Treatment Of Surgical Brain Injury By Immune Tolerance Induced By Peripheral Intravenous Injection Of Antigens

Objective:Hepatic portal vein injection of brain antigens can lead to the body's immune tolerance to the brain antigens,which reduces brain tissue inflammation to achieve the treatment goal.However,complicated hepatic portal vein injections are not conducive to the clinical conversion of this technique.Peripheral intravenous infusion could be made possible by coating the brain antigens with liver biotargeting nanomaterials and controlling the particle size to within the range of liver phagocytosis.This method has been validated using the SBI model in rats.Methods:1.Preparation of nanoparticles loaded with brain antigen:Using the emulsion solvent evaporation method with polyvinyl alcohol-containing branched pullulan modified poly??-amino ester??PBAE?/poly?lactic-co-glycolic acid??PLGA?,novel nanoparticles with cores that included PVA/PBAE/PLGA were synthesized.First,PBAE/PLGA nanoparticles were prepared by the solvent emulsion evaporation method;then,polyvinyl alcohol?PVA?-containing branched pullulan was prepared,and the surface modification of the hydrophobic PBAE/PLGA nanoparticles was performed via the emulsion solvent evaporation method.The particle size distribution of the nanoparticles was measured with dynamic laser scattering,and the particle sizes and surface charge properties of the nanoparticles were measured with a Malvern Particle Sizer.PVA/PBAE/PLGA/myelin basic protein?MBP?and PVA/PBAE/PLGA/brain proteins were prepared,the amount of loaded protein and the entrapment efficiency were determined by ultraviolet spectrophotometry,the nanoparticles'abilities to carry both proteins were determined,and the morphologies of the nanoparticles were observed with transmission electron microscopy?TEM?.2.Evaluation of the therapeutic effect of biological targeting brain antigen nanomaterials following peripheral vein infusion in a rat SBI model:The SBI rat model was prepared in male Sprague-Dawley rats according to the methods of Ayer,RE^[3];the nanoparticles were then injected through the rat tail vein.The same doses of normal saline,allogeneic MBP,or allogeneic brain protein were injected into rats to create the following experimental groups:Group A:SBI+nanoparticles loaded with normal saline;Group B:SBI+nanoparticles loaded with MBP;and Group C:SBI+nanoparticles loaded with brain protein.One,7,14,and 21 days after brain injury,ELISAs were used to detect the peripheral blood levels of interleukin 2?IL-2?,transforming growth factor?TGF-?1?.FCM was used to test the blood CD4⁺T/CD8⁺T cell ratio.In the 21 days after surgery,immunohistochemistry was performed to obtain the apoptosis index of the microglial cell activation index of Anti-Ionized calcium binding adapter molecule 1?Iba-1?expression.Results:1.The nanoparticle loadings with MBP and brain protein were successfully achieved.The average diameter was 270±2.2 nm,the average polydispersity index was?PDI?<0.2,the average zeta potential values were 13.9 mV and 12.1 mV,and the greatest trapping efficiency was approximately 63%on average,which indicated good stability.TEM observation of the typical"core-shell"structure was performed.2.The two dosing groups exhibited significantly lower levels of the proinflammatory cytokine IL-2 than the control group postoperatively at 7 and 14 d after SBI,and the differences were statistically significant?P<0.05?.The two dosing groups exhibited higher TGF-?1 levels than the control group at 7,14 and 21 d after SBI,and the differences were statistically significant?P<0.05?.The ratios of CD4⁺T/CD8⁺T cells in the two dosing groups were lower than those in the control group postoperatively at 7 and 14 d after SBI,and the difference was statistically significant?P<0.05?.Immunohistochemistryperformedontheneuronalmicroglial cytoplasm-labeled Iba-1-positive cells were brown-yellow at 21 d after SBI.The results indicated that,compared with the control group,the expression of Iba-1 and the activation rate of microglia decreased in the two administration groups.Additionally,loaded with the same amount of protein,the nanoparticles loaded with brain protein were better than those loaded with MBP.Conclusion:1.Nanoparticles can effectively load MBP or brain protein.2.The injection of nanoparticles loaded with homologous MBP or brain protein into the rat tail vein can effectively induce immune tolerance and thus reduce postoperative secondary inflammatory damage,and the effect of nanoparticles loaded with brain protein was superior to that of nanoparticles loaded with MBP.