Study of Pathogenic Mechanisms and Identification of Novel Autoantibodies in Autoimmune Encephalitis (AE_Abs)

Study of Pathogenic Mechanisms and Identification of Novel Autoantibodies in Autoimmune Encephalitis Through the Integration of Conventional Methodologies and Advanced Single-cell Technologies

Autoimmune encephalitis is a debilitating neurological disorder that usually appears as a rapidly progressive form of brain dysfunction, typically developing in less than six weeks, caused by inflammation in the brain. These conditions show a wide range of clinical and immunological presentations and are generally divided into two main types.

The first type includes what are called paraneoplastic syndromes. In these cases, the immune system produces antibodies in response to a tumor that mistakenly target parts of the nervous system. The antibodies are not directly harmful themselves, but they are a sign that the immune system has launched a T-cell-driven attack on brain tissue because it recognizes a protein that's found both in the tumor and in the nervous system. These forms usually follow a single, non-repeating course and tend to respond poorly to treatment, which mostly focuses on removing or treating the underlying tumor and using immunotherapy to reduce the immune response.

The second type includes what we more properly call autoimmune encephalitis, where the immune system produces antibodies that directly attack proteins on the surface of neurons or on synaptic receptors in the brain. Unlike in paraneoplastic syndromes, these antibodies are directly responsible for the disease, and they don't usually indicate the presence of a tumor. Most people with this type of autoimmune encephalitis-around 70% to 80%-respond well to treatment with immunotherapy and can make a good or even full recovery. However, in about 20% of cases, the disease can come back or lead to long hospital stays, with a slower or only partial recovery.

There is also a third group of autoimmune encephalitides where the antibodies target synaptic proteins. These may or may not be linked to cancer, and the proteins they target are usually found inside the cells rather than on their surface.

A fourth group includes what are called seronegative autoimmune encephalitides. These are cases that meet the clinical criteria for autoimmune encephalitis, but no specific antibodies have been identified so far. Among the autoimmune neurological disorders without known antibodies is Susac syndrome, a rare condition that affects the brain, the retina, and the inner ear. It's especially interesting because its features suggest the involvement of antibodies, even though no disease-causing antibodies have yet been found.

The diagnosis of autoimmune encephalitis is based on clinical signs and symptoms, the detection of specific antibodies in blood or spinal fluid, and, in paraneoplastic cases, identifying the underlying tumor. To detect autoantibodies, doctors use various lab techniques, including immunoblotting and different types of immunofluorescence tests-some based on cultured cells, others on brain tissue from rodents.

Despite important progress in recent years, many cases of autoimmune encephalitis remain undiagnosed. One reason is that the disease can begin with vague or incomplete symptoms, making it difficult to recognize. Another issue is that current testing methods might not be sensitive enough to detect all possible antibodies. This means that the group of patients diagnosed with seronegative autoimmune encephalitis might actually include people who have antibodies we just haven't discovered yet.

In many cases, especially in the seronegative forms, the exact cause of the disease is still not fully understood.

The main goal of this study is to better understand how autoimmune encephalitis develops, especially in cases involving antibodies that target proteins on the surface of brain cells-such as NMDAR, GABABR, AMPAR, LGI1, and DNER-as well as in seronegative autoimmune encephalitis and in Susac syndrome. A second goal is to try to discover new autoantibodies that could explain the disease in patients who currently test negative.

Study Overview

• Status: Recruiting
• Conditions: Autoimmune Encephalitis

Detailed Description

Prospective and retrospective observational study

• Study Type: Observational
• Enrollment (Estimated): 20

Contacts and Locations

• Study Contact: Name: Raffaele Iorio; Phone Number: +390630155930; Email: raffaele.iorio@policlinicogemelli.it

Study Locations

• Italy
  • RM
    • Rome, RM, Italy, 00168
      • Recruiting
      • Fondazione Policlinico Universitario A. Gemelli IRCCS
      • Contact: Raffaele Iorio; Phone Number: 0630155930; Email: raffaele.iorio@policlinicogemelli.it

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

For the autoimmune encephalitis group: Patients diagnosed with encephalitis associated with antibodies against NMDAR, GABABR, AMPAR, LGI-1, DNER, seronegative autoimmune encephalitis, and Susac syndrome belonging to the IRCCS Fondazione Policlinico A. Gemelli on an outpatient basis, who meet the inclusion and exclusion criteria of the study, will be enrolled consecutively.

For the control group: patients with other neurological disorders, in whom the presence of antibodies against neuronal antigens has been excluded, belonging to the IRCCS Fondazione Policlinico A. Gemelli on an outpatient basis, who meet the inclusion and exclusion criteria of the study, will be enrolled consecutively.

Description

Inclusion Criteria:

• Patients > 18 years of age
• Patients able to provide informed consent
• For the patient group: patients diagnosed with autoimmune encephalitis associated with anti-NMDAR, GABABR, AMPAR, LGI-1, DNER antibodies, seronegative autoimmune encephalitis, or Susac syndrome, without other concomitant autoimmune diseases
• For the control group: patients without a diagnosis of autoimmune encephalitis associated with anti-NMDAR, GABABR, AMPAR, LGI-1, DNER antibodies, seronegative autoimmune encephalitis, or Susac syndrome
• For the control group: patients with other neurological disorders in whom the presence of antibodies against neuronal antigens has been excluded

Exclusion Criteria:

• Patients ≤ 18 years of age
• Deceased patients

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort
autoimmune encephalitis group; Patients diagnosed with encephalitis associated with antibodies against NMDAR, GABABR, AMPAR, LGI-1, DNER, seronegative autoimmune encephalitis, and Susac syndrome.
Control Group; A control group consisting of patients with other neurological disorders, in whom the presence of antibodies against neuronal antigens has been excluded, will also be enrolled.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Generate human recombinant monoclonal antibodies (mAbs) specific to the target antigen from patients' B cells	To generate monoclonal antibodies (mAbs) from autoreactive B cells of patients, we will use LIBRA-seq (Linking B-cell Receptor to Antigen specificity through sequencing), a recently developed technique.	12 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Isolate polyclonal IgG from the serum of patients with autoimmune encephalitis associated with known antibodies, seronegative autoimmune encephalitis, and Susac syndrome	IgGs will be purified (at a concentration of 2 mg/ml) from the serum of various patients using protein A/G Sepharose chromatography with the Melon™ Gel IgG Purification Kit. Protein concentration will be measured using the BCA Protein Assay Kit. All samples will be dialyzed against phosphate-buffered saline (PBS), and the solutions will be used at pH 7.4.	3 months

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Identify the autoantibody target antigen in samples from patients with seronegative autoimmune encephalitis and Susac syndrome using immunoprecipitation with electrophoresis and mass spectrometry	Identify the autoantibody target antigen in samples from patients with seronegative autoimmune encephalitis and Susac syndrome using immunoprecipitation combined with electrophoresis and mass spectrometry	12 months
Investigate and confirm the tissue reactivity of serum and cerebrospinal fluid samples, polyclonal IgGs, and mAbs on neuronal cultures and rat brain sections using immunohistochemistry techniques	Investigate and confirm the tissue reactivity of serum and CSF samples, polyclonal IgGs, and mAbs on neuronal cultures and rat brain sections using immunohistochemistry techniques.	6 months
Identify the autoantibody target antigen in samples from patients with seronegative autoimmune encephalitis and Susac syndrome using antigen protein microarrays	Identify the autoantibody target antigen in samples from patients with seronegative autoimmune encephalitis and Susac syndrome using antigen protein microarrays	12 months

Collaborators and Investigators

• Sponsor: Fondazione Policlinico Universitario Agostino Gemelli IRCCS
• Investigators: Principal Investigator: Raffaele Iorio, Fondazione Policlinico Universitario A. Gemelli, IRCCS

Study record dates

Study Major Dates

• Study Start (Actual): July 31, 2025
• Primary Completion (Estimated): July 31, 2028
• Study Completion (Estimated): December 31, 2028

Study Registration Dates

• First Submitted: April 14, 2025
• First Submitted That Met QC Criteria: March 12, 2026
• First Posted (Actual): March 17, 2026

Study Record Updates

• Last Update Posted (Actual): March 17, 2026
• Last Update Submitted That Met QC Criteria: March 12, 2026
• Last Verified: July 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Nervous System Diseases; Autoimmune Diseases; Immune System Diseases; Autoimmune Diseases of the Nervous System
• Other Study ID Numbers: 6379

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No