Beneficial effect of chronic Staphylococcus aureus infection in a model of multiple sclerosis is mediated through the secretion of extracellular adherence protein

Genomic and functional divergence of Staphylococcus aureus strains from atopic dermatitis patients and healthy individuals: insights from global and local scales

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease worldwide and is characterized by a complex interplay with skin microbiota, with Staphylococcus aureus often abnormally more abundant in AD patients than in healthy individuals (HE). S. aureus harbors diverse strains with varied genetic compositions and functionalities, which exhibit differential connections with the severity of AD. However, the differences in S. aureus strains between AD and HE remain unclear, with most variations seen at a specific geographic level, implying spontaneous adaptations rather than systematic distinctions. This study presents genomic and functional differences between these S. aureus strains from AD and HE on both global and local levels. We observed reduced gene content diversity but increased functional variation in the global AD-associated strains. Two additional AD-dominant clusters emerged, with Cluster 1 enriched in transposases and Cluster 2 showcasing genes linked to adaptability and antibiotic resistance. Particularly, robust evidence illustrates that the lantibiotic operon of S. aureus, involved in the biosynthesis of lantibiotics, was acquired via horizontal gene transfer from environmental bacteria. Comparisons of the gene abundance profiles in functional categories also indicate limited zoonotic potential between human and animal isolates. Local analysis mirrored global gene diversity but showed distinct functional variations between AD and HE strains. Overall, this research provides foundational insights into the genomic evolution, adaptability, and antibiotic resistance of S. aureus, with significant implications for clinical microbiology.IMPORTANCEOur study uncovers significant genomic variations in Staphylococcus aureus strains associated with atopic dermatitis. We observed adaptive evolution tailored to the disease microenvironment, characterized by a smaller pan-genome than strains from healthy skin both on the global and local levels. Key functional categories driving strain diversification include "replication and repair" and "transporters," with transposases being pivotal. Interestingly, the local strains predominantly featured metal-related genes, whereas global ones emphasized antimicrobial resistances, signifying scale-dependent diversification nuances. We also pinpointed horizontal gene transfer events, indicating interactions between human-associated and environmental bacteria. These insights expand our comprehension of S. aureus's genetic adaptation in atopic dermatitis, yielding valuable implications for clinical approaches.

Staphylococcus aureus extracellular adherence protein (Eap) reduces immune cell phenotype in developing but not in established atherosclerotic lesions

Atherosclerosis is a chronic, inflammatory disease of the vessel wall where triggered immune cells bind to inflamed endothelium, extravasate and sustain local inflammation. Leukocyte adhesion and extravasation are mediated by adhesion molecules expressed by activated endothelial cells, like intercellular adhesion molecule 1 (ICAM-1). Extracellular adherence protein (Eap) from Staphylococcus aureus binds to a plethora of extracellular matrix proteins, including ICAM-1 and its ligands macrophage-1 antigen (Mac-1, αMβ2) and lymphocyte function-associated antigen 1 (LFA-1, αLβ2), thereby disrupting the interaction between leukocytes and endothelial cells. We aimed to use Eap to inhibit the interaction of leukocytes with activated endothelial cells in settings of developing and established atherosclerosis in apolipoprotein E (ApoE) deficient mice on high-fat diet. In developing atherosclerosis, Eap treatment reduced circulating platelet-neutrophil aggregates as well as infiltration of T cells and neutrophils into the growing plaque, accompanied by reduced formation of neutrophil extracellular traps (NETs). However, plaque size did not change. Intervention treatment with Eap of already established plaques did not result in cellular or morphological plaque changes, whereas T cell infiltration was increased and thereby again modulated by Eap. We conclude that although Eap leads to cellular changes in developing plaques, clinical implications might be limited as patients are usually treated at a more advanced stage of disease progression. Hence, usage of Eap might be an interesting mechanistic tool for cellular infiltration during plaque development in basic research but not a clinical target.

Intracerebral Infection with E. coli Impairs Spatial Learning and Induces Necrosis of Hippocampal Neurons in the Tg2576 Mouse Model of Alzheimer’s Disease

Background:

In patients with Alzheimer’s disease (AD), bacterial infections are often associated with a cognitive decline. Animal models of genuine acute infections with viable bacteria which induce deterioration of neurodegenerative diseases are missing.

Objective:

We assessed the effect of an intracerebral infection with E. coli in a mouse model of AD.

Methods:

13-month-old Tg2576 +/- mice and transgene negative littermates (Tg2576 -/-) received an intracerebral injection with E. coli K1 or saline followed by treatment with ceftriaxone starting 41 h post infection (p.i.) for 5 days. For 4 weeks, mice were monitored for clinical status, weight, motor functions, and neuropsychological status using the Morris water maze. ELISAs, stainings, and immunohistochemistry in brains were performed at the end of the experiment.

Results:

Mortality of the infection was approximately 20%. After 4 weeks, spatial learning of infected Tg2576 +/- mice was compromised compared to non-infected Tg2576 +/- mice (p < 0.05). E. coli infection did not influence spatial learning in Tg2576 -/- mice, or spatial memory in both Tg2576 +/- and -/- mice within 4 weeks p.i.. Necrosis of hippocampal neurons was induced in infected compared to non-infected Tg2576 +/- mice 4 weeks p.i., whereas brain concentrations of Aβ_1–40, Aβ_1–42, and phosphoTau as well as axonal damage and microglia density were not altered.

Conclusion:

Here, we proved in principle that a genuine acute bacterial infection can worsen cognitive functions of AD mice. Mouse models of subacute systemic infections are needed to develop new strategies for the treatment of bacterial infections in patients with AD in order to minimize their cognitive decline.

Interactions between the foreign body reaction and Staphylococcus aureus biomaterial-associated infection. Winning strategies in the derby on biomaterial implant surfaces

Biomaterial-associated infections (BAIs) are an increasing problem where antibiotic therapies are often ineffective. The design of novel strategies to prevent or combat infection requires a better understanding of how an implanted foreign body prevents the immune system from eradicating surface-colonizing pathogens. The objective of this review is to chart factors resulting in sub-optimal clearance of Staphylococcus aureus bacteria involved in BAIs. To this end, we first describe three categories of bacterial mechanisms to counter the host immune system around foreign bodies: direct interaction with host cells, modulation of intercellular communication, and evasion of the immune system. These mechanisms take place in a time frame that differentiates sterile foreign body reactions, BAIs, and soft tissue infections. In addition, we identify experimental interventions in S. aureus BAI that may impact infectious mechanisms. Most experimental treatments modulate the host response to infection or alter the course of BAI through implant surface modulation. In conclusion, the first week after implantation and infection is crucial for the establishment of an S. aureus biofilm that resists the local immune reaction and antibiotic treatment. Although established and chronic S. aureus BAI is still treatable and manageable, the focus of interventions should lie on this first period.

Bioinformatics and system biology approaches to identify pathophysiological impact of COVID-19 to the progression and severity of neurological diseases

The Coronavirus Disease 2019 (COVID-19) still tends to propagate and increase the occurrence of COVID-19 across the globe. The clinical and epidemiological analyses indicate the link between COVID-19 and Neurological Diseases (NDs) that drive the progression and severity of NDs. Elucidating why some patients with COVID-19 influence the progression of NDs and patients with NDs who are diagnosed with COVID-19 are becoming increasingly sick, although others are not is unclear. In this research, we investigated how COVID-19 and ND interact and the impact of COVID-19 on the severity of NDs by performing transcriptomic analyses of COVID-19 and NDs samples by developing the pipeline of bioinformatics and network-based approaches. The transcriptomic study identified the contributing genes which are then filtered with cell signaling pathway, gene ontology, protein-protein interactions, transcription factor, and microRNA analysis. Identifying hub-proteins using protein-protein interactions leads to the identification of a therapeutic strategy. Additionally, the incorporation of comorbidity interactions score enhances the identification beyond simply detecting novel biological mechanisms involved in the pathophysiology of COVID-19 and its NDs comorbidities. By computing the semantic similarity between COVID-19 and each of the ND, we have found gene-based maximum semantic score between COVID-19 and Parkinson's disease, the minimum semantic score between COVID-19 and Multiple sclerosis. Similarly, we have found gene ontology-based maximum semantic score between COVID-19 and Huntington disease, minimum semantic score between COVID-19 and Epilepsy disease. Finally, we validated our findings using gold-standard databases and literature searches to determine which genes and pathways had previously been associated with COVID-19 and NDs.

Multi-Level Analyses of Genome-Wide Association Study to Reveal Significant Risk Genes and Pathways in Neuromyelitis Optica Spectrum Disorder

Background

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disease of the central nervous system and it is understandable that environmental and genetic factors underlie the etiology of NMOSD. However, the susceptibility genes and associated pathways of NMOSD patients who are AQP4-Ab positive and negative have not been elucidated.

Methods

Secondary analysis from a NMOSD Genome-wide association study (GWAS) dataset originally published in 2018 (215 NMOSD cases and 1244 controls) was conducted to identify potential susceptibility genes and associated pathways in AQP4-positive and negative NMOSD patients, respectively (132 AQP4-positive and 83 AQP4-negative).

Results

In AQP4-positive NMOSD cases, five shared risk genes were obtained at chromosome 6 in AQP4-positive NMOSD cases by using more stringent p-Values in both methods (p < 0.05/16,532), comprising CFB, EHMT2, HLA-DQA1, MSH5, and SLC44A4. Fifty potential susceptibility gene sets were determined and 12 significant KEGG pathways were identified. Sixty-seven biological process pathways, 32 cellular-component pathways, and 29 molecular-function pathways with a p-Value of <0.05 were obtained from the GO annotations of the 128 pathways identified. In the AQP4 negative NMOSD group, no significant genes were obtained by using more stringent p-Values in both methods (p < 0.05/16,485). The 22 potential susceptibility gene sets were determined. There were no shared potential susceptibility genes between the AQP4-positive and negative groups, furthermore, four significant KEGG pathways were also identified. Of the GO annotations of the 165 pathways identified, 99 biological process pathways, 37 cellular-component pathways, and 29 molecular-function pathways with a p-Value of <0.05 were obtained.

Conclusion

The potential molecular mechanism underlying NMOSD may be related to proteins encoded by these novel genes in complements, antigen presentation, and immune regulation. The new results may represent an improved comprehension of the genetic and molecular mechanisms underlying NMOSD.

Bacteria induce skin regeneration via IL-1β signaling

Environmental factors that enhance regeneration are largely unknown. The immune system and microbiome are attributed roles in repairing and regenerating structure but their precise interplay is unclear. Here, we assessed the function of skin bacteria in wound healing and wound-induced hair follicle neogenesis (WIHN), a rare adult organogenesis model. WIHN levels and stem cell markers correlate with bacterial counts, being lowest in germ-free (GF), intermediate in conventional specific pathogen-free (SPF), and highest in wild-type mice, even those infected with pathogenic Staphylococcus aureus. Reducing skin microbiota via cage changes or topical antibiotics decreased WIHN. Inflammatory cytokine IL-1β and keratinocyte-dependent IL-1R-MyD88 signaling are necessary and sufficient for bacteria to promote regeneration. Finally, in a small trial, a topical broad-spectrum antibiotic also slowed skin wound healing in adult volunteers. These results demonstrate a role for IL-1β to control morphogenesis and support the need to reconsider routine applications of topical prophylactic antibiotics.

Protective effects of Clostridium butyricum against oxidative stress induced by food processing and lipid-derived aldehydes in Caco-2 cells

The human body is almost always facing the oxidative stress caused by foodborne aldehydes such as glyoxal (GO) and methylglyoxal (MGO), 4-hydroxyhexenal (HHE), and 4-hydroxynonenal (HNE). When these aldehydes build up, they can cause a range of harm. However, a probiotic, Clostridium butyricum, can increase nuclear factor erythroid-2 related factor 2 (Nrf2) and may have the potential to relieve oxidative stress. If C. butyricum is indeed resistant to aldehydes, the advantages (accessibility, convenience, and safety) will be of great significance compared with drugs. Unfortunately, whether C. butyricum can play a role in alleviating toxic effects of foodborne aldehydes in the intestine (the first line of defense against food-derived toxin) was unclear. To investigate these, we measured the viability, ROS, autophagy, and inflammatory cytokine expression of Caco-2 which were co-cultured with C. butyricum and stimulated by the four aldehydes via Nrf2 pathway (Staphylococcus aureus and Enterococcus faecium as controls). Then, we explored the link among C. butyricum, NLRP6, and Nrf2 signaling pathways when facing the stimuli. In the present study, we demonstrated that Clostridium butyricum relieved the oxidative stress induced by the aldehydes in Caco-2. Most interestingly, we found a "complementary" relationship between NLRP6 and Nrf2 in C. butyricum treatment under aldehyde stress. Our research not only makes a contribution to the popularization of C. butyricum as a probiotic-rich food instead of medicines but also sheds new light on the application of subsequent microecological formulation of C. butyricum. KEY POINTS: • The adverse effects are caused in a dose-dependent manner by foodborne aldehydes. • Clostridium butyricum can significantly ameliorate oxidative stress. • There is a "complementary" relationship between the NLRP6 and Nrf2 signaling pathways. • Using Clostridium butyricum foods to alleviate oxidative stress shows great prospects.

Signaling pathways and therapeutic perspectives related to environmental factors associated with multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated demyelinating disorder of unknown etiology. Both genetic-susceptibility and environment exposures, including vitamin D deficiency, Epstein-Barr viral and Herpesvirus (HHV-6) infections are strongly implicated in the activation of T cells and MS-pathogenesis. Despite precise knowledge of how these factors could be operating alone or in combination to facilitate and aggravate the disease progression, it is clear that prolonged induction of inflammatory molecules and recruitment of other immune cells by the activated T cells results in demyelination and axonal damage. It is imperative to understand the risk factors associated with MS progression and how these factors contribute to disease pathology. Understanding of the underlying mechanisms of what factors triggers activation of T cells to attack myelin antigen are important to strategize therapeutics and therapies against MS. Current review provides a detailed literature to understand the role of both pathogenic and non-pathogenic factors on the impact of MS.

Why monkeys do not get multiple sclerosis (spontaneously): An evolutionary approach

The goal of this review is to apply an evolutionary lens to understanding the origins of multiple sclerosis (MS), integrating three broad observations. First, only humans are known to develop MS spontaneously. Second, humans have evolved large brains, with characteristically large amounts of metabolically costly myelin. This myelin is generated over long periods of neurologic development—and peak MS onset coincides with the end of myelination. Third, over the past century there has been a disproportionate increase in the rate of MS in young women of childbearing age, paralleling increasing westernization and urbanization, indicating sexually specific susceptibility in response to changing exposures. From these three observations about MS, a life history approach leads us to hypothesize that MS arises in humans from disruption of the normal homeostatic mechanisms of myelin production and maintenance, during our uniquely long myelination period. This review will highlight under-explored areas of homeostasis in brain development, that are likely to shed new light on the origins of MS and to raise further questions about the interactions between our ancestral genes and modern environments.

Staphylococcus aureus Strain Newman D2C Contains Mutations in Major Regulatory Pathways That Cripple Its Pathogenesis

Staphylococcus aureus is a major human pathogen that imposes a great burden on the health care system. In the development of antistaphylococcal modalities intended to reduce the burden of staphylococcal disease, it is imperative to select appropriate models of S. aureus strains when assessing the efficacy of novel agents. Here, using whole-genome sequencing, we reveal that the commonly used strain Newman D2C from the American Type Culture Collection (ATCC) contains mutations that render the strain essentially avirulent. Importantly, Newman D2C is often inaccurately referred to as simply "Newman" in many publications, leading investigators to believe it is the well-described pathogenic strain Newman. This study reveals that Newman D2C carries a stop mutation in the open reading frame of the virulence gene regulator, agrA In addition, Newman D2C carries a single-nucleotide polymorphism (SNP) in the global virulence regulator gene saeR that results in loss of protein function. This loss of function is highlighted by complementation studies, where the saeR allele from Newman D2C is incapable of restoring functionality to an saeR-null mutant. Additional functional assessment was achieved through the use of biochemical assays for protein secretion, ex vivo intoxications of human immune cells, and in vivo infections. Altogether, our study highlights the importance of judiciously screening for genetic changes in model S. aureus strains when assessing pathogenesis or the efficacy of novel agents. Moreover, we have identified a novel SNP in the virulence regulator gene saeR that directly affects the ability of the protein product to activate S. aureus virulence pathways.IMPORTANCE Staphylococcus aureus is a human pathogen that imposes an enormous burden on health care systems worldwide. This bacterium is capable of evoking a multitude of disease states that can range from self-limiting skin infections to life-threatening bacteremia. To combat these infections, numerous investigations are under way to develop therapeutics capable of thwarting the deadly effects of the bacterium. To generate successful treatments, it is of paramount importance that investigators use suitable models for examining the efficacy of the drugs under study. Here, we demonstrate that a strain of S. aureus commonly used for drug efficacy studies is severely mutated and displays markedly reduced pathogenicity. As such, the organism is an inappropriate model for disease studies.

Infections in neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory astrocytopathy that has both genetic and environmental causes. A growing body of evidence suggests that the presence of several infectious agents correlates with the development of NMOSD. In this review, we summarize studies that either support or present evidence against the hypothesized association between infection and NMOSD. We will also present an overview of potential mechanisms underlying the pathogenesis of NMOSD. Finally, we provide some beneficial properties that infectious elements may have based on "hygiene hypothesis". It is of great clinical significance to further investigate the complex mechanisms by which infections may affect autoimmune diseases to develop better strategies to prevent and treat them, although so far no causal link between infectious agents and NMOSD has been established.

The pathogenesis of Staphylococcus aureus in autoimmune diseases

Autoimmune disease are defined as the attacks on host tissue by the immune system. Several factors, e.g. genetic and environmental triggers (in particular, viruses, bacteria, and other infectious pathogens) play a role in the development of autoimmune diseases. Bacterial infections are related to several autoimmune diseases, e.g. chronic inflammations and demyelination. Nowadays, an estimated 20-30% of the general human population carry Staphylococcus aureus (S. aureus). This organism can asymptomatically colonize healthy individuals. S. aureus carriers show no sign of infection and can thus spread this bacterium in the community. Several studies investigated the potential involvement of this bacterium as the etiological agents of autoimmune diseases. The present review focused on the role of S. aureus infections in the pathogenesis of autoimmune, inflammatory, and demyelinating diseases. Possible modes of the pathogenic action of bacteria are discussed in association with the ways in which S. aureus can initiate or exacerbate autoimmunity.

Integrating genome-wide association studies and gene expression data highlights dysregulated multiple sclerosis risk pathways

BACKGROUND

Much effort has been expended on identifying the genetic determinants of multiple sclerosis (MS). Existing large-scale genome-wide association study (GWAS) datasets provide strong support for using pathway and network-based analysis methods to investigate the mechanisms underlying MS. However, no shared genetic pathways have been identified to date.

OBJECTIVE

We hypothesize that shared genetic pathways may indeed exist in different MS-GWAS datasets.

METHODS

Here, we report results from a three-stage analysis of GWAS and expression datasets. In stage 1, we conducted multiple pathway analyses of two MS-GWAS datasets. In stage 2, we performed a candidate pathway analysis of the large-scale MS-GWAS dataset. In stage 3, we performed a pathway analysis using the dysregulated MS gene list from seven human MS case-control expression datasets.

RESULTS

In stage 1, we identified 15 shared pathways. In stage 2, we successfully replicated 14 of these 15 significant pathways. In stage 3, we found that dysregulated MS genes were significantly enriched in 10 of 15 MS risk pathways identified in stages 1 and 2.

CONCLUSION

We report shared genetic pathways in different MS-GWAS datasets and highlight some new MS risk pathways. Our findings provide new insights on the genetic determinants of MS.

Neurodegeneration in Autoimmune Optic Neuritis Is Associated with Altered APP Cleavage in Neurons and Up-Regulation of p53

Multiple Sclerosis (MS) is a chronic autoimmune inflammatory disease of the central nervous system (CNS). Histopathological and radiological analysis revealed that neurodegeneration occurs early in the disease course. However, the pathological mechanisms involved in neurodegeneration are poorly understood. Myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) in Brown Norway rats (BN-rats) is a well-established animal model, especially of the neurodegenerative aspects of MS. Previous studies in this animal model indicated that loss of retinal ganglion cells (RGCs), the neurons that form the axons of the optic nerve, occurs in the preclinical phase of the disease and is in part independent of overt histopathological changes of the optic nerve. Therefore, the aim of this study was to identify genes which are involved in neuronal cell loss at different disease stages of EAE. Furthermore, genes that are highly specific for autoimmune-driven neurodegeneration were compared to those regulated in RGCs after optic nerve axotomy at corresponding time points. Using laser capture micro dissection we isolated RNA from unfixed RGCs and performed global transcriptome analysis of retinal neurons. In total, we detected 582 genes sequentially expressed in the preclinical phase and 1150 genes in the clinical manifest EAE (P < 0.05, fold-induction >1.5). Furthermore, using ingenuity pathway analysis (IPA), we identified amyloid precursor protein (APP) as a potential upstream regulator of changes in gene expression in the preclinical EAE but neither in clinical EAE, nor at any time point after optic nerve transection. Therefore, the gene pathway analysis lead to the hypothesis that altered cleavage of APP in neurons in the preclinical phase of EAE leads to the enhanced production of APP intracellular domain (AICD), which in turn acts as a transcriptional regulator and thereby initiates an apoptotic signaling cascade via up-regulation of the target gene p53.

Resistant Strains of Enterotoxigenic Staphylococcus aureus; Unknown Risk for Multiple Sclerosis Exacerbation

Background:

Despite all advances in neurological sciences, there are unknown aspects in the epidemiology of multiple sclerosis (MS). Based on this hypothesis, the enterotoxigenic strains of Staphylococcus aureus (S. aureus) are possible risk factors for exacerbations of MS.

Objectives:

The present study was carried out to investigate the role of resistant strains of enterotoxigenic S. aureus in MS exacerbation.

Materials and Methods:

Two-hundred nasal swab samples were collected from non-MS (n = 80), MS stable (n = 60) and MS exacerbation (n = 60) groups. Samples were cultured and those that were S. aureus-positive were analyzed for the presence of enterotoxins, using polymerase chain reaction (PCR). Antimicrobial susceptibility was performed using disk diffusion method.

Results:

Ninety out of 200 nasal samples (45%) were positive for S. aureus. The highest levels of nasal colonization were seen in MS exacerbation group (68.33%). The most commonly detected enterotoxins were sea (30%), sec (15.55%) and seb (11.11%). There were significant differences between S. aureus colonization and type of samples (P = 0.026) and, also, between type of samples and prevalence of enterotoxins (P = 0.022). The highest levels of enterotoxigenic genes were seen in MS exacerbation group. The S. aureus strains had the highest levels of resistance against tetracycline (80%), ampicillin (72.22%), methicillin (66.66%), erythromycin (66.66%), oxacillin (63.33%), trimethoprim-sulfamethoxazole (61.11%) and cotrimoxazole (55.55%).

Conclusions:

Our findings should raise awareness about the role of sea and sec enterotoxins, in resistant strains of S. aureus, as a risk factor for MS exacerbation. It is better to keep MS patients away from polluted environments of hospitals and health centers.

Systemic Escherichia coli infection does not influence clinical symptoms and neurodegeneration in experimental autoimmune encephalomyelitis

Background

Systemic infections can influence the course of multiple sclerosis (MS), especially by driving recurrent acute episodes. The question whether the infection enhances tissue damage is of great clinical importance and cannot easily be assessed in clinical trials. Here, we investigated the effects of a systemic infection with Escherichia coli, a Gram-negative bacterium frequently causing urinary tract infections, on the clinical course as well as on neurodegeneration in experimental autoimmune encephalomyelitis (EAE), an animal model of MS.

Methods

Rats were immunized with myelin oligodendrocyte glycoprotein (MOG_1–125) and challenged intraperitoneally with live E. coli K1 in the preclinical or in the clinical phase of the disease. To ensure the survival of animals, antibiotic treatment with ceftriaxone was initiated 36 h after the infection and continued for 3 consecutive days.

Results

Systemic infection with E. coli did not influence the onset of clinical EAE symptoms or disease severity. Analysis of the optic nerve and retinal ganglion cells revealed no significant changes in the extent of inflammatory infiltrates, demyelination and neurodegeneration after E. coli infection.

Conclusions

We could not confirm the detrimental effect of lipopolysaccharide-induced systemic inflammation, a model frequently used to mimic the bacterial infection, previously observed in animal models of MS. Our results indicate that the effect of an acute E. coli infection on the course of MS is less pronounced than suspected and underline the need for adequate models to test the role of systemic infections in the pathogenesis of MS.