Treatment of severe La Crosse encephalitis with intravenous ribavirin following diagnosis by brain biopsy

Identification of age-specific gene regulators of La Crosse virus neuroinvasion and pathogenesis

One of the key events in viral encephalitis is the ability of virus to enter the central nervous system (CNS). Several encephalitic viruses, including La Crosse Virus (LACV), primarily induce encephalitis in children, but not adults. This phenomenon is also observed in LACV mouse models, where the virus gains access to the CNS of weanling animals through vascular leakage of brain microvessels, likely through brain capillary endothelial cells (BCECs). To examine age and region-specific regulatory factors of vascular leakage, we used genome-wide transcriptomics and targeted siRNA screening to identify genes whose suppression affected viral pathogenesis in BCECs. Further analysis of two of these gene products, Connexin43 (Cx43/Gja1) and EphrinA2 (Efna2), showed a substantial effect on LACV pathogenesis. Induction of Cx43 by 4-phenylbutyric acid (4-PBA) inhibited neurological disease in weanling mice, while Efna2 deficiency increased disease in adult mice. Thus, we show that Efna2 and Cx43 expressed by BCECs are key mediators of LACV-induced neuroinvasion and neurological disease.

Age influences susceptibility of brain capillary endothelial cells to La Crosse virus infection and cell death

Background

A key factor in the development of viral encephalitis is a virus crossing the blood-brain barrier (BBB). We have previously shown that age-related susceptibility of mice to the La Crosse virus (LACV), the leading cause of pediatric arbovirus encephalitis in the USA, was associated with the ability of the virus to cross the BBB. LACV infection in weanling mice (aged around 3 weeks) results in vascular leakage in the olfactory bulb/tract (OB/OT) region of the brain, which is not observed in adult mice aged > 6–8 weeks. Thus, we studied age-specific differences in the response of brain capillary endothelial cells (BCECs) to LACV infection.

Methods

To examine mechanisms of LACV-induced BBB breakdown and infection of the CNS, we analyzed BCECs directly isolated from weanling and adult mice as well as established a model where these cells were infected in vitro and cultured for a short period to determine susceptibility to virus infection and cell death. Additionally, we utilized correlative light electron microscopy (CLEM) to examine whether changes in cell morphology and function were also observed in BCECs in vivo.

Results

BCECs from weanling, but not adult mice, had detectable infection after several days in culture when taken ex vivo from infected mice suggesting that these cells could be infected in vitro. Further analysis of BCECs from uninfected mice, infected in vitro, showed that weanling BCECs were more susceptible to virus infection than adult BCECs, with higher levels of infected cells, released virus as well as cytopathic effects (CPE) and cell death. Although direct LACV infection is not detected in the weanling BCECs, CLEM analysis of brain tissue from weanling mice indicated that LACV infection induced significant cerebrovascular damage which allowed virus-sized particles to enter the brain parenchyma.

Conclusions

These findings indicate that BCECs isolated from adult and weanling mice have differential viral load, infectivity, and susceptibility to LACV. These age-related differences in susceptibility may strongly influence LACV-induced BBB leakage and neurovascular damage allowing virus invasion of the CNS and the development of neurological disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02173-4.

Modeling SARS-CoV-2 infection in individuals with opioid use disorder with brain organoids

The COVID-19 pandemic has aggravated a preexisting epidemic: the opioid crisis. Much literature has shown that the circumstances imposed by COVID-19, such as social distancing regulations, medical and financial instability, and increased mental health issues, have been detrimental to those with opioid use disorder (OUD). In addition, unexpected neurological sequelae in COVID-19 patients suggest that COVID-19 compromises neuroimmunity, induces hypoxia, and causes respiratory depression, provoking similar effects as those caused by opioid exposure. Combined conditions of COVID-19 and OUD could lead to exacerbated complications. With limited human in vivo options to study these complications, we suggest that iPSC-derived brain organoid models may serve as a useful platform to investigate the physiological connection between COVID-19 and OUD. This mini-review highlights the advances of brain organoids in other neuropsychiatric and infectious diseases and suggests their potential utility for investigating OUD and COVID-19, respectively.

Ribavirin inhibits Chandipura virus replication in Vero cells

Chandipura virus (CHPV) is an emerging tropical pathogen in India. The virus has been reported to be associated with an acute encephalitis syndrome in young children with a case fatality rate of 55% to 75%. Clinical management with symptomatic treatment is the only option available to treat infected patients. No vaccines are available for prophylaxis. In light of the prophylactic limitations, antiviral therapy would play an important role in control of CHPV infection. In the present study, ribavirin (RBV), an antiviral drug widely accepted for human use and having an antiviral effect on many RNA and DNA viruses, was tested against the CHPV. A screening assay that scores for the virus-mediated plaque formation in the cultured Vero cells was used. RBV exhibited 50% inhibitory concentration (IC50 ) at 89.84 ± 1.8 µM. The drug was very effective when the cells were treated either within an hour postinfection or 4 to 6 hours before infection. The plaque morphology was different in RBV treated cells; the plaques were smaller in size as compared with the plaques in the virus infected cells. The study reports the antiviral activity of RBV against CHPV, and hence, suggests the possible utility of RBV in CHPV infected patients to mitigate the disease. A further clinical trial is needed before introducing the drug for human use against CHPV infection.

Emerging orthobunyaviruses associated with CNS disease

The Orthobunyavirus genus comprises a wide range of arthropod-borne viruses which are prevalent worldwide and commonly associated with central nervous system (CNS) disease in humans and other vertebrates. Several orthobunyaviruses have recently emerged and increasingly more will likely do so in the future. Despite this large number, an overview of these viruses is currently lacking, making it challenging to determine importance from a One Health perspective. Causality is a key feature of determining importance, yet classical tools are unfit to evaluate the causality of orthobunyaviral CNS disease. Therefore, we aimed to provide an overview of orthobunyaviral CNS disease in vertebrates and objectify the causality strength of each virus. In total, we identified 27 orthobunyaviruses described in literature to be associated with CNS disease. Ten were associated with disease in multiple host species of which seven included humans. Seven viruses were associated with both congenital and postnatal CNS disease. CNS disease-associated orthobunyaviruses were spread across all known Orthobunyavirus serogroups by phylogenetic analyses. Taken together, these results indicate that orthobunyaviruses may have a common tendency to infect the CNS of vertebrates. Next, we developed six tailor-made causality indicators and evaluated the causality strength of each of the identified orthobunyaviruses. Nine viruses had a 'strong' causality score and were deemed causal. Eight had a 'moderate' and ten a 'weak' causality score. Notably, there was a lack of case-control studies, which was only available for one virus. We, therefore, stress the importance of proper case-control studies as a fundamental aspect of proving causality. This comprehensible overview can be used to identify orthobunyaviruses which may be considered causal, reveal research gaps for viruses with moderate to low causality scores, and provide a framework to evaluate the causality of orthobunyaviruses that may newly emerge in the future.

Beneficial and Detrimental Effects of Regulatory T Cells in Neurotropic Virus Infections

Neurotropic viruses infect the central nervous system (CNS) and cause acute or chronic neurologic disabilities. Regulatory T cells (Treg) play a critical role for immune homeostasis, but may inhibit pathogen-specific immunity in infectious disorders. The present review summarizes the current knowledge about Treg in human CNS infections and their animal models. Besides dampening pathogen-induced immunopathology, Treg have the ability to facilitate protective responses by supporting effector T cell trafficking to the infection site and the development of resident memory T cells. Moreover, Treg can reduce virus replication by inducing apoptosis of infected macrophages and attenuate neurotoxic astrogliosis and pro-inflammatory microglial responses. By contrast, detrimental effects of Treg are caused by suppression of antiviral immunity, allowing for virus persistence and latency. Opposing disease outcomes following Treg manipulation in different models might be attributed to differences in technique and timing of intervention, infection route, genetic background, and the host’s age. In addition, mouse models of virus-induced demyelination revealed that Treg are able to reduce autoimmunity and immune-mediated CNS damage in a disease phase-dependent manner. Understanding the unique properties of Treg and their complex interplay with effector cells represents a prerequisite for the development of new therapeutic approaches in neurotropic virus infections.

Antiviral Therapy of Haemorrhagic Fevers and Arbovirus Infections

RNA viruses of the families Arena-, Bunya-, Filo-, Flavi-and Togaviridae cause illness in humans ranging from mild, non-specific febrile syndromes to fulminant, lethal haemorrhagic fever. They are transmitted from animals to humans and from human to human by arthropods, aerosols or contact with body fluids. Antiviral compounds, convalescent plasma and interferon inhibit many of these agents in vitro and in virus-infected animals. Drug or plasma treatment is now in use for several human diseases, and would probably be beneficial for a number of others for which there is only limited treatment experience. Success is linked to early diagnosis and initiation of therapy. Ribavirin is used to treat Lassa fever and haemorrhagic fever with renal syndrome, and would probably be effective for Crimean-Congo haemorrhagic fever and for all New World arenavirus diseases. The value of ribavirin in the early treatment of hantavirus pulmonary syndrome is under evaluation. Convalescent plasma is the therapy of choice for Argentine haemorrhagic fever, and would also probably be effective for other New World arenaviruses and some other infections if a safe supply of plasma could be maintained. Ribavirin and interferon-α have both shown protective efficacy in non-human primates infected with Rift Valley fever virus. No effective therapy has yet been identified for filovirus infections, but results in animal models are encouraging. More clinical research is urgently needed. Even if placebo-controlled drug trials cannot be performed, conscientious reports of the results of therapy in limited numbers of patients can still provide evidence of antiviral drug effects.

Critical View on the Usage of Ribavirin in Already Existing Psychostimulant-Use Disorder

Substance-use disorder represents a frequently hidden non-communicable chronic disease. Patients with intravenous drug addiction are at high risk of direct exposure to a variety of viral infections and are considered to be the largest subpopulation infected with the hepatitis C virus. Ribavirin is a synthetic nucleoside analog that has been used as an integral component of hepatitis C therapy. However, ribavirin medication is quite often associated with pronounced psychiatric adverse effects. It is not well understood to what extent ribavirin per se contributes to changes in drug-related neurobehavioral disturbances, especially in the case of psychostimulant drugs, such as amphetamine. It is now well-known that repeated amphetamine usage produces psychosis in humans and behavioral sensitization in animals. On the other hand, ribavirin has an affinity for adenosine A1 receptors that antagonistically modulate the activity of dopamine D1 receptors, which play a critical role in the development of behavioral sensitization. This review will focus on the current knowledge of neurochemical/ neurobiological changes that exist in the psychostimulant drug-addicted brain itself and the antipsychotic-like efficiency of adenosine agonists. Particular attention will be paid to the potential side effects of ribavirin therapy, and the opportunities and challenges related to its application in already existing psychostimulant-use disorder.

Neuronal maturation reduces the type I IFN response to orthobunyavirus infection and leads to increased apoptosis of human neurons

BACKGROUND

La Crosse virus (LACV) is the leading cause of pediatric arboviral encephalitis in the USA. LACV encephalitis can result in learning and memory deficits, which may be due to infection and apoptosis of neurons in the brain. Despite neurons being the primary cell infected in the brain by LACV, little is known about neuronal responses to infection.

METHODS

Human cerebral organoids (COs), which contain a spectrum of developing neurons, were used to examine neuronal responses to LACV. Plaque assay and quantitative reverse transcription (qRT) PCR were used to determine the susceptibility of COs to LACV infection. Immunohistochemistry, flow cytometry, and single-cell transcriptomics were used to determine specific neuronal subpopulation responses to the virus.

RESULTS

Overall, LACV readily infected COs causing reduced cell viability and increased apoptosis. However, it was determined that neurons at different stages of development had distinct responses to LACV. Both neural progenitors and committed neurons were infected with LACV, however, committed neurons underwent apoptosis at a higher rate. Transcriptomic analysis showed that committed neurons expressed fewer interferon (IFN)-stimulated genes (ISGs) and genes involved IFN signaling in response to infection compared to neural progenitors. Furthermore, induction of interferon signaling in LACV-infected COs by application of recombinant IFN enhanced cell viability.

CONCLUSIONS

These findings indicate that neuronal maturation increases the susceptibility of neurons to LACV-induced apoptosis. This susceptibility is likely due, at least in part, to mature neurons being less responsive to virus-induced IFN as evidenced by their poor ISG response to LACV. Furthermore, exogenous administration of recombinant IFN to LACV COs rescued cellular viability suggesting that increased IFN signaling is overall protective in this complex neural tissue. Together these findings indicate that induction of IFN signaling in developing neurons is an important deciding factor in virus-induced cell death.

Lymphocytes have a role in protection, but not in pathogenesis, during La Crosse Virus infection in mice

BACKGROUND

La Crosse Virus (LACV) is a primary cause of pediatric viral encephalitis in the USA and can result in severe clinical outcomes. Almost all cases of LACV encephalitis occur in children 16 years or younger, indicating an age-related susceptibility. This susceptibility is recapitulated in a mouse model where weanling (3 weeks old or younger) mice are susceptible to LACV-induced disease, and adults (greater than 6 weeks) are resistant. Disease in mice and humans is associated with infiltrating leukocytes to the CNS. However, what cell types are infiltrating into the brain during virus infection and how these cells influence pathogenesis remain unknown.

METHODS

In the current study, we analyzed lymphocytes recruited to the CNS during LACV-infection in clinical mice, using flow cytometry. We analyzed the contribution of these lymphocytes to LACV pathogenesis in weanling mice using knockout mice or antibody depletion. Additionally, we studied at the potential role of these lymphocytes in preventing LACV neurological disease in resistant adult mice.

RESULTS

In susceptible weanling mice, disease was associated with infiltrating lymphocytes in the CNS, including NK cells, CD4 T cells, and CD8 T cells. Surprisingly, depletion of these cells did not impact neurological disease, suggesting these cells do not contribute to virus-mediated damage. In contrast, in disease-resistant adult animals, depletion of both CD4 T cells and CD8 T cells or depletion of B cells increased neurological disease, with higher levels of virus in the brain.

CONCLUSIONS

Our current results indicate that lymphocytes do not influence neurological disease in young mice, but they have a critical role protecting adult animals from LACV pathogenesis. Although LACV is an acute virus infection, these studies indicate that the innate immune response in adults is not sufficient for protection and that components of the adaptive immune response are necessary to prevent virus from invading the CNS.

Encephalitic Arboviruses: Emergence, Clinical Presentation, and Neuropathogenesis

Arboviruses are arthropod-borne viruses that exhibit worldwide distribution, contributing to systemic and neurologic infections in a variety of geographical locations. Arboviruses are transmitted to vertebral hosts during blood feedings by mosquitoes, ticks, biting flies, mites, and nits. While the majority of arboviral infections do not lead to neuroinvasive forms of disease, they are among the most severe infectious risks to the health of the human central nervous system. The neurologic diseases caused by arboviruses include meningitis, encephalitis, myelitis, encephalomyelitis, neuritis, and myositis in which virus- and immune-mediated injury may lead to severe, persisting neurologic deficits or death. Here we will review the major families of emerging arboviruses that cause neurologic infections, their neuropathogenesis and host neuroimmunologic responses, and current strategies for treatment and prevention of neurologic infections they cause.

Molecular identification of Aedes triseriatus and Aedes hendersoni by a novel duplex polymerase chain reaction assay

Aedes triseriatus is the principal vector of La Crosse virus (LACv), which is the most common cause of pediatric arboviral encephalitis in North America. Here we report a novel species-specific polymerase chain reaction (PCR) assay that differentially identifies Ae. triseriatus and Ae. hendersoni. Because these 2 sibling species differ in their abilities to transmit LACv, accurate identification is critical for surveillance, research, and control programs. This duplex assay can detect the presence of both species in a single PCR reaction and is therefore simpler and faster than previously reported methods.

A recombinant chimeric La Crosse virus expressing the surface glycoproteins of Jamestown Canyon virus is immunogenic and protective against challenge with either parental virus in mice or monkeys

La Crosse virus (LACV) and Jamestown Canyon virus (JCV), family Bunyaviridae, are mosquito-borne viruses that are endemic in North America and recognized as etiologic agents of encephalitis in humans. Both viruses belong to the California encephalitis virus serogroup, which causes 70 to 100 cases of encephalitis a year. As a first step in creating live attenuated viral vaccine candidates for this serogroup, we have generated a recombinant LACV expressing the attachment/fusion glycoproteins of JCV. The JCV/LACV chimeric virus contains full-length S and L segments derived from LACV. For the M segment, the open reading frame (ORF) of LACV is replaced with that derived from JCV and is flanked by the untranslated regions of LACV. The resulting chimeric virus retained the same robust growth kinetics in tissue culture as observed for either parent virus, and the virus remains highly infectious and immunogenic in mice. Although both LACV and JCV are highly neurovirulent in 21 day-old mice, with 50% lethal dose (LD₅₀) values of 0.1 and 0.5 log₁₀ PFU, respectively, chimeric JCV/LACV is highly attenuated and does not cause disease even after intracerebral inoculation of 10³ PFU. Parenteral vaccination of mice with 10¹ or 10³ PFU of JCV/LACV protected against lethal challenge with LACV, JCV, and Tahyna virus (TAHV). The chimeric virus was infectious and immunogenic in rhesus monkeys and induced neutralizing antibodies to JCV, LACV, and TAHV. When vaccinated monkeys were challenged with JCV, they were protected against the development of viremia. Generation of highly attenuated yet immunogenic chimeric bunyaviruses could be an efficient general method for development of vaccines effective against these pathogenic viruses.

Antiviral drugs for viruses other than human immunodeficiency virus

Most viral diseases, with the exception of those caused by human immunodeficiency virus, are self-limited illnesses that do not require specific antiviral therapy. The currently available antiviral drugs target 3 main groups of viruses: herpes, hepatitis, and influenza viruses. With the exception of the antisense molecule fomivirsen, all antiherpes drugs inhibit viral replication by serving as competitive substrates for viral DNA polymerase. Drugs for the treatment of influenza inhibit the ion channel M(2) protein or the enzyme neuraminidase. Combination therapy with Interferon-α and ribavirin remains the backbone treatment for chronic hepatitis C; the addition of serine protease inhibitors improves the treatment outcome of patients infected with hepatitis C virus genotype 1. Chronic hepatitis B can be treated with interferon or a combination of nucleos(t)ide analogues. Notably, almost all the nucleos(t) ide analogues for the treatment of chronic hepatitis B possess anti-human immunodeficiency virus properties, and they inhibit replication of hepatitis B virus by serving as competitive substrates for its DNA polymerase. Some antiviral drugs possess multiple potential clinical applications, such as ribavirin for the treatment of chronic hepatitis C and respiratory syncytial virus and cidofovir for the treatment of cytomegalovirus and other DNA viruses. Drug resistance is an emerging threat to the clinical utility of antiviral drugs. The major mechanisms for drug resistance are mutations in the viral DNA polymerase gene or in genes that encode for the viral kinases required for the activation of certain drugs such as acyclovir and ganciclovir. Widespread antiviral resistance has limited the clinical utility of M(2) inhibitors for the prevention and treatment of influenza infections. This article provides an overview of clinically available antiviral drugs for the primary care physician, with a special focus on pharmacology, clinical uses, and adverse effects.

Safety and pharmacokinetics of ribavirin for the treatment of la crosse encephalitis

BACKGROUND

La Crosse viral encephalitis (LACVE) is associated with residual epilepsy and neurocognitive deficits in survivors. This report summarizes 3 phases of clinical studies of children treated with intravenous (IV) ribavirin (RBV), each one exploring a different phase (I, IIA, IIB) of clinical trial development.

METHODS

In phase I, 7 children with life-threatening LACVE were treated with emergency use RBV using a moderate IV dose (8.33 mg/kg/dose q 8 hours day 1, 5 mg/kg/dose q 8 hours days 2-10). In phase IIA, 12 children with severe LACVE were enrolled: 8 treated with RBV (same dose as phase I) and 4 with placebo. In phase IIB an escalated dose was used (33 mg/kg dose 1, then 16 mg/kg/dose q 6 hours for 4 days, and 8 mg/kg/dose q 8 hours for 3 days).

RESULTS

In a group of 15 children treated in phase I and phase IIA, RBV appeared safe at moderate dose, but based on steady-state RBV levels of 9.3 μM, estimated cerebrospinal fluid levels were less than 20% of the EC50 of RBV for LACVE. At the escalated dose used in phase IIB, adverse events occurred, likely related to RBV, and therefore the trial was discontinued. Nevertheless, valuable pharmacokinetic (PK) and safety data were obtained at moderate dose, with potential treatment implications for other indications.

CONCLUSIONS

Although the results do not support the use of RBV for LACVE, this nevertheless is the largest study of antiviral treatment for LACVE to date and the largest pharmacokinetic analysis of IV RBV in children for any indication.

La crosse virus encephalitis preceding neurosarcoidosis diagnosed by brain biopsy

Childhood neurosarcoidosis is rare, and its etiology is unknown. La Crosse virus is one of the most common causes of encephalitis in North America. We report the case of a 12-year-old boy who had La Crosse virus encephalitis and subsequently developed imaging and pathologic findings suggestive of neurosarcoidosis. He presented with acute onset of transient aphasia 4 months after an episode of encephalitis; serology results at the time of aphasia were positive for La Crosse virus. Brain MRI revealed diffuse subcortical nodular lesions. His serum angiotensin-converting enzyme level was elevated, and brain biopsy revealed noncaseating granuloma. It is interesting to note that he has had no recurrence of aphasia; repeat MRI showed significant improvement of nodular lesions without therapy. To our knowledge, this is the first case of La Crosse virus encephalitis associated with neurosarcoid findings.

Review of the literature and proposed guidelines for the use of oral ribavirin as postexposure prophylaxis for Lassa fever

Lassa fever is an acute viral hemorrhagic illness; the virus is endemic in West Africa and also of concern with regard to bioterrorism. Transmission of Lassa virus between humans may occur through direct contact with infected blood or bodily secretions. Oral administration of the antiviral drug ribavirin is often considered for postexposure prophylaxis, but no systematically collected data or uniform guidelines exist for this indication. Furthermore, the relatively low secondary attack rates for Lassa fever, the restriction of the area of endemicity to West Africa, and the infrequency of high-risk exposures make it unlikely that controlled prospective efficacy trials will ever be possible. Recommendations for postexposure use of ribavirin can therefore be made only on the basis of a thorough understanding and logical extrapolation of existing data. Here, we review the pertinent issues and propose guidelines based on extensive review of the literature, as well as our experience in this field. We recommend oral ribavirin postexposure prophylaxis for Lassa fever exclusively for definitive high-risk exposures. These guidelines may also serve for exposure to other hemorrhagic fever viruses susceptible to ribavirin.

Arboviral encephalitides: transmission, emergence, and pathogenesis

Arthropod-borne viruses (arboviruses) are of paramount concern as a group of pathogens at the forefront of emerging and re-emerging diseases. Although some arboviral infections are asymptomatic or present with a mild influenza-like illness, many are important human and veterinary pathogens causing serious illness ranging from rash and arthritis to encephalitis and hemorrhagic fever. Here, we discuss arboviruses from diverse families (Flaviviruses, Alphaviruses, and the Bunyaviridae) that are causative agents of encephalitis in humans. An understanding of the natural history of these infections as well as shared mechanisms of neuroinvasion and neurovirulence is critical to control the spread of these viruses and for the development of effective vaccines and treatment modalities.

A duplex real-time reverse transcriptase polymerase chain reaction assay for the detection of California serogroup and Cache Valley viruses

A duplex TaqMan real-time reverse transcriptase polymerase chain reaction (PCR) assay was developed for the detection of California (CAL) serogroup viruses and Cache Valley virus (CVV), for use in human surveillance. The targets selected for the assay were the sequences encoding the nucleocapsid protein of CAL and the G1 glycoprotein of CVV. Conserved regions were selected by aligning genetic sequences from various strains available in the GenBank database. Primers and probes were selected in conserved regions. The assay sensitivity was 75 gene copies (gc)/reaction for CAL serogroup viruses and 30 gc/reaction for CVV. The performance of the assay was linear over at least 6 log(10) gc. The assay was specific, given that it did not cross-react with a variety of pathogens. It did, however, detect 11 viruses within the CAL serogroup and 12 CVV isolates. The use of an internal control ensured that possible inefficiency in nucleic acid extraction or PCR inhibition would be detected.

Randomized, controlled trial of oral ribavirin for Japanese encephalitis in children in Uttar Pradesh, India

BACKGROUND

Japanese encephalitis is associated with high rates of mortality and disabling sequelae. To date, no specific antiviral has proven to be of benefit for this condition. We attempted to determine the efficacy of oral ribavirin treatment for reducing early mortality among children with Japanese encephalitis in Uttar Pradesh, India.

METHODS

Children (age, 6 months to 15 years) who had been hospitalized with acute febrile encephalopathy (a < or =2-week history of fever plus altered sensorium) were tested for the presence of immunoglobulin M antibodies to Japanese encephalitis virus with commercial immunoglobulin M capture enzyme-linked immunosorbent assay. Children with positive results were randomized to receive either ribavirin (10 mg/kg per day in 4 divided doses for 7 days) or placebo syrup through nasogastric tube or by mouth. The primary outcome was early mortality; secondary outcome measures were early (at hospital discharge; normal or nearly normal, independent functioning, dependent, vegetative state, or death) outcome, time to resolution of fever, time to resumption of oral feeding, duration of hospitalization, and late outcome (> or =3 months after hospital discharge). The study was double-blind, and analysis was by intention to treat.

RESULTS

A total of 153 patients were enrolled during a 3-year period; 70 patients received ribavirin, and 83 received placebo. There was no statistically significant difference between the 2 groups in the early mortality rate: 19 (27.1%) of 70 ribavirin recipients and 21 (25.3%) of 83 placebo recipients died (odds ratio, 1.10; 95% confidence interval, 0.5-2.4). No statistically significant differences in secondary outcome measures were found.

CONCLUSIONS

For the dosage schedule used in our study, oral ribavirin has no effect in reducing early mortality associated with Japanese encephalitis.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00216268 .

Original research: Intravenous ribavirin--review of the FDA's Emergency Investigational New Drug Database (1997-2008) and literature review

Intravenous (IV) ribavirin does not have US Food and Drug Administration (FDA) approval, although oral and aerosol formulations have been approved. Intravenous ribavirin can, however, be authorized for use as a result of an Emergency Investigational New Drug (EIND) application as investigational treatment for patients with serious viral infections, including emerging or rare infections for which no alternative treatment is available. This retrospective study evaluated clinical experience with IV ribavirin based on a review of the FDA's EIND database and a literature review. The main outcome measures were disease condition, clinical outcomes, and adverse events (AEs). First, the FDA's EIND database was evaluated for these variables among patients authorized to receive investigational IV ribavirin. Second, published literature on IV ribavirin was reviewed for diseases treated, reported clinical outcomes, and AEs. Adverse events reported in the literature were compared with AEs listed in approved product labeling (aerosol and oral formulations). From February 1997 to December 2008, 608 IV ribavirin EIND requests were made for 19 disease conditions. Adenovirus, respiratory syncytial virus, and parainfluenza infections comprised 84.7% of IV ribavirin EINDs. Inadequate reporting of clinical outcomes and AEs in the EIND database prevented analysis of either outcome. Data interpretation in the literature was limited by multiple factors, including retrospective design, small sample sizes, differences in reporting outcomes and AEs, lack of generalizability, and potential confounders such as concomitant medications, selection bias, and reporting bias. Reported AEs were consistent with labels of approved aerosol and oral formulations, except for lip and gingival swelling. However, estimates of frequency, severity, and causality of AEs associated with IV ribavirin could not be determined because of study limitations. Our study findings suggest that the literature is inconclusive on the potential benefit for continued use of IV ribavirin. A review of the literature and the FDA's EIND database suggests that prospective, controlled trials of IV ribavirin in patients with adenovirus, parainfluenza, or serious respiratory syncytial virus infections could be feasible.

Progress on the development of therapeutics against West Nile virus

A decade has passed since the appearance of West Nile virus (WNV) in humans in the Western Hemisphere in New York City. During this interval, WNV spread inexorably throughout North and South America and caused millions of infections ranging from a sub-clinical illness, to a self-limiting febrile syndrome or lethal neuroinvasive disease. Its entry into the United States triggered intensive research into the basic biology of WNV and the elements that comprise a protective host immune response. Although no therapy is currently approved for use in humans, several strategies are being pursued to develop effective prophylaxis and treatments. This review describes the current state of knowledge on epidemiology, clinical presentation, pathogenesis, and immunobiology of WNV infection, and highlights progress toward an effective therapy.

The use of oral ribavirin in the management of La Crosse viral infections

Since its recognition in 1964, La Crosse (LAC) virus has been recognized as an important cause of pediatric encephalitis in the United States. The annual incidence of this illness is believed to be between 20 and 30 cases per hundred thousand, though most cases remain undiagnosed. It is typically responsible for a relatively mild disease in humans, though a sub-group of patients suffer from life-threatening illness characterized by permanent neuropsychiatric sequelae. There are currently no approved medications to treat LAC viral infections. However, an anti-RNA viral treatment might prove useful in reducing the length and severity of illness while potentially reducing the risk of permanent sequelae. Evidence exists that the use of ribavirin may form the basis of an effective treatment for LAC viral infections. We propose that oral ribavirin may provide a useful treatment to limit the severity and improve the prognosis of those suffering from LAC viral infections.

Ribavirin reduces mortality in enterovirus 71-infected mice by decreasing viral replication

Enterovirus 71 (EV71) causes fatal encephalitis in young children. However, there is no effective antiviral drug available for infected patients. Ribavirin is currently used for the treatment of several RNA virus infections clinically, so its anti-EV71 efficacy was evaluated. In vitro results showed that ribavirin effectively reduced the viral yields (with an IC₅₀ of 65 μg/mL) and virus-induced cytopathic effect in human and mouse cell lines. In vivo results showed that ribavirin reduced the mortality, morbidity, and subsequent paralysis sequelae in infected mice by decreasing viral loads in tissues. Thus, ribavirin could be a potential anti-EV71 drug

La Crosse virus infectivity, pathogenesis, and immunogenicity in mice and monkeys

BACKGROUND

La Crosse virus (LACV), family Bunyaviridae, was first identified as a human pathogen in 1960 after its isolation from a 4 year-old girl with fatal encephalitis in La Crosse, Wisconsin. LACV is a major cause of pediatric encephalitis in North America and infects up to 300,000 persons each year of which 70-130 result in severe disease of the central nervous system (CNS). As an initial step in the establishment of useful animal models to support vaccine development, we examined LACV infectivity, pathogenesis, and immunogenicity in both weanling mice and rhesus monkeys.

RESULTS

Following intraperitoneal inoculation of mice, LACV replicated in various organs before reaching the CNS where it replicates to high titer causing death from neurological disease. The peripheral site where LACV replicates to highest titer is the nasal turbinates, and, presumably, LACV can enter the CNS via the olfactory neurons from nasal olfactory epithelium. The mouse infectious dose50 and lethal dose50 was similar for LACV administered either intranasally or intraperitoneally. LACV was highly infectious for rhesus monkeys and infected 100% of the animals at 10 PFU. However, the infection was asymptomatic, and the monkeys developed a strong neutralizing antibody response.

CONCLUSION

In mice, LACV likely gains access to the CNS via the blood stream or via olfactory neurons. The ability to efficiently infect mice intranasally raises the possibility that LACV might use this route to infect its natural hosts. Rhesus monkeys are susceptible to LACV infection and develop strong neutralizing antibody responses after inoculation with as little as 10 PFU. Mice and rhesus monkeys are useful animal models for LACV vaccine immunologic testing although the rhesus monkey model is not optimal.

Periodic lateralized epileptiform discharges in La Crosse encephalitis, a worrisome subgroup: clinical presentation, electroencephalogram (EEG) patterns, and long-term neurologic outcome

La Crosse virus encephalitis is the most common mosquito-borne virus in children in the United States. La Crosse virus encephalitis has emerged as a significant health concern due to its potential for acute morbidity, including seizures, alterations in mental status, and, in rare cases, death, as well as the potential for chronic morbidity, including, epilepsy and cognitive and behavioral disorders. The aim of this study is to provide a clinical description of the largest series of children reported with periodic lateralizing epileptiform discharges (PLEDS) associated with La Cross virus encephalitis with reference to their clinical course, seizure type, electroencephalogram (EEG) patterns, and 2- and 10-year long-term neurologic outcome. In addition, to evaluate whether this subset of children may indeed have more severe disease than children with La Crosse virus encephalitis without PLEDS, comparisons are made between the 2 groups on specific variables. All patients presented with fever and disorientation; 6 of the 9 (66%) presented with seizures. PLEDS localized to the temporal lobe in 7 patients (77%). The children with PLEDS had longer intensive care unit stays (6.5 +/- 2.4 vs 3.2 +/- 1.9; P < .0001), a higher rate of intubation (88% vs 20%; P < .001), and a higher rate of cerebral herniation (1%; P < .05) than children with La Crosse virus encephalitis without PLEDS. Follow-up data on the subset with PLEDS also suggest a relatively high rate of epilepsy and behavioral difficulties with hyperactivity symptoms, memory deficits, and school difficulties. The implications for recognition, management, and follow-up of this worrisome subset of patients with La Crosse virus encephalitis are discussed.

Development of effective therapies against West Nile virus infection

Since its entry into North America in 1999, West Nile virus has spread throughout the USA and Canada, and now annually causes a clinical spectrum of human disease ranging from a self-limiting acute febrile illness to potentially lethal encephalitis. Although no therapy is currently approved for use in humans, several strategies are being pursued to develop effective prophylaxis and treatments. This review describes the epidemiology, clinical presentation and pathogenesis of West Nile virus infection, and highlights recent progress towards an effective therapy.

Nucleic acid amplification assays for detection of La Crosse virus RNA

We report the development of nucleic acid sequence-based amplification (NASBA) and quantitative real-time reverse transcription (RT)-PCR assays for the detection of La Crosse (LAC) virus in field-collected vector mosquito samples and human clinical samples. The sensitivities of these assays were compared to that of a standard plaque assay in Vero cells. The NASBA and quantitative real-time RT-PCR assays demonstrated sensitivities greater than that of the standard plaque assay. The specificities of these assays were determined by testing a battery of reference strain viruses, including representative strains of LAC virus and other arthropod-borne viruses. Additionally, these assays were used to detect LAC viral RNA in mosquito pool samples and human brain tissue samples and yielded results within less than 4 h. The NASBA and quantitative real-time RT-PCR assays detect LAC viral RNA in a sensitive, specific, and rapid manner; these findings support the use of these assays in surveillance and diagnostic laboratory systems.

5'-nor carbocyclic ribavirin

An efficient synthesis of 5'-nor carbocyclic ribavirin (4) is described in 13 steps from conveniently available (+)-(IR,4S)-4-hydroxy-2-cyclopenten-1-yl acetate (6). Compound 4 was evaluated against the following viruses: herpes simplex type 1 and 2, vaccinia, cowpox, smallpox, Ebola, hepatitis B, hepatitis C, adenovirus type 1, influenza A (H1N1 and H3N2), influenza B, parainfluenza type 3, Pichinde, Punta Toro A, respiratory syncytial, rhinovirus type 2, Venezuelan equine encephalitis, yellow fever, and West Nile. No activity was found nor was there any cytotoxicity to the viral host cells.

Viral meningitis and encephalitis: traditional and emerging viral agents

In the United States, the annual number of central nervous system (CNS) infections that occur as a result of viral agents far exceeds that of infections caused by bacteria, yeast, molds, and protozoa combined. The recent incursion of West Nile virus (WNV) into North America has led to a dramatic change in the incidence and epidemiology of summer-associated viral CNS disease. As a result of increased testing for WNV, lesser known viral causes of CNS infection have been identified. Even the epidemiology of such traditional viral neuropathogens as rabies has changed in recent years. This review provides an overview of viruses traditionally associated with meningitis and encephalitis (enteroviruses, La Crosse virus, St. Louis encephalitis virus, eastern and western equine viruses, varicella-zoster virus), as well as several of the less common (Powassan virus, lymphocytic choriomeningitis virus, Colorado tick fever virus, rabies virus, influenza viruses, etc.) and emerging (West Nile virus) viral pathogens.

La Crosse encephalitis in children

BACKGROUND

La Crosse encephalitis is a mosquito-borne disease that can be mistaken for herpes simplex encephalitis. It has been reported in 28 states but may be underrecognized.

METHODS

We investigated the manifestations and clinical course of La Crosse encephalitis in 127 patients hospitalized from 1987 through 1996. The diagnosis was established by serologic testing for IgM and IgG antibodies to La Crosse virus. Data were collected by chart review.

RESULTS

Most of the patients were school-aged children (mean [+/-SD] age, 7.8+/-3.5 years; range, 0.5 to 15.0). Symptoms included headache, fever, and vomiting (each in 70 percent or more of the patients), seizures (in 46 percent), and disorientation (in 42 percent). Thirteen percent had aseptic meningitis. Hyponatremia developed in 21 percent, and there were signs of increased intracranial pressure in 13 percent. Six patients, including three with cerebral herniation, underwent intracranial-pressure monitoring. The 13 patients (11 percent) whose condition deteriorated in the hospital had decreases in serum sodium levels (P=0.007), and increases in body temperature (P=0.003) at the time of deterioration. At admission, these patients more often had a history of vomiting (P=0.047) and a score of 12 or lower on the Glasgow Coma Scale (P=0.02) than the others; a trend toward a greater prevalence of seizures at admission was also evident in this group (P=0.07). All the patients survived, but 15 of them (12 percent) had neurologic deficits at discharge. Follow-up assessments, performed in 28 children, suggested an increase in cognitive and behavioral deficits 10 to 18 months after the episode of encephalitis.

CONCLUSIONS

La Crosse virus infection should be considered in children who present with aseptic meningitis or encephalitis. Hyponatremia and increasing body temperature may be related to clinical deterioration.

Combined treatment with interferon-alpha and ribavirin for subacute sclerosing panencephalitis

Two patients with subacute sclerosing panencephalitis (SSPE) are described. They were diagnosed on admission to the hospital with SSPE, as judged on cerebrospinal fluid examination involving reverse transcription followed by polymerase chain reaction, at the second stage of Jabbour's classification. They first were treated with intraventricular interferon-alpha monotherapy; however, the combination of interferon-alpha and IV ribavirin was started at 8 and 5 months after beginning the interferon-alpha monotherapy, respectively. Although slow progressive brain atrophy was observed in Patient 1 on brain magnetic resonance imaging before the ribavirin therapy, no further progression was noted 11 months after starting combination therapy with ribavirin. The event-related potential study results and audiography of the right ear improved in Patient 1 after the combination therapy was initiated. In Patient 2 the hypertonicity, neurobladder incontinence, and dysphagia improved 3 months after starting the combination treatment. Although this group of patients is small, these results suggest treatment with intrathecal high-dose interferon-alpha and IV ribavirin is effective in the treatment of SSPE. Early administration of intrathecal high-dose interferon-alpha and IV ribavirin should be considered as a possible therapy for SSPE patients, especially interferon-nonresponding ones.

La Crosse encephalitis presenting like herpes simplex encephalitis in an immunocompromised adult

The diagnosis of the precise cause of viral encephalitis can be difficult, hampered by the nonspecific presentation, the number of etiologic viruses, and limited culture and serologic diagnostic methods. Because herpes simplex encephalitis (HSE) can be neurologically devastating and is treatable, timely diagnosis is important. We report an immunocompromised adult with encephalitis clinically consistent with HSE who had serology consistent with recent La Crosse encephalitis (LAC).

Severe La Crosse encephalitis with significant neurologic sequelae

La Crosse encephalitis, a member of the California arbovirus group, is the most common cause of reported mosquito-borne illness in the United States. Approximately 70 cases of La Crosse encephalitis are reported each year. The principal vector is the mosquito Aedes triseriatus. During the summer the virus is amplified horizontally in a cycle among small mammals such as chipmunks and squirrels. Infected female A. triseriatus deposit eggs in the basal holes of hardwood trees, although man-made containers and old tires containing water also supply a suitable breeding site. Some of these eggs infected with La Crosse virus hatch the next spring and give rise to infected adult A. triseriatus, and the host-vector cycle is renewed. Only a minority of children infected with the virus become ill. Clinical disease caused by La Crosse is usually mild, and neurologic sequelae are relatively uncommon. In this report we describe six patients with severe La Crosse meningoencephalitis diagnosed within a 4-week period. All patients required intensive care management, and there was a high rate of neurologic sequelae, suggesting that La Crosse is not necessarily a benign meningoencephalitis.

Encephalitis

Encephalitis is an acute infection of brain parenchyma characterized clinically by fever, headache, and an altered level of consciousness. There may also be focal or multifocal neurologic deficits, and focal or generalized seizure activity. This article discusses the clinical presentation, diagnosis, and treatment of herpes simplex virus (HSV) encephalitis, the arthropodborne viral encephalidities, Rocky Mountain spotted fever, viral encephalitis in the immunocompromised patient, and postinfectious encephalomyelitis.

La Crosse and other forms of California encephalitis

The California serogroup viruses are mosquito viruses that cause human infections on five continents. They are maintained and amplified in nature by a wide variety of mosquito vectors and mammalian hosts; they thrive in a remarkably wide variety of microclimates (eg, tropical, coastal temperate marshland, lowland river valleys, alpine valleys and highlands, high boreal deserts, and arctic steppes). In 1993, California serogroup viruses caused 71% of all cases of arboviral illness in the United States, principally La Crosse encephalitis. The 30 to 180 annual cases of La Crosse encephalitis represent 8% to 30% of all cases of encephalitis, rendering this illness the most common and important endemic mosquito-borne illness in the USA. Subclinical or mild infections are much more common. Methods and results acquired from intense study of California serogroup viruses have been applied, with benefit, to the study of the ecology and pathogenesis of many more serious human arboviral illnesses. The evolutionary potential of viruses, with particular reference to the development of more virulent strains, has been studied more closely in the California serogroup viruses than in almost any other agent of human disease.

Characterization of La Crosse virus RNA in autopsied central nervous system tissues

A reverse transcription-PCR (RT-PCR) technique was used to detect La Crosse (LAC) virus RNA in the central nervous system (CNS) tissues of two patients who died of LAC encephalitis in 1960 and 1978. Viral RNA was readily detected by RT-PCR although the tissues had been stored frozen for up to 37 years. LAC virus was detected in the cerebral cortex but not in other CNS tissues. RT-PCR allowed detection of replicative forms of the virus, indicating that the virus was actively replicating in the specific CNS tissues. The small (S) RNA segments of the viruses from the CNS samples were demonstrated to be genetically similar by single-strand conformation polymorphism analyses. These S RNA segments were then sequenced; only two base changes were demonstrated between the 1960 and the 1978 samples, suggesting that LAC virus is genetically stable in areas of endemicity. The RT-PCR analyses of analyte directly from CNS tissues allows study of the virus without passage in cell culture.

California-La Crosse encephalitis

La Crosse encephalitis, a mosquito-borne viral disease that can be mistaken for herpes simplex encephalitis, is under-recognized in the United States, despite case reports from 28 states and an incidence in endemic areas (20-30/100,000) exceeding that of bacterial meningitis. The disease recurs every summer in endemic foci in the midwestern and mid-Atlantic United States in areas forested with hardwood trees, which provide breeding sites for the treehole-dwelling mosquito vector, Aedes triseriatus. La Crosse encephalitis should be considered in the child presenting with meningoencephalitis in summer and early fall, particularly for children living in (or recent travel to) endemic areas in mid-Atlantic and midwestern states.

Prevention and treatment recommendations for respiratory syncytial virus infection. Background and clinical experience 40 years after discovery

Though 40 years have passed since its discovery, respiratory syncytial virus (RSV), one of the most ubiquitous viruses known, continues to evade most of our efforts to prevent or treat the clinical disease it causes. Long recognised as the most common cause of lower respiratory tract infections in virtually all children in the first 2 years of life, it has been increasingly recognised as a cause of more serious disease in several 'high risk' populations. These populations include infants with cardiac or pulmonary disease and infants and adults with immunodeficiencies, particularly those undergoing bone marrow transplantation. Early attempts to immunise children with a simple formalin-inactivated vaccine led to severe disease in vaccinated children who subsequently were infected with RSV from the community. Other vaccine constructs have failed for a variety of reasons, although surface glycoprotein subunit vaccines may hold promise. For years, ribavirin, a synthetic nucleoside analogue administered by constant aerosol, has been felt by many to lead to more rapid improvement in clinical disease caused by RSV, but it is still unclear whether its benefits are truly significant. An intravenous immunoglobulin product prepared from donors screened for the presence of high titres of RSV neutralising antibody (known as RSVIG) appears to be well tolerated and relatively effective in protecting high-risk infants against serious RSV disease, although therapeutic use has proven less dramatic. At least one monoclonal antibody undergoing current testing may prove easier to use in similar immunoprophylactic use. Results on the use of corticosteroids as supportive therapy have not been conclusive. In short, RSV will continue to be a challenge for clinicians and researchers well into the next century.