The human Parechoviruses: an overview

Prevalence and genetic diversity of Parechovirus

Human parechovirus (HPeV) is a common virus that can cause severe infections in newborns. Due to the limited knowledge of the prevalence of HPeV in different cities in China and the unknown association between HPeV infection and clinical characteristics of newborns, this research investigated the epidemiological and clinical characteristics of HPeV infection in hospitalized neonates in Changsha. From August to October 2023, 145 anal swab samples from 96 newborns and 38 pharyngeal swab samples from 33 newborns in the neonatal intensive care unit (NICU) were collected. The prevalence of HPeV was detected by reverse transcription-polymerase chain reaction (RT-PCR). The genomes of HPeV were sequenced and the viral protein 1 (VP1) region was used for genotyping. Phylogenetic analysis and recombination analysis of HPeV genome were performed. Finally, HPeV was detected in 10 out of 44 patients in October, all of them were HPeV-1. The sequenced 4 genomes of HPeV showed high genetic diversity with known strains. Additionally, a HPeV-1 recombinant strain was detected. Compared with HPeV negative patients, HPeV patients had higher prevalence of abdominal pain and diarrhea, intracranial hemorrhage, and purulent meningitis. Compared with HPeV negative patients, HPeV patients had higher peripheral blood lymphocytes, albumin, globulin, pH and lower peripheral blood neutrophils and hemoglobin. HPeV is an important viral cause of newborn infections and appears to be increasing in prevalence in recent years. Characteristic clinical pictures exist in HPeV infections, and further research is needed to accumulate more cases to obtain a comprehensive understanding of HPeV infections.

Mapping disparities in viral infection rates using highly multiplexed serology

Despite advancements in medical interventions, the disease burden caused by viral pathogens remains large and highly diverse. This burden includes the wide range of signs and symptoms associated with active viral replication as well as a variety of clinical sequelae of infection. Moreover, there is growing evidence supporting the existence of sex- and ethnicity-based health disparities linked to viral infections and their associated diseases. Despite several well-documented disparities in viral infection rates, our current understanding of virus-associated health disparities remains incomplete. This knowledge gap can be attributed, in part, to limitations of the most commonly used viral detection methodologies, which lack the breadth needed to characterize exposures across the entire virome. Additionally, virus-related health disparities are dynamic and often differ considerably through space and time. In this study, we utilize PepSeq, an approach for highly multiplexed serology, to broadly assess an individual's history of viral exposures, and we demonstrate the effectiveness of this approach for detecting infection disparities through a pilot study of 400 adults aged 30-60 in Phoenix, AZ. Using a human virome PepSeq library, we observed expected seroprevalence rates for several common viruses and detected both expected and previously undocumented differences in inferred rates of infection between our male/female and Hispanic/non-Hispanic White individuals.

IMPORTANCE

Our understanding of population-level virus infection rates and associated health disparities is incomplete. In part, this is because of the high diversity of human-infecting viruses and the limited breadth and sensitivity of traditional approaches for detecting infection events. Here, we demonstrate the potential for modern, highly multiplexed antibody detection methods to greatly increase our understanding of disparities in rates of infection across subpopulations (e.g., different sexes or ethnic groups). The use of antibodies as biomarkers allows us to detect evidence of past infections over an extended period, and our approach for highly multiplexed serology (PepSeq) allows us to measure antibody responses against hundreds of viruses in an efficient and cost-effective manner.

Diagnosis, management, and outcomes of parechovirus infections in infants: an overview

Parechovirus A (PeV-A) infections have been detected with increasing frequency in US infants under 6 months of age, leading to a Centers for Disease Control and Prevention (CDC) health advisory in July 2022. Clinicians are advised to consider PeV-A laboratory testing of blood and cerebrospinal fluid when infants present with unexplained fever, sepsis-like illness, or neurological issues. Clinical laboratories are encouraged to offer in-house molecular testing for PeV-A to avoid diagnostic delays, unnecessary use of antibiotics, and prolonged hospitalization of infants presenting with sepsis-like illness. While data are evolving on potential neurodevelopmental sequelae after PeV-A infant central nervous system infections, most infected infants return to baseline health for age. This review examines the PeV-A literature with a focus on PeV-A3, including aspects of epidemiology, clinical presentations/management, laboratory diagnostics, genotyping, and post-infectious sequelae related to PeV-A infections in infants.

Analysis of mild and severe neonatal enterovirus infections in a Chinese neonatal tertiary center: a retrospective case-control study

PURPOSE

To compare the clinical characteristics, virus serotype, and outcome in cases of mild and severe enteroviral infection at a tertiary neonatal intensive care unit in China.

METHODS

A retrospective analysis of cases hospitalized between June and August 2019. Samples (stool or throat swabs) were examined using reverse transcription polymerase chain reaction. Positive cases were divided into two groups: mild infection and severe infection.

RESULTS

A total of 149 cases were assigned to one of two groups: mild infection (n = 104) and severe infection (n = 45). There were no significant differences between the groups in terms of sex, gestational age, birth weight, mode of delivery, and onset within 7 days. Clinical symptoms in both groups mostly resembled sepsis (fever, rash, poor feeding, and lethargy); however, there were significant variations in concomitant symptoms such as hepatitis, thrombocytopenia, encephalitis, coagulopathy, and myocarditis. Severe cases were more likely to have abnormal complete blood counts, biochemical parameters, and cerebrospinal fluid markers. The predominant serotypes implicated in neonatal enterovirus infections were echoviruses and Coxsackievirus B. Invasive ventilation, intravenous immunoglobulin, vasoactive medications, and blood product transfusions were often required, with high mortality rates among severe cases.

CONCLUSION

We found significant differences between mild and severe cases of neonatal enterovirus infection with respect to complications, laboratory findings, and enterovirus serotypes. It is crucial to exercise caution when newborns exhibit symptoms of sepsis, during an enterovirus outbreak. Anemia, thrombocytopenia, abnormal liver function, and coagulation dysfunction should be monitored closely as they could indicate the presence of a severe enteroviral infection.

Parechovirus infection in human brain organoids: host innate inflammatory response and not neuro-infectivity correlates to neurologic disease

Picornaviruses are a leading cause of central nervous system (CNS) infections. While genotypes such as parechovirus A3 (PeV-A3) and echovirus 11 (E11) can elicit severe neurological disease, the highly prevalent PeV-A1 is not associated with CNS disease. Here, we expand our current understanding of these differences in PeV-A CNS disease using human brain organoids and clinical isolates of the two PeV-A genotypes. Our data indicate that PeV-A1 and A3 specific differences in neurological disease are not due to infectivity of CNS cells as both viruses productively infect brain organoids with a similar cell tropism. Proteomic analysis shows that PeV-A infection significantly alters the host cell metabolism. The inflammatory response following PeV-A3 (and E11 infection) is significantly more potent than that upon PeV-A1 infection. Collectively, our findings align with clinical observations and suggest a role for neuroinflammation, rather than viral replication, in PeV-A3 (and E11) infection.

Assessment of the broad-spectrum host targeting antiviral efficacy of halofuginone hydrobromide in human airway, intestinal and brain organotypic models

Halofuginone hydrobromide has shown potent antiviral efficacy against a variety of viruses such as SARS-CoV-2, dengue, or chikungunya virus, and has, therefore, been hypothesized to have broad-spectrum antiviral activity. In this paper, we tested this broad-spectrum antiviral activity of Halofuginone hydrobomide against viruses from different families (Picornaviridae, Herpesviridae, Orthomyxoviridae, Coronaviridae, and Flaviviridae). To this end, we used relevant human models of the airway and intestinal epithelium and regionalized neural organoids. Halofuginone hydrobomide showed antiviral activity against SARS-CoV-2 in the airway epithelium with no toxicity at equivalent concentrations used in human clinical trials but not against any of the other tested viruses.

A Coxsackievirus B1-mediated nonlytic Extracellular Vesicle-to-cell mechanism of virus transmission and its possible control through modulation of EV release

Like most non-enveloped viruses, CVB1 mainly uses cell lysis to spread. Details of a nonlytic virus transmission remain unclear. Extracellular Vesicles (EVs) transfer biomolecules between cells. We show that CVB1 entry into HeLa cells results in apoptosis and release of CVB1-induced 'medium-sized' EVs (CVB1i-mEVs). These mEVs (100-300 nm) harbour CVB1 as shown by immunoblotting with anti-CVB1-antibody; viral capsids were detected by transmission electron microscopy and RT-PCR revealed CVB1 RNA. The percentage of mEVs released from CVB1-infected HeLa cells harbouring virus was estimated from TEM at 34 %. Inhibition of CVB1i-mEV production, with calpeptin or siRNA knockdown of CAPNS1 in HeLa cells limited spread of CVB1 suggesting these vesicles disseminate CVB1 virions to new host cells by a nonlytic EV-to-cell mechanism. This was confirmed by detecting CVB1 virions inside HeLa cells after co-culture with CVB1i-mEVs; EV release may also prevent apoptosis of infected cells whilst spreading apoptosis to secondary sites of infection.

Isolation and characterization of phage display-derived scFv antibodies against human parechovirus 1 VP0 protein

Human parechoviruses (PeVs) are common viruses that are associated with a variety of diseases from mild gastrointestinal and respiratory symptoms to severe central nervous system infections. Until now there has not been antibodies for visualizing parechovirus infection. We used E. coli recombinant PeV-A1-VP0 protein as a target in phage display single chain variable fragment (scFv) antibody library panning. Three rounds of panning allowed identification and isolation of several candidate scFv clones, which tested positive in enzyme-linked immunosorbent assay (ELISA) against VP0. Three scFv clones (scFv-55, -59 and -71) with different CDR-3 sequences were further purified and tested in ELISA, Western blot and immunofluorescence microscopy (IFA) against a set of PeV-A1 isolates and a few isolates representing PeV types 2–6. In IFA, all three scFv binders recognized twenty PeV-A1 isolates. ScFv-55 and -71 also recognized clinical representatives of PeV types 1–6 both in IFA and in capture ELISA, while scFv-59 only recognized PeV-A1, -A2 and -A6. PeV-A1-VP0 (Harris strain) sequence was used to generate a peptide library, which allowed identification of a putative unique conformational antibody epitope with fully conserved flanking regions and a more variable core VVTYDSKL, shared between the scFv antibodies. Sequencing of the VP0 region of virus samples and sequence comparisons against parechoviral sequences in GenBank revealed 107 PeV-A1, -A3, -A8, -A17, -A (untyped) sequences with this exact epitope core sequence, which was most dominant among PeV-A1 isolates. These data suggest the first-time isolation of broad range phage display antibodies against human parechoviruses that may be used in diagnostic antibody development.

Novel Human Parechovirus 3 Diversity, Recombination, and Clinical Impact Across 7 Years: An Australian Story

BACKGROUND

A novel human parechovirus 3 Australian recombinant (HPeV3-AR) strain emerged in 2013 and coincided with biennial outbreaks of sepsis-like illnesses in infants. We evaluated the molecular evolution of the HPeV3-AR strain and its association with severe HPeV infections.

METHODS

HPeV3-positive samples collected from hospitalized infants aged 5-252 days in 2 Australian states (2013-2020) and from a community-based birth cohort (2010-2014) were sequenced. Coding regions were used to conduct phylogenetic and evolutionary analyses. A recombinant-specific polymerase chain reaction was designed and utilized to screen all clinical and community HPeV3-positive samples.

RESULTS

Complete coding regions of 54 cases were obtained, which showed the HPeV3-AR strain progressively evolving, particularly in the 3' end of the nonstructural genes. The HPeV3-AR strain was not detected in the community birth cohort until the initial outbreak in late 2013. High-throughput screening showed that most (>75%) hospitalized HPeV3 cases involved the AR strain in the first 3 clinical outbreaks, with declining prevalence in the 2019-2020 season. The AR strain was not statistically associated with increased clinical severity among hospitalized infants.

CONCLUSIONS

HPeV3-AR was the dominant strain during the study period. Increased hospital admissions may have been from a temporary fitness advantage and/or increased virulence.

Parechovirus A Infection of the Intestinal Epithelium: Differences Between Genotypes A1 and A3

Human parechovirus (PeV-A), one of the species within the Picornaviridae family, is known to cause disease in humans. The most commonly detected genotypes are PeV-A1, associated with mild gastrointestinal disease in young children, and PeV-A3, linked to severe disease with neurological symptoms in neonates. As PeV-A are detectable in stool and nasopharyngeal samples, entry is speculated to occur via the respiratory and gastro-intestinal routes. In this study, we characterized PeV-A1 and PeV-A3 replication and tropism in the intestinal epithelium using a primary 2D model based on human fetal enteroids. This model was permissive to infection with lab-adapted strains and clinical isolates of PeV-A1, but for PeV-A3, infection could only be established with clinical isolates. Replication was highest with infection established from the basolateral side with apical shedding for both genotypes. Compared to PeV-A1, replication kinetics of PeV-A3 were slower. Interestingly, there was a difference in cell tropism with PeV-A1 infecting both Paneth cells and enterocytes, while PeV-A3 infected mainly goblet cells. This difference in cell tropism may explain the difference in replication kinetics and associated disease in humans.

Virome in adult Aedes albopictus captured during different seasons in Guangzhou City, China

Background

The mosquito Aedes albopictus is an important vector for many pathogens. Understanding the virome in Ae. albopictus is critical for assessing the risk of disease transmission, implementation of vector control measures, and health system strengthening.

Methods

In this study, viral metagenomic and PCR methods were used to reveal the virome in adult Ae. albopictus captured in different areas and during different seasons in Guangzhou, China.

Results

The viral composition of adult Ae. albopictus varied mainly between seasons. Over 50 viral families were found, which were specific to vertebrates, invertebrates, plants, fungi, bacteria, and protozoa. In rural areas, Siphoviridae (6.5%) was the most common viral family harbored by mosquitoes captured during winter and spring, while Luteoviridae (1.1%) was the most common viral family harbored by mosquitoes captured during summer and autumn. Myoviridae (7.0% and 1.3%) was the most common viral family in mosquitoes captured in urban areas during all seasons. Hepatitis B virus (HBV) was detected by PCR in a female mosquito pool. The first near full-length HBV genome from Ae. albopictus was amplified, which showed a high level of similarity with human HBV genotype B sequences. Human parechovirus (HPeV) was detected in male and female mosquito pools, and the sequences were clustered with HPeV 1 and 3 sequences.

Conclusions

Large numbers of viral species were found in adult Ae. albopictus, including viruses from vertebrates, insects, and plants. The viral composition in Ae. albopictus mainly varied between seasons. Herein, we are the first to report the detection of HPeV and HBV in mosquitoes. This study not only provides valuable information for the control and prevention of mosquito-borne diseases, but it also demonstrates the feasibility of xenosurveillance.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04922-z.

Maternal parechovirus A (PeV-A) shedding, serostatus, and the risk of central nervous system PeV-A infections in infants

BACKGROUND

Parechovirus A (PeV-A) has emerged as a leading cause of infant central nervous system (CNS) infections. Risk factors associated with infant acquisition of PeV-A are not well understood.

METHODS

We conducted prospective PeV-A/enterovirus (EV) CNS infection surveillance, enrolling 461 hospitalized infants <90 days old who underwent sepsis evaluations and lumbar puncture during 2011-2012. Infants were grouped by RT-PCR detection of PeV-A, EV, or neither virus (Neg) in CSF. We collected demographic/clinical data and tested specimens from all infants. For 427 mothers, we collected demographic/clinical data and evaluated PeV-A3 and EV shedding, and PeV-A3 neutralizing antibody for 147 mothers.

RESULTS

PeV-A was detected in 40 infants (8.7%), 4 in 2011 and 36 in 2012. EV was detected in 35 infants (7.6%), 16 in 2011, and 19 in 2012. PeV-A infected infants presented with irritability, abdominal discomfort, fever, and tachycardia, plus both lymphopenia and absence of CSF pleocytosis which help differentiate PeV-A from EV CNS infection. PeV-A was detected in 9/427 maternal throat swabs; eight of their infants also had PeV-A CNS infection. Infants whose mothers had PeV-A3-positive throat swabs were more likely to be PeV-A3-positive than infants whose mothers had negative throat swabs (relative risk [RR], 13.4 [95% CI, 8.6 - 20.7]). Maternal PeV-A3 seropositivity decreased with increasing maternal age. Mothers of PeV-A-positive infants had lower median PeV-A3 neutralizing titers and were more likely seronegative.

CONCLUSIONS

Maternal viral shedding, serostatus and neutralization titers appear to be important factors in infant PeV-A3 CNS infections.

Year-Round, Routine Testing of Multiple Body Site Specimens for Human Parechovirus in Young Febrile Infants

OBJECTIVES

To test our hypothesis that routine year-round testing of specimens from multiple body sites and genotyping of detected virus would describe seasonal changes, increase diagnostic yield, and provide a better definition of clinical manifestations of human parechovirus (PeV-A) infections in young febrile infants.

STUDY DESIGN

PeV-A reverse-transcriptase polymerase chain reaction (RT-PCR) analysis was incorporated in routine evaluation of infants aged ≤60 days hospitalized at Nationwide Children's Hospital for fever and/or suspected sepsis-like syndrome beginning in July 2013. We reviewed electronic medical records of infants who tested positive for PeV-A between July 2013 and September 2016. Genotyping was performed with specific type 3 RT-PCR and sequencing.

RESULTS

Of 1475 infants evaluated, 130 (9%) tested positive for PeV-A in 1 or more sites: 100 (77%) in blood, 84 (65%) in a nonsterile site, and 53 (41%) in cerebrospinal fluid (CSF). Five infants (4%) were CSF-only positive, 31 (24%) were blood-only positive, and 20 (15%) were nonsterile site-only positive. PeV-A3 was the most common type (85%) and the only type detected in CSF. Although the majority (79%) of infections were diagnosed between July and December, PeV-A was detected year-round. The median age at detection was 29 days. Fever (96%), fussiness (75%), and lymphopenia (56%) were common. Among infants with PeV-A-positive CSF, 77% had no CSF pleocytosis. The median duration of hospitalization was 41 hours. Four infants had bacterial coinfections diagnosed within 24 hours of admission; 40 infants had viral coinfections.

CONCLUSIONS

Although most frequent in summer and fall, PeV-A infections were encountered in every calendar month within the 3-year period of study. More than one-half of patients had PeV-A detected at more than 1 body site. Coinfections were common. PeV-A3 was the most common type identified and the only type detected in the CSF.

Development of Monoclonal Antibodies and Antigen-Capture ELISA for Human Parechovirus Type 3

Human parechovirus type 3 (HPeV3) is an etiologic agent of respiratory diseases, meningitis, and sepsis-like illness in both infants and adults. Monoclonal antibodies (mAbs) can be a promising diagnostic tool for antigenic diseases such as virus infection, as they offer a high specificity toward a specific viral antigen. However, to date, there is no specific mAb available for the diagnosis of HPeV3 infection. In this study, we developed and characterized mAbs specific for HPeV3 capsid protein VP0. We used cell-free, wheat germ-synthesized viral VP0 protein for immunizing BALB/c mice to generate hybridomas. From the resultant hybridoma clones, we selected nine clones producing mAbs reactive to the HPeV3-VP0 antigen, based on enzyme-linked immunosorbent assay (ELISA). Epitope mapping showed that these mAbs recognized three distinct domains in HPeV3 VP0. Six mAbs recognized HPeV3 specifically and the other three mAbs showed cross-reactivity with other HPeVs. Using the HPeV3-specific mAbs, we then developed an ELISA for viral antigen detection that could be reliably used for laboratory diagnosis of HPeV3. This ELISA system exhibited no cross-reactivity with other related viruses. Our newly developed mAbs would, thus, provide a useful set of tools for future research and ensure HPeV3-specific diagnosis.

Parechovirus A Pathogenesis and the Enigma of Genotype A-3

Parechovirus A is a species in the Parechovirus genus within the Picornaviridae family that can cause severe disease in children. Relatively little is known on Parechovirus A epidemiology and pathogenesis. This review aims to explore the Parechovirus A literature and highlight the differences between Parechovirus A genotypes from a pathogenesis standpoint. In particular, the curious case of Parechovirus-A3 and the genotype-specific disease association will be discussed. Finally, a brief outlook on Parechovirus A research is provided.

Emergence of Parechovirus A4 Central Nervous System Infections among Infants in Kansas City, Missouri, USA

Among known parechovirus (PeV) types infecting humans, PeV-A3 (formerly HPeV3) and PeV-A1 (formerly HPeV1) are associated with pediatric central nervous system (CNS) infections. The prevalence of PeV-A3 among hospitalized infants with sepsis-like illness and viral CNS infection is well described; however, the contribution of PeV-A4 to infant CNS infection is relatively unexplored. We report the first 11 U.S. cases of PeV-A4 CNS infections occurring in Kansas City infants during 2010 to 2016 and compare the clinical presentation with that of PeV-A3. PeV-positive cerebrospinal fluid (CSF) specimens from 2010 to 2016 underwent sequencing for genotyping. Among all PeV-CSF positives, PeV-A4 was detected in 11 CSF samples from 2010 to 2016. PeV-A4 was first detected in 2010 (n = 1/4), followed by detections in 2014 (n = 1/39), 2015 (n = 6/9), and 2016 (n = 3/33). The median age of PeV-A4-infected infants in weeks (median, 4; range, 1 to 8) was similar to that of infants infected with PeV-A3 (median, 4; range, 0.25 to 8). Clinical characteristics of PeV-A4 (n = 11) were compared with those of select PeV-A3-infected children (n = 34) with CNS infections and found to be mostly similar, although maximum temperature was higher (P = 0.017) and fever duration was shorter (P = 0.03) for PeV-A4 than for PeV-A3. Laboratory test results were also similar between genotypes, although they showed significantly lower peripheral white blood cell (P = 0.014) and absolute lymphocyte (P = 0.04) counts for PeV-A4 infants. Like PeV-A3, PeV-A4 caused summer-fall seasonal clusters of CNS infections in infants, with mostly similar presentations. Further surveillance is necessary to confirm potential differences in laboratory findings and in fever intensity/duration.

Molecular epidemiology and genetic diversity of human parechoviruses in children hospitalized with acute diarrhea in Thailand during 2011-2016

Little is known about human parechovirus (HPeV) infection in Thailand. The genotype distribution of HPeV strains in children admitted to hospitals with acute gastroenteritis was investigated using polymerase chain reaction (PCR) and nucleotide sequencing of the VP1 region as the detection and genotype identification methods, respectively. Of a total of 2,002 stool samples, 49 (2.4%) were positive for HPeV. Of these, HPeV-1 was the most predominant genotype (40.8%), followed by HPeV-3 (16.3%) and HPeV-14 (16.3%), while HPeV-5, -6, -2, -4, and -8 strains were less frequently detected, at 10.2%, 8.2%, 2%, 2%, and 2%, respectively. HPeV infections were detected throughout the year with the biannual peaks of infection in the rainy (Jun-Jul-Aug) and winter (Nov-Dec-Jan) months in Thailand. Based on VP1 amino acid sequence alignment, the arginyl-glycyl-aspartic acid (RGD) motif was found in HPeV-1, -2, -4, and -6 strains. Additionally, an amino acid insertion at the N-terminus of VP1 was observed in HPeV-4 and HPeV-5 strains. Phylogenetic analysis revealed that small clades of HPeV-1 and HPeV-3 strains emerged in 2016 and 2015, respectively, and dominated in the year of their emergence. The HPeV strains detected in Thailand in this study were most closely related to reference strains from Asia and Europe. The evolutionary rate of HPeV strains was 2.87 × 10^-4 (95% highest posterior density (HPD) 0.10-6.14 × 10^-4) substitutions/site/year. These findings provide information about the genetic diversity and evolutionary dynamics of HPeV genotypes circulating in pediatric patients with acute gastroenteritis in Thailand.

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.

Polarized Entry of Human Parechoviruses in the Airway Epithelium

Human parechoviruses (HPeVs), a poorly studied genus within the Picornaviridae family, are classified into 19 genotypes of which HPeV1 and HPeV3 are the most often detected. HPeV1 VP1 C terminus contains an arginine-glycine-aspartic acid (RGD) motif and has been shown to depend on the host cell surface αV integrins (αV ITGs) and heparan sulfate (HS) for entry. HPeV3 lacks this motif and the receptors remain unknown. HPeVs can be detected in patient nasopharyngeal and stool samples, and infection is presumed to occur after respiratory or gastro-intestinal transmission. HPeV pathogenesis is poorly understood as there are no animal models and previous studies have been conducted in immortalized monolayer cell cultures which do not adequately represent the characteristics of human tissues. To bridge this gap, we determined the polarity of infection, replication kinetics, and cell tropism of HPeV1 and HPeV3 in the well-differentiated human airway epithelial (HAE) model. We found the HAE cultures to be permissive for HPeVs. Both HPeV genotypes infected the HAE preferentially from the basolateral surface while the progeny virus was shed toward the apical side. Confocal microscopy revealed the target cell type to be the p63⁺ basal cells for both viruses, αV ITG and HS blocking had no effect on the replication of either virus, and transcriptional profiling suggested that HPeV3 infection induced stronger immune activation than HPeV1. Genotype-specific host responses may contribute to the differences in pathogenesis and clinical outcomes associated with HPeV1 and HPeV3.

Human parechovirus type 6 and Guillain-Barré syndrome: a case report

A previously healthy 6-year-old boy was admitted to hospital with hypotonia and hyposthenia of lower limbs. Electromyography and slow motor nerve conduction velocity test identified a lower limb acute motor axonal neuropathy. Brain and spinal cord magnetic resonance imaging demonstrated multifocal cortical gray matter lesions in both cerebral hemispheres consistent with gray matter acute disseminated encephalitis otherwise with viral/Mycoplasma pneumoniae encephalitis, and signs of involvement of anterior nerve roots of the cauda equina consistent with Guillain-Barré syndrome. The patient resulted negative to routinely bacterial and viral investigations but positive to human parechovirus that sequence analyses confirmed as type 6. Intravenous immunoglobulins and methylprednisolone treatment were administered but did not relieve the symptoms of Guillain-Barré syndrome. The disease improved gradually over the next 3-month follow-up with a complete remission of both central and peripheral nervous system symptoms.

Neonatal nonpolio enterovirus and parechovirus infections

Nonpolio enteroviruses and parechoviruses are frequent causes of neonatal infection. Clinical manifestations of infection range from asymptomatic infection to mild infection without sequelae to septic shock with muiltiorgan failure. Neonates with clinically apparent infection typically have mothers and/or other contacts with recent symptoms consistent with a viral illness. Severe neonatal infection with nonpolio enterovirus or parechovirus cannot be differentiated clinically from serious bacterial infection. The preferred method for diagnosing neonatal nonpolio enterovirus or parechovirus infection is PCR as it is rapid, sensitive, specific, and commercially available for the detection of virus from various clinical specimens. Investigational agents such as the capsid inhibitors pleconaril and pocapavir show promise for treatment of neonatal enterovirus infections, and other investigational agents are being developed. This review focuses on the epidemiology, diagnosis, and treatment of neonatal nonpolio enterovirus and parechovirus infections.

Strain-dependent neutralization reveals antigenic variation of human parechovirus 3

Human parechovirus 3 (HPeV3), a member of the Picornavirus family, is frequently detected worldwide. However, the observed seropositivity rates for HPeV3 neutralizing antibodies (nAbs) vary from high in Japan to low in the Netherlands and Finland. To study if this can be explained by technical differences or antigenic diversity among HPeV3 strains included in the serological studies, we determined the neutralizing activity of Japanese and Dutch intravenous immunoglobulin batches (IVIG), a rabbit HPeV3 hyperimmune polyclonal serum, and a human HPeV3-specific monoclonal antibody (mAb) AT12-015, against the HPeV3 A308/99 prototype strain and clinical isolates from Japan, the Netherlands and Australia, collected between 1989 and 2015. The rabbit antiserum neutralized all HPeV3 isolates whereas the neutralization capacity of the IVIG batches varied, and the mAb exclusively neutralized the A308/99 strain. Mapping of the amino acid variation among a subset of the HPeV3 strains on an HPeV3 capsid structure revealed that the majority of the surface-exposed amino acid variation was located in the VP1. Furthermore, amino acid mutations in a mAb AT12-015-resistant HPeV3 A308/99 variant indicated the location for potential antigenic determinants. Virus aggregation and the observed antigenic diversity in HPeV3 can explain the varying levels of nAb seropositivity reported in previous studies.

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.

A 4-year Study on Epidemiologic and Molecular Characteristics of Human Parechoviruses and Enteroviruses Circulating in Children Younger Than 5 Years in Northern Italy

BACKGROUND

Human parechovirus (HPeV) and enterovirus (EV) infections are widespread and can lead to a broad range of symptoms, from the common cold to severe disease (SD). Because of the lack of Italian data, this 4-year retrospective cross-sectional study aimed to investigate the frequency, seasonality and molecular characteristics of EV and HPeV circulating in children younger than 5 years.

METHODS

A total of 812 samples were collected from children ≤5 years (56.5% males; median age: 20.6 months; interquartile range: 30.1 months) from September 2010 to August 2014. Two real-time RT-PCR assays were used for EV/HPeV and EV-D68 detection. Phylogenetic analysis was performed on the EV-VP1 gene and the HPeV-VP3/VP1 junction.

RESULTS

16.1% and 5.2% of samples were EV- and HPeV-positive, respectively. One sample was EV-D68-positive. The majority (nearly 80%) of EV/HPeV-positive samples was detected in children ≤3 years, during the summer/autumn seasons. The risk of EV infection was higher in children presenting with SD, whereas the risk of infection from HPeV was higher in infants ≤1 year. Most (61.7%) of molecularly characterized EVs belonged to species B, followed by A (29.4%). The majority (66.7%) of characterized HPeVs were type 1, followed by types 3 (20%) and 6 (13.3%).

CONCLUSIONS

This study shows the significant impact of EV/HPeV circulation in children, particularly among those ≤3 years and during and early autumn, with different pattern of viral strains. The implementation of a national surveillance system could clarify the epidemiologic and clinical characteristics of these viruses in the general population.

Enterovirus and Human Parechovirus Surveillance - United States, 2009-2013

Enteroviruses (EVs) and human parechoviruses (HPeVs) are small, non-enveloped RNA viruses in the Picornaviridae family, which are known or suspected to cause a spectrum of clinical manifestations in humans. Although most infected persons are asymptomatic, mild presentations can include respiratory infections, herpangina, and hand, foot, and mouth disease. Among the more severe syndromes associated with EV and HPeV infection are acute flaccid paralysis, meningitis, encephalitis, myocarditis, and sepsis. Neonates and infants are at higher risk for infection and for severe clinical outcomes than older children or adults (1–3). As of August 2015, a total of 16 HPeV types and 118 EV types (within four EV species known to infect humans: A, B, C, and D) had been identified, and the spectrum of illness caused differed among virus types (4). To describe trends in EV and HPeV circulating in the United States during 2009–2013, CDC summarized detections reported through two surveillance systems. The most commonly reported types of EV and HPeV during this period were coxsackievirus (CV) A6 and HPeV3. The large number of CVA6 detections likely reflected an increase in testing in response to an outbreak of severe hand, foot, and mouth disease in late 2011 and 2012 (5). Most HPeV3 detections originated from a single hospital that routinely tested for HPeV (6). Clinicians and public health practitioners should consider the EV and HPeV types recently circulating in the United States to inform diagnostic and surveillance activities. When EV and HPeV typing is performed, clinical and public health laboratories should routinely report their results to improve the reliability and generalizability of surveillance data.

A child with acute encephalopathy associated with quadruple viral infection

Pediatric acute encephalopathy (AE) was sometimes attributed to virus infection. However, viral infection does not always result in AE. The risk factors for developing infantile AE upon virus infection remain to be determined. Here, we report an infant with AE co-infected with human herpesvirus-6 (HHV-6) and three picornaviruses, including coxsackievirus A6 (CVA6), Enterovirus D68 (EV-D68), and human parechovirus (HPeV). EV-D68 was vertically transmitted to the infant from his mother. CVA6 and HPeV were likely transmitted to the infant at the nursery school. HHV-6 might be re-activated in the patient. It remained undetermined, which pathogen played the central role in the AE pathogenesis. However, active, simultaneous infection of four viruses should have evoked the cytokine storm, leading to the pathogenesis of AE.

CONCLUSION

an infant case with active quadruple infection of potentially AE-causing viruses was seldom reported partly because systematic nucleic acid-based laboratory tests on picornaviruses were not common. We propose that simultaneous viral infection may serve as a risk factor for the development of AE.

Basics of virology

Viruses are important pathogens of the nervous system. Here we describe the basic properties of viruses and the principles of virus classification, evolution, structure, and replication, with a focus on neurotropic viruses that are important neuropathogens of humans. These properties then provide the background for introductions to pathogenesis of viral diseases of the nervous system, host immune responses to virus infection, and the diagnosis and treatment of virus infections of the nervous system.

Human parechovirus genotypes -10, -13 and -15 in Pakistani children with acute dehydrating gastroenteritis

Human parechoviruses are known to cause asymptomatic to severe clinical illness predominantly respiratory and gastroenetric infections. Despite their global prevalence, epidemiological studies have not been performed in Pakistan. In this study, we retrospectively analyzed 110 fecal specimen and found 26 (24%) positive for viral RNA with HPeV-10 (n = 3, 23%), HPeV-13 (n = 4, 31%) and HPeV-15 (n = 6, 46%) genotypes. Clinical features of patients with different HPeV genotypes were compared. All HPeV positive children were aged ≤4 years (mean 13.92 months). The male-to-female ratio was 1: 1.17 (46.2 vs 53.8%) with significant association (p = .031) to HPeV infectivity. HPeV-10 and -13 were found during summer while HPeV-15 was only detected during late winter season. Disease symptoms were more severe in children infected with HPeV-10 and -13 as compared to HPeV-15. Fever and vomiting were observed in 100% cases of HPeV-10 and -13 while only 17% patients of HPeV-15 had these complaints. Phylogenetic analyses showed that HPeV-10, -13 and -15 strains found in this study have 9-13%, 16.8% and 21.8% nucleotide divergence respectively from the prototype strains and were clustered to distinct genetic lineages. This is the first report of HPeV-15 infection in humans although first identified in rhesus macaques. The arginine-glycine-aspartic acid (RGD) motif present at the C-terminal of VP1 responsible for the viral attachment to cellular integrins was not found in all of these strains. In conclusion, these findings enhance our knowledge related to the epidemiology and genetic diversity of the HPeV in Pakistan and support the need for continued laboratory based surveillance programs especially in infants and neonatal clinical settings. Further, the parechovirus pathogenesis, cross-species transmission and disease reservoirs must be ascertained to adopt better prevention measures.

Identification of a novel picornavirus in healthy piglets and seroepidemiological evidence of its presence in humans

In this study, we describe a novel porcine parechovirus-like virus (tentatively named PLV-CHN) from healthy piglets in China using 454 high-throughput sequencing. The complete genome of the virus comprises 6832 bp, encoding a predicted polyprotein of 2132 amino acids that is most similar to Ljungan virus (32% identity). A similar virus that belongs to a novel Picornaviridae genus, named swine pasivirus 1 (SPaV-1), was reported during the preparation of this paper. Sequence analysis revealed that PLV-CHN and SPaV1 shared 82% nucleotide identity and 89% amino acid identity. Further genomic and phylogenetic analyses suggested that both SPaV1 and PLV-CHN shared similar genomic characteristics and belong to the same novel Picornaviridae genus. A total of 36 (20.0%) fecal samples from 180 healthy piglets were positive for PLV-CHN by RT-PCR, while no fecal samples from 100 healthy children and 100 children with diarrhea, and no cerebrospinal fluid samples from 196 children with suspected viral encephalitis, was positive for the virus. However, Western blot and enzyme-linked immunosorbent assays using recombinant PLV-CHN VP1 polypeptide as an antigen showed a high seroprevalence of 63.5% in the healthy population. When grouped by age, the antibody-positivity rates showed that the majority of children under 12 years of age have been infected by the virus. It was suggested that PLV-CHN, SPaV1, or an as-yet-uncharacterized virus can infect humans early in life. Thus, investigation of the role of this novel virus is vital.

Coxsackievirus B transmission and possible new roles for extracellular vesicles

Coxsackievirus B1, a member of the Picornaviridae family is a non-enveloped single-stranded RNA virus associated with human diseases including myocarditis and pancreatitis. Infection of the intestinal mucosa, lined by polarized epithelial cells, requires interaction of coxsackievirus with apically located DAF (decay-accelerating factor) before transport to the basolaterally located CAR (coxsackie and adenovirus receptor), where entry is mediated by endocytosis. As with many other non-enveloped viruses, coxsackievirus has to induce lysis of host cells in order to perpetuate infection. However, recent evidence indicates that virus spread to secondary sites is not only achieved by a lytic mechanism and a non-lytic cell–cell strategy has been suggested for coxsackievirus B3. A physical interaction between infected and non-infected cells has been shown to be an efficient mechanism for retroviral transmission and one type of extracellular vesicle, the exosome, has been implicated in HIV-1 transmission. HIV-1 also takes advantage of depolymerization of actin for spread between T-cells. Calpain-mediated depolymerization of the actin cytoskeleton, as a result of increases in intracellular calcium concentration during coxsackievirus infection, would result in a release of host cell-derived microvesicles. If so, we speculate that maybe such microvesicles, increasingly recognized as major vehicles mediating intercellular communication, could play a role in the intercellular transmission of non-enveloped viruses.

Picornavirus and enterovirus diversity with associated human diseases

Members of the Picornaviridae family are non-enveloped, positive-stranded RNA viruses with a 30nm icosahedral capsid. This virus family exhibits a considerable amount of genetic variability driven both by mutation and recombination. Recently, three previously unknown human picornaviruses, namely the human Saffold cardiovirus, cosavirus and salivirus, have been identified in stools or respiratory samples from subjects presenting symptoms ranging from gastroenteritis to acute flaccid paralysis. However, these viruses were also frequently detected in asymptomatic subjects and their clinical relevance remains to be elucidated. The Enterovirus genus is a prototype example of the Picornaviridae heterogeneity at both genetic and phenotypic levels. This genus is divided into 10 species, seven of which contain human viruses, including three Rhinovirus species. Both human rhino- and enteroviruses are also characterized by high levels of genetic variability, as exemplified by the existence of over 250 different serotypes and the recent discovery of new enterovirus genotypes and the Rhinovirus C species. Despite their common genomic features, rhinoviruses are restricted to the respiratory tract, whereas the vast majority of enteroviruses infect the gastrointestinal tract and can spread to other organs, such as the heart or the central nervous system. Understanding the genetic determinants of such phenotypic diversity is an important challenge and a field for future investigation. Better characterization of these ubiquitous human pathogens may help to develop vaccines or antiviral treatments and to monitor the emergence of new strains.

Identification of human parechovirus genotype, HPeV-12, in a paralytic child with diarrhea

BACKGROUND

New genotypes of human parechoviruses have been readily identified after improvement of diverse diagnostic tools. We hereby report the detection of a new genotype, HPeV 12, from a child presented with diarrhea and paralysis.

OBJECTIVES

The genetic variability of human parechoviruses has recently expanded defining 16 genotypes however data available covers only 11 genotypes. The present study was designed to determine the genetic characterization of human parechovirus identified in a child with gastroenteritis and acute flaccid paralysis (AFP).

STUDY DESIGN

Stool samples are referred to Virology Department, NIH-Pakistan for the routine detection of enteroviruses and polioviruses through cell culture and RT-PCR. Five of isolates showing cytopathic effect on L20B cell line but negative for poliovirus were further explored for human parechovirus using multiple cell lines and RT-PCR.

RESULTS

Human Coxsackie A virus type 2, 3, 6 and 20 were found in four samples whereas the fifth sample contained human parechovirus genotype 12. Efficient growth of human parechovirus was found on L20B cells while Vero and LLC-MK2 cells showed no apparent cytopathic effect.

CONCLUSIONS

This study describes the detection of a new human parechovirus genotype (HPeV-12) in a paralytic child with diarrhea. Human parechoviruses are now considered as potential pathogens that may cause a number of serious clinical complications especially in infants and young children. These findings emphasize to conduct large scale epidemiological surveys in the country to understand their association with clinical diseases especially gastroenteritis, respiratory and neurological disorders.

Nearly constant shedding of diverse enteric viruses by two healthy infants

Stool samples from two healthy infant siblings collected at about weekly intervals during their first year of life were analyzed by PCR for 15 different enteric viral genera. Adenovirus, Aichi virus, Anellovirus, Astrovirus, Bocavirus, Enterovirus, Parechovirus, Picobirnavirus, and Rotavirus were detected. Not detected were Coronavirus, Cardiovirus, Cosavirus, Salivirus, Sapovirus, and Norovirus. Long-term virus shedding, lasting from one to 12 months, was observed for adenoviruses, anelloviruses, bocaviruses, enteroviruses, parechoviruses, and picobirnaviruses. Repeated administration of oral poliovirus vaccine resulted in progressively shorter periods of poliovirus detection. Four nonpolio enterovirus genotypes were also detected. An average of 1.8 distinct human viruses were found per time point. Ninety-two percent (66/72) of the fecal samples tested contained one to five different human viruses. Two British siblings in the mid-1980s showed nearly constant fecal viral shedding. Our results demonstrate that frequent enteric infections with diverse viruses occur during early childhood in the absence of severe clinical symptoms.

Viral infections of the lower respiratory tract

Lower respiratory tract infections (LRTIs) are a global burden to public health and are frequently caused by respiratory viruses. Advances in molecular diagnostic techniques have allowed the identification of previously undetected viral pathogens and have improved our understanding of respiratory virus infections. Here we review the epidemiological and clinical characteristics of recently identified viruses including human metapneumovirus, human coronaviruses NL63 and HKU1, human rhinovirus C, bocavirus, WU and KI polyomaviruses, and parechovirus. The roles of these viruses in LRTIs in children and adults are discussed.