Pathophysiology of autoimmune epilepsies from antibodies to hyperexcitable neuronal networks

Transcription

1 3 rd Congress of the European Academy of Neurology Amsterdam, The Netherlands, June 24 27, 2017 Teaching Course 2 Autoimmune causes of epilepsy - Level 3 Pathophysiology of autoimmune epilepsies from antibodies to hyperexcitable neuronal networks Angela C. Vincent Oxford, United Kingdom angela.vincent@imm.ox.ac.uk

2 Pathophysiology of Autoimmune Epilepsies From antibodies to hyperexcitable neuronal networks Angela Vincent Nuffield Department of Clinical Neurosciences Oxford With help from Profs Arjune Sen (Oxford), Mala Shah (London) and Holger Lerche (Tuebingen) Disclosures AV and University of Oxford receive payments and royalties for MuSK, LGI1 and CASPR2 antibody assays 1

3 Plan of presentation Myasthenia gravis as a model of antibody-mediated diseases Background to autoimmune epilepsy Epileptic encephalopathies What do we mean by autoimmune epilepsy? How common is it? How do antibodies alter cellular functions and generate seizures? Myasthenia gravis as a model of antibody-mediated diseases Antibodies that bind to extracellular domain of membrane protein on target tissue Antibodies measured in serum Antibodies cause loss of the target protein and/or damage to the membrane Patients can improve with immunotherapies: steroids, plasma exchange, intravenous immunoglobulins etc Injection of patient IgG affects target functions in vitro and transfers disease to mice 2

4 Mechanisms of antibodies illustrated by AChR-Abs in myasthenia gravis IgG1 and IgG3 antibodies are divalent and cause complement-mediated damage (a), increased internalisation (b) and occasionally direct inhibition of AChR function (c) Note that activation of the receptor by antibody is very uncommon From Crisp, Kullmann and Vincent Nature Reviews Neurology 2016 But MuSK antibodies are IgG4 > IgG1-3. IgG4 antibodies are hybrid and monovalent because they exchange arms with other IgG4 molecules. They do not activate complement or cause internalisation. They act mainly by inhibiting the binding of LRP4 to MuSK which is required for clustering AChRs at the neuromuscular junction 3

5 In addition, modifying mechanisms can operate in MG Ca 2+ Release of ACh increases to compensate Plomp et al 1995 Loss of postsynaptic membrane reduces sodium channels and leads to increase in threshold for CMAP Ruff and Lennon 1998 Rate of AChR synthesis increases to compensate Wilson et al 1983, Guyon et al 1994 Modifying mechanisms can occur at ALL synapses What factors might determine whether antibodies cause neuronal hyperexcitability in CNS neurons? Access of antibodies via blood flow/interstitial fluid require changes in BBB and/or intrathecal synthesis IgG subclass determines potential mechanisms Reduction in receptor or ion channel numbers or function usually result therefore target should be inhibitory not excitatory Morphological damage by complement can contribute But complement regulators may limit damage Compensatory pre- and post-synaptic changes likely Final result is unpredictable! 4

6 Background to autoimmune epilepsy Kasper et al Brain 2010 Corsellis JAN, Goldberg GJ, Norton AR 1968 Not all patients had a tumour 5

7 a. b. Jim McNamarra GluR3 antibodies in Rasmussen s encephalitis and response to plasma exchange. Rogers, Andrews.McNamarra Science 1994 NOT FOUND Watson.Lang Neurology 2004 BUT A B UPDATE 2017: AMPAR2/3 (GluR2/3) antibodies in 2/54 Rasmussen s encephalitis patients but GluR2/3 Abs may be secondary, not primary. 4 CBA Score Positive cutoff 0 RE HC DC Samples Hemispheric ratio Hemispheric ratio Anjan Nibber, Beth Lang, Christian Bien et al EJPN

8 Four patients Young onset, subacute, intractable TLE, verbal and visual memory defects, affective disorders. Increased T2 signal in limbic structues, inflammation on biopsy. No virus or tumour identified Non-paraneoplastic limbic encephalitis should be included in the differential diagnosis of adult patients with temporal lobe epilepsy. Neurology 2000 Acquired neuromyotonia an autoimmune voltage-gated potassium channel (VGKC) disease causing neuronal hyperexcitability Peripheral nerve hyperexcitability Twitching, cramps, weakness, sweating Improves after plasma exchange or IvIg VGKC-Abs detected in some patients Some had CNS involvement Hart et al al Ann Neurol 1997; Brain 2002; Turner et al JNNP

9 Limbic encephalitis: A treatable or spontaneously improving form of limbic encephalitis mostly >40 years, M>F Unexplained onset of severe memory loss, confusion, personality changes, seizures Inflammation in the hippocampus on magnetic resonance imaging or neuropathology Tumours <10% Hyponatraemia common VGKC-Ab positive 100+ per year in UK Buckley et al Neurology 2001; Vincent et al Brain 2004 But the antibodies are directed at VGKC-complexes Antibodies to any of these proteins can be positive in the 125 I- -dendrotoxin-vgkc-complex Ab assay LGI1 Contactin-2 CASPR2 Kv1 VGKC Kv1s Other? PSD95 PSD93 Irani et al Brain

10 VGKC-complex/LGI1 Abs most common LGI1 expressed on cultured hippocampal neurons Strongly associated with limbic encephalitis LGI1-Ab Neuron LGI1 Contactin-2 CASPR2 Kv1 VGKC Kv1s Other? PSD95 PSD93 LGI1 is mutated in autosomal dominant lateral temporal lobe epilepsy with auditory hallucinations Heterozygous transgenic mice cause seizure susceptibility. Fukata group, Japan Antibodies to cell-surface, extracellular antigens Live cell-based assays CASPR2 Antigen + EGFP Antigen + EGFP Patient has specific antibodies, Intensity can be scored visually Patient does not have specific antibodies Most labs use fixed tissue/fixed cells 9

11 Improvement in modified Rankin Scores following variable immunotherapies in 45 adult patients with VGKC-Ab limbic encephalitis Modified Rankin Scores in Lgi1-Ab positive patients Pre-treatment P< Post-treatment Death Normal 20 Oxford patients, years after successful treatment. Majority LGI1-Abs. Epilepsy remits readily in most. Neuropsychology testing shows normalisation in most modalities but verbal memory is still impaired Butler et al JNNP 2014 LGI1 antibodies associated with poor memory recovery and hippocampal atrophy Malter..Bien J Neurol 2014 Irani et al Brain 2010 VGKC/LGI1 Ab IgG elicits epileptiform activity in the CA3 area of hippocampus in brain slices Extracellular potentials recorded in the stratum lucidum of CA3 pyramidal cell layer with extracellular stimulation of mossy fibres LGI1-antibody positive IgG increased burst activity in CA3 Lalic et al Epilepsia

12 LGI1-antibody positive IgG increased the release probability of mossy fibre-ca3 pyramidal cell synapses Effects similar to blocking Kv1s with dendrotoxin Reduced no of failures in evoked excitatory postsynaptic currents (EPSCs) more hyperexcitability Lalic et al Epilepsia 2010 LGI1 forms bridge between pre and postsynaptic membranes LGI1-Abs mainly IgG4; direct block of LGI1 function LGI1-Ab Neuron Postsynaptic ADAM22 AMPAR LGI1 LGI LGI1 1 Others Presynaptic CASPR2 Kv1s ADAM23 LGI1-Abs disrupt binding of LGI1 to ADAM22 and reduce postsynaptic AMPARs Ohkawa et al J Neurosci

13 Majority of VGKC/LGI1 antibodies are IgG4 but nevertheless the pathology includes neuronal loss, T cell infiltrates and immunoglobulin and complement deposits. How is this? See Bien et al Brain 2012 er animal models? Knut shaking off after a swim in September 2010 Disputes between the two zoos continued into On 19 May, the Berlin Zoo offered to buy Knut VGKC/LGI1 antibodies in cats cause a similar syndrome with similar pathology Pakozdy et al 2014; Klang et al

14 Neuropsychiatric and movement disorders with NMDAR-Abs Presented with neuropsychiatric features, amnesia, seizures Became mute Developed facial grimacing and chewing, choreoathetoid limb movements Loss of consciousness No tumour found Very good recovery Dalmau et al 2007; 2008 Video courtesy of the patient and Dr G Vasello, Manchester Seizures are found in 70% of children and adults Titulaer et al Lancet Neurology

15 Seizures are common at first presentation, but do not dominate Irani et al Brain 2010 Vincent, Bien, Irani, Waters Lancet Neurology review 2011 NMDAR-Abs bind to hippocampal neurons and reduce the number of NMDARs on both excitatory and inhibitory neurons Hughes et al 2010; Moscato et al Ann Neurol 2014 In mice, intraventricular infusion of NMDAR-Ab CSFs caused cognitive defects and anhedonia Planaguma et al Brain 2014; 14

16 A Lateral ventricle Hippocamp us B Wright et al Brain 2015 F 50µm D1 Insert electrodes D D7 Inject IgG icv D9 Inject proconvulsant pentylenetetrazol (PTZ) E IgG bound ex vivo (CA3 highest) 100 µm 100 µm Seizure score related to IgG bound D 100µm NMDAR-Ab IgG HC IgG No overall loss of NMDARs How do the NMDAR-Abs cause increased seizure susceptibility in this model? 15

17 26/04/201 GABA A antibody GABA A R antibody Patients selected from archived samples Patients selected from archived samples Alpha and beta subunit antibodies Alpha and beta subunit antibodies Six patients higher titres, refractory seizures or SE Six patients higher titres, refractory seizures or SE Other patients low titre and some had other antibodies Other patients low titre and some had other antibodies eg GAD, GABAR eg GAD, GABAR GABA A antibody GABA A R antibody Routine referrals Routine referrals Alpha1 and gamma2 subunit Alpha1 and gamma2 subunit IgG antibodies and IgM IgG antibodies and IgM antibodies antibodies Clinical features at presentation Clinical features at presentation were diverse were diverse Seizures (47%), memory Seizures (47%), memory impairment (47%), impairment (47%), hallucinations (33%) or anxiety hallucinations (33%) or anxiety (20%) but few given (20%) but few given immunotherapy immunotherapy Pettingill et al Neurology 2015 Pettingill et al Neurology

18 Extracellular and intracellular antigens relevant to seizure disorders GABAaR GlyR (AChR) Patrick Waters from Vincent, Bien, Irani and Waters Lancet Neurology 2011 Can antibodies cause seizures without other evident neurological features? 17

19 Very frequent brief dystonic events with high VGKC-complex/LGI1Abs often PRECEDE limbic encephalitis Irani et al Neurology 2008; Irani et al Ann Neurol 2011; Irani et al Brain 2013 Thompson..Irani 2017 submitted 18

20 Autoimmune epilepsy in general 1. Epilepsy associated with autoimmune disorders Survey from USA health insurance: incidence of epilepsy (0.4% in population) and risk of epilepsy in patients with autoimmune disorders (mean 3.8), with highest risk in antiphospholipid syndrome and SLE. 1.3% of epilepsy cases associated with autoimmune disorder (ie approx 5/100,000 prevalence) Ong et al JAMA Neurol 2014 The Mayo Clinic definition of autoimmune epilepsy? M. Toledano et al. Neurology 2014;82:

21 How common are autoimmune epilepsies? 78 new patients in 21 months; 13 autoimmune (ie. approx 17%) M. Toledano et al. Neurology 2014;82: What other forms of autoimmune epilepsy are there? 2. Status epilepticus occurring with specific neuronal antibodies Survey from 7 centres, 8 years, only identified 13 patients with status epilepticus 12F, 1M Epilepsy first feature in most 5/13 had tumours 8/13 NMDAR-Abs, no Abs to LGI1 (or GABA A R not available at the time) Holtzer et al European Neurology

22 3. Typical epilepsy occurring with specific neuronal antibodies 111 patients with long-standing MTLE had antibodies 11 CASPR2 1 GABAAR 4 NMDAR 5 GlyR 4 VGKC-complex only Vanli-Yavuz et al JNNP 2016 BUT we need to know when antibody testing performed in relation to onset of seizures are antibodies primary or secondary to neuroinflammation? Antibodies to VGKC-complexes found in proportion of patients with unselected epilepsy, particularly focal epilepsies, in adults and children, but usually low levels and significance unclear Contactin-2 CASPR2 125 I-DTX LGI1 Kv1s Other Brenner et al Epilepsia 2013; Also Suleiman et al Dev Med Neurol 2011; Suleiman et al 2013; Quek et al 2012; Lang et al in preparation

23 Historic cases with serum at first study Historic cohort of paediatric cases, no immunotherapies. Antibodies were not associated with AED resistance, and some fell spontaneously, or appeared de novo over time. Ie may be secondary, not primary What controls the pyramidal neuron? Pyramidal neuron receives input from dendrites which are controlled by Cav (L,T), HCN and Kv4.2 Pyramidal dendrites and cell body are also modulated by inhibitory neurons via nachr and GABA A R Action initial segment initiates activity via Nav1.2; Kv1 and 7 control axonal activity From Lerche, Shah et al J Physiol

24 Targets for autoimmune epilepsy Antibodies cause loss of function Therefore candidate antigens are those for which loss of function gene mutations or perhaps modifiers? cause increased excitability Gene targets Loss of function mutation Gain of function mutation Modifiers of disease Increased excitability predicted IgG antibody targets K v 1.1,1.2 Yes Yes Yes No LGI1 Yes Yes Yes IgG4>>IgG1 CASPR2 Yes Yes Yes IgG4>IgG1 K Ca 1.1 Yes Yes Yes? K v 7.2,7.3 Yes Yes Yes? NR1 IgG1 NR2a,b? GABA A Ra1,g2 Yes Yes Yes IgG1 Nav1.1, 1.2 Yes Yes Yes Unlikely Ca v 2.1 Yes Yes Yes Unlikely HCN Reduced Yes? K v 4.2 Reduced Yes? Taken from Lerche, Shah J Physiol et al 2013 (a) Activation of pyramidal cells by glutamate release onto AMPAR and NMDARs. Output also stimulates GABAergic neurons via glutamate/nmdars GABA release onto pyramidal neuron provides a feedback loop and regulates activity But how do NMDAR-Abs cause seizures? (b) Antibody-mediated reduction of NMDARs on GABAergic neurons leads to unregulated pyramidal cell activity and seizures Wright and Vincent Current Op Neurol

25 Autoimmune epilepsy some questions How many immunotherapy-responsive epilepsy patients are there? Are they being missed or over-diagnosed? Is positive NMDAR-Ab CSF relevant to autoimmune epilepsy or only to encephalitis? Can brain damage induce autoantibodies to these antigens (eg. post-hsv encephalitis, NMDAR-Abs)? Should we be looking at candidate epilepsy antigens (eg. HCN)? 24

26 References Bien CG, Schulze-Bonhage A, Deckert M, Urbach H, Helmstaedter C, Grunwald T, Schaller C, Elger CE. Limbic encephalitis not associated with neoplasm as a cause of temporal lobe epilepsy. Neurology Dec 26;55(12): Bien CG, Vincent A, Barnett MH, Becker AJ, Blumcke I, Graus F, Jellinger KA, Reuss DE, Ribalta T, Schlegel J, Sutton I, Lassmann H, Bauer J. Immunopathology of autoantibody-associated encephalitides: clues for pathogenesis. Brain : a journal of neurology May;135(Pt 5): Butler CR, Miller TD, Kaur MS, Baker IW, Boothroyd GD, Illman NA, Rosenthal CR, Vincent A, Buckley CJ. Persistent anterograde amnesia following limbic encephalitis associated with antibodies to the voltage-gated potassium channel complex. Journal of neurology, neurosurgery, and psychiatry Apr;85(4): Fukata Y, Lovero KL, Iwanaga T, Watanabe A, Yokoi N, Tabuchi K, Shigemoto R, Nicoll RA, Fukata M. Disruption of LGI1-linked synaptic complex causes abnormal synaptic transmission and epilepsy. Proceedings of the National Academy of Sciences of the United States of America Feb 23;107(8): PubMed PMID: Pubmed Central PMCID: Gresa-Arribas N, Titulaer MJ, Torrents A, Aguilar E, McCracken L, Leypoldt F, Gleichman AJ, Balice-Gordon R, Rosenfeld MR, Lynch D, Graus F, Dalmau J. Antibody titres at diagnosis and during followup of anti-nmda receptor encephalitis: a retrospective study. The Lancet Neurology Feb;13(2): PubMed PMID: Pubmed Central PMCID: Hacohen Y, Wright S, Waters P et al. Paediatric autoimmune encephalopathies: clinical features, laboratory investigations and outcomes in patients with or without antibodies to known central nervous system autoantigens. Journal of neurology, neurosurgery, and psychiatry Jul;84(7): Irani SR, Alexander S, Waters P, Kleopa KA, Pettingill P, Zuliani L, Peles E, Buckley C, Lang B, Vincent A. Antibodies to Kv1 potassium channel-complex proteins leucine-rich, glioma inactivated 1 protein and contactin-associated protein-2 in limbic encephalitis, Morvan's syndrome and acquired neuromyotonia. Brain : a journal of neurology Sep;133(9): PubMed PMID:

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29 Titulaer MJ, McCracken L, Gabilondo I, Armangue T, Glaser C, Iizuka T, Honig LS, Benseler SM, Kawachi I, Martinez-Hernandez E, Aguilar E, Gresa-Arribas N, Ryan-Florance N, Torrents A, Saiz A, Rosenfeld MR, Balice-Gordon R, Graus F, Dalmau J. Treatment and prognostic factors for long-term outcome in patients with anti- NMDA receptor encephalitis: an observational cohort study. The Lancet Neurology Feb;12(2): Toledano M, Britton JW, McKeon A, Shin C, Lennon VA, Quek AM, So E, Worrell GA, Cascino GD, Klein CJ, Lagerlund TD, Wirrell EC, Nickels KC, Pittock SJ. Utility of an immunotherapy trial in evaluating patients with presumed autoimmune epilepsy. Neurology May 06;82(18): Varadkar S, Bien CG, Kruse CA, Jensen FE, Bauer J, Pardo CA, Vincent A, Mathern GW, Cross JH. Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances. The Lancet Neurology Feb;13(2): Vincent A, Bien CG, Irani SR, Waters P. Autoantibodies associated with diseases of the CNS: new developments and future challenges. The Lancet Neurology Aug;10(8): Vincent A, Buckley C, Schott JM, Baker I, Dewar BK, Detert N, Clover L, Parkinson A, Bien CG, Omer S, Lang B, Rossor MN, Palace J. Potassium channel antibody-associated encephalopathy: a potentially immunotherapy-responsive form of limbic encephalitis. Brain : a journal of neurology Mar;127(Pt 3): Wright S, Geerts AT, Jol-van der Zijde CM, Jacobson L, Lang B, Waters P, van Tol MJ, Stroink H, Neuteboom RF, Brouwer OF, Vincent A. Neuronal antibodies in pediatric epilepsy: Clinical features and long-term outcomes of a historical cohort not treated with immunotherapy. Epilepsia May;57(5): Wright S, Hashemi K, Stasiak L, Bartram J, Lang B, Vincent A, Upton AL. Epileptogenic effects of NMDAR antibodies in a passive transfer mouse model. Brain : a journal of neurology Nov;138(Pt 11): Wright S, Vincent A. Progress in autoimmune epileptic encephalitis. Current opinion in neurology Apr;29(2): Wright S, Vincent A. Pediatric Autoimmune Epileptic Encephalopathies. Journal of child neurology Mar;32(4): PubMed PMID: