found that the 3D^poly of EV-D68 can interact with PGAM5 and promote mitofusin 2 protein upregulation, and subsequently, 3D^poly impairs IFN-β expression by impacting the activation of the RIG-I receptor signaling pathway. Our findings suggest that during EV-D68 replication, the 3D^poly, via its interaction with PGAM5, can affect the mitochondrial dynamics and suppress the expression of IFN-β by impacting the RIG-I-like receptor signal pathway.

The pathogenesis and virulence of enterovirus-D68 infection

In 2014, enterovirus D68 (EV-D68) emerged causing outbreaks of severe respiratory disease in children worldwide. In a subset of patients, EV-D68 infection was associated with the development of central nervous system (CNS) complications, including acute flaccid myelitis (AFM). Since then, the number of reported outbreaks has risen biennially, which emphasizes the need to unravel the systemic pathogenesis in humans. We present here a comprehensive review on the different stages of the pathogenesis of EV-D68 infection – infection in the respiratory tract, systemic dissemination and infection of the CNS – based on observations in humans as well as experimental in vitro and in vivo studies. This review highlights the knowledge gaps on the mechanisms of systemic dissemination, routes of entry into the CNS and mechanisms to induce AFM or other CNS complications, as well as the role of virus and host factors in the pathogenesis of EV-D68.

Development of an experimental inactivated vaccine from Vero cell adapted Enterovirus D68

Enterovirus D68 is an emerging respiratory disease pathogen causing multiple outbreaks worldwide. Enterovirus D68 strain US/KY/14-18953 was adapted to propagate in Vero cells resulting alteration of seven amino acids. The Vero cell adapted virus was inactivated with Formalin and immunized in mice. Formalin inactivated vaccine elicited high virus specific IgG antibody titer and neutralization titer. Avidity of the IgG antibodies elicited by two different doses of formalin inactivated vaccine is moderately high which got augmented by alum adjuvanted formulations. Formalin inactivated unadjuvanted vaccine elicited a balanced IgG1 type and IgG2a type antibody indicating a more balanced Th2/Th1 type immune response while alum formulated formalin inactivated antigen elicited significantly high IgG1 antibody in immunized sera and Th2 cytokines in mice splenocytes denoting Th2 type T cell immune response. Additionally, the formalin inactivated vaccine formulations has displayed excellent serum mediated invivo protective efficacy. These data suggested that formalin inactivated Enterovirus D68 is a promising vaccine candidate.

The role of conformational epitopes in the evolutionary divergence of enterovirus D68 clades: A bioinformatics-based study

Enterovirus D68 (EV-D68), as one of the major pathogens of paediatric respiratory disease, has been widely spread in the population in recent years. As the basis of virus antigenicity, antigenic epitopes are essential to monitoring the transformation of virus antigenicity. However, there is a lack of systematic studies on the antigenic epitopes of EV-D68. In this study, a bioinformatics-based prediction algorithm for human enteroviruses was used to predict the conformational epitopes of EV-D68. The prediction results showed that the conformational epitopes of EV-D68 were clustered into three sites: site 1, site 2, and site 3. Site 1 was located in the "north rim" region of the canyon near the fivefold axis; site 2 was located in the "puff" region near the twofold axis; and site 3 consisted of two parts, one in the "knob" region on the south rim of the canyon and the other in the threefold axis region. The predicted epitopes overlapped highly with the binding regions of four reported monoclonal antibodies (mAbs), indicating that the predictions were highly reliable. Phylogenetic analysis showed that amino acid mutations in the epitopes of the VP1 BC loop, DE loop, C-terminus, and VP2 EF loop played a crucial role in the evolutionary divergence of EV-D68 clades/subclades and epidemics. This finding indicated that the VP1 BC loop, DE loop, C-terminus, and VP2 EF loop were the most important epitopes of EV-D68. Research on the epitopes of EV-D68 will contribute to outbreak surveillance and to the development of diagnostic reagents and recombinant vaccines.

Enterovirus D68 in hospitalized children with respiratory symptoms in Guangdong from 2014 to 2018: Molecular epidemiology and clinical characteristics

BACKGROUND

Enterovirus D68 (EV-D68) is an emerging pathogen in humans. EV-D68 causes a wide range of respiratory symptoms in children and has the propensity to cause severe complications. EV-D68 outbreaks are rarely investigated in mainland China. Therefore, in this study, we aimed to investigate the prevalence of EV-D68 in children and to describe the clinical manifestations as well as the phylogeny of EV-D68 in Guangdong Province from 2014 to 2018.

METHODS

Nasopharyngeal swabs were collected from hospitalized children with respiratory symptoms and screened for respiratory pathogens by fluorescence quantitative PCR and culture. The EV-positive samples were subsequently typed by sequencing the 5'-untranslated region and EV-D68-specific VP1 capsid gene. A phylogenetic tree was constructed by the maximum-likelihood method based on the VP1 gene using ClustalW.

RESULTS

A total of 1,498 (59.8%) out of 2,503 children were screened positive for ≥1 virus species. Among the 158 (6.31%) EV-positive samples, 17 (0.68%) were identified as EV-D68. Most EV-D68 cases (n = 14) were diagnosed with pneumonia and bronchial pneumonia. No deaths were found in EV-D68 cases. Wheezing occurred in EV-D68 cases more frequently (70.59% vs. 43.26%, P = 0.040) than that of other EVs. All the EV-D68 were of clade B3, which were highly similar to the strains circulating in China.

CONCLUSION

EV-D68 was the predominant enterovirus type in hospitalized children with respiratory symptoms in Guangdong Province. All the EV-D68 strains belong to clade B3. The development of diagnostic tools is warranted in order to monitor EV-D68 infections in China.

Genetic analysis of Enterovirus D68 associated with pneumonia in children from South India

EV-D68 is an emerging enterovirus infection associated with severe acute respiratory illness (SARI), acute flaccid myelitis (AFM) and acute flaccid paralysis (AFP). While EV-D68 outbreaks and sporadic cases are reported globally, a single case has been reported from India. The present study aims to investigate the molecular epidemiology and clinical characteristics of EV-D68-associated SARI cases from South India. We screened influenza-negative archived throat swab specimens from Influenza-Like Illness (ILI) and SARI cases (n=959; 2016 to 2018 period) for enteroviruses by pan-enterovirus real-time RT-PCR. Thirteen samples positive for enteroviruses were typed by PCR and sequencing based on VPI, VP2 and/or 5'NCR regions. One EV-D68 RNA sample was subjected to next-generation sequencing for whole genome characterisation. Among 13 enterovirus cases, four were ECHO-11, three EV-D68, two CV-A16 and one each EV-71, CV-B1, CV-B2 and CV-A9. All three cases of EV-D68 infection were reported in children below 2 years of age from Kerala state of South India during June and July 2017. The patients developed pneumonia without any neurological complications. Sequencing based on VPI and 5'NCR regions showed that EV-D68 strains belong to the novel subclade B3. The EV-D68 complete genome identified with two unique amino acid substitutions in VP1 (T-246-I) and 3D (K-344-R) regions. This study reiterates the EV-D68 novel subclade B3 circulation in India and indicates the urgent need for structured EV-D68 surveillance in the country to describe the epidemiology.

Acute flaccid paralysis and neurogenic respiratory failure associated with enterovirus D68 infection in children: Report of two cases

BACKGROUND

Acute flaccid paralysis (AFP) and neurogenic respiratory failure rarely occur in children. At the end of 2018, some children with such symptoms were admitted to our hospital. In this study, we aimed to assess two children with AFP and neurogenic respiratory failure associated with enterovirus D68 (EV-D68).

CASE SUMMARY

Two children admitted to our hospital presented with symptoms and imaging results different from those of acute disseminated encephalomyelitis and hand, foot, and mouth disease. Their main symptoms were AFP and neurogenic respiratory failure. Magnetic resonance imaging showed severe inflammatory injury mainly to the anterior horn cells of the spinal cord. Blood and cerebrospinal fluid samples were collected to assess for pathogens, including bacteria, tuberculosis, cryptococcus, herpes virus, and coxsackie virus, and the results were negative. At the beginning, the two cases were not assessed for EV-D68 in the nasopharyngeal, blood, and cerebrospinal fluid specimens. About 2 mo later, EV-D68 was detected in the stool sample of one of the cases. The symptom of AFP was caused by injury to the anterior horn cells at levels C5-L5 of the spinal cord, while neurogenic respiratory failure was at levels C3-C5.

CONCLUSION

We should pay attention to the detection and diagnosis of EV-D68 and make efforts to develop antivirus drugs and vaccines.

Regulation of the proteostasis network during enterovirus infection: A feedforward mechanism for EV-A71 and EV-D68

The proteostasis network guarantees successful protein synthesis, folding, transportation, and degradation. Mounting evidence has revealed that this network maintains proteome integrity and is linked to cellular physiology, pathology, and virus infection. Human enterovirus A71 (EV-A71) and EV-D68 are suspected causative agents of acute flaccid myelitis, a severe poliomyelitis-like neurologic syndrome with no known cure. In this context, further clarification of the molecular mechanisms underlying EV-A71 and EV-D68 infection is paramount. Here, we summarize the components of the proteostasis network that are intercepted by EV-A71 and EV-D68, as well as antivirals that target this network and may help develop improved antiviral drugs.

Enterovirus D68 infection among hospitalized children with severe acute respiratory illness in El Salvador and Panama, 2012-2013

We assessed EV‐D68 epidemiology and phylogenetics among children aged ≤9 years hospitalized with severe acute respiratory illnesses at five sites in Panama and El Salvador during 2012‐2013. Respiratory specimens positive for enterovirus or rhinovirus were tested by real‐time RT‐PCR for EV‐D68, and partial VP1 gene sequences were determined. Of 715 enrolled children, 17 from sites in both countries were EV‐D68‐positive and commonly had a history of asthma or wheezing. Phylogenetically, 15 of 16 sequences fell into Clade B1, and one into Clade A2. The Central American EV‐D68s were closely related genetically to contemporaneous strains from North America, South America, and the Caribbean.

Combating SARS-CoV-2: leveraging microbicidal experiences with other emerging/re-emerging viruses

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan City, China, late in December 2019 is an example of an emerging zoonotic virus that threatens public health and international travel and commerce. When such a virus emerges, there is often insufficient specific information available on mechanisms of virus dissemination from animal-to-human or from person-to-person, on the level or route of infection transmissibility or of viral release in body secretions/excretions, and on the survival of virus in aerosols or on surfaces. The effectiveness of available virucidal agents and hygiene practices as interventions for disrupting the spread of infection and the associated diseases may not be clear for the emerging virus. In the present review, we suggest that approaches for infection prevention and control (IPAC) for SARS-CoV-2 and future emerging/re-emerging viruses can be invoked based on pre-existing data on microbicidal and hygiene effectiveness for related and unrelated enveloped viruses.

Pharmacological Characterization of the Mechanism of Action of , a Promising Antiviral for Enterovirus D68

Enterovirus D68 (EV-D68) is a re-emerging virus that causes moderate to severe respiratory diseases in children. In severe cases, EV-D68 infection can lead to neurological complications called acute flaccid myelitis (AFM). There is currently no antiviral or vaccine available for EV-D68. The goal of this study is to delineate the mechanism of action of a promising antiviral drug candidate R523062 that was identified through a phenotypic cytopathic effect (CPE)-based high-throughput screening. R523062 inhibits multiple contemporary EV-D68 strains with single-digit micromolar EC50 values and is less effective against the enterovirus A71 strains. Resistant mutants identified through serial viral passage experiments were mapped to four viral proteins including VP1-G178S, 2A-V112I, 2C-I227L/Q322R, and 3A-V54A. The involvements of VP1-G178S, 2A-V112I, and 3A-V54A mutants in drug resistance were ruled out by the drug time-of-addition experiment, protease enzymatic assay, and the plaque assay with recombinant virus, respectively. In contrast, recombinant virus encoding the 2C-I227L/Q322R double mutants confers significant drug resistance, which is consistent with the result from serial passage experiments. The thermal shift binding assay showed R523062 binds to the wild-type EV-D68 2C and 2C-Q322R but not 2C-I227L or 2C-I227L/Q322R, confirming 2C as the direct drug target of R523062 and 2C-I227L alone confers drug resistance. The 2C inhibitor R523062 also showed additive antiviral activity with the viral 2A protease inhibitor telaprevir as well as the viral capsid VP1 inhibitor R856932. Collectively, this study identified a promising EV-D68 antiviral drug candidate R523062 with a confirmed mechanism of action by targeting the viral 2C protein.

Structure of the enterovirus D68 RNA-dependent RNA polymerase in complex with NADPH implicates an inhibitor binding site in the RNA template tunnel

Enterovirus D68 (EV-D68) is an emerging viral pathogen belonging to the Enterovirus genus of the Picornaviridae family, which is a serious threat to human health and has resulted in significant economic losses. The EV-D68 genome encodes an RNA-dependent RNA polymerase (RdRp) 3D^pol, which is central for viral genome replication and considered as a promising target for specific antiviral therapeutics. In this study, we report the crystal structures of human EV-D68 RdRp in the apo state and in complex with the inhibitor NADPH, which was selected by using a structure-based virtual screening approach. The EV-D68-RdRp-NADPH complex is the first RdRp-inhibitor structure identified in the species Enterovirus D. The inhibitor NADPH occupies the RNA template binding channel of EV-D68 RdRp with a novel binding pocket. Additionally, residues involved in the NADPH binding pocket of EV-D68 RdRp are highly conserved in RdRps of enteroviruses. Therefore, the enzyme activity of three RdRps from EV-D68, poliovirus, and enterovirus A71 is shown to decrease when titrated with NADPH separately in vitro. Furthermore, we identified that NADPH plays a pivotal role as an RdRp inhibitor instead of a chain terminator during restriction of RNA-dependent RNA replication. In the future, derivatives of NADPH may pave the way for novel inhibitors of RdRp through compound modification, providing potential antiviral agents for treating enteroviral infection and related diseases.

Receptor-Binding Assays of Enterovirus D68

Human enterovirus D68 (EV-D68) is a causative agent for acute respiratory infections and potentially central nervous system illnesses with increasing epidemiological significance. Recent studies have highlighted the role of sialic acids as a functional receptor for EV-D68 in vitro. However, further investigations are required to reveal its significance in actual infections in human.

Methyl-β-cyclodextrin inhibits EV-D68 virus entry by perturbing the accumulation of virus particles and ICAM-5 in lipid rafts

Enterovirus D68 (EV-D68) is a member of the Picornavirus family and a causative agent of respiratory diseases in children. The incidence of EV-D68 infection has increased worldwide in recent years. Thus far, there are no approved antiviral agents or vaccines for EV-D68. Here, we show that methyl-β-cyclodextrin (MβCD), a common drug that disrupts lipid rafts, specifically inhibits EV-D68 infection without producing significant cytotoxicity at virucidal concentrations. The addition of exogenous cholesterol attenuated the anti-EV-D68 activity of MβCD. MβCD treatment had a weak influence on the attachment of viral particles to the cell membrane but significantly inhibited EV-D68 entry into host cells. We demonstrated that EV-D68 facilitated the translocation of the viral receptor ICAM-5 to membrane rafts in infected cells. The colocalization of viral particles with ICAM-5 in lipid rafts was thoroughly abolished in cells after treatment with MβCD. Finally, we showed that MβCD inhibited the replication of isolated circulating EV-D68 strains. In summary, our results demonstrate that MβCD suppresses EV-D68 replication by perturbing the accumulation of virus particles and ICAM-5 in lipid rafts. This mechanism represents a promising strategy for drug development.

Enterovirus D68 in a 6-year-old acute flaccid myelitis case in China, 2018: a case report

BACKGROUND

Acute flaccid myelitis (AFM) are reported to be associated with enterovirus D68 infection. Though an increasing number of AFM cases were reported with EV-D68 infection in the US, few such cases have been found in China.

CASE PRESENTATION

A 6-year-old boy presented with acute flaccid myelitis (AFM) involving left arm after fever and respiratory symptoms for 6 days. Computed Tomography (CT) revealed inflammation in both lungs and magnetic resonance imaging (MRI) of the brain and spine showed swelling in the left frontal lobe and brain stem. The patient was diagnosed with meningomyelitis. EV-D68 was detected from pharyngeal samples 36 days after the onset of the disease.

CONCLUSION

We report the first EV-D68 infection in case of AFM in mainland China. AFM surveillance systems is recommended to be established in China to guide diagnosis, case reporting, and specimen collection and testing for better understanding its etiologies.

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.

A case report of the enterovirus-D68 associated severe acute respiratory illness in a pediatric case from India

Since, early 2000s, there have been several clusters of enterovirus-D68 (EV D68) associated respiratory illness reported from various countries. Recent largest and most wide-spread outbreak of EV-D68 associated severe acute respiratory illness (SARI) occurred in North America. Present report describes a case of EV-D68 associated severe acute respiratory illness from India with a whole genome sequence. The case was identified through retrospective analysis of Influenza SARI surveillance sample collected during September 2017 using Next Generation sequencing. EV D68 positive child aged two years and presented with asthma like symptoms for which he was admitted to ICU. The child tested negative for Influenza, RSV, Rhinovirus, PIV, hMPV and adenovirus, on real time RT-PCR. And on NGS full EV D68 genome was retrieved belonging to sub-clade B3. In ICU, child received anti-bacterial and anti-viral therapy. The child recovered with-out any sequelae and was discharged one week later. Present report highlights the importance of studying this emergent virus EV-D68 through prospective studies to understand the burden and epidemiological pattern in the country and its implications.

Acute flaccid myelitis associated with enterovirus D68 in a non-epidemic setting

Acute flaccid myelitis (AFM) is a recently defined clinical disease accompanied by the national outbreak of enterovirus D68 (EV-D68) in the United States during the late summer/fall of 2014; 258 cases of EV-D68 and 59 cases of AFM were reported in Japan during the late summer/fall of 2015. Subsequently, there have been no epidemics of AFM or EV-D68. However, we encountered a patient who had AFM associated with EV-D68 in 2017. This is the first case of AFM caused by EV-D68 after the 2015 epidemic, and the only reported case in 2017. This report indicates that AFM caused by EV-D68 can arise even in non-epidemic situations. If a patient presents with paralysis, AFM caused by EV-D68 should be included in the differential diagnosis, regardless of the absence of an epidemic of EV-D68 infection.

Acute flaccid myelitis caused by enterovirus D68: Case definitions for use in clinical practice

Acute flaccid myelitis (AFM) was increasingly detected in recent years, coinciding with upsurges of enterovirus D68 (EV-D68) infections. We reviewed the evidence for a causal relationship between both. Based on reported cases, we provide case definitions for AFM caused by EV-D68 infections to enable a standard procedure for affected patients. Current case definitions are focussing on epidemiological aspects but clinical case definitions are still missing. We propose the following case definitions to be used in clinical practice in order to mirror clinical realities and facilitate a common systematic approach in case management: A possible case is defined as a person presenting with either acute myelitis/paralysis or Guillain-Barré Syndrome (GBS), particularly during periods of EV-D68 circulation. A probable case is defined as a person presenting with symptoms of either acute myelitis/paralysis or GBS and at least one of the following criteria: i) MRI abnormality representing with T2 hyperintensity in spinal cord grey matter with or without hyperintensity at dorsal brain stem, ii) investigations showing an axonal neuropathy including reduced compound motor action potentials with normal conduction velocities and absence of conduction blocks compatible with anterior horn cell disease or iii) detection of enteroviruses in a respiratory specimen obtained from the lower respiratory tract during periods of EV-D68 circulation. A confirmed case is defined as a person presenting with acute flaccid myelitis/paralysis, MRI abnormality and detection of enterovirus-D68-specific nucleic acids in a respiratory specimen using a validated PCR assay targeting the VP1 gene with subsequent sequencing and typing.

Acute flaccid myelitis and enterovirus D68: lessons from the past and present

Acute flaccid myelitis is characterized by the combination of acute flaccid paralysis and a spinal cord lesion largely restricted to the gray matter on magnetic resonance imaging. The term acute flaccid myelitis was introduced in 2014 after the upsurge of pediatric cases in the USA with enterovirus D68 infection. Since then, an increasing number of cases have been reported worldwide. Whereas the terminology is new, the clinical syndrome has been recognized in the past in association with several other neurotropic viruses such as poliovirus.Conclusion: This review presents the current knowledge on acute flaccid myelitis with respect to the clinical presentation and its differential diagnosis with Guillain-Barré syndrome and acute transverse myelitis. We also discuss the association with enterovirus D68 and the presumed pathophysiological mechanism of this infection causing anterior horn cell damage. Sharing clinical knowledge and insights from basic research is needed to make progress in diagnosis, treatment, and prevention of this new polio-like disease. What is Known: • Acute flaccid myelitis (AFM) is a polio-like condition characterized by rapid progressive asymmetric weakness, together with specific findings on MRI • AFM has been related to different viral agents, but recent outbreaks are predominantly associated with enterovirus D68. What is New: • Improving knowledge on AFM must increase early recognition and adequate diagnostic procedures by clinicians. • The increasing incidence of AFM urges cooperation between pediatricians, neurologists, and microbiologists for the development of treatment and preventive options.

Development of a respiratory disease model for enterovirus D68 in 4-week-old mice for evaluation of antiviral therapies

Enterovirus D68 (EV-D68) is a non-polio enterovirus that affects the respiratory system and can cause serious complications, especially in children and older people with weakened immune systems. As an emerging virus, there are no current antiviral therapies or vaccines available. Our goal was to develop a mouse model of human EV-D68 infection that mimicked the disease observed in humans and could be used for evaluation of experimental therapeutics. This is the first report of a respiratory disease model for EV-D68 infection in mice. We adapted the virus by 30 serial passages in AG129 mice, which are deficient in IFN- α/β and -γ receptors. Despite a lack of weight loss or mortality in mice, lung function measured by plethysmography, showed an increase in enhanced pause (Penh) on days 6 and 7 post-infection. In addition, as virus adapted to mice, virus titer in the lungs increased 50-fold, and the pro-inflammatory cytokines MCP-1 and RANTES increased 15-fold and 2-fold in the lung, respectively. In addition, a time course of mouse-adapted EV-D68 infection was determined in lung, blood, liver, kidney, spleen, leg muscle, spinal cord and brain. Virus in the lung replicated rapidly after intranasal inoculation of adapted virus, 10⁶ CCID₅₀/mL by 4 h and 10^8.3 CCID₅₀/mL by 24 h. Virus then spread to the blood and other tissues, including spinal cord and brain. This mouse model for EV-D68 infection includes enhanced pause (Penh) as an indicator of morbidity, and viremia, virus titers and proinflammatory cytokines in the lung, and lung histopathology as indicators of disease. Our mouse-adapted virus has a similar antiviral profile to the original isolate as well as another respiratory picornavirus, rhinovirus-14. This model will be valuable in evaluating experimental therapies in the future.

A neonatal mouse model of Enterovirus D68 infection induces both interstitial pneumonia and acute flaccid myelitis

Enterovirus D68 (EV-D68) is a causative agent of recent outbreaks of severe respiratory illness, pneumonia and acute flaccid myelitis (AFM) worldwide. The study of the pathogenesis, vaccines and anti-viral drugs for EV-D68 infection has been reported. Given the previously described mouse model of EV-D68, we sought to establish a neonatal mice model inducing both pneumonia and AFM. The neonatal BALB/c mice were inoculated intraperitoneally with the EV-D68 strain (named15296-virus) which was produced by the reverse genetics method. The infected mice displayed limb paralysis, tachypnea and even death, which were similar to the clinical symptoms of human infections. Moreover, the results of histopathologic examination and immunohistochemical staining showed acidophilic necrosis in the muscle, the spinal cord and alveolar wall thickening in the lung, indicating that EV-D68 exhibited strong tropism to the muscles, spinal cord and lung. Furthermore, the results of real-time PCR also suggested that the viral loads in the blood, spinal cord, muscles and lung were higher than those in other tissues at different time points post-infection. Additionally, the neonatal mouse model was used for evaluating the EV-D68 infection. The results of the anti-serum passive and maternal antibody protection indicated that the neonatal mice could be protected against the EV-D68 challenge, and displayed that both the serum of 15296-virus and prototype-virus (Fermon) were performing a certain cross-protective activity against the 15296-virus challenge. In summary, the above results proved that our neonatal mouse model possessed not only the interstitial pneumonia and AFM simultaneously but also a potentiality to evaluate the protective effects of EV-D68 vaccines and anti-viral drugs in the future.

Enterovirus D68 - The New Polio?

Enterovirus D68 (EV-D68) has emerged over the recent years, with large outbreaks worldwide. Increased occurrence has coincided with improved clinical awareness and surveillance of non-polio enteroviruses. Studies showing its neurotropic nature and the change in pathogenicity have established EV-D68 as a probable cause of Acute Flaccid Myelitis (AFM). The EV-D68 storyline shows many similarities with poliovirus a century ago, stimulating discussion whether EV-D68 could be ascertaining itself as the "new polio." Increasing awareness amongst clinicians, incorporating proper diagnostics and integrating EV-D68 into accessible surveillance systems in a way that promotes data sharing, will be essential to reveal the burden of disease. This will be a necessary step in preventing EV-D68 from becoming a threat to public health.

Evaluation of antiviral therapies in respiratory and neurological disease models of Enterovirus D68 infection in mice

Enterovirus D68 (EV-D68) is unique among enteroviruses because of the ability to cause severe respiratory disease as well as neurological disease. We developed separate models of respiratory and neurological disease following EV-D68 infection in AG129 mice that respond to antiviral treatment with guanidine. In four-week-old mice infected intranasally, EV-D68 replicates to high titers in lung tissue increasing the proinflammatory cytokines MCP-1 and IL-6. The respiratory infection also produces an acute viremia. In 10-day-old mice infected intraperitoneally, EV-D68 causes a neurological disease with weight-loss, paralysis, and mortality. In our respiratory model, treatment with guanidine provides a two-log reduction in lung virus titers, reduces MCP-1 and IL-6, and prevents histological lesions in the lungs. Importantly, viremia is prevented by early treatment with guanidine. In our neurological model, guanidine treatment protects mice from weight-loss, paralysis, and mortality. These results demonstrate the utility of these models for evaluation of antiviral therapies for EV-D68 infection.

Oh, SNAP! How enteroviruses redirect autophagic traffic away from degradation

Picornaviruses, one of the major causes of human diseases ranging from the common cold to acute flaccid paralysis, have a short cytosolic lifecycle that, in cultured cells, ends in cell lysis. For years, the prevailing model was that these viruses exit from cells exclusively through cell lysis. However, over the last several years it has become apparent that for some picornaviruses, a macroautophagy/autophagy-related pathway can result in release of virus particles wrapped in a membrane containing autophagic markers. It has been proposed that this enveloped release predominates within hosts, allowing cell-to-cell movement of virus while minimizing exposure to the immune system. One reason that picornaviruses induce the autophagy pathway is to provide membrane scaffolds for RNA replication complexes. Perhaps more importantly, acidified autophagosomes (known as amphisomes) provide havens for maturation of new viral particles into infectious viruses. In back-to-back papers recently published in Cell Reports, our labs investigated a basic question: if picornavirus particles are maturing inside amphisomes, then how are they avoiding the typical degradative fate of autophagic cargo and exiting the cell intact?

Acute Flaccid Paralysis and Enteroviral Infections

PURPOSE OF REVIEW

The focus of this review is on enterovirus (EV)-associated acute flaccid paralysis (AFP) due to spinal cord anterior horn cell disease. Emphasis is placed on the epidemiology, pathogenesis, diagnosis, treatment, and outcome of AFP caused by polioviruses, vaccine-derived polioviruses, EV-D68, and EV-A71.

RECENT FINDINGS

Since the launch of The Global Polio Eradication Initiative in 1988, the worldwide incidence of polio has been reduced by 99.9%, with small numbers of poliomyelitis cases being reported only in Afghanistan, Pakistan, and Nigeria. With the planned phaseout of oral polio vaccine, vaccine-associated poliomyelitis is also expected to be eliminated. In their place, other EVs, chiefly EV-D68 and EV-A71, have emerged as the principal causes of AFP. There is evidence that the emergence of EV-D68 as a cause of severe respiratory disease and AFP was due to recent genetic virus evolution. Antiviral medications targeting EV-D68, EV-A71, and other EVs will likely be available in the near future. An effective EV-A71 vaccine has been developed, and preliminary investigations suggest an EV-D68 vaccine could be on the horizon. The eradication of poliomyelitis and vaccine-associated poliomyelitis is near, after which other EVs, presently EV-D68 and EV-A71, will be the principle viral causes of AFP. Moving forward, it is essential that EV outbreaks, in particular those associated with neurologic complications, be investigated carefully and the causal strains identified, so that treatment and prevention efforts can be rapidly developed and implemented.

Hopkins syndrome following the first episode of bronchial asthma associated with enterovirus D68: a case report

Background

Hopkins syndrome (HS) is a rare disorder presenting with acute flaccid paralysis of the limbs following an asthma attack. Neurologists encounter a diagnostic challenge if patients without a history of bronchial asthma develop neurologic features mimicking HS following acute respiratory distress. We report a case of HS occurring after a first episode of bronchial asthma associated with enterovirus D68 infection.

Case presentation

A 5-year-old girl developed acute respiratory distress. On the fourth hospital day, both her legs became paralyzed except for slight muscle contraction in the right lower limb. Tendon reflexes in the lower limbs were diminished and there was a positive Babinski sign on the right. Sensation was normal in all modalities, and there was no uro-rectal disturbance. Spinal magnetic resonance imaging identified T2-hyperintense lesions with spinal cord edema, mainly involving the bilateral T11 to L1 anterior horns, with left side dominance extending to the left posterior horn. The neurological and neuro-radiological findings of our case were suggestive of HS; however, she had no history of bronchial asthma. An acetylcholine inhalation challenge eventually proved the presence of reversible airway hyper-responsiveness, allowing us to diagnose HS. We identified enterovirus D68 in the patient’s intratracheal aspirates using a sensitive polymerase chain reaction assay. Intravenous immunoglobulin administrations at 2 g/kg² for 5 consecutive days were repeated every month up to four times. After these treatments, the muscle strength of her right lower limb slightly improved while her left lower leg remained completely paralyzed.

Conclusion

This case emphasizes the importance of provocation tests to reveal the presence of airway hyper-responsiveness when a child shows neurological signs mimicking HS following acute respiratory distress. Furthermore, the present case suggests a possible link between HS and acute flaccid paralysis following lower respiratory tract infection by enterovirus D68.