Intracellular and non-neuronal targets of voltage-gated potassium channel complex antibodies
Objectives<br/> Autoantibodies against the extracellular domains of the voltage-gated potassium channel (VGKC) complex proteins, leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-2 (CASPR2), are found in patients with limbic encephalitis, faciobrachial dystonic seizure...
| Main Authors: | , , , , , , , , , , , , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
BMJ Publishing Group
2017
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| _version_ | 1826298778266632192 |
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| author | Lang, B Makuch, M Moloney, T Dettmann, I Mindorf, S Probst, C Stoecker, W Buckley, C Newton, C Leite, I Maddison, P Komorowski, L Adcock, J Vincent, A Waters, P Irani, S |
| author_facet | Lang, B Makuch, M Moloney, T Dettmann, I Mindorf, S Probst, C Stoecker, W Buckley, C Newton, C Leite, I Maddison, P Komorowski, L Adcock, J Vincent, A Waters, P Irani, S |
| author_sort | Lang, B |
| collection | OXFORD |
| description | Objectives<br/> Autoantibodies against the extracellular domains of the voltage-gated potassium channel (VGKC) complex proteins, leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-2 (CASPR2), are found in patients with limbic encephalitis, faciobrachial dystonic seizures, Morvan’s syndrome and neuromyotonia. However, in routine testing, VGKC-complex-antibodies without LGI1- or CASPR2-reactivities (“double-negative”) are commoner than LGI1- or CASPR2-specificities. Therefore, the target(s) and clinical associations of double-negative antibodies need to be determined. <br/><br/>Methods<br/> Sera (n=1131) from several clinically-defined cohorts were tested for IgG-radioimmunoprecipitation of 125I-DTX-labelled VGKC-complexes from mammalian brain extracts. Positive samples were systematically tested for live hippocampal neuron reactivity, IgG-precipitation of 125I-DTX and 125I-DTX-labelled Kv1-subunits, and by cell-based assays which expressed Kv1-subunits, LGI1 and CASPR2. <br/><br/>Results<br/> VGKC-complex-antibodies were found in 162 of 1131 (14%) sera. Ninety of these (56%) had antibodies targeting the extracellular domains of LGI1 or CASPR2. Of the remaining 72 double-negative sera, ten (14%) immunoprecipitated 125I-DTX itself, and 27 (38%) bound to solubilized co-expressed Kv1.1/1.2/1.6 subunits and/or Kv1.2 subunits alone, at levels proportionate to VGKC-complex-antibody levels (r=0.57, p=0.0017). The sera with LGI1- and CASPR2-antibodies immunoprecipitated neither preparation. None of the 27 Kv1-precipitating samples bound live hippocampal neurons or Kv1-extracellular domains, but 16 (59%) bound to permeabilised Kv1-expressing HEK cells. These intracellular Kv1-antibodies mainly associated with non-immune disease aetiologies, poor longitudinal clinical-serological correlations, and a limited immunotherapy-response. <br/><br/>Conclusions<br/> Double-negative VGKC-complex-antibodies are often directed against cytosolic epitopes of Kv1-subunits, and occasionally against non-mammalian DTX. These antibodies should no longer be classified as neuronal-surface antibodies. They consequently lack pathogenic potential, and do not in themselves support use of immunotherapies. |
| first_indexed | 2024-03-07T04:52:00Z |
| format | Journal article |
| id | oxford-uuid:d54a3596-b855-46fb-a0db-87a3caed4c31 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T04:52:00Z |
| publishDate | 2017 |
| publisher | BMJ Publishing Group |
| record_format | dspace |
| spelling | oxford-uuid:d54a3596-b855-46fb-a0db-87a3caed4c312022-03-27T08:24:57ZIntracellular and non-neuronal targets of voltage-gated potassium channel complex antibodiesJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:d54a3596-b855-46fb-a0db-87a3caed4c31EnglishSymplectic Elements at OxfordBMJ Publishing Group2017Lang, BMakuch, MMoloney, TDettmann, IMindorf, SProbst, CStoecker, WBuckley, CNewton, CLeite, IMaddison, PKomorowski, LAdcock, JVincent, AWaters, PIrani, S Objectives<br/> Autoantibodies against the extracellular domains of the voltage-gated potassium channel (VGKC) complex proteins, leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-2 (CASPR2), are found in patients with limbic encephalitis, faciobrachial dystonic seizures, Morvan’s syndrome and neuromyotonia. However, in routine testing, VGKC-complex-antibodies without LGI1- or CASPR2-reactivities (“double-negative”) are commoner than LGI1- or CASPR2-specificities. Therefore, the target(s) and clinical associations of double-negative antibodies need to be determined. <br/><br/>Methods<br/> Sera (n=1131) from several clinically-defined cohorts were tested for IgG-radioimmunoprecipitation of 125I-DTX-labelled VGKC-complexes from mammalian brain extracts. Positive samples were systematically tested for live hippocampal neuron reactivity, IgG-precipitation of 125I-DTX and 125I-DTX-labelled Kv1-subunits, and by cell-based assays which expressed Kv1-subunits, LGI1 and CASPR2. <br/><br/>Results<br/> VGKC-complex-antibodies were found in 162 of 1131 (14%) sera. Ninety of these (56%) had antibodies targeting the extracellular domains of LGI1 or CASPR2. Of the remaining 72 double-negative sera, ten (14%) immunoprecipitated 125I-DTX itself, and 27 (38%) bound to solubilized co-expressed Kv1.1/1.2/1.6 subunits and/or Kv1.2 subunits alone, at levels proportionate to VGKC-complex-antibody levels (r=0.57, p=0.0017). The sera with LGI1- and CASPR2-antibodies immunoprecipitated neither preparation. None of the 27 Kv1-precipitating samples bound live hippocampal neurons or Kv1-extracellular domains, but 16 (59%) bound to permeabilised Kv1-expressing HEK cells. These intracellular Kv1-antibodies mainly associated with non-immune disease aetiologies, poor longitudinal clinical-serological correlations, and a limited immunotherapy-response. <br/><br/>Conclusions<br/> Double-negative VGKC-complex-antibodies are often directed against cytosolic epitopes of Kv1-subunits, and occasionally against non-mammalian DTX. These antibodies should no longer be classified as neuronal-surface antibodies. They consequently lack pathogenic potential, and do not in themselves support use of immunotherapies. |
| spellingShingle | Lang, B Makuch, M Moloney, T Dettmann, I Mindorf, S Probst, C Stoecker, W Buckley, C Newton, C Leite, I Maddison, P Komorowski, L Adcock, J Vincent, A Waters, P Irani, S Intracellular and non-neuronal targets of voltage-gated potassium channel complex antibodies |
| title | Intracellular and non-neuronal targets of voltage-gated potassium channel complex antibodies |
| title_full | Intracellular and non-neuronal targets of voltage-gated potassium channel complex antibodies |
| title_fullStr | Intracellular and non-neuronal targets of voltage-gated potassium channel complex antibodies |
| title_full_unstemmed | Intracellular and non-neuronal targets of voltage-gated potassium channel complex antibodies |
| title_short | Intracellular and non-neuronal targets of voltage-gated potassium channel complex antibodies |
| title_sort | intracellular and non neuronal targets of voltage gated potassium channel complex antibodies |
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