To explore the characteristics of anti N-methyl-D-aspartate receptor (NMDAR) encephalitis exosomes and the potential of exosomal microRNAs as a new biomarker for anti-NMDAR encephalitis.

Some studies have shown that anti-NMDAR-IgG can be detected in a few of healthy people. Therefore it is necessary to find a better new biomarker to provide new diagnosis and treatment ideas in clinical practice. It have confirmed that exosomal microRNAs plays a crucial pathogenic role in some autoimmune diseases. Furthermore, exosomes have both diagnostic and therapeutic effects for many neurological diseases. Previous studies have shown that exosomal microRNAs, as a new biomarker, can be used not only for the diagnosis of diseases, but also for prognosis evaluation in myasthenia gravis, Alzheimer's disease and multiple sclerosis.

We collected peripheral venous blood from patients with anti-NMDAR encephalitis (AE group), neuromyelitis optica spectrum disorders patients with positive aquaporin-4 (AQP-4) antibody (NMOSD group) and healthy people (HC group), and isolated exosomes in plasma to obtain the exosomal microRNAs. Analyzed the differential expression and function of genes by the next-generation sequencing technology. The microRNAs with significant differential expression and corresponding target genes enrichment of functional pathways were screened.

In the comparison between AE group and HC group, there were 5 microRNAs with significant differential expression and high diagnostic efficacy. There were 3 common differentially expressed microRNAs between AE and NMOSD group compared to HC group. The most obvious pathways for differential genes enrichment in the AE group were: TGF-beta signaling pathway, Axon guidance, Signaling pathways regulating pluripotency of stem cells, Small cell lung cancer and so on.

In this study, it was found that exosomal microRNAs have important research value and application prospects in the early diagnosis and tumor screening of anti-NMDAR encephalitis, and provide new diagnostic and therapeutic ideas for the clinical treatment of anti-NMDAR encephalitis.