Innate host responses to West Nile virus: Implications for central nervous system immunopathology

Ocular manifestations of West Nile virus infection: A case report and systematic review of the literature

PurposeTo report the case of a patient with ocular West Nile virus infection (WNVI) and to describe the demographics, eye characteristics, and treatment of patients with WNVI reported in the literature.MethodsSystematic literature search using the PubMed MEDLINE database searching for all cases of ocular WNVI published from inception until October 14, 2023. Inclusion criteria were patients with serologic and/or cerebrospinal fluid diagnosis of WNVI with ocular involvement.ResultsA total of 60 patients (111 eyes), including the present case, were included. Most patients were males (57%), diagnosed in the United States (77%), and with a mean age at presentation of 54 years. The median time elapsed between the viral prodrome, and eye symptoms was 7 days. Neurologic involvement was present in 47 (78%) patients. Diabetes mellitus was the most frequent systemic comorbidity (45%). Posterior segment findings were present in 107 (96%) eyes. Multifocal chorioretinal lesions (86%), vitreous inflammation (51%), intraretinal hemorrhages (43%), and retinal vasculitis (21%) were the most frequent findings. Fluorescein angiography was performed in 88 (79%) eyes. Fifty-seven (51%) eyes did not receive treatment. Topical and systemic steroids were prescribed to 35% and 28% of eyes, respectively.ConclusionWNVI should be considered as a potential diagnosis in older patients who exhibit posterior uveitis, especially if they have recently experienced flu-like symptoms and have been exposed to mosquitoes. A comprehensive ocular assessment, which includes a dilated fundus examination and ocular imaging studies, can help raise suspicion for this condition even before serological confirmation is obtained.

Genotype-driven sensitivity of mice to tick-borne encephalitis virus correlates with differential host responses in peripheral macrophages and brain

BACKGROUND

Tick-borne encephalitis (TBE) is the most common tick-borne viral infection in Eurasia. Outcomes range from asymptomatic infection to fatal encephalitis, with host genetics likely playing a role. BALB/c mice have intermediate susceptibility to TBE virus (TBEV) and STS mice are highly resistant, whereas the recombinant congenic strain CcS-11, which carries 12.5% of the STS genome on the BALB/c background, is more susceptible than BALB/c mice. In the present study, we employed these genetically distinct mouse models to investigate the host response to TBEV infection in both peripheral macrophages, one of the initial target cell populations, and the brain, the terminal target organ of the virus.

METHODS

TBEV growth and the production of key cytokines and chemokines were measured and compared in macrophages derived from BALB/c, CcS-11, and STS mice. In addition, brains from these TBEV-infected mouse strains underwent in-depth transcriptomic analysis.

RESULTS

Virus production in BALB/c and CcS-11 macrophages exhibited similar kinetics 24 and 48 h post-infection (hpi), but CcS-11 macrophages yielded significantly higher titers 72 hpi. Macrophages from both sensitive strains demonstrated elevated chemokine and proinflammatory cytokine production upon infection, whereas the resistant strain, STS, showed no cytokine/chemokine activation. Transcriptomic analysis of brain tissue demonstrated that the genetic background of the mouse strains dictated their transcriptional response to infection. The resistant strain exhibited a more robust cell-mediated immune response, whereas both sensitive strains showed a less effective cell-mediated response but increased cytokine signaling and signs of demyelination, with loss of oligodendrocytes.

CONCLUSIONS

Our findings suggest that variations in susceptibility linked to host genetic background correspond with distinct host responses, both in the periphery upon virus entry into the organism and in the brain, the target organ of the virus. These results provide insights into the influence of host genetics on the clinical trajectory of TBE.

The role of IL-1β during human immunodeficiency virus type 1 infection

Interleukin (IL)-1β is a key innate cytokine that is essential for immune activation and promoting the inflammatory process. However, abnormal elevation in IL-1β levels has been associated with unwanted clinical outcomes. IL-1β is the most extensively studied cytokine among the IL-1 family of cytokines and its role in pathology is well established. During the course of human immunodeficiency virus type 1 (HIV-1) infection, the level of this proinflammatory cytokine is increased in different anatomical compartments, particularly in lymphatic tissues, and this elevation is associated with disease progression. The aim of this review is to address the pathological roles play by IL-1β in the light of enhancing HIV-1 replication, driving immune cell depletion, and chronic immune activation. The role of IL-1β in HIV-1 transmission (sexually or vertically 'from mother-to-child') will also be discussed. Additionally, the impact of the available antiretroviral therapy regimens on the levels of IL-1β in HIV-1 treated patients is also discussed. Finally, we will provide a glance on how IL-1β could be targeted as a therapeutic strategy.

West Nile virus IgG antibodies among blood donors in Sudan: a cross-sectional study

while the world is concentrated on fighting SARS-CoV-2, other viruses such as West Nile virus (WNV) attack the communities silently. West Nile Virus (WNV) is established as one of the infectious agents that transmissible blood transfusion. The present study is cross-sectional, conducted in the central blood bank, Khartoum state, Sudan, and aimed to determine WNV IgG antibodies among blood donors.

METHODS

the antibodies of the IgG class against West Nile virus in the serum were determined using the ELISA technique. Ninety blood donors participated in this study.

RESULTS

the results showed that 67(74.4%) of participants had positive IgG for WNV. The majority of positive participants 28/67(41.8%) had an age between 28-37 years followed by an age group 18-27 years 24/67(35.8), the dominant blood group of the positive WNV IgG participants was A+ 26/67 (38.8%) followed by O+ 19/67(28.4%). The result displayed that 40(59.7%) of the positive IgG had donated blood several times and 58 (86.6%) had a blood transfusion. Statistical analysis showed an insignificant association between age group, blood group, blood donation, blood transfusion, and West Nile Virus.

CONCLUSIONS

the high IgG seroprevalence (which indicated previous infection) in the present study suggests high virus circulation in Sudan. This situation proposed that WNF screening test should be part of blood transfusion screening tests in Sudan.

West Nile Neuroinvasive Disease Treated With High-Dose Corticosteroids

West Nile neuroinvasive disease, which includes encephalitis, meningitis, or acute flaccid paralysis, is one of the two most common manifestations of West Nile virus (WNV). According to many national agencies, since 1999, WNV has been one of the most common causes of epidemic viral encephalitis in the United States, especially in the state of California, and it will likely remain an important cause of neurological disease for years to come. To date, the mainstay of treatment for West Nile neuroinvasive disease has been supportive care with no data to support the routine use of any agents. Here, we present a unique case of West Nile encephalitis in a 61-year-old male who was successfully treated with a five-day course of high-dose corticosteroids. Although this rapid improvement could be a mere coincidence, it facilitates the need for further trials to determine if high-dose corticosteroids and other drugs may benefit patients in the treatment of West Nile neuroinvasive disease.

New Targets for Antiviral Therapy: Inhibitory Receptors and Immune Checkpoints on Myeloid Cells

Immune homeostasis is achieved by balancing the activating and inhibitory signal transduction pathways mediated via cell surface receptors. Activation allows the host to mount an immune response to endogenous and exogenous antigens; suppressive modulation via inhibitory signaling protects the host from excessive inflammatory damage. The checkpoint regulation of myeloid cells during immune homeostasis raised their profile as important cellular targets for treating allergy, cancer and infectious disease. This review focuses on the structure and signaling of inhibitory receptors on myeloid cells, with particular attention placed on how the interplay between viruses and these receptors regulates antiviral immunity. The status of targeting inhibitory receptors on myeloid cells as a new therapeutic approach for antiviral treatment will be analyzed.

Therapeutic role of inflammasome inhibitors in neurodegenerative disorders

Neuroinflammation, characterized by the activation of glial cells, is a hallmark in several neurological and neurodegenerative disorders. Inadequate inflammation cannot eliminate the infection of pathogens, while excessive or hyper-reactive inflammation can cause chronic or systemic inflammatory diseases affecting the central nervous system (CNS). In response to a brain injury or pathogen invasion, the pathogen recognition receptors (PRRs) expressed on glial cells are activated via binding to cellular damage-associated molecular patterns (DAMPs) or pathogen-associated molecular patterns (PAMPs). This subsequently leads to the activation of NOD (nucleotide-binding oligomerization domain)-like receptor proteins (NLRs). In neurodegenerative diseases such as HIV-1-associated neurocognitive disorders (HAND), Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS), chronic inflammation is a critical contributing factor for disease manifestation including pathogenesis. Emerging evidence points to the involvement of "inflammasomes", especially the nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing (NLRP) complex in the development of these diseases. The activated NLRP3 results in the proteolytic activation of caspase-1 that facilitates the cleavage of pro-IL-1β and the secretion of IL-1β and IL-18 proinflammatory cytokines. Accordingly, these and other seminal findings have led to the development of NLRP-targeting small-molecule therapeutics as possible treatment options for neurodegenerative disorders. In this review, we will discuss the new advances and evidence-based literature concerning the role of inflammasomes in neurodegenerative diseases, its role in the neurological repercussions of CNS chronic infection, and the examples of preclinical or clinically tested NLRP inhibitors as potential strategies for the treatment of chronic neurological diseases.

Tumor Necrosis Factor-Alpha Signaling May Contribute to Chronic West Nile Virus Post-infectious Proinflammatory State

Background: West Nile virus (WNV) causes a spectrum of human disease ranging from a febrile illness (WNV fever) to severe neuroinvasive disease (meningitis, encephalitis, acute flaccid paralysis). Since WNV gained entry into North America in 1999, clinicians caring for WNV survivors have observed persistent neurological symptoms occurring long-after the production of neutralizing antibodies and clearance of the virus. Accordingly, alternative pathogeneses other than direct viral invasion have been hypothesized to explain these post-infectious symptoms. The dominant hypothesis is that antiviral inflammatory responses triggered initially to clear WNV may persist to promote a post-infectious proinflammatory state.

Methods: In 4 serologically-confirmed WNV patients with persistent post-infectious symptoms (3 WNV fever, 1 neuroinvasive disease), we ordered a comprehensive cytokine panel at weeks 8, 10, 12, and 36 months post-onset of illness, respectively, to better understand the pathophysiology of the protracted symptoms.

Results: All patients had abnormally elevated tumor necrosis factor alpha (TNF-α), a major molecule triggering antiviral cytokines and chronic inflammation in many human autoimmune diseases, but heretofore not reported to be upregulated in human WNV infection. Three patients also had elevations of other proinflammatory proteins. Major symptoms included fatigue, arthralgias, myalgias, generalized or multifocal pain or weakness, imbalance, headaches, cognitive problems, and symptoms of dysautonomia.

Conclusion: The findings provide support for an extended post-infectious proinflammatory state that may contribute to chronic inflammation and long-term morbidity in some WNV survivors and further suggest that TNF-α may play a pathogenic role in initiating this inflammatory environment. Clinical trials may be warranted to determine if TNF-α inhibitors or other immunosuppressive agents can improve patient outcomes.

Cellular microRNA-155 Regulates Virus-Induced Inflammatory Response and Protects against Lethal West Nile Virus Infection

West Nile virus (WNV) is a flavivirus that has disseminated globally as a significant cause of viral encephalitis in humans. MircoRNA-155 (miR-155) regulates various aspects of innate and adaptive immune responses. We previously reported that WNV infection induces upregulation of miR-155 in mice brains. In the current study, we demonstrate the critical role of miR-155 in restricting the pathogenesis of WNV infection in mice. Compared to wild-type (WT) mice, miR-155 knockout mice exhibited significantly higher morbidity and mortality after infection with either a lethal strain, WNV NY99, or a non-lethal strain, WNV Eg101. Increased mortality in miR-155^−/− mice was associated with significantly high WNV burden in the serum and brains. Protein levels of interferon (IFN)-α in the serum and brains were higher in miR-155^−/− mice. However, miR-155^−/− mice exhibited significantly lower protein levels of anti-viral interleukin (IL)-1β, IL-12, IL-6, IL-15, and GM-CSF despite the high viral load. Primary mouse cells lacking miR-155 were more susceptible to infection with WNV compared to cells derived from WT mice. Besides, overexpression of miR-155 in human neuronal cells modulated anti-viral cytokine response and resulted in significantly lower WNV replication. These data collectively indicate that miR-155 restricts WNV production in mouse and human cells and protects against lethal WNV infection in mice.

Inflammatory responses to a pathogenic West Nile virus strain

Background

West Nile virus (WNV) circulates across Australia and was referred to historically as Kunjin virus (WNV_KUN). WNV_KUN has been considered more benign than other WNV strains circulating globally. In 2011, a more virulent form of the virus emerged during an outbreak of equine arboviral disease in Australia.

Methods

To better understand the emergence of this virulent phenotype and the mechanism by which pathogenicity is manifested in its host, cells were infected with either the virulent strain (NSW2012), or less pathogenic historical isolates, and their innate immune responses compared by digital immune gene expression profiling. Two different cell systems were used: a neuroblastoma cell line (SK-N-SH cells) and neuronal cells derived from induced pluripotent stem cells (iPSCs).

Results

Significant innate immune gene induction was observed in both systems. The NSW2012 isolate induced higher gene expression of two genes (IL-8 and CCL2) when compared with cells infected with less pathogenic isolates. Pathway analysis of induced inflammation-associated genes also indicated generally higher activation in infected NSW2012 cells. However, this differential response was not paralleled in the neuronal cultures.

Conclusion

NSW2012 may have unique genetic characteristics which contributed to the outbreak. The data herein is consistent with the possibility that the virulence of NSW2012 is underpinned by increased induction of inflammatory genes.

Associations between the presence of specific antibodies to the West Nile Virus infection and candidate genes in Romanian horses from the Danube delta

The West Nile virus (WNV) is a mosquito-borne flavivirus causing meningoencephalitis in humans and animals. Due to their particular susceptibility to WNV infection, horses serve as a sentinel species. In a population of Romanian semi-feral horses living in the Danube delta region, we have analyzed the distribution of candidate polymorphic genetic markers between anti WNV-IgG seropositive and seronegative horses. Thirty-six SNPs located in 28 immunity-related genes and 26 microsatellites located in the MHC and LY49 complex genomic regions were genotyped in 57 seropositive and 32 seronegative horses. The most significant association (p_corr < 0.0002) was found for genotypes composed of markers of the SLC11A1 and TLR4 genes. Markers of five other candidate genes (ADAM17, CXCR3, IL12A, MAVS, TNFA), along with 5 MHC class I and LY49-linked microsatellites were also associated with the WNV antibody status in this model horse population. The OAS1 gene, previously associated with WNV-induced clinical disease, was not associated with the presence of anti-WNV antibodies.

Lazarus Effect of High Dose Corticosteroids in a Patient With West Nile Virus Encephalitis: A Coincidence or a Clue?

West Nile virus (WNV) causes severe neuroinvasive disease in humans characterized by meningitis, encephalitis, and acute flaccid paralysis (poliomyelitis variant). In neuroinvasive disease, WNV infection of neurons resulting in neuronal loss is generally presumed to be the anatomical substrate for the high morbidity and mortality. However, on a molecular level, WNV infection also results in a significant upregulation of important proinflammatory molecules that have been reported to promote neuroinflammation and cytotoxicity. Currently, there is no specific treatment for the neurological complications of WNV infection. We present a 71-year-old woman who developed WNV infection that rapidly progressed to severe generalized weakness and encephalitis manifesting with bulbar signs (dysphagia, dysarthria) and persistent delirium and stupor. Consciousness remained impaired for 9 days and then she received a 5-day course of high-dose intravenous methylprednisolone (1,000 mg daily). After the first day, voluntary movement and spontaneous eye-opening increased and by the end of the second day, she was awake and responding to commands. Thereafter, she remained awake and responsive. Although the rapid improvement from stupor to wakefulness following treatment with an anti-inflammatory immunosuppressant could merely be coincidence, since these observations are of one patient, it may also provide a clue that in some cases of WNV neuroinvasive disease a post-infectious pro-inflammatory state, rather than neuronal loss, may also contribute to morbidity. Further clinical trials are warranted to determine if high dose corticosteroids and other drugs that can alter this neuro-inflammatory cascade may be potentially beneficial in the treatment of WNV neuroinvasive disease.

Genetic susceptibility to West Nile virus infection in Camargue horses

West Nile virus (WNV) is a mosquito-borne zoonotic neurotropic virus capable to cause lethal meningoencephalitis (WNE) in infected hosts such as birds, horses, and humans. Due to their sensitivity, horses serve as sentinel species in areas at risk. We studied a population of Camargue horses living in Southern France in two zones with endemic WNV circulation where WNV outbreaks were recorded in 2000 and 2003-4. Two sets of microsatellite markers located in MHC and Ly49 genomic regions were genotyped as well as multiple SNPs in ten immunity-related candidate gene regions. Associations between genetic polymorphisms and resistance/susceptibility to WNE were tested. While single marker associations were weak, compound two-gene genotypes of SNPs located within the MAVS, NCR2 and IL-10 genes and microsatellites HMS082 and CZM013 were associated with susceptibility to WNE. Combinations of microsatellite markers CZM009, ABGe17402 and ABGe9019 were associated with simple seroconversion without clinical signs of WNE (resistance). In addition, a distribution of polymorphic markers between WNV-IgG seropositive horses and a control group of WNV-IgG seronegative horses was tested. One SNP in the OAS1 gene (NC_009151.3:g.21961328A>G) was significantly associated with the seropositive phenotype (p_corr = 0.023; OR = 40.5 CI (4.28; 383.26); RR = 8.18 CI (1.27; 52.89) in the Camargue breed. In compound genotypes, SNP markers for SLC11A1, MAVS, OAS1, TLR4, ADAM17 and NCR2 genes and ten microsatellites showed non-random distribution between seropositive and seronegative groups of horses. Further analysis of associated markers could contribute to our understanding of anti-WNV defense mechanisms in horses.

Myeloid Cells during Viral Infections and Inflammation

Myeloid cells represent a diverse range of innate leukocytes that are crucial for mounting successful immune responses against viruses. These cells are responsible for detecting pathogen-associated molecular patterns, thereby initiating a signaling cascade that results in the production of cytokines such as interferons to mitigate infections. The aim of this review is to outline recent advances in our knowledge of the roles that neutrophils and inflammatory monocytes play in initiating and coordinating host responses against viral infections. A focus is placed on myeloid cell development, trafficking and antiviral mechanisms. Although known for promoting inflammation, there is a growing body of literature which demonstrates that myeloid cells can also play critical regulatory or immunosuppressive roles, especially following the elimination of viruses. Additionally, the ability of myeloid cells to control other innate and adaptive leukocytes during viral infections situates these cells as key, yet under-appreciated mediators of pathogenic inflammation that can sometimes trigger cytokine storms. The information presented here should assist researchers in integrating myeloid cell biology into the design of novel and more effective virus-targeted therapies.

From dengue to Zika: the wide spread of mosquito-borne arboviruses

The worldwide invasion of arthropod-borne viruses (arboviruses) in recent decades is responsible for emerging public health threats. Some factors like climate change, urbanisation and uncontrolled population growth are fuelling their widespread. Arboviruses incorporate a vast collection of genetically diverse viral pathogens including that of dengue, Zika and chikungunya. These viruses are peculiar as they are zoonotic and are a serious harm to the society, with no particular therapy to neutralise their effect. So it is the need of the hour to develop an effective treatment against infections caused by them. This review focuses on some of the common families of mosquito-borne arboviruses and their most known members that are a threat to mankind and discusses their genome organisation, worldwide spread and negative influence on public health.

IRF5 regulates unique subset of genes in dendritic cells during West Nile virus infection

Pathogen recognition receptor (PRR) signaling is critical for triggering innate immune activation and the expression of immune response genes, including genes that impart restriction against virus replication. RIG-I-like receptors and TLRs are PRRs that signal immune activation and drive the expression of antiviral genes and the production of type I IFN leading to induction of IFN-stimulated genes, in part through the interferon regulatory factor (IRF) family of transcription factors. Previous studies with West Nile virus (WNV) showed that IRF3 and IRF7 regulate IFN expression in fibroblasts and neurons, whereas macrophages and dendritic cells (DCs) retained the ability to induce IFN-β in the absence of IRF3 and IRF7 in a manner implicating IRF5 in PRR signaling actions. Here we assessed the contribution of IRF5 to immune gene induction in response to WNV infection in DCs. We examined IRF5-dependent gene expression and found that loss of IRF5 in mice resulted in modest and subtle changes in the expression of WNV-regulated genes. Anti-IRF5 chromatin immunoprecipitation with next-generation sequencing of genomic DNA coupled with mRNA analysis revealed unique IRF5 binding motifs within the mouse genome that are distinct from the canonical IRF binding motif and that link with IRF5-target gene expression. Using integrative bioinformatics analyses, we identified new IRF5 primary target genes in DCs in response to virus infection. This study provides novel insights into the distinct and unique innate immune and immune gene regulatory program directed by IRF5.

Identification of genetic variants associated with dengue or West Nile virus disease: a systematic review and meta-analysis

BACKGROUND

Dengue and West Nile viruses are highly cross-reactive and have numerous parallels in geography, potential vector host (Aedes family of mosquitoes), and initial symptoms of infection. While the vast majority (> 80%) of both dengue and West Nile virus infections result in asymptomatic infections, a minority of individuals experience symptomatic infection and an even smaller proportion develop severe disease. The mechanisms by which these infections lead to severe disease in a subset of infected individuals is incompletely understood, but individual host differences including genetic factors and immune responses have been proposed. We sought to identify genetic risk factors that are associated with more severe disease outcomes for both viruses in order to shed light on possible shared mechanisms of resistance and potential therapeutic interventions.

METHODS

We applied a search strategy using four major databases (Medline, PubMed, Embase, and Global Health) to find all known genetic associations identified to date with dengue or West Nile virus disease. Here we present a review of our findings and a meta-analysis of genetic variants identified.

RESULTS

We found genetic variations that are significantly associated with infections of these viruses. In particular we found variation within the OAS1 (meta-OR = 0.83, 95% CI: 0.69-1.00) and CCR5 (meta-OR = 1.29, 95% CI: 1.08-1.53) genes is significantly associated with West Nile virus disease, while variation within MICB (meta-OR = 2.35, 95% CI: 1.68-3.29), PLCE1 (meta-OR = 0.55, 95% CI: 0.42-0.71), MBL2 (meta-OR = 1.54, 95% CI: 1.02-2.31), and IFN-γ (meta-OR = 2.48, 95% CI: 1.30-4.71), is associated with dengue disease.

CONCLUSIONS

Despite substantial heterogeneity in populations studied, genes examined, and methodology, significant associations with genetic variants were found across studies within both diseases. These gene associations suggest a key role for immune mechanisms in susceptibility to severe disease. Further research is needed to elucidate the role of these genes in disease pathogenesis and may reveal additional genetic factors associated with disease severity.

Biochemistry and Molecular Biology of Flaviviruses

Flaviviruses, such as dengue, Japanese encephalitis, tick-borne encephalitis, West Nile, yellow fever, and Zika viruses, are critically important human pathogens that sicken a staggeringly high number of humans every year. Most of these pathogens are transmitted by mosquitos, and not surprisingly, as the earth warms and human populations grow and move, their geographic reach is increasing. Flaviviruses are simple RNA-protein machines that carry out protein synthesis, genome replication, and virion packaging in close association with cellular lipid membranes. In this review, we examine the molecular biology of flaviviruses touching on the structure and function of viral components and how these interact with host factors. The latter are functionally divided into pro-viral and antiviral factors, both of which, not surprisingly, include many RNA binding proteins. In the interface between the virus and the hosts we highlight the role of a noncoding RNA produced by flaviviruses to impair antiviral host immune responses. Throughout the review, we highlight areas of intense investigation, or a need for it, and potential targets and tools to consider in the important battle against pathogenic flaviviruses.

Current developments in understanding of West Nile virus central nervous system disease

PURPOSE OF REVIEW

West Nile virus (WNV) is the most important cause of epidemic encephalitis in the United States. We review articles published in the last 18 months related to the epidemiology, immunology, clinical features, and treatment of this disease.

RECENT FINDINGS

There was a resurgence in WNV disease in the United States in 2012. The WNV strain now predominant in the United States (NA/WN02) differs from the initial emergent isolate in 1999 (NY99). However, differences in the genetics of currently circulating United States WNV strains do not explain variations in epidemic magnitude or disease severity. Innate and acquired immunity are critical in control of WNV, and in some cases pathways are central nervous system specific. The clinical features of infection are now well understood, although nonconfirmed observations of chronic viral excretion in urine remain controversial. There is no specific antiviral therapy for WNV, but studies of antivirals specific for other flaviviruses may identify agents with promise against WNV. Phase I and II human WNV vaccine clinical trials have established that well tolerated and immunogenic WNV vaccines can be developed.

SUMMARY

WNV remains an important public health problem. Although recent studies have significantly increased our understanding of host immune and genetic factors involved in control of WNV infection, no specific therapy is yet available. Development of a well tolerated, immunogenic, and effective vaccine against WNV is almost certainly feasible, but economic factors and the lack of predictability of the magnitude and location of outbreaks are problematic for designing phase III trials and ultimate licensure.

West nile virus encephalitis induced opsoclonus-myoclonus syndrome

West Nile virus (WNV) is an arthropod borne neurotropic single stranded RNA flavivirus with <1% developing presenting with neurological disease. Immunocompromised and elderly patients are more prone to developing WNV meningitis or encephalitis. Definitive diagnosis of WNV meningoencephalitis is a combination of clinical suspicion and cerebrospinal fluid (CSF) serology. Forty-eight year old Caucasian female presented with a sudden onset of altered mental status after being found unresponsive. She was confused with intermittent bouts of alertness/lethargy and unintelligible responses to questioning. Her medical problems included endometrial cancer that was in remission after undergoing a total abdominal hysterectomy with bilateral salpingectomy and postoperative chemotherapy with paclitaxel and carboplatin. Pertinent physical examination revealed muscle strength that was significantly decreased, nuchal rigidity and +2 pitting edema of both lower extremities. Computed tomography and magnetic resonance imaging of the brain were negative for any intracranial pathology. CSF analysis was consistent with aseptic meningitis with all CSF serology being negative except for positive WNV antibody. A few days after being admitted she developed involuntary random movements of her eyes and generalized jerking movements (myoclonus). This was determined to be opsoclonus myoclonus syndrome (OMS) induced by the WNV meningoencephalitis. She then received five consecutive days of plasmapheresis with a significant improvement in her neurological status. Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disorder associated with chaotic multidirectional eye movements, myoclonus and less frequently cerebellar ataxia. OMS affects as few as 1 in 10,000,000 people per year. The pathogenesis is not fully understood with the majority of cases of opsoclonus-myoclonus syndrome being idiopathic. According to current medical literature there have only been two previous case reports of opsoclonus myoclonus syndrome associated with WNV encephalitis.

Integrated human surveillance systems of West Nile virus infections in Italy: the 2012 experience

In Italy, a West Nile virus (WNV) surveillance plan was firstly implemented in 2008 and 2009 in two affected regions and, since 2010, according to a national plan, a WNV neuroinvasive disease (WNND) surveillance has to be carried out each year during the period 15 June–30 November, in those regions where WNV circulation has been demonstrated among humans, animals or vectors. Moreover, since WNV can be transmitted to humans even by blood transfusions and organ transplants obtained from infected donors, the national surveillance integrates the blood transfusions and organs transplant surveillances too. The paper describes the results of this integrated human surveillance in Italy in 2012. Overall, in 2012, 28 autochthonous confirmed cases of WNND were reported, 14 blood donations were found WNV positive by Nucleic Acid Amplification Test and no solid organ donors tested positive for WNV. Moreover, 17 cases of WNV fever were confirmed in Veneto region. When comparing the number of WNND cases reported to the surveillance system in previous 4 years (43 cases during the period 2008–2011), with those reported in 2012 an important increase was observed in 2012. The geographic distribution of human cases was consistent with the WNV circulation among animals and vectors. Moreover, the implementation of preventive measures for WNV transmission through blood components allowed the detection of blood donors positive for WNV, avoiding the further spread of the disease. Since surveillance strategies and preventive measures are based on the integration among human, animal and vector control activities, the Italian experience could be considered a good example of collaboration among different sectors of public health in a “one health” perspective.

Reprogramming the host: Modification of cell functions upon viral infection

Viruses and their hosts have co-evolved for million years. In order to successfully replicate their genome, viruses need to usurp the biosynthetic machinery of the host cell. Depending on the complexity and the nature of the genome, replication might involve or not a relatively large subset of viral products, in addition to a number of host cell factors, and take place in several subcellular compartments, including the nucleus, the cytoplasm, as well as virus-induced, rearranged membranes. Therefore viruses need to ensure the correct subcellular localization of their effectors and to be capable of disguising from the cellular defensive mechanisms. In addition, viruses are capable of exploiting host cell activities, by modulating their post-translational modification apparatus, resulting in profound modifications in the function of cellular and viral products. Not surprisingly infection of host cells by these parasites can lead to alterations of cellular differentiation and growing properties, with important pathogenic consequences. In the present hot topic highlight entitled “Reprogramming the host: modification of cell functions upon viral infection”, a number of leading virologists and cell biologist thoroughly describe recent advances in our understanding of how viruses modulate cellular functions to achieve successful replication and propagation at the expenses of human cells.