Identification, validation, and characterization of novel autoantigens of chronic inflammatory demyelinating polyneuropathy (CIDP)
Clinical Neurology; Neurosurgery and Neuroradiology
Final Report Abstract
Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare disease of the peripheral nervous system. Patients suffer from progressively increasing limb weakness, ataxia, absent or diminished tendon reflexes, and paresthesia. Sensory neuropathies (SNs) are another disease of peripheral nerves, affecting the sensory system. Both diseases are considered having an autoimmune background, hence research has been focussing the identification of autoantibodies to improve diagnosis, treatment, and understanding of the disease. However, recent studies identified autoantigens for small subgroups only. Thus, my project aimed at identifying, validating, and characterizing novel autoantigens. The project has been divided into the following subprojects: During sample preparation, we developed a cheap and simple immunoblotting method to screen patient sera using their immunological fingerprints. We screened sera from 52 CIDP patients and 45 controls, identified a 155 kDa band in two anti-NF-155-positive patients (proof of principle), and found two novel immunobands specific for a CIDP subgroup. The sera from 22 classical CIDP patients were selected and their set of targeted autoantigens profiled via HuProt protein microarrays, containing about 16,000 different bait proteins. As controls, 12 SN patients and 9 healthy controls were profiled in parallel. A patient with Sjögren syndrome manifesting the known autoantibodies anti-Ro/SSA/Trove2 and anti-SS-B, as well as an autoimmune hepatitis patient manifesting anti- SLA/SEPSECS, served successfully as positive controls. We detected at least 10 novel disease-specific candidates in different patient subgroups (5-33%). The two best candidates – reacting with the biggest subgroup – was an antigen that was significantly detected by 5 out of 22 CIDP patients (CIDP antigen candidate 1, CAC1) and another antigen by 4 out of 12 SN patients (SN antigen candidate 1, SAC1). Although SN was not the focus of this project, we decided to address it because of the strong reactivity and the relatively high frequency. While establishing the ELISA for validation, we found a promising way to increase its sensitivity and specificity. Using this approach, we have tested an independent (and for SN patients also larger) cohort of patients and controls. We found 3/13 tested CIDP patients and 0/18 controls to be positive for anti-CAC1. Even more promising, 8/57 tested SN patients (14%) and 0/78 HCs (0%) were positive for anti-SAC1. CHARACTERIZATION: Denaturation assays suggest that anti-SAC1 antibodies bind its antigen in a conformation-specific way. As another way of characterizing the autoantibody, I successfully established an epitope mapping assay. The immense data set resulting from the protein microarray approach (106 data points) and the fact that the number of targeted antigens does not differ between patients and healthy controls, challenged me developing a novel idea of addressing the antigen repertoires in a more holistic way. I found that the size of the antigen repertoire depended on the clinical situation; e.g., CIDP patients responsive to intravenous immunoglobulin therapy targeted three times more antigens than non-responders. Furthermore, anchoring junction proteins and the downstream signaling pathway of the growth factor receptor are overrepresented in the CIDP repertoire as compared to that of controls. My project resulted and results in promising scientific and industrial cooperations. Furthermore, it helps to understand the role of autoantibodies in CIDP and SN patients by addressing novel single antigen candidates, but also the set of autoantigens holistically.
Publications
- (2017) Tubulin or not tubulin: Heading toward total protein staining as loading control in Western blots. Proteomics, vol. 17, 1600189
Moritz, C.P.
(See online at https://doi.org/10.1002/pmic.201600189) - (2019) Completing the immunological fingerprint by refractory proteins: Autoantibody screening by an improved immunoblotting technique. Proteomics Clinical Applications, 15:e1800157
Moritz, C.P., Tholance, Y., Reynaud-Federspiel, E., Rosier, C., Svahn, J., Camdessanché, J.P., Antoine, J.C.
(See online at https://doi.org/10.1002/prca.201800157) - (2019) Poor transcript-protein correlation in the brain: negatively correlating gene products reveal neuronal polarity as a potential cause. Journal of Neurochemistry
Moritz, C.P., Mühlhaus, T., Tenzer, S., Schulenborg, T., Friauf, E.
(See online at https://doi.org/10.1111/jnc.14664) - (2019) Reducing the risk of misdiagnosis of indirect ELISA by normalizing serumspecific background noise: The example of detecting anti-FGFR3 autoantibodies. Journal of Immunological Methods, vol. 466, 52-56
Moritz, C.P., Tholance, Y., Lassablière, F., Camdessanché, J.P., Antoine, J.C.
(See online at https://doi.org/10.1016/j.jim.2019.01.004)
