Carbohydrate mimicry between human ganglioside GM1 and Campylobacter jejuni lipooligosaccharide causes Guillain-Barre syndrome

Lipid Involvement in Neurodegenerative Diseases of the Motor System: Insights from Lysosomal Storage Diseases

Lysosomal storage diseases (LSDs) are a heterogeneous group of rare inherited metabolic diseases that are frequently triggered by the accumulation of lipids inside organelles of the endosomal-autophagic-lysosomal system (EALS). There is now a growing realization that disrupted lysosomal homeostasis (i.e., lysosomal cacostasis) also contributes to more common neurodegenerative disorders such as Parkinson disease (PD). Lipid deposition within the EALS may also participate in the pathogenesis of some additional neurodegenerative diseases of the motor system. Here, I will highlight the lipid abnormalities and clinical manifestations that are common to LSDs and several diseases of the motor system, including amyotrophic lateral sclerosis (ALS), atypical forms of spinal muscular atrophy, Charcot-Marie-Tooth disease (CMT), hereditary spastic paraplegia (HSP), multiple system atrophy (MSA), PD and spinocerebellar ataxia (SCA). Elucidating the underlying basis of intracellular lipid mislocalization as well as its consequences in each of these disorders will likely provide innovative targets for therapeutic research.

Acute axonal neuropathy subtype of Guillain Barré syndrome in a French pediatric series: Adequate follow-up may require repetitive electrophysiological studies

Different subtypes of Guillain Barré Syndromes (GBSs) are defined by their electrophysiological characteristics, acute inflammatory demyelinating neuropathy (AIDP), and acute motor/motor-sensory axonal forms (AMAN/AMSAN) with either reversible nerve conduction failure (RCF) or axonal degeneration. Our aim was to describe initial clinical and electrophysiological characteristics of axonal forms of GBS in a pediatric population and their short- and long-term evolution. Electroneuromyogram (ENMG) results were collected at diagnosis and at two months of evolution and interpreted using the recently proposed pattern of RCF vs axonal degeneration. Clinical evaluation was standardized using the GBS disability scale ("GBSds") at diagnosis, and then at 3, 6, and 12 months of evolution. Outcome was compared to those of patients with AIDP diagnosed within the same period. Eleven patients were included, among whom eight patients presenting with AMAN and three with AMSAN. Two subgroups were identified according to severity. Three patients had a severe form (GBSds ≥2 at 12 months), two of them presenting an axonal degeneration on ENMG studies. Seven patients had a less severe form (GBSds ≤1 at 12 months), five of them with RCF on ENMG studies. Axonal forms had a more severe evolution than demyelinating forms (n = 17) at 3 months (median GBSds 3 and 2, respectively), 6 months (2 and 0), and 12 months (1 and 0), (p < 0,05). Axonal forms of GBS in children have a more severe global outcome than demyelinating forms. Axonal degeneration in two successive early ENMGs may be a prognostic factor of poor outcome.

Disturbance of Plasma Lipid Metabolic Profile in Guillain-Barre Syndrome

Guillain-Barre Syndrome (GBS) is an inflammatory disease of the peripheral nervous system. Given that plasma metabolic profiles in GBS patients have never been explored, plasma samples of 38 GBS patients, 22 multiple sclerosis (MS) patients, and 40 healthy controls were analyzed by using untargeted and targeted metabolomics analysis. The untargeted analysis showed that levels of a set of plasma lipid metabolites were significantly decreased in GBS patients compared to the controls. Furthermore, the targeted analysis demonstrated that levels of 41 metabolites in GBS patients were significantly changed compared to either the controls or MS patients. A further metabolic analysis showed that 12 of 41 metabolites were significantly lower in classical GBS patients compared to Miller-Fisher syndrome. Among them, each of PCae C34:0, PCae C42:2, PCae C42:3, and SM C24:0 was inversely correlated with Hughes functional grading scale of GBS patients at both nadir and discharge. Receiver operating characteristic curve analysis of combination of three metabolites (PCaa C42:2, PCae C36:0 and SM C24:0) showed a good discrimination between the GBS and the controls (area under curve = 0.86). This study has demonstrated disruption of lipid metabolites in GBS may be potential biomarkers to indicate disease severity and prognosis of GBS.

Comparative Proteomics Reveals Differences in Host-Pathogen Interaction between Infectious and Commensal Relationship with Campylobacter jejuni

Campylobacter jejuni is the leading food-borne poisoning in industrialized countries. While the bacteria causes disease in humans, it merely colonizes the gut in poultry or pigs, where seems to establish a commensal relationship. Until now, few studies have been conducted to elucidate the relationship between C. jejuni and its different hosts. In this work, a comparative proteomics approach was used to identify the underlying mechanisms involved in the divergent outcome following C. jejuni infection in human and porcine host. Human (INT-407) and porcine (IPEC-1) intestinal cell lines were infected by C. jejuni for 3 h (T3h) and 24 h (T24h). C. jejuni infection prompted an intense inflammatory response at T3h in human intestinal cells, mainly characterized by expression of proteins involved in cell spreading, cell migration and promotion of reactive oxygen species (ROS). Proteomic analysis evidenced significantly regulated biofunctions in human cells related with engulfment and endocytosis, and supported by canonical pathways associated to infection such as caveolar- and clathrin-mediated endocytosis signaling. In porcine IPEC-1 cells, inflammatory response as well as signaling pathways that control cellular functions such as cell migration, endocytosis and cell cycle progression resulted downregulated. These differences in the host response to infection were supported by the different pattern of adhesion and invasion proteins expressed by C. jejuni in human and porcine cells. No marked differences in expression of virulence factors involved in adaptive response and iron acquisition functions were observed. Therefore, the results of this study suggest that both host and pathogen factors are responsible for commensal or infectious character of C. jejuni in different hosts.

Lateral Gene Transfer in the Adaptation of the Anaerobic Parasite Blastocystis to the Gut

Blastocystis spp. are the most prevalent eukaryotic microbes found in the intestinal tract of humans. Here we present an in-depth investigation of lateral gene transfer (LGT) in the genome of Blastocystis sp. subtype 1. Using rigorous phylogeny-based methods and strict validation criteria, we show that ∼2.5% of the genes of this organism were recently acquired by LGT. We identify LGTs both from prokaryote and eukaryote donors. Several transfers occurred specifically in ancestors of a subset of Blastocystis subtypes, demonstrating that LGT is an ongoing process. Functional predictions reveal that these genes are involved in diverse metabolic pathways, many of which appear related to adaptation of Blastocystis to the gut environment. Specifically, we identify genes involved in carbohydrate scavenging and metabolism, anaerobic amino acid and nitrogen metabolism, oxygen-stress resistance, and pH homeostasis. A number of the transferred genes encoded secreted proteins that are potentially involved in infection, escaping host defense, or most likely affect the prokaryotic microbiome and the inflammation state of the gut. We also show that Blastocystis subtypes differ in the nature and copy number of LGTs that could relate to variation in their prevalence and virulence. Finally, we identified bacterial-derived genes encoding NH₃-dependent nicotinamide adenine dinucleotide (NAD) synthase in Blastocystis and other protozoan parasites, which are promising targets for drug development. Collectively, our results suggest new avenues for research into the role of Blastocystis in intestinal disease and unequivocally demonstrate that LGT is an important mechanism by which eukaryotic microbes adapt to new environments.

The epitope sequence of S16, a monoclonal antibody against influenza C virus hemagglutinin-esterase fusion glycoprotein

Aim: S16, a monoclonal antibody against the hemagglutinin-esterase fusion (HEF) glycoprotein of influenza C virus, reacts with SV40 large T antigen (LT) and a host cellular component(s). The aim is to determine the location of S16 linear epitope on LT and the amino acid sequence of S16 epitope. Materials & methods: BHK-21 cells expressing wild-type and mutant LTs, HEFs or GFPs, each of which was tagged with a FLAG epitope, were analyzed by immunoblotting using S16. Results & conclusions: An amino acid sequence 98-FNEENL-103 on LT forms a linear epitope recognized by S16. The sequence of S16 epitope was defined as F[NAT]EE[NYA]L, excluding FAEEAL and FTEEAL. This finding will be of help in identifying a host cellular component(s) crossreactive with S16.

Guillain-Barré Syndrome

Guillain-Barré syndrome is an acute inflammatory immune-mediated polyradiculoneuropathy presenting typically with tingling, progressive weakness, and pain. Variants and formes frustes may complicate recognition. The best known variant is the sensory ataxic form of Miller Fisher syndrome, which also affects the oculomotor nerves and the brain stem. Divergent pathologic mechanisms lead to demyelinating, axonal, or mixed demyelinating-axonal damage. In the demyelinating form, yet to be identified antigens are inferred by complement activation, myelin destruction, and macrophage-activated cleanup. In the axonal and Miller Fisher variants, gangliosides (GM1, GD1a, GQ1b) are targeted by immunoglobulins and share antigenic epitopes with some bacterial and viral antigens. Campylobacter jejuni infection is associated with an axonal-onset variant; affected patients commonly experience more rapid deterioration. Many other antecedent infectious agents have been recognized including the most recently identified, Zika virus. Supportive care remains the mainstay of therapy. Plasma exchange or intravenous immunoglobin hastens recovery. Combination immunotherapy is not more effective, and the efficacy of prolonged immunotherapy is unproven. One in 3 patients will have deterioration severe enough to require prolonged intensive care monitoring or mechanical ventilation. Full recovery is often seen; most patients regain ambulation, even in severe cases, but disability remains in up to 10% and perhaps more. Numerous challenges remain including early identification and control of infectious triggers, improved access of modern neurointensive care worldwide, and translating our understanding of pathogenesis into meaningful preventive or assistive therapies. This review provides a historical perspective at the centenary of the first description of the syndrome, insights into its pathogenesis, triage, initial immunotherapy, and management in the intensive care unit.

Cerebrospinal fluid findings in Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathies

The classic immunologic alteration of the cerebrospinal fluid (CSF) in Guillain-Barré syndrome (GBS), albuminocytologic dissociation, has been known since the original paper by Guillain, Barré, and Strohl. Albuminocytologic dissociation has been also described in other forms of the GBS spectrum, such as axonal motor or motor-sensory forms (AMAN, AMSAN), the anti-GQ1b spectrum of Miller Fisher syndrome, and Bickerstaff brainstem encephalitis. Cytokines, chemokines, antibodies, complement components, and molecules with a putative neuroprotective role or indicating axonal damage have also been examined using different methods. Besides these candidate approaches, proteomics has been recently applied to discover potential biomarkers. The overall results support the immunopathogenesis of GBS, but albuminocytologic dissociation remained the only consistent CSF biomarker supporting the diagnosis of GBS. Chronic inflammatory neuropathies also comprise a heterogeneous group of diseases. Increased protein in the CSF is a supportive factor of chronic inflammatory demyelinating polyneuropathy, especially in the absence of definite electrophysiologic criteria. A number of other markers have also been investigated in the CSF of patients with chronic inflammatory neuropathies, similar to GBS. However, none has been used in supporting diagnosis, differentiating among syndromes, or predicting the clinical course and treatment responses.

Antibodies from multiple sclerosis patients preferentially recognize hyperglucosylated adhesin of non-typeable Haemophilus influenzae

In autoimmune diseases, there have been proposals that exogenous “molecular triggers”, i.e., specific ‘non-self antigens’ accompanying infectious agents, might disrupt control of the adaptive immune system resulting in serious pathologies. The etiology of multiple sclerosis (MS) remains unclear. However, epidemiologic data suggest that exposure to infectious agents may be associated with increased MS risk and progression may be linked to exogenous, bacterially-derived, antigenic molecules, mimicking mammalian cell surface glycoconjugates triggering autoimmune responses. Previously, antibodies specific to a gluco-asparagine (N-Glc) glycopeptide, CSF114(N-Glc), were identified in sera of an MS patient subpopulation. Since the human glycoproteome repertoire lacks this uniquely modified amino acid, we turned our attention to bacteria, i.e., Haemophilus influenzae, expressing cell-surface adhesins including N-Glc, to establish a connection between H. influenzae infection and MS. We exploited the biosynthetic machinery from the opportunistic pathogen H. influenzae (and the homologous enzymes from A. pleuropneumoniae) to produce a unique set of defined glucosylated adhesin proteins. Interestingly we revealed that a hyperglucosylated protein domain, based on the cell-surface adhesin HMW1A, is preferentially recognized by antibodies from sera of an MS patient subpopulation. In conclusion the hyperglucosylated adhesin is the first example of an N-glucosylated native antigen that can be considered a relevant candidate for triggering pathogenic antibodies in MS.

Guillain Barré Syndrome is induced in Non-Obese Diabetic (NOD) mice following Campylobacter jejuni infection and is exacerbated by antibiotics

Campylobacter jejuni is a leading cause of bacterial gastroenteritis linked to several serious autoimmune sequelae such as the peripheral neuropathies Guillain Barré syndrome (GBS) and Miller Fisher syndrome (MFS). We hypothesized that GBS and MFS can result in NOD wild type (WT) mice or their congenic interleukin (IL)-10 or B7-2 knockouts secondary to C. jejuni infection. Mice were gavaged orally with C. jejuni strains HB93-13 and 260.94 from patients with GBS or CF93-6 from a patient with MFS and assessed for clinical neurological signs and phenotypes, anti-ganglioside antibodies, and cellular infiltrates and lesions in gut and peripheral nerve tissues. Significant increases in autoantibodies against single gangliosides (GM1, GQ1b, GD1a) occurred in infected NOD mice of all genotypes, although the isotypes varied (NOD WT had IgG1, IgG3; NOD B7-2^-/- had IgG3; NOD IL-10^-/- had IgG1, IgG3, IgG2a). Infected NOD WT and NOD IL-10^-/- mice also produced anti-ganglioside antibodies of the IgG1 isotype directed against a mixture of GM1/GQ1b gangliosides. Phenotypic tests showed significant differences between treatment groups of all mouse genotypes. Peripheral nerve lesions with macrophage infiltrates were significantly increased in infected mice of NOD WT and IL-10^-/- genotypes compared to sham-inoculated controls, while lesions with T cell infiltrates were significantly increased in infected mice of the NOD B7-2^-/- genotype compared to sham-inoculated controls. In both infected and sham inoculated NOD IL-10^-/- mice, antibiotic treatment exacerbated neurological signs, lesions and the amount and number of different isotypes of antiganglioside autoantibodies produced. Thus, inducible mouse models of post-C. jejuni GBS are feasible and can be characterized based on evaluation of three factors-onset of GBS clinical signs/phenotypes, anti-ganglioside autoantibodies and nerve lesions. Based on these factors we characterized 1) NOD B-7^-/- mice as an acute inflammatory demyelinating polyneuropathy (AIDP)-like model, 2) NOD IL-10^-/- mice as an acute motor axonal neuropathy (AMAN)-like model best employed over a limited time frame, and 3) NOD WT mice as an AMAN model with mild clinical signs and lesions. Taken together these data demonstrate that C. jejuni strain genotype, host genotype and antibiotic treatment affect GBS disease outcomes in mice and that many disease phenotypes are possible.

Concurrency of Guillain-Barre syndrome and acute transverse myelitis: a case report and review of literature

Guillain-Barré syndrome and acute transverse myelitis manifest as demyelinating diseases of the peripheral and central nervous system. Concurrency of these two disorders is rarely documented in literature. A 4-year-old girl presenting with cough, fever, and an impaired walking ability was admitted to hospital. She had no previous complaints in her medical history. A physical examination revealed lack of muscle strength of the lower extremities and deep tendon reflexes. MRI could not be carried out due to technical problems; therefore, both Guillain-Barré syndrome and acute transverse myelitis were considered for the diagnosis. Intravenous immunoglobulin treatment was started as first line therapy. Because this treatment did not relieve the patient's symptoms, spinal MRI was carried out on the fourth day of admission and demyelinating areas were identified. Based on the new findings, the patient was diagnosed with acute transverse myelitis, and high dose intravenous methylprednisolone therapy was started. Electromyography findings were consistent with acute polyneuropathy affecting both motor and sensory fibers. Therefore, the patient was diagnosed with concurrency of Guillain-Barré syndrome and acute transverse myelitis. Interestingly, while concurrency of these 2 disorders is rare, this association has been demonstrated in various recent publications. Progress in diagnostic tests (magnetic resonance imaging and electrophysiological examination studies) has enabled clinicians to establish the right diagnosis. The possibility of concurrent Guillain-Barré syndrome and acute transverse myelitis should be considered if recovery takes longer than anticipated.

Guillain-Barré syndrome: a century of progress

In 1916, Guillain, Barré and Strohl reported on two cases of acute flaccid paralysis with high cerebrospinal fluid protein levels and normal cell counts - novel findings that identified the disease we now know as Guillain-Barré syndrome (GBS). 100 years on, we have made great progress with the clinical and pathological characterization of GBS. Early clinicopathological and animal studies indicated that GBS was an immune-mediated demyelinating disorder, and that severe GBS could result in secondary axonal injury; the current treatments of plasma exchange and intravenous immunoglobulin, which were developed in the 1980s, are based on this premise. Subsequent work has, however, shown that primary axonal injury can be the underlying disease. The association of Campylobacter jejuni strains has led to confirmation that anti-ganglioside antibodies are pathogenic and that axonal GBS involves an antibody and complement-mediated disruption of nodes of Ranvier, neuromuscular junctions and other neuronal and glial membranes. Now, ongoing clinical trials of the complement inhibitor eculizumab are the first targeted immunotherapy in GBS.

Genetic Characteristics and Multiple-PCR Development for Capsular Identification of Specific Serotypes of Campylobacter jejuni

The polysaccharide capsule (CPS) of Campylobacter jejuni is a virulence factor linked to cell surface carbohydrate diversity which mainly determines the serotypes. Thirty-four CPS gene cluster structures have been published and some of them can be distinguished by multiple-PCR. Penner serotypes HS1/44c, HS2, HS4c, HS19, HS23/36c and HS41 are markers for Guillain—Barré syndrome (GBS). The capsules may contribute to GBS susceptibility. Analysis of 18 CPS loci revealed high gene content diversity and a mosaic nature of the capsule loci, which are possibly due to gene gain/loss events, and demonstrated a high degree of conservation of genes within serotypes/serotype complexes. A method of multiple-PCR was developed to distinguish five specific serotypes and three GBS-related serotypes. Primers specific for each capsule type were designed on the basis of paralogs or a unique DNA region of the CPS locus. The multiple-PCR can distinguish the eight serotypes in two PCRs with sensitivity and specificity of 100% using 227 strains of known Penner type. The multiple-PCR method will help to distinguish serotypes simply and rapidly.

Large Sequence Diversity within the Biosynthesis Locus and Common Biochemical Features of Campylobacter coli Lipooligosaccharides

Despite the importance of lipooligosaccharides (LOSs) in the pathogenicity of campylobacteriosis, little is known about the genetic and phenotypic diversity of LOS in Campylobacter coli In this study, we investigated the distribution of LOS locus classes among a large collection of unrelated C. coli isolates sampled from several different host species. Furthermore, we paired C. coli genomic information and LOS chemical composition for the first time to investigate possible associations between LOS locus class sequence diversity and biochemical heterogeneity. After identifying three new LOS locus classes, only 85% of the 144 isolates tested were assigned to a class, suggesting higher genetic diversity than previously thought. This genetic diversity is at the basis of a completely unexplored LOS structural heterogeneity. Mass spectrometry analysis of the LOSs of nine isolates, representing four different LOS classes, identified two features distinguishing C. coli LOS from that of Campylobacter jejuni 2-Amino-2-deoxy-d-glucose (GlcN)-GlcN disaccharides were present in the lipid A backbone, in contrast to the β-1'-6-linked 3-diamino-2,3-dideoxy-d-glucopyranose (GlcN3N)-GlcN backbone observed in C. jejuni Moreover, despite the fact that many of the genes putatively involved in 3-acylamino-3,6-dideoxy-d-glucose (Quip3NAcyl) were apparently absent from the genomes of various isolates, this rare sugar was found in the outer core of all C. coli isolates. Therefore, regardless of the high genetic diversity of the LOS biosynthesis locus in C. coli, we identified species-specific phenotypic features of C. coli LOS that might explain differences between C. jejuni and C. coli in terms of population dynamics and host adaptation.

IMPORTANCE

Despite the importance of C. coli to human health and its controversial role as a causative agent of Guillain-Barré syndrome, little is known about the genetic and phenotypic diversity of C. coli LOSs. Therefore, we paired C. coli genomic information and LOS chemical composition for the first time to address this paucity of information. We identified two species-specific phenotypic features of C. coli LOS, which might contribute to elucidating the reasons behind the differences between C. jejuni and C. coli in terms of population dynamics and host adaptation.

Guillain-Barré syndrome: What have we learnt during one century? A personal historical perspective

We are approaching the centenary of the first description of Guillain-Barré syndrome. The past 30 years had witnessed an amazing progress in the understanding of the immunological and pathological mechanisms of this disorder. We now recognize that Guillain-Barré syndrome is remarkably heterogeneous and under this umbrella term are several variants and subtypes with distinct clinical, electrophysiological and immunopathological features. This review is a historical journey, through a personal perspective, following the milestones that led to the current substantial knowledge of Guillain-Barré syndrome.

Determinants of VH1-46 Cross-Reactivity to Pemphigus Vulgaris Autoantigen Desmoglein 3 and Rotavirus Antigen VP6

Shared VH1-46 gene usage has been described in B cells reacting to desmoglein 3 (Dsg3) in the autoimmune disease pemphigus vulgaris (PV), as well as B cells responding to rotavirus capsid protein VP6. In both diseases, VH1-46 B cells bearing few to no somatic mutations can recognize the disease Ag. This intriguing connection between an autoimmune response to self-antigen and an immune response to foreign Ag prompted us to investigate whether VH1-46 B cells may be predisposed to Dsg3-VP6 cross-reactivity. Focused testing of VH1-46 mAbs previously isolated from PV and rotavirus-exposed individuals indicates that cross-reactivity is rare, found in only one of seven VH1-46 IgG clonotypes. High-throughput screening of IgG B cell repertoires from two PV patients identified no additional cross-reactive clonotypes. Screening of IgM B cell repertoires from one non-PV and three PV patients identified specific cross-reactive Abs in one PV patient, but notably all six cross-reactive clonotypes used VH1-46. Site-directed mutagenesis studies indicate that amino acid residues predisposing VH1-46 Abs to Dsg3 reactivity reside in CDR2. However, somatic mutations only rarely promote Dsg3-VP6 cross-reactivity; most mutations abolish VP6 and/or Dsg3 reactivity. Nevertheless, functional testing identified two cross-reactive VH1-46 Abs that both disrupt keratinocyte adhesion and inhibit rotavirus replication, indicating the potential for VH1-46 Abs to have both pathologic autoimmune and protective immune functions. Taken together, these studies suggest that certain VH1-46 B cell populations may be predisposed to Dsg3-VP6 cross-reactivity, but multiple mechanisms prevent the onset of autoimmunity after rotavirus exposure.

Guillain-Barré syndrome: causes, immunopathogenic mechanisms and treatment

INTRODUCTION

Guillain-Barré syndrome is a rare disease representing the most frequent cause of acute flaccid symmetrical weakness of the limbs and areflexia usually reaching its peak within a month. The etiology and pathogenesis remain largely enigmatic and the syndrome results in death or severe disability in 9-17% of cases despite immunotherapy. Areas covered: In terms of etiology, Guillain-Barré syndrome is linked to Campylobacter infection but less than 0.1% of infections result in the syndrome. In terms of pathogenesis, activated macrophages and T cells and serum antibodies against gangliosides are observed but their significance is unclear. Expert commentary: Guillain-Barré syndrome is a heterogeneous condition with numerous subtypes and recent data point towards the role of ganglioside epitopes by immunohistochemical methods. Ultimately, the syndrome results from a permissive genetic background on which environmental factors, including infections, vaccination and the influence of aging, lead to disease.

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 GABA_B-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 GABA_B-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.

Utilizing complement evasion strategies to design complement-based antibacterial immunotherapeutics: Lessons from the pathogenic Neisseriae

Novel therapies are urgently needed to combat the global threat of multidrug-resistant pathogens. Complement forms an important arm of innate defenses against infections. In physiological conditions, complement activation is tightly controlled by soluble and membrane-associated complement inhibitors, but must be selectively activated on invading pathogens to facilitate microbial clearance. Many pathogens, including Neisseria gonorrhoeae and N. meningitidis, express glycans, including N-acetylneuraminic acid (Neu5Ac), that mimic host structures to evade host immunity. Neu5Ac is a negatively charged 9-cabon sugar that inhibits complement, in part by enhancing binding of the complement inhibitor factor H (FH) through C-terminal domains (19 and 20) on FH. Other microbes also bind FH, in most instances through FH domains 6 and 7 or 18-20. Here we describe two strategies to target complement activation on Neisseriae. First, microbial binding domains of FH were fused to IgG Fc to create FH18-20/Fc (binds gonococci) and FH6,7/Fc (binds meningococci). A point mutation in FH domain 19 eliminated hemolysis caused by unmodified FH18-20, but retained binding to gonococci. FH18-20/Fc and FH6,7/Fc mediated complement-dependent killing in vitro and showed efficacy in animal models of gonorrhea and meningococcal bacteremia, respectively. The second strategy utilized CMP-nonulosonate (CMP-NulO) analogs of sialic acid that were incorporated into LOS and prevented complement inhibition by physiologic CMP-Neu5Ac and resulted in attenuated gonococcal infection in mice. While studies to establish the safety of these agents are needed, enhancing complement activation on microbes may represent a promising strategy to treat antimicrobial resistant organisms.

Sialylated intravenous immunoglobulin suppress anti-ganglioside antibody mediated nerve injury

The precise mechanisms underlying the efficacy of intravenous immunoglobulin (IVIg) in autoimmune neurological disorders including Guillain-Barré syndrome (GBS) are not known. Anti-ganglioside antibodies have been reported to be pathogenic in some variants of GBS, and we have developed passive transfer animal models to study anti-ganglioside antibody mediated-endoneurial inflammation and associated neuropathological effects and to evaluate the efficacy of new therapeutic approaches. Some studies indicate that IVIg's anti-inflammatory activity resides in a minor sialylated IVIg (sIVIg) fractions and is dependent on an innate Th2 response via binding to a specific ICAM3-grabbing nonintegrin related 1 receptor (SIGN-R1). Therefore the efficacy of IVIg, IVIg fractions with various IgG Fc sialylation status, and the involvement of Th2 pathway were examined in one of our animal model of antibody-mediated inhibition of axonal regeneration. We demonstrate that both IVIg and sIVIg ameliorated anti-glycan antibody mediated-pathological effect, whereas, the unsialylated fractions of IVIg were not beneficial in our model. Tenfold lower doses of sIVIg compared to whole IVIg provided equivalent efficacy in our studies. Moreover, we found that whole IVIg and sIVIg significantly upregulates the gene expression of IL-33, which itself can provide protection from antibody-mediated nerve injury in our model. Our results support that the SIGN-R1-Th2 pathway is involved in the anti-inflammatory effects of IVIg on endoneurium in our model and elements of this pathway including IL-33 can provide novel therapeutics in inflammatory neuropathies.

Neurologic autoimmunity: mechanisms revealed by animal models

Over the last decade, neurologic autoimmunity has become a major consideration in the diagnosis and management of patients with many neurologic presentations. The nature of the associated antibodies and their targets has led to appreciation of the importance of the accessibility of the target antigen to antibodies, and a partial understanding of the different mechanisms that can follow antibody binding. This chapter will first describe the basic principles of autoimmune inflammation and tissue damage in the central and peripheral nervous system, and will then demonstrate what has been learnt about neurologic autoimmunity from circumstantial clinical evidence and from passive, active, and occasionally spontaneous or genetic animal models. It will cover neurologic autoimmune diseases ranging from disorders of neuromuscular transmission, peripheral and ganglionic neuropathy, to diseases of the central nervous system, where autoantibodies are either pathogenic and cause destruction or changes in function of their targets, where they are harmless bystanders of T-cell-mediated tissue damage, or are not involved at all. Finally, this chapter will summarize the relevance of current animal models for studying the different neurologic autoimmune diseases, and it will identify aspects where future animal models need to be improved to better reflect the disease reality experienced by affected patients, e.g., the chronicity or the relapsing/remitting nature of their disease.

Hepatitis E virus and neurological injury

Hepatitis E is hyperendemic in many developing countries in Asia and Africa, and is caused by hepatitis E virus (HEV) genotypes 1 and 2, which are spread via the faecal-oral route by contaminated water. Recent data show that HEV infection is also endemic in developed countries. In such geographical settings, hepatitis E is caused by HEV genotypes 3 and 4, and is mainly a porcine zoonosis. In a minority of cases, HEV causes acute and chronic hepatitis, but infection is commonly asymptomatic or unrecognized. HEV infection is associated with a number of extrahepatic manifestations, including a range of neurological injuries. To date, 91 cases of HEV-associated neurological injury--most commonly, Guillain-Barré syndrome, neuralgic amyotrophy, and encephalitis/myelitis--have been reported. Here, we review the reported cases, discuss possible pathogenic mechanisms, and present our perspectives on future directions and research questions.

Assessing Bacterial Interactions Using Carbohydrate-Based Microarrays

Carbohydrates play a crucial role in host-microorganism interactions and many host glycoconjugates are receptors or co-receptors for microbial binding. Host glycosylation varies with species and location in the body, and this contributes to species specificity and tropism of commensal and pathogenic bacteria. Additionally, bacterial glycosylation is often the first bacterial molecular species encountered and responded to by the host system. Accordingly, characterising and identifying the exact structures involved in these critical interactions is an important priority in deciphering microbial pathogenesis. Carbohydrate-based microarray platforms have been an underused tool for screening bacterial interactions with specific carbohydrate structures, but they are growing in popularity in recent years. In this review, we discuss carbohydrate-based microarrays that have been profiled with whole bacteria, recombinantly expressed adhesins or serum antibodies. Three main types of carbohydrate-based microarray platform are considered; (i) conventional carbohydrate or glycan microarrays; (ii) whole mucin microarrays; and (iii) microarrays constructed from bacterial polysaccharides or their components. Determining the nature of the interactions between bacteria and host can help clarify the molecular mechanisms of carbohydrate-mediated interactions in microbial pathogenesis, infectious disease and host immune response and may lead to new strategies to boost therapeutic treatments.

The immunobiology of Campylobacter jejuni: Innate immunity and autoimmune diseases

The Gram-negative bacterium Campylobacter jejuni causes gastroenteritis and Guillain-Barré syndrome in humans. Recent advances in the immunobiology of C. jejuni have been made. This review summarizes C. jejuni-binding innate receptors and highlights the role of innate immunity in autoimmune diseases. This human pathogen produces a variety of glycoconjugates, including human ganglioside-like determinants and multiple activators of Toll-like receptors (TLRs). Furthermore, C. jejuni targets MyD88, NLRP3 inflammasome, TIR-domain-containing adapter-inducing interferon-β (TRIF), sialic acid-binding immunoglobulin-like lectins (Siglecs), macrophage galactose-type lectin (MGL), and immunoglobulin-like receptors (TREM2, LMIR5/CD300b). The roles of these innate receptors and signaling molecules have been extensively studied. MyD88-mediated TLR activation or inflammasome-dependent IL-1β secretion is essential for autoimmune induction. TRIF mediates the production of type I interferons that promote humoral immune responses and immunoglobulin class-switching. Siglec-1 and Siglec-7 interact directly with gangliosides. Siglec-1 activation enhances phagocytosis and inflammatory responses. MGL internalizes GalNAc-containing glycoconjugates. TREM2 is well-known for its role in phagocytosis. LMIR5 recognizes C. jejuni components and endogenous sulfoglycolipids. Several lines of evidence from animal models of autoimmune diseases suggest that simultaneous activation of innate immunity in the presence of autoreactive lymphocytes or antigen mimicry may link C. jejuni to immunopathology.

The role of the gut microbiota in the pathogenesis of antiphospholipid syndrome

Infectious triggers are associated with the induction of transient antiphospholipid antibodies. One therefore wonders if microbes that permanently colonize us play a role in the pathogenesis of antiphospholipid syndrome (APS). The microbiota represents the collection of all microorganisms colonizing humans and is necessary for normal host physiology. The microbiota, however, is a constant stress on the immune system, which is tasked with recognizing and eliminating pathogenic microbes while tolerating commensal populations. A growing body of literature supports a critical role for the commensal-immune axis in the development of autoimmunity against colonized barriers (e.g., gut or skin) and sterile organs (e.g., pancreas or joints). Whether these interactions affect the development and sustainment of autoreactive CD4(+) T cells and pathogenic autoantibodies in APS is unknown. This review provides an overview of the current understanding of the commensal-immune axis in autoimmunity with a focus on the potential relevance to APS. Additionally, we discuss emerging findings supporting the involvement of the gut microbiota in a spontaneous model of APS, the (NZW × BXSB)F1 hybrid, and formalize hypotheses to explain how interactions between the immune system and the microbiota may influence human APS etiopathogenesis.

Streptococcal IdeS: therapeutic potential for Guillain-Barré syndrome

Plasma exchange and intravenous immunoglobulin are effective in treating Guillain–Barré syndrome (GBS) probably because the former removes IgG autoantibodies and complement and the latter inhibits complement activation subsequent to the autoantibody binding to peripheral nerve antigens. IgG degrading enzyme of Streptococcus pyogenes (IdeS) can cleave the pathogenic autoantibodies into F(ab’)₂ and Fc. The purpose of this study is to show whether IdeS has novel therapeutic potential for GBS. Sera with anti-ganglioside IgG antibodies from 15 patients with GBS or Miller Fisher syndrome were used. We tested whether IdeS cleaved the anti-ganglioside IgG antibodies and inhibited deposition of activated complement component on ELISA plates. IdeS efficiently cleaved IgG and blocked complement activation mediated by anti-GM1, anti-GD1a and anti-GQ1b IgG antibodies. IdeS has therapeutic potential for GBS and related conditions.

Anti-Ganglioside Antibodies Induce Nodal and Axonal Injury via Fcγ Receptor-Mediated Inflammation

Guillain-Barré syndrome (GBS) is a postinfectious autoimmune neuropathy and anti-ganglioside antibodies (Abs) are strongly associated with this disorder. Several studies have implied that specific anti-ganglioside Abs induce neuropathy in patients with axonal forms of GBS. To study the mechanisms of anti-ganglioside Abs-induced neuropathy, we established a new passive transfer mouse model by L5 spinal nerve transection (L5SNT; modified Chung's model) and systemic administration of anti-ganglioside Abs. L5SNT causes degeneration of a small proportion of fibers that constitute sciatic nerve and its branches, but importantly breaks the blood-nerve barrier, which allows access to circulating Abs and inflammatory cells. Our studies indicate that, in this mouse model, anti-ganglioside Abs induce sequential nodal and axonal injury of intact myelinated nerve fibers, recapitulating pathologic features of human disease. Notably, our results showed that immune complex formation and the activating Fc gamma receptors (FcγRs) were involved in the anti-ganglioside Abs-mediated nodal and axonal injury in this model. These studies provide new evidence that the activating FcγRs-mediated inflammation plays a critical role in anti-ganglioside Abs-induced neuropathy (injury to intact nerve fibers) in GBS.

Campylobacter jejuni capsular genotypes are related to Guillain-Barré syndrome

In about one in a thousand cases, a Campylobacter jejuni infection results in the severe polyneuropathy Guillain-Barré syndrome (GBS). It is established that sialylated lipo-oligosaccharides (LOS) of C. jejuni are a crucial virulence factor in GBS development. Frequent detection of C. jejuni with sialylated LOS in stools derived from patients with uncomplicated enteritis implies that additional bacterial factors should be involved. To assess whether the polysaccharide capsule is a marker for GBS, the capsular genotypes of two geographically distinct GBS-associated C. jejuni strain collections and an uncomplicated enteritis control collection were determined. Capsular genotyping of C. jejuni strains from the Netherlands revealed that three capsular genotypes, HS1/44c, HS2 and HS4c, were dominant in GBS-associated strains and capsular types HS1/44c and HS4c were significantly associated with GBS (p 0.05 and p 0.01, respectively) when compared with uncomplicated enteritis. In a GBS-associated strain collection from Bangladesh, capsular types HS23/36c, HS19 and HS41 were most prevalent and the capsular types HS19 and HS41 were associated with GBS (p 0.008 and p 0.02, respectively). Next, specific combinations of the LOS class and capsular genotypes were identified that were related to the occurrence of GBS. Multilocus sequence typing revealed restricted genetic diversity for strain populations with the capsular types HS2, HS19 and HS41. We conclude that capsular types HS1/44c, HS2, HS4c, HS19, HS23/36c and HS41 are markers for GBS. Besides a crucial role for sialylated LOS of C. jejuni in GBS pathogenesis, the identified capsules may contribute to GBS susceptibility.

Diagnostic Utility of Auto Antibodies in Inflammatory Nerve Disorders

A wide range of autoantibodies have been described in immune-mediated nerve disorders that target glycans borne by glycolipids and glycoproteins enriched in the peripheral nerves. Their use as diagnostic biomarkers is very widespread, despite some limitations on sensitivity and specificity, and the lack of standardized assays and access to quality assurance schemes. Although many methods have been applied to measurement, ELISA, in the form of commercial kits or in-house assays, still remains the most widely available and convenient assay methodology.Some antibodies have a particularly robust and widely appreciated clinical significance. Thus, the anti-MAG IgM antibodies that are found in IgM paraprotein related neuropathies define a relatively uniform clinical and prognostic phenotype. IgG antibodies against gangliosides GM1 and GD1a are strongly associated with motor axonal variants of Guillain-Barré syndrome, and anti-GQ1b with Miller Fisher syndrome. In other chronic neuropathies, antibodies against disialylated gangliosides including GD1b and GD3 are detected in ataxic neuropathies, usually associated with an IgM paraprotein, and antibodies against GM1 and the complex GM1:GalC are frequently found in multifocal motor neuropathy. Unfortunately, autoantibodies strongly associated with the diagnosis of chronic inflammatory demyelinating polyneuropathies and with demyelinating forms of GBS are still lacking.Identification of autoantibodies that map onto a specific clinical phenotype not only allows for improved classification, but also provides better understanding of the pathophysiology of inflammatory neuropathies and the potential for therapeutic interventions.

Mechanisms of distal axonal degeneration in peripheral neuropathies

Peripheral neuropathy is a common complication of a variety of diseases and treatments, including diabetes, cancer chemotherapy, and infectious causes (HIV, hepatitis C, and Campylobacter jejuni). Despite the fundamental difference between these insults, peripheral neuropathy develops as a combination of just six primary mechanisms: altered metabolism, covalent modification, altered organelle function and reactive oxygen species formation, altered intracellular and inflammatory signaling, slowed axonal transport, and altered ion channel dynamics and expression. All of these pathways converge to lead to axon dysfunction and symptoms of neuropathy. The detailed mechanisms of axon degeneration itself have begun to be elucidated with studies of animal models with altered degeneration kinetics, including the slowed Wallerian degeneration (Wld(S)) and Sarm knockout animal models. These studies have shown axonal degeneration to occur through a programmed pathway of injury signaling and cytoskeletal degradation. Insights into the common disease insults that converge on the axonal degeneration pathway promise to facilitate the development of therapeutics that may be effective against other mechanisms of neurodegeneration.

Complex of GM1- and GD1a-like lipo-oligosaccharide mimics GM1b, inducing anti-GM1b antibodies

Objective

Molecular mimicry between Campylobacter jejuni lipo-oligosaccharides (LOSs) and human gangliosides GM1 and GD1a induces the production of anti-GM1 and anti-GD1a antibodies, and the development of Guillain-Barré syndrome. Complexes of two different gangliosides form new molecular shapes capable of enhancing recognition by anti-ganglioside antibodies. To test the hypothesis that the complex of GM1-like and GD1a-like LOSs of C. jejuni induces the development of anti-GM1b antibodies in Guillain-Barré syndrome patients.

Methods

Mass spectrometry analysis determined the LOS outer core structures, with which mice were immunized. IgG antibodies to single gangliosides and complex of gangliosides were tested in sera from Guillain-Barré syndrome patients from whom C. jejuni LOS had been isolated.

Results

Two isolates from GBS patients who had anti-GM1b antibodies, but neither anti-GM1 nor -GD1a antibodies, expressed both GM1-like and GD1a-like LOSs, but not GM1b-like LOS. Anti-GM1b antibodies were induced in one of the mice immunized with the C. jejuni bearing GM1-like and GD1a-like LOS. Sera from 20 patients had antibodies to the complex of GM1 and GD1a, all of which carried anti-GM1b reactivity. Five of these sera harbored neither anti-GM1 nor anti-GD1a antibodies. IgG antibodies to the complex were absorbed by GM1b, but by neither GM1 nor GD1a.

Conclusions

GM1-like and GD1a-like LOSs form a GM1b epitope, inducing the development of anti-GM1b antibodies in patients with Guillain-Barré syndrome subsequent to C. jejuni enteritis. Here, we present a new paradigm that the complex of two different structures forms a new molecular mimicry, inducing the production of autoantibodies.

Molecular Mimicry and Autoimmunity

The term Molecular mimicry describes the sequence similarity between foreign (microorganism's peptides) and self peptides (the host's antigen). This phenomenon has been recently discovered as a one of the major mechanism in which there is a break-down of self-tolerance of the immune system following autoimmunity. After a short preface, the chapter contains examples of common infectious agents and their role in autoimmune diseases. Later on, it describes the autoimmune diseases in which there was found a relation to infectious agents via molecular mimicry mechanism. The data is summarized in two tables.