Enterovirus D-68: an emerging cause of infection

Update on Viral Infections Involving the Central Nervous System in Pediatric Patients

Infections of the central nervous system (CNS) are mainly caused by viruses, and these infections can be life-threatening in pediatric patients. Although the prognosis of CNS infections is often favorable, mortality and long-term sequelae can occur. The aims of this narrative review were to describe the specific microbiological and clinical features of the most frequent pathogens and to provide an update on the diagnostic approaches and treatment strategies for viral CNS infections in children. A literature analysis showed that the most common pathogens worldwide are enteroviruses, arboviruses, parechoviruses, and herpesviruses, with variable prevalence rates in different countries. Lumbar puncture (LP) should be performed as soon as possible when CNS infection is suspected, and cerebrospinal fluid (CSF) samples should always be sent for polymerase chain reaction (PCR) analysis. Due to the lack of specific therapies, the management of viral CNS infections is mainly based on supportive care, and empiric treatment against herpes simplex virus (HSV) infection should be started as soon as possible. Some researchers have questioned the role of acyclovir as an empiric antiviral in older children due to the low incidence of HSV infection in this population and observed that HSV encephalitis may be clinically recognizable beyond neonatal age. However, the real benefit-risk ratio of selective approaches is unclear, and further studies are needed to define appropriate indications for empiric acyclovir. Research is needed to find specific therapies for emerging pathogens. Moreover, the appropriate timing of monitoring neurological development, performing neuroimaging evaluations and investigating the effectiveness of rehabilitation during follow-up should be evaluated with long-term studies.

Seroepidemiological and phylogenetic characterization of neurotropic enteroviruses in Ireland, 2005-2014

Enteroviruses (EVs) are associated with a broad spectrum of clinical presentation, including aseptic meningitis (AM), encephalitis, hand, foot and mouth disease, acute flaccid paralysis, and acute flaccid myelitis. Epidemics occur sporadically and are associated with increased cases of AM in children. The present study describes the seroepidemiological analysis of circulating EVs in Ireland from 2005 to 2014 and phylogenetic characterization of echovirus 30 (E-30), enterovirus A71 (EV-A71), and enterovirus D68 (EV-D68). EV VP1 genotyping was applied to viral isolates and clinical samples, including cerebrospinal fluid (CSF), and those isolates that remained untypeable by neutralising anti-sera. An increase in AM cases from 2010 to 2014 was associated with an E-30 genogroup variant VII and sequences clustered phylogenetically with those detected in AM outbreaks in France and Italy. EV-D68 viral RNA was not detected in CSF samples and no neurological involvement was reported. Three EV-A71 positive CSF samples were identified in patients presenting with AM. A phylogenetic analysis of respiratory-associated EV-D68 and EV-A71 cases in circulation was performed to determine baseline epidemiological data. EV-D68 segregated with clades B and B(1) and EV-A71 clustered as subgenogroup C2. The EV VP1 genotyping method was more sensitive than neutralising anti-sera methods by virus culture and importantly demonstrated concordance between EV genotypes in faecal and CSF samples which should facilitate EV screening by less invasive sampling approaches in AM presentations.

CRISPR/Cas9-mediated gene knockout screens and target identification via whole-genome sequencing uncover host genes required for picornavirus infection

Several groups have used genome-wide libraries of lentiviruses encoding small guide RNAs (sgRNAs) for genetic screens. In most cases, sgRNA expression cassettes are integrated into cells by using lentiviruses, and target genes are statistically estimated by the readout of sgRNA sequences after targeted sequencing. We present a new virus-free method for human gene knockout screens using a genome-wide library of CRISPR/Cas9 sgRNAs based on plasmids and target gene identification via whole-genome sequencing (WGS) confirmation of authentic mutations rather than statistical estimation through targeted amplicon sequencing. We used 30,840 pairs of individually synthesized oligonucleotides to construct the genome-scale sgRNA library, collectively targeting 10,280 human genes (i.e. three sgRNAs per gene). These plasmid libraries were co-transfected with a Cas9-expression plasmid into human cells, which were then treated with cytotoxic drugs or viruses. Only cells lacking key factors essential for cytotoxic drug metabolism or viral infection were able to survive. Genomic DNA isolated from cells that survived these challenges was subjected to WGS to directly identify CRISPR/Cas9-mediated causal mutations essential for cell survival. With this approach, we were able to identify known and novel genes essential for viral infection in human cells. We propose that genome-wide sgRNA screens based on plasmids coupled with WGS are powerful tools for forward genetics studies and drug target discovery.

Enterovirus D68-Associated Community-Acquired Pneumonia in the Pediatric Age Group

PURPOSE OF REVIEW

This review summarizes the current knowledge regarding the role of Enterovirus D68 (EV-D68) in community-acquired pneumonia (CAP) in children.

RECENT FINDINGS

EV-D68 is an emergent viral pathogen. Since its first isolation in 1962 in California in four children suffering from CAP and bronchiolitis, EV-D68 has been rarely detected from respiratory specimens. However, recently, EV-D68 infection has raised concerns in the international community because of outbreaks in 2014 in the USA and the increased number of children with EV-D68-associated severe respiratory illnesses, including pneumonia, that have been reported in many other countries around the world. EV-D68 causes severe and life-threatening respiratory diseases in the pediatric population, particularly in children with underlying conditions such as prematurity or chronic diseases. Since no specific treatment or vaccinations are available for EV-D68 infections, greater surveillance as well as the use of sensitive and rapid diagnostic methods are essential to prevent and manage new outbreaks.

Acute flaccid myelitis associated with enterovirus-D68 infection in an otherwise healthy child

Background

Reporting new cases of enterovirus (EV)-D68-associated acute flaccid myelitis (AFM) is essential to understand how the virus causes neurological damage and to characterize EV-D68 strains associated with AFM.

Case presentation

A previously healthy 4-year-old boy presented with sudden weakness and limited mobility in his left arm. Two days earlier, he had an upper respiratory illness with mild fever. At admission, his physical examination showed that the child was febrile (38.5 °C) and alert but had a stiff neck and weakness in his left arm, which was hypotonic and areflexic. Cerebrospinal fluid (CSF) examination showed a mild increase in white blood cell count (80/mm³, 41% neutrophils) and a slightly elevated protein concentration (76 gm/dL). Bacterial culture and molecular biology tests for detecting viral infection in CSF were negative. The patient was then treated with intravenous ceftriaxone and acyclovir. Despite therapy, within 24 h, the muscle weakness extended to all four limbs, which exhibited greatly reduced mobility. Due to his worsening clinical prognosis, the child was transferred to our Pediatric Intensive Care Unit; at admission he was diagnosed with acute flaccid paralysis of all four limbs. Brain magnetic resonance imaging (MRI) was negative, except for a focal signal alteration in the dorsal portion of the medulla oblongata, also involving the pontine tegmentum, whereas spine MRI showed an extensive signal alteration of the cervical and dorsal spinal cord reported as myelitis. Signal alteration was mainly localized in the central grey matter, most likely in the anterior horns. Molecular biology tests performed on nasopharyngeal aspirate and on bronchoalveolar lavage fluid were negative for bacteria but positive for EV-D68 clade B3. Plasmapheresis was performed and corticosteroids and intravenous immunoglobulins were administered. After 4 weeks of treatment, the signs and symptoms of AFM were significantly reduced, although some weakness and tingling remained in the patient’s four limbs. MRI acquired after 3 weeks showed that the previously reported alterations were no longer present.

Conclusion

This case suggests that EV-D68 is a neurotropic agent that can cause AFM and strains are circulating in Europe. EV-D68 disease surveillance is required to better understand EV-D68 pathology and to compare various strains that cause AFM.

Identification and Whole-Genome Sequencing of Four Enterovirus D68 Strains in Southern China in Late 2015

Four enterovirus D68 (EV-D68) strains from four children with influenza-like illness were identified in Shenzhen, southern China, in late 2015. Here, we announce the availability of these viral genomes in GenBank. The genomic sequences of these EV-D68 strains showed the closest phylogenetic relationship to strains from northern China.

Enterovirus D68 Infection

First described in 1962 in children hospitalized for pneumonia and bronchiolitis, the Enterovirus D68 (EV-D68) is an emergent viral pathogen. Since its discovery, during the long period of surveillance up to 2005, EV-D68 was reported only as a cause of sporadic outbreaks. In recent years, many reports from different countries have described an increasing number of patients with respiratory diseases due to EV-D68 associated with relevant clinical severity. In particular, an unexpectedly high number of children have been hospitalized for severe respiratory disease due to EV-D68, requiring intensive care such as intubation and mechanical ventilation. Moreover, EV-D68 has been associated with acute flaccid paralysis and cranial nerve dysfunction in children, which has caused concerns in the community. As no specific antiviral therapy is available, treatment is mainly supportive. Moreover, because no vaccines are available, conventional infection control measures (i.e., standard, for contacts and droplets) in both community and healthcare settings are recommended. However, further studies are required to fully understand the real importance of this virus. Prompt diagnosis and continued surveillance of EV-D68 infections are essential to managing and preventing new outbreaks. Moreover, if the association between EV-D68 and severe diseases will be confirmed, the development of adequate preventive and therapeutic approaches are a priority.