Enterovirus A71 neurologic complications and long-term sequelae

Targeting Ser78 phosphorylation of Hsp27 achieves potent antiviral effects against enterovirus A71 infection

A positive-sense (+) single-stranded RNA (ssRNA) virus (e.g. enterovirus A71, EV-A71) depends on viral polypeptide translation for initiation of virus replication after entry. We reported that EV-A71 hijacks Hsp27 to induce hnRNP A1 cytosol redistribution to initiate viral protein translation, but the underlying mechanism is still elusive. Here, we show that phosphorylation-deficient Hsp27-3A (Hsp27S15/78/82A) and Hsp27S78A fail to translocate into the nucleus and induce hnRNP A1 cytosol redistribution, while Hsp27S15A and Hsp27S82A display similar effects to the wild type Hsp27. Furthermore, we demonstrate that the viral 2A protease (2Apro) activity is a key factor in regulating Hsp27/hnRNP A1 relocalization. Hsp27S78A dramatically decreases the IRES activity and viral replication, which are partially reduced by Hsp27S82A. However, Hsp27S15A displays the same activity as the wild-type Hsp27. Peptide S78 potently suppresses EV-A71 protein translation and reproduction through blockage of EV-A71-induced Hsp27 phosphorylation and Hsp27/hnRNP A1 relocalization. A point mutation (S78A) on S78 impairs its inhibitory functions on Hsp27/hnRNP A1 relocalization and viral replication. Taken together, we demonstrate the importance of Ser78 phosphorylation of Hsp27 regulated by virus infection in nuclear translocation, hnRNP A1 cytosol relocation, and viral replication, suggesting a new path (such as peptide S78) for target-based antiviral strategy.

Epidemiology and molecular detection of human adenovirus and non-polio enterovirus in fecal samples of children with acute gastroenteritis: A five-year surveillance in northern Brazil

Acute gastroenteritis (AGE) is a common pediatric infection that remains a significant cause of childhood morbidity and mortality worldwide, especially in low-income regions. Thus, the objective of this study was to detect human adenovirus (HAdV) and non-polio enterovirus (NPEV) in fecal samples from the Gastroenteritis Surveillance Network, and to identify circulating strains by nucleotide sequencing. A total of 801 fecal samples were tested using qPCR/RT-qPCR, and 657 (82.0%) were inoculated into HEp-2C and RD cell lines. The HAdV and NPEV positivity rates obtained using qPCR/RT-qPCR were 31.7% (254/801) and 10.5% (84/801), respectively, with 5.4% (43/801) co-detection. Cytopathic effect was observed in 9.6% (63/657) of patients, 2.7% (18/657) associated with HAdV, and 6.2% (41/657) associated with NPEV after testing by ICC-PCR. A comparison of the two methodologies demonstrated an agreement of 93.5% for EVNP and 64.4% for HAdV. These two viruses were detected throughout the study period, with HAdV positivity rates ranging from 41% in Amapá to 18% in Pará. The NEPV varied from 18% in Pará/Rondônia to 3% in Acre. The most affected age group was over 60 months for both HAdV and NPEV. Samples previously positive for rotavirus and norovirus, which did not show a major difference in the presence or absence of diarrhea, fever, and vomiting, were excluded from the clinical analyses of these two viruses. These viruses circulated over five years, with a few months of absence, mainly during the months corresponding to the waves of SARS-CoV-2 infection in Brazil. Five HAdV species were identified (A, B, C, D, and F), with a greater predominance of HAdV-F41 (56.5%) followed by HAdV-C (15.2%). Three NPEV species (A, B, and C) were detected, with serotypes E14 (19.3%) and CVA-24 (16.1%) being the most prevalent. The present study revealed a high diversity of NPEV and HAdV types circulating in children with AGE symptoms in the northern region of Brazil.

Neurological manifestations of SARS-CoV-2 infection in children in Taiwan: A cross-section, multicenter study

BACKGROUND

The SARS-CoV-2 virus has been a global public health threat since December 2019. This study aims to investigate the neurological characteristics and risk factors of coronavirus disease 2019 (COVID-19) in Taiwanese children, using data from a collaborative registry.

METHODS

A retrospective, cross-sectional, multi-center study was done using an online network of pediatric neurological COVID-19 cohort collaborative registry.

RESULTS

A total of 11160 COVID-19-associated emergency department (ED) visits and 1079 hospitalizations were analyzed. Seizures were the most common specific neurological symptom, while encephalitis and acute disseminated encephalomyelitis (ADEM) was the most prevalent severe involvement. In ED patients with neurological manifestations, severe neurological diagnosis was associated with visual hallucination, seizure with/without fever, behavior change, decreased GCS, myoclonic jerk, decreased activity/fatigue, and lethargy. In hospitalized patients with neurological manifestations, severe neurological diagnosis was associated with behavior change, visual hallucination, decreased GCS, seizure with/without fever, myoclonic jerk, fatigue, and hypoglycemia at admission. Encephalitis/ADEM was the only risk factor for poor neurological outcomes at discharge in hospitalized patients.

CONCLUSION

Neurological complications are common in pediatric COVID-19. Visual hallucination, seizure, behavior change, myoclonic jerk, decreased GCS, and hypoglycemia at admission are the most important warning signs of severe neurological involvement such as encephalitis/ADEM.

Novel Anti-Enterovirus A71 Compounds Discovered by Repositioning Antivirals from the Open-Source MMV Pandemic Response Box

The open-source drug library, namely, MMV Pandemic Response Box, contains 153 antiviral agents, a chemically and pharmacologically diverse mixture of early-stage, emerging anti-infective scaffolds, and mature compounds currently undergoing clinical development. Hence, the Pandemic Response Box might contain compounds that bind and interfere with target molecules or cellular pathways that are conserved or shared among the closely related viruses with enterovirus A71 (EV-A71). This study aimed to screen antiviral agents included in the Pandemic Response Box for repurposing to anti-EV-A71 activity and investigate the inhibitory effects of the compounds on viral replication. The compounds' cytotoxicity and ability to rescue infected cells were determined by % cell survival using an SRB assay. The hit compounds were verified for anti-EV-A71 activity by virus reduction assays for viral RNA copy numbers, viral protein synthesis, and mature particle production using qRT-PCR, Western blot analysis, and CCID50 assay, respectively. It was found that some of the hit compounds could reduce EV-A71 genome replication and protein synthesis. D-D7 (2-pyridone-containing human rhinovirus 3C protease inhibitor) exhibited the highest anti-EV-A71 activity. Even though D-D7 has been originally indicated as a polyprotein processing inhibitor of human rhinovirus 3C protease, it could be repurposed as an anti-EV-A71 agent.

A 3-month-old neonatal rhesus macaque HFMD model caused by coxsackievirus B1 infection and viral tissue tropism

Coxsackievirus B1 (CVB1), an enterovirus with multiple clinical presentations, has been associated with potential long-term consequences, including hand, foot, and mouth disease (HFMD), in some patients. However, the related animal models, transmission dynamics, and long-term tissue tropism of CVB1 have not been systematically characterized. In this study, we established a model of CVB1 respiratory infection in rhesus macaques and evaluated the clinical symptoms, viral load, and immune levels during the acute phase (0-14 days) and long-term recovery phase (15-30 days). We also investigated the distribution, viral clearance, and pathology during the long-term recovery period using 35 postmortem rhesus macaque tissue samples collected at 30 days postinfection (d.p.i.). The results showed that the infected rhesus macaques were susceptible to CVB1 and exhibited HFMD symptoms, viral clearance, altered cytokine levels, and the presence of neutralizing antibodies. Autopsy revealed positive viral loads in the heart, spleen, pancreas, soft palate, and olfactory bulb tissues. HE staining demonstrated pathological damage to the liver, spleen, lung, soft palate, and tracheal epithelium. At 30 d.p.i., viral antigens were detected in visceral, immune, respiratory, and muscle tissues but not in intestinal or neural tissues. Brain tissue examination revealed viral meningitis-like changes, and CVB1 antigen expression was detected in occipital, pontine, cerebellar, and spinal cord tissues at 30 d.p.i. This study provides the first insights into CVB1 pathogenesis in a nonhuman primate model of HFMD and confirms that CVB1 exhibits tissue tropism following long-term infection.

Enterovirus A71 does not meet the uncoating receptor SCARB2 at the cell surface

Enterovirus A71 (EV-A71) infection involves a variety of receptors. Among them, two transmembrane protein receptors have been investigated in detail and shown to be critical for infection: P-selectin glycoprotein ligand-1 (PSGL-1) in lymphocytes (Jurkat cells), and scavenger receptor class B member 2 (SCARB2) in rhabdomyosarcoma (RD) cells. PSGL-1 and SCARB2 have been reported to be expressed on the surface of Jurkat and RD cells, respectively. In the work reported here, we investigated the roles of PSGL-1 and SCARB2 in the process of EV-A71 entry. We first examined the expression of SCARB2 in Jurkat cells, and detected it within the cytoplasm, but not on the cell surface. Further, using PSGL-1 and SCARB2 knockout cells, we found that although both PSGL-1 and SCARB2 are essential for virus infection of Jurkat cells, virus attachment to these cells requires only PSGL-1. These results led us to evaluate the cell surface expression and the roles of SCARB2 in other EV-A71-susceptible cell lines. Surprisingly, in contrast to the results of previous studies, we found that SCARB2 is absent from the surface of RD cells and other susceptible cell lines we examined, and that although SCARB2 is essential for infection of these cells, it is dispensable for virus attachment. These results indicate that a receptor other than SCARB2 is responsible for virus attachment to the cell and probably for internalization of virions, not only in Jurkat cells but also in RD cells and other EV-A71-susceptible cells. SCARB2 is highly concentrated in lysosomes and late endosomes, where it is likely to trigger acid-dependent uncoating of virions, the critical final step of the entry process. Our results suggest that the essential interactions between EV-A71 and SCARB2 occur, not at the cell surface, but within the cell.

Uncovering Structural Plasticity of Enterovirus A through Deep Insertional and Deletional Scanning

Insertions and deletions (InDels) are essential sources of novelty in protein evolution. In RNA viruses, InDels cause dramatic phenotypic changes contributing to the emergence of viruses with altered immune profiles and host engagement. This work aimed to expand our current understanding of viral evolution and explore the mutational tolerance of RNA viruses to InDels, focusing on Enterovirus A71 (EV-A71) as a prototype for Enterovirus A species (EV-A). Using newly described deep InDel scanning approaches, we engineered approximately 45,000 insertions and 6,000 deletions at every site across the viral proteome, quantifying their effects on viral fitness. As a general trend, most InDels were lethal to the virus. However, our screen reproducibly identified a set of InDel-tolerant regions, demonstrating our ability to comprehensively map tolerance to these mutations. Tolerant sites highlighted structurally flexible and mutationally plastic regions of viral proteins that avoid core structural and functional elements. Phylogenetic analysis on EV-A species infecting diverse mammalian hosts revealed that the experimentally-identified hotspots overlapped with sites of InDels across the EV-A species, suggesting structural plasticity at these sites is an important function for InDels in EV speciation. Our work reveals the fitness effects of InDels across EV-A71, identifying regions of evolutionary capacity that require further monitoring, which could guide the development of Enterovirus vaccines.

Neutralization of African enterovirus A71 genogroups by antibodies to canonical genogroups

Enterovirus 71 (EV-A71) is a major public health problem, causing a range of illnesses from hand-foot-and-mouth disease to severe neurological manifestations. EV-A71 strains have been phylogenetically classified into eight genogroups (A to H), based on their capsid-coding genomic region. Genogroups B and C have caused large outbreaks worldwide and represent the two canonical circulating EV-A71 subtypes. Little is known about the antigenic diversity of new genogroups as compared to the canonical ones. Here, we compared the antigenic features of EV-A71 strains that belong to the canonical B and C genogroups and to genogroups E and F, which circulate in Africa. Analysis of the peptide sequences of EV-A71 strains belonging to different genogroups revealed a high level of conservation of the capsid residues involved in known linear and conformational neutralization antigenic sites. Using a published crystal structure of the EV-A71 capsid as a model, we found that most of the residues that are seemingly specific to some genogroups were mapped outside known antigenic sites or external loops. These observations suggest a cross-neutralization activity of anti-genogroup B or C antibodies against strains of genogroups E and F. Neutralization assays were performed with diverse rabbit and mouse anti-EV-A71 sera, anti-EV-A71 human standards and a monoclonal neutralizing antibody. All the batches of antibodies that were tested successfully neutralized all available isolates, indicating an overall broad cross-neutralization between the canonical genogroups B and C and genogroups E and F. A panel constituted of more than 80 individual human serum samples from Cambodia with neutralizing antibodies against EV-A71 subgenogroup C4 showed quite similar cross-neutralization activities between isolates of genogroups C4, E and F. Our results thus indicate that the genetic drift underlying the separation of EV-A71 strains into genogroups A, B, C, E and F does not correlate with the emergence of antigenically distinct variants.

Structure-based virtual screening of ROCK1 inhibitors for the discovery of Enterovirus-A71 antivirals

Human enterovirus A71 (EV-A71) is the major causative agent of hand, foot, and mouth disease (HFMD), which may lead to neurological sequelae and even death. Although EV-A71 seriously threatens public health, there remains no efficient drug for the treatment of EV-A71 infection. We previously demonstrated that ROCK1 is a novel host dependency factor for EV-A71 replication and can serve as a target for the development of anti-EV-A71 therapeutics. In this study, we identified a subset of inhibitors with potential anti-EV-A71 activity by virtual screening using ROCK1 as a target. Among the hits, Dasabuvir, an HCV polymerase inhibitor, was found to have the best antiviral activity which is consistent with the ranking scores in Autodock Vina and iGEMDOCK. We found that Dasabuvir efficiently suppressed EV-A71 replication in a dose-dependent manner. Moreover, Dasabuvir not only efficiently suppressed the replication of EV-A71 in RD cells, but also in multiple cell lines, including HEK-293T, Caco-2, HT-29, HepG2, and Huh7. Besides, Dasabuvir alleviated the release of proinflammatory cytokines caused by EV-A71 infection. Notably, Dasabuvir also exhibited antiviral activity of CVA10, indicating it may have broad-spectrum antiviral activity against species Enteroviruses A. Hence, our results further confirm that ROCK1 can be a potential drug target and suggest Dasabuvir could be a clinical candidate for the treatment of EV-A71 infection.

Addressing vaccine-preventable encephalitis in vulnerable populations

PURPOSE OF REVIEW

Vaccinations have been pivotal in lowering the global disease burden of vaccine-preventable encephalitides, including Japanese encephalitis, tick-borne encephalitis, measles encephalitis, and rabies encephalitis, among others.

RECENT FINDINGS

Populations vulnerable to vaccine-preventable infections that may lead to encephalitis include those living in endemic and rural areas, military members, migrants, refugees, international travelers, younger and older persons, pregnant women, the immunocompromised, outdoor, healthcare and laboratory workers, and the homeless. There is scope for improving the availability and distribution of vaccinations, vaccine equity, surveillance of vaccine-preventable encephalitides, and public education and information.

SUMMARY

Addressing these gaps in vaccination strategies will allow for improved vaccination coverage and lead to better health outcomes for those most at risk for vaccine-preventable encephalitis.

Factors related to the mortality risk of severe hand, foot, and mouth diseases (HFMD): a 5-year hospital-based survey in Guangxi, Southern China

BACKGROUND

To understand the factors influencing clinical outcomes of severe hand, foot, and mouth diseases (HFMD), and to provide scientific evidence for reducing the mortality risk of severe HFMD.

METHODS

From 2014 to 2018, children diagnosed with severe HFMD cases in Guangxi, China, were enrolled in this hospital-based study. The epidemiological data obtained through face-to-face interviews with the parents and guardians. Univariate and multivariate logistics regression models were used to analyze the factors influencing the clinical outcomes of severe HFMD. The impact of the EV-A71 vaccination on inpatient mortality was analyzed by a comparison approach.

RESULTS

A total of 1565 severe HFMD cases were enrolled in this survey, including 1474 (94.19%) survival cases and 91 (5.81%) death cases. The multivariate logistic analysis demonstrated that HFMD history of playmates in the last three months, first visit to the village hospital, time from the first visit to admission less than two days, no correct diagnosis for HFMD at the first visit, and having no rash symptoms were the independent risk factors for severe HFMD cases (all p < 0.05). While EV-A71 vaccination was a protective factor (p < 0.05). The EV-A71 vaccination group versus the non-vaccination group showed 2.23% of death in the vaccination group and 7.24% of death in the non-vaccination group. The EV-A71 vaccination protected 70.80% of the death of severe HFMD cases, with an effective index of 4.79.

CONCLUSIONS

The mortality risk of severe HFMD in Guangxi was related to playmates had HFMD history in last 3 months, hospital grade, EV-A71 vaccination, patients visit hospital previously, and rash symptom. EV-A71 vaccination can significantly reduce mortality among severe HFMD. The findings are of great significance for the effective prevention and control of HFMD in Guangxi, southern China.

Analysis of the epidemiological trends of enterovirus A in Asia and Europe

BACKGROUND

Enteroviruses have been in massive, cyclical epidemics worldwide. An in-depth understanding of the international epidemiological characteristics of Enterovirus A (EVA) is critical to determining its clinical significance and total disease burden. Although much research has been conducted on EVA epidemiology, there is still a lack of a comprehensive overview of EVA epidemiological characteristics and trends.

OBJECTIVE

EVA nucleic acid sequences from the NCBI virus database were used to summarize the epidemic time (based on the time of specimen collection), spatial and serotype distribution of EVA, and to analyze EVA isolated from cerebrospinal fluid specimens.

METHODS

EVA sequences were searched in NCBI Virus by keyword ("Enterovirus A″ or "EVA") to screen sequences released before December 2021 and sort them to analyze EVA by year, geographic region and serotype prevalence.

RESULTS

The results found 23,041 retrieved nucleic acid sequences with precise collection dates and geographical regions as of December 2021, with Asia accounting for 87%, Europe for 11% and Africa and the Americas for only 2%. Overall, EV-A71, CVA6 and CVA16 are a few of the main prevalent serotypes; and the prevalence characteristics of the different serotypes change over time from place to place.

CONCLUSION

The prevalence of different serotypes of EVA varies considerably over time and space, and we focused on analysing the epidemiological characteristics of EVAs in Asia and Europe and EVAs that invade the nervous system. This study will likely provide important clues for prevention, control and future research in virological surveillance, disease management and vaccine development.

Current status of hand-foot-and-mouth disease

Hand-foot-and-mouth disease (HFMD) is a viral illness commonly seen in young children under 5 years of age, characterized by typical manifestations such as oral herpes and rashes on the hands and feet. These symptoms typically resolve spontaneously within a few days without complications. Over the past two decades, our understanding of HFMD has greatly improved and it has received significant attention. A variety of research studies, including epidemiological, animal, and in vitro studies, suggest that the disease may be associated with potentially fatal neurological complications. These findings reveal clinical, epidemiological, pathological, and etiological characteristics that are quite different from initial understandings of the illness. It is important to note that HFMD has been linked to severe cardiopulmonary complications, as well as severe neurological sequelae that can be observed during follow-up. At present, there is no specific pharmaceutical intervention for HFMD. An inactivated Enterovirus A71 (EV-A71) vaccine that has been approved by the China Food and Drug Administration (CFDA) has been shown to provide a high level of protection against EV-A71-related HFMD. However, the simultaneous circulation of multiple pathogens and the evolution of the molecular epidemiology of infectious agents make interventions based solely on a single agent comparatively inadequate. Enteroviruses are highly contagious and have a predilection for the nervous system, particularly in child populations, which contributes to the ongoing outbreak. Given the substantial impact of HFMD around the world, this Review synthesizes the current knowledge of the virology, epidemiology, pathogenesis, therapy, sequelae, and vaccine development of HFMD to improve clinical practices and public health efforts.

Development of Enterovirus Antiviral Agents That Target the Viral 2C Protein

The Enterovirus (EV) genus includes several important human and animal pathogens. EV-A71, EV-D68, poliovirus (PV), and coxsackievirus (CV) outbreaks have affected millions worldwide, causing a range of upper respiratory, skin, and neuromuscular diseases, including acute flaccid myelitis, and hand-foot-and-mouth disease. There are no FDA-approved antiviral therapeutics for these enteroviruses. This study describes novel antiviral compounds targeting the conserved non-structural viral protein 2C with low micromolar to nanomolar IC₅₀ values. The selection of resistant mutants resulted in amino acid substitutions in the viral capsid protein, implying these compounds may play a role in inhibiting the interaction of 2C and the capsid protein. The assembly and encapsidation stages of the viral life cycle still need to be fully understood, and the inhibitors reported here could be useful probes in understanding these processes.

Antiviral Potential of Melissa officinalis L.: A Literature Review

The use of synthetic drugs has increased in recent years; however, herbal medicine is yet more trusted among a huge population worldwide; This could be due to minimal side effects, affordable prices, and traditional beliefs. Lemongrass (Melissa officinalis) has been widely used for reducing stress and anxiety, increasing appetite and sleep, reducing pain, healing wounds, and treating poisonous insect bites and bee stings for a long time. Today, research has shown that this plant can also fight viruses including Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), Herpes Simplex Virus (HSV), and Human Immunodeficiency Virus (HIV) through various mechanisms such as inhibiting HSV-1 from binding to host cell, inhibiting HSV-1 replication during the post-adsorption or inhibiting main protease and spike protein of SARS-CoV-2, furthermore, be effective in treating related diseases. This Review investigated the antiviral properties of Melissa officinalis and its effect on viral diseases. More in vitro and in vivo studies are needed to determine Melissa officinaliss underlying mechanism, and more randomized controlled trials should be done to identify its effect in humans. Also, due to the usefulness and lack of side effects, it can be used more as a complementary medicine.

Evaluation of multiple consensus criteria for autoimmune encephalitis and temporal analysis of symptoms in a pediatric encephalitis cohort

Objective

To evaluate the sensitivity and specificity of current criteria for the diagnosis of autoimmune encephalitis (AE) and the temporal onset of neuropsychiatric symptoms (NP) in a pediatric encephalitis cohort.

Background

Multiple criteria for AE have been developed, including the Graus and pediatric-focused Cellucci consensus criteria, and the Determining Etiology in Encephalitis (DEE) score for patients with encephalitis. Early identification and treatment of AE is crucial to improve outcomes, but this can be difficult given the frequent overlap of clinical presentation between AE and infectious encephalitis (IE).

Design/methods

A retrospective review was conducted of patients seen at our institution from 2000 to 2021 with a final diagnosis of AE or IE. These were narrowed through multiple exclusions to etiology-confirmed IE or antibody-positive/negative AE. Time of onset or results of all symptoms and diagnostics were recorded. Sensitivity and specificity of each criterion under various clinical scenarios were calculated over the first month after initial NP symptom onset.

Results

A total of 23 antibody-positive AE, 9 antibody-negative AE and 23 IE patients were included in final analysis. Under an idealized scenario with rapid initial diagnostic evaluations, the sensitivity for pediatric AE by day 28 after onset of NP symptoms approached 90% for both Cellucci and Graus criteria. Specificity within these 28 days was low without infectious testing results, increasing the greatest with rapid PCR testing and second with infectious antibody testing-reaching ~90% with both. A DEE score of 3 provided a specificity of 100% in identifying IE, but low sensitivity (29%). Symptoms were noted to cluster within several days of onset in IE, but in AE were spread out. Personality/behavioral change, speech change, affective disorder, and sleep disturbance were noted more often in AE, while fever, elevated C-reactive protein or CSF protein, and abnormal MRI-Brain occurred more often in IE.

Conclusion

In this study, we provide the first evaluation of the Cellucci criteria and the first validation of the DEE score in the differentiation of pediatric AE and IE. Further refinement of AE criteria is needed to improve early detection and treatment of pediatric AE.

Pharmacological Potential of Flavonoids against Neurotropic Viruses

Flavonoids are a group of natural compounds that have been described in the literature as having anti-inflammatory, antioxidant, and neuroprotective compounds. Although they are considered versatile molecules, little has been discussed about their antiviral activities for neurotropic viruses. Hence, the present study aimed to investigate the pharmacological potential of flavonoids in the face of viruses that can affect the central nervous system (CNS). We carried out research from 2011 to 2021 using the Pubmed platform. The following were excluded: articles not in the English language, letters to editors, review articles and papers that did not include any experimental or clinical tests, and papers that showed antiviral activities against viruses that do not infect human beings. The inclusion criteria were in silico predictions and preclinical pharmacological studies, in vitro, in vivo and ex vivo, and clinical studies with flavonoids, flavonoid fractions and extracts that were active against neurotropic viruses. The search resulted in 205 articles that were sorted per virus type and discussed, considering the most cited antiviral activities. Our investigation shows the latest relevant data about flavonoids that have presented a wide range of actions against viruses that affect the CNS, mainly influenza, hepatitis C and others, such as the coronavirus, enterovirus, and arbovirus. Considering that these molecules present well-known anti-inflammatory and neuroprotective activities, using flavonoids that have demonstrated both neuroprotective and antiviral effects could be viewed as an alternative for therapy in the course of CNS infections.

Neurotropic EV71 causes encephalitis by engaging intracellular TLR9 to elicit neurotoxic IL12-p40-iNOS signaling

Brainstem encephalitis, a manifestation of severe enterovirus 71 (EV71) infection, is an acute excessive inflammatory response. The mechanisms underlying its development remain poorly understood. Usually neurotropic viruses trigger acute host immune response by engaging cell surface or intracellular receptors. Here, we show that EV71 engagement with intracellular receptor TLR9 elicits IL-12p40-iNOS signaling causing encephalitis in mice. We identified IL-12p40 to be the only prominent cytokine-induced at the early infection stage in the brainstem of mice subjected to a lethal dose of EV71. The upregulated IL-12p40 proteins were expressed in glial cells but not neuronal cells. To better understand the role of IL-12p40 in severe EV71 infection, we treated the EV71-infected mice with an antibody against IL-12p40 and found the mortality rate, brainstem inflammation, and gliosis to be markedly reduced, suggesting that the acute IL-12p40 response plays a critical role in the pathogenesis of brainstem encephalitis. Mechanistically, intracellular TLR9 was found essential to the activation of the IL-12p40 response. Blocking TLR9 signaling with CpG-ODN antagonist ameliorated IL-12p40 response, brainstem inflammation, and limb paralysis in mice with EV71-induced encephalitis. We further found the glial IL-12p40 response might damage neurons by inducing excess production of neurotoxic NO by iNOS. Overall, EV71 engagement with intracellular TLR9 was found to elicit a neurotoxic glial response via IL12p40-iNOS signaling contributing to the neurological manifestation of EV71 infection. This pathway could potentially be targeted for the treatment of brainstem encephalitis.

Enterovirus A71 antivirals: Past, present, and future

Enterovirus A71 (EV-A71) is a significant human pathogen, especially in children. EV-A71 infection is one of the leading causes of hand, foot, and mouth diseases (HFMD), and can lead to neurological complications such as acute flaccid myelitis (AFM) in severe cases. Although three EV-A71 vaccines are available in China, they are not broadly protective and have reduced efficacy against emerging strains. There is currently no approved antiviral for EV-A71. Significant progress has been made in developing antivirals against EV-A71 by targeting both viral proteins and host factors. However, viral capsid inhibitors and protease inhibitors failed in clinical trials of human rhinovirus infection due to limited efficacy or side effects. This review discusses major discoveries in EV-A71 antiviral development, analyzes the advantages and limitations of each drug target, and highlights the knowledge gaps that need to be addressed to advance the field forward.

N-Acetyltransferase 8 Promotes Viral Replication by Increasing the Stability of Enterovirus 71 Nonstructural Proteins

Enterovirus 71 (EV71) is deemed as a re-emergent pathogen with recent outbreaks worldwide. EV71 infection causes hand, foot and mouth disease (HFMD) and has been associated with severe cardiac and central nervous system complications and even death. Viruses need host factors to complete their life cycle, thus the identification of the host factors for EV71 infection is pivotal to new antiviral research. Emerging evidence has highlighted the importance of protein acetylation during infection of various human viruses. The endoplasmic reticulum, as the prominent organelle of EV71 replication, also has its unique acetylation regulation mechanism. However, the pathogenesis of EV71 and its relationship with the ER-based acetylation machinery are not fully understood. In this study, we demonstrated for the first time that the ER-resident acetyltransferase NAT8 is a host factor for EV71 infection. Inhibiting NAT8 with CRISPR or a small compound significantly suppressed EV71 infection in SK-N-SH cells. NAT8 promoted EV71 replication in an acetyltransferase activity-dependent manner. Additionally, we found NAT8 facilitates EV71 infection through interacting with EV71 2B,3AB and 3C proteins and increasing the stability of these proteins. These results uncovered a novel function of NAT8 and elucidated a new mechanism underlying the regulation of EV71 replication. Importance Enterovirus 71 (EV71) is one of the most common pathogens that cause hand, foot and mouth disease in young children and some patients experience severe or fatal neurologic consequences. To ensure efficient replication, the virus must hijack multiple host factors for its own benefit. Here we show that the ER-resident acetyltransferase NAT8 is a host factor for EV71 infection. EV71 fails to complete its infection in various cells in the absence of NAT8. We further show that NAT8 benefits EV71 replication in an acetyltransferase activity-dependent manner. Finally, we show that NAT8 facilitates EV71 infection through interacting with EV71 2B,3AB and 3C proteins and increasing the stability of these proteins. These results uncovered a novel function of NAT8 in EV71 infection and elucidated a new mechanism underlying the regulation of EV71 replication.

Life-Threatening Enterovirus 71 Encephalitis in Unrelated Children with Autosomal Dominant TLR3 Deficiency

PURPOSE

Enterovirus A71 (EV71) causes a broad spectrum of childhood diseases, ranging from asymptomatic infection or self-limited hand-foot-and-mouth disease (HFMD) to life-threatening encephalitis. The molecular mechanisms underlying these different clinical presentations remain unknown. We hypothesized that EV71 encephalitis in children might reflect an intrinsic host single-gene defect of antiviral immunity. We searched for mutations in the toll-like receptor 3 (TLR3) gene. Such mutations have already been identified in children with herpes simplex virus encephalitis (HSE).

METHODS

We sequenced TLR3 and assessed the impact of the mutations identified. We tested dermal fibroblasts from a patient with EV71 encephalitis and a TLR3 mutation and other patients with known genetic defects of TLR3 or related genes, assessing the response of these cells to TLR3 agonist poly(I:C) stimulation and EV71 infection.

RESULTS

Three children with EV71 encephalitis were heterozygous for rare mutations-TLR3 W769X, E211K, and R867Q-all of which were shown to affect TLR3 function. Furthermore, fibroblasts from the patient heterozygous for the W769X mutation displayed an impaired, but not abolished, response to poly(I:C). We found that TLR3-deficient and TLR3-heterozygous W769X fibroblasts were highly susceptible to EV71 infection.

CONCLUSIONS

Autosomal dominant TLR3 deficiency may underlie severe EV71 infection with encephalitis. Human TLR3 immunity is essential to protect the central nervous system against HSV-1 and EV71. Children with severe EV71 infections, such as encephalitis in particular, should be tested for inborn errors of TLR3 immunity.

Inborn errors of TLR3- or MDA5-dependent type I IFN immunity in children with enterovirus rhombencephalitis

Enterovirus (EV) infection rarely results in life-threatening infection of the central nervous system. We report two unrelated children with EV30 and EV71 rhombencephalitis. One patient carries compound heterozygous TLR3 variants (loss-of-function F322fs2* and hypomorphic D280N), and the other is homozygous for an IFIH1 variant (loss-of-function c.1641+1G>C). Their fibroblasts respond poorly to extracellular (TLR3) or intracellular (MDA5) poly(I:C) stimulation. The baseline (TLR3) and EV-responsive (MDA5) levels of IFN-β in the patients’ fibroblasts are low. EV growth is enhanced at early and late time points of infection in TLR3- and MDA5-deficient fibroblasts, respectively. Treatment with exogenous IFN-α2b before infection renders both cell lines resistant to EV30 and EV71, whereas post-infection treatment with IFN-α2b rescues viral susceptibility fully only in MDA5-deficient fibroblasts. Finally, the poly(I:C) and viral phenotypes of fibroblasts are rescued by the expression of WT TLR3 or MDA5. Human TLR3 and MDA5 are critical for cell-intrinsic immunity to EV, via the control of baseline and virus-induced type I IFN production, respectively.

Epidemiological characteristics and cerebrospinal fluid cytokine profiles of enterovirus encephalitis in children in Hangzhou, China

Enteroviruses (EVs) are common causes of viral encephalitis in children. To better understand the epidemiological and pathological characteristics of EV encephalitis, we enrolled suspected encephalitis patients younger than 15 years old in Hangzhou, China, from October 2016 to September 2019 for cerebrospinal fluid (CSF) collection and analyses. A total of 7735 CSF samples were collected, among which 330 (4.27%) were positive for the EV genome. The positivity rate was significantly higher in boys than girls (χ²  =  5.68, p =  0.02). The monthly case numbers peaked from June to August (80.30%). Among the different age groups, the 0-2 months age group showed the highest number of cases (28.48% of all cases). The 6-7 years (10.82%) and 9-10 years (9.29%) age groups showed the highest EV-positivity rates among suspected encephalitis cases. Sixty-two EV-positive and 53 control CSF samples were collected for Bio-Plex Pro human cytokine assays that simultaneously tested 48 cytokines. Principle component analyses showed significant separation between EV-positive and control samples, but insignificant separation between children and newborns. The levels of 28 cytokines and chemokines were significantly elevated in the EV-positive group including many proinflammatory and a few anti-inflammatory cytokines, as well as chemokines belonging to the CC and CXC subfamilies. Only one cytokine, stem cell growth factor-β, showed a decrease in the EV-positive group. Thus, this study revealed age, sex, and seasonal preferences for EV encephalitis incidences in children and identified many cytokines dysregulated during EV encephalitis.

Long-term neurodevelopment outcomes of hand, foot and mouth disease inpatients infected with EV-A71 or CV-A16, a retrospective cohort study

Hand, foot and mouth disease (HFMD) is a common infectious disease in western Asia area and the full range of the long-term sequelae of HFMD remains poorly described. We conducted a retrospective hospital-based cohort study of HFMD patients with central nervous system (CNS) complications caused by EV-A71 or CV-A16 between 2010 and 2016. Patients were classified into three groups, including CNS only, autonomic nervous system (ANS) dysregulation, and cardiorespiratory failure. Neurologic examination, neurodevelopmental assessments, Magnetic Resonance Imaging (MRI) and lung function, were performed at follow up. Of the 176 patients followed up, 24 suffered CNS only, 133 ANS dysregulation, and 19 cardiorespiratory failure. Median follow-up period was 4.3 years (range [1.4-8.3]). The rate of neurological abnormalities was 25% (43 of 171) at discharge and 10% (17 of 171) at follow-up. The rates of poor outcome were significantly different between the three groups of complications in motor (28%, 38%, 71%) domain (p=0.020), but not for cognitive (20%, 24%, 35%), language (25%, 36%, 41%) and adaptive (24%, 16%, 26%) domains (p = 0.537, p = 0.551, p = 0.403). For children with ventilated during hospitalization, 41% patients (14 of 34) had an obstructive ventilatory defect, and one patient with scoliosis had mixed ventilatory dysfunction. Persistent abnormalities on brain MRI were 0% (0 of 7), 9% (2 of 23) and 57% (4 of 7) in CNS, ANS and cardiorespiratory failure group separately. Patients with HFMD may have abnormalities in neurological, motor, language, cognition, adaptive behaviour and respiratory function. Long-term follow-up programmes for children's neurodevelopmental and respiratory function may be warranted.

The Causes and Long-Term Consequences of Viral Encephalitis

Reports regarding brain inflammation, known as encephalitis, have shown an increasing frequency during the past years. Encephalitis is a relevant concern to public health due to its high morbidity and mortality. Infectious or autoimmune diseases are the most common cause of encephalitis. The clinical symptoms of this pathology can vary depending on the brain zone affected, with mild ones such as fever, headache, confusion, and stiff neck, or severe ones, such as seizures, weakness, hallucinations, and coma, among others. Encephalitis can affect individuals of all ages, but it is frequently observed in pediatric and elderly populations, and the most common causes are viral infections. Several viral agents have been described to induce encephalitis, such as arboviruses, rhabdoviruses, enteroviruses, herpesviruses, retroviruses, orthomyxoviruses, orthopneumovirus, and coronaviruses, among others. Once a neurotropic virus reaches the brain parenchyma, the resident cells such as neurons, astrocytes, and microglia, can be infected, promoting the secretion of pro-inflammatory molecules and the subsequent immune cell infiltration that leads to brain damage. After resolving the viral infection, the local immune response can remain active, contributing to long-term neuropsychiatric disorders, neurocognitive impairment, and degenerative diseases. In this article, we will discuss how viruses can reach the brain, the impact of viral encephalitis on brain function, and we will focus especially on the neurocognitive sequelae reported even after viral clearance.

Assessing In Vitro Resistance Development in Enterovirus A71 in the Context of Combination Antiviral Treatment

There are currently no antivirals available to treat infection with enterovirus A71 (EV-A71) or any other enterovirus. The extensively studied capsid binders rapidly select for drug-resistant variants. We here explore whether the combination of two direct-acting enterovirus inhibitors with a different mechanism of action may delay or prevent resistance development to the capsid binders. To that end, the in vitro dynamics of resistance development to the capsid binder pirodavir was studied either alone or in combination with a viral 2C-targeting compound (SMSK_0213), a viral 3C-protease inhibitor (rupintrivir) or a viral RNA-dependent RNA polymerase inhibitor (7DMA). We demonstrate that combining pirodavir with either rupintrivir or 7DMA delays the development of resistance to pirodavir and that no resistance to the protease or polymerase inhibitor develops. The combination of pirodavir with the 2C inhibitor results in a double-resistant virus population, where only the minority carries the resistant mutation.

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.

[Viruses and bats: interdisciplinary issues]

The virologists' attention to bats (Сhiroptera) changed in the late 20th century as the concept of emerging infections grew in popularity. Since the beginning of the COVID-19 pandemic, the number of publications on bat viruses has increased profoundly.History of the problem; biodiversity of Chiroptera and related viruses; medical and veterinary significance of some viral genera and subgenera (Lyssavirus, Henipavirus, Marburgvirus, Ebolavirus, Sarbecovirus, Merbecovirus), as well as problems of bat protection, are addressed in a concise form. Literature search was carried out in electronic databases, mainly for the period of 2000-2021. Publications in Russian that are poorly represented in English-language reviews are also included. The purpose of the review is to substantiate the importance of an interdisciplinary approach in the context of increased interest in the study of viral infections in bats. This review was written for researchers who have not previously dealt with this problem.Since the beginning of this century, the number of known virus species associated with bats has increased by an order of magnitude (&gt;200). The families Rhabdoviridae, Coronaviridae, Paramyxoviridae are in the first ranks according to the number of findings, and the highest diversity of viruses has been established for the families Vespertilionidae, Pteropodidae, Molossidae. Interdisciplinary cooperation positively influences the efficiency, biological safety and practical significance of the ongoing research. The best results were achieved by multidisciplinary teams with good cross-training in several specialties. Many papers emphasize the need to balance health and conservation interests.The analysis of scientific publications indicates a change in research approaches in this area: from collecting individual facts within the framework of narrow specialties to a comprehensive assessment of new knowledge from ecological, evolutionary and socio-economic positions. Results of the research emphasize the need to maintain complex approaches addressing public health needs and environmental protection. The importance of bat-borne viral infections determines the necessity for correction and interdepartmental coordination of scientific research and surveillance of wildlife zoonoses in the Russian Federation.

Postinfectious Optic Neuritis After Hand-Foot-Mouth Disease

ABSTRACT

A 33-year-old man presented with acute painless loss of vision in his right eye after hand-foot-mouth disease (HFMD). Examination confirmed a right optic neuropathy. Neuroimaging and routine evaluations for alternative causes for an optic neuropathy were negative. He was treated with high dose corticosteroids and made an almost complete visual recovery. Postinfectious optic neuritis has been reported after a vast array of infections including: varicella zoster virus, influenza virus, herpes simplex virus, Epstein-Barr Virus, Lyme disease, and many others. Although Coxsackie virus infections are a known cause of HFMD and have been reported to cause maculopathy, to the best of our knowledge, this is the first reported case of optic neuritis after HFMD in the English language ophthalmic literature.

Seroprevalence and Virologic Surveillance of Enterovirus 71 and Coxsackievirus A6, United Kingdom, 2006-2017

Enterovirus A71 (EV-A71) and coxsackievirus A6 (CVA6) cause hand, foot and mouth disease (HFMD) and are occasionally linked to severe neurologic complications and large outbreaks worldwide. We estimated EV-A71 and CVA6 seroprevalence using cross-sectional age-stratified samples collected in 2006, 2011, and 2017. Seroprevalences of EV-A71 and CVA6 increased from 32% and 54% at 6-11 months to >75% by 10 years of age. Antibody titers declined after 20 years, which could indicate infrequent re-exposure in older populations. Age profiles for acquiring infections and mean titers were comparable in the 3 testing years, despite the marked increase in incidence of CVA6-related HFMD from 2010. The uncoupling of changes in disease severity from the infection kinetics of CVA6 as we inferred from the seroprevalence data, rather than incidence of infection over the 11-year study period, provides further evidence for a change in its pathogenicity.

Implications of Innate Immunity in Post-Acute Sequelae of Non-Persistent Viral Infections

Non-persistent viruses classically cause transient, acute infections triggering immune responses aimed at the elimination of the pathogen. Successful viruses evolved strategies to manipulate and evade these anti-viral defenses. Symptoms during the acute phase are often linked to dysregulated immune responses that disappear once the patient recovers. In some patients, however, symptoms persist or new symptoms emerge beyond the acute phase. Conditions resulting from previous transient infection are termed post-acute sequelae (PAS) and were reported for a wide range of non-persistent viruses such as rota-, influenza- or polioviruses. Here we provide an overview of non-persistent viral pathogens reported to be associated with diverse PAS, among them chronic fatigue, auto-immune disorders, or neurological complications and highlight known mechanistic details. Recently, the emergence of post-acute sequelae of COVID-19 (PASC) or long COVID highlighted the impact of PAS. Notably, PAS of non-persistent infections often resemble symptoms of persistent viral infections, defined by chronic inflammation. Inflammation maintained after the acute phase may be a key driver of PAS of non-persistent viruses. Therefore, we explore current insights into aberrant activation of innate immune signaling pathways in the post-acute phase of non-persistent viruses. Finally, conclusions are drawn and future perspectives for treatment and prevention of PAS are discussed.

First evidence of enterovirus A71 and echovirus 30 in Uruguay and genetic relationship with strains circulating in the South American region

Human enteroviruses (EVs) comprise more than 100 types of coxsackievirus, echovirus, poliovirus and numbered enteroviruses, which are mainly transmitted by the faecal-oral route leading to diverse diseases such as aseptic meningitis, encephalitis, and acute flaccid paralysis, among others. Since enteroviruses are excreted in faeces, wastewater-based epidemiology approaches are useful to describe EV diversity in a community. In Uruguay, knowledge about enteroviruses is extremely limited. This study assessed the diversity of enteroviruses through Illumina next-generation sequencing of VP1-amplicons obtained by RT-PCR directly applied to viral concentrates of 84 wastewater samples collected in Uruguay during 2011-2012 and 2017-2018. Fifty out of the 84 samples were positive for enteroviruses. There were detected 27 different types belonging to Enterovirus A species (CVA2-A6, A10, A16, EV-A71, A90), Enterovirus B species (CVA9, B1-B5, E1, E6, E11, E14, E21, E30) and Enterovirus C species (CVA1, A13, A19, A22, A24, EV-C99). Enterovirus A71 (EV-A71) and echovirus 30 (E30) strains were studied more in depth through phylogenetic analysis, together with some strains previously detected by us in Argentina. Results unveiled that EV-A71 sub-genogroup C2 circulates in both countries at least since 2011-2012, and that the C1-like emerging variant recently entered in Argentina. We also confirmed the circulation of echovirus 30 genotypes E and F in Argentina, and reported the detection of genotype E in Uruguay. To the best of our knowledge this is the first report of the EV-A71 C1-like emerging variant in South-America, and the first report of EV-A71 and E30 in Uruguay.

Enterovirus A71 causing meningoencephalitis and acute flaccid myelitis in a patient receiving rituximab

We present the case of a young woman being treated with rituximab for rheumatoid arthritis who developed a severe enteroviral meningoencephalitis and acute flaccid myelitis (AFM). Cerebrospinal fluid (CSF) and stool reverse transcription-polymerase chain reaction (RT-PCR) testing confirmed the diagnosis and additional sequencing studies performed at the CDC further characterized the enterovirus as enterovirus A71 (EV-A71). After treatment with intravenous immunoglobulin (IVIg) and fluoxetine (based on previous reports of possible efficacy) the patient experienced a remarkable improvement over time. This case highlights the importance of considering enteroviral infection in patients treated with rituximab, depicts a possible clinical course of enteroviral meningoencephalitis and AFM, and illustrates the importance of testing multiple sites for enterovirus infection (CSF, stool, nasopharyngeal swab, blood). Here we present the case with a brief review of the literature pertaining to EV-A71.

Response of Severe EV71-Infected Patients to Hyperimmune Plasma Treatment: A Pilot Study

Hand, foot, and mouth disease (HFMD) is highly prevalent in East and Southeast Asia. It particularly affects children under five years of age. The most common causative agents are coxsackieviruses A6 and A16, and enterovirus A71 (EV71). The clinical presentation is usually mild and self-limited, but, in some cases, severe and fatal complications develop. To date, no specific therapy or worldwide vaccine is available. In general, viral infection invokes both antibody and cell-mediated immune responses. Passive immunity transfer can ameliorate the severe symptoms of diseases such as COVID-19, influenza, MERS, and SARS. Hyperimmune plasma (HIP) from healthy donors with high anti-EV71 neutralizing titer were used to transfuse confirmed EV71-infected children with neurological involvement (n = 6). It resulted in recovery within three days, with no neurological sequelae apparent upon examination 14 days later. Following HIP treatment, plasma chemokines were decreased, whereas anti-inflammatory and pro-inflammatory cytokines gradually increased. Interestingly, IL-6 and G-CSF levels in cerebrospinal fluid declined sharply within three days. These findings indicate that HIP has therapeutic potential for HFMD with neurological complications. However, given the small number of patients who have been treated, a larger cohort study should be undertaken. Successful outcomes would stimulate the development of anti-EV71 monoclonal antibody therapy.

Circulation of enterovirus A71 during 2019-2020, Marseille, France

Enteroviruses A71 (EVs-A71) are known to cause serious neurological infections, especially in the pediatric population. We report here eight cases of EV-A71 infection diagnosed in Marseille over the past 2 years (seven cases in 2019 and one case in 2020). Only children under 5 years of age were affected, including one case of acute flaccid paralysis. Viral RNA was detected by RT-PCR in peripheral samples for all cases (feces and upper respiratory samples). Phylogenetic analyses based on VP1 and 2C3C coding regions revealed that all these cases of EV-A71 infection were caused by viruses belonging to the subgenogroup C1 that currently circulates in Europe and that these viruses are genetically closed to other EVs-A71 recently detected in European countries. These data therefore reinforce the usefulness of the enterovirus surveillance network and the need for systematic screening for EV-A71 in case of an enteroviral infection. This study therefore suggests that the systematic screening for EV-A71 in case of enteroviral infection could provide additional data for enterovirus surveillance networks.

Enterovirus A71 Vaccines

Enterovirus A71 (EV-A71) is a major causative agent of hand, foot, and mouth disease (HFMD) and herpangina. Moreover, EV-A71 infection can lead to neurological complications and death. Vaccination is the most efficient way to control virus infection. There are currently three inactivated, whole EV-A71 vaccines licensed by the China NMPA (National Medical Products Administration). Several other types of vaccines, such as virus-like particles and recombinant VP1 (capsid protein), are also under development. In this review, we discuss recent advances in the development of EV-A71 vaccines.

Vaccine candidates generated by codon and codon pair deoptimization of enterovirus A71 protect against lethal challenge in mice

Enterovirus A71 (EV-A71) causes hand, foot and mouth disease (HFMD) in young children. It is associated with severe neurological complications and death. This study aims to develop a live-attenuated vaccine by codon deoptimization (CD) and codon-pair deoptimization (CPD) of EV-A71. CD is generated by introducing the least preferred codons for amino acids while CPD increases the presence of underrepresented codon pairs in the specific genes. CD and CPD chimeras were generated by synonymous mutations at the VP2, VP3, VP1 and 2A gene regions, designated as XYZ. All twelve deoptimized viruses were viable with similar replication kinetics, but the plaque sizes were inversely proportional to the level of deoptimization. All the deoptimized viruses showed attenuated growth in vitro with reduced viral protein expression at 48 h and lower viral RNA at 39 °C. Six-week-old ICR mice were immunized intraperitoneally with selected CD and CPD X and XY vaccine candidates covering the VP2-VP3 and VP2-VP3-VP1 genes, respectively. All vaccine candidates elicited high anti-EV-A71 IgG levels similar to wild-type (WT) EV-A71. The CD X and CPD X vaccines produced robust neutralizing antibodies but not the CD XY and CPD XY. On lethal challenge, offspring of mice immunized with WT, CD X and CPD X were fully protected, but the CD XY- and CPD XY-vaccinated mice had delayed symptoms and eventually died. Similarly, active immunization of 1-day-old suckling mice with CD X, CPD X and CD XY vaccine candidates provided complete immune protection but CPD XY only protected 40% of the challenged mice. Histology of the muscles from CD X- and CPD X-vaccinated mice showed minimal pathology compared to extensive inflammation in the post-challenged mock-vaccinated mice. Overall, we demonstrated that the CD X and CPD X elicited good neutralizing antibodies, conferred immune protection and are promising live-attenuated vaccine candidates for EV-A71.

Acute flaccid myelitis: cause, diagnosis, and management

Acute flaccid myelitis (AFM) is a disabling, polio-like illness mainly affecting children. Outbreaks of AFM have occurred across multiple global regions since 2012, and the disease appears to be caused by non-polio enterovirus infection, posing a major public health challenge. The clinical presentation of flaccid and often profound muscle weakness (which can invoke respiratory failure and other critical complications) can mimic several other acute neurological illnesses. There is no single sensitive and specific test for AFM, and the diagnosis relies on identification of several important clinical, neuroimaging, and cerebrospinal fluid characteristics. Following the acute phase of AFM, patients typically have substantial residual disability and unique long-term rehabilitation needs. In this Review we describe the epidemiology, clinical features, course, and outcomes of AFM to help to guide diagnosis, management, and rehabilitation. Future research directions include further studies evaluating host and pathogen factors, including investigations into genetic, viral, and immunological features of affected patients, host-virus interactions, and investigations of targeted therapeutic approaches to improve the long-term outcomes in this population.

Emergence of genotype C1 Enterovirus A71 and its link with antigenic variation of virus in Taiwan

An outbreak of the hand-foot-mouth disease with severe neurological cases, mainly caused by the genotype C1 enterovirus A71 (EV-A71), occurred in Taiwan between 2018 and early 2019. In the recent decade, the most dominant EV-A71 genotypes in Taiwan were B5 and C4 but changed to C1 in 2018. Antibody-mediated immunity plays a key role in limiting the EV-A71 illness in humans. However, the level of neutralizing activities against genotype C1 virus by human polyclonal and monoclonal antibodies (MAbs) remains largely unclear. In the study, we demonstrated that that 39% (9 in 23) of post-infection sera from the genotype B5- or C4-infected patients in 2014–2017 exhibit reduced titers with the 2018–2019 genotype C1 viruses than with the earlier B5 and C4 viruses tested. This finding with polyclonal sera is confirmed with human MAbs derived from genotype B5 virus-infected individuals. The 2018–2019 genotype C1 virus is resistant to the majority of canyon-targeting human MAbs, which may be associated with the residue change near or at the bottom of the canyon region on the viral capsid. The remaining three antibodies (16-2-11B, 16-3-4D, and 17-1-12A), which target VP1 S241 on the 5-fold vertex, VP3 E81 on the 3-fold plateau and VP2 D84 on the 2-fold plateau of genotype C1 viral capsid, respectively, retained neutralizing activities with variable potencies. These neutralizing antibodies were also found to be protective against a lethal challenge of the 2018–2019 genotype C1 virus in an hSCARB2-transgenic mice model. These results indicate that the EV-A71-specific antibody response may consist of a fraction of poorly neutralizing antibodies against 2018–2019 genotype C1 viruses among a subset of previously infected individuals. Epitope mapping of protective antibodies that recognize the emerging genotype C1 virus has implications for anti-EV-A71 MAbs and the vaccine field.

EV-A71 is a cause of hand-foot-mouth disease, epidemics of which still regularly occur around the globe. Given that EV-A71 immune protection from the disease correlates with neutralizing antibody responses, but the responses in humans prior to an outbreak are still poorly understood. An outbreak of hand-foot-mouth disease among children emerged in Taiwan from 2018 to 2019, and genotype C1 EV-A71 caused most of the cases. Here, we characterized EV-A71-neutralizing antibody profiles in details at both the serological and monoclonal levels and showed that antibodies generated by humans prior to the emergence of genotype C1 EV-A71 less effectively neutralize C1 compared to the prior circulating genotypes, which implies the presence of antigenic variation in the EV-A71 genotypes. We further identified and mapped critical neutralizing epitopes of 2018–2019 genotype C1 EV-A71 on the top and margin of the viral capsid pentamer and demonstrated the in vivo protective effect of human monoclonal antibodies, which highlight the properties of human antibody-neutralizing sites on EV-A71 and the potential of human antibodies as antiviral agents.

Increased detection of enterovirus A71 infections, Germany, 2019

We report on the increased circulation of enterovirus A71 in Germany in 2019. Strains were mainly identified in hospitalised patients with suspected aseptic meningitis/encephalitis. Molecular analysis showed co-circulation of EV-A71 sub-genogroups C1 and C4, a signal for physicians and public health authorities to include/intensify EV diagnostic in patients showing signs of aseptic meningitis, encephalitis or acute flaccid paralysis/myelitis.

Proteomic Analysis of Cerebrospinal Fluid in Children with Acute Enterovirus-Associated Meningoencephalitis Identifies Dysregulated Host Processes and Potential Biomarkers

Enteroviruses (EVs) are major causes of viral meningoencephalitis in children. To better understand the pathogenesis and identify potential biomarkers, cerebrospinal fluid proteome in children (n = 52) suffering from EV meningoencephalitis was compared to that in EV-negative control subjects (n = 53) using the BoxCar acquisition technique. Among 1697 proteins identified, 1193 with robust assay readouts were used for quantitative analyses. Differential expression analyses identified 154 upregulated and 227 downregulated proteins in the EV-positive group. Functional analyses showed that the upregulated proteins are mainly related to activities of lymphocytes and cytokines, inflammation, and responses to stress and viral invasion, while the downregulated proteins are mainly related to neuronal integrity and activity as well as neurogenesis. According to receiver operating characteristic analysis results, Rho-GDP-dissociation inhibitor 2 exhibited the highest sensitivity (96.2%) and specificity (100%) for discriminating EV-positive from EV-negative patients. The chemokine CXCL10 was most upregulated (>300-fold) with also high sensitivity (92.3%) and specificity (94.3%) for indicating EV positivity. Thus, this study uncovered perturbations of multiple host processes due to EV meningoencephalitis, especially the general trend of enhanced immune responses but impaired neuronal functions. The identified dysregulated proteins may also prompt biomarker development.

Enterovirus-related rhombencephalitis and myelitis in the third trimester of pregnancy: A case report highlighting clinico-radiological findings at diagnosis and follow-up

Rhombencephalitis (RE) refers to inflammatory diseases involving the brainstem and cerebellum. Although RE is a rare entity, it is associated with high morbidity and mortality. The management of such patients is often challenging in terms of identifying the etiology and defining prognosis. Infections, autoimmune and paraneoplastic conditions are commonly implicated. Patients with RE often present with a biphasic illness with an initial flu-like syndrome followed by brainstem dysfunction. CSF pleocytosis, abnormal brain MRI findings, isolation of organism or molecular (PCR/antigen) detection in CSF/blood cultures/stool samples and nasal/rectal swabs help in arriving at a definitive or probable diagnosis. Prompt aggressive treatment with antibacterial and antiviral drugs and/or immunoglobulins along with supportive therapy is crucial for avoiding a poor outcome. We present a case report of a 28-year old female patient who developed RE and myelitis in the third trimester of pregnancy. We aim to highlight the highly suggestive radiological findings which corroborated with the clinical diagnosis of enterovirus infection. The patient's radiological follow-up and neurological sequalae are also described. To the best of our knowledge, ours is the first report which describes the MRI features of this clinical scenario in the third trimester of pregnancy, and also the subsequent clinico-radiological follow up.

Non-polio enterovirus infections in children with central nervous system disorders in Shanghai, 2016-2018: Serotypes and clinical characteristics

BACKGROUND

Non-polio enrerovirus causes a wide spectrum of neurologic syndromes. The epidemiological and clinical profiles of non-polio enrerovirus-associated central nervous system infections vary by regions and over year.

OBJECTIVES

This study aimed to understand the prevalence, serotypes and clinical characteristics of enterovirus-associated aseptic meningitis, encephalitis and meningo-encephalitis in children in Shanghai during 2016-2018.

METHODS

We collected the clinical data and the cerebrospinal fluid specimens from the pediatric patients with aseptic meningitis, encephalitis and meningo-encephalitis during 2016-2018. The nested RT-PCR and sequencing were performed to identify enterovirus and serotypes.

RESULTS

A total of 424 patients were included in this study and their non-duplicated cerebrospinal fluid specimens were collected during the acute stage of illness. Based on PCR assay, enterovirus was detected in 272 (64.15 %) patients, of whom, the ratio of male to female subjects was 1.99, and the mean age was 5.71 ± 3.55 years (range: 0.03-16 years). There were 17 serotypes identified. Echovirus 30 (24.63 %), Coxsackievirus A10 (20.96 %), Coxsackievirus A6 (18.01 %) accounted for 63.6 %, followed by Coxsackievirus B5 (7.72 %), Echovirus 6 (5.88 %), and other serotypes (22.8 %). Of the 10 (3.68 %) critically severe patients, all had refractory seizure, 8 required mechanical ventilation, 7 survivors had recurrent attacks of epilepsy and 3 abandoned treatment; Coxsackievirus A10, Echovirus 9, Coxsackievirus A2, Coxsackievirus A6 and Echovirus 6 were identified.

CONCLUSIONS

Non-polio enterovirus is the major pathogen causing aseptic meningitis, encephalitis and meningo-encephalitis in Chinese children and can cause life-threatening encephalitis and severe sequelae.

Transcriptome sequencing analysis of SH-SY5Y cells infected with EV71 reveals the potential neuropathic mechanisms

Enterovirus A71 (EV71) remains the most common causative agent of hand, foot, and mouth disease (HFMD), and the neurological complications induced by EV71 are usually the leading cause of death in children with HFMD. However, the mechanism of nervous system changes caused by EV71 infection is still unclear. Therefore, in the current study, EV71 was inoculated into the human neuroblastoma cell line SH-SY5Y and subsequent transcriptome sequencing was used to examine the alterations of the transcriptome in infected SH-SY5Y cells. It is expected to determine the underlying mechanism of neurological diseases in response to EV71 infection. As a result, a total of 82,406,974, 112,410,808 and 87,780,371 clean reads were found in the control, EV71-12 h and EV71-24 h groups, respectively. Moreover, 160 and 745 differentially expressed genes were identified in the EV71-12 h and EV71-24 h groups, respectively, as compared to the control group. Next, to further explore the pathogenic mechanism triggered by EV71 infection, we mainly focused on the common differentially expressed genes at different time points of EV71 infection. And it was discovered that there were 95 common differentially expressed genes, which were used to conduct GO and pathway analysis. GO enrichment analysis demarcated related biological processes, molecular functions and cellular components, and KEGG pathway analysis enabled annotations of metabolic pathways and revealed interactions among the significantly enriched pathways. The results showed that the enriched GO term "Nervous system development" and enriched pathway "CCKR signaling map" might be important contributors to EV71-induced neuropathological mechanisms. In addition, we also screened 10 up- and down-regulated non-protein coding genes with significantly different expression in our transcriptome profiling, which suggested that these abnormally regulated non-protein-encoding genes might also play important roles in the pathogenesis of EV71 infection. Eventually, RT-qPCR technology was adopted to validate the transcriptome sequencing data and the experiment demonstrated that the RT-qPCR and transcriptome sequencing results were basically consistent. In summary, this is the first transcriptome analysis of SH-SY5Y cells in response to EV71 infection and provides valuable cues for further exploring the mechanism of nervous system changes caused by EV71 infection.

Functional analyses of mammalian virus 5'UTR-derived, small RNAs that regulate virus translation

Enterovirus A71 (EV-A71¹) RNA contains an internal ribosomal entry site (IRES) to direct cap-independent translation. IRES-dependent translation requires the host's translation initiation factors and IRES-associated trans-acting factors (ITAFs). We previously showed that hnRNP A1, the mRNA stability factor HuR, and the RISC subunit Argonaute 2 (Ago2) are ITAFs that associate with stem loop II (SL-II) of the IRES and promote IRES-dependent translation. By contrast, the mRNA decay factor AUF1 is a negative-acting ITAF that also binds SL-II. Moreover, the small RNA-processing enzyme Dicer produces at least four virus-derived, small RNAs (vsRNAs 1-4) from the EV-A71 5'UTR in infected cells. One of these, vsRNA1, derived from SL-II, inhibits IRES activity via an unknown mechanism. In vitro RNA-binding assays revealed that vsRNA1 can alter association of Ago2, HuR, and AUF1 with SL-II. This presents a possible mechanism by which vsRNA1 could control association of ITAFs with the IRES and modulate viral translation. Here, we describe methods for functional analyses of vsRNA1-mediated regulation of IRES activity. These methods should be applicable to other virus-derived, small RNAs as well.

The RNA-dependent RNA polymerase of enterovirus A71 associates with ribosomal proteins and positively regulates protein translation

Enteroviruses, which may cause neurological complications, have become a public health threat worldwide in recent years. Interactions between cellular proteins and enteroviral proteins could interfere with cellular biological processes to facilitate viral replication in infected cells. Enteroviral RNA-dependent RNA polymerase (RdRP), known as 3D protein, mainly functions as a replicase for viral RNA synthesis in infected cells. However, the 3D protein encoded by enterovirus A71 (EV-A71) could also interact with several cellular proteins to regulate cellular events and responses during infection. To globally investigate the functions of the EV-A71 3D protein in regulating biological processes in host cells, we performed immunoprecipitation coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify host proteins that may associate with the 3D protein. We found that the 3D protein interacts with factors involved in translation-related biological processes, including ribosomal proteins. In addition, polysome profiling analysis showed that the 3D protein cosediments with small and large subunits of ribosomes. We further discovered that the EV-A71 3D protein could enhance EV-A71 internal ribosome entry site (IRES)-dependent translation as well as cap-dependent translation. Collectively, this research demonstrated that the RNA polymerase encoded by EV-A71 could join a functional ribosomal complex and positively regulate viral and host translation.

Hypoxia and therapeutic treatment of EV-A71 with an immune modulator TLR7 agonist in a new immunocompetent mouse model

Background

Enterovirus 71 (EV71 or EV-A71) was first identified in California about half a century ago. In recent years, outbreaks of EV-A71 were prevalent worldwide, including Taiwan, Malaysia, Singapore, Japan, and China. Between 2008 and 2011, China alone reported 1894 deaths associated with EV-A71 infection. In mild cases, EV-A71 can cause herpangina and hand-foot-and-mouth disease (HFMD). However, in severe cases, it could cause neurological disorders, including meningitis and encephalitis. Cardiopulmonary failure is common among hospitalized children with EV-A71 infection. No effective FDA-approved therapeutics against EV-A71 are clinically available.

Methods

We report the establishment of an immunocompetent wild type strain 129 (wt-129) mouse model, which can be cross-species infected with human EV-A71 clinical isolates via an intraperitoneal route.

Results

One intriguing disease phenotype of this new model is the development of characteristic “White-Jade” patches in the muscle, which lost sporadically the normal pink color of uninfected muscle. Viral VP1 protein and massive leukocyte infiltration were detected in muscles with or without white-jades. We demonstrated further that hypoxia is a general phenomenon associated with white-jades in both immunocompetent and immunodeficient mouse models. Therefore, hypoxia appears to be a feature intrinsic to EV-A71 infection, irrespective of its host’s immunogenetic background. To date, no effective treatment for EV-A71 is available. Here, using this new wt-129 mouse model, we showed that timely treatment with compound R837 (a TLR7 immune modulator) via oral or intraperitoneal routes, rescued the hypoxia, limb paralysis, and death at a high therapeutic efficacy.

Conclusions

In this new immunocompetent mouse 129 model, we observed an unexpected white-jade phenotype and its associated hypoxia. The successful treatment with TLR7 immune modulators via an oral route, provide us a new research direction for EV-A71 basic science and translational research. It remains an open issue whether R837 or its related compounds, will be a promising drug candidate in clinical trials in EV-A71 endemic or epidemic areas in the future.