Archives of Academic Emergency Medicine. 2021; 9(1): e57 REV I EW ART I C L E Active and Passive Immunization with Myelin Basic Pro- tein as a Method for Early Treatment of Traumatic Spinal Cord Injury; a Meta-Analysis Mahmoud Yousefifard1a, Arian Madani Neishaboori1a, Seyedeh Niloufar Rafiei Alavi1, Amirmohammad Toloui1, Mohammed I M Gubari2, Amirali Zareie Shab Khaneh3, Maryam Karimi Ghahfarokhi3, Mostafa Hosseini4,3∗ 1. Physiology Research Center, Iran University of Medical Sciences, Tehran, Iran. 2. Community Medicine, College of Medicine, University of Sulaimani, Sulaimani, Iraq. 3. Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. 4. Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran. Received: June 2021; Accepted: July 2021; Published online: 30 August 2021 Abstract: Introduction: Traumatic spinal cord injury (SCI), as a dangerous central nervous system damage, continues to threaten communities by imposing various disabilities and costs. Early adjustment of the immune system re- sponse using Myelin Basic Protein (MBP) immunization may prevent the SCI-related secondary damages. As a result, the current study is designed to review and analyse the evidence on active and passive immunization with MBP for treatment of traumatic SCI. Methods: Medline, Embase, Scopus, and Web of Science databases were systematically searched until the end of 2020. Criteria for inclusion in the current study included pre-clinical studies, which performed passive (injection of MBP-activated T cells) or active (administration of MBP or MBP- modified peptides) immunization with MBP after traumatic SCI. Exclusion criteria was defined as lack of a non- treated SCI group, lack of evaluation of locomotion, review studies, and combination therapy. Finally, analyses were conducted using STATA software, and a standardized mean difference (SMD) with a 95% confidence in- terval (CI) were reported. Results: Data from 17 papers were included in the present study. Finally, analysis of these data showed that passive immunization (SMD=0.87; 95%CI: 0.19-1.55; p=0.012) and active immuniza- tion (SMD=2.08, 95%CI: 1.42-2.73; p<0.001) for/with MBP both have good efficacy in improving locomotion following traumatic SCI. However, significant heterogeneity was observed in both of them. The most impor- tant sources of heterogeneity in active immunization were differences in SCI models, route of administration, time interval between SCI and transplantation, and type of vaccine used. In passive immunization, however, these sources were the model of SCI and the time interval between SCI and transplantation. Although, there was substantial heterogeneity among studies, subgroup analysis showed that active immunization improved loco- motion after traumatic SCI in all tested conditions (with differences in injury model, severity of injury, method of administration, different time interval between SCI to vaccination, etc.). Conclusion: The results of the present study demonstrated that immunization with MBP, especially in its active form, could significantly improve mo- tor function following SCI in rats and mice. Therefore, it could be considered as a potential treatment in acute settings such as emergency departments. However, the safety of this method is still under debate. Therefore, it is recommended for future research to focus on the investigation of safety of MBP immunization in animal studies, before conducting human clinical trials. Keywords: Early Medical Intervention; Emergency treatment; Immunization; Myelin basic protein; Spinal cord injuries Cite this article as: Yousefifard M, Madani Neishaboori A, Rafiei Alavi S N, Toloui MA, I M Gubari M, Zareie Shab Khaneh A, Karimi Ghah- farokhi M, Hosseini M. Active and Passive Immunization with Myelin Basic Protein as a Method for Early Treatment of Traumatic Spinal Cord Injury; a Meta-Analysis. Arch Acad Emerg Med. 2021; 9(1): e57. DOI: https://doi.org/10.22037/aaem.v9i1.1316. ∗Corresponding Author: Mostafa Hosseini; Department of Epidemiology and Biostatistics School of Public Health, Tehran University of Medical Sci- ences, Poursina Ave, Tehran, Iran. Email: mhossein110@yahoo.com; Tel: +982188989125; Fax: +982188989127, ORCID: https://orcid.org/0000-0002- 1334-246X. a: First and second authors have equally contributed to this work. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Yousefifard et al. 2 1. Introduction Spinal cord injury (SCI) is one of the most dangerous neu- rological disorders that mostly affects the young population, and causes long-term disabilities in this group of society. Un- fortunately, more than 90% of the patients suffer from long- term motor disabilities and about 78% of them experience severe to moderate pain. SCI and its complications impose significant direct and indirect costs on both the individual and the healthcare system; the annual costs of SCI are esti- mated at about 26270$ per patient (1). Current treatments have very low efficacy and can only alle- viate some of its symptoms. Medication therapy is the main- stay of current treatment methods. Not only has this treat- ment had very little effect on motor recovery (2), but also the unwanted side effects that occur with continued use of med- ications are a major barrier to their use (3). Current efforts in improving the recovery of central nervous system (CNS) fo- cus on two aspects: 1) stimulation of neurogenesis or regen- eration and 2) neuroprotection or prevention of secondary damage (4, 5). However, there is still significant disagree- ment over the new treatment strategies. For instance, older studies had demonstrated that inflammation caused by au- toimmune response leads to exacerbation of SCI and motor impairment (6, 7). Nonetheless, recent animal research showed that the post- injury autoimmune reactions provoke beneficial endoge- nous responses following SCI (8). These studies indicate that the presence of immune T cells in the injury site increases secretion of nervous growth factors, improves the tissue en- vironment surrounding the damaged neurons, protects the remaining myelin, and eventually, leads to enhancement of motor recovery (4). It has also been demonstrated that proper regulation of im- mune response following SCI may have an essential role in axonal regeneration, prevention of secondary injuries, and SCI recovery. In addition, local transplantation of macrophages was associated with some degree of motor re- covery in the literature (9, 10). Myelin Basic Protein (MBP) is a surface antigen expressed on cells in the CNS. Available studies show that transplantation of activated immune cells against this antigen is associated with improved motor recovery in animals with SCI (11, 12). Thus, transplantation of cells activated by this antigen, may selectively affect the CNS and reduce nonspecific inflamma- tory responses in other tissues (13). On the other hand, ad- ministration of this protein or similar peptides, as an active immunogenic process, could have significant effects on im- proving motor function following SCI (14-16). Although several studies that evaluate the effectiveness of ac- tive and passive immunization in SCI are available, conflict- ing findings have been reported between studies. For exam- ple, Rodríguez-Barrera et al. showed that active immuniza- tion with neural-derived peptides, such as MBP-related pep- tides, improves motor function following SCI (17). However, Ibara et al. showed that the use of this immunization has no effect on motor function following SCI (18). These inconsis- tencies have made it impossible to draw a general conclusion in this regard. On the other hand, it is not yet clear which ac- tive and inactive immunogenic methods are more effective in improving the motor function of animals. Accordingly, there is still no conclusion on the role of passive immunization with immune cells activated by MBP or on ac- tive immunization with injection of MBP and its derivatives in the treatment of SCI in the literature. Hence, the present study aims to perform a systematic review and meta-analysis to determine the effectiveness of passive or active immuniza- tion with MBP on motor recovery in animal models following SCI. 2. Methods 2.1. Study design PICO was defined as follows: Problem (P) included animals in which SCI injury was induced. Intervention (I) was the injection of MBP-activated T cells (passive immunization) or administration of MBP or MBP-modified peptides, induc- ing intrinsic immunity to MBP (active immunization). Com- parison (C) consisted of a comparison with control animals, which were induced with SCI but had not received treatment, and outcome (O) was an assessment of motor function by BBB testing. 2.2. Search strategy An extensive search was conducted on Medline, Embase, Scopus, and Web of Science databases until the end of 2020. Search strategy was designed based on keywords related to SCI and immunization/vaccination, which were obtained through searching databases such as Emtree (Embase) and Mesh (PubMed). Although only animal studies were included in the current systematic review, animal study filter was not applied in the search, in order to prevent the loss of relevant records. A manual search was also performed in the list of references of the relevant articles and highly related journals. To search for Grey literature, the thesis section was searched in the ProQuest database. In addition, Google and Google Scholar search engines were searched to find additional resources. Finally, authors of the relevant studies were contacted to gain access to their unpublished or pre-print data. Full electronic search strategy for all databases is presented in appendix 1. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 3 Archives of Academic Emergency Medicine. 2021; 9(1): e57 2.3. Selection criteria The inclusion criteria in the present study consisted of con- trolled studies that had evaluated the efficacy of immune cells activated against MBP protein in motor function im- provement after SCI. Controlled studies were defined as stud- ies that had a control group without any treatment (placebo group or vehicle group), in addition to the group treated with active/passive immunization with MBP. Since some articles were written in Chinese and Japanese, no language restric- tions were imposed. Irrelevant, duplicate and review studies were excluded. Moreover, lack of motor function evaluation and combination therapy were the other exclusion criteria in the current meta-analysis. 2.4. Data collection and quality assessment The search results in the databases were combined and duplicate studies were eliminated using Endnote software. Next, after screening of the titles and abstracts of the records by two independent reviewers, full texts of potentially rele- vant studies were obtained and then relevant studies were included. The final results of the systematic search in the present study were recorded in a checklist designed based on PRISMA statement (19). The extracted data consisted of study design, treated and control group characteristics (age, sex, spinal cord injury model, etc.), sample size, outcome (motor outcome) and possible biases. Considering that mo- tor function recovery following SCI needs a 4-week time win- dow after the injury in a rat model, studies with a follow-up period of less than four weeks were excluded. In cases that the aforementioned information was not reported, the cor- responding author of the study was contacted and asked to provide the required data. If the results were presented in the form of graphs, they were extracted using the method demonstrated by Sistorm and Mergo (20). In cases of dis- agreement between the two researchers, it would be resolved through discussion with a third reviewer. Quality assess- ment of the studies was conducted independently by the two researchers based on the recommended SYRCLE guide- line (21). This tool includes 10 domains of sequence gener- ation, baseline characteristics, allocation concealment, ran- dom housing, care-giver blinding, random outcome assess- ment, blinding of outcome assessor, incomplete outcome assessment, selective outcome assessment, and other risk of bias. Two independent reviewers rated each domain (as low risk, high risk, unclear) according to signaling questions presented in explanation and elaboration paper of SYRCLE guideline (21). Any disagreement was resolved by discussion. 2.5. Statistical analysis In all of the studies, the scores of the animals in the BBB test in treated and control groups were considered as the final outcome. Data were recorded as mean and standard deviation and analyzed using “metan” command in STATA 14.0 statistical software. The findings were reported as stan- dardized mean difference (SMD) and 95% confidence inter- val (95% CI). Heterogeneity between the studies was assessed using the I2 test and a p value of less than 0.1 was consid- ered as significant heterogeneity. If the studies were homo- geneous, the fixed effect model was performed, and in case of heterogeneity, subgroup analysis was conducted to deter- mine the source of the heterogeneity. Random effect model was performed in cases where the cause of heterogeneity was not clear. Meta-analyses were performed, only if the data were reported in at least two separate experiments. Finally, publication bias was investigated by performing Egger’s test and presenting a funnel Plot (22). 3. Results 3.1. Study characteristics Searching the databases eventually provided researchers with 1055 non-duplicate records. By reviewing the abstracts and titles of the records, the full text of 40 relevant articles were obtained and then studied in detail. Finally, the data of 17 articles (5, 11, 12, 14-18, 23-30) were included in the present meta-analysis (Figure 1). These pre-clinical articles consisted of 39 separate analyses (experiments), 36 of which were performed on rats and 3 were performed on mice. The animals were female in 38 of the experiments and male in only one. The models for the induction of SCI were contu- sion in 31, compression in four, hemisection in one and tran- section model in three experiments. The severity of injury was moderate in 22 and severe in 17 of the trials. The site of injury was thoracic in all of the experiments. Seven experi- ments had used prophylaxis vaccination and 32 of them per- formed the vaccination after the SCI. 25 experiments vacci- nated the subjects immediately after the SCI. 13 experiments conducted passive immunization by injecting MBP-activated T cells, while 26 experiments performed active immuniza- tion. Compounds used to induce active immunization in- cluded MBP, A91 (a peptide derived from MBP), and den- dritic cells pulsed with MBP or A91. Moreover, follow-up time ranged from 27 days to 112 days (Table 1). 3.2. Efficacy of passive immunization on motor function recovery after SCI The effect of passive immunization on improving the mo- tor function of animals following SCI was investigated in 13 experiments. Meta-analysis showed that passive immuniza- tion improved motor function of animals after SCI (SMD = 0.87; 95% CI: 0.19, 1.55; p = 0.012). Significant heterogeneity was observed in this section (I2 = 78.4%; p <0.001) (Figure 2). Therefore, subgroup analysis was conducted. The most im- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Yousefifard et al. 4 portant sources of heterogeneity and subgroup analysis re- sults are reported in Table 2. The model of injury and the time interval between SCI and transplantation were the most important sources of heterogeneity. Studies that used tran- section/hemisection models (I2 = 0.0%) and had a time inter- val of 1-9 days between SCI and transplantation (I2 = 49.9%) were found to be homogeneous. Interestingly, the efficacy of passive immunization on mo- tor recovery was affected by the diversities between the stud- ies. Passive immunization improved motor function only in models of contusion injury (SMD = 1.23, p <0.001), whereas such an effect was not observed in transection/hemisection models (SMD = -0.19; p = 0.565). Also, the use of passive immunization in severe SCI models had no effect on motor function of the animals (SMD = 0.47, p = 0.262), but in mod- erate injuries, it significantly enhanced motor function (SMD = 1.30, p = 0.018). In addition, intraperitoneal injection of MBP-activated T cells (SMD = 0.54, p = 0.173) and the admin- istration of this treatment immediately after SCI (SMD = 0.77, p = 0.052) had no effect on the motor function of animals. Finally, the impression is created that the positive effects of passive immunization is only observed in long term follow- up (p = 0.024) (Table 2). 3.3. Efficacy of active immunization on motor function recovery after SCI The effect of active immunization on the motor function of the animals was evaluated in 26 experiments. Meta-analysis of this section demonstrated that active immunization signif- icantly improves motor function following SCI (SMD = 2.08, 95% CI: 1.42, 2.73; p <0.001) (Figure 3). Significant hetero- geneity was observed in this part (I2 =86.4%, p <0.001). Sub- group analysis showed that differences in SCI model, route of administration, time interval between SCI and transplan- tation, and the type of vaccine inducing active immunization were the most important sources of heterogeneity. Studies that had used compression model to induce SCI (I2 = 0.0%), studies with intraperitoneal (I2 = 26.9%) or intrathecal ad- ministration (I2 = 0.0%), studies that performed immuniza- tion in the chronic phase (60 days after SCI) (I2 =16.8%), and studies that had used activated dendritic cells to create im- munization (I2 = 0.0%) were homogeneous. It is worth men- tioning that active immunization improved the motor func- tion in the animals in all test conditions (with differences in injury model, severity of injury, method of administration, etc.) (Table 3). 3.4. Publication bias and risk of bias assessment The SYRACLE tool was used to assess the risk of bias in the included studies. Accordingly, all of the studies in this re- view had low risk of bias in the baseline characteristic sec- tion. On the other hand, all of the articles had an unclear risk of bias on random housing. In both care giver blinding and allocation concealment items, there was one study with un- clear risk of bias, three had low risk of bias, and the others were classified as having high risk of bias. However, only two studies had high risk of bias in the blinding of outcome asses- sor section and the others were classified as having low risk of bias. More information on the risk of bias of the articles is shown in Table 4. It should be kept in mind that publica- tion bias was not observed in either active immunization (p = 0.131) or passive immunization studies (p = 0.272) (Figure 4). 4. Discussion The present study aimed to determine the efficacy of pas- sive and active immunization with MBP on motor function recovery following SCI in animal models. The obtained re- sults showed that overall, both passive and active immuniza- tion with MBP can improve motor function recovery follow- ing SCI in rats and mice. This substantiates previous find- ings in the literature indicating the positive effects of con- trolled activity of the immune system in the injury site. In other words, the autoimmunity that occurs due to the acti- vation of immune cells, (including T-helper 2, macrophages, and neutrophils), protects the spinal cord from further dam- age, whilst promoting tissue recovery (10, 11, 31). Based on the results of the current review, in general, active immunization has a greater effect on the protection and re- covery of the spinal cord following injury, compared to pas- sive immunization. This finding is very promising, as storage of antigens in the laboratory and the clinic is much more at- tainable than activated immune cells. Furthermore, injection of antigens is associated with less complications and side ef- fects. Previous studies have also noted the pathogenic effect of most injected T cells on the central nervous system (32). In addition, the formation of memory cells in active immu- nization provides a more durable immunity and it is expected to protect the injured spinal cord from further damage for a longer time. It has even been observed that in chronic condi- tions (60 days after injury) the cells formed under the influ- ence of active immunization could maintain their function and lead to recovery after spinal cord injury (17). Subgroup analysis showed that passive immunization is not effective in promoting motor recovery after SCI in severe or immediate administration after the injury. Hence, their ad- ministration is not recommended in such conditions. In con- trast, active immunization is less associated with the acuity of the injury and has significant efficacy in all conditions. This statement could be justified considering the vulnerability of cells to antigens (10). It may even be suggested that in situ- ations in which immunization is achieved by the injection of dendritic cells, the immunity is safer and more long lasting, This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 5 Archives of Academic Emergency Medicine. 2021; 9(1): e57 granted that the immune cells become activated inside the body of the animal itself (12, 23, 26). At last, it should be added that immunization, and especially active immunization, have shown favorable efficacy in ani- mal studies. Further investigations are recommended to fo- cus on the application of this method both for the treatment of SCI (23, 25, 27-30) and also prophylaxis (vaccination) (14, 15, 18) in high-risk groups, e.g. horse riders or rally drivers. However, the safety of this method is still under debate, as autoimmune diseases, such as multiple sclerosis, are caused by hyperreaction to intrinsic antigens, such as MBP (33). This issue may also be considered as one of the limitations of the present study, as none of the included studies had discussed it. However, there are studies that demonstrate the benefi- cial effects observed when administrating T Cell vaccines in Multiple Sclerosis patients (34). Hence, investigations on the safety of active/passive vaccination with MBP are strongly suggested to be carried out before conducting clinical trials. Moreover, another limitation of this study was the hetero- geneity of the articles. Considering the sources of this het- erogeneity, including the method of injury, the time interval between SCI and treatment, and the route of administration, it is proposed that further research should be undertaken re- garding the mentioned variables. Finally, due to the men- tioned limitations, conclusions about the application of ac- tive and passive immunization in SCI should be drawn with caution. 5. Conclusion Although the heterogeneity among the included studies in the present meta-analysis was significant, the result of this study showed that the immunization provided with MBP, es- pecially in its active form, significantly improves motor func- tion following SCI in rats and mice. However, future investi- gations are necessary in order to establish the efficacy of this method. In addition, safety of immunization with MBP is de- bated, both in active and passive immunization. Hence, con- sidering the possible complications of this method, such as autoimmunity, it is recommended for future researchers to investigate its safety by designing more animal experiments, before conducting clinical trials. 6. Declarations 6.1. Conflict of Interest There is no conflict of interest. 6.2. Funding This study has been funded and supported by Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran; Grant No: 95-01-38-31334. 6.3. Authors’ contribution Study design: MH, MY; Data gathering: MY, AMN, SNRA, AT; Analysis: MH, AZSK, and MKG MY; interpreting the results: All authors; Drafting: MY, AMN; Critically revised: All au- thors. 6.4. Acknowledgments None. References 1. Mann R, Schaefer C, Sadosky A, Bergstrom F, Baik R, Parsons B, et al. Burden of spinal cord injury-related neuropathic pain in the United States: retrospective chart review and cross-sectional survey. Spinal cord. 2013;51(7):564-70. 2. Backonja MM, Irving GA, Argoff C. Rational multidrug therapy in the treatment of neuropathic pain. Curr Pain Headache Rep. 2006;10:34-8. 3. Marineo G, Iorno V, Gandini C, Moschini V, Smith TJ. Scrambler therapy may relieve chronic neuropathic pain more effectively than guideline-based drug management: Results of a pilot, randomized, controlled trial. Journal of pain and symptom management. 2012;43(1):87-95. 4. Hauben E, Butovsky O, Nevo U, Yoles E, Moalem G, Agranov E, et al. Passive or active immunization with myelin basic protein promotes recovery from spinal cord contusion. The Journal of Neuroscience. 2000;20(17):6421-30. 5. Jones TB, Ankeny DP, Guan Z, McGaughy V, Fisher LC, Basso DM, et al. Passive or active immunization with myelin basic protein impairs neurological function and exacerbates neuropathology after spinal cord injury in rats. The Journal of neuroscience. 2004;24(15):3752-61. 6. Hausmann O. Post-traumatic inflammation following spinal cord injury. Spinal cord. 2003;41(7):369-78. 7. Brambilla R, Bracchi-Ricard V, Hu W-H, Frydel B, Bramwell A, Karmally S, et al. Inhibition of astroglial nu- clear factor KB reduces inflammation and improves func- tional recovery after spinal cord injury. The Journal of ex- perimental medicine. 2005;202(1):145-56. 8. Donnelly DJ, Popovich PG. Inflammation and its role in neuroprotection, axonal regeneration and functional re- covery after spinal cord injury. Experimental neurology. 2008;209(2):378-88. 9. Yoles E, Hauben E, Palgi O, Agranov E, Gothilf A, Co- hen A, et al. Protective autoimmunity is a physiological response to CNS trauma. The Journal of Neuroscience. 2001;21(11):3740-8. 10. Moalem G, Leibowitz–Amit R, Yoles E, Mor F, Cohen IR, Schwartz M. Autoimmune T cells protect neurons from secondary degeneration after central nervous system axo- This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Yousefifard et al. 6 tomy. Nature medicine. 1999;5(1):49-55. 11. Wang HJ, Hu JG, Shen L, Wang R, Wang QY, Zhang C, et al. Passive immunization with myelin basic protein activated T cells suppresses axonal dieback but does not promote axonal regeneration following spinal cord hemi- section in adult rats. The International journal of neuro- science. 2012;122(8):458-65. 12. Wang Y, Li J, Kong P, Zhao S, Yang H, Chen C, et al. Enhanced expression of neurotrophic factors in the in- jured spinal cord through vaccination with myelin ba- sic protein-derived peptide pulsed dendritic cells. Spine. 2015;40(2):95-101. 13. Liu H, Shiryaev SA, Chernov AV, Kim Y, Shubayev I, Remacle AG, et al. Immunodominant fragments of myelin basic protein initiate T cell-dependent pain. Journal of neuroinflammation. 2012;9:119. 14. Hauben E, Butovsky O, Nevo U, Yoles E, Moalem G, Agranov E, et al. Passive or active immunization with myelin basic protein promotes recovery from spinal cord contusion. The Journal of neuroscience : the official jour- nal of the Society for Neuroscience. 2000;20(17):6421-30. 15. Ibarra A, Sosa M, García E, Flores A, Cruz Y, Mestre H, et al. Prophylactic neuroprotection with A91 improves the outcome of spinal cord injured rats. Neuroscience letters. 2013;554:59-63. 16. Rodríguez-Barrera R, Fernández-Presas AM, García E, Flores-Romero A, Martiñón S, González-Puertos VY, et al. Immunization with a neural-derived peptide protects the spinal cord from apoptosis after traumatic injury. BioMed research international. 2013;2013:827517. 17. Rodríguez-Barrera R, Flores-Romero A, García E, Fernández-Presas AM, Incontri-Abraham D, Navarro- Torres L, et al. Immunization with neural-derived peptides increases neurogenesis in rats with chronic spinal cord in- jury. CNS Neuroscience and Therapeutics. 2020;26(6):650- 8. 18. Ibarra A, Hauben E, Butovsky O, Schwartz M. The ther- apeutic window after spinal cord injury can accommodate T cell-based vaccination and methylprednisolone in rats. The European journal of neuroscience. 2004;19(11):2984- 90. 19. Moher D, Liberati A, Tetzlaff J, Altman DG. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. Annals of internal medicine. 2009;151(4):264-9. 20. Sistrom CL, Mergo PJ. A simple method for obtaining original data from published graphs and plots. American Journal of Roentgenology. 2000;174(5):1241-4. 21. Hooijmans CR, Rovers MM, de Vries RBM, Leenaars M, Ritskes-Hoitinga M, Langendam MW. SYRCLE’s risk of bias tool for animal studies. BMC Medical Research Methodol- ogy. 2014;14(1):43. 22. Egger M, Smith GD, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. Bmj. 1997;315(7109):629-34. 23. Hauben E, Gothilf A, Cohen A, Butovsky O, Nevo U, Smirnov I, et al. Vaccination with dendritic cells pulsed with peptides of myelin basic protein promotes functional recovery from spinal cord injury. The Journal of neuro- science : the official journal of the Society for Neuro- science. 2003;23(25):8808-19. 24. Hu JG, Shen L, Wang R, Wang QY, Zhang C, Xi J, et al. Effects of Olig2-overexpressing neural stem cells and myelin basic protein-activated T cells on recovery from spinal cord injury. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics. 2012;9(2):422-45. 25. Hu JG, Shi LL, Chen YJ, Xie XM, Zhang N, Zhu AY, et al. Differential effects of myelin basic protein-activated Th1 and Th2 cells on the local immune microenvironment of injured spinal cord. Exp Neurol. 2016;277:190-201. 26. Liu M, Zhao J, Liang H, Bian X. Vaccination with den- dritic cells pulsed with homogenate protein of spinal cord promotes functional recovery from spinal cord injury in mice. Spinal cord. 2009;47(5):360-6. 27. Lü HZ, Xu L, Zou J, Wang YX, Ma ZW, Xu XM, et al. Ef- fects of autoimmunity on recovery of function in adult rats following spinal cord injury. Brain, behavior, and immu- nity. 2008;22(8):1217-30. 28. Martiñon S, García E, Flores N, Gonzalez I, Ortega T, Buenrostro M, et al. Vaccination with a neural-derived peptide plus administration of glutathione improves the performance of paraplegic rats. The European journal of neuroscience. 2007;26(2):403-12. 29. Martiñón S, García E, Gutierrez-Ospina G, Mestre H, Ibarra A. Development of protective autoimmunity by im- munization with a neural-derived peptide is ineffective in severe spinal cord injury. PloS one. 2012;7(2):e32027. 30. Martiñón S, García-Vences E, Toscano-Tejeida D, Flores-Romero A, Rodriguez-Barrera R, Ferrusquia M, et al. Long-term production of BDNF and NT-3 induced by A91-immunization after spinal cord injury. BMC neuro- science. 2016;17(1):42. 31. Schwartz M, Raposo C. Protective autoimmunity: a unifying model for the immune network involved in CNS repair. The Neuroscientist. 2014;20(4):343-58. 32. Held W, Meyermann R, Qin Y, Mueller C. Perforin and tumor necrosis factor α in the pathogenesis of experimen- tal allergic encephalomyelitis: comparison of autoantigen induced and transferred disease in Lewis rats. Journal of autoimmunity. 1993;6(3):311-22. 33. Zang YC, Li S, Rivera VM, Hong J, Robinson RR, Breit- bach WT, et al. Increased CD8+ cytotoxic T cell responses to myelin basic protein in multiple sclerosis. The Journal This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 7 Archives of Academic Emergency Medicine. 2021; 9(1): e57 of Immunology. 2004;172(8):5120-7. 34. Zhang J, Medaer R, Stinissen P, Hafler D, Raus J. MHC-restricted depletion of human myelin basic protein-reactive T cells by T cell vaccination. Science. 1993;261(5127):1451-4. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Yousefifard et al. 8 Appendix 1: Search syntaxes for current study PubMed ((Immunization[Mesh] OR Active Immunization*[Mesh] OR Passive Immunization*[Mesh] OR Vaccination[Mesh] OR Autoimmu- nity[Mesh] OR Immunization, Passive/methods[Mesh] OR Immunization[tiab] OR Active Immunization*[tiab] OR Passive Immuniza- tion*[tiab] OR Vaccination[tiab] OR Autoimmunity[tiab] OR Immunization, Passive/methods[tiab] OR Autoimmunities[tiab] OR au- toimmune Response*[tiab] OR Myelin Basic Protein[tiab] OR Immunization with neural derived peptides[tiab] OR A91[tiab])) AND (Spinal cord injuries[mh] OR Spinal cord contusion[tiab] OR Spinal cord transection[tiab] OR Injured spinal cord[tiab] OR spinal cord Traum*[tiab] OR Spinal cord Hemisection[tiab] OR Spinal compression[tiab] OR traumatic Myelopath*[tiab] OR spinal cord Lacera- tio*[tiab] OR post-traumatic Myelopath*[tiab]) Embase 1- ’active immunization’/exp OR ’passive immunization’/exp OR ’vaccination’/exp OR ’myelin basic protein’/exp 2- ’spinal cord injury’/exp OR ’experimental spinal cord injury’/exp OR ’spinal cord transsection’/exp OR ’cervical spinal cord in- jury’/exp OR ’cervical spinal cord injury’/exp OR ’cervical spinal cord injury’/exp OR ’lumbar spinal cord’/exp OR ’photochemical spinal cord injury’/exp OR ’spinal paralysis’/exp OR ’spinal cord transverse lesion’/exp 3- #1 AND #2 Scopus ( ( TITLE-ABS-KEY ( "active immunization" ) OR TITLE-ABS-KEY ( "passive immunization" ) OR TITLE-ABS-KEY ( "vaccination" ) OR TITLE-ABS-KEY ( "myelin basic protein" ) OR TITLE-ABS-KEY ( "Myelin Basic Protein" ) OR TITLE-ABS-KEY ( "Immunization with neural derived peptides" ) OR TITLE-ABS-KEY ( "A91" ) ) ) AND ( ( ( TITLE-ABS-KEY ( "spinal cord injuries" ) OR TITLE-ABS-KEY ( "spinal cord injury" ) OR TITLE-ABS-KEY ( "spinal cord transection" ) OR TITLE-ABS-KEY ( "spinal cord hemisection" ) OR TITLE- ABS-KEY ( "injured spinal cord" ) OR TITLE-ABS-KEY ( "spinal cord trauma" ) OR TITLE-ABS-KEY ( "spinal compression" ) OR TITLE- ABS-KEY ( "spinal cord contusion" ) OR TITLE-ABS-KEY ( "photochemical spinal cord injury" ) OR TITLE-ABS-KEY ( "spinal paralysis" ) ) ) ) Web of Science ((TS="active immunization" OR "passive immunization" OR "vaccination" OR "myelin basic protein" OR "Myelin Basic Protein" OR "Immunization with neural derived peptides" OR "A91") AND (TS="spinal cord injuries" OR "spinal cord injury" OR "spinal cord transection" OR "spinal cord hemisection" OR "injured spinal cord" OR "spinal cord trauma" OR "spinal compression" OR "spinal cord contusion" OR "photochemical spinal cord injury" OR "spinal paralysis") ) This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 9 Archives of Academic Emergency Medicine. 2021; 9(1): e57 Table 1: Characteristics of included studies Study Sex, Strain, Species Severity of injury; Model; Injury Location Injury to treatment* (day) Vaccine Number of admin- istrations Type of Treatment Transplantation route Number of cells Follow- up days Hauben, 2000 (14) Female, Lewis, Rat Severe; Contusion, transection; T9, T7 -7, 0, 7 TMBP cells, MBP-IFA 1 Passive, active IP, SC 1.0 × 107 76 Hauben, 2003 (23) Female, Lewis, Rat Severe; Contusion; T8 0 DC-MBP, DC-A91 1 Active IS, IV, SC 5.0 × 105 1.0 × 107 2.0 × 107 76 Hu, 2012 (24) Female, Lewis, Rat Moderate; Contusion; T9 9 TMBP cells 1 Passive IV 4.0 × 105 49 Hu, 2016 (25) Female, Lewis, Rat Moderate; Contusion; T9 0 T-helper 1 MBP cell, T-helper 2 MBP cell 1 Passive IV 2.0 × 107 42 Ibarra, 2004 (18) Female, Lewis and SD, Rat Severe; Contusion; T9 -7 A91-CFA 1 Active SC NA 72 Ibarra, 2013 (15) Female, SD, Rat Moderate; Contusion; T9 -40 A91-CFA 1, 2 Active SC NA 63 Jones, 2004 (5) Female, Lewis, Rat Moderate, Severe; Contusion, Transection; T8 -7, 0 TMBP cells, MBP-IFA, MBP-CFA 1 Passive, active IP, SC 1.0 × 107 43, 63 Liu, 2009 (26) NR, BALB/C, Mice Moderate; Compression; T10 1 DC-MBP 1 Active IP, IS 5.0 × 105 84 Lu, 2008 (27) Female and Male, SD, Rat Moderate; Contusion; T9 0 TMBP cells 1 Passive IV 2.0 × 107 56 Martinon, 2007 (28) Female, SD, Rat Moderate; Contusion, compression; T9 0 A91-CFA 1, 2 Active SC NA 77, 84 Martinon, 2013 (29) Female, SD, Rat Moderate, severe; Contusion, transection; T9 0 A91-CFA 1 Active SC NA 56 Martinon, 2016 (30) Female, SD, Rat Moderate; Contusion; T9 0 A91-CFA 1 Active SC NA 112 Rodríguez- Barrera, 2013 (16) Female, SD, Rat Moderate; Contusion; T9 0 A91-CFA 1 Active SC NA 30 Rodríguez- Barrera, 2020a (17) Female, SD, Rat Moderate; Contusion; T9 60 A91 2 Active SC NA 60 Rodríguez- Barrera, 2020b (17) Female, SD, Rat Moderate; Contusion; T9 60 A91-CFA 1 Active SC NA 60 Wang, 2012 (11) Female, SD, Rat Severe; Transection; T9 0 TMBP cells 1 Passive IV 2.0 × 107 56 Wang, 2015 (12) NR, BALB/C, Mice Moderate; Compression; T9 1 DC-A91 1 Active IP 1.0 × 106 27 CFA: Complete Freund’s adjuvant; DC: Dendritic cells; DC-MBP: DCs pulsed with myelin basic protein; DC-A91: DCs pulsed with A91 peptide; IFA: Incomplete Freund’s adjuvant; IP: Intraperitoneal; IS: Intraspinal; IV: Intravenous; MBP: Myelin basic protein; NA: Not applicable; SC: Subcutaneous; SD: Sprague-Dawley; T: Thoracic regions; TMBP: Myelin basic protein-activated T cells; MBP-IFA: MBP emulsified in incomplete Freund’s adjuvant; MBP-CFA: MBP emulsified in complete Freund’s adjuvant. *, Negative numbers refer to pre-treatment protocols. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Yousefifard et al. 10 Table 2: Subgroup analysis for effect of passive immunization with Myelin Basic Protein (MBP) on motor function recovery after spinal cord injury (SCI) Variable No. experiment Heterogeneity (p value) SMD (95% CI) P Model of injury Contusion 10 81.1% (<0.001) 1.23 (0.39, 2.07) <0.001 Transection/hemisection 3 0.0% (0.796) -0.19 (-0.81, 0.45) 0.565 Severity of injury Moderate 6 84.6% (<0.001) 1.39 (0.24, 2.55) 0.018 Severe 7 71.3% (0.002) 0.47 (-0.35, 1.30) 0.262 Route of administration Intraperitoneal 7 68.7% (0.004) 0.54 (-0.24, 1.32) 0.173 Intravenous 6 85.7% (<0.001) 1.33 (0.10, 2.56) 0.034 Time interval between SCI and transplantation Immediately after SCI 11 79.6% (<0.001) 0.77 (-0.006, 1.55) 0.052 1-9 days after SCI 2 49.9% (0.158) 1.38 (0.32, 2,44) 0.011 Follow-up duration < 8 weeks 4 80.0% (0.002) 0.51 (-0.50, 1.52) 0.327 ≥ 8 weeks 15 80.1% (<0.001) 1.11 (0.14, 2.07) 0.024 CI: confidence interval; SMD: Standardized mean difference. Table 3: Subgroup analysis for effect of active immunization with Myelin Basic Protein (MBP) on motor function recovery after spinal cord injury (SCI) Variable No. experiment Heterogeneity (p value) SMD (95% CI) P Model of injury Contusion 21 88.5% (<0.001) 2.42 (1.61, 3.23) <0.001 Compression 4 0.0% (0.567) 1.28 (0.72, 1.84) <0.001 Transection 1 NA NA NA Severity of injury Moderate 16 90.1% (<0.001) 2.67 (1.68, 3.68) <0.001 Severe 10 68.9% (0.001) 1.27 (0.59, 1.95) <0.001 Route of administration Intraperitoneal 2 26.9% (0.242) 1.49 (0.40, 2.90) 0.008 Intravenous 1 NA NA NA Subcutaneous 19 89.8% (<0.001) 2.29 (1.44, 3.14) <0.001 Intraspinal 4 0.0% (0.981) 1.64 (1.01, 2.27) <0.001 Time interval between SCI and transplantation Prophylaxis 7 88.4% (<0.001) 1.50 (0.28, 2.71) 0.016 Immediately after SCI 17 87.3% (<0.001) 2.42 (1.52, 3.31) <0.001 60 days after SCI 2 16.8% (0.273) 1.94 (1.10, 2,77) <0.001 Type of vaccine MBP or A91 base antigens 18 90.1% (<0.001) 1.11 (0.85, 1.36) <0.001 Activated dendritic cells 8 0.0% (0.446) 1.73 (1.23, 2.22) <0.001 Follow-up duration < 8 weeks 4 81.1% (<0.001) 5.12 (0.50, 9.73) 0.030 ≥ 8 weeks 21 95.8% (<0.001) 1.67 (1.10, 2.24) <0.001 CI: confidence interval; SMD: Standardized mean difference. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 11 Archives of Academic Emergency Medicine. 2021; 9(1): e57 Table 4: Risk of bias assessment of included studies Study Sequence genera- tion Baseline charac- teristics Allocation conceal- ment Random housing Care- giver blinding Random outcome assessment Blinding of outcome assessor Incomplete outcome assessment Selective outcome assessment Other Hauben, 2000 p p p ? p p p p ? p Hauben, 2003 p p ? ? ? p p p ? p Hu, 2012 - p - ? - p p p p p Hu, 2016 - p - ? - - p p p p Ibarra, 2004 - p - ? - - - ? ? ? Ibarra, 2013 - p - ? - - p p ? ? Jones, 200 p p - ? - p p p ? ? Liu, 2009 p p p ? p p p p ? p Lu, 2008 ? p - ? - ? - ? p p Martinon, 2007 - p - ? - - p ? ? ? Martinon, 2013 - p - ? - - p ? ? ? Martinon, 2016 p p - ? - p p ? ? p Rodríguez- Barrera, 2013 - p - ? - - p ? ? ? Rodríguez- Barrera, 2020a p p p ? p p p p ? p Rodríguez- Barrera, 2020b ? p - ? - p p ? ? p Wang, 2012 p p - ? - p p ? ? p Wang, 2015 ? p - ? - - p ? ? p p : Low risk of bias; ?: Unclear risk of bias; -: High risk of bias Figure 1: Flowchart of selecting related studies This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Yousefifard et al. 12 Figure 2: Forest plot for effect of passive immunization with Myelin Basic Protein (MBP) on motor function recovery after spinal cord injury. SMD: Standardized mean difference; CI: Confidence interval. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem 13 Archives of Academic Emergency Medicine. 2021; 9(1): e57 Figure 3: Forest plot for effect of active immunization with Myelin Basic Protein (MBP) on motor function recovery after spinal cord injury. SMD: Standardized mean difference; CI: Confidence interval. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem M. Yousefifard et al. 14 Figure 4: Funnel plot for assessment of publication bias in studies assessing the effect of passive and active immunization with Myelin Basic Protein (MBP) on motor function recovery after spinal cord injury. SMD: Standardized mean difference. This open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0). Downloaded from: http://journals.sbmu.ac.ir/aaem Introduction Methods Results Discussion Conclusion Declarations References