Encephalitis due to emerging viruses: CNS innate immunity and potential therapeutic targets

Exploring the management approaches of cytokines including viral infection and neuroinflammation for neurological disorders

Considerable evidence supports that cytokines are important mediators of pathophysiologic processes within the central nervous system (CNS). Numerous studies have documented the increased production of various cytokines in the human CNS in various neurological and neuropsychiatric disorders. Deciphering cytokine actions in the intact CNS has important implications for our understanding of the pathogenesis and treatment of these disorders. The purpose of this study is to discuss the recent research on treating cytokine storm and amyloids, including stroke, Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's condition, Multi-sclerosis (MS), Amyotrophic Lateral Sclerosis (ALS). Neuroinflammation observed in neurological disorders has a pivotal role in exacerbating Aβ burden and tau hyperphosphorylation, suggesting that stimulating cytokines in response to an undesirable external response could be a checkpoint for treating neurological disorders. Furthermore, the pro-inflammatory cytokines help our immune system through a neuroprotective mechanism in clearing viral infection by recruiting mononuclear cells. This study reveals that cytokine applications may play a vital role in providing novel regulation and methods for the therapeutic approach to neurological disorders and the causes of the deregulation, which is responsible for neuroinflammation and viral infection. However, it needs to be further investigated to clarify better the mechanisms of cytokine release in response to various stimuli, which could be the central point for treating neurological disorders.

MAVS mediates a protective immune response in the brain to Rift Valley fever virus

Rift Valley fever virus (RVFV) is a highly pathogenic mosquito-borne virus capable of causing hepatitis, encephalitis, blindness, hemorrhagic syndrome, and death in humans and livestock. Upon aerosol infection with RVFV, the brain is a major site of viral replication and tissue damage, yet pathogenesis in this organ has been understudied. Here, we investigated the immune response in the brain of RVFV infected mice. In response to infection, microglia initiated robust transcriptional upregulation of antiviral immune genes, as well as increased levels of activation markers and cytokine secretion that is dependent on mitochondrial antiviral-signaling protein (MAVS) and independent of toll-like receptors 3 and 7. In vivo, Mavs^-/- mice displayed enhanced susceptibility to RVFV as determined by increased brain viral burden and higher mortality. Single-cell RNA sequence analysis identified defects in type I interferon and interferon responsive gene expression within microglia in Mavs^-/- mice, as well as dysregulated lymphocyte infiltration. The results of this study provide a crucial step towards understanding the precise molecular mechanisms by which RVFV infection is controlled in the brain and will help inform the development of vaccines and antiviral therapies that are effective in preventing encephalitis.

Rift Valley fever virus causes severe disease in humans and livestock and in some cases can be fatal. There is concern about the use of Rift Valley fever virus as a bioweapon since it can be transmitted through the air, and there are no vaccines or antiviral treatments. Airborne transmission of the virus causes severe inflammation of the brain, yet little is known about the immune response against the virus in this organ. Here, we investigated the immune response in the brain to Rift Valley fever virus following intranasal infection. We determined that microglia, the resident immune cells of the brain, initiate a robust response to Rift Valley fever virus infection and identified a key immune pathway that is critical for the ability of microglia to respond to infection. When this immune pathway is rendered non-functional, mice have a dysregulated response to infection in the brain. This study provides insight into how the immune response can control Rift Valley fever virus infection of the brain.

Early Transcriptional Changes in Rabies Virus-Infected Neurons and Their Impact on Neuronal Functions

Rabies is a zoonotic disease caused by rabies virus (RABV). As rabies advances, patients develop a variety of severe neurological symptoms that inevitably lead to coma and death. Unlike other neurotropic viruses that can induce symptoms of a similar range, RABV-infected post-mortem brains do not show significant signs of inflammation nor the structural damages on neurons. This suggests that the observed neurological symptoms possibly originate from dysfunctions of neurons. However, many aspects of neuronal dysfunctions in the context of RABV infection are only partially understood, and therefore require further investigation. In this study, we used differentiated neurons to characterize the RABV-induced transcriptomic changes at the early time-points of infection. We found that the genes modulated in response to the infection are particularly involved in cell cycle, gene expression, immune response, and neuronal function-associated processes. Comparing a wild-type RABV to a mutant virus harboring altered matrix proteins, we found that the RABV matrix protein plays an important role in the early down-regulation of host genes, of which a significant number is involved in neuronal functions. The kinetics of differentially expressed genes (DEGs) are also different between the wild type and mutant virus datasets. The number of modulated genes remained constant upon wild-type RABV infection up to 24 h post-infection, but dramatically increased in the mutant condition. This result suggests that the intact viral matrix protein is important to control the size of host gene modulation. We then examined the signaling pathways previously studied in relation to the innate immune responses against RABV, and found that these pathways contribute to the changes in neuronal function-associated processes. We further examined a set of regulated genes that could impact neuronal functions collectively, and demonstrated in calcium imaging that indeed the spontaneous activity of neurons is influenced by RABV infection. Overall, our findings suggest that neuronal function-associated genes are modulated by RABV early on, potentially through the viral matrix protein-interacting signaling molecules and their downstream pathways.

Modulating Neurological Complications of Emerging Infectious Diseases: Mechanistic Approaches to Candidate Phytochemicals

Growing studies are revealing the critical manifestations of influenza, dengue virus (DENV) infection, Zika virus (ZIKV) disease, and Ebola virus disease (EVD) as emerging infectious diseases. However, their corresponding mechanisms of major complications headed for neuronal dysfunction are not entirely understood. From the mechanistic point of view, inflammatory/oxidative mediators are activated during emerging infectious diseases towards less cell migration, neurogenesis impairment, and neuronal death. Accordingly, the virus life cycle and associated enzymes, as well as host receptors, cytokine storm, and multiple signaling mediators, are the leading players of emerging infectious diseases. Consequently, chemokines, interleukins, interferons, carbohydrate molecules, toll-like receptors (TLRs), and tyrosine kinases are leading orchestrates of peripheral and central complications which are in near interconnections. Some of the resulting neuronal manifestations have attracted much attention, including inflammatory polyneuropathy, encephalopathy, meningitis, myelitis, stroke, Guillain-Barré syndrome (GBS), radiculomyelitis, meningoencephalitis, memory loss, headaches, cranial nerve abnormalities, tremor, and seizure. The complex pathophysiological mechanism behind the aforementioned complications urges the need for finding multi-target agents with higher efficacy and lower side effects. In recent decades, the natural kingdom has been highlighted as promising neuroprotective natural products in modulating several dysregulated signaling pathways/mediators. The present study provides neuronal manifestations of some emerging infectious diseases and underlying pathophysiological mechanisms. Besides, a mechanistic-based strategy is developed to introduce candidate natural products as promising multi-target agents in combating major dysregulated pathways towards neuroprotection in influenza, DENV infection, ZIKV disease, and EVD.

Honeysuckle Aqueous Extracts Induced let-7a Suppress EV71 Replication and Pathogenesis In Vitro and In Vivo and Is Predicted to Inhibit SARS-CoV-2

Honeysuckle (Lonicera japonica Thunb) is a traditional Chinese medicine (TCM) with an antipathogenic activity. MicroRNAs (miRNAs) are small non-coding RNA molecules that are ubiquitously expressed in cells. Endogenous miRNA may function as an innate response to block pathogen invasion. The miRNA expression profiles of both mice and humans after the ingestion of honeysuckle were obtained. Fifteen overexpressed miRNAs overlapped and were predicted to be capable of targeting three viruses: dengue virus (DENV), enterovirus 71 (EV71) and SARS-CoV-2. Among them, let-7a was examined to be capable of targeting the EV71 RNA genome by reporter assay and Western blotting. Moreover, honeysuckle-induced let-7a suppression of EV71 RNA and protein expression as well as viral replication were investigated both in vitro and in vivo. We demonstrated that let-7a targeted EV71 at the predicted sequences using luciferase reporter plasmids as well as two infectious replicons (pMP4-y-5 and pTOPO-4643). The suppression of EV71 replication and viral load was demonstrated in two cell lines by luciferase activity, RT-PCR, real-time PCR, Western blotting and plaque assay. Furthermore, EV71-infected suckling mice fed honeysuckle extract or inoculated with let-7a showed decreased clinical scores and a prolonged survival time accompanied with decreased viral RNA, protein expression and virus titer. The ingestion of honeysuckle attenuates EV71 replication and related pathogenesis partially through the upregulation of let-7a expression both in vitro and in vivo. Our previous report and the current findings imply that both honeysuckle and upregulated let-7a can execute a suppressive function against the replication of DENV and EV71. Taken together, this evidence indicates that honeysuckle can induce the expression of let-7a and that this miRNA as well as 11 other miRNAs have great potential to prevent and suppress EV71 replication.

Enterovirus A71 capsid protein VP1 increases blood-brain barrier permeability and virus receptor vimentin on the brain endothelial cells

Enterovirus A71 (EV-A71) is the major cause of severe hand-foot-and-mouth diseases (HFMD), especially encephalitis and other nervous system diseases. EV-A71 capsid protein VP1 mediates virus attachment and is the important virulence factor in the EV-A71pathogenesis. In this study, we explored the roles of VP1 in the permeability of blood-brain barrier (BBB). Sera albumin, Evans blue, and dextran leaked into brain parenchyma of the 1-week-old C57BL/6J mice intracranially injected with VP1 recombinant protein. VP1 also increased the permeability of the brain endothelial cells monolayer, an in vitro BBB model. Tight junction protein claudin-5 was reduced in the brain tissues or brain endothelial cells treated with VP1. In contrast, VP1 increased the expression of virus receptor vimentin, which could be blocked with VP1 neutralization antibody. Vimentin expression in the VP1-treated brain endothelial cells was regulated by TGF-β/Smad-3 and NF-κB signal pathways. Moreover, vimentin over-expression was accompanied with compromised BBB. From these studies, we conclude that EV-A71 virus capsid protein VP1 disrupted BBB and increased virus receptor vimentin, which both may contribute to the virus entrance into brain and EV-A71 CNS infection.

Pathogenesis of hand-foot-mouth disease caused by enterovirus 71

Hand-foot-mouth disease (HFMD) is a global infectious disease. The infected population is mainly infants and young children. Enterovirus 71 (EV71) is the main pathogen. In addition to HFMD, EV71 infection can also affect the nervous system and other organs, resulting in aseptic meningitis, brainstem encephalitis, and poliomyelitis-like paralysis, causing serious harm to children's health. At present, the pathogenesis of HFMD caused by EV71 is still unclear, and there is no effective treatment. In this paper, we discuss the factors influencing EV71 infection from the aspects of virus gene recombination and spontaneous mutation, host genes, and receptor sites, review the pathogenesis of HFMD caused by EV71 based on the study findings from animal infection models, and explore the main problems in the study of pathogenesis of this condition, in order to provide reference for the prevention and treatment of HFMD and for the development of new drugs or effective vaccines for EV71 infection.

Ebola virus disease: Essential clinical knowledge

Since its initial outbreak in 1976, Ebola virus disease (EVD) has affected thousands of people, causing severe illness with high mortality rates. In the absence of a vaccine or effective specific treatment, as well as the lack of early diagnostic and detective methods, the EVD outbreak has generated a significant worldwide health concern. Insufficient health-care system resources, deficient infection control measures, and the shortage of appropriate personal protective equipment acted as amplifiers of the outbreak extension, especially in poorly resourced and unprepared communities. Operating on the frontlines, health-care workers must be familiar, not only with the identification of the disease, but also with the ability to protect themselves and initiate the appropriate response. This review seeks to provide essential information required to identify and manage the disease, with an emphasis on pathogenesis, transmission, diagnosis, treatment, and prevention. We conducted a literature search in MEDLINE/PubMed and Google Scholar using the following keywords: "Ebola, Ebola virus disease, Hemorrhagic Fever, Outbreak." We included all types of publications. To augment our study, we searched the reference lists of identified reviews.

Valosin-containing protein (VCP/p97) plays a role in the replication of West Nile virus

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Inhibition of VCP by chemical inhibitors decreased WNV infection in a dose-dependent manner.

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Knockdown of endogenous VCP level using siRNA suppressed WNV infection.

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Depletion of VCP levels suppressed WNV infection at the early stages of WNV replication cycle.

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Depletion of VCP levels lowered nascent WNV genomic RNA.

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VCP participates in early stages and viral genomic RNA replication.

Valosin-containing protein (VCP) is classified as a member of the type II AAA⁺ ATPase protein family. VCP functions in several cellular processes, including protein degradation, membrane fusion, vesicular trafficking and disassembly of stress granules. Moreover, VCP is considered to play a role in the replication of several viruses, albeit through different mechanisms. In the present study, we have investigated the role of VCP in West Nile virus (WNV) infection. Endogenous VCP expression was inhibited using either VCP inhibitors or by siRNA knockdown. It could be shown that the inhibition of endogenous VCP expression significantly inhibited WNV infection. The entry assay revealed that silencing of endogenous VCP caused a significant reduction in the expression levels of WNV-RNA compared to control siRNA-treated cells. This indicates that VCP may play a role in early steps either the binding or entry steps of the WNV life cycle. Using WNV virus like particles and WNV-DNA-based replicon, it could be demonstrated that perturbation of VCP expression decreased levels of newly synthesized WNV genomic RNA. These findings suggest that VCP is involved in early steps and during genome replication of the WNV life cycle.

Biomarkers in Cerebrospinal Fluid of Children With Tick-borne Encephalitis: Association With Long-term Outcome

BACKGROUND

Tick-borne encephalitis (TBE) is a major cause of meningoencephalitis in children in endemic areas, and long-term residual problems are not uncommon. Currently, no predictive markers in the acute phase are available that identify children at risk of incomplete recovery. We measured cytokines, chemokines and markers of neuronal damage in cerebrospinal fluid (CSF) in children with TBE and central nervous system (CNS) involvement.

METHODS

CSF from 37 children with TBE with CNS involvement was analyzed. Concentrations of 16 cytokines, chemokines and 5 markers of neuronal damage were assessed in CSF, using a multiplex assay, and correlated with clinical findings in the acute phase (n = 37), and with long-term outcome (n=22).

RESULTS

Significantly higher levels of CSF interferon (IFN)-γ, interleukin (IL)-4, IL-6 and IL-8 were detected in the acute phase from children who later developed sequelae. Although most of the studied markers of neuronal damage displayed no significant differences between children with sequelae and those with good outcome, neuron-specific enolase correlated inversely. The grade of CSF pleocytosis correlated positively with the levels of IFN-γ, IL-4 and IL-6; however, pleocytosis alone did not predict sequelae. Increasing age correlated positively with IL-4, IL-6 and IL-8 values.

CONCLUSIONS

The mechanism underlying the CNS pathology causing sequelae in TBE appears related to the grade of inflammation in CNS, rather than to direct neuronal destruction. High concentration of IFN-γ, IL-4, IL-6 and IL-8 in CSF might indicate a risk for incomplete recovery in childhood TBE.

Ebola Virus-Related Encephalitis

Ebola patients frequently exhibit behavioral modifications with ideation slowing and aggressiveness, sometimes contrasting with mild severity of Ebola disease. We performed lumbar punctures in 3 patients with this presentation and found Ebola virus in all cerebrospinal fluid samples. This discovery helps to discuss the concept of a specific Ebola virus encephalitis.

Interferon gamma protects neonatal neural stem/progenitor cells during measles virus infection of the brain

BACKGROUND

In the developing brain, self-renewing neural stem/progenitor cells (NSPC) give rise to neuronal and glial lineages. NSPC survival and differentiation can be altered by neurotropic viruses and by the anti-viral immune response. Several neurotropic viruses specifically target and infect NSPCs, in addition to inducing neuronal loss, which makes it difficult to distinguish between effects on NSPCs that are due to direct viral infection or due to the anti-viral immune response.

METHODS

We have investigated the impact of anti-viral immunity on NSPCs in measles virus (MV)-infected neonates. A neuron-restricted viral infection model was used, where NSPCs remain uninfected. Thus, an anti-viral immune response was induced without the confounding issue of NSPC infection. Two-transgenic mouse lines were used: CD46+ mice express the human isoform of CD46, the MV entry receptor, under the control of the neuron-specific enolase promoter; CD46+/IFNγ-KO mice lack the key anti-viral cytokine IFNγ. Multi-color flow cytometry and Western Blot analysis were used to quantify effects on NSPC, neuronal, and glial cell number, and quantify effects on IFNγ-mediated signaling and cell markers, respectively.

RESULTS

Flow cytometric analysis revealed that NSPCs were reduced in CD46+/IFNγ-KO mice at 3, 7, and 10 days post-infection (dpi), but were unaffected in CD46+ mice. Early neurons showed the greatest cell loss at 7 dpi in both genotypes, with no effect on mature neurons and glial cells. Thus, IFNγ protected against NSPC loss, but did not protect young neurons. Western Blot analyses on hippocampal explants showed reduced nestin expression in the absence of IFNγ, and reduced doublecortin and βIII-tubulin in both genotypes. Phosphorylation of STAT1 and STAT2 occurred independently of IFNγ in the hippocampus, albeit with distinct regulation of activation.

CONCLUSIONS

This is the first study to demonstrate bystander effects of anti-viral immunity on NSPC function. Our results show IFNγ protects the NSPC population during a neonatal viral CNS infection. Significant loss of NSPCs in CD46+/IFNγ-KO neonates suggests that the adaptive immune response is detrimental to NSPCs in the absence of IFNγ. These results reveal the importance and contribution of the anti-viral immune response to neuropathology and may be relevant to other neuroinflammatory conditions.

Toscana virus infects dendritic and endothelial cells opening the way for the central nervous system

Toscana virus (TOSV) is a Phlebovirus responsible for human neurological infections in endemic Mediterranean areas. The main viral target is the central nervous system, with viremia as a way of dissemination throughout the host. This study was aimed at understanding the spread of TOSV in the host by identifying the cell population infected by the virus and the vehicle to the organs. In vivo studies provided evidence that endothelial cells are infected by TOSV, indicating their potential role in the diffusion of the virus following viremic spread. These results were further confirmed in vitro. Human peripheral mononuclear blood cells were infected with TOSV; only monocyte-derived dendritic cells were identified as susceptible to TOSV infection. Productive viral replication was then observed in human monocyte-derived dendritic cells (moDCs) and in human endothelial cells by recovery of the virus from a cell supernatant. Interleukin-6 was produced by both cell types upon TOSV infection, mostly by endothelial cells, while moDCs particularly expressed TNF-α, which is known to induce a long-lasting decrease in endothelial cell barrier function. These cells could therefore be implicated in the spread of the virus in the host and in the infection of tissues that are affected by the disease, such as the central nervous system. The identification of in vitro and in vivo TOSV cell targets is an important tool for understanding the pathogenesis of the infection, providing new insight into virus-cell interaction for improved knowledge and control of this viral disease.

Clinical presentation and management of severe Ebola virus disease

Clinicians caring for patients infected with Ebola virus must be familiar not only with screening and infection control measures but also with management of severe disease. By integrating experience from several Ebola epidemics with best practices for managing critical illness, this report focuses on the clinical presentation and management of severely ill infants, children, and adults with Ebola virus disease. Fever, fatigue, vomiting, diarrhea, and anorexia are the most common symptoms of the 2014 West African outbreak. Profound fluid losses from the gastrointestinal tract result in volume depletion, metabolic abnormalities (including hyponatremia, hypokalemia, and hypocalcemia), shock, and organ failure. Overt hemorrhage occurs infrequently. The case fatality rate in West Africa is at least 70%, and individuals with respiratory, neurological, or hemorrhagic symptoms have a higher risk of death. There is no proven antiviral agent to treat Ebola virus disease, although several experimental treatments may be considered. Even in the absence of antiviral therapies, intensive supportive care has the potential to markedly blunt the high case fatality rate reported to date. Optimal treatment requires conscientious correction of fluid and electrolyte losses. Additional management considerations include searching for coinfection or superinfection; treatment of shock (with intravenous fluids and vasoactive agents), acute kidney injury (with renal replacement therapy), and respiratory failure (with invasive mechanical ventilation); provision of nutrition support, pain and anxiety control, and psychosocial support; and the use of strategies to reduce complications of critical illness. Cardiopulmonary resuscitation may be appropriate in certain circumstances, but extracorporeal life support is not advised. Among other ethical issues, patients' medical needs must be carefully weighed against healthcare worker safety and infection control concerns. However, meticulous attention to the use of personal protective equipment and strict adherence to infection control protocols should permit the safe provision of intensive treatment to severely ill patients with Ebola virus disease.

Pathogens penetrating the central nervous system: infection pathways and the cellular and molecular mechanisms of invasion

The brain is well protected against microbial invasion by cellular barriers, such as the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). In addition, cells within the central nervous system (CNS) are capable of producing an immune response against invading pathogens. Nonetheless, a range of pathogenic microbes make their way to the CNS, and the resulting infections can cause significant morbidity and mortality. Bacteria, amoebae, fungi, and viruses are capable of CNS invasion, with the latter using axonal transport as a common route of infection. In this review, we compare the mechanisms by which bacterial pathogens reach the CNS and infect the brain. In particular, we focus on recent data regarding mechanisms of bacterial translocation from the nasal mucosa to the brain, which represents a little explored pathway of bacterial invasion but has been proposed as being particularly important in explaining how infection with Burkholderia pseudomallei can result in melioidosis encephalomyelitis.

Flaviviruses are neurotropic, but how do they invade the CNS?

Flaviruses (FV) are RNA viruses carried by mosquitoes. Neurological signs including acute encephalitis, meningitis and acute flaccid paralysis develop in a small percentage of infected individuals; long term sequlae are, Parkinsonism, dystonias and cognitive changes. FV neuroinfection is neurotropic involving subcortical nuclei (substantia nigra and thalamus) anterior horn neurons and neocortex. Glycosylation of the FV E envelope protein is one determinant of neuroinvasion, increasing both axonal and trans-epithelial transportation. Neutralizing antibodies against the E and NS proteins prevents FV uptake into several cell types, including axons. CD8+ T cells are vital for clearance of WNF infected cells from the CNS, whereas TLR-3 and TLR-7 mediated anti-virus response through increased serum inflammatory cytokines to disrupt the BBB providing infected leucocytes and free virus access to the CNS (so called Trojan horse) Cellular virus attachment factors, promoting FV cell entry are widely distributed and include DC-SIGN (that detects complex carbohydrate molecules); Glycosamino glycans (GAG), Heparan sulphate(HSPG) Semaphorin 7A, Low Density Lipid receptors (LDLR); these are not FV specific virus entry receptors. The FV also crosses epithelial and endothelial barriers by disrupting Tight Junction complexes to increase BBB permeability. This review describes the multiple pathways responsible for the neuroinvasive properties of the Flaviviruses.

Viruses and antiviral immunity in Drosophila

Viral pathogens present many challenges to organisms, driving the evolution of a myriad of antiviral strategies to combat infections. A wide variety of viruses infect invertebrates, including both natural pathogens that are insect-restricted, and viruses that are transmitted to vertebrates. Studies using the powerful tools in the model organism Drosophila have expanded our understanding of antiviral defenses against diverse viruses. In this review, we will cover three major areas. First, we will describe the tools used to study viruses in Drosophila. Second, we will survey the major viruses that have been studied in Drosophila. And lastly, we will discuss the well-characterized mechanisms that are active against these diverse pathogens, focusing on non-RNAi mediated antiviral mechanisms. Antiviral RNAi is discussed in another paper in this issue.

Seroprevalence of human enterovirus 71 and coxsackievirus A16 in Guangdong, China, in pre- and post-2010 HFMD epidemic period

BACKGROUND

Human Enterovirus 71 and Coxsackie A16 have caused many outbreaks in the last decade in mainland China, resulting in thousands of fatal cases. Seroepidemiology which provides important information to document population immunity is rare in China.

METHODOLOGY/PRINCIPAL FINDINGS

A cross sectional study of Enterovirus 71 (EV71) and Coxsackie A16 (CA16) seroprevalence was carried out in Guangdong, China, pre- and post- the 2010 hand, foot and mouth disease (HFMD) epidemic period. The levels of EV71 and CA16 specific antibodies were evaluated by a microneutralization test and the geometric mean titer (GMT) was calculated and compared. Our results indicated frequent infection by EV71 and CA16 in Guangdong before the 2010 epidemic. Only EV71 neutralizing antibody but not CA16 seroprevalence was significantly increased after the 2010 HFMD epidemic. Children less than 3 years old especially those aged 2 years showed the lowest positive rates for EV71 and CA16 NA before epidemic and the most significantly increased EV71 seroprevalence after epidemic. CA16 GMT values declined after the 2010 epidemic.

CONCLUSIONS

These results indicate EV71 was the major pathogen of HFMD in Guangdong during the 2010 epidemic. The infection occurs largely in children less than 3 years, who should have first priority to receive an EV71 vaccine.

Seroepidemiology of human enterovirus71 and coxsackievirusA16 among children in Guangdong province, China

Background

Hand, foot and mouth disease (HFMD) is a common pediatric illness. Mainly induced by the Enterovirus 71 and Coxsackievirus A 16 infections, the frequently occurred HFMD outbreaks have become a serious public health problem in Southeast Asia. Currently,only a few studies have investigated the human immunity to HFMD in China. In this study, we conducted a cohort study in Guangdong province, China.

Methods

Stored serum samples from children less than 10 years old were analyzed. The levels of EV71 and CA16 specific antibodies before, during and shortly after the 2008 large outbreak of HFMD were evaluated by the microneutralization test. The geometric mean titer (GMT) was calculated and compared. Statistical significance was taken as P < 0.05.

Results

The seroprevalence data showed a continuous circulation of EV71 and CA16 in Guangdong province China in 2007–2009. The low positive rate in 2009 correlated well with the unprecedented outbreak of HFMD in 2010. Age related increase of seroprevalence was identified in 1–3 years old children for EV71 and in 1–5 years old children for CA16 in Guangdong province. High GMT of EV71 and CA16 antibody titers were also found for these age groups.

Conclusions

All of the above findings indicated common infections for these age groups. And they should clearly be at the top of the priority in periodical seroprevalence survey and future vaccination campaign.

Intrathecal humoral immunity to encephalitic RNA viruses

The nervous system is the target for acute encephalitic viral infections, as well as a reservoir for persisting viruses. Intrathecal antibody (Ab) synthesis is well documented in humans afflicted by infections associated with neurological complications, as well as the demyelinating disease, multiple sclerosis. This review focuses on the origin, recruitment, maintenance, and biological relevance of Ab-secreting cells (ASC) found in the central nervous system (CNS) following experimental neurotropic RNA virus infections. We will summarize evidence for a highly dynamic, evolving humoral response characterized by temporal alterations in B cell subsets, proliferation, and differentiation. Overall local Ab plays a beneficial role via complement-independent control of virus replication, although cross or self-reactive Ab to CNS antigens may contribute to immune-mediated pathogenesis during some infections. Importantly, protective Ab exert anti-viral activity not only by direct neutralization, but also by binding to cell surface-expressed viral glycoproteins. Ab engagement of viral glycoproteins blocks budding and mediates intracellular signaling leading to restored homeostatic and innate functions. The sustained Ab production by local ASC, as well as chemokines and cytokines associated with ASC recruitment and retention, are highlighted as critical components of immune control.