Cytokines/Chemokines: Potential Biomarkers for Non-paraneoplastic Anti-N-Methyl-D-Aspartate Receptor Encephalitis

Abstract

Objective: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is the most common type of autoimmune encephalitis. This study focuses on finding new biomarkers to evaluate the clinical condition and provide new directions for treatment. Methods: A total of 44 cytokines/chemokines in the cerebrospinal fluid of 10 non-paraneoplastic patients and nine controls were measured. We selected some of the cytokines/chemokines that significantly increased in patients. Six selected cytokines/chemokines, including IL-10, CXCL10, CCL22, CCL3, IL-7, TNF-α, and three previously reported (IL-2, IL-6, and IL-17A), were measured in seven other patients who provided repeat samples. We compared their levels and explored correlations with severity of disease and antibody titers. Results: The levels of Th1 axis (CXCL10, TNF-α, IFN-γ, CCL3), Th2 axis (CCL1, CCL8, CCL17, CCL22), Treg axis (IL-10), Th17 axis (IL-7), and B cell axis (CXCL13) cytokines, as well as IL-12 p40 and IL-16, were significantly higher in patients compared to those in controls. The level of IL-2 was significantly decreased at the intermediate stage of treatment compared with that before treatment. The severity of disease is positively correlated with levels of CXCL10, CCL3, IL-10, CCL22, and IL-6. The level of CCL3 in the high antibody titer group was greater than that in the low antibody titer group. Conclusion: The pathogenesis of anti-NMDAR encephalitis involves T cell and B cell cytokines. T cells likely assist B cells to produce antibodies. IL-2, CXCL10, CCL3, IL-10, CCL22, and IL-6 may represent new biomarkers in anti-NMDAR encephalitis. Given the lack of research on IL-10, CCL3, and CCL22 in this disease, it will be informative to explore their potential role in pathogenesis in larger studies.

Keywords: anti-NMDAR encephalitis; biomarker; chemokine; cytokine; prognosis.

Figure 1

Comparison of the level of cytokines/chemokines between anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis group and control group. Mann–Whitney U test was used. Only cytokines/chemokines that were statistically significantly different and selected for the next experiment are shown. Median cytokine/chemokine levels are indicated. **P < 0.01, ***P < 0.001. NMDA, anti-NMDAR encephalitis group; Control, control group.

Figure 2

Modified Rankin score (mRS) in patients in part two of the study. Green: only first-line treatment (IVIG/corticosteroids). The median mRS was 2.5 (0–5). Blue: first-line treatment plus mycophenolate mofetil. The median mRS was 2 (0–5). Red: first-line treatment plus rituximab. The median mRS was 3 (2–4). One recurrence occurred in patient 1 during follow-up; his mRS went up after falling. The other nine patients showed a downward trend in mRS over time, and their clinical symptoms gradually improved.

Figure 3

Levels of cytokines/chemokines in patients at different stages of disease. Kruskal–Wallis test with Mann–Whitney U test for post hoc analysis and Bonferroni correction were used. Only changes in IL-2 between group 1 and group 2 were statistically significant. Group 1: before treatment. Group 2: treatment had lasted for 2–3 months (the intermediate stage of treatment). Group 3: treatment had lasted for more than 3 months (the late stage of treatment).

Figure 4

Correlations between Modified Rankin score (mRS) and cytokines/chemokines. Spearman correlation analysis was used. mRS was positively correlated with CXCL10, CCL3, IL-10, CCL22, and IL-6 (p < 0.05).

Figure 5

Comparison of the level of cytokines/chemokines at different antibody titers. C1: antibody titer in cerebrospinal fluid (CSF) was negative ~1:100, n = 14. C2: Antibody titer in CSF was more than 1:100~1:320, n = 13. Mann–Whitney U test was used. The level of CCL3 was significantly increased in C2 compared to that in C1 (p < 0.05).

Figure 6

Patient 5 data. We collected four samples at 10, 94, 250, and 450 days after disease onset. Modified Rankin score at these four time points were 5, 2, 2, and 2, respectively. Antibody titer was 1:320, 1:320, 1:320, and 1:320. Clinical symptoms improved on day 94 compared with those on day 10. Despite equal antibody titers in the cerebrospinal fluid, the levels of IL-10, CCL22, IL-17A, IL-2, IL-6, CXCL10, CCL3, and TNF-α decreased.