Clinical characteristics of the West Nile fever outbreak, Israel, 2000

A Case of West Nile Virus Neuroinvasive Disease Presenting With Isolated Diplopia

West Nile virus (WNV) is a single-stranded RNA virus causing a wide spectrum of diseases. Neuroinvasive conditions such as meningitis and encephalitis are feared complications of WNV infection. Here, we describe the case of a 78-year-old male whose only initial presenting symptoms were fever and transient diplopia, whose initial MRI imaging with and without contrast did not reveal any abnormalities. He was discharged, only to return to care the next day; lumbar puncture was performed suggesting bacterial meningitis, and he was admitted and given antibiotics. Repeat MRI was negative, and he developed an altered mental status requiring intubation. WNV neuroinvasive disease was subsequently found after serology was performed. Supportive care was given, and he made a full recovery with no residual deficits. This case highlights an unusual presentation of WNV encephalitis and highlights the difficulty that can be present in diagnosing this disease.

Detection of West Nile Virus Envelope Protein in Brain Tissue with an Immunohistochemical Assay

Immunohistochemistry is a valuable tool for probing not only scientific questions but also clinical diagnoses. It provides power from localization of a protein within the milieu of a tissue section that may reflect positioning within or beyond the boundaries of a cell that is representative of the tissue at a discrete moment in time. The method can be applied broadly, including to tissues under normal, developmental, chemically, or genetically altered conditions and disease states.Disease manifesting from West Nile virus infection ranges from acute, systemic febrile symptoms to compromise of central nervous system function. Immunohistochemistry has been used to assess WNV infection in the nervous system in postmortem and experimental conditions, despite the lack of understanding of the precise route of viral entry. In addition to imprecise knowledge of initial viral entry into cells and whether entry is even the same between cell types, the fact that spontaneous viral mutations and environmental pressures from climate change may alter the prevalence of the disease state across geographical and climatological boundaries highlights the need for continued assessment of infection. Immunohistochemistry is a useful way to assess these aspects of WNV infection with the aim being to better understand the organs and cell types that are compromised by WNV infection. This chapter outlines how this can be carried out on brain tissue, but the procedures discussed can also be applied more broadly on tissue outside of the central nervous system.

Immune ageing at single-cell resolution

Ageing leads to profound alterations in the immune system and increases susceptibility to some chronic, infectious and autoimmune diseases. In recent years, widespread application of single-cell techniques has enabled substantial progress in our understanding of the ageing immune system. These comprehensive approaches have expanded and detailed the current views of ageing and immunity. Here we review a body of recent studies that explored how the immune system ages using unbiased profiling techniques at single-cell resolution. Specifically, we discuss an emergent understanding of age-related alterations in innate and adaptive immune cell populations, antigen receptor repertoires and immune cell-supporting microenvironments of the peripheral tissues. Focusing on the results obtained in mice and humans, we describe the multidimensional data that align with established concepts of immune ageing as well as novel insights emerging from these studies. We further discuss outstanding questions in the field and highlight techniques that will advance our understanding of immune ageing in the future.

A 20-year historical review of West Nile virus since its initial emergence in North America: Has West Nile virus become a neglected tropical disease?

After the unexpected arrival of West Nile virus (WNV) in the United States in 1999, the mosquito-borne virus quickly spread throughout North America. Over the past 20 years, WNV has become endemic, with sporadic epizootics. Concerns about the economic impact of infection in horses lead to the licensure of an equine vaccine as early as 2005, but few advances regarding human vaccines or treatments have since been made. There is a high level of virus transmission in hot/humid, subtropical climates, and high morbidity that may disproportionately affect vulnerable populations including the homeless, elderly, and those with underlying health conditions. Although WNV continues to cause significant morbidity and mortality at great cost, funding and research have declined in recent years. These factors, combined with neglect by policy makers and amenability of control measures, indicate that WNV has become a neglected tropical disease.

Could Chronic Idiopatic Intestinal Pseudo-Obstruction Be Related to Viral Infections?

Chronic idiopathic intestinal pseudo-obstruction (CIIPO) is a disease characterized by symptoms and signs of small bowel obstruction in the absence of displayable mechanical obstruction. Due to the known neuropathic capacity of several viruses, and their localization in the intestine, it has been hypothesized that such viruses could be involved in the pathogenesis of CIIPO. The most frequently involved viruses are John Cunningham virus, Herpesviridae, Flaviviruses, Epstein–Barr virus and Citomegalovirus. Therefore, the present narrative review aims to sum up some new perspectives in the etiology and pathophysiology of CIIPO.

Molecular characterization of the re-emerging West Nile virus in avian species and equids in Israel, 2018, and pathological description of the disease

BACKGROUND

In this report we describe the molecular and pathological characteristics of West Nile virus (WNV) infection that occurred during the summer and fall of 2018 in avian species and equines. WNV is reported in Israel since the 1950s, with occasional outbreaks leading to significant morbidity and mortality in birds, high infection in horses and humans, and sporadic fatalities in humans.

METHODS

Animal and avian carcasses in a suitable condition were examined by post-mortem analysis. Tissue samples were examined for WNV by RT-qPCR and the viral load was quantified. Samples with sufficient material quality were further analyzed by Endpoint PCR and sequencing, which was used for phylogenetic analysis. Tissue samples from positive animals were used for culturing the virus in Vero and C6/36 cells.

RESULTS

WNV RNA was detected in one yellow-legged gull (Larus michahellis), two long-eared owls (Asio otus), two domesticated geese (Anser anser), one pheasant (Phasianus colchicus), four hooded crows (Corvus cornix), three horses and one donkey. Pathological and histopathological findings were characteristic of viral infection. Molecular analysis and viral load quantification showed varying degrees of infection, ranging between 70-1.4 × 106 target copies per sample. Phylogenetic analysis of a 906-bp genomic segment showed that all samples belonged to Lineage 1 clade 1a, with the following partition: five samples from 2018 and one sample detected in 2016 were of Cluster 2 Eastern European, two of Cluster 2 Mediterranean and four of Cluster 4. Four of the positive samples was successfully propagated in C6/36 and Vero cell lines for further work.

CONCLUSIONS

WNV is constantly circulating in wild and domesticated birds and animals in Israel, necessitating constant surveillance in birds and equines. At least three WNV strains were circulating in the suspected birds and animals examined. Quantitative analysis showed that the viral load varies significantly between different organs and tissues of the infected animals.

Anti-Flavivirus Vaccines: Review of the Present Situation and Perspectives of Subunit Vaccines Produced in Escherichia coli

This article aims to review the present status of anti-flavivirus subunit vaccines, both those at the experimental stage and those already available for clinical use. Aspects regarding development of vaccines to Yellow Fever virus, (YFV), Dengue virus (DENV), West Nile virus (WNV), Zika virus (ZIKV), and Japanese encephalitis virus (JEV) are highlighted, with particular emphasis on purified recombinant proteins generated in bacterial cells. Currently licensed anti-flavivirus vaccines are based on inactivated, attenuated, or virus-vector vaccines. However, technological advances in the generation of recombinant antigens with preserved structural and immunological determinants reveal new possibilities for the development of recombinant protein-based vaccine formulations for clinical testing. Furthermore, novel proposals for multi-epitope vaccines and the discovery of new adjuvants and delivery systems that enhance and/or modulate immune responses can pave the way for the development of successful subunit vaccines. Nonetheless, advances in this field require high investments that will probably not raise interest from private pharmaceutical companies and, therefore, will require support by international philanthropic organizations and governments of the countries more severely stricken by these viruses.

West Nile Virus: An Update on Pathobiology, Epidemiology, Diagnostics, Control and "One Health" Implications

West Nile virus (WNV) is an important zoonotic flavivirus responsible for mild fever to severe, lethal neuroinvasive disease in humans, horses, birds, and other wildlife species. Since its discovery, WNV has caused multiple human and animal disease outbreaks in all continents, except Antarctica. Infections are associated with economic losses, mainly due to the cost of treatment of infected patients, control programmes, and loss of animals and animal products. The pathogenesis of WNV has been extensively investigated in natural hosts as well as in several animal models, including rodents, lagomorphs, birds, and reptiles. However, most of the proposed pathogenesis hypotheses remain contentious, and much remains to be elucidated. At the same time, the unavailability of specific antiviral treatment or effective and safe vaccines contribute to the perpetuation of the disease and regular occurrence of outbreaks in both endemic and non-endemic areas. Moreover, globalisation and climate change are also important drivers of the emergence and re-emergence of the virus and disease. Here, we give an update of the pathobiology, epidemiology, diagnostics, control, and “One Health” implications of WNV infection and disease.

Epidemiologic and phylogenetic analysis of the 2018 West Nile virus (WNV) outbreak in Israel demonstrates human infection of WNV lineage I

As at 12 November 2018, an outbreak of West Nile virus (WNV) was responsible for 139 WNV infection cases in Israel. Here, we characterise the epidemiology of the outbreak and demonstrate that only WNV lineage I was circulating in mosquitoes and responsible for WNV infection in humans. This suggests that the concurrence of the outbreak in Israel with WNV outbreaks in several European countries is not due to a common, more virulent WNV genotype.

Seropositivity of West Nile Virus Among Acute Febrile Patients in Southern Ethiopia

Background

West Nile virus (WNV) is one of the widely distributed arboviruses in the world, and it is a pathogen of both humans and animals. The evidence that supports the prevalence of the WNV infection in Ethiopia is very scarce. Hence, this study aimed to assess the seropositivity of WNV among patients with acute febrile illness.

Methods

This health institution-based descriptive cross-sectional study was conducted on 532 acute febrile patients from May to August 2016 in Arba Minch Zuria district selected public health facilities, Southern Ethiopia. A pre-structured questionnaire was used to collect socio-demographic and clinical related information of the participants through convenient sampling techniques. In addition, trained nurses who were working in the health centers were responsible for interviewing acute febrile patients. About 5 mL of venous blood was collected aseptically from each of the study participants for the screening of the WNV immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies using indirect immunofluorescence technique (IIFT) as per manufacturer’s protocol. Data analysis was done using statistical package for social sciences (SPSS) version 20 software and the results were presented by frequency and percentage using tables.

Results

A total number of 529 acute febrile patients (42.7% males and 57.3% females) were enrolled in the study with a response rate of 99.4%. The overall 7.4% of acute febrile patients were seropositive for WNV-specific IgG and the rate was higher in males (9.7%) when compared to females (5.6%). While the overall 4.5% were seropositive for WNV-specific IgM and the rate was 6.6% in males and 3.0% in females.

Conclusion

The finding of this study is an important alarm for clinicians/physicians to diagnose febrile patients in the divergent direction including with the diagnosis of flaviviruses. In addition, the finding will further contribute to understanding the epidemiology of WNV fever in Ethiopia and it will play a role in the delivery of public health measures to decrease the risk of WNV exposure in the areas.

Retrospective Descriptive Analysis of West Nile Neuroinvasive Disease (WNND) in Northwest Louisiana

Aims

The aim of the study was to describe the presentation characteristics and epidemiology of WNND in Louisiana to improve future recognition of cases and decrease inappropriate antibiotic use. Settings and Design. It was a retrospective descriptive-analytic cohort study. A total of 23 patients with WNND were identified at one tertiary care hospital center in Northwest Louisiana from a retrospective chart review from January 1, 2012 to October 31, 2017.

Results

The median age was 49 years (range: 15–75) for patients with WNND. Of 23 patients diagnosed with WNND, twelve (52%) were diagnosed with encephalitis (WNE), six (26%) were diagnosed with meningitis (WNM), and five (22%) with myelitis (WNME). The common symptoms with WNND were fever in 65%, altered mental status in 61%, headache in 52%, fatigue in 43%, gastrointestinal symptoms in 43%, rigors in 30%, imbalance in 26%, rash in 9%, and seizures in 26% of patients. Most patients presented in the late summer season. The average duration of antibiotics given was six days. The average number of days from the admission to the diagnosis of WNND was nine days (3 to 16 days). Twenty-one (91%) patients survived the infection.

Conclusions

Identifying WNV infection early in its clinical course would help in decreasing inappropriate antibiotic use when patients presented with fever and meningeal symptoms. Performing WNV serology in CSF studies is critical in making the diagnosis.

In vitro and in silico Models to Study Mosquito-Borne Flavivirus Neuropathogenesis, Prevention, and Treatment

Mosquito-borne flaviviruses can cause disease in the nervous system, resulting in a significant burden of morbidity and mortality. Disease models are necessary to understand neuropathogenesis and identify potential therapeutics and vaccines. Non-human primates have been used extensively but present major challenges. Advances have also been made toward the development of humanized mouse models, but these models still do not fully represent human pathophysiology. Recent developments in stem cell technology and cell culture techniques have allowed the development of more physiologically relevant human cell-based models. In silico modeling has also allowed researchers to identify and predict transmission patterns and discover potential vaccine and therapeutic candidates. This review summarizes the research on in vitro and in silico models used to study three mosquito-borne flaviviruses that cause neurological disease in humans: West Nile, Dengue, and Zika. We also propose a roadmap for 21st century research on mosquito-borne flavivirus neuropathogenesis, prevention, and treatment.

Arenaviruses and West Nile Virus in solid organ transplant recipients: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the epidemiology, diagnosis, prevention, and management of infection due to Arenaviruses and West Nile Virus (WNV) in the pre- and post-transplant period. Arenaviruses and WNV have been identified as causes of both donor-derived and post-transplant infection. Most data related to these infections have been published in case reports and case series. Transplant recipients may become infected with Arenaviruses if they, or their donors, are exposed to wild rodents or infected pet rodents. Lymphocytic choriomeningitis virus is the most commonly recognized Arenavirus among transplant recipients and should be considered when transplant recipients present with fever, hepatitis, meningitis/encephalitis, and/or multisystem organ failure. WNV is a mosquito-borne virus, and as such, its incidence varies yearly depending on environmental conditions. WNV in transplant recipients typically presents with fever, myalgias, and rash; approximately one in 40 develop neuroinvasive disease. Due to its morbidity, the Organ Procurement and Transplantation Network recently mandated that transplant centers screen living donors for WNV infection in endemic areas. Little is known about the optimal treatment of Arenaviruses or WNV; reduction in immunosuppression and supportive care are the mainstays of management at present.

Viral RNA-Dependent RNA Polymerase Inhibitor 7-Deaza-2'-C-Methyladenosine Prevents Death in a Mouse Model of West Nile Virus Infection

West Nile virus (WNV) is a medically important emerging arbovirus causing serious neuroinfections in humans and against which no approved antiviral therapy is currently available. In this study, we demonstrate that 2'-C-methyl- or 4'-azido-modified nucleosides are highly effective inhibitors of WNV replication, showing nanomolar or low micromolar anti-WNV activity and negligible cytotoxicity in cell culture. One representative of C2'-methylated nucleosides, 7-deaza-2'-C-methyladenosine, significantly protected WNV-infected mice from disease progression and mortality. Twice daily treatment at 25 mg/kg starting at the time of infection resulted in 100% survival of the mice. This compound was highly effective, even if the treatment was initiated 3 days postinfection, at the time of a peak of viremia, which resulted in a 90% survival rate. However, the antiviral effect of 7-deaza-2'-C-methyladenosine was absent or negligible when the treatment was started 8 days postinfection (i.e., at the time of extensive brain infection). The 4'-azido moiety appears to be another important determinant for highly efficient inhibition of WNV replication in vitro However, the strong anti-WNV effect of 4'-azidocytidine and 4'-azido-aracytidine was cell type dependent and observed predominantly in porcine kidney stable (PS) cells. The effect was much less pronounced in Vero cells. Our results indicate that 2'-C-methylated or 4'-azidated nucleosides merit further investigation as potential therapeutic agents for treating WNV infections as well as infections caused by other medically important flaviviruses.

Rapidly progressive neurologic decline and morbilliform rash presenting in a patient with lymphoma

A 67-year-old male with past medical history of mantle cell lymphoma and atrial fibrillation presented with a truncal rash, bilateral lower extremity weakness, and confusion. Within three days of presentation, his condition rapidly deteriorated with the onset of diffuse flaccid paralysis, aphasia, and severe alteration in mental status. Initial results from serum studies, lumbar puncture, magnetic resonance imaging, and electroencephalogram were not diagnostic. However, on the ninth day after initial presentation, the West Nile Virus (WNV) immunoglobulin M antibody returned positive from the cerebrospinal fluid. West Nile Virus encephalitis is endemic worldwide, and is the most common viral encephalitis in the United States. WNV presents in a variety of ways, and the recognition by physicians is crucial due to the estimated 2-12% mortality rate and significant longterm morbidity of neuroinvasive disease. The initial management and long term prognosis are points of ongoing research. This case represents a particularly profound example of neuroinvasive WNV. Our patient made a significant recovery after his initial presentation with aggressive supportive care, however still suffers from bilateral lower extremity weakness more than a year later.

Intestinal Dysmotility Syndromes following Systemic Infection by Flaviviruses

Although chronic gastrointestinal dysmotility syndromes are a common worldwide health problem, underlying causes for these disorders are poorly understood. We show that flavivirus infection of enteric neurons leads to acute neuronal injury and cell death, inflammation, bowel dilation, and slowing of intestinal transit in mice. Flavivirus-primed CD8⁺ T cells promote these phenotypes, as their absence diminished enteric neuron injury and intestinal transit delays, and their adoptive transfer reestablished dysmotility after flavivirus infection. Remarkably, mice surviving acute flavivirus infection developed chronic gastrointestinal dysmotility that was exacerbated by immunization with an unrelated alphavirus vaccine or exposure to a non-infectious inflammatory stimulus. This model of chronic post-infectious gastrointestinal dysmotility in mice suggests that viral infections with tropism for enteric neurons and the ensuing immune response might contribute to the development of bowel motility disorders in humans. These results suggest an opportunity for unique approaches to diagnosis and therapy of gastrointestinal dysmotility syndromes.

Epidemiologic and clinical parameters of West Nile virus infections in humans: a scoping review

Background

Clinical syndromes associated with West Nile virus (WNV) infection range from fever to neuroinvasive disease. Understanding WNV epidemiology and disease history is important for guiding patient care and healthcare decision-making. The objective of this review was to characterize the existing body of peer-reviewed and surveillance literature on WNV syndromes and summarize epidemiologic and clinical parameters.

Methods

We followed scoping review methodology described by the Joanna Briggs Institute. Terms related to WNV epidemiology, hospitalization, and surveillance were searched in four bibliographic databases (MEDLINE, EMBASE, Scopus, and CINAHL) for literature published from January 1999 to December 2015.

Results

In total, 2334 non-duplicated titles and abstracts were screened; 92 primary studies were included in the review. Publications included one randomized controlled trial and 91 observational studies. Sample sizes ranged from under 25 patients (n = 19) to over 400 patients (n = 28). Eight studies were from Canada, seven from Israel, and the remaining (n = 77) from the United States. N = 17 studies were classified as outbreak case investigations following epidemics; n = 37 with results of regional/national surveillance and monitoring programs.

Mean patient ages were > 40 years old; three studies (3%) focused on the pediatric population. Patients with encephalitis fared worse than patients with meningitis and fever, considering hospitalization, length of stay, discharge, recovery, and case-fatality. Several studies examined risk factors; however, age was the only risk factor for neuroinvasive disease/death consistently identified. Overall, patients with acute flaccid paralysis or encephalitis fared worse than patients with meningitis and West Nile fever in terms of hospitalization and mortality. Among the included studies, proportion hospitalized, length of stay, proportion discharged home and case-fatality ranged considerably.

Conclusion

Our review highlights the heterogeneity among reporting clinical WNV syndromes and epidemiologic parameters of WNV-related illness. Presently, there is potential for further synthesis of the risk factors of WNV-illness and mortality; undertaking further analysis through a systematic review and meta-analysis may benefit our understanding of risk factors for emerging mosquito-borne diseases. Future research on the burden of WNV can build on existing evidence summarized in this review, not only to support our understanding of endemic WNV, but also to strengthen research on emerging arboviruses with similar clinical manifestations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2637-9) contains supplementary material, which is available to authorized users.

Broad-spectrum agents for flaviviral infections: dengue, Zika and beyond

Infections with flaviviruses, such as dengue, West Nile virus and the recently re-emerging Zika virus, are an increasing and probably lasting global risk. This Review summarizes and comments on the opportunities for broad-spectrum agents that are active against multiple flaviviruses. Broad-spectrum activity is particularly desirable to prepare for the next flaviviral epidemic, which could emerge from as-yet unknown or neglected viruses. Potential molecular targets for broad-spectrum antiflaviviral compounds include viral proteins, such as the viral protease or polymerase, and host targets that are exploited by these viruses during entry and replication, including α-glucosidase and proteins involved in nucleoside biosynthesis. Numerous compounds with broad-spectrum antiviral activity have already been identified by target-specific or phenotypic assays. For other compounds, broad-spectrum activity can be anticipated because of their mode of action and molecular targets.

Protective and Pathological Immunity during Central Nervous System Infections

The concept of immune privilege of the central nervous system (CNS) has dominated the study of inflammatory processes in the brain. However, clinically relevant models have highlighted that innate pathways limit pathogen invasion of the CNS and adaptive immunity mediates control of many neural infections. As protective responses can result in bystander damage, there are regulatory mechanisms that balance protective and pathological inflammation, but these mechanisms might also allow microbial persistence. The focus of this review is to consider the host-pathogen interactions that influence neurotropic infections and to highlight advances in our understanding of innate and adaptive mechanisms of resistance as key determinants of the outcome of CNS infection. Advances in these areas have broadened our comprehension of how the immune system functions in the brain and can readily overcome immune privilege.

The seroprevalence of West Nile Virus in Israel: A nationwide cross sectional study

West Nile Virus (WNV) is endemic in Israel, affecting yearly 40-160 individuals. Israel is located on a central migratory path between Africa and Eurasia and most West Nile Fever (WNF) cases reported in recent years were among residents of the coastal plain. The aim of the study was to evaluate the seroprevalence of WNV among the Israeli population and to assess correlates for WNV infection. A cross-sectional nationwide serologic survey was conducted using 3,145 serum samples collected by the national Israeli serum bank during 2011-2014, representing all age and population groups in Israel. Prevalence rates of WNV IgG antibodies were determined. Logistic regressions models were applied to assess the associations between demographic characteristics and WNV seropositivity. 350 samples were positive to WNV (11.1%; 95%CI: 10.0-12.3%). In the multivariable analysis, there was a significant association between seropositivity and the Arab population group vs. Jews and others (OR = 1.86, 95%CI: 1.37-2.52), the time lived in Israel [50-59 years vs. 0-9 years; OR = 10.80 (95%CI: 1.03-113.46) and ≥60 years vs. 0-9 years; OR = 14.00 (1.32-148.31)] residence area] Coastal Plain, Inland Plain (Shfela) and Great Rift Valley vs. Upper Galilee; OR = 2.24 (95%CI: 1.37-3.65), OR = 2.18 (95%CI: 1.18-4.03), OR = 1.90 (95%CI: 1.10-3.30), respectively [and rural vs. urban settlement (OR = 1.65, 95%CI: 1.26-2.16). People, who reside in the Coastal Plain, Inland Plain and Great Rift Valley, should be aware of the risk of contracting WNV and reduce exposure to mosquito bites, using insect repellents, and wearing protective clothing. The Ministry of Environmental Protection should be active in reducing the mosquito population by eliminating sources of standing water, a breeding ground for mosquitoes.

The Importance of Haematological and Biochemical Findings in Patients with West Nile Virus Neuroinvasive Disease

BACKGROUND

West Nile virus neuroinvasive disease (WNND) occurs in less than 1% of infected people. Leukocytosis with lymphocytopenia, mild anaemia, thrombocytopenia, elevated liver and muscle enzymes and hyponatremia are occasionally present in patients with WNND. Cerebrospinal fluid (CSF) findings resemble other viral neuroinfections. The purpose of this study is to pre sent some of the most important laboratory findings of our patients with WNND and to evaluate their correlation with fatal outcome.

METHODS

The study included 161 patients with WNND. Their blood and CSF samples were cytobiochemically analysed and the obtained variables were then tested for predictive significance of the disease outcome, or used for differentiation between two clinical syndromes (encephalitis vs meningitis).

RESULTS

West Nile encephalitis was present in 127 (78.9%) patients and West Nile meningitis was diagnosed in 34 (21.1%) cases. Leukocytosis was found in 45.9% patients. CRP level higher than 100 mg/L was registered only in those with encephalitis (p=0.020). CSF leukocyte count was 146±171 per microlitre, with slight lymphocytic predominance (mean 52%). Hypoglycorrhachia was registered in 9.3% of our patients with WNND. Twenty-eight (17.4%) patients died and all of them had encephalitis. Independent predictors of fatal outcome in WNND were serum CRP > 100 mg/L (p=0.011) and CSF proteins > 1 g/L (p=0.002).

CONCLUSIONS

WNND usually affects older males. Prolonged neutrophilic predominance in CSF can occasionally be present, as well as hypoglycorrhachia. Patients with encephalitis, high serum CRP and high CSF protein level have a higher risk of fatal outcome.

Identification of genetic variants associated with susceptibility to West Nile virus neuroinvasive disease

West Nile virus (WNV) infection results in a diverse spectrum of outcomes, and host genetics are likely to influence susceptibility to neuroinvasive disease (West Nile neuroinvasive disease (WNND)). We performed whole-exome sequencing of 44 individuals with WNND and identified alleles associated with severe disease by variant filtration in cases, kernel association testing in cases and controls and single-nucleotide polymorphism (SNP) imputation into a larger cohort of WNND cases and seropositive controls followed by genome-wide association analysis. Variant filtration prioritized genes based on the enrichment of otherwise rare variants, but did not unambiguously implicate variants shared by a majority of cases. Kernel association demonstrated enrichment for risk and protective alleles in the human leukocyte antigen (HLA)-A and HLA-DQB1 loci that have well understood roles in antiviral immunity. Two loci, HERC5 and an intergenic region between CD83 and JARID2, were implicated by multiple imputed SNPs and exceeded genome-wide significance in a discovery cohort (n=862). SNPs at two additional loci, TFCP2L1 and CACNA1H, achieved genome-wide significance after association testing of directly genotyped and imputed SNPs in a discovery cohort (n=862) and a separate replication cohort (n=1387). The context of these loci suggests that immunoregulatory, ion channel and endothelial barrier functions may be important elements of the host response to WNV.

A Novel Synthetic TLR-4 Agonist Adjuvant Increases the Protective Response to a Clinical-Stage West Nile Virus Vaccine Antigen in Multiple Formulations

West Nile virus (WNV) is a mosquito-transmitted member of the Flaviviridae family that has emerged in recent years to become a serious public health threat. Given the sporadic nature of WNV epidemics both temporally and geographically, there is an urgent need for a vaccine that can rapidly provide effective immunity. Protection from WNV infection is correlated with antibodies to the viral envelope (E) protein, which encodes receptor binding and fusion functions. Despite many promising E-protein vaccine candidates, there are currently none licensed for use in humans. This study investigates the ability to improve the immunogenicity and protective capacity of a promising clinical-stage WNV recombinant E-protein vaccine (WN-80E) by combining it with a novel synthetic TLR-4 agonist adjuvant. Using the murine model of WNV disease, we find that inclusion of a TLR-4 agonist in either a stable oil-in-water emulsion (SE) or aluminum hydroxide (Alum) formulation provides both dose and dosage sparing functions, whereby protection can be induced after a single immunization containing only 100 ng of WN-80E. Additionally, we find that inclusion of adjuvant with a single immunization reduced viral titers in sera to levels undetectable by viral plaque assay. The enhanced protection provided by adjuvanted immunization correlated with induction of a Th1 T-cell response and the resultant shaping of the IgG response. These findings suggest that inclusion of a next generation adjuvant may greatly enhance the protective capacity of WNV recombinant subunit vaccines, and establish a baseline for future development.

Neurotropic virus infections as the cause of immediate and delayed neuropathology

A wide range of viruses from different virus families in different geographical areas, may cause immediate or delayed neuropathological changes and neurological manifestations in humans and animals. Infection by neurotropic viruses as well as the resulting immune response can irreversibly disrupt the complex structural and functional architecture of the central nervous system, frequently leaving the patient or affected animal with a poor or fatal prognosis. Mechanisms that govern neuropathogenesis and immunopathogenesis of viral infections are highlighted, using examples of well-studied virus infections that are associated with these alterations in different populations throughout the world. A better understanding of the molecular, epidemiological and biological characteristics of these infections and in particular of mechanisms that underlie their clinical manifestations may be expected to provide tools for the development of more effective intervention strategies and treatment regimens.

Age-Dependent Cell Trafficking Defects in Draining Lymph Nodes Impair Adaptive Immunity and Control of West Nile Virus Infection

Impaired immune responses in the elderly lead to reduced vaccine efficacy and increased susceptibility to viral infections. Although several groups have documented age-dependent defects in adaptive immune priming, the deficits that occur prior to antigen encounter remain largely unexplored. Herein, we identify novel mechanisms for compromised adaptive immunity that occurs with aging in the context of infection with West Nile virus (WNV), an encephalitic flavivirus that preferentially causes disease in the elderly. An impaired IgM and IgG response and enhanced vulnerability to WNV infection during aging was linked to delayed germinal center formation in the draining lymph node (DLN). Adoptive transfer studies and two-photon intravital microscopy revealed a decreased trafficking capacity of donor naïve CD4+ T cells from old mice, which manifested as impaired T cell diapedesis at high endothelial venules and reduced cell motility within DLN prior to antigen encounter. Furthermore, leukocyte accumulation in the DLN within the first few days of WNV infection or antigen-adjuvant administration was diminished more generally in old mice and associated with a second aging-related defect in local cytokine and chemokine production. Thus, age-dependent cell-intrinsic and environmental defects in the DLN result in delayed immune cell recruitment and antigen recognition. These deficits compromise priming of early adaptive immune responses and likely contribute to the susceptibility of old animals to acute WNV infection.

An outbreak of West Nile Virus infection in the region of Monastir, Tunisia, 2003

BACKGROUND

A West Nile (WN) fever epidemic occurred in the region of Monastir, Tunisia, between August and October 2003.

AIM OF THE STUDY

We attempt to describe the epidemiology, clinical presentation, and outcome of patients with confirmed West Nile virus (WNV) infection.

METHODS

Three groups of specimens were prepared. One was made up of serum only (n  =  43), the other of cerebrospinal fluid (CSF) only (n  =  30), and the third group was made up of both (n  =  40). These specimens were obtained from 113 patients. A serological diagnosis and evidence of WNV genome by nested reverse-transcriptase polymerase chain reaction (nRT-PCR) and TaqMan reverse transcription-polymerase chain reaction (RT-PCR) were carried out.

RESULTS

Thirty-eight cases (33.6%) were serologically positive. Results of nRT-PCR showed a total of 10 positive cases of WNV (8.8%) detected in group 1 (n  =  1/43), group 2 (n  =  5/30), and group 3 (n  =  4/40) whereas the PCR TaqMan showed 18 positive samples (15.9%) found in group 1 (n  =  3/43), group 2 (n  =  9/30), and group 3 (n  =  6/40). All TaqMan PCR positive cases were nRT-PCR positive. In addition, four serologically probable cases were confirmed by TaqMan PCR. The attempts to isolate WNV by cell culture were unsuccessful. Considering the results of TaqMan assay and the serological diagnosis, WNV infection was confirmed in a total of 42 patients. The main clinical presentations were meningoencephalitis (40%), febrile disease (95%), and meningitis (36%). Eight patients (19%) died. The highest case-fatality rates occurred among patients aged ≧55 years. The phylogenetic analysis revealed that isolates of WNV were closely related to the Tunisian strain 1997 (PAH001) and the Israeli one (Is-98).

CONCLUSIONS

West Nile virus is a reemerging global pathogen that remains an important public health challenge in the next decade.

Multiplexed digital mRNA profiling of the inflammatory response in the West Nile Swiss Webster mouse model

BACKGROUND AND PURPOSE

The ability to track changes in gene expression following viral infection is paramount to understanding viral pathogenesis. This study was undertaken to evaluate the nCounter, a high throughput digital gene expression system, as a means to better understand West Nile virus (WNV) dissemination and the inflammatory response against WNV in the outbred Swiss Webster (SW) mouse model over the course of infection.

METHODOLOGY

The nCounter Mouse Inflammation gene expression kit containing 179 inflammation related genes was used to analyze gene expression changes in multiple tissues over a nine day course of infection in SW mice following intraperitoneal injection with WNV. Protein expression levels for a subset of these cytokine/chemokine genes were determined using a multiplex protein detection system (BioPlex) and comparisons of protein/RNA expression levels made.

RESULTS

Expression analysis of spleen, lung, liver, kidney and brain of SW mice infected with WNV revealed that Cxcl10 and Il12b are differentially expressed in all tissues tested except kidney. Data stratification of positively confirmed infected (WNV (+)) versus non-infected (WNV (-) tissues allowed differentiation of the systemic inflammatory gene response from tissue-specific responses arising from WNV infection. Significant (p<0.05) decrease in C3ar1 was found in WNV (-) spleen. Il23a was significantly upregulated, while Il10rb was down-regulated in WNV (-) lung. Il3 and Mbl2 were down-regulated in WNV (-) liver. In WNV (+) livers, Stat1, Tlr2, chemokines Cxcl1, Cxcl3, Cxcl9, Cxcl10, cytokines Il6, Il18, cytokine-related gene Il1r and cytokine agonist Ilrn were significantly upregulated. In WNV (-) brain tissues, Csf2 and Cxcl10 were significantly upregulated. Similar gene and protein expression kinetics were found for Ccl2, Ccl3, Ccl4 and Ccl5 and correlated with the presence of infectious virus. In summary, the utility of the nCounter platform for rapid identification of gene expression changes in SW mice associated with WNV infection was demonstrated.

Neuroepidemiology and the epidemiology of viral infections of the nervous system

The field of neurovirology will undoubtedly experience evolution and change in the years to come. The epidemiology of viral CNS diseases continues to change, and as our understanding of the pathogenesis and pathophysiology associated with viral agents grows, so does our understanding of the behavior of these pathogens among populations. The appearance of viral pathogens in newsettings, new or unrecognized modes of transmission,and the emergence of previously unrecognized pathogens will continue to challenge our laboratory diagnostic and epidemiologic capabilities. However, each lesson that is learned from this evolving epidemiology will hopefully result in improved surveillance, diagnostic,and treatment and prevention capabilities.

Donor-derived West Nile virus infection in solid organ transplant recipients: report of four additional cases and review of clinical, diagnostic, and therapeutic features

We describe four solid-organ transplant recipients with donor-derived West Nile virus (WNV) infection (encephalitis 3, asymptomatic 1) from a common donor residing in a region of increased WNV activity. All four transplant recipients had molecular evidence of WNV infection in their serum and/or cerebrospinal fluid (CSF) by reverse transcription polymerase chain reaction (RT-PCR) testing. Serum from the organ donor was positive for WNV IgM but negative for WNV RNA, whereas his lymph node and spleen tissues tested positive for WNV by RT-PCR. Combination therapy included intravenous immunoglobulin (4 cases), interferon (3 cases), fresh frozen plasma with WNV IgG (2 cases), and ribavirin (1 case). Two of the four transplant recipients survived.Review of the 20 published cases of organ-derived WNV infection found that this infection is associated with a high incidence of neuroinvasive disease (70%) and severe morbidity and mortality (30%). Median time to onset of symptomatic WNV infection was 13 days after transplantation (range 5-37 days). Initial unexplained fever unresponsive to antibiotic therapy followed by rapid onset of neurologic deficits was the most common clinical presentation. Confirmation of infection was made by testing serum and CSF for both WNV RNA by RT-PCR and WNV IgM by serological assays. Treatment usually included supportive care, reduction of immunosuppression, and frequent intravenous immunoglobulin. The often negative results for WNV by current RT-PCR and serological assays and the absence of clinical signs of acute infection in donors contribute to the sporadic occurrence of donor-derived WNV infection. Potential organ donors should be assessed for unexplained fever and neurological symptoms, particularly if they reside in areas of increased WNV activity.

A review of the epidemiological and clinical aspects of West Nile virus

The resurgence of West Nile virus (WNV) in North America and Europe in recent years has raised the concerns of local authorities and highlighted that mosquito-borne disease is not restricted to tropical regions of the world. WNV is maintained in enzootic cycles involving, primarily, Culex spp. mosquitoes and avian hosts, with epizootic spread to mammals, including horses and humans. Human infection results in symptomatic illness in approximately one-fifth of cases and neuroinvasive disease in less than 1% of infected persons. The most consistently recognized risk factor for neuroinvasive disease is older age, although diabetes mellitus, alcohol excess, and a history of cancer may also increase risk. Despite the increasing public health concern, the current WNV treatments are inadequate. Current evidence supporting the use of ribavirin, interferon α, and WNV-specific immunoglobulin are reviewed. Nucleic acid detection has been an important diagnostic development, which is particularly important for the protection of the donated blood supply. While effective WNV vaccines are widely available for horses, no human vaccine has been registered. Uncertainty surrounds the magnitude of future risk posed by WNV, and predictive models are limited by the heterogeneity of environmental, vector, and host factors, even in neighboring regions. However, recent history has demonstrated that for regions where suitable mosquito vectors and reservoir hosts are present, there will be a risk of major epidemics. Given the potential for these outbreaks to include severe neuroinvasive disease, strategies should be implemented to monitor for, and respond to, outbreak risk. While broadscale mosquito control programs will assist in reducing the abundance of mosquito populations and subsequently reduce the risks of disease, for many individuals, the use of topical insect repellents and other personal protective strategies will remain the first line of defense against infection.

Clinical characteristics and functional outcome of patients with West Nile neuroinvasive disease in Serbia

Neurologic manifestations are prominent characteristic of West Nile virus (WNV) infection. The aim of this article was to describe neurological manifestations in patients with WNV neuroinvasive disease and their functional outcome at discharge in the first human outbreak of WNV infection in Serbia. The study enrolled patients treated in the Clinic for Infectious and Tropical Diseases, Clinical Center Serbia in Belgrade, with serological evidence of acute WNV infection who presented with meningitis, encephalitis and/or acute flaccid paralyses (AFP). Functional outcome at discharge was assessed using modified Rankin Scale (mRS) and Barthel index. Fifty-two patients were analysed. Forty-four (84.6 %) patients had encephalitis, eight (15.4 %) had meningitis, and 13 (25 %) had AFP. Among patients with AFP, 12 resembled poliomyelitis and one had clinical and electrodiagnostic findings consistent with polyradiculoneuritis. Among patients with encephalitis, 17 (32.7 %) had clinical signs of rhombencephalitis, and eight (15.4 %) presented with cerebellitis. Respiratory failure with subsequent mechanical ventilation developed in 13 patients with WNE (29.5 %). Nine (17.3 %) patients died, five (9.6 %) were functionally dependent (mRS 3-5), and 38 (73.1 %) were functionally independent at discharge (mRS 0-2). In univariate analysis, the presence of AFP, respiratory failure and consciousness impairment were found to be predictors of fatal outcome in patients with WNV neuroinvasive disease (p < 0.001, p < 0.001, p = 0.018, respectively). The outbreak of human WNV infection in Serbia caused a notable case fatality ratio, especially in patients with AFP, respiratory failure and consciousness impairment. Rhombencephalitis and cerebellitis could be underestimated presentations of WNV neuroinvasive disease.

Clinical manifestations and outcomes of West Nile virus infection

Since the emergence of West Nile virus (WNV) in North America in 1999, understanding of the clinical features, spectrum of illness and eventual functional outcomes of human illness has increased tremendously. Most human infections with WNV remain clinically silent. Among those persons developing symptomatic illness, most develop a self-limited febrile illness. More severe illness with WNV (West Nile neuroinvasive disease, WNND) is manifested as meningitis, encephalitis or an acute anterior (polio) myelitis. These manifestations are generally more prevalent in older persons or those with immunosuppression. In the future, a more thorough understanding of the long-term physical, cognitive and functional outcomes of persons recovering from WNV illness will be important in understanding the overall illness burden.

West Nile Virus Infection in the Immunocompromised Patient

West Nile virus infection has become the predominant cause of flavivirus-associated encephalitis in the US. While 80 % of infected individuals are asymptomatic, 20 % develop symptoms including fever, headache, transient rash and gastrointestinal symptoms. Among the immunocompetent population, 1 in 150 develop neuroinvasive disease characterized by acute flaccid paralysis, Parkinsonian cogwheel rigidity, meningitis, encephalitis, meningoencephalitis and asymmetric muscle weakness (Mostashari et al. in Lancet 358:261-264, 2001). In the immunocompromised population such as transplant recipients and HIV-infected and chemotherapy patients, the incidence of neuroinvasive disease may be increased. The largest population studied is recipients of solid organ transplants, with data on both donor-derived and naturally occurring transmissions. The risk of neuroinvasive disease in donor-derived infection is estimated to be between 50 % and 75 % while in those with mosquito-borne transmission the risk is estimated at 40 % of those infected (Kumar et al. in Am J Transplant 4:1883-1888, 2004). With significant morbidity associated with donor transmission, specific pretransplant screening recommendations are reviewed. Treatment includes supportive care and consideration for the use of intravenous immunoglobulin.

Outbreak of West Nile virus infection among humans in Serbia, August to October 2012

We describe the first reported outbreak of West Nile virus (WNV) infection in humans in Serbia in August to October 2012 and examine the association of various variables with encephalitis and fatal outcome. Enzyme-linked immunosorbent assay (ELISA) was used for detection of WNV-specific IgM and IgG antibodies in sera and cerebrospinal fluid. A total of 58 patients (mean age: 61 years; standard deviation: 15) were analysed: 44 were from Belgrade and its suburbs; 52 had neuroinvasive disease, of whom 8 had meningitis, while 44 had encephalitis. Acute flaccid paralysis developed in 13 of the patients with encephalitis. Age over 60 years and immunosuppression (including diabetes) were independently associated with the development of encephalitis in a multivariate analysis: odds ratio (OR): 44.8 (95% confidence interval (CI): 4.93–408.59); p=0.001 (age over 60 years); OR: 10.76 (95% CI: 1.06–109.65); p=0.045 (immunosuppression including diabetes). Respiratory failure requiring mechanical ventilation developed in 13 patients with encephalitis. A total of 35 patients had completely recovered by the time they were discharged; nine patients died. The presence of acute flaccid paralysis, consciousness impairment, respiratory failure and immunosuppression (without diabetes) were found to be associated with death in hospital in a univariate analysis (p<0.001, p=0.007, p<0.001 and p=0.010, respectively).

A mastoparan-derived peptide has broad-spectrum antiviral activity against enveloped viruses

Broad-spectrum antiviral drugs are urgently needed to treat individuals infected with new and re-emerging viruses, or with viruses that have developed resistance to antiviral therapies. Mammalian natural host defense peptides (mNHP) are short, usually cationic, peptides that have direct antimicrobial activity, and which in some instances activate cell-mediated antiviral immune responses. Although mNHP have potent activity in vitro, efficacy trials in vivo of exogenously provided mNHP have been largely disappointing, and no mNHP are currently licensed for human use. Mastoparan is an invertebrate host defense peptide that penetrates lipid bilayers, and we reasoned that a mastoparan analog might interact with the lipid component of virus membranes and thereby reduce infectivity of enveloped viruses. Our objective was to determine whether mastoparan-derived peptide MP7-NH2 could inactivate viruses of multiple types, and whether it could stimulate cell-mediated antiviral activity. We found that MP7-NH2 potently inactivated a range of enveloped viruses. Consistent with our proposed mechanism of action, MP7-NH2 was not efficacious against a non-enveloped virus. Pre-treatment of cells with MP7-NH2 did not reduce the amount of virus recovered after infection, which suggested that the primary mechanism of action in vitro was direct inactivation of virus by MP7-NH2. These results demonstrate for the first time that a mastoparan derivative has broad-spectrum antiviral activity in vitro and suggest that further investigation of the antiviral properties of mastoparan peptides in vivo is warranted.

A review of vaccine approaches for West Nile virus

The West Nile virus (WNC) first appeared in North America in 1999. The North American lineages of WNV were characterized by the presence of neuroinvasive and neurovirulent strains causing disease and death in humans, birds and horses. The 2012 WNV season in the United States saw a massive spike in the number of neuroinvasive cases and deaths similar to what was seen in the 2002–2003 season, according to the West Nile virus disease cases and deaths reported to the CDC by year and clinical presentation, 1999–2012, by ArboNET (Arboviral Diseases Branch, Centers for Disease Control and Prevention). In addition, the establishment and recent spread of lineage II WNV virus strains into Western Europe and the presence of neurovirulent and neuroinvasive strains among them is a cause of major concern. This review discusses the advances in the development of vaccines and biologicals to combat human and veterinary West Nile disease.

Immune responses to West Nile virus infection in the central nervous system

West Nile virus (WNV) continues to cause outbreaks of severe neuroinvasive disease in humans and other vertebrate animals in the United States, Europe, and other regions of the world. This review discusses our understanding of the interactions between virus and host that occur in the central nervous system (CNS), the outcome of which can be protection, viral pathogenesis, or immunopathogenesis. We will focus on defining the current state of knowledge of WNV entry, tropism, and host immune response in the CNS, all of which affect the balance between injury and successful clearance.

Medical risk factors for severe West Nile Virus disease, United States, 2008-2010

We conducted enhanced surveillance to identify medical risk factors for severe illness (i.e., hospitalization or death) and neuroinvasive disease (i.e., encephalitis or meningitis) among all West Nile virus disease cases reported from selected states from 2008 to 2010. Of the 1,090 case-patients included in the analysis, 708 (65%) case-patients were hospitalized, 641 (59%) case-patients had neuroinvasive disease, and 55 (5%) case-patients died. Chronic renal disease (adjusted odds ratio [aOR] = 4.1; 95% confidence interval [CI] = 1.4-12.1), history of cancer (aOR = 3.7; 95% CI = 1.8-7.5), history of alcohol abuse (aOR = 3.0; 95% CI = 1.3-6.7), diabetes (aOR = 2.2; 95% CI = 1.4-3.4), and hypertension (aOR = 1.5; 95% CI = 1.1-2.1) were independently associated with severe illness on multivariable analysis. Although the same medical conditions were independently associated with encephalitis, only hypertension was associated with meningitis. The only condition independently associated with death was immune suppression. Prevention messages should be targeted to persons with these conditions.

West Nile virus: A re-emerging pathogen revisited

West Nile virus (WNV), a flavivirus of the Flaviviridae family, is maintained in nature in an enzootic transmission cycle between avian hosts and ornithophilic mosquito vectors, although the virus occasionally infects other vertebrates. WNV causes sporadic disease outbreaks in horses and humans, which may result in febrile illness, meningitis, encephalitis and flaccid paralysis. Until recently, its medical and veterinary health concern was relatively low; however, the number, frequency and severity of outbreaks with neurological consequences in humans and horses have lately increased in Europe and the Mediterranean basin. Since its introduction in the Americas, the virus spread across the continent with worrisome consequences in bird mortality and a considerable number of outbreaks among humans and horses, which have resulted in the largest epidemics of neuroinvasive WNV disease ever documented. Surprisingly, its incidence in human and animal health is very different in Central and South America, and the reasons for it are not yet understood. Even though great advances have been obtained lately regarding WNV infection, and although efficient equine vaccines are available, no specific treatments or vaccines for human use are on the market. This review updates the most recent investigations in different aspects of WNV life cycle: molecular virology, transmission dynamics, host range, clinical presentations, epidemiology, ecology, diagnosis, control, and prevention, and highlights some aspects that certainly require further research.

Insecticide-treated vertical mesh barriers reduce the number of biting mosquitoes

Mosquitoes foraging for blood sources normally fly relatively close to the ground where wind velocities do not exceed their flight speed. An experiment designed to block foraging mosquitoes from reaching inhabited houses was conducted in a rural settlement flanked by agricultural fields. Mosquitoes were collected during 9 nights using 30 carbon dioxide-baited traps deployed along the external walls of six houses in the row closest to the settlement's perimeter fence. Thereafter, a deltamethrin-impregnated mesh was draped along 400 m of the perimeter fence to a height of 2 m opposite three of the monitored houses. Mosquitoes were trapped for a further 11 nights. A significant difference in the numbers of mosquitoes caught before and after the intervention was demonstrated near protected houses, whereas no significant difference was observed in catches near control houses. The percentage of Culex perexiguus (Diptera: Culicidae), an important vector of West Nile virus, was significantly lower near protected houses (13%) than around control houses (45%). By contrast, the percentage of Culex pipiens was not significantly affected (16% at experimental and 18% at control houses). Although the results presented here are preliminary, the data demonstrate the potential efficacy of vertical insecticidal barriers for mosquito control.

Investigation of schizophrenic patients from Istanbul, Turkey for the presence of West Nile virus

Association of some neurotropic viruses like Borna Disease virus and Herpes virus with schizophrenia is better explained. However, the role of West Nile virus (WNV) infection in schizophrenia is not well documented. Therefore, this study was performed to investigate possible association between schizophrenia and presence of antibodies and WNV RNA in schizophrenic patients. For this, 200 blood samples from patients with schizophrenia and 200 from control groups were collected in Istanbul, Turkey. WNV RNA was not detected in any of the 200 patients and 200 controls analyzed by real-time RT-PCR. One hundred and twelve sera of schizophrenic patients and 162 of controls were analyzed for the presence of IgG antibodies to WNV by a commercial IgG-ELISA (Euroimmun, Germany). Antibodies to WNV were detected in 6 schizophrenic patients and 5 controls. ELISA positive patients had antipsychotic therapy. The difference between groups in terms of seropositivity to WNV was not statistically significant (p = 0.887, p = 0.148). Known symptoms of schizophrenia were observed in these patients, and interestingly majority had close contact to cats in the past and come from agricultural area of Turkey where potential area of mosquitoes and bird habitat. In conclusion, the results of this study show that antibodies to WNV in people do not seem to be associated with schizophrenia. However, detecting antibodies to WNV in schizophrenic patients suggests that WNV infection should be considered in endemic areas as it may play role in psychiatric diseases.

The clinical response of West Nile virus neuroinvasive disease to intravenous immunoglobulin therapy

The aim of the study was to determine whether intravenous gamma globulin (IVIG) treatment is effective in patients with West Nile Virus (WNV) neuroinvasive disease. We contacted hospital based infectious disease experts in Israeli hospitals to identify patients with WNV neuroinvasive disease who were treated with IVIG. The main outcome measure was neurological response after treatment. There were 12 patients who received IVIG and four improved within 48 h. Three patients died, 6 had partial recovery, and 3 recovered completely. Eleven of the 12 patients were infected with Israeli genotypes that are highly homologous to Europe/Africa viruses. The rapid response in some patients suggests that IVIG is effective, and might be used to treat patients with WNV neuroinvasive disease with IVIG.

Delayed mortality in a cohort of persons hospitalized with West Nile virus disease in Colorado in 2003

Most mortality associated with West Nile virus (WNV) disease occurs during the acute or early convalescent phases of illness. However, some reports suggest mortality may be elevated for months or longer after acute illness. The objective of this study was to assess the survival of a cohort of patients hospitalized with WNV disease in Colorado in 2003 up to 4 years after illness onset. We calculated age-adjusted standardized mortality ratios (SMRs) to evaluate excess mortality, evaluated reported causes of death in those who died, and analyzed potential covariates of delayed mortality. By 1 year after illness onset, 4% of the 201 patients had died (SMR, 2.7; 95% confidence interval [CI], 1.3-5.2), and 12% had died by 4 years after onset (SMR, 2.0; 95% CI, 1.3-3.0). Among those who had died, the most common immediate and contributory causes of death included pulmonary disease and cardiovascular disease; cancer, hepatic disease, and renal disease were mentioned less frequently. In multivariate analysis, age (hazard ratio [HR], 2.0 per 10-year increase; 95% CI, 1.4-2.7), autoimmune disease (HR, 3.0; 95% CI, 1.1-7.9), ever-use of tobacco (HR, 3.0; 95% CI, 1.3-7.0), encephalitis during acute WNV illness (HR, 2.6; 95% CI, 1.1-6.4), and endotracheal intubation during acute illness (HR 4.8; 95% CI, 1.9-12.1) were found to be independently associated with mortality. Our finding of an approximate twofold increase in mortality for up to 3 years after acute illness reinforces the need for prevention measures against WNV infection among at-risk groups to reduce acute as well as longer-term adverse outcomes.

Association between HLA class I and class II alleles and the outcome of West Nile virus infection: an exploratory study

Background

West Nile virus (WNV) infection is asymptomatic in most individuals, with a minority developing symptoms ranging from WNV fever to serious neuroinvasive disease. This study investigated the impact of host HLA on the outcome of WNV disease.

Methods

A cohort of 210 non-Hispanic mostly white WNV⁺ subjects from Canada and the U.S. were typed for HLA-A, B, C, DP, DQ, and DR. The study subjects were divided into three WNV infection outcome groups: asymptomatic (AS), symptomatic (S), and neuroinvasive disease (ND). Allele frequency distribution was compared pair-wise between the AS, S, and ND groups using χ2 and Fisher's exact tests and P values were corrected for multiple comparisons (Pc). Allele frequencies were compared between the groups and the North American population (NA) used as a control group. Logistic regression analysis was used to evaluate the potential synergistic effect of age and HLA allele phenotype on disease outcome.

Results

The alleles HLA-A*68, C*08 and DQB*05 were more frequently associated with severe outcomes (ND vs. AS, P_A*68 = 0.013/Pc = 0.26, P_C*08 = 0.0075/Pc = 0.064, and P_DQB1*05 = 0.029/Pc = 0.68), However the apparent DQB1*05 association was driven by age. The alleles HLA-B*40 and C*03 were more frequently associated with asymptomatic outcome (AS vs. S, P_B*40 = 0.021/Pc = 0.58 and AS vs. ND P_C*03 = 0.039/Pc = 0.64) and their frequencies were lower within WNV⁺ subjects with neuroinvasive disease than within the North American population (NA vs. S, P_B*40 = 0.029 and NA vs. ND, P_C*03 = 0.032).

Conclusions

Host HLA may be associated with the outcome of WNV disease; HLA-A*68 and C*08 might function as “susceptible” alleles, whereas HLA-B*40 and C*03 might function as “protective” alleles.

Treatment of spatial memory impairment in hamsters infected with West Nile virus using a humanized monoclonal antibody MGAWN1

In addition to functional disorders of paresis, paralysis, and cardiopulmonary complications, subsets of West Nile virus (WNV) patients may also experience neurocognitive deficits and memory disturbances. A previous hamster study has also demonstrated spatial memory impairment using the Morris water maze (MWM) paradigm. The discovery of an efficacious therapeutic antibody MGAWN1 from pre-clinical rodent studies raises the possibility of preventing or treating WNV-induced memory deficits. In the current study, hamsters were treated intraperitoneally (i.p.) with 32 mg/kg of MGAWN1 at 4.5 days after subcutaneously (s.c.) challenging with WNV. As expected, MGAWN1 prevented mortality, weight loss, and improved food consumption of WNV-infected hamsters. The criteria for entry of surviving hamsters into the study were that they needed to have normal motor function (forelimb grip strength, beam walking) and normal spatial reference memory in the MWM probe task. Twenty-eight days after the acute phase of the disease had passed, MGAWN1- and saline-treated infected hamsters were again trained in the MWM. Spatial memory was evaluated 48 h after this training in which the hamsters searched for the location where a submerged escape platform had been positioned. Only 56% of infected hamsters treated with saline spent more time in the correct quadrant than the other three quadrants, as compared to 92% of MGAWN1-treated hamsters (P⩽0.05). Overall these studies support the possibility that WNV can cause spatial memory impairment and that therapeutic intervention may be considered.

West Nile virus and its emergence in the United States of America

Zoonotic West Nile virus (WNV) circulates in natural transmission cycles involving certain mosquitoes and birds, horses, humans, and a range of other vertebrates are incidental hosts. Clinical infections in humans can range in severity from uncomplicated WNV fever to fatal meningoencephalitis. Since its introduction to the Western Hemisphere in 1999, WNV had spread across North America, Central and South America and the Caribbean, although the vast majority of severe human cases have occurred in the United States of America (USA) and Canada. By 2002-2003, the WNV outbreaks have involved thousands of patients causing severe neurologic disease (meningoencephalitis and poliomyelitis-like syndrome) and hundreds of associated fatalities in USA. The purpose of this review is to present recent information on the epidemiology and pathogenicity of WNV since its emergence in North America.