Viral CNS Infection Research Articles

OCA-B promotes pathogenic maturation of stem-like CD4 + T cells and autoimmune demyelination.

Stem-like T cells selectively contribute to autoimmunity, but the activities that promote their pathogenicity are incompletely understood. Here, we identify the transcription coregulator OCA-B as a driver of the pathogenic maturation of stem-like CD4 + T cell to promote autoimmune demyelination. Using a human multiple sclerosis (MS) patient dataset, we show that POU2AF1 , the gene encoding OCA-B, is elevated in CD4 + T cells from secondary-progressive MS patient lesions. We show that T cell-intrinsic OCA-B loss protects mice from experimental autoimmune encephalomyelitis (EAE) while preserving responses to viral CNS infection. In EAE models driven by antigen reencounter, OCA-B deletion nearly eliminates CNS infiltration, proinflammatory cytokine production and clinical disease. CNS OCA-B-expressing CD4 + T of mice with EAE express an encephalitogenic gene program and preferentially confer disease. In a relapsing-remitting EAE model, OCA-B loss protects mice specifically at relapse. During remission, OCA-B promotes the expression of Tcf7 , Slamf6 , and Sell in proliferating CNS T cell populations. At relapse timepoints, OCA-B loss results in both the accumulation of an immunomodulatory CD4 + T cell population expressing Ccr9 and Bach2 , and loss of pro-inflammatory gene expression from Th17 cells. These results identify OCA-B as a driver of pathogenic CD4 + T cells.

Surveillance of tick-borne encephalitis in emerging risk areas in southern Sweden: a retrospective case finding study

Tick-borne encephalitis (TBE) is an emerging infection causing CNS infection of various severity. Good knowledge of the incidence in the population and defined risk areas is important in risk communication and vaccination recommendations. The aim of this study was to investigate potential underreporting by retrospectively diagnose TBE among patients with viral CNS infections of unknown etiology in a region with emerging risk areas for TBE, and define variables associated with performed TBE serology at the time of infection. Epidemiological data and microbiological diagnostics of cases with viral CNS infection of unknown etiology treated at departments of infectious diseases and pediatrics in Skåne County during 2000–2012 were investigated. Analyses to evaluate variables associated with performed TBE serology at the time of infection were performed. Retrospective TBE serology was performed on stored blood samples when available. TBE serology was already performed at the time of CNS infection in 193 out of 761 cases. Department, type of clinical manifestation, time period of illness, and whether Borrelia serology had been performed were independent variables associated with having had TBE serology performed or not at the time of illness. Only one of 137 cases, where samples could be retrospectively analyzed for TBE, turned out positive. This study shows a low frequency of TBE sampling among patients with meningoencephalitis in a region with emerging risk for TBE. A higher awareness of TBE as differential diagnosis could contribute to earlier detection of new risk areas and adequate preventive advice to the public.

MyD88 signaling by neurons induces chemokines that recruit protective leukocytes to the virus-infected CNS.

Viral encephalitis initiates a series of immunological events in the brain that can lead to brain damage and death. Astrocytes express IFN-β in response to neurotropic infection, whereas activated microglia produce proinflammatory cytokines and accumulate at sites of infection. Here, we observed that neurotropic vesicular stomatitis virus (VSV) infection causes recruitment of leukocytes into the central nervous system (CNS), which requires MyD88, an adaptor of Toll-like receptor and interleukin-1 receptor signaling. Infiltrating leukocytes, and in particular CD8+ T cells, protected against lethal VSV infection of the CNS. Reconstitution of MyD88, specifically in neurons, restored chemokine production in the olfactory bulb as well as leukocyte recruitment into the infected CNS and enhanced survival. Comparative analysis of the translatome of neurons and astrocytes verified neurons as the critical source of chemokines, which regulated leukocyte infiltration of the infected brain and affected survival.

The yield of CSF molecular testing in febrile neonates.

We retrospectively examined the yield of a cerebrospinal fluid (CSF) multiplex real-time PCR assay of febrile young infants undergoing a full sepsis work-up. Eighty infants were included in the study: Forty-nine (61%) neonates and 31 (39%) 29-90day-old patients were included in the study. A viral pathogen was detected in 59% (47/80) of the samples, human enterovirus in 53% (42/80) and Human parechovirus in 6% (5/80). The CSF of nearly half of the subjects with CNS infection was without pleocytosis; all CSF cultures were negative. Multiplex PCR CSF testing enhances the diagnosis of pathogen-specific viral CNS infection among febrile young infants.

Tick-borne encephalitis virus (TBEV) prevalence in field-collected ticks (Ixodes ricinus) and phylogenetic, structural and virulence analysis in a TBE high-risk endemic area in southwestern Germany

BackgroundTick-borne encephalitis (TBE) is the most common viral CNS infection with incidences much higher than all other virus infections together in many risk areas of central and eastern Europe. The Odenwald Hill region (OWH) in southwestern Germany is classified as a TBE risk region and frequent case numbers but also more severe infections have been reported within the past decade. The objective of the present study was to survey the prevalence of tick-borne encephalitis virus (TBEV) in Ixodes ricinus and to associate TBEV genetic findings with TBE infections in the OWH.MethodsTicks were collected by the flagging methods supported by a crowdsourcing project implementing the interested public as collectors to cover completely and collect randomly a 3532 km2 area of the OWH TBE risk region. Prevalence of TBEV in I. ricinus was analysed by reversed transcription quantitative real-time PCR. Phylogeographic analysis was performed to classify OWH TBEV isolates within a European network of known TBEV strains. Mutational sequence analysis including 3D modelling of envelope protein pE was performed and based on a clinical database, a spatial association of TBE case frequency and severity was undertaken.ResultsUsing the crowd sourcing approach we could analyse a total of 17,893 ticks. The prevalence of TBEV in I. ricinus in the OWH varied, depending on analysed districts from 0.12% to 0% (mean 0.04%). Calculated minimum infection rate (MIR) was one decimal power higher. All TBEV isolates belonged to the European subtype. Sequence analysis revealed a discontinuous segregation pattern of OWH isolates with two putative different lineages and a spatial association of two isolates with increased TBE case numbers as well as exceptional severe to fatal infection courses.ConclusionsTBEV prevalence within the OWH risk regions is comparatively low which is probably due to our methodological approach and may more likely reflect prevalence of natural TBEV foci. As for other European regions, TBEV genetics show a discontinuous phylogeny indicating among others an association with bird migration. Mutations within the pE gene are associated with more frequent, severe and fatal TBE infections in the OWH risk region.

Chemokine receptors CCR2 and CX3CR1 regulate viral encephalitis-induced hippocampal damage but not seizures

Viral encephalitis is a major risk factor for the development of seizures, epilepsy, and hippocampal damage with associated cognitive impairment, markedly reducing quality of life in survivors. The mechanisms underlying seizures and hippocampal neurodegeneration developing during and after viral encephalitis are only incompletely understood, hampering the development of preventive treatments. Recent findings suggest that brain invasion of blood-born monocytes may be critically involved in both seizures and brain damage in response to encephalitis, whereas the relative role of microglia, the brain's resident immune cells, in these processes is not clear. CCR2 and CX3CR1 are two chemokine receptors that regulate the responses of myeloid cells, such as monocytes and microglia, during inflammation. We used Ccr2-KO and Cx3cr1-KO mice to understand the role of these receptors in viral encephalitis-associated seizures and neurodegeneration, using the Theiler's virus model of encephalitis in C57BL/6 mice. Our results show that CCR2 as well as CX3CR1 plays a key role in the accumulation of myeloid cells in the CNS and activation of hippocampal myeloid cells upon infection. Furthermore, by using Cx3cr1-creER+/-tdTomatoSt/Wt reporter mice, we show that, with regard to CD45 and CD11b expression, some microglia become indistinguishable from monocytes during CNS infection. Interestingly, the lack of CCR2 or CX3CR1 receptors was associated with almost complete prevention of hippocampal damage but did not prevent seizure development after viral CNS infection. These data are compatible with the hypothesis that CNS inflammatory mechanism(s) other than the infiltrating myeloid cells trigger the development of seizures during viral encephalitis.

Epidemiology and clinical outcomes of viral central nervous system infections

BackgroundCentral nervous system (CNS) viral infections are an important cause of morbidity and mortality. No data are available regarding their epidemiology in Qatar. DesignWe retrospectively evaluated all cerebrospinal fluid findings from January 2011–March 2015 at Hamad Medical Corporation. Those with abnormal CSF finding were included in our study. We excluded those with missing medical records, no clinical evidence of viral CNS infection, or proven bacterial, fungal or tuberculosis CNS infection. CNS clinical findings were classified as meningitis, encephalitis or myelitis. ResultsAmong 7690 patients with available CSF results, 550 cases met the inclusion criteria (meningitis 74.7%; encephalitis 25%; myelitis 0.4%). Two-thirds (65%) were male and 50% were between 16–60 years old. Viral etiology was confirmed in 38% (enterovirus, 44.3%; Epstein-Barr virus, 31%; varicella zoster virus, 12.4%). The estimated incidence was 6.4 per 100,000 population. Two persons died and the rest were discharged to home. Among those with confirmed viral etiology, 83.8% received ceftriaxone (mean duration 7.3±5.2 days), 38% received vancomycin (mean duration 2.7±5.4 days) and 38% received at least one other antibiotic. Intravenous acyclovir was continued for more than 48h in patients with confirmed negative viral etiology (mean duration 5±5.6 days). ConclusionViral etiology is not uncommon among those evaluated for CNS infection in Qatar. Clinical outcomes are excellent in this group of patients. Antibiotics and acyclovir are overly used even when a viral etiology is confirmed. There is a need for clinician education regarding etiology and treatment of viral CNS infections.

CSF herpes virus and autoantibody profiles in the evaluation of encephalitis.

Objective:To report the frequency of coexisting herpes viruses (herpes simplex virus 1 [HSV-1] or HSV-2, varicella zoster virus, Epstein-Barr virus [EBV], cytomegalovirus, or human herpes virus 6 [HHV-6]) and autoantibodies in patients with encephalitis (herpes or autoimmune) in clinical laboratory service.Methods:Three groups were evaluated for herpes viruses and antibodies: group 1—patients whose CSF was positive for a herpes virus by real-time PCR over a period of 6 months; group 2—patients whose CSF was positive for an autoimmune encephalitis–associated antibody over 5 years (e.g., NMDA receptor [NMDA-R] antibody), and the same number of controls without autoimmune/infectious disease; and group 3—incidental autoimmune parainfectious encephalitis cases encountered over 1 year.Results:In group 1, antibodies were detected in 27 of 100 herpes PCR-positive CSF specimens (CSFs), either unclassified neural or nonneural in all but one patient with NMDA-R antibody detected after EBV infection. Antibodies were also detected in 3 of 7 CSFs submitted for repeat PCR testing (unclassified, 2; AMPA receptor, 1). In group 2, herpes viruses were detected in 1 of 77 controls (HHV-6) and 4 of 77 patients with autoimmune encephalitis (EBV, 2; HHV-6, 2); autoantibodies targeted NMDA-R in 3/4 and GABAB-R in 1/4. In group 3, NMDA-R antibody was detected in 7 patients post–HSV-1 encephalitis. Of the remaining 3 patients, 2 had unclassified neural antibodies detected, and one had GABAB-R autoimmunity. Concomitant neoplasms were discovered in 2 patients each from groups 2 and 3.Conclusions:Autoantibodies and herpes virus DNA frequently coexist in encephalitic CSF. Some patients develop parainfectious autoimmunity following viral CNS infection (usually HSV-1 encephalitis). The significance of detecting herpes nucleic acids in others remains unclear.

Interferon gamma protects neonatal neural stem/progenitor cells during measles virus infection of the brain.

BackgroundIn the developing brain, self-renewing neural stem/progenitor cells (NSPC) give rise to neuronal and glial lineages. NSPC survival and differentiation can be altered by neurotropic viruses and by the anti-viral immune response. Several neurotropic viruses specifically target and infect NSPCs, in addition to inducing neuronal loss, which makes it difficult to distinguish between effects on NSPCs that are due to direct viral infection or due to the anti-viral immune response.MethodsWe have investigated the impact of anti-viral immunity on NSPCs in measles virus (MV)-infected neonates. A neuron-restricted viral infection model was used, where NSPCs remain uninfected. Thus, an anti-viral immune response was induced without the confounding issue of NSPC infection. Two-transgenic mouse lines were used: CD46+ mice express the human isoform of CD46, the MV entry receptor, under the control of the neuron-specific enolase promoter; CD46+/IFNγ-KO mice lack the key anti-viral cytokine IFNγ. Multi-color flow cytometry and Western Blot analysis were used to quantify effects on NSPC, neuronal, and glial cell number, and quantify effects on IFNγ-mediated signaling and cell markers, respectively.ResultsFlow cytometric analysis revealed that NSPCs were reduced in CD46+/IFNγ-KO mice at 3, 7, and 10 days post-infection (dpi), but were unaffected in CD46+ mice. Early neurons showed the greatest cell loss at 7 dpi in both genotypes, with no effect on mature neurons and glial cells. Thus, IFNγ protected against NSPC loss, but did not protect young neurons. Western Blot analyses on hippocampal explants showed reduced nestin expression in the absence of IFNγ, and reduced doublecortin and βIII-tubulin in both genotypes. Phosphorylation of STAT1 and STAT2 occurred independently of IFNγ in the hippocampus, albeit with distinct regulation of activation.ConclusionsThis is the first study to demonstrate bystander effects of anti-viral immunity on NSPC function. Our results show IFNγ protects the NSPC population during a neonatal viral CNS infection. Significant loss of NSPCs in CD46+/IFNγ-KO neonates suggests that the adaptive immune response is detrimental to NSPCs in the absence of IFNγ. These results reveal the importance and contribution of the anti-viral immune response to neuropathology and may be relevant to other neuroinflammatory conditions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0571-1) contains supplementary material, which is available to authorized users.

Automated cerebrospinal fluid cell count — New reference ranges and evaluation of its clinical use in central nervous system infections

ObjectivesThe purposes of this study were to establish new reference ranges for leukocytes in the CSF and to examine if the separation of mononuclear cells into lymphocytes and monocytes could be used to differentiate between various CNS infections that present with a similar picture in manual CSF cell counts. Design and methodsThe automated cell counter Siemens ADVIA 2120i was used. For the reference range section, we analyzed CSF from 80 neurologically healthy volunteers. For the differential diagnosis section we analyzed cell counts and hospital records from 175 patients with CSF mononuclear pleocytosis. ResultsCorrelation was good between automated and manual leukocyte counts for samples with erythrocyte counts <250cells/μL. For the neurologically healthy volunteers studied in the reference range section, the 95th percentile was 3.0cells/μL for lymphocytes, 1.0cell/μL for monocytes and 1.0cell/μL for granulocytes. In the differential diagnosis section, comparisons were done between the groups Lyme neuroborreliosis and viral CNS infection. There were no significant differences between these two groups regarding cell counts; neither for lymphocytes, median 58cells/μL vs. 72cells/μL (P=n.s.); nor for monocytes, median 13cells/μL vs. 16cells/μL (P=n.s.); nor for granulocytes, median 1cell/μL vs. 2cells/μL (P=n.s.) ConclusionsWe suggest new CSF cell count reference ranges of <4cells/μL for lymphocytes, <3cells/μL for monocytes and <3cells/μL for granulocytes. The separation of mononuclear cells into lymphocytes and monocytes did not facilitate the discrimination between Lyme neuroborreliosis and viral CNS infection.

Viral CNS infections in children from a malaria-endemic area of Malawi: a prospective cohort study.

SummaryBackgroundFever with reduced consciousness is an important cause of hospital admission of children in sub-Saharan Africa, with high mortality. Cerebral malaria, diagnosed when acute Plasmodium falciparum infection and coma are recorded with no other apparent reason, is one important cause. We investigated whether viruses could also be an important cause of CNS infection in such patients, and examined the relative contribution of viral pathogens and malaria parasitaemia.MethodsWe did a prospective cohort study in Blantyre, Malawi. From March 1, 2002, to Aug 31, 2004, we enrolled children aged between 2 months and 15 years who were admitted to hospital with suspected non-bacterial CNS infections. Children with a cerebrospinal fluid (CSF) white cell count of less than 1000 cells per μL and negative bacterial microscopy and culture were deemed to have suspected viral CNS infection. Blood was examined for asexual forms of P falciparum. PCR was done on CSF or on post-mortem brain biopsy specimens to detect 15 viruses known to cause CNS infection.FindingsFull outcome data were available for 513 children with suspected viral CNS infection, of whom 94 (18%) died. 163 children (32%) had P falciparum parasitaemia, of whom 34 (21%) died. At least one virus was detected in the CNS in 133 children (26%), of whom 43 (33%) died. 12 different viruses were detected; adenovirus was the most common, affecting 42 children; mumps, human herpes virus 6, rabies, cytomegalovirus, herpes simplex virus 1, and enterovirus were also important. 45 (9%) of the 513 children had both parasitaemia and viral infection, including 27 (35%) of 78 diagnosed clinically with cerebral malaria. Children with dual infection were more likely to have seizures than were those with parasitaemia alone, viral infection only, or neither (p<0·0001). 17 (38%) of the 45 children with dual infection died, compared with 26 (30%) of 88 with viral infection only, 17 (14%) of 118 with parasitaemia only, and 34 (13%) of 262 with neither (p<0·0001). Logistic regression showed children with a viral CNS infection had a significantly higher mortality than did those who did not have a viral CNS infection (p=0·001).InterpretationViral CNS infections are an important cause of hospital admission and death in children in Malawi, including in children whose coma might be attributed solely to cerebral malaria. Interaction between viral infection and parasitaemia could increase disease severity.FundingWellcome Trust, US National Institutes of Health, and UK Medical Research Council.

PML therapy: “It's Déjà vu all over again”

PML therapy: “It's Déjà vu all over again”

Case Shows How Lyme Disease Can Mimic New-Onset Panic Disorder

Back to table of contents Previous article Next article Clinical and Research NewsFull AccessCase Shows How Lyme Disease Can Mimic New-Onset Panic DisorderLeslie SinclairLeslie SinclairSearch for more papers by this authorPublished Online:25 Jun 2013https://doi.org/10.1176/appi.pn.2013.6b19AbstractNeuropsychiatric symptoms are commonly misdiagnosed, and delayed treatment for the real cause can lead to long-lasting impairment.Syphilis, caused by the spirochete bacterium Treponema pallidum, has been called the “great imitator” because of its ability to affect numerous systems and confusion with other diseases. At a workshop at APA’s 2013 annual meeting titled “Medical Conditions Mimicking Psychiatric Disorders Versus Psychiatric Disorders Mimicking Medical Conditions: Diagnostic and Treatment Challenges,” presenter Yu Dong, M.D., Ph.D., a psychiatry resident at Baystate Medical Center in Springfield, Mass., detailed the case of another spirochetal imitator: Borrelia burgdorferi, the Lyme disease bacterium.The bite of an Ixodes tick can potentially lead to a host of neuropsychiatric symptoms.PHOTO FUN/ShutterstockDong shared with a packed room the case of a 19-year-old female college sophomore who suffered neuropsychiatric manifestations of early-stage Lyme disease. The patient experienced sustained panic attacks lasting for hours at a time and severely disturbed sleep, and she described a “brain fog” that caused difficulty with concentration and memory and left her feeling detached from reality. She also experienced “stroke-like” symptoms that included blurred vision, facial tingling, and left-sided body numbness. Despite the occurrence of these symptoms within a month after she was exposed to a tick at a baseball field in May 2012, the patient had four negative Lyme test (ELISA) results. Her symptoms continued for several months, as she was given a cardiac workup, which was negative, and a neurologic workup including head CT and MRI of the cervical spine. Results of the neurologic workup—intended to assess whether she might be experiencing a viral CNS infection or atypical migraine—were negative as well. In September, she experienced joint pain and swelling. In December, six months after her symptoms had begun, a Lyme disease specialist performed a Western blot test, finding her positive for three out of 10 bands, and she was finally diagnosed with Lyme disease. Treatment was begun, but the patient’s medical odyssey was not yet over.Despite treatment, her symptoms worsened, with more frequent panic attacks and nighttime awakening attributed to Herxheimer reaction. A Herxheimer reaction is worsening of symptoms during the first few days of antibiotic treatment, presumably due to an inflammatory response to spirochetal lysis and antigen release, explained Dong, who noted that such a reaction can be quite prolonged in cases of Lyme disease. “Patients who are treated with appropriate antibiotics in the early stages of Lyme disease usually recover rapidly and completely,” Dong noted, “but antibiotic treatment may be less effective in the late stages of illness,” making rapid diagnosis imperative to prevent long-term consequences for the patient. Treatment in the late or chronic stage is difficult due to sequestration of the spirochete, especially in the CNS. Untreated infection leads to recurrence of fluctuations of symptoms, triggering specific or nonspecific immunologic responses that can become multisystem symptoms. Neuropsychiatric symptoms may become permanent and irreversible, either from the direct effect of the spirochete in the CNS or from a secondary immune response. Dong said Lyme disease is just one of several medical conditions that can mimic panic disorder—myocardial infarction, cardiac dysrhythmia, asthma, hyperthyroidism, pheochromocytoma, and seizure disorder are some of the others.Lyme disease can be easily missed as a diagnosis because a patient may not have a history of tick exposure or experience the characteristic skin rash, and the multisystem nature of the disease can lead to multiple diagnoses for the patient’s symptoms. Latent asymptomatic infection with Borrelia burgdorferi can also last years before symptoms of late infection appear. When Lyme disease is suspected, two-tiered testing (ELISA and Western blot) is recommended, and “most literature recommends clinical diagnosis regardless of serology findings,” said Dong. ■ ISSUES NewArchived

Foxp3+ Regulatory T Cells Control Persistence of Viral CNS Infection

We earlier established a model of a persistent viral CNS infection using two week old immunologically normal (genetically unmodified) mice and recombinant measles virus (MV). Using this model infection we investigated the role of regulatory T cells (Tregs) as regulators of the immune response in the brain, and assessed whether the persistent CNS infection can be modulated by manipulation of Tregs in the periphery. CD4+ CD25+ Foxp3+ Tregs were expanded or depleted during the persistent phase of the CNS infection, and the consequences for the virus-specific immune response and the extent of persistent infection were analyzed. Virus-specific CD8+ T cells predominantly recognising the H-2Db-presented viral hemagglutinin epitope MV-H22–30 (RIVINREHL) were quantified in the brain by pentamer staining. Expansion of Tregs after intraperitoneal (i.p.) application of the superagonistic anti-CD28 antibody D665 inducing transient immunosuppression caused increased virus replication and spread in the CNS. In contrast, depletion of Tregs using diphtheria toxin (DT) in DEREG (depletion of regulatory T cells)-mice induced an increase of virus-specific CD8+ effector T cells in the brain and caused a reduction of the persistent infection. These data indicate that manipulation of Tregs in the periphery can be utilized to regulate virus persistence in the CNS.

Should procalcitonin be used as a routine biomarker of bacterial infection?

I read with great interest the article by Chalupa et al. [1]. The authors have conducted a prospective hospital-based study comparing the potential biomarkers used to diagnose infection in subjects with bacterial and viral infection. The authors concluded that only procalcitonin (PCT) demonstrated superiority over the routine parameters in the differentiation of bacterial from viral infections. Based on this, the authors strongly support the use of the PCT serum level as a routine biomarker of bacterial infection. However, there a few points that need to be highlighted in order for the result to be more meaningful. It is not clear why the authors have used bacterial infection of the lungs (community-acquired bacterial pneumonia [CABP]) and urinary tract (urosepsis) to compare with the viral infections in sites other than these (i.e., of the central nervous system [CNS], liver, etc.). For the results to be meaningful and to supplement clinical decision regarding whether to start or withhold antibiotics in an individual case scenario, the authors could have compared the two infections (either bacterial or viral) at these two sites (either CABP or urosepsis) only. CABP would have been better, as urosepsis is not viral. Moreover, though the authors strongly support the use of PCT as a biomarker for bacterial infection, this issue is still debated [2, 3]. In the recent 2009 H1N1 pandemic, a higher PCT threshold was required to discriminate between bacterial and viral pneumonia, suggesting that severe viral pneumonia alone may elevate PCT [4, 5]. In another important study, 22/23 of patients with community-acquired pneumonia (CAP) with positive serology (three being atypical pneumonia and the rest were viral) were given antibiotics per their PCT algorithm [6]. Patients with atypical pneumonia (due to Mycoplasma and Chlamydia) may have low PCT levels [7]. Even patients who were bacteremic from various sources can have lower PCT levels (\0.5 ng/ml), as found in a recent study [8]. As PCT levels are documented to distinguish viral from bacterial meningitis [9, 10], the authors could have compared the PCT levels between viral or bacterial CNS infection (meningitis or encephalitis) instead of CABP or urosepsis. Another important observation that is not even included in the discussion is that, if PCT is a sensitive indicator of bacterial infection, then why there is a significant difference in the levels of PCT between patients with CABP and urosepsis (as both are presumed to be bacterial), as shown in Table 3 of the paper. As the isolated value of PCT in discriminating between bacterial and viral infection is still not clear, advanced molecular diagnostics should possibly be used to validate the ability of the serum PCT in this regard. In addition, such analysis should be able to clarify PCT responses in mixed viral and bacterial infections, which are detailed elsewhere [11]. If both pathogens (viral and bacterial) are identified, PCT levels should assist in the interpretation of the result also (e.g., colonization with one organism ersus infection with another and vice versa). In spite of all these limitations, PCT serum levels have several advantages when compared with the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level as a biomarker for invasive bacterial disease, and I congratulate the authors for adding further data to support the use of PCT in the diagnosis of bacterial infection. R. R. Das (&) Department of Pediatrics, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India e-mail: dr_rashmipgi@yahoo.com

T helper cell- and CD40-dependent germline IgM prevents chronic virus-induced demyelinating disease

Generation of antiviral IgM is usually considered as a marker of a short-lived initial antibody response that is replaced by hypermutated and more-efficient IgG. However, once viruses have established a particular niche for their persistence (e.g., within the CNS), the immune system has to specifically mobilize a broad range of antimicrobial effectors to contain the pathogen in the long term. Infection of the CNS with the mouse hepatitis virus (MHV) provides a unique model situation in which the extent of inflammatory CNS disease is determined by the balance between antiviral immune control, viral replication, and immune-mediated damage. We show here that whereas antibody- or B cell-deficient mice failed to contain MHV CNS infection and developed progressive demyelinating disease, germline IgM produced in activation-induced cytidine deaminase-deficient mice (aicda(-/-)) provided long-term protection against the chronic multiple sclerosis-like disease. Furthermore, we found that appropriate B-cell activation within the CNS-draining lymph node and subsequent CXCR3-mediated migration of antiviral IgM-secreting cells to the infected CNS was dependent on CD40-mediated interaction of B cells with T helper cells. These data indicate that the CD40-mediated collaboration of T and B cells is critical to secure neuroprotective IgM responses during viral CNS infection.

The effect of B-cell depletion in Theiler's viral model of multiple sclerosis (107.17)

Abstract Introduction: B cell depletion (BCD) has been utilized to treat relapsing-remitting multiple sclerosis (MS), but it is also not clear whether BCD ameliorates disability progression. We used an anti-mouse CD20 mAb (5D2), and tested its effects in Theiler’s murine encephalomyelitis virus-induced demyelinating disease (TIDD), a viral CNS infection considered the best experimental animal model of disability progression in MS. Methods: SJL mice were injected intraperitoneally with 5D2 15 days before intracerebral infection of TMEV BeAn strain. 5D2 bioactivity was assessed by flow cytometry assay of CD19+ cells in peripheral blood mononuclear cells (PBMC). Mouse disability was measured by Rotarod, and viral load was measured by real-time reverse transcriptase PCR (RT-PCR) for TMEV RNA. Antibody levels were determined in mouse sera and CSF by ELISA, and in CNS tissues by real-time RT-PCR for IgG RNA. Results: Bioactivity of 5D2 was confirmed by nearly absent CD19+ cells in the peripheral blood from animals with persistent BCD. Antibody responses in both CNS and peripheral system were suppressed during 5D2 treatment. Relatively higher viral loads were detected in 5D2-treated mice than in PBS animals, and the viral levels correlated negatively to IgG production in the brain. 5D2 caused marked worsening of the early encephalitis, possibly from deletion of a B cell phenotype which downregulates inflammation.

The cytosolic sensors RIG-I and DAI can mediate glial inflammatory responses to neurotropic viruses (162.17)

Abstract The rapid onset of severe neuroinflammation is a defining feature of viral encephalitis. Glial cells are ideally positioned to respond to CNS pathogens and produce potent inflammatory mediators following exposure to neurotropic viruses. However, the mechanisms by which glia perceive viruses remain unclear. Recently the cytosolic proteins RIG-I and DAI have been reported to function as intracellular sensors of RNA and DNA viruses, respectively, but their role in virally-induced neuroinflammation has not been defined. We have shown that primary glial cells express such receptors constitutively and that their expression can be further induced following viral challenge. In the present study we demonstrate that resident CNS cells express these cytosolic pattern recognition receptors in situ and we show that their expression is elevated in murine models of viral encephalitis. Importantly, we have utilized specific ligands for RIG-I and DAI to demonstrate that these viral sensors can mediate the production of inflammatory/neurotoxic mediators by microglia and astrocytes. Furthermore, we have employed siRNA approaches to demonstrate the importance of RIG-I and DAI in such responses to the neurotropic viruses, VSV and HSV-1, respectively. Together, our studies indicate that these novel cytosolic viral sensors may play a critical role in the recognition of viral pathogens and the initiation of the potentially lethal neuroinflammation associated with acute viral CNS infection.

Viral-like brain inflammation during development causes increased seizure susceptibility in adult rats

Viral infections of the CNS and their accompanying inflammation can cause long-term neurological effects, including increased risk for seizures. To examine the effects of CNS inflammation, we infused polyinosinic:polycytidylic acid, intracerebroventricularly to mimic a viral CNS infection in 14 day-old rats. This caused fever and an increase in the pro-inflammatory cytokine, interleukin (IL)-1β in the brain. As young adults, these animals were more susceptible to lithium-pilocarpine and pentylenetetrazol-induced seizures and showed memory deficits in fear conditioning. Whereas there was no alteration in adult hippocampal cytokine levels, we found a marked increase in NMDA (NR2A and C) and AMPA (GluR1) glutamate receptor subunit mRNA expression. The increase in seizure susceptibility, glutamate receptor subunits, and hippocampal IL-1β levels were suppressed by neonatal systemic minocycline. Thus, a novel model of viral CNS inflammation reveals pathophysiological relationships between brain cytokines, glutamate receptors, behaviour and seizures, which can be attenuated by anti-inflammatory agents like minocycline.

Astrocytes produce interferon‐alpha and CXCL10, but not IL‐6 or CXCL8, in aicardi‐Goutières syndrome

Aicardi-Goutières syndrome (AGS) presents as a severe autosomal recessively inherited neurological brain disease. Clinical and neurological manifestations closely resemble those of congenital viral infection and are generally attributed to a perturbation of innate immunity including a long lasting lymphocytosis and production of interferon-alpha (IFNalpha) in the central nervous system. To clarify the innate immune response evoked in these diseases, we used a 30-mer multiplexed luminex system to measure multiple cytokines and growth factors in the cerebrospinal fluid and serum of patients with AGS and viral meningitis or encephalitis, and febrile controls in whom infection could not be substantiated. In addition to the previously described IFNalpha, both AGS and viral diseases were characterized by expression of CXCL10 and CCL2. In contrast to AGS, viral infection resulted in high levels of IL-6 and CXCL8 in the CNS. Postmortem immunohistochemical staining of brain sections showed that in both AGS and viral CNS infection, astrocytes were responsible for the production of cytokines and not the infiltrating leukocytes. In summary, our data indicate that astrocytes are the predominant cell type responsible for the production of IFNalpha and CXCL10 in AGS. Whereas IFNalpha is assumed to be involved in the neurodegeneration, calcifications and seizures in AGS, CXCL10 may act as the chemoattractant responsible for the influx of activated lymphocytes into the brain. The lack of the inflammatory cytokines IL-6 and CXCL8 in AGS suggest that the neuroinflammatory reaction in this disease is distinct from viral disease.