Decreased antiviral immune response within the central nervous system of aged mice is associated with increased lethality of West Nile virus encephalitis.

West Nile virus (WNV) is an emerging pathogen that causes disease syndromes ranging from a mild flu-like illness to encephalitis. While the incidence of WNV infection is fairly uniform across age groups, the risk of lethal encephalitis increases with advanced age. Prior studies have demonstrated age-related, functional immune deficits that limit systemic antiviral immunity and increase mortality; however, the effect of age on antiviral immune responses specifically within the central nervous system (CNS) is unknown. Here, we show that aged mice exhibit increased peripheral organ and CNS tissue viral burden, the latter of which is associated with alterations in activation of both myeloid and lymphoid cells compared with similarly infected younger animals. Aged mice exhibit lower MHCII expression by microglia, and higher levels of PD1 and lower levels of IFNγ expression by WNV-specific CD8+ T cells in the CNS and CD8+ CD45+ cells. These data indicate that the aged CNS exhibits limited local reactivation of T cells during viral encephalitis, which may lead to reduced virologic control at this site.

Mosquito blood-feeding patterns and nesting behavior of American crows, an amplifying host of West Nile virus.

BACKGROUND: Although American crows are a key indicator species for West Nile virus (WNV) and mount among the highest viremias reported for any host, the importance of crows in the WNV transmission cycle has been called into question because of their consistent underrepresentation in studies of Culex blood meal sources. Here, we test the hypothesis that this apparent underrepresentation could be due, in part, to underrepresentation of crow nesting habitat from mosquito sampling designs. Specifically, we examine how the likelihood of a crow blood meal changes with distance to and timing of active crow nests in a Davis, California, population. METHODS: Sixty artificial mosquito resting sites were deployed from May to September 2014 in varying proximity to known crow nesting sites, and Culex blood meal hosts were identified by DNA barcoding. Genotypes from crow blood meals and local crows (72 nestlings from 30 broods and 389 local breeders and helpers) were used to match mosquito blood meals to specific local crows. RESULTS: Among the 297 identified Culex blood meals, 20 (6.7%) were attributable to crows. The mean percentage of blood meals of crow origin was 19% in the nesting period (1 May-18 June 2014), but 0% in the weeks after fledging (19 June-1 September 2014), and the likelihood of a crow blood meal increased with proximity to an active nest: the odds that crows hosted a Culex blood meal were 38.07 times greater within 10 m of an active nest than > 10 m from an active nest. Nine of ten crow blood meals that could be matched to a genotype of a specific crow belonged to either nestlings in these nests or their mothers. Six of the seven genotypes that could not be attributed to sampled birds belonged to females, a sex bias likely due to mosquitoes targeting incubating or brooding females. CONCLUSION: Data herein indicate that breeding crows serve as hosts for Culex in the initial stages of the WNV spring enzootic cycle. Given their high viremia, infected crows could thereby contribute to the re-initiation and early amplification of the virus, increasing its availability as mosquitoes shift to other moderately competent later-breeding avian hosts.

Prediction of unfavorable outcomes in West Nile virus neuroinvasive infection - Result of a multinational ID-IRI study.

BACKGROUND: WNV causes 1.4% of all central nervous system infections and is the most common cause of epidemic neuro-invasive disease in humans. OBJECTIVES: Our main objective was to investigate retrospectively West Nile virus neuroinvasive disease (WNND) cases hospitalized during 2010-2017 and identified factors that can influence prognosis. STUDY DESIGN: We documented the demographic, epidemiologic, clinical and laboratory data of WNND and identified factors that can influence prognosis. The data were recruited through Infectious Diseases International Research Initiative (ID-IRI), which serves as a network for clinical researches. RESULTS: We investigated 165 patients with WNND in 10 countries from three continents. 27 patients died and the mortality rate was 16.4%. In an univariate analysis age, congestive heart failure, neoplasm and ischemic heart disease (p < 0.001), neuropsychiatric disorders (p = 0.011), chronic hepatitis (p = 0.024) and hypertension (p = 0.043) were risk factors for death. Fatal evolution was also correlated with ICU addmission, disorientation, speech disorders, change in consciousnes, coma, a low Glasgow coma score, obtundation, confusion (p < 0.001), history of syncope (p = 0.002) and history of unconsciousness (p = 0.037). In a binomial logistic regresssion analysis only age and coma remained independent prediction factors for death. We created an equation that was calculated according to age, co-morbidities and clinical manifestations that may be used to establish the prognosis of WNND patients. CONCLUSIONS: WNND remain an important factor for morbidity and mortality worldwide, evolution to death or survival with sequelae are not rare. Our study creates an equation that may be used in the future to establish the prognosis of WNND patients.

RIG-I-like receptors direct inflammatory macrophage polarization against West Nile virus infection.

RIG-I-Like Receptors (RLRs) RIG-I, MDA5, and LGP2, are vital pathogen recognition receptors in the defense against RNA viruses. West Nile Virus (WNV) infections continue to grow in the US. Here, we use a systems biology approach to define the contributions of each RLR in the innate immune response to WNV. Genome-wide RNAseq and bioinformatics analyses of macrophages from mice lacking either RLR reveal that the RLRs drive distinct immune gene activation and response polarization to mediate an M1/inflammatory signature while suppressing the M2/wound healing phenotype. While LGP2 functions to modulate inflammatory signaling, RIG-I and MDA5 together are essential for M1 macrophage polarization in vivo and the control of WNV infection through potential downstream control of ATF4 and SMAD4 to regulate target gene expression for cell polarization. These analyses reveal the RLR-driven signature of macrophage polarization, innate immune protection, and immune programming against WNV infection.

West Nile encephalitis mimicking neuropsychiatric lupus in a patient with systemic lupus erythematosus.

A man in his 70s with known systemic lupus erythematosus (SLE) was admitted with confusion, worsening proteinuria and cutaneous vasculitis despite adherence to his home immunosuppressive regimen. Admission laboratories were consistent with active lupus. Despite treatment with pulse-dose glucocorticoids and intravenous immunoglobulin, he developed worsening mental status and meningeal signs. Investigations revealed cerebrospinal fluid (CSF) neutrophilic and plasmacytic pleocytosis and negative cultures. Empiric treatment for SLE flare with potential neuropsychiatric involvement was continued while workup for altered mental status was ongoing. Ultimately, West Nile encephalitis was diagnosed by CSF serologies, and steroids were tapered. Altered mental status in a patient with SLE has a broad differential, and primary neuropsychiatric SLE should be considered only after exclusion of secondary causes. Although evidence of end-organ SLE activity usually lends support to a neuropsychiatric SLE diagnosis, in this case, serological and clinical evidence of SLE activity may have been triggered by acute viral infection.

Neuroinvasive West Nile Virus Disease in an Elderly Patient with Diffuse Large B-Cell Lymphoma Treated with R-CHOP Therapy: A Case Report

Background: West Nile virus is an arthropod-borne virus (arbovirus) and emerging cause of significant illness in European and Mediterranean countries. West Nile virus infection can cause severe and potentially fatal neurological illnesses, including encephalitis, meningitis, and acute flaccid paralysis. Additionally, immunosuppression, alcohol abuse, old age, and diabetes mellitus are common factors associated with West Nile neuroinvasive disease. Case Report: In August 2018, a 60-year-old male patient with a history of diffuse large B-cell lymphoma initially presented with symptoms including abdominal pain and distention, nausea, and vomiting. Three days after open abdominal surgery due to adhesive small bowel obstruction, he developed fever, prominent tremors, and rapidly progressing flaccid paralysis. The identification of West Nile virus RNA in the serum sample led to the diagnosis of West Nile neuroinvasive disease. Conclusion: Clinicians should evaluate patients with acute flaccid paralysis for the evidence of West Nile neuroinvasive disease. It is particularly important for healthcare providers to consider West Nile neuroinvasive disease in the differential diagnosis of aseptic meningitis, encephalitis, and acute paralysis cases, especially in endemic areas.

EEG in WNV Neuroinvasive Disease.

PURPOSE: Neuroinvasive West Nile virus (WNV) is rare, occurring in less than 1% of those infected, and may manifest as meningitis, encephalitis, and/or acute flaccid paralysis. Patients may present initially with nonspecific symptoms including fevers. Although rare, neuroinvasive WNV is associated with significant morbidity and mortality. The mainstay of treatment is supportive care. Electroencephalography (EEG) allows for identification of nonconvulsive status epilepticus and other epileptiform and nonepileptiform patterns suggestive of underlying cognitive dysfunction. Our aim was to describe specific EEG patterns observed in WNV neuroinvasive disease. METHODS: A retrospective chart review was conducted. West Nile virus was confirmed with serum and/or cerebrospinal fluid markers. Patients with a history of abnormal EEG were excluded. Electroencephalography reports were classified into categories based on the presence of epileptiform activity, focal slowing, generalized periodic discharges with triphasic morphology, and frontally predominant generalized rhythmic delta activity. RESULTS: In our cohort of 34 patients, 60% of focal EEG abnormalities were anterior-predominant, seen as epileptiform discharges, focal slowing, or frontally predominant generalized rhythmic delta activity. Nonepileptiform EEG patterns included nonspecific slowing and generalized periodic discharges with triphasic morphology. Two patients had electrographic seizures, one arising from the frontocentral head region. CONCLUSIONS: EEGs are important in the evaluation of WNV infection to rule out seizures or alternative causes of encephalopathy, and because of the risk of nonconvulsive seizures or status epilepticus in encephalitis. Although an anterior predominance of EEG abnormalities was seen in our cohort, this most likely is more correlative to encephalopathy than WNV itself. Although a specific correlative EEG pattern may not accompany all cases of WNV neuroinvasive disease, WNV should be considered as a possible etiology in patients presenting with an encephalitic or meningitic syndrome in the presence of abnormal EEG findings including encephalopathic patterns, particularly those with anterior predominant EEG changes.

WEST NILE VIRUS INFECTION WITH NEUROLOGICAL DISORDERS: A CASE REPORT AND A BRIEF REVIEW OF THE SITUATION IN BULGARIA.

A case of a 66-year-old man with West Nile neuroinvassive disease manifested with fever, weakness, fatigue, consciousness disorders and underlying diabetes mellitus type 2 and cardiovascular diseases is presented. Laboratory data showed elevated erythrocyte sedimentation rate and fibrinogen. Serological tests revealed West Nile virus specific antibodies of class IgM and IgG in serum. West Nile virus RNA was detected in urine sample. Supportive therapy was applied.

West Nile Neuroinvasive Disease Presenting as Elsberg Syndrome.

INTRODUCTION: Elsberg syndrome (ES) is a rarely recognized cause of cauda equina syndrome and lower thoracic myelitis, mainly linked to reactivation, or occasionally primary, infection with herpes simplex virus type 2. West Nile virus neuroinvasive disease is rarely considered in the differential diagnosis of patients with ES. CASE REPORT: A 63-year-old man with pancreatic cancer in remission and polymyalgia rheumatica on low-dose prednisone presented with a 10-day history of low-back pain and a viral-type illness with low-grade fever, nausea, and vomiting. Days later, he developed left leg monoparesis, neurogenic bladder, and bowel. Magnetic resonance imaging of the lumbar spine revealed a hyperintense signal abnormality within the central spinal cord and conus medullaris with mild swelling of the conus. Cells, proteins, and glucose in cerebrospinal fluid were 67/mm, 70 mg/dL, and 58 mg/dL, respectively. Serology was positive for West Nile virus IgM. Nerve conduction studies and electromyography showed an acute motor neurogenic process affecting left lumbosacral segments. CONCLUSIONS: West Nile virus neuroinvasive disease is an uncommon condition that should be considered in patients with ES. Determining the etiology of ES in the acute setting may avoid unnecessary diagnostic investigations and treatments.

Ocular Manifestations of Mosquito-Transmitted Diseases.

Of the 3,548 known mosquito species, about 100 transmit human diseases. Mosquitoes are distributed globally throughout tropical and temperate regions where standing water sources are available for egg laying and the maturation of larva. Female mosquitoes require blood meals for egg production. This is the main pathway for disease transmission. Mosquitoes carry several pathogenic organisms responsible for significant ocular pathology and vision loss including West Nile, Rift Valley, chikungunya, dengue viruses, various encephalitis viruses, malarial parasites, Francisella tularensis, microfilarial parasites, including Dirofilaria, Wuchereria, and Brugia spp., and human botfly larvae. Health care providers may not be familiar with many of these mosquito-transmitted diseases or their associated ocular findings delaying diagnosis, treatment, and recovery of visual function. This article aims to provide an overview of the ocular manifestations associated with mosquito-transmitted diseases.

Long-term neuromuscular outcomes of west nile virus infection: A clinical and electromyographic evaluation of patients with a history of infection.

INTRODUCTION: Neuromuscular clinical manifestations during acute West Nile virus (WNV) infection are well documented; however, long-term neurologic outcomes still require investigation. METHODS: We conducted a long-term follow-up study in patients with history of WNV infection. Of the 117 patients who participated in neurologic and neurocognitive evaluations, 30 were referred for neuromuscular and electrodiagnostic evaluation based on abnormal findings. RESULTS: We found that 33% of these patients (10 of 30) showed abnormalities on nerve conduction and/or needle electromyography due to primary or secondary outcomes of WNV infection. Most common electrodiagnostic findings and causes of long-term disability were related to anterior horn cell poliomyelitis (WNV poliomyelitis). Electrical data on these patient populations were similar to those observed in chronic poliomyelitis. DISCUSSION: With more than 16,000 cases of WNV neuroinvasive disease reported across the USA since 1999, understanding clinical outcomes from infection will provide a resource for physicians managing long-term care of these patients. Muscle Nerve 57: 77-82, 2018.

An examination of the effect of aerosolized Permanone insecticide on zebra finch susceptibility to West Nile virus.

West Nile virus (WNV) is maintained cryptically primarily in avian (passerine) populations, where it is transmitted by Culex spp. mosquitoes. Mosquito-control measures currently include physical activities to reduce mosquito-breeding sites and the application of mosquito larvicides or aerosolized insecticides to kill adults (adulticides) when arboviral diseases such as WNV or Zika virus are detected in mosquito populations. Organochlorine, organophosphorus, carbamate, and pyrethroid insecticides are often used. Previous work suggests an effect of pyrethroids on the immune system in a variety of vertebrates. We examined the effects of exposure to aerosolized Permanone® 30:30 insecticide (permethrin and piperonyl butoxide in soy oil vehicle) at approximately 103 to 106 times potential environmental concentrations on the response of captive zebra finches (Taeniopygia guttata) to experimental challenge with WNV. Compared to vehicle control birds, WNV outcome was unchanged (65% of birds produced a viremia) in the "low" exposure (9.52 ± 3.13 mg/m3 standard deviation [SD] permethrin) group but reduced in the "high" exposure (mean 376.5 ± 27.9 mg/m3 SD permethrin) group (30% were viremic; p < 0.05). After clearing WNV infection, birds treated with Permanone regained less body mass than vehicle-treated birds (p < 0.001). The present study suggests that exposure to aerosolized Permanone insecticide at levels exceeding typical application rates has the potential to not change or to mildly enhance a bird's resistance to WNV. Environ Toxicol Chem 2017;36:3376-3386. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Stress hormones predict a host superspreader phenotype in the West Nile virus system.

Glucocorticoid stress hormones, such as corticosterone (CORT), have profound effects on the behaviour and physiology of organisms, and thus have the potential to alter host competence and the contributions of individuals to population- and community-level pathogen dynamics. For example, CORT could alter the rate of contacts among hosts, pathogens and vectors through its widespread effects on host metabolism and activity levels. CORT could also affect the intensity and duration of pathogen shedding and risk of host mortality during infection. We experimentally manipulated songbird CORT, asking how CORT affected behavioural and physiological responses to a standardized West Nile virus (WNV) challenge. Although all birds became infected after exposure to the virus, only birds with elevated CORT had viral loads at or above the infectious threshold. Moreover, though the rate of mortality was faster in birds with elevated CORT compared with controls, most hosts with elevated CORT survived past the day of peak infectiousness. CORT concentrations just prior to inoculation with WNV and anti-inflammatory cytokine concentrations following viral exposure were predictive of individual duration of infectiousness and the ability to maintain physical performance during infection (i.e. tolerance), revealing putative biomarkers of competence. Collectively, our results suggest that glucocorticoid stress hormones could directly and indirectly mediate the spread of pathogens.

Pathophysiological mechanisms of Flavivirus infection of the central nervous system.

Flaviviruses are important human pathogens. Transmitted by the bite of infected mosquitoes, Flaviviruses such as West Nile and Japanese encephalitis may reach the central nervous system where they can elicit severe diseases. Their ability to cross the blood-brain-barrier is still poorly understood. The newly emerging Zika Flavivirus on the other hand very rarely reaches the brain of adults, but can infect neural progenitors in the developing central nervous system of fetuses, eliciting devastating congenital malformations including microcephaly. This short review focuses on selected aspects of West Nile, Japanese encephalitis and Zika virus pathophysiological features such as neuroinvasion and neurovirulence, and highlights what we know about some possible mechanisms involved in Flaviviral neuropathogenesis.

A complement-microglial axis drives synapse loss during virus-induced memory impairment.

Over 50% of patients who survive neuroinvasive infection with West Nile virus (WNV) exhibit chronic cognitive sequelae. Although thousands of cases of WNV-mediated memory dysfunction accrue annually, the mechanisms responsible for these impairments are unknown. The classical complement cascade, a key component of innate immune pathogen defence, mediates synaptic pruning by microglia during early postnatal development. Here we show that viral infection of adult hippocampal neurons induces complement-mediated elimination of presynaptic terminals in a murine WNV neuroinvasive disease model. Inoculation of WNV-NS5-E218A, a WNV with a mutant NS5(E218A) protein leads to survival rates and cognitive dysfunction that mirror human WNV neuroinvasive disease. WNV-NS5-E218A-recovered mice (recovery defined as survival after acute infection) display impaired spatial learning and persistence of phagocytic microglia without loss of hippocampal neurons or volume. Hippocampi from WNV-NS5-E218A-recovered mice with poor spatial learning show increased expression of genes that drive synaptic remodelling by microglia via complement. C1QA was upregulated and localized to microglia, infected neurons and presynaptic terminals during WNV neuroinvasive disease. Murine and human WNV neuroinvasive disease post-mortem samples exhibit loss of hippocampal CA3 presynaptic terminals, and murine studies revealed microglial engulfment of presynaptic terminals during acute infection and after recovery. Mice with fewer microglia (Il34(-/-) mice with a deficiency in IL-34 production) or deficiency in complement C3 or C3a receptor were protected from WNV-induced synaptic terminal loss. Our study provides a new murine model of WNV-induced spatial memory impairment, and identifies a potential mechanism underlying neurocognitive impairment in patients recovering from WNV neuroinvasive disease.

Epidemiological and clinical aspects on West Nile virus, a globally emerging pathogen.

BACKGROUND: Since the isolation of West Nile virus (WNV) in 1937, in Uganda, it has spread globally, causing significant morbidity and mortality. While birds serve as amplifier hosts, mosquitoes of the Culex genus function as vectors. Humans and horses are dead end hosts. The clinical manifestations of West Nile infection in humans range from asymptomatic illness to West Nile encephalitis. METHODS: The laboratory offers an array of tests, the preferred method being detection of RNA and serum IgM for WNV, which, if detected, confirms the clinical diagnosis. Although no definitive antiviral therapy and vaccine are available for humans, many approaches are being studied. STUDY: This article will review the current literature of the natural cycle, geographical distribution, virology, replication cycle, molecular epidemiology, pathogenesis, laboratory diagnosis, clinical manifestations, blood donor screening for WNV, treatment, prevention and vaccines.