Human Parechovirus 3 Meningitis and Fatal Leukoencephalopathy

Parechovirus: neglected for too long?

Parechoviruses are non-enveloped, positive-sense, single-stranded RNA viruses that have been isolated from multiple vertebrate species. Infection with these etiologic agents of typically mild childhood respiratory and gastrointestinal illness in humans is nearly universal, and a subset of infected neonates and infants develop severe neurologic diseases. Rodent parechoviruses cause myocarditis, encephalitis, and perinatal death in multiple rodent species. The key steps of the viral life cycle, clinical characteristics, and global burden of these viruses are not well characterized yet, particularly for nonhuman parechoviruses. Here, we review the history of human and nonhuman parechovirus isolation, global seroprevalence and distribution, viral biology, and evolution, considering these factors might contribute to host specificity, virulence, tissue tropism, pathogenesis, host immunity, and population dynamics.

Clinical Spectrum and Epidemiology of Human Parechovirus Infections in Infants: A Retrospective Study in the Western Part of Sweden

Background

Human parechovirus (HPeV) infections can cause sepsis and meningoencephalitis in infants. To improve our knowledge of the consequences of HPeV infections in young children, the incidence, clinical spectrum, and short-term outcome among infants infected with HPeV were investigated retrospectively.

Methods

The presence of HPeV RNA was investigated by polymerase chain reaction in cerebrospinal fluid from 327 children aged 0 to 12 months sampled between 2014 and 2017. Eighty-one were infected with HPeV and included in the study. These infants were divided into 3 groups based on clinical assessment: HPeV was the presumed cause of disease (n = 35); HPeV could have contributed to or been considered the cause of disease (n = 24); and HPeV was not considered the cause of disease (n = 22).

Results

Infection with HPeV type 3 was common in all groups (n = 54), and most children were younger than 3 months (n = 63). The children in the first group (HPeV as presumed cause) had meningoencephalitis (n = 20), viral sepsis (n = 9), or non-severe viral infection (n = 6). The youngest were more prone to develop meningoencephalitis, while the slightly older children had symptoms of viral sepsis or nonsevere viral infection (P < .05). Eleven had symptom onset within 2 days after birth. Two infants diagnosed with sudden infant death syndrome were HPeV infected when tested postmortem.

Conclusions

HPeV infections were identified in 25% of children with suspected central nervous system infection. The clinical presentation of those infected with HPeV varied with age. HPeV infections may be associated with sudden infant death syndrome, although this is not well studied. The results suggest that HPeV infections may be underdiagnosed in young infants.

Multiomic Analysis of Neuroinflammation and Occult Infection in Sudden Infant Death Syndrome

Importance

Antemortem infection is a risk factor for sudden infant death syndrome (SIDS)-the leading postneonatal cause of infant mortality in the developed world. Manifestations of infection and inflammation are not always apparent in clinical settings or by standard autopsy; thus, enhanced resolution approaches are needed.

Objective

To ascertain whether a subset of SIDS cases is associated with neuroinflammation and occult infection.

Design, Setting, and Participants

In this case-control study, postmortem fluids from SIDS cases and controls collected between July 2011 and November 2018 were screened for elevated inflammatory markers, specifically cerebrospinal fluid (CSF) neopterin and CSF and serum cytokines. CSF, liver, and brain tissue from SIDS cases with elevated CSF neopterin were subjected to metagenomic next-generation sequencing (mNGS) to probe for infectious pathogens. Brainstem tissue from a subset of these cases was analyzed by single-nucleus RNA sequencing (snRNAseq) to measure cell type-specific gene expression associated with neuroinflammation and infection. All tissue and fluid analyses were performed from April 2019 to January 2023 in a pathology research laboratory. Included was autopsy material from infants dying of SIDS and age-matched controls dying of known causes.

Exposures

There were no interventions or exposures.

Main Outcomes and Measures

CSF neopterin levels were measured by high-performance liquid chromatography. Cytokines were measured by multiplex fluorometric assay. mNGS was performed on liver, CSF, brain, and brainstem tissue. snRNAseq was performed on brainstem tissue.

Results

A cohort of 71 SIDS cases (mean [SD] age, 55.2 [11.4] postconceptional weeks; 42 male [59.2%]) and 20 controls (mean [SD] age, 63.2 [16.9] postconceptional weeks; 11 male [55.0%]) had CSF and/or serum available. CSF neopterin was screened in 64 SIDS cases and 15 controls, with no exclusions. Tissues from 6 SIDS cases were further analyzed. For CSF neopterin measures, SIDS samples were from infants with mean (SD) age of 54.5 (11.3) postconceptional weeks (38 male [59.4%]) and control samples were from infants with mean (SD) age of 61.5 (17.4) postconceptional weeks (7 male [46.7%]). A total of 6 SIDS cases (9.3%) with high CSF neopterin were identified, suggestive of neuroinflammation. mNGS detected human parechovirus 3 (HPeV3) in tissue and CSF from 1 of these 6 cases. snRNAseq of HPeV3-positive brainstem tissue (medulla) revealed dramatic enrichment of transcripts for genes with predominately inflammatory functions compared with 3 age-matched SIDS cases with normal CSF neopterin levels.

Conclusions and Relevance

Next-generation molecular tools in autopsy tissue provide novel insight into pathogens that go unrecognized by normal autopsy methodology, including in infants dying suddenly and unexpectedly.

Infection and inflammation: radiological insights into patterns of pediatric immune-mediated CNS injury

The central nervous system (CNS) undergoes constant immune surveillance enabled via regionally specialized mechanisms. These include selectively permissive barriers and modifications to interlinked innate and adaptive immune systems that detect and remove an inciting trigger. The end-points of brain injury and edema from these triggers are varied but often follow recognizable patterns due to shared underlying immune drivers. Imaging provides insights to understanding these patterns that often arise from unique interplays of infection, inflammation and genetics. We review the current updates in our understanding of these intersections and through examples of cases from our practice, highlight that infection and inflammation follow diverse yet convergent mechanisms that can challenge the CNS in children.

Molecular Mechanisms in the Genesis of Seizures and Epilepsy Associated With Viral Infection

Seizures are a common presenting symptom during viral infections of the central nervous system (CNS) and can occur during the initial phase of infection ("early" or acute symptomatic seizures), after recovery ("late" or spontaneous seizures, indicating the development of acquired epilepsy), or both. The development of acute and delayed seizures may have shared as well as unique pathogenic mechanisms and prognostic implications. Based on an extensive review of the literature, we present an overview of viruses that are associated with early and late seizures in humans. We then describe potential pathophysiologic mechanisms underlying ictogenesis and epileptogenesis, including routes of neuroinvasion, viral control and clearance, systemic inflammation, alterations of the blood-brain barrier, neuroinflammation, and inflammation-induced molecular reorganization of synapses and neural circuits. We provide clinical and animal model findings to highlight commonalities and differences in these processes across various neurotropic or neuropathogenic viruses, including herpesviruses, SARS-CoV-2, flaviviruses, and picornaviruses. In addition, we extensively review the literature regarding Theiler's murine encephalomyelitis virus (TMEV). This picornavirus, although not pathogenic for humans, is possibly the best-characterized model for understanding the molecular mechanisms that drive seizures, epilepsy, and hippocampal damage during viral infection. An enhanced understanding of these mechanisms derived from the TMEV model may lead to novel therapeutic interventions that interfere with ictogenesis and epileptogenesis, even within non-infectious contexts.

Characterization of Pathogenesis and Inflammatory Responses to Experimental Parechovirus Encephalitis

Human parechovirus type 3 (PeV-A3) infection has been recognized as an emerging etiologic factor causing severe nerve disease or sepsis in infants and young children. But the neuropathogenic mechanisms of PeV-A3 remain unknown. To understand the pathogenesis of PeV-A3 infection in the neuronal system, PeV-A3-mediated cytopathic effects were analyzed in human glioblastoma cells and neuroblastoma cells. PeV-A3 induced interferons and inflammatory cytokine expression in these neuronal cells. The pronounced cytopathic effects accompanied with activation of death signaling pathways of apoptosis, autophagy, and pyroptosis were detected. A new experimental disease model of parechovirus encephalitis was established. In the disease model, intracranial inoculation with PeV-A3 in C57BL/6 neonatal mice showed body weight loss, hindlimb paralysis, and approximately 20% mortality. PeV-A3 infection in the hippocampus and cortex regions of the neonatal mouse brain was revealed. Mechanistic assay supported the in vitro results, indicating detection of PeV-A3 replication, inflammatory cytokine expression, and death signaling transduction in mouse brain tissues. These in vitro and in vivo studies revealed that the activation of death signaling and inflammation responses is involved in PeV-A3-mediated neurological disorders. The present results might account for some of the PeV-A3-associated clinical manifestations.

Parent-administered Neurodevelopmental Follow up in Children After Picornavirus CNS Infections

BACKGROUND

Data on the neurodevelopment of children who experienced central nervous system (CNS) infections with enteroviruses (EV) or parechoviruses (hPeV) is scarce and mostly limited to follow up of short-term outcomes.

METHODS

Parents of children who presented between 2014 and 2019, underwent a lumbar puncture and whose cerebrospinal fluid was polymerase chain reaction positive for EV or hPeV, were asked to complete a care-giver-administered neurodevelopmental assessment tool (The Ages and Stages Instrument [ASQ3]). Clinical data of the infective episode were collected from patient notes.

RESULTS

Of 101 children, 43 (10 hPeV+, 33 EV+) submitted ASQ3 results. Median age at assessment was 38.9 months (interquartile range, 15.4-54.8), the follow-up interval 3 years (median 37 months; interquartile range, 13.9-53.1). Age, inflammatory markers, and cerebrospinal fluid pleocytosis during the infective event were not associated with ASQ3 scores. In 23 children (17 EV+, 6 hPeV+), no neurodevelopmental concerns were reported. Two more had preexisting developmental delay and were excluded. Of the remaining, 18/41 (43.9%) reported ASQ3 scores indicating need for monitoring or professional review in at least 1 category, not differing by pathogen (EV 14/31, 45.2%; hPeV 4/10, 40%; P = 0.71). Seven children will require formal review, scoring ≥2 SD below the mean in at least 1 category (6/31 EV+, 1/10 hPeV+, P = 0.7), 3 scored ≥2 SD below the mean in more than 1 area.

CONCLUSIONS

Parent-administered developmental assessment of children with a history of early picornavirus infection of the CNS identified a subgroup that requires formal neurodevelopmental review. Wider application of community-based developmental screening will complement our understanding of the impact of CNS infections in early childhood.

Enterovirus Encephalitis in Newborns: Not-Periventricular Brain Involvement and Vascular Pathogenesis in a Novel Case

Neonatal encephalitis by either enteroviruses (EVs) or parechoviruses (PeVs) is often complicated by hemispheric periventricular white matter lesions. Although showing many similarities, the two types of encephalitis differ in some clinical and laboratory aspects, mostly because PeV encephalitis does not show any change of protein and white cell content in the cerebrospinal fluid, and clinically, the onset of PeV encephalitis is often marked by early seizures accompanying a fever of sepsis-like disease. Instead, no difference exists relative to the white matter lesions, which are constantly described as periventricular, even in rare detailed neuropathological studies. Herein, taking a cue from a neonate with EV encephalitis who showed occipital white matter lesions involving the overlying cortex, but completely sparing the periventricular area, we demonstrate that the brain lesions in EV encephalitis in newborns can be more extended than known. To our knowledge, the not-periventricular involvement of the white matter with EV encephalitis has never been described so far, as well as the potential of EV to injure the cortex. We confirm the pathogenetic role of a vascular mechanism for the tissue injury, but other proposed mechanisms are also discussed. It is noteworthy that the neurological outcome of this newborn remained favorable, and no epileptic seizures occurred in the first few days nor afterward.

Multicystic Encephalomalacia: The Neuropathology of Systemic Neonatal Parechovirus Infection

The Neuropathology of Human Parechovirus (HPeV) is not widely described due to the relatively recent discovery of the virus combined with a limited number of autopsy case reports. We report the case of an infant boy born at 38 weeks who, six days after birth, presented with fever and severe neurological dysfunction. Human Parechovirus Type 3 (HPeV3) RNA was detected in his cerebrospinal fluid (CSF) and blood. He died five days after his initial presentation. Neuropathologic examination demonstrated multicystic encephalomalacia (ME). This case report confirms that white matter pathology is dominant in HPeV3 infection. A unique feature, of HPeV encephalomalacia is absence of CSF pleocytosis and minimal inflammation in the meninges. The findings permit comment on the pathogenesis of brain injury by this virus.

HPeV3-associated acute encephalitis/encephalopathy among Japanese infants

OBJECTIVE

The current study aimed to identify and compare the clinical characteristics of human parechovirus type 3 (HPeV3)-associated acute encephalitis/encephalopathy (HPeV3E/E) between infants with abnormal brain magnetic resonance imaging (MRI) findings (typical, or MRI-positive HPeV3E/E) and those with MRI-negative findings (MRI-negative HPeV3E/E).

METHODS

This is a retrospective study on patients with HPeV3 infection, and a two-step questionnaire survey performed on 837 hospitals in Japan between 2014 and 2016.

RESULTS

We identified 240 infants with HPeV3 infection, of which 34 had been clinically-diagnosed HPeV3E/E (cHPeV3E/E). However, detailed clinical data were provided by 32 of the 34 patients. Among these 32, 23 had undergone MRI and were categorized into two groups, MRI-positive (n = 17) and -negative (n = 6). There were no significant intergroup differences in clinical lab results or symptoms, except for gastrointestinal symptoms that were only present in the MRI-negative patients. The MRI-positive group showed white matter involvement on brain MRI during the acute phase, and 8 patients presented with lesions on follow-up MRI. Furthermore, 4 (50%) of the 8 patients had neurological sequelae.

CONCLUSION

Clinical characteristics of cHPeV3E/E patients with and without lesions on brain MRI showed no significant differences. Therefore, considering the difficulty in distinguishing febrile infants with cHPeV3E/E from those with a sepsis-like illness, during an HPeV3 infection epidemic, it is imperative to frequently perform brain MRI in febrile infants presenting with severe disease for the early diagnosis of HPeV3E/E presenting with brain lesions.

Innate Immune Responses in Serum and Cerebrospinal Fluid From Neonates and Infants Infected With Parechovirus-A3 or Enteroviruses

BACKGROUND

Parechovirus (PeV)-A3 and enteroviruses (EV) are the most common viruses causing sepsis and meningoencephalitis in neonates and young infants. Clinical manifestations of PeV-A3 infection are more severe than those of EV infection, and no pleocytosis with a positive polymerase chain reaction (PCR) result for PeV-A3 in cerebrospinal fluid (CSF) are characteristic findings. We hypothesized that innate immune responses to PeV-A3 and EV are distinct in serum and CSF.

METHODS

We evaluated 22 cytokines/chemokines in serum and CSF from PeV-A3- or EV-infected patients younger than 4 months in Niigata, Japan, from 2015 through 2018. Infection was diagnosed with real-time PCR followed by sequencing. Febrile neonates and infants with sepsis-like syndrome who had negative bacterial culture and viral PCR for both PeV-A and EV were also included (non-PeV-A/EV patients).

RESULTS

Among 192 febrile patients, we evaluated 16 PeV-A3-infected, 15 EV-infected, and 8 non-PeV-A/EV patients. Serum pro-/anti-inflammatory cytokine/chemokine levels were higher in PeV-A3-infected patients than in EV-infected patients (P < .02). Although most cytokine/chemokine were elevated in CSF from EV-infected patients, levels were low or undetectable in PeV-A3-infected and non-PeV-A/EV patients (P < .001).

CONCLUSIONS

Distinct cytokine/chemokine patterns in serum and CSF may explain the different clinical manifestations of PeV-A3-infected and EV-infected neonates and young infants.

Non-congenital viral infections of the central nervous system: from the immunocompetent to the immunocompromised child

Non-congenital viral infections of the central nervous system in children can represent a severe clinical condition that needs a prompt diagnosis and management. However, the aetiological diagnosis can be challenging because symptoms are often nonspecific and cerebrospinal fluid analysis is not always diagnostic. In this context, neuroimaging represents a helpful tool, even though radiologic patterns sometimes overlap. The purpose of this pictorial essay is to suggest a schematic representation of different radiologic patterns of non-congenital viral encephalomyelitis based on the predominant viral tropism and vulnerability of specific regions: cortical grey matter, deep grey matter, white matter, brainstem, cerebellum and spine.

Emergent Viral Infections of the CNS

Biological evolution of the microbiome continually drives the emergence of human viral pathogens, a subset of which attack the nervous system. The sheer number of pathogens that have appeared, along with their abundance in the environment, demand our attention. For the most part, our innate and adaptive immune systems have successfully protected us from infection; however, in the past 5 decades, through pathogen mutation and ecosystem disruption, a dozen viruses emerged to cause significant neurologic disease. Most of these pathogens have come from sylvatic reservoirs having made the energetically difficult, and fortuitously rare, jump into humans. But the human microbiome is also replete with agents already adapted to the host that need only minor mutations to create neurotropic/toxic agents. While each host/virus symbiosis is unique, this review examines virologic and immunologic principles that govern the pathogenesis of different viral CNS infections that were described in the past 50 years (Influenza, West Nile Virus, Zika, Rift Valley Fever Virus, Hendra/Nipah, Enterovirus-A71/-D68, Human parechovirus, HIV, and SARS-CoV). Knowledge of these pathogens provides us the opportunity to respond and mitigate infection while at the same time prepare for inevitable arrival of unknown agents.

Neuropathology in Neonatal Mice After Experimental Coxsackievirus B2 Infection Using a Prototype Strain, Ohio-1

Coxsackievirus B (CVB) causes severe morbidity and mortality in neonates and is sometimes associated with severe brain damage resulting from acute severe viral encephalomyelitis. However, the neuropathology of CVB infection remains unclear. A prototype strain of coxsackievirus B2 (Ohio-1) induces brain lesions in neonatal mice, resulting in dome-shaped heads, ventriculomegaly, and loss of the cerebral cortex. Here, we characterized the glial pathology in this mouse model. Magnetic resonance imaging revealed an absence of the cerebral cortex within 2 weeks after inoculation. Histopathology showed that virus replication triggered activation of microglia and astrocytes, and induced apoptosis in the cortex, with severe necrosis and lateral ventricular dilation. In contrast, the brainstem and cerebellum remained morphologically intact. Immunohistochemistry revealed high expression of the coxsackievirus and adenovirus receptor (a primary receptor for CVB) in mature neurons of the cortex, hippocampus, thalamus, and midbrain, demonstrating CVB2 infection of mature neurons in these areas. However, apoptosis and neuroinflammation from activated microglia and astrocytes differed in thalamic and cortical areas. Viral antigens were retained in the brains of animals in the convalescence phase with seroconversion. This animal model will contribute to a better understanding of the neuropathology of CVB infection.

Neurological and neurodevelopmental outcomes after human parechovirus CNS infection in neonates and young children: a systematic review and meta-analysis

BACKGROUND

Human parechoviruses are a major cause of CNS infection in neonates and young children. They have been implicated in neurological sequelae and neurodevelopmental delay. However, the magnitude of this effect has not been systematically reviewed or assessed with meta-analyses. We investigated short-term, medium-term, and long-term neurological sequelae and neurodevelopmental delay in neonates and young children after parechovirus-CNS-infection.

METHODS

In this systematic review and meta-analyses of studies, we searched PubMed, Embase, and PsycInfo, from the inception of the database until March 18, 2019, for reviews, systematic reviews, cohort studies, case series, and case control studies reporting on neurological or neurodevelopmental outcomes of children 3 months or younger with parechovirus infection of the CNS. Studies that were published after Dec 31, 2007, assessed children younger than 16 years, detailed parechoviruses infection of the CNS (confirmed by PCR), and followed up on neurological and neurodevelopmental outcomes were included. Studies published before Dec 31, 2007, were excluded. The predefined primary outcomes were the proportions of children with neurological sequelae, impairment in auditory or visual functions, or gross motor function delay. The proportion of children in whom neurological or neurodevelopmental outcomes were reported was pooled in meta-analyses. For each outcome variable we calculated the pooled proportion with 95% CI. The proportion of children in whom neurological or neurodevelopmental outcomes were reported was extracted by one author and checked by another. Two authors independently assessed the methodological quality of the studies.

FINDINGS

20 studies were eligible for quantitative synthesis. The meta-analyses showed an increasing proportion of children with neurological sequelae over time: 5% during short-term follow-up (pooled proportion 0·05 [95% CI 0·03-0·08], I²=0·00%; p=0·83) increasing to 27% during long-term follow-up (0·27 [0·17-0·40], I²=52·74%; p=0·026). The proportion of children with suspected neurodevelopmental delay was 9% or more during long-term follow-up. High heterogeneity and methodological issues in the included studies mean that the results should be interpreted with caution.

INTERPRETATION

This systematic review suggests the importance of long follow-up, preferably up to preschool or school age (5-6 years), of children with parechovirus infection of the CNS. Although not clinically severe, we found an increasing proportion of neonates and young children with CNS infection had associated neurological sequelae and neurodevelopmental delay over time. We recommend the use of standardised methods to assess neurological and neurodevelopmental functions of these children and to compare results with age-matched reference groups.

FUNDING

No funding was received for this study.

Association Between Neutralizing Antibody Titers against Parechovirus A3 in Maternal and Cord Blood Pairs and Perinatal Factors

BACKGROUND

Parechovirus A3 (PeV-A3) is a pathogen that causes severe infectious diseases such as sepsis and meningoencephalitis in neonates and young infants. In this study, we aimed to measure the neutralizing antibody titer (NAT) against PeV-A3 in paired maternal and cord blood samples and to clarify the serum epidemiology of PeV-A3 and the association between the NAT and perinatal factors.

METHODS

NATs against PeV-A3 were measured in 1033 mothers (maternal and cord blood pairs; total of 2066 samples) who delivered their infant in Fukushima Prefecture between December 2013 and June 2014. RD-18S cells were used to measure NATs against PeV-A3. The association between NATs against PeV-A3 in maternal and cord blood and perinatal factors was determined using multivariate logistic regression analysis.

RESULTS

The median gestational age of the infants was 39 weeks 4 days (interquartile range, 38 weeks 4 days to 40 weeks 3 days). The NATs against PeV-A3 in maternal blood and in cord blood were almost the same. The proportion of samples assigned to the low-titer group (NAT ≤ 1:16) was approximately 70%, and the proportion of samples assigned to the high-titer group tended to increase with gestational age. The high-titer rate and geometric mean titers decreased with increased maternal age.

CONCLUSIONS

Cord blood indicates that neonates born at a lower gestational age and older mothers have a low NAT against PeV-A3. Thus, more attention should be paid to the onset of severe PeV-A3 disease in such neonates and young infants.

dotdotdot: an automated approach to quantify multiplex single molecule fluorescent in situ hybridization (smFISH) images in complex tissues

Multiplex single-molecule fluorescent in situ hybridization (smFISH) is a powerful method for validating RNA sequencing and emerging spatial transcriptomic data, but quantification remains a computational challenge. We present a framework for generating and analyzing smFISH data in complex tissues while overcoming autofluorescence and increasing multiplexing capacity. We developed dotdotdot (https://github.com/LieberInstitute/dotdotdot) as a corresponding software package to quantify RNA transcripts in single nuclei and perform differential expression analysis. We first demonstrate robustness of our platform in single mouse neurons by quantifying differential expression of activity-regulated genes. We then quantify spatial gene expression in human dorsolateral prefrontal cortex (DLPFC) using spectral imaging and dotdotdot to mask lipofuscin autofluorescence. We lastly apply machine learning to predict cell types and perform downstream cell type-specific expression analysis. In summary, we provide experimental workflows, imaging acquisition and analytic strategies for quantification and biological interpretation of smFISH data in complex tissues.

Early Life Parechovirus Infection Neurodevelopmental Outcomes at 3 Years: A Cohort Study

OBJECTIVE

To investigate the long-term developmental and behavioral outcomes in an established cohort of children hospitalized as infants with human parechovirus (HPeV) infection and sepsis-like illness.

STUDY DESIGN

The HPeV cohort was composed of children 3 years of age after HPeV infection and hospitalization in early infancy that occurred during a well-documented HPeV genotype 3 outbreak in Australia. We assessed neurodevelopmental and behavioral outcomes using the Bayley Scales of Infant and Toddler Development-III and the Child Behavior Checklist. We compared their outcomes with a subsample of healthy control infants drawn from the independently sampled Triple B Pregnancy Cohort Study.

RESULTS

Fifty children, with a mean age of 41 months, were followed for 3 years after hospital admission with HPeV infection. There were 47 children whose original illness was fever without source or sepsis-like illness and 3 who had encephalitis. All children in the HPeV cohort showed age-specific development within the population normal range on the Bayley Scales of Infant and Toddler Development-III. There was no difference in developmental attainment compared with 107 healthy control infants after adjusting for measured confounders. The HPeV cohort showed higher average scores on the Child Behavior Checklist and a higher frequency of clinical range scores compared with healthy controls.

CONCLUSIONS

Although HPeV sepsis-like illness did not result in neurodevelopmental delay at 3 years of age, it was associated with increased behavioral problems compared with healthy controls. The behavioral problems reached a clinical threshold in a minority of children. Results inform clinical management and planning for children after severe HPeV infection in infancy.

Antifungal Triazole Posaconazole Targets an Early Stage of the Parechovirus A3 Life Cycle

Viruses in species Parechovirus A (Picornaviridae) are associated with a wide variety of clinical manifestations. Parechovirus A3 (PeV-A3) is known to cause sepsis-like illness, meningitis, and encephalitis in infants and young children. To date, no specific therapies are available to treat PeV-A3-infected children. We had previously identified two FDA-cleared antifungal drugs, itraconazole (ITC) and posaconazole (POS), with potent and specific antiviral activity against PeV-A3. Time-of-addition and synchronized infection assays revealed that POS targets an early stage of the PeV-A3 life cycle. POS exerts an antiviral effect, evidenced by a reduction in viral titer following the addition of POS to Vero-P cells before infection, coaddition of POS and PeV-A3 to Vero-P cells, incubation of POS and PeV-A3 prior to Vero-P infection, and at attachment. POS exerts less of an effect on virus entry. A PeV-A3 enzyme-linked immunosorbent assay inhibition experiment, using an anti-PeV-A3 monoclonal antibody, suggested that POS binds directly to the PeV-A3 capsid. POS-resistant PeV-A3 strains developed by serial passage in the presence of POS acquired substitutions in multiple regions of the genome, including the capsid. Reverse genetics confirmed substitutions in capsid proteins VP0, VP3, and VP1 and nonstructural proteins 2A and 3A. Single mutants VP0_K66R, VP0_A124T, VP3_N88S, VP1_Y224C, 2A_S78L, and 3A_T1I were 4-, 9-, 12-, 34-, 51-, and 119-fold more resistant to POS, respectively, than the susceptible prototype strain. Our studies demonstrate that POS may be a valuable tool in developing an antiviral therapy for PeV-A3.

Novel scoring system for differentiating parechovirus-A3 and enterovirus infection in neonates and young infants

BACKGROUND

Parechovirus-A3 (PeV-A3) and the enteroviruses (EVs) are the most common viral pathogens responsible for sepsis and meningoencephalitis in neonates and young infants; however, differences in the clinical presentations of two infections are not well described.

OBJECTIVES

To describe the clinical presentations of PeV-A3- and EVs-related diseases and develop a novel scoring system to differentiate two diseases.

STUDY DESIGN

This prospective study used real-time PCR and genetic sequencing to evaluate viral etiologies of febrile neonates and infants <4 months with suspected sepsis or meningoencephalitis in Niigata area, Japan, in 2014-2016. The clinical manifestations of PeV-A3- and EVs-infected patients were compared, and a novel scoring system was developed after identifying the most distinguishable clinical findings, followed by the external cohort validation.

RESULTS

In 210 patients evaluated, we identified 56 PeV-A3-infected (27%) and 43 EVs-infected (20%) patients. The following clinical manifestations were significant in PeV-A3-infected patients, as compared with EVs-infected patients; a higher body temperature (38.9°C vs. 38.5°C, P < .01) and heart rate (181/min vs. 168/min, P = .01), cold extremities (72% vs. 34%, P < .01) and skin mottling (65% vs. 23%, P < .01), lower white blood cell count (5,200/μL vs. 8,900/μL, P < .01) and incidence of cerebrospinal fluid (CSF) pleocytosis (2% vs. 63%, P < .01). Using some of these significant findings, the scoring system successfully distinguished the diseases (accuracy: 86% and 83% for the derivative and external validation cohorts, respectively).

CONCLUSIONS

We found significant clinical manifestations in PeV-A3-infected patients compared to EVs-infected patients. The scoring system may be helpful to distinguish two infections, especially at onset of outbreak.

Human Parechovirus Meningoencephalitis: Neuroimaging in the Era of Polymerase Chain Reaction-Based Testing

Human parechovirus infection is an increasingly recognized cause of neonatal meningoencephalitis. We describe characteristic clinical features and brain MR imaging abnormalities of human parechovirus meningoencephalitis in 6 infants. When corroborated by increasingly available polymerase chain reaction-based testing of the CSF, the distinctive MR imaging appearance may yield a specific diagnosis that obviates costly and time-consuming further clinical evaluation. In our study, infants with human parechovirus presented in the first 35 days of life with seizures, irritability, and sepsis. MR imaging consistently demonstrated low diffusivity within the thalami, corpus callosum, and subcortical white matter with a frontoparietal predominance. T1 and T2 shortening connoting white matter injury along the deep medullary veins suggests venous ischemia as an alternative potential pathogenetic mechanism to direct neuroaxonal injury.

Neurodevelopment medium-term outcome after parechovirus infection

AIM

Human parechoviruses (HPeV) are responsible for fever without a source (FWS), sepsis-like illness and encephalitis in neonates and children under 3 months of age. Short-term outcome is generally good, but there is great concern about medium and long- term outcome of infants after HPeV infection. The aim of this study is to assess the medium-term outcome in infants following HPeV infection without encephalitis.

METHODS

Patients who suffered HPeV infection involving cerebrospinal fluid were evaluated twice using Ages and Stages Questionnaire-3 (ASQ-3). The first evaluation was conducted at least one year after the infection and the second one year later.

RESULTS

Sixteen patients were evaluated in the first assessment, and three of them presented mild alterations in motor function domains. Moreover, hypotonia was observed in the neurologic exam in one case, and hemiparesis in another case. In the second assessment fifteen patients were included, and only the patient with hemiparesis continued presenting gross motor disfunction, with complete recovery of the remaining patients.

INTERPRETATION

We have observed a good medium-term prognosis in infants after HPeV infections, with improvement of mild motor alterations after at-home intervention. Infants who suffer HPeV infection without encephalitis seem to have a better prognosis than those with encephalitis.

Infant identical triplets' presentation of human parechovirus Type 3

Introduction

Human parechovirus (HPeV) infections appear common across age groups, and transmission is likely fecal-oral and through respiratory secretions. Cyclical and seasonal patterns have been described; however, HPeV has likely been previously underdiagnosed due to lack of commercially available diagnostic testing.

Presentation of Case

We present identical triplets contracting HPeV Type 3.

Discussion

The clinical presentation, similar to echoviruses, is broad and includes asymptomatic shedding, severe pulmonary and neurologic disease, and disseminated intravascular coagulation. Neonates and young infants are particularly susceptible. In neonates, distinctive MRI brain findings have been described that, when combined with clinical presentation, suggest HPeV. Infection clusters have been described, and neonates with older siblings may be a risk factor.

Conclusion

This case suggests that HPeV has been under-recognized in the United States, and HPeV Type 3 prevalence is likely underestimated. The case highlights variation in presentation, including lack of fever and rash, which were previously documented as common HPeV symptoms.

Clinical benefits of introducing real-time multiplex PCR for cerebrospinal fluid as routine diagnostic at a tertiary care pediatric center

BACKGROUND

Sepsis-like illness with suspected meningitis or encephalitis is a common reason for using empiric antimicrobial therapy in infants and children. However, in cases of viral meningitis not covered by these antimicrobials, this management is ineffective and due to side effects potentially harmful.

METHODS

A retrospective analysis of cerebrospinal fluid (CSF) multiplex PCRs (Biofire FilmArray^®) in children with clinical suspicion of meningitis, encephalitis or sepsis-like illness was performed over the period of 1 year. Subsequently, a subgroup of children (age of 8-84 days of life) diagnosed with viral meningitis (enterovirus, HHV-6, human parechovirus) was compared to an age-matched control group.

RESULTS

During the study period, the multiplex PCR panel was performed on 187 individual CSF samples that met the inclusion criteria. About half of the patients (92/187) were less than 1 year of age. In 27 cases (14.4%), the PCR yielded a positive result with the majority (12/27) being indicative of an enteroviral infection. In the age group of 8-84 days of life, 36.4% of the patients had a positive result. When the patients with a PCR positive for a viral agent were compared to an age-matched group of patients, no differences were observed regarding symptoms and laboratory parameters. However, the duration of antimicrobial therapy could be significantly reduced through the use of multiplex PCR.

CONCLUSION

The use of on-site diagnostic multiplex PCR was able to reduce the use of antimicrobials in selected cases. This test can guide clinical decisions earlier during the course of medical care compared to standard diagnostics.

Post-mortem microbiology in sudden death: sampling protocols proposed in different clinical settings

BACKGROUND

Autopsies, including minimally invasive autopsies, are a powerful tool for determination of the cause of death. When a patient dies from an infection, microbiology is crucial to identify the causative organism. Post-mortem microbiology (PMM) aims to detect unexpected infections causing sudden deaths; confirm clinically suspected but unproven infection; evaluate the efficacy of antimicrobial therapy; identify emergent pathogens; and recognize medical errors. Additionally, the analysis of the thanatomicrobiome may help to estimate the post-mortem interval.

AIMS

The aim was to provide advice in the collection of PMM samples and to propose sampling guidelines for microbiologists advising autopsy pathologists facing different sudden death scenarios.

SOURCES

A multidisciplinary team with experts in various fields of microbiology and autopsies on behalf of the ESGFOR (ESCMID - European Society of Clinical Microbiology and Infectious Diseases - study group of forensic and post-mortem microbiology and in collaboration with the European Society of Pathology) developed this narrative review based on a literature search using MedLine and Scopus electronic databases supplemented with their own expertise.

CONTENT

These guidelines address measures to prevent sample contamination in autopsy microbiology; general PMM sampling technique; protocols for PMM sampling in different scenarios and using minimally invasive autopsy; and potential use of the evolving post-mortem microbiome to estimate the post-mortem interval.

IMPLICATIONS

Adequate sampling is paramount to identify the causative organism. Meaningful interpretation of PMM results requires careful evaluation in the context of clinical history, macroscopic and histological findings. Networking and closer collaboration among microbiologists and autopsy pathologists is vital to maximize the yield of PMM.

Severe Parechovirus 3 Infections in Young Infants-Kansas and Missouri, 2014

BACKGROUND

Infection with parechovirus type 3 (PeV3) can cause severe neurologic and sepsis-like illness in young infants; clinical and epidemiologic descriptions have been limited. We aimed to characterize PeV3 illness and explore risk factors for acquisition in a cluster of neonatal cases at Children's Mercy Hospital in Kansas City, Missouri.

METHODS

Cerebrospinal fluid specimens were obtained from infants aged <180 days who were hospitalized with sepsis-like illness or meningitis between June 1 and November 1, 2014. PeV-positive specimens were sequenced at the Centers for Disease Control and Prevention. We reviewed the medical and birth charts of the infants and performed face-to-face parent interviews. We analyzed characteristics according to infant age and intensive care admission status.

RESULTS

We identified 35 cases of PeV infection in infants aged 5 to 56 days. Seven infants required intensive care (median age, 11 days vs 27 days among those who did not require intensive care; P = .0044). Six of these 7 infants had neurologic manifestations consistent with seizures, and all 6 of them were treated with acyclovir but subsequently tested negative for herpes simplex virus. Virus sequences formed 2 lineages, both of which were associated with severe illness. Half of the infants were reported to have household contacts who were ill during the week before onset. Infants aged ≤7 days at onset were more likely to have been delivered at the same hospital.

CONCLUSIONS

PeV3 can cause severe neurologic illness in neonates, and younger infants are more likely to require intensive care. PeV3 should be considered along with herpes simplex virus and other pathogens when evaluating young infants with sepsis-like illness or meningitis. More widespread testing for PeV3 would enable us to gain a better understanding of the clinical scope and circulation of this virus.

High prevalence of developmental concern amongst infants at 12 months following hospitalised parechovirus infection

AIM

The human parechovirus (HPeV) is an increasingly recognised cause of sepsis and central nervous system infection in young infants for which there are limited long-term outcome data. We aimed to assess neurodevelopmental outcome and quality of life in infants following hospitalised HPeV infection.

METHODS

This cohort study was a 12-month follow-up of infants who were hospitalised with confirmed HPeV infection at the Sydney Children's Hospitals Network during an outbreak in Sydney in 2013. Telephone interviews were conducted with parents/guardians. We administered standardised questionnaires, including: Ages and Stages Questionnaire (ASQ), Liverpool Outcome Score-follow-up, Pediatric Quality of Life Inventory(PedsQL) Infant scales and Short-Form health survey (SF-12).

RESULTS

We followed up 46 of 79 infants (58%) aged between 12 and 16 months who had been hospitalised with HPeV infection; 19% showed significant concern in developmental attainment (ASQ3 score <2 standard deviation below population mean), and 50% showed some concern (<1 standard deviation below mean). ASQ3 developmental outcome was associated with the presence of neurodevelopmental sequelae (lower total Liverpool Outcome Score) and poorer health-related quality of life (HRQOL) in physical functioning (PedsQL physical component score), but not overall HRQOL (total PedsQL score) or parental HRQOL (SF-12 scores). No significant associations were identified between clinical or laboratory features during acute hospitalisation and adverse outcome on ASQ3.

CONCLUSIONS

A high proportion of infants show developmental concern at 12-month follow-up post-hospitalisation with HPeV infection. Clinical features during hospitalisation were not associated with adverse outcomes at 12 months. These results suggest that careful follow-up of young infants hospitalised with HPeV disease may be warranted.

Human Parechovirus: an Increasingly Recognized Cause of Sepsis-Like Illness in Young Infants

Human parechovirus (HPeV) is increasingly being recognized as a potentially severe viral infection in neonates and young infants. HPeV belongs to the family Picornaviridae and is currently divided into 19 genotypes. HPeV-1 is the most prevalent genotype and most commonly causes gastrointestinal and respiratory disease. HPeV-3 is clinically the most important genotype due to its association with severe disease in younger infants, which may partly be explained by its distinct virological properties. In young infants, the typical clinical presentation includes fever, severe irritability, and rash, often leading to descriptions of "hot, red, angry babies." Infants with severe central nervous system (CNS) infections are at an increased risk of long-term sequelae. Considering the importance of HPeV as a cause of severe viral infections in young infants, we recommend that molecular diagnostic techniques for early detection be included in the standard practice for the investigation of sepsis-like illnesses and CNS infections in this age group.

Human picornaviruses associated with neurological diseases and their neutralization by antibodies

Picornaviruses are the most commonly encountered infectious agents in mankind. They typically cause mild infections of the gastrointestinal or respiratory tract, but sometimes also invade the central nervous system. There, they can cause severe diseases with long-term sequelae and even be lethal. The most infamous picornavirus is poliovirus, for which significant epidemics of poliomyelitis were reported from the end of the nineteenth century. A successful vaccination campaign has brought poliovirus close to eradication, but neurological diseases caused by other picornaviruses have increasingly been reported since the late 1990s. In this review we focus on enterovirus 71, coxsackievirus A16, enterovirus 68 and human parechovirus 3, which have recently drawn attention because of their links to severe neurological diseases. We discuss the clinical relevance of these viruses and the primary role of humoral immunity in controlling them, and summarize current knowledge on the neutralization of such viruses by antibodies.

Evolutionary and network analysis of virus sequences from infants infected with an Australian recombinant strain of human parechovirus type 3

We present the near complete virus genome sequences with phylogenetic and network analyses of potential transmission networks of a total of 18 Australian cases of human parechovirus type 3 (HPeV3) infection in infants in the period from 2012–2015. Overall the results support our previous finding that the Australian outbreak strain/lineage is a result of a major recombination event that took place between March 2012 and November 2013 followed by further virus evolution and possibly recombination. While the nonstructural coding region of unknown provenance appears to evolve significantly both at the nucleotide and amino acid level, the capsid encoding region derived from the Yamagata 2011 lineage of HPeV3 appears to be very stable, particularly at the amino acid level. The phylogenetic and network analyses performed support a temporal evolution from the first Australian recombinant virus sequence from November 2013 to March/April 2014, onto the 2015 outbreak. The 2015 outbreak samples fall into two separate clusters with a possible common ancestor between March/April 2014 and September 2015, with each cluster further evolving in the period from September to November/December 2015.

Human Zika and West Nile virus neurological infections: What is the difference?

The recent epidemic of West Nile Virus (WNV) infection in the United States was associated with severe neurological disease in immunocompromised hosts, while the emergence of Zika virus infection in the Americas has been notable for an association with increased microcephaly in the fetuses of infected mothers. Rare autopsies of WNV infected humans have shown multiple organ involvement with a clear neurotropism. We have recently had the opportunity to examine the distribution of Zika virus in autopsies of newborns from infected pregnancies. While both viruses infect multiple organs, Zika appears to cause neurological disease in the fetus through two different mechanisms. Infection during the first trimester showed the potential to infect neural progenitor cells causing severe developmental abnormalities, while infection later in gestation was associated with meningeal infection and destructive ischemic lesions of the brain. Both viruses infect kidney tubules but Zika shares a prominent hepatotropism characteristic of other flaviviruses (e.g., Dengue). Limited transplacental Zika infection would be consistent with restriction to primary maternal infections with high viremia. In the absence of a vaccine, restriction of travel by immunosuppressed and pregnant non-immune individuals to endemic regions seems prudent.

An outbreak of severe infections among Australian infants caused by a novel recombinant strain of human parechovirus type 3

Human parechovirus types 1–16 (HPeV1–16) are positive strand RNA viruses in the family Picornaviridae. We investigated a 2015 outbreak of HPeV3 causing illness in infants in Victoria, Australia. Virus genome was extracted from clinical material and isolates and sequenced using a combination of next generation and Sanger sequencing. The HPeV3 outbreak genome was 98.7% similar to the HPeV3 Yamagata 2011 lineage for the region encoding the structural proteins up to nucleotide position 3115, but downstream of that the genome varied from known HPeV sequences with a similarity of 85% or less. Analysis indicated that recombination had occurred, may have involved multiple types of HPeV and that the recombination event/s occurred between March 2012 and November 2013. However the origin of the genome downstream of the recombination site is unknown. Overall, the capsid of this virus is highly conserved, but recombination provided a different non-structural protein coding region that may convey an evolutionary advantage. The indication that the capsid encoding region is highly conserved at the amino acid level may be helpful in directing energy towards the development of a preventive vaccine for expecting mothers or antibody treatment of young infants with severe disease.

Human parechovirus and enterovirus initiate distinct CNS innate immune responses: Pathogenic and diagnostic implications

BACKGROUND

Human parechovirus (HPeV) and enterovirus (EV) cause a range of human diseases including serious CNS infections. Little is known regarding the immune response to HPeV meningitis compared to EV meningitis or how the immune response to HPeV reflects its pathogenesis.

OBJECTIVE

To characterize the innate immune response to HPeV CNS infection in order to increase our understanding of HPeV pathogenesis and possibly help identify HPeV in the clinical setting.

STUDY DESIGN

CSF samples from 13 patients with HPeV meningitis, 7 patients with EV meningitis, and 11 patients negative for CNS infections were analyzed for chemokines/cytokines using multiplex ELISA assays.

RESULTS

CSF levels of the majority of cytokines/chemokines analyzed were significantly higher in patients with EV meningitis (EV group) compared to patients with HPeV meningitis (HPeV group) and controls. In the HPeV group, a small number of cytokine/chemokine levels were higher than controls; however, these levels were either significantly lower or not significantly different compared to the EV group. IL-6 levels were lower in HPeV than in both EV and controls.

CONCLUSIONS

The immune response to HPeV CNS infection differs from that of EV. Distinct patterns of cytokine/chemokine expression in HPeV infections suggest HPeV-mediated modulation of the immune response. HPeV disrupts the interferon cascade and seems to interfere with early inflammatory signaling. Although HPeV elicits a predominantly muted immune reaction, a partial, general infectious-type cytokine/chemokine response does occur. Beyond providing insight into HPeV pathogenesis, the identified cytokine/chemokine profile may aid in early detection of HPeV infection.

Genome analysis revealed novel genotypes and recombination of the human parechoviruses prevalent in children in Eastern China

BACKGROUND

Human parechovirus (HPeV) is a genus of virus in the family Picornaviridae, having two species A and B. HPeVs are common infectious agents, usually causing mild diarrhea and respiratory disease in young children.

RESULTS

Here, we collected and sequenced the near complete genome sequences of 17 novel HPeVs from children with diarrhea in eastern China, which showed significant nucleotide sequence divergence. Phylogenetic analysis based on the complete genomes of these HPeV strains revealed that they belonged to seven different genotypes (including three putative novel genotypes), suggesting that HPeVs showed genotype diversity in this area. Recombination analysis indicated that one of the HPeVs, belonging to HPeV-1 with strain name 146Chzj02, was a recombinant generated by inter-genotype recombination among three HPeV strains belonging to three different genotypes, respectively.

CONCLUSION

Our data revealed the property of the genotype diversity of HPeVs prevalent in children with diarrhea in eastern China, which will be helpful in the future study of the viral evolution of HPeVs and the identification and typing of HPeVs in the clinical laboratory.

Neurotropic virus infections as the cause of immediate and delayed neuropathology

A wide range of viruses from different virus families in different geographical areas, may cause immediate or delayed neuropathological changes and neurological manifestations in humans and animals. Infection by neurotropic viruses as well as the resulting immune response can irreversibly disrupt the complex structural and functional architecture of the central nervous system, frequently leaving the patient or affected animal with a poor or fatal prognosis. Mechanisms that govern neuropathogenesis and immunopathogenesis of viral infections are highlighted, using examples of well-studied virus infections that are associated with these alterations in different populations throughout the world. A better understanding of the molecular, epidemiological and biological characteristics of these infections and in particular of mechanisms that underlie their clinical manifestations may be expected to provide tools for the development of more effective intervention strategies and treatment regimens.

Emerging Infections of CNS: Avian Influenza A Virus, Rift Valley Fever Virus and Human Parechovirus

History is replete with emergent pandemic infections that have decimated the human population. Given the shear mass of humans that now crowd the earth, there is every reason to suspect history will repeat itself. We describe three RNA viruses that have recently emerged in the human population to mediate severe neurological disease. These new diseases are results of new mutations in the infectious agents or new exposure pathways to the agents or both. To appreciate their pathogenesis, we summarize the essential virology and immune response to each agent. Infection is described in the context of known host defenses. Once the viruses evade immune defenses and enter central nervous system (CNS) cells, they rapidly co-opt host RNA processing to a cataclysmic extent. It is not clear why the brain is particularly susceptible to RNA viruses; but perhaps because of its tremendous dependence on RNA processing for physiological functioning, classical mechanisms of host defense (eg, interferon disruption of viral replication) are diminished or not available. Effectiveness of immunity, immunization and pharmacological therapies is reviewed to contextualize the scope of the public health challenge. Unfortunately, vaccines that confer protection from systemic disease do not necessarily confer protection for the brain after exposure through unconventional routes.