Emerging viral infections of the central nervous system: part 2

Viral meningoencephalitis in pediatric solid organ or hematopoietic cell transplant recipients: a diagnostic and therapeutic approach

Neurologic complications, both infectious and non-infectious, are frequent among hematopoietic cell transplant (HCT) and solid organ transplant (SOT) recipients. Up to 46% of HCT and 50% of SOT recipients experience a neurological complication, including cerebrovascular accidents, drug toxicities, as well as infections. Defects in innate, adaptive, and humoral immune function among transplant recipients predispose to opportunistic infections, including central nervous system (CNS) disease. CNS infections remain uncommon overall amongst HCT and SOT recipients, compromising approximately 1% of total cases among adult patients. Given the relatively lower number of pediatric transplant recipients, the incidence of CNS disease amongst in this population remains unknown. Although infections comprise a small percentage of the neurological complications that occur post-transplant, the associated morbidity and mortality in an immunosuppressed state makes it imperative to promptly evaluate and aggressively treat a pediatric transplant patient with suspicion for viral meningoencephalitis. This manuscript guides the reader through a broad infectious and non-infectious diagnostic differential in a transplant recipient presenting with altered mentation and fever and thereafter, elaborates on diagnostics and management of viral meningoencephalitis. Hypothetical SOT and HCT patient cases have also been constructed to illustrate the diagnostic and management process in select viral etiologies. Given the unique risk for various opportunistic viral infections resulting in CNS disease among transplant recipients, the manuscript will provide a contemporary review of the epidemiology, risk factors, diagnosis, and management of viral meningoencephalitis in these patients.

Human Monkeypox-A Global Public Health Emergency

Monkeypox, a viral zoonosis caused by an Orthopoxvirus, is clinically characterized by fever, headache, lymphadenopathy, myalgia, rash and burdened by some complications that can be severe and life threatening. Monkeypox, endemic in some central and west African countries, in tropical areas near equator, rose to the headlines following its recent outbreak in non-endemic countries of Europe and the USA. Thus, the World Health Organization, worried about the growing dimension of the problem, declared monkeypox a global public health emergency. Now, after months of careful observation, the western scientific research is drawing conclusion that African endemic countries represent a reserve pool able to feed, through travelers and sexual networks, the outbreak in non-endemic countries in which high-risk communities such as gay and bisexual men are the most affected. Prevention through vaccination and early diagnosis are the core to breaking the chain of diffusion of this epidemic. Particular attention should be paid to avoid the spread from endemic countries, also implementing the economic investments in their public health system. Information campaigns and assistance to high-risk classes in non-endemic countries are important priorities, however, assuming that specific treatments for this disease are still tentative.

Monkeypox virus neurological manifestations in comparison to other orthopoxviruses

Viral infectious diseases have various neurological manifestations, whether they are epidemic or pandemic in nature. Nonspecific encephalopathy is the most common central nervous system (CNS) manifestation. The spectrum of nervous evidence varies for viral pathogens. Some infectious viruses, such as the Ebola virus, exhibit direct neurotropism. Others, such as the Rift Valley fever virus, have the potential for neurotropism. Direct neurotropism is unknown in monkeypox virus, SARS-CoV-2, MERS-CoV, and even smallpox. As seen in the COVID-19, there may be evidence of para-infectious neurological syndrome. There have only been a few reports of neurological diseases caused by monkeypox infection. Future efforts to prevent the spread of infectious disease surges can reduce mortality complications, the therapeutic burden on the health-care system, and prevent further spread. This study describes the clinical and neurological complications of monkeypox infection, particularly encephalitis, as well as the laboratory diagnosis of these cases.

Metagenomics for neurological infections - expanding our imagination

Over the past two decades, the diagnosis rate for patients with encephalitis has remained poor despite advances in pathogen-specific testing such as PCR and antigen assays. Metagenomic next-generation sequencing (mNGS) of RNA and DNA extracted from cerebrospinal fluid and brain tissue now offers another strategy for diagnosing neurological infections. Given that mNGS simultaneously assays for a wide range of infectious agents in an unbiased manner, it can identify pathogens that were not part of a neurologist’s initial differential diagnosis either because of the rarity of the infection, because the microorganism has not been previously associated with a clinical phenotype or because it is a newly discovered organism. This Review discusses the technical advantages and pitfalls of cerebrospinal fluid mNGS in the context of patients with neuroinflammatory syndromes, including encephalitis, meningitis and myelitis. We also speculate on how mNGS testing potentially fits into current diagnostic testing algorithms given data on mNGS test performance, cost and turnaround time. Finally, the Review highlights future directions for mNGS technology and other hypothesis-free testing methodologies that are in development.

This Review discusses the advantages and pitfalls of metagenomic next-generation sequencing (mNGS) in patients with encephalitis, meningitis and myelitis. The authors outline data on mNGS test performance, cost and turnaround time and highlight future directions for mNGS technology.

Meningoencephalitis remains a challenging diagnosis owing to the multitude of possible infectious and autoimmune causes.

Meningoencephalitis is associated with a high rate of morbidity and mortality and requires prompt diagnosis and treatment.

Metagenomic next-generation sequencing (mNGS) is now a clinically validated test for neuroinfectious diseases that can aid clinicians with a timely diagnosis.

mNGS can improve the detection of pathogens that were missed by clinicians or on standard direct testing.

mNGS does not perform well when indirect tests are required to make the diagnosis (for example, serology), when infections are compartmentalized and for certain low abundance pathogens.

The clinical context of the case is required when interpreting the results of mNGS.

An improved animal model for herpesvirus encephalitis in humans

Herpesviral encephalitis caused by Herpes Simplex Virus 1 (HSV-1) is one of the most devastating diseases in humans. Patients present with fever, mental status changes or seizures and when untreated, sequelae can be fatal. Herpes Simplex Encephalitis (HSE) is characterized by mainly unilateral necrotizing inflammation effacing the frontal and mesiotemporal lobes with rare involvement of the brainstem. HSV-1 is hypothesized to invade the CNS via the trigeminal or olfactory nerve, but viral tropism and the exact route of infection remain unclear. Several mouse models for HSE have been developed, but they mimic natural infection only inadequately. The porcine alphaherpesvirus Pseudorabies virus (PrV) is closely related to HSV-1 and Varicella Zoster Virus (VZV). While pigs can control productive infection, it is lethal in other susceptible animals associated with severe pruritus leading to automutilation. Here, we describe the first mutant PrV establishing productive infection in mice that the animals are able to control. After intranasal inoculation with a PrV mutant lacking tegument protein pUL21 and pUS3 kinase activity (PrV-ΔUL21/US3Δkin), nearly all mice survived despite extensive infection of the central nervous system. Neuroinvasion mainly occurred along the trigeminal pathway. Whereas trigeminal first and second order neurons and autonomic ganglia were positive early after intranasal infection, PrV-specific antigen was mainly detectable in the frontal, mesiotemporal and parietal lobes at later times, accompanied by a long lasting lymphohistiocytic meningoencephalitis. Despite this extensive infection, mice showed only mild to moderate clinical signs, developed alopecic skin lesions, or remained asymptomatic. Interestingly, most mice exhibited abnormalities in behavior and activity levels including slow movements, akinesia and stargazing. In summary, clinical signs, distribution of viral antigen and inflammatory pattern show striking analogies to human encephalitis caused by HSV-1 or VZV not observed in other animal models of disease.

In developed countries, more than 50% of humans are seropositive for the neurotropic Herpes Simplex Virus 1 (HSV-1) and two to four million cases of Herpes simplex encephalitis (HSE) are reported per year worldwide. Primary infection with HSV-1 takes place via the skin or the oral mucosa followed by intraaxonal retrograde spread to sensory ganglia of the peripheral nervous system where HSV-1 usually establishes latency. Further spread to the central nervous system results in HSE, a necrotizing encephalitis effacing predominantly the temporal and frontal lobes of the brain. Mice infected with HSV-1 develop encephalitis, but do not show the typical lesions and exhibit high mortality rates. Here we demonstrate that mice infected with a mutant pseudorabies virus lacking the tegument protein pUL21 and an active viral kinase pUS3 were able to survive the productive infection but developed lymphohistiocytic encephalitis with viral antigen distribution, inflammation and associated behavioral changes comparable to HSE in humans. These striking analogies offer new perspectives to study herpesviral encephalitis in a suitable animal model.

Emerging Infectious Diseases

Emerging infectious diseases (EIDs) including novel avian influenza viruses or even recently reported Zika virus (ZIKV) have drawn great attentions globally. The application of modern diagnostic technologies is expected to increase. Imaging plays a key role on diagnosis and prognosis assessment in patients with EID.

Adult Mouse DRG Explant and Dissociated Cell Models to Investigate Neuroplasticity and Responses to Environmental Insults Including Viral Infection

This protocol describes an ex vivo model of mouse-derived dorsal root ganglia (DRG) explant and in vitro DRG-derived co-culture of dissociated sensory neurons and glial satellite cells. These are useful and versatile models to investigate a variety of biological responses associated with physiological and pathological conditions of the peripheral nervous system (PNS) ranging from neuron-glial interaction, neuroplasticity, neuroinflammation, and viral infection. The usage of DRG explant is scientifically advantageous compared to simplistic single cells models for multiple reasons. For instance, as an organotypic culture, the DRG explant allows ex vivo transfer of an entire neuronal network including the extracellular microenvironment that play a significant role in all the neuronal and glial functions. Further, DRG explants can also be maintained ex vivo for several days and the culture conditions can be perturbed as desired. In addition, the harvested DRG can be further dissociated into an in vitro co-culture of primary sensory neurons and satellite glial cells to investigate neuronal-glial interaction, neuritogenesis, axonal cone interaction with the extracellular microenvironment, and more general, any aspect associated with the neuronal metabolism. Therefore, the DRG-explant system offers a great deal of flexibility to study a wide array of events related to biological, physiological, and pathological conditions in a cost-effective manner.

Efficient propagation of archetype JC polyomavirus in COS-7 cells: evaluation of rearrangements within the NCCR structural organization after transfection

John Cunningham virus (JCPyV) is an ubiquitous human pathogen that causes disease in immunocompromised patients. The JCPyV genome is composed of an early region and a late region, which are physically separated by the non-coding control region (NCCR). The DNA sequence of the NCCR distinguishes two forms of JCPyV, the designated archetype and the prototype, which resulted from a rearrangement of the archetype sequence. To date, the cell culture systems for propagating JCPyV archetype have been very limited in their availability and robustness. Prior to this study, it was demonstrated that JCPyV archetype DNA replicates in COS-7 simian kidney cells expressing SV40 TAg and COS-7 cells expressing HIV-1 Tat. Based on these observations, the present study was conducted to reproduce an in vitro model in COS-7 cells transfected with the JCPyV archetype strain in order to study JCPyV DNA replication and analyze NCCR rearrangements during the viral life cycle. The efficiency of JCPyV replication was evaluated by quantitative PCR (Q-PCR) and by hemagglutination (HA) assay after transfection. In parallel, sequence analysis of JCPyV NCCR was performed. JCPyV efficiently replicated in kidney-derived COS-7 cells, as demonstrated by a progressive increase in viral load and virion particle production after transfection. The archetypal structure of NCCR was maintained during the viral cycle, but two characteristic point mutations were detected 28 days after transfection. This model is a useful tool for analyzing NCCR rearrangements during in vitro replication in cells that are sites of viral persistence, such as tubular epithelial cells of the kidney.

Epidemiology of infectious encephalitis causes in 2016

We performed a literature search in the Medline database, using the PubMed website. The incidence of presumably infectious encephalitis is estimated at 1.5-7 cases/100,000 inhabitants/year, excluding epidemics. Infectious encephalitis and immune-mediated encephalitis share similar clinical signs and symptoms. The latter accounts for a significant proportion of presumably infectious encephalitis cases without any established etiological diagnosis; as shown from a prospective cohort study where 21% of cases were due to an immune cause. Several infectious agents are frequently reported in all studies: Herpes simplex virus (HSV) is the most frequent pathogen in 65% of studies, followed by Varicella-zoster virus (VZV) in several studies. Enteroviruses are also reported; being the most frequent viruses in two studies, and the 2nd or 3rd viruses in five other studies. There are important regional differences, especially in case of vector-borne transmission: Asia and the Japanese encephalitis virus, Eastern and Northern Europe/Eastern Russia and the tick-borne encephalitis virus, Northern America and Flavivirus or Alphavirus. Bacteria can also be incriminated: Mycobacterium tuberculosis and Listeria monocytogenes are the most frequent, after HSV and VZV, in a French prospective study. The epidemiology of encephalitis is constantly evolving. Epidemiological data may indicate the emergence and/or dissemination of new causative agents. The dissemination and emergence of causative agents are fostered by environmental, social, and economical changes, but prevention programs (vaccination, vector controls) help reduce the incidence of other infectious diseases and associated encephalitis (e.g., measles).

The Multifactorial Background of Emerging Viral Infections with Neurological Manifestation

The events of the past year have highlighted the continuing importance of emerging virus infections on the diagnosis and treatment of neurological disease. This review focusses on clarifying the effects of the multiple overlapping factors that impact emergence, including viral richness, transmission opportunity, and establishment. Case studies of the West Nile, chikungunya, and Zika viruses are utilised to illustrate the dramatic effects of expansion in the range and geographical distribution of emerging infectious disease, the acquisition of new virus vectors, and of increasing human anthropogenic factors such as global transport, climate change, and mosquito abatement programmes on the regional spread and clinical consequences of emerging infectious disease.

Therapeutic antiviral T cells noncytopathically clear persistently infected microglia after conversion into antigen-presenting cells

Clearance of neurotropic infections is challenging because the CNS is relatively intolerant of immunopathological reactions. Herz et al. use a model of persistent viral infection in mice to demonstrate therapeutic antiviral T cells can purge the CNS infection without causing tissue damage resulting from limited recruitment of inflammatory innate immune cells and conversion of microglia into APCs.

Several viruses can infect the mammalian nervous system and induce neurological dysfunction. Adoptive immunotherapy is an approach that involves administration of antiviral T cells and has shown promise in clinical studies for the treatment of peripheral virus infections in humans such as cytomegalovirus (CMV), Epstein-Barr virus (EBV), and adenovirus, among others. In contrast, clearance of neurotropic infections is particularly challenging because the central nervous system (CNS) is relatively intolerant of immunopathological reactions. Therefore, it is essential to develop and mechanistically understand therapies that noncytopathically eradicate pathogens from the CNS. Here, we used mice persistently infected from birth with lymphocytic choriomeningitis virus (LCMV) to demonstrate that therapeutic antiviral T cells can completely purge the persistently infected brain without causing blood–brain barrier breakdown or tissue damage. Mechanistically, this is accomplished through a tailored release of chemoattractants that recruit antiviral T cells, but few pathogenic innate immune cells such as neutrophils and inflammatory monocytes. Upon arrival, T cells enlisted the support of nearly all brain-resident myeloid cells (microglia) by inducing proliferation and converting them into CD11c⁺ antigen-presenting cells (APCs). Two-photon imaging experiments revealed that antiviral CD8⁺ and CD4⁺ T cells interacted directly with CD11c⁺ microglia and induced STAT1 signaling but did not initiate programmed cell death. We propose that noncytopathic CNS viral clearance can be achieved by therapeutic antiviral T cells reliant on restricted chemoattractant production and interactions with apoptosis-resistant microglia.

Detailed analysis of the African green monkey model of Nipah virus disease

Henipaviruses are implicated in severe and frequently fatal pneumonia and encephalitis in humans. There are no approved vaccines or treatments available for human use, and testing of candidates requires the use of well-characterized animal models that mimic human disease. We performed a comprehensive and statistically-powered evaluation of the African green monkey model to define parameters critical to disease progression and the extent to which they correlate with human disease. African green monkeys were inoculated by the intratracheal route with 2.5 × 10(4) plaque forming units of the Malaysia strain of Nipah virus. Physiological data captured using telemetry implants and assessed in conjunction with clinical pathology were consistent with shock, and histopathology confirmed widespread tissue involvement associated with systemic vasculitis in animals that succumbed to acute disease. In addition, relapse encephalitis was identified in 100% of animals that survived beyond the acute disease phase. Our data suggest that disease progression in the African green monkey is comparable to the variable outcome of Nipah virus infection in humans.

A Review of Hendra Virus and Nipah Virus Infections in Man and Other Animals

Hendra virus (HeV) and Nipah virus (NiV) emerged in the last decade of the twentieth century. They were the cause of a number of outbreaks of respiratory and neurological disease infecting horses and pigs respectively. Transmission from infected domestic animal species resulted in human infections as well, with high case fatality rates a feature. Today they continue to cause outbreaks of human and animal disease. NiV causes yearly disease outbreaks in humans in Bangladesh, and HeV causes sporadic disease outbreaks in horses in north eastern Australia. Due to their zoonotic nature, they have been ideal candidates for collaborative projects in the One Health space, bringing public health and animal health professionals together. This has lead to insightful epidemiological studies, which has resulted in practical disease prevention solutions including a horse vaccine for HeV and NiV spill-over prevention interventions in the field. As more surveillance is undertaken, their known distributions have expanded, as has the range of reservoir host species. The majority of bat species for which there is evidence of henipavirus infection belong to the group known as the Old World family of fruit and nectar feeding bats (Family Pteropodidae, Suborder Megachiroptera). This review of the bat borne henipaviruses discusses the epidemiology, pathology, transmission and disease symptoms in these closely related viruses which belong to the Genus Henipavirus, Family Paramyxoviridae.

Novel approaches and challenges to treatment of central nervous system viral infections

Existing and emerging viral central nervous system (CNS) infections are major sources of human morbidity and mortality. Treatments of proven efficacy are currently limited predominantly to herpesviruses and human immunodeficiency virus (HIV). Development of new therapies has been hampered by the lack of appropriate animal model systems for some important viruses and by the difficulty in conducting human clinical trials for diseases that may be rare, or in the case of arboviral infections, often have variable seasonal and geographic incidence. Nonetheless, many novel approaches to antiviral therapy are available, including candidate thiazolide and pyrazinecarboxamide derivatives with potential broad‐spectrum antiviral efficacy. New herpesvirus drugs include viral helicase‐primase and terminase inhibitors. The use of antisense oligonucleotides and other strategies to interfere with viral RNA translation has shown efficacy in experimental models of CNS viral disease. Identifying specific molecular targets within viral replication cycles has led to many existing antiviral agents and will undoubtedly continue to be the basis of future drug design. A promising new area of research involves therapies based on enhanced understanding of host antiviral immune responses. Toll‐like receptor agonists and drugs that inhibit specific cytokines as well as interferon preparations have all shown potential therapeutic efficacy. Passive transfer of virus‐specific cytotoxic T lymphocytes has been used in humans and may provide an effective therapy for some herpesvirus infections and potentially for progressive multifocal leukoencephalopathy. Humanized monoclonal antibodies directed against specific viral proteins have been developed and in several cases evaluated in humans in settings including West Nile virus and HIV infection and in pre‐exposure prophylaxis for rabies. Ann Neurol 2013;74:412–422

Consensus guidelines on evaluation and management of suspected acute viral encephalitis in children in India

JUSTIFICATION

Viral encephalitis is an important cause of mortality and morbidity in children. The etiological agents are varied, and physicians treating such children often feel limited by the lack of uniform guidelines on evaluation and management of these critically ill children in resource-constrained settings.

PROCESS

An Expert Group Meeting on Viral Encephalitis in Children was held on 19th January, 2012 in Gurgaon, Haryana (under the aegis of PEDICON 2012, the National Conference of Indian Academy of Pediatrics). The invited experts included pediatricians and microbiologists with expertise in the relevant field. Various issues related to the subject were discussed and it was decided to bring out recommendations on the topic. The final recommendations were produced after circulating the draft document, and incorporating/discussing all changes, by email.

OBJECTIVES

To aid the pediatrician in the evaluation and management of children with suspected viral encephalitis and to assist the public health authorities in acute encephalitis surveillance. These guidelines do not cover viral encephalitis in the neonatal period and in immunocompromised children, Rabies encephalitis, and chronic viral encephalitis such as Subacute sclerosing panencephalitis (SSPE).

RECOMMENDATIONS

Recommendation for evaluation and management of suspected viral encephalitis in children are presented. In any acute encephalitis outbreak, pediatricians should be aware of the common viral causes of encephalitis in their area, what information and samples they should collect, and the contact details of the District Surveillance Unit. Pending specific diagnosis and therapy (which may or may not be possible), prompt empirical therapy and meticulous supportive care are important to prevent ongoing brain damage, and improve outcome.

New insights on human polyomavirus JC and pathogenesis of progressive multifocal leukoencephalopathy

John Cunningham virus (JCV) is a member of the Polyomaviridae family. It was first isolated from the brain of a patient with Hodgkin disease in 1971, and since then the etiological agent of the progressive multifocal leukoencephalopathy (PML) was considered. Until the human immunodeficiency virus (HIV) pandemic, PML was rare: in fact HIV-induced immunodeficiency is the most common predisposing factor accounting for 85% of all instances of PML. This data led to intense research on JCV infection and resulted in better understanding of epidemiology and clinic-pathologic spectrum. Recently, cases of PML have been observed after the introduction of monoclonal antibodies, such as natalizumab, rituximab, efalizumab, and infliximab, in the treatment of autoimmune disease, underlining the important role of host immunity in PML pathogenesis. In this review current understanding of the JCV infection and the new findings relating to the pathogenesis of PML has been comprehensively revised, focusing our attention on the interaction between the cellular and viral molecular pathways implicated in the JCV infection and the modulating role of host immune surveillance in the viral reactivation from a latent state.

The yield of temporary exclusion of blood donors, exposed to emerging infections abroad

BACKGROUND AND OBJECTIVES

Emerging infections abroad pose a threat to the safety of blood, donated by travelling blood donors. In this study, the yield of donor deferral after travelling was evaluated, by comparing the estimated numbers of infected donors returning from various affected areas.

METHODS

A deterministic model was applied to calculate the number of infected donors, returning from six areas affected by outbreaks: Greece - Macedonia (West Nile fever), Italy - Emilia Romagna (West Nile fever), Thailand (chikungunya), Latvia (hepatitis A), central Turkey (Sicilian sandfly fever) and Italy - Tuscany (Toscana sandfly fever).

RESULTS

The estimated number of infections among returning blood donors was surprisingly low, ranging from 0·32 West Nile virus-infected donors per year returning from Macedonia (Greece) to approximately 0·005 infected donors per year returning respectively from Tuscany (sandfly fever), Latvia (hepatitis A) and central Turkey (sandfly fever).

CONCLUSION

The yield of the temporary exclusion of blood donors travelling to a specific, affected area is low, but the continuous monitoring of emerging infections and the timely assessment of new threats are laborious and imperfect. Safety measures may be instituted after the greatest threat of a new outbreak has passed. A general deferral of travelling donors may be more appropriate than targeted measures. It can be argued that all donors who stayed outside their country or continent of residency should be deferred for 4 weeks.

Stroke mimics

Stroke mimics are an important consideration for emergency physicians and physician extenders working in emergency departments. The emergency medicine physician must determine whether the acute neurologic deficits represent a transient event or a potential stroke. This article describes the common stroke mimic presentations by cause, including toxic-metabolic pathologies, seizure disorders, degenerative neurologic conditions, and peripheral neuropathies.

Viral CNS infections: role of glial pattern recognition receptors in neuroinflammation

Viruses are the major causative agents of central nervous system (CNS) infection worldwide. RNA and DNA viruses trigger broad activation of glial cells including microglia and astrocytes, eliciting the release of an array of mediators that can promote innate and adaptive immune responses. Such responses can limit viral replication and dissemination leading to infection resolution. However, a defining feature of viral CNS infection is the rapid onset of severe neuroinflammation and overzealous glial responses are associated with significant neurological damage or even death. The mechanisms by which microglia and astrocytes perceive neurotropic RNA and DNA viruses are only now becoming apparent with the discovery of a variety of cell surface and cytosolic molecules that serve as sensors for viral components. In this review we discuss the role played by members of the Toll-like family of pattern recognition receptors (PRRs) in the inflammatory responses of glial cells to the principle causative agents of viral encephalitis. Importantly, we also describe the evidence for the involvement of a number of newly described intracellular PRRs, including retinoic acid-inducible gene I and DNA-dependent activator of IFN regulatory factors, that are thought to function as intracellular sensors of RNA and DNA viruses, respectively. Finally, we explore the possibility that cross-talk exists between these disparate viral sensors and their signaling pathways, and describe how glial cytosolic and cell surface/endosomal PRRs could act in a cooperative manner to promote the fulminant inflammation associated with acute neurotropic viral infection.

Infektionen

Trotz Weiterentwicklung moderner Antibiotika in den letzten Jahren sind die Letalitätszahlen der bakteriellen (eitrigen) Meningitis weiterhin hoch; Überlebende haben häufig neurologische Residuen. Die ungünstigen klinischen Verläufe der bakteriellen Meningitis sind meist Folge intrakranieller Komplikationen, wie z. B. eines generalisierten Hirnödems, einer zerebrovaskulären arteriellen oder venösen Beteiligung oder eines Hydrozephalus.

Infectious causes of seizures and epilepsy in the developing world

Central nervous system (CNS) infections are the main cause of seizures and acquired epilepsy in the developing world. Geographical variations determine the common causes in a particular region. Acute seizures are common in severe meningitis, viral encephalitis, malaria, and neurocysticercosis, and in most cases are associated with increased mortality and morbidity, including subsequent epilepsy. Neuronal excitability secondary to proinflammatory signals induced by CNS infections are an important common mechanism for the generation of seizures, in addition to various other specific mechanisms. Newer insights into the neurobiology of these infections and the associated epilepsy could help in developing neuroprotective interventions. Management issues include prompt treatment of acute seizures and the underlying CNS infection, correction of associated predisposing factors, and decisions regarding the appropriate choice and duration of antiepileptic therapy. Strategies for the prevention of epilepsy in CNS infections such as early anti-infective and anti-inflammatory therapy need scientific exploration. Prevention of CNS infections is the only definitive way forward to reduce the burden of epilepsy in developing countries.

Illuminating viral infections in the nervous system

Viral infections are a major cause of human disease. Although most viruses replicate in peripheral tissues, some have developed unique strategies to move into the nervous system, where they establish acute or persistent infections. Viral infections in the central nervous system (CNS) can alter homeostasis, induce neurological dysfunction and result in serious, potentially life-threatening inflammatory diseases. This Review focuses on the strategies used by neurotropic viruses to cross the barrier systems of the CNS and on how the immune system detects and responds to viral infections in the CNS. A special emphasis is placed on immune surveillance of persistent and latent viral infections and on recent insights gained from imaging both protective and pathogenic antiviral immune responses.

Hendra and nipah infection: pathology, models and potential therapies

The Paramyxoviridae family comprises of several genera that contain emerging or re-emerging threats for human and animal health with no real specific effective treatment available. Hendra and Nipah virus are members of a newly identified genus of emerging paramyxoviruses, Henipavirus. Since their discovery in the 1990s, henipaviruses outbreaks have been associated with high economic and public health threat potential. When compared to other paramyxoviruses, henipaviruses appear to have unique characteristics. Henipaviruses are zoonotic paramyxoviruses with a broader tropism than most other paramyxoviruses, and can cause severe acute encephalitis with unique features among viral encephalitides. There are currently no approved effective prophylactic or therapeutic treatments for henipavirus infections. Although ribavirin was empirically used and seemed beneficial during the biggest outbreak caused by one of these viruses, the Nipah virus, its efficacy is disputed in light of its lack of efficacy in several animal models of henipavirus infection. Nevertheless, because of its highly pathogenic nature, much effort has been spent in developing anti-henipavirus therapeutics. In this review we describe the unique features of henipavirus infections and the different strategies and animal models that have been developed so far in order to identify and test potential drugs to prevent or treat henipavirus infections. Some of these components have the potential to be broad-spectrum antivirals as they target effectors of viral pathogenecity common to other viruses. We will focus on small molecules or biologics, rather than vaccine strategies, that have been developed as anti-henipaviral therapeutics.

Headaches attributable to infectious diseases

Headache is the most common symptom that humans experience. While the vast majority of headaches are due to benign primary headache disorders, a small but important minority of headaches are due to secondary causes. Whereas significant emphasis is placed on educating physicians regarding prompt recognition of subarachnoid hemorrhage and headaches secondary to brain tumors, attention toward headaches secondary to infectious causes is often neglected. Unfortunately, a missed or delayed diagnosis of a headache secondary to meningitis, encephalitis, brain abscess, subdural empyema, or other infectious etiologies can lead to dire consequences for both the patient and physician. Accordingly, this article provides an overview of headaches attributed to systemic and intracranial infectious causes.

Non-heat related impacts of climate change on working populations

Environmental and social changes associated with climate change are likely to have impacts on the well-being, health, and productivity of many working populations across the globe. The ramifications of climate change for working populations are not restricted to increases in heat exposure. Other significant risks to worker health (including physical hazards from extreme weather events, infectious diseases, under-nutrition, and mental stresses) may be amplified by future climate change, and these may have substantial impacts at all scales of economic activity. Some of these risks are difficult to quantify, but pose a substantial threat to the viability and sustainability of some working populations. These impacts may occur in both developed and developing countries, although the latter category is likely to bear the heaviest burden.This paper explores some of the likely, non-heat-related health issues that climate change will have on working populations around the globe, now and in the future. These include exposures to various infectious diseases (vector-borne, zoonotic, and person-to-person), extreme weather events, stress and mental health issues, and malnutrition.

JC virus infection of the brain

Since its initial description, there have been significant changes in the epidemiology, pathogenesis, and clinical and imaging manifestations of JCV infection of brain. The most common clinical manifestation is PML. Other recently described CNS manifestations are JCE, JCVGCN, and JCM. Although AIDS is the most common predisposing factor for JCV reactivation, there is increasing incidence of brain manifestations of JCV reactivation in non-HIV settings, including different rheumatologic, hematologic, and oncologic conditions; monoclonal antibody therapy; transplant recipients; primary immunodeficiency syndromes; and even in patients without any recognizable immune deficiency. IRIS may develop secondary to restoration of immunity in HIV-positive patients with PML receiving antiretroviral therapy. This is of profound clinical significance and needs to be diagnosed promptly. Imaging plays a crucial role in the diagnosis of the disease, monitoring of treatment response, identifying disease progression, and predicting prognosis. In this article, current understanding of the epidemiology, pathogenesis, clinical presentations, and all aspects of imaging of JCV infection of the brain have been comprehensively reviewed.

Astrovirus encephalitis in boy with X-linked agammaglobulinemia

Encephalitis is a major cause of death worldwide. Although >100 pathogens have been identified as causative agents, the pathogen is not determined for up to 75% of cases. This diagnostic failure impedes effective treatment and underscores the need for better tools and new approaches for detecting novel pathogens or determining new manifestations of known pathogens. Although astroviruses are commonly associated with gastroenteritis, they have not been associated with central nervous system disease. Using unbiased pyrosequencing, we detected an astrovirus as the causative agent for encephalitis in a 15-year-old boy with agammaglobulinemia; several laboratories had failed to identify the agent. Our findings expand the spectrum of causative agents associated with encephalitis and highlight unbiased molecular technology as a valuable tool for differential diagnosis of unexplained disease.

Advances in pediatric neurovirology

Viral infections of the pediatric central nervous system (CNS) encompass a broad spectrum of both perinatally and postnatally acquired diseases with potentially devastating effects on the developing brain. In children, viral infections have been associated with chronic encephalopathy, encephalitis, demyelinating disease, tumors, and epilepsy. Older diagnostic techniques of biopsy, viral culture, electron microscopy, gel-based polymerase chain reaction (PCR), and viral titer quantification are being replaced with more rapid, sensitive, and specific real-time and microarray-based PCR technologies. Advances in neuroimaging technologies have provided for earlier recognition of CNS injury without elucidation of specific viral etiology. Although the mainstay therapy of many pediatric neurovirologic diseases, aside from HIV, includes intravenous acyclovir, much work is being done to develop novel antiviral immunotherapies aimed at both treating and preventing pediatric CNS viral disease.

[Acute viral and emerging viral CNS infections]

The morbidity and mortality of viral CNS infections can be reduced through early initiation of therapy, which could be specific or in most cases symptomatic. This in turn requires the physician to consider meningoencephalitis as a differential diagnosis.Increasing climate changes, global air travel and changing immune responses contribute to the emergence of rather rare viral pathogens on our continent. Thus, neurologists in Europe are facing an enormous challenge due to lacking knowledge and experience of these new germs, which needs to be taken care of.Novel therapeutic approaches with e.g. monoclonal antibodies awaken the hope of mitigating the partially lethal courses of these diseases.