Background Toxoplasma multiplication and its persistence into the brain cause a local neuroinflammatory reaction, resulting synthesis of neurotransmitters involved in neurological disorders, especially schizophrenia. The Matrix metallopeptidase 9 (MMP-9) protein can play a major role in this neuroinflammation. It can promote extravasation and migration of infected immune cells into the brain. The objectives of this study are to determine the possible association between schizophrenia and toxoplasmosis and highlight the existence of gene polymorphism encoding MMP-9 protein’s in patients presented both schizophrenia and toxoplasmosis. Methods A case-control study was conducted on 150 patients with schizophrenia (case group), and 150 healthy persons (control group). Groups were matched with age, gender, and place of residence. The survey was conducted using a questionnaire and a serological profile assay for specific IgG and IgM antibodies against T. gondii. Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) of gene polymorphism encoding MMP-9 was performed on 83 cases selected randomly. Results Data show a significant association between toxoplasmosis (IgM+/IgG+ serological profile) and schizophrenia. Significant effects of raw meat consumption and contact with cats have been associated with the occurrence of schizophrenia. PCR-RFLP shows the presence of muted allele of MMP-9 gene in selected cases whose present T. gondii serological profile IgM+/IgG+ and IgM-/IgG+ respectively. Conclusion Toxoplasmosis may be one of the etiological causes of schizophrenia, and MMP-9 gene polymorphism could be involved in the occurrence mechanism of this pathology following Toxoplasma infection.

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