Advances in Potential Cerebrospinal Fluid Biomarkers for Autoimmune Encephalitis: A Review

Long-Term Clinical and Biological Prognostic Factors of Anti-NMDA Receptor Encephalitis in Children

BACKGROUND AND OBJECTIVES

Anti-NMDAR encephalitis (NMDARE) is a severe neurologic condition, and recently, the NMDAR Encephalitis One-Year Functional Status (NEOS) score has emerged as a 1-year prognostic tool. This study aimed to evaluate NEOS score and biomarker (neurofilament light chains [NfL], total-Tau protein, glial fibrillary acidic protein, and serum cytokines) correlation with modified Rankin Scale (mRS), cognitive impairment, and clinical recovery in pediatric NMDARE over 2 years.

METHODS

In this French multicenter observational study, 104 pediatric patients with NMDARE were followed for a minimum of 2 years. Clinical data and serum/plasma samples were collected. Biomarker levels, measured using electroluminescence mesoscale discovery (MSD) S-PLEX, were compared between patients and controls and assessed for correlations with disease activity, mRS, cognitive/language impairment, and recovery status at 2 years.

RESULTS

At a median follow-up of 39.5 months, 68 percent of patients had unfavorable recovery and 54% had significant cognitive impairment. Both outcomes were strongly associated with younger age at diagnosis (OR 6.10 [1.91-27.3] p < 0.01 and 5.69 [1.46-27.7] p = 0.02, respectively). A higher NEOS score was significantly correlated with increased cognitive impairment (OR 2.53 [1.52-4.21], p < 0.001), higher mRS scores (OR 2.12 [1.34-3.57], p < 0.01), and unfavorable recovery at 2 years (OR 2.00 [1.30-3.06], p = 0.015). Elevated NfL levels were significantly associated with unfavorable recovery (OR 3.62 [1.29-10.9] p = 0.012) and severe cognitive impairment (OR 3.77 [1.38-10.9] p = 0.012) at 2 years. The combined area under the curve (AUC) for NfL and NEOS was significantly higher than the AUCs of NEOS and NfL alone (p = 0.01).

DISCUSSION

The NEOS score strongly predicts long-term outcomes in NMDARE, with its predictive value extending beyond the first-year mR prediction. NfL levels at disease onset seem to improve accuracy in predicting poor outcomes, providing valuable information for treatment decisions and future clinical trials.

Soluble Membrane Attack Complex (sMAC) as a Potential Diagnostic Biomarker Differentiating Acute Viral Encephalitis from Guillain-Barré Syndrome, a Post-infectious Autoimmune State

Acute encephalitis syndrome (AES) presents with the onset of fever, altered sensorium and/or seizures, known to be caused by various infectious and non-infectious aetiological agents, among which viruses are the commonest. The severity of AES prompts rapid diagnosis, which is not met by time-consuming conventional diagnostic techniques. In this study, archived cerebrospinal fluid samples of laboratory-confirmed viral AES, an acute infectious condition and Guillain-Barré Syndrome (GBS), a post-infectious, autoimmune condition was assessed for soluble membrane attack complex (sMAC) using ELISA. Statistical analysis was performed to understand the diagnostic potential of sMAC in AES versus GBS patients. sMAC levels were significantly increased in viral encephalitis compared with GBS samples (43.69 ng/mL vs. 29.33 ng/mL, P < 0.05). The diagnostic potential of sMAC was assessed using the receiver operating characteristic (ROC) curve, which demonstrated excellent diagnostic discrimination between viral AES and GBS (area under curve = 0.8125, 95% CI, P < 0.0001). Using Youden's index, the optimal sMAC cut-off was calculated as 33.6 ng/mL for distinguishing AES from GBS. The findings of our study revealed significant increase in sMAC levels in AES patients in comparison to those with GBS. This underscores the utility of sMAC as a valuable tool in distinguishing between AES and GBS, thereby facilitating more tailored patient management strategies, which varies for acute infectious and post-infectious conditions especially those mediated by autoimmunity.

A Minimally-Invasive Method for Serial Cerebrospinal Fluid Collection and Injection in Rodents with High Survival Rates

Cerebrospinal fluid (CSF) is an important sample source for diagnosing diseases in the central nervous system (CNS), but collecting and injecting CSF in small animals is technically challenging and often results in high mortality rates. Here, we present a cost-effective and efficient method for accessing the CSF in live rodents for fluid collection and infusion purposes. The key element of this protocol is a metal needle tool bent at a unique angle and length, allowing the successful access of the CSF through the foramen magnum. With this method, we can collect 5-10 µL of the CSF from mice and 70-100 µL from rats for downstream analyses, including mass spectrometry. Moreover, our minimally-invasive procedure enables iterative CSF collection from the same animal every few days, representing a significant improvement over prior protocols. Additionally, our method can be used to inject solutions into mice cisterna magna with high success rates and high postoperative recovery rates. In summary, we provide an efficient and minimally-invasive protocol for collecting and infusing reagents into the CSF in live rodents. We envision this protocol will facilitate biomarker discovery and drug development for diseases in the central nervous system.

Biomarkers in autoimmune diseases of the central nervous system

The autoimmune diseases of the central nervous system (CNS) represent individual heterogeneity with different disease entities. Although clinical and imaging features make it possible to characterize larger patient cohorts, they may not provide sufficient evidence to detect disease activity and response to disease modifying drugs. Biomarkers are becoming a powerful tool due to their objectivity and easy access. Biomarkers may indicate various aspects of biological processes in healthy and/or pathological states, or as a response to drug therapy. According to the clinical features described, biomarkers are usually classified into predictive, diagnostic, monitoring and safety biomarkers. Some nerve injury markers, humoral markers, cytokines and immune cells in serum or cerebrospinal fluid have potential roles in disease severity and prognosis in autoimmune diseases occurring in the CNS, which provides a promising approach for clinicians to early intervention and prevention of future disability. Therefore, this review mainly summarizes the potential biomarkers indicated in autoimmune disorders of the CNS.

CHI3L1 in the CSF is a potential biomarker for anti-leucine-rich glioma inactivated 1 encephalitis

Objective

Anti-leucine-rich glioma inactivated 1(LGI1) encephalitis is one rare autoimmune encephalitis which is accompanied by inflammatory responses. (Anti-leucine-rich glioma inactivated 1 (anti-LGI1) encephalitis is an autoimmune disease mediated by inflammatory responses.)This study aimed to investigate the Chitinase 3-like 1(CHI3L1) in anti-LGI1encephalitis patients and evaluate its association with modified Rankin Scale (mRS) score in anti-LGI1 encephalitis at admission and 6 months follow-up.(This study looked into the relationship between Chitinase 3-like 1 (CHI3L1) and the modified Ranking Scale (mRS) score in anti-LGI1 encephalitis patients at admission and 6 months later.).

Methods

Thirty-five patients with anti-LGI1 encephalitis and 22 patients with non-inflammatory neurological disease were enrolled in this study. (We enrolled 35 patients with anti-LGI1 encephalitis and 22 patients with non-inflammatory neurological disease.)Cerebrospinal fluid (CSF) and serum levels of CHI3L1 were measured by enzyme-linked immunosorbent assay. (We quantified CHI3L1 in the serum and cerebrospinal fluid (CSF) by performing an enzyme-linked immunosorbent assay.)Patients were evaluated for mRS score at admission and at 6 months follow-up.(We recorded the mRS score of the patients at admission and 6 months later.).

Results

CHI3L1 levels in CSF and serum were highly elevated in patients with anti-LGI1 encephalitis at admission compared those with the controls.(At admission, patients with anti-LGI1 encephalitis had elevated CHI3L1 levels in the CSF and serum.) Additionally, patients presenting with cognitive impairment had significantly higher CSF CHI3L1 levels and mRS scores than those without cognitive impairment symptoms. Patients presenting with only faciobrachial dystonic seizures at admission had lower CSF CHI3L1 levels than those with other symptoms. Finally, CSF CHI3L1 levels were positively correlated with CSF lactate levels.

Conclusion

CHI3L1 level in CSF is correlated with the severity and prognosis of anti-LGI1 encephalitis. (CSF CHI3L1 levels are correlated with the severity and prognosis of anti-LGI1 encephalitis.).