A Correlation Study Between PrP^C And Antibody Type And Titer,Changes In The Conditions,and IgG Of Patients With Autoimmune Encephalitis

Objective:By measuring the content of PrP^C in cerebrospinal fluid of patients with autoimmune encephalitis（AE）,we explored the relationship between PrP^C and the classification,severity,and changes of AE,so as to provide an index for early identification,early initiation of immunotherapy,and prognosis of AE.At the same time,by combining with the content of IgG in the cerebrospinal fluid of patients,we further studied the relationship between PrP^C and the pathogenesis of AE.Methods:Forty-five patients diagnosed with AE were included in this study among outpatients and inpatients of Jilin University First Hospital from February 2021 to January 2022.All patients completed lumbar puncture within 3 days of admission.We recorded the patients’ conditions,the severity of their conditions,the antibody types and titers in the cerebrospinal fluid,and IgG levels in the cerebrospinal fluid and retained 2 ml of cerebrospinal fluid from the patients.In the meanwhile,we collected 2 ml of cerebrospinal fluid of 45 patients as the control group who visited the clinic with headache without abnormalities in the cerebrospinal fluid pressure,routine,and cell count.The IgG content of cerebrospinal fluid was recorded.The content of PrP^C in the cerebrospinal fluid of the two groups was measured by ELISA.SPSS software was used for the statistical analysis of the data.Independent sample T test was used for the indicators conforming to normal distribution,while Mann-Whitney and Kruskal-Wallis nonparametric tests and Wilcoxon signed-rank test were used for the indicators with non-normal distribution.The correlation between indicators was analyzed by the Spearman rank correlation test.The χ2 test was used for comparison between groups of the counting data.P < 0.05 was considered to be statistically different.Results:1.There was a statistical difference in the PrP^C content of cerebrospinal fluid between the AE group and the control group（P<0.05）,however,there was no statistical difference of the indicator among the three subtypes of anti-NMDAR,LGI1,and GABABR antibodyassociated encephalitis（P>0.05）.2.There was a positive correlation between PrP^C content and antibody titer in the cerebrospinal fluid in AE patients with single antibody,and the correlation coefficient was0.409（P<0.05）.3.Among the four patients in this study who underwent lumbar puncture in the acute and recovery phases,their PrP^C levels in the cerebrospinal fluid were decreased,but the difference was not statistically significant（P>0.05）.4.There was a significant difference in the content of IgG in the cerebrospinal fluid between AE patients with antibody-associated with anti-cell surface antigen and the control group,and there was a positive correlation between the content of PrP^C in the cerebrospinal fluid and the content of IgG in cerebrospinal fluid.The correlation coefficient was 0.589（P<0.05）.Conclusion:1.The content of PrP^C in cerebrospinal fluid increased in patients with acute AE,suggesting that PrP^C might be a potential marker for the identification of AE,however,it has no guiding significance for the identification of AE subtypes.2.The positive correlation between cerebrospinal fluid PrP^C levels and antibody titers in AE patients suggested that PrP^C was useful in determining the severity of AE patients.3.The concentration of PrP^C in cerebrospinal fluid of convalescent AE patients was lower than that in the acute stage,but there was no guiding value for the prediction of disease changes,which could be further explored in large sample studies.4.AE patients with antibody-associated with anti-cell surface antigen had elevated cerebrospinal fluid IgG levels,and there was a positive correlation between the concentration of PrP^C and IgG levels in the cerebrospinal fluid,suggesting that PrP^C might be related to humoral immunity in AE,which could facilitate the exploration of PrP^C function.