Toscana meningoencephalitis: a comparison to other viral central nervous system infections

Toscana virus (TOSV) meningitis with atypical characteristics: Report of two cases

Toscana virus (TOSV) is an emerging cause of central nervous system (CNS) infections, especially in endemic countries during summer. Cerebrospinal fluid (CSF) is usually clear, with < 500 leukocytes/mm3, normal glucose (> 60 % serum glucose) and normal (< 45 mg/dL) to slightly increased protein levels. Here we present two cases of TOSV meningitis with misleading CSF characteristics observed at Santa Maria Annunziata Hospital (Bagno a Ripoli, Florence, Italy). Case 1 presented with signs and symptoms of meningitis. CSF was opalescent on macroscopic examination, with 1192 cells/mm3, hypoglycorrhachia (30 % serum glucose) and hyperproteinorachia (228.0 mg/dL). TOSV meningitis was confirmed with serology. Case 2 presented with headache, vomiting and mild neck stiffness. CSF was slightly turbid, with 1092 cells/mm3, normal glucose (61 % serum glucose) and slightly increased protein (77.0 mg/dL) levels. TOSV meningitis was confirmed with serology and molecular test on CSF. We performed a literature review including cases of TOSV neuroinvasive infections in which CSF characteristics were reported. Pleocytosis > 500 cells/mm3 was reported in 12/62 (19.4 %) patients, hypoglycorrhachia in 3/62 (4.8 %) patients, mild hyperproteinorachia (45 - 75 mg/dL) in 7/62 (11.3 %) patients and severe hyperproteinorachia (> 75 mg/dL) in 40/62 (64.5 %) patients. TOSV should be considered in the differential diagnosis of CNS infections in endemic areas during the warm season even when CSF examination shows atypical results.

Viral meningitis and encephalitis: an update

PURPOSE OF REVIEW

The most common infectious etiologies of meningitis and encephalitis are viruses. In this review, we will discuss current epidemiology, prevention, diagnosis, and treatment of the most common causes of viral meningitis and encephalitis worldwide.

RECENT FINDINGS

Viral meningitis and encephalitis are increasingly diagnosed as molecular diagnostic techniques and serologies have become more readily available worldwide but recent progress in novel antiviral therapies remains limited. Emerging and re-emerging viruses that have caused endemic or worldwide outbreaks or epidemics are arboviruses (e.g., West Nile virus, Japanese encephalitis, Tick borne encephalitis, Dengue, Zika, Toscana), enteroviruses (e.g., Enterovirus 71, Enterovirus D68), Parechoviruses, respiratory viruses [e.g., severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza, metapneumoviruses, measles, mumps], and herpes viruses [e.g., herpes simplex virus (HSV) type 1 (HSV-1), HSV-2, human herpes (HV) 6, varicella zoster virus (VZV)]. Future efforts should concentrate in increasing availability for those viruses with effective vaccination [e.g., Japanese encephalitis, Tick borne encephalitis, varicella zoster viruses, SARS-CoV-2, influenza], prompt initiation of those with encephalitis with treatable viruses (e.g., HSV-1, VZV), increasing the diagnostic yield by using novel techniques such as metagenomic sequencing and avoiding unnecessary antibiotics in those with viral meningitis or encephalitis.

SUMMARY

We review the current epidemiology, clinical presentation, diagnosis, and treatment of the common causative agents of viral meningitis and encephalitis worldwide.

Toscana virus encephalitis in Southwest Germany: a retrospective study

Background

Toscana virus (TOSV) is an arthropod-borne virus transmitted by phlebotomine sandflies (Phlebotomus sp.) widespread throughout the Mediterranean having the potential to cause meningoencephalitis in humans. In Germany, the vectors of TOSV are introduced recently and become endemic especially in Southwestern Germany. As TOSV is not investigated regularly in patients with meningoencephalitis, cases of TOSV-neuroinvasive disease may remain mostly undetected.

Methods

We conducted a retrospective cohort study on patients with meningoencephalitis without identification of a causal pathogen from 2006 to 2016. Serologic assessment for anti-TOSV-IgG and IgM was performed on serum and CSF. Demographic, clinical and CSF data from TOSV-positive patients were compared to a cohort of patients with meningoencephalitis due to enterovirus. Informed consent was obtained from all included patients.

Results

We found 138 patients with meningoencephalitis without identified causal pathogen. From 98 of these patients CSF and serum was available for further testing. Additionally, we included 27 patients with meningoencephalitis due to enterovirus. We identified two patients with serological confirmed TOSV-neuroinvasive disease (TOSV-IgM and IgG positive, 2%) and two patients with possible TOSV-neuroinvasive disease (isolated TOSV-IgM positive, 2%). Overall, TOSV-neuroinvasive was detected in 4% of our cases with suspected viral meningoencephalitis. None of them had a history of recent travel to an endemic area.

Conclusions

We found cases of TOSV-neuroinvasive disease in our German cohort of patients with meningoencephalitis. As no recent history of travel to an endemic area was reported, it remains probable that these cases resemble autochthonous infections, albeit we cannot draw conclusions regarding the origin of the respective vectors. TOSV could be considered in patients with meningoencephalitis in Germany.

Phlebovirus-associated diseases transmitted by phlebotominae in Spain: Are we at risk?

The genera Phlebovirus transmitted by Diptera belonging to the Psychodidae family are a cause of self-limited febrile syndrome in the Mediterranean basin in summer and autumn. Toscana virus can also cause meningitis and meningoencephalitis. In Spain, Toscana, Granada, Naples, Sicily, Arbia and Arrabida-like viruses have been detected. The almost widespread distribution of Phlebotomus genus vectors, and especially Phlebotomus perniciosus, in which several of these viruses have been detected, makes it very likely that there will be regular human infections in our country, with this risk considered moderate for Toscana virus and low for the other ones, in areas with the highest vector activity. Most of the infections would be undiagnosed, while only Toscana virus would have a greater impact due to the potential severity of the illness.

Phlebovirus-associated diseases transmitted by phlebotominae in Spain: Are we at risk?

The genera Phlebovirus transmitted by Diptera belonging to the Psychodidae family are a cause of self-limited febrile syndrome in the Mediterranean basin in summer and autumn. Toscana virus can also cause meningitis and meningoencephalitis. In Spain, Toscana, Granada, Naples, Sicily, Arbia and Arrabida-like viruses have been detected. The almost widespread distribution of Phlebotomus genus vectors, and especially Phlebotomus perniciosus, in which several of these viruses have been detected, makes it very likely that there will be regular human infections in our country, with this risk considered moderate for Toscana virus and low for the other ones, in areas with the highest vector activity. Most of the infections would be undiagnosed, while only Toscana virus would have a greater impact due to the potential severity of the illness.

Broader Geographical Distribution of Toscana Virus in the Mediterranean Region Suggests the Existence of Larger Varieties of Sand Fly Vectors

Toscana virus (TOSV) is endemic in the Mediterranean basin, where it is transmitted by sand flies. TOSV can infect humans and cause febrile illness as well as neuroinvasive infections affecting the central and peripheral nervous systems. Although TOSV is a significant human pathogen, it remains neglected and there are consequently many gaps of knowledge. Recent seroepidemiology studies and case reports showed that TOSV’s geographic distribution is much wider than was assumed a decade ago. The apparent extension of the TOSV circulation area raises the question of the sandfly species that are able to transmit the virus in natural conditions. Phlebotomus (Ph.)perniciosus and Ph. perfiliewi were historically identified as competent species. Recent results suggest that other species of sand flies could be competent for TOSV maintenance and transmission. Here we organize current knowledge in entomology, epidemiology, and virology supporting the possible existence of additional phlebotomine species such as Ph. longicuspis, Ph. sergenti, Ph. tobbi, Ph. neglectus, and Sergentomyia minuta in TOSV maintenance. We also highlight some of the knowledge gaps to be addressed in future studies.

An update on Toscana virus distribution, genetics, medical and diagnostic aspects

BACKGROUND

Toscana virus is an arbovirus transmitted by sand flies within the Mediterranean area where it can cause febrile illness and neuroinvasive infections during the seasonal circulation period of the vector. Although it is an important cause of meningitis and encephalitis, it remains a neglected virus with limited published data, as demonstrated by <250 peer-reviewed articles since the 1970s.

OBJECTIVE

The last review article on Toscana virus was published in 2012. The aim was to compile peer-reviewed articles to provide an updated review highlighting recent findings to complement previous review articles.

SOURCES

PubMed database was searched using the 'Toscana virus' keyword from 2010 to present. A total of 152 articles were retrieved and identified studies were assessed for novel information on virus genetics, and geographic and medical aspects compared with existing knowledge reported in previous review articles.

CONTENT

Studies addressing medical, veterinary and entomological aspects have provided evidence that Toscana virus is present in North Africa, in the Balkan Peninsula, and in most of the Mediterranean islands. Besides the two previously recognized genetic lineages, a novel evolutionary lineage has been identified in the Balkan Peninsula. Co-circulation of two genetic lineages has been demonstrated in France, in Turkey and in Croatia. In addition to meningitis and meningo-encephalitis, which have been reported for 40 years, various neuroinvasive forms have been recently reported such as Guillain-Barré syndrome, hydrocephalus, myositis, fasciitis, polymyeloradiculopathy, deafness and facial paralysis.

IMPLICATION

Because it is endemic in countries bordering the Mediterranean, physicians should include Toscana virus in the differential diagnosis of patients presenting with febrile illness and/or neurological manifestations.

Circulation of Toscana Virus in a Sample Population of Corsica, France

Sandfly-borne phleboviruses pathogenic to humans, such as Toscana virus (TOSV) and Sandfly Fever Sicilian virus (SFSV), are endemic in the Mediterranean region. In France, several autochthonous cases of TOSV infection have been described, causing either meningitis or encephalitis. The aim of the present study was to investigate the seroprevalence of TOSV and SFSV antibodies in a healthy population from Corsica. In this cross-sectional study, participants were enrolled (i) from a medical staff at the University of Corsica and (ii) from general practitioners of the Corsican Sentinelles Network. The seroprevalence study was based on a virus microneutralization assay. A total of 240 sera were tested. Altogether, 54 sera (22.5%) were confirmed positive for TOSV antibodies, whereas none were positive for SFSV (0/240). The residential district of participants was significantly associated with TOSV seropositivity (p value = 0.005). The rate of the seropositivity against TOSV in our study suggests that the Corsican population is well exposed to the TOSV. These results encourage the implementation of a systematic surveillance system including entomological, microbiological, and medical aspects for the collection of better information on the diseases that are associated with phleboviruses in Corsica and beyond in the regions where these viruses are present.

Diagnostic tools to tackle infectious causes of encephalitis and meningoencephalitis in immunocompetent adults in Europe

BACKGROUND

Encephalitis and meningoencephalitis imply inflammation of the brain parenchyma, and comprise many diagnostic entities, such as various infections and causes of dysimmunity. The cause remains unknown in around 50% of cases.

OBJECTIVES

To summarize the main infectious causes of encephalitis and meningoencephalitis acquired in Europe, and the diagnostic means to identify them.

SOURCES

PubMed, ECDC and WHO websites, personal experience.

CONTENT

The principal infectious causes of encephalitis and meningoencephalitis acquired in Europe in adults are discussed in this review, with special emphasis on the microbiological and imaging diagnostic approaches. The role of electroencephalography in diagnosing encephalitis is also mentioned. Among infections, viruses are more frequent than other pathogen types, and their epidemiology varies according to geographic area. A few bacteria, such as Listeria monocytogenes and Mycobacterium tuberculosis, are also to be considered. In contrast, parasites and fungi are rare encephalitis causes in Europe.

IMPLICATIONS

Identifying the causative pathogen of infectious encephalitis and meningoencephalitis is complex because of the variety of pathogens, the epidemiology of which is determined by geography and environmental factors. Furthermore, despite extensive microbiological testing, many cases of encephalitis remain of unknown origin. Brain magnetic resonance imaging and electroencephalography are useful complementary diagnostic tools, and newer unbiased sequencing technologies might help to fill in the diagnostic gap.

Neglected vector-borne bacterial diseases and arboviruses in the Mediterranean area

Arthropod vectors can transmit pathogenic microorganisms from one vertebrate to another during their blood meal. Although some vector-borne diseases have been eradicated in the Mediterranean area, such as malaria and dengue, recent endemic microorganisms (Toscana virus, Rickettsia spp.) remain neglected even though they cause many more cases. New diagnostic tools and innovative tools for the identification and characterization of vector species and microorganisms have been developed at IHU Méditerranée Infection, either internally or through collaborative and integrated projects. We have detected Rickettsia slovaca as a human pathogen and have described the disease; we have shown that Rickettsia felis can be transmitted by Anopheles mosquitoes; we have emphasized the increasing importance of bedbug (Cimex lectularius) as a potential vector of Bartonella quintana; and we have described the Toscana virus, a major agent of meningitis and meningoencephalitis which was disseminated in North Africa and Central and Eastern Europe, where it frequently cocirculates with a large number of newly described phleboviruses transmitted by sand flies.

Acute versus subacute community-acquired meningitis: Analysis of 611 patients

Community-acquired meningitis can be classified into acute and subacute presentations by the duration of illness of ≤ or >5 days, respectively. There are currently no studies comparing the clinical features, management decisions, etiologies, and outcomes between acute and subacute presentations.It is a retrospective study of adults with community-acquired meningitis hospitalized in Houston, TX between January 2005 and January 2010. An adverse clinical outcome was defined as a Glasgow Outcome Scale score of ≤4.A total of 611 patients were identified, of which 458 (75%) were acute and 153 subacute (25%). The most common etiologies were unknown in 418 (68.4%), viral in 94 (15.4%), bacterial in 47 (7.7%), fungal in 42 patients (6.9%), and other noninfectious etiologies in 6 (1%). Patients with subacute meningitis were more likely to be immunosuppressed or have comorbidities, had fungal etiologies, and had higher rates of hypoglycorrachia and abnormal neurological findings (P <.05). Patients with an acute presentation were more likely to be treated empirically with intravenous antibiotics and had higher cerebrospinal fluid pleocytosis and serum white blood cell counts (P <.05). On logistic regression, age >65 years and abnormal neurological findings were predictive of an adverse clinical outcome in both acute and subacute meningitis, whereas fever was also a significant prognostic factor in acute meningitis. (P <.05).Acute and subacute meningitis differ in regards to clinical presentations, etiologies, laboratory findings, and management decisions, but did not differ in rates of adverse clinical outcomes. Future studies including thoroughly investigated patients with new diagnostic molecular methods may show different results and outcomes.

Detection of Toscana virus from an adult traveler returning to Australia with encephalitis

Toscana virus (TOSV) is identified in sandflies, animals, and humans around the Mediterranean Sea. TOSV has not been reported in Australia. During investigations of cerebrospinal fluid samples from patients with encephalitis, TOSV genetic sequences were identified in a traveler returning to Australia from Europe. TOSV should be considered, especially during May to October, in travelers to Australia who embarked in countries in and around the Mediterranean Sea and who subsequently present for medical care because of neurological symptoms.

Characterization of antibody response in neuroinvasive infection caused by Toscana virus

OBJECTIVES

Among sandfly-borne pathogens, Toscana virus (TOSV) is a prominent cause of summer meningitis in Mediterranean Europe. Here, we assessed the kinetics of anti-TOSV antibodies over time in 41 patients diagnosed with TOSV meningitis or meningoencephalitis in northeastern Italy.

METHODS

Acute and follow-up serum samples were collected up to 20 months after diagnosis of TOSV infection and tested for the presence of specific antibody using immunoenzymatic and indirect immunofluorescence assays. In addition, maturation of anti-TOSV IgG over time was evaluated as well as production of neutralizing antibodies.

RESULTS

Specific IgM and IgG response was present at diagnosis in 100% of patients; TOSV-specific IgM and IgG were detected in patients' sera up to 6 and 20 months after diagnosis, respectively. The avidity index (AI) increased over the first month after infection in 100% of patients and most cases exceeded 60% by Day 30 post infection. The AI subsequently plateaued then declined at 20 months after diagnosis. Finally, neutralization assay to TOSV was performed in 217 sera collected from 41 patients; 69.6% of tested samples resulted in reactive and moderate levels of neutralizing antibodies observed during all phases of infection despite high titres of total anti-TOSV IgG.

CONCLUSIONS

Specific antibody response develops rapidly and is long-lasting for neuroinvasive TOSV infection. Serodiagnosis of neuroinvasive TOSV requires simultaneous detection of specific IgM and IgG. Moderate levels of neutralizing antibodies were maintained over the study period, while the protective role of antibodies lacking neutralizing activity is unclear and requires further evaluation.

Infectious encephalitis: Management without etiological diagnosis 48hours after onset

Introduction

The etiological diagnosis of infectious encephalitis is often not established 48 hours after onset. We aimed to review existing literature data before providing management guidelines.

Method

We performed a literature search on PubMed using filters such as “since 01/01/2000”, “human”, “adults”, “English or French”, and “clinical trial/review/guidelines”. We also used the Mesh search terms “encephalitis/therapy” and “encephalitis/diagnosis”.

Results

With Mesh search terms “encephalitis/therapy” and “encephalitis/diagnosis”, we retrieved 223 and 258 articles, respectively. With search terms “encephalitis and corticosteroid”, we identified 38 articles, and with “encephalitis and doxycycline” without the above-mentioned filters we identified 85 articles. A total of 210 articles were included in the analysis.

Discussion

Etiological investigations must focus on recent travels, animal exposures, age, immunodeficiency, neurological damage characteristics, and potential extra-neurological signs. The interest of a diagnosis of encephalitis for which there is no specific treatment is also to discontinue any empirical treatments initially prescribed. Physicians must consider and search for autoimmune encephalitis.

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.

RNA Encapsidation and Packaging in the Phleboviruses

The Bunyaviridae represents the largest family of segmented RNA viruses, which infect a staggering diversity of plants, animals, and insects. Within the family Bunyaviridae, the Phlebovirus genus includes several important human and animal pathogens, including Rift Valley fever virus (RVFV), severe fever with thrombocytopenia syndrome virus (SFTSV), Uukuniemi virus (UUKV), and the sandfly fever viruses. The phleboviruses have small tripartite RNA genomes that encode a repertoire of 5–7 proteins. These few proteins accomplish the daunting task of recognizing and specifically packaging a tri-segment complement of viral genomic RNA in the midst of an abundance of host components. The critical nucleation events that eventually lead to virion production begin early on in the host cytoplasm as the first strands of nascent viral RNA (vRNA) are synthesized. The interaction between the vRNA and the viral nucleocapsid (N) protein effectively protects and masks the RNA from the host, and also forms the ribonucleoprotein (RNP) architecture that mediates downstream interactions and drives virion formation. Although the mechanism by which all three genomic counterparts are selectively co-packaged is not completely understood, we are beginning to understand the hierarchy of interactions that begins with N-RNA packaging and culminates in RNP packaging into new virus particles. In this review we focus on recent progress that highlights the molecular basis of RNA genome packaging in the phleboviruses.

Sandfly virus seroconversion associated with neurologic presentation

Objective:

To describe the clinical presentation and unique neurologic manifestations of sandfly viruses (SFVs) in the Jerusalem area.

Methods:

We identified all patients with acute seroconversion to SFV at the Hadassah-Hebrew University Medical Centers during the years 2008–2013 and retrospectively collected and analyzed the clinical and imaging data.

Results:

Nine patients (ranging from 1.5 to 85 years old) were identified. Presentation included acute neurologic disease, mostly with fever, change in consciousness and behavior, seizures, headache, meningitis, limb paresis, or myelitis. Eight patients had clinical signs of meningitis, meningoencephalitis, or encephalitis alone. Four patients had myelitis. MRI identified pathologic symmetrical changes in the basal ganglia, thalami, and other deep structures in 5 patients, and additional myelitis of the spine was noted on imaging in 3 patients. Seven patients had long-term follow-up: 4 completely recovered and 3 had remaining neurologic sequelae, among them 1 with permanent severe brain damage.

Conclusion:

Neurologic involvement associated with acute SFV infections is considered to be benign. However, in this series, all 9 patients presented with significant neurologic pathology associated with a unique finding of myelitis and symmetrical basal ganglia, thalami, or white matter involvement. Thus, acute SFV infection should be included in the differential diagnosis in febrile onset of neurologic manifestations and neuroradiologic changes.

Meningitis Caused by Toscana Virus Is Associated with Strong Antiviral Response in the CNS and Altered Frequency of Blood Antigen-Presenting Cells

Toscana virus (TOSV) is a Phlebotomus-transmitted RNA virus and a frequent cause of human meningitis and meningoencephalitis in Southern Europe during the summer season. While evidence for TOSV-related central nervous system (CNS) cases is increasing, little is known about the host defenses against TOSV. We evaluated innate immune response to TOSV by analyzing frequency and activation of blood antigen-presenting cells (APCs) and cytokine levels in plasma and cerebrospinal fluid (CSF) from patients with TOSV neuroinvasive infection and controls. An altered frequency of different blood APC subsets was observed in TOSV-infected patients, with signs of monocytic deactivation. Nevertheless, a proper or even increased responsiveness of toll-like receptor 3 and 7/8 was observed in blood APCs of these patients as compared to healthy controls. Systemic levels of cytokines remained low in TOSV-infected patients, while levels of anti-inflammatory and antiviral mediators were significantly higher in CSF from TOSV-infected patients as compared to patients with other infectious and noninfectious neurological diseases. Thus, the early host response to TOSV appears effective for viral clearance, by proper response to TLR3 and TLR7/8 agonists in peripheral blood and by a strong and selective antiviral and anti-inflammatory response in the CNS.

Toscana virus genome stability: data from a meningoencephalitis case in Mantua, Italy

In July of 2013, samples from a patient with a neurological syndrome were collected from Mantua hospital and sent to the National Reference Laboratory for Arboviruses (National Institute of Health, Rome). On the basis of the symptoms, serological and molecular assays were performed to diagnose either West Nile virus (WNV) or Toscana virus (TOSV) infection. Molecular and serological tests confirmed TOSV infection. Virus isolation was obtained from cerebrospinal fluid. A full genome sequence was determined from this TOSV strain with next-generation sequencing using Ion Torrent technology. Nucleotide and amino acidic sequences grouped phylogenetically with lineage TOSV A and showed a low genome variability.

Afebrile meningoencephalitis with transient central facial paralysis due to Toscana virus infection, southeastern France, 2014 [corrected]

We report a case of meningoencephalitis caused by Toscana virus (TOSV) with central facial paralysis lasting over two days acquired in south-eastern France. The patient was not febrile either before or during the course of the disease. The diagnosis was established by both real-time RT-PCR and virus isolation with complete genome sequencing. This case emphasises the need to consider TOSV in non-febrile neurological syndromes in people living in or having travelled to the Mediterranean area.

Emerging and reemerging neurologic infections

The list of emerging and reemerging pathogens that cause neurologic disease is expanding. Various factors, including population growth and a rise in international travel, have contributed to the spread of pathogens to previously nonendemic regions. Recent advances in diagnostic methods have led to the identification of novel pathogens responsible for infections of the central nervous system. Furthermore, new issues have arisen surrounding established infections, particularly in an increasingly immunocompromised population due to advances in the treatment of rheumatologic disease and in transplant medicine.

Toscana virus infections: a case series from France

Toscana virus (TOSV) is a neglected sandfly-borne pathogen in Mediterranean countries. Although discovered four decades ago, articles that describe the clinical aspects are scarce and consist mostly of case reports, with few series of cases. We studied retrospectively symptomatic TOSV infections in patients hospitalized in Marseille (France) from 2004 to 2011. Seventeen patients were classified as probable or confirmed cases. Fourteen cases (82%) occurred between June and September, and 3 cases in March, April and November. Two cases were potentially imported from Croatia and Tuscany. All patients presented with fever and neurological signs were observed such as aseptic meningitis (n = 6), muscular symptoms (n = 3), or encephalitis (n = 4). The outcome was always favorable. At the acute stage, anti TOSV IgM were observed in 14/17 patients, neutralization tests were positive for 3/8 patients, and RT-PCR confirmed TOSV infections in 5/8 CSF specimens.

Co-circulation of Toscana virus and Punique virus in northern Tunisia: a microneutralisation-based seroprevalence study

Background

In northern Tunisia, the co-circulation of two related sand fly-borne phleboviruses, Toscana virus (TOSV) and Punique virus (PUNV) was previously demonstrated. In contrast to TOSV, a prominent human pathogen, there is no data supporting that PUNV is capable to infect and cause disease to humans. We studied the respective involvement of TOSV and PUNV in human infections in northern Tunisia through a seroprevalence study.

Methods

The presence of TOSV and PUNV neutralising antibodies (NT-Ab) was tested in human sera collected from 5 districts of the governorate of Bizerte, and the titres of NT-Ab were estimated by microneutralisation (MN) assay.

Principal Findings

A total of 1,273 sera were processed. TOSV and PUNV NT-Ab were detected in 522 (41%) and 111 sera (8.72%) respectively. TOSV seroprevalence varied from 17.2% to 59.4% depending on the district. Analysis of TOSV geometric mean titre values demonstrated a constant increase according to the age. The vast majority of sera containing NT-Ab were found to be more reactive toward TOSV than PUNV. Indeed, past infections with PUNV and TOSV were undisputable for 5 and 414 sera, respectively.

Conclusions

PUNV may be capable to infect humans but at a low rate. TOSV is responsible for the vast majority of human infections by sand fly-borne phleboviruses in northern Tunisia. TOSV must be considered by physician and tested in diagnostic laboratories for patients with meningitis and unexplained fever in northern Tunisia.

In northern Tunisia, two different pheboviruses are known to circulate in sand fly population, Toscana virus (TOSV) and Punique virus (PUNV). In contrast to TOSV, a prominent human pathogen, there is no data supporting that PUNV is capable to infect humans and to cause a disease. We studied the respective involvement of TOSV and PUNV in human infections in northern Tunisia through a seroprevalence study. Because TOSV and PUNV are antigenically and genetically closely related, it is difficult to distinguish between them by using broadly reactive serological tests, such as enzyme-linked immunosorbent assay (ELISA). Thus, we developed a method of microneutralisation assay using the two viruses in a comparative manner. A total of 1,273 sera were processed. We provide first evidence to support (i) that Punique virus may be capable to infect humans but at a low rate, (ii) that TOSV, the most prevalent arbovirus in Southern Europe, is responsible for the vast majority of human infections by sand fly-borne phleboviruses in northern Tunisia. Therefore, it is important to consider TOSV as an important pathogen that needs to be included in all virological diagnostic concerning patients with meningitis and unexplained febrile illness originated from Northern Tunisia.

The clinical and laboratory diagnosis of acute meningitis and acute encephalitis

INTRODUCTION

Acute bacterial meningitis (ABM) is a life-threatening infectious disease requiring prompt antimicrobial therapy. ABM must be differentiated from systemic disorders with CNS manifestations that may mimic ABM. ABM should also be differentiated from acute meningoencephalitis (AME) and acute viral encephalitis (AVE). Nonviral causes of AME are treatable. Among the causes of AVE, Herpes simplex encephalitis (HSE) is treatable. This article reviews the clinical diagnostic approach to ABM, AME and AVE.

AREAS COVERED

The differential diagnostic (DDx) approach to ABM, AME and AVE is based on clinical and laboratory findings. A specific pathogen diagnosis is based on serum/cerebrospinal fluid (CSF) tests. This overview presents the diagnostic approach to ABM, AME and AVE in normal hosts (excluding brain abscesses and chronic CNS infections).

EXPERT OPINION

It is time critical to diagnose ABM and begin empiric antimicrobial therapy based on the known/most likely pathogen. The diagnosis of ABM depends on clinical features and the CSF profile. The CSF Gram stain and CSF lactic acid (LA) levels provide the most rapid, reliable and cost-effective tests to diagnose ABM. CSF LA levels are also the best way to diagnose partially treated acute bacterial meningitis (PTABM). In those cases of AME/AVE due to viruses with a CSF profile mimicking ABM, for example, HSE, unelevated CSF LA levels rapidly/reliably rule out ABM as a diagnostic possibility.

Toscana virus NSs protein inhibits the induction of type I interferon by interacting with RIG-I

Toscana virus (TOSV) is a phlebovirus, of the Bunyaviridae family, that is responsible for central nervous system (CNS) injury in humans. Previous data have shown that the TOSV NSs protein is a gamma interferon (IFN-β) antagonist when transiently overexpressed in mammalian cells, inhibiting IRF-3 induction (G. Gori Savellini, F. Weber, C. Terrosi, M. Habjan, B. Martorelli, and M. G. Cusi, J. Gen. Virol. 92:71-79, 2011). In this study, we investigated whether an upstream sensor, which has a role in the signaling cascade leading to the production of type I IFN, was involved. We found a significant decrease in RIG-I protein levels in cells overexpressing TOSV NSs, suggesting that the nonstructural protein interacts with RIG-I and targets it for proteasomal degradation. In fact, the MG-132 proteasome inhibitor was able to restore IFN-β promoter activation in cells expressing NSs, demonstrating the existence of an evasion mechanism based on inhibition of the RIG-I sensor. Furthermore, a C-terminal truncated NSs protein (ΔNSs), although able to interact with RIG-I, did not affect the RIG-I-mediated IFN-β promoter activation, suggesting that the NSs domains responsible for RIG-I-mediated signaling and interaction with RIG-I are mapped on different regions. These results contribute to identify a novel mechanism for bunyaviruses by which TOSV NSs counteracts the early IFN response.