Toxoplasma gondii: A possible etiologic agent for Alzheimer's disease

Abstract

Toxoplasma gondii ( T. gondii ) is one of the most pervasive neurotropic pathogens causing different lesions in a wide variety of mammals as intermediate hosts, including humans. It is estimated that one-third of the world population is infected with T. gondii ; however, for a long time, there has been much interest in the examination of the possible role of this parasite in the development of mental disorders, such as Alzheimer's disease (AD). T. gondii may play a role in the progression of AD using mechanisms, such as the induction of the host's immune responses, inflammation of the central nervous system (CNS), alteration in the levels of neurotransmitters, and activation of indoleamine-2,3-dyoxigenase. This paper presents an appraisal of the literature, reports, and studies that seek to the possible role of T. gondii in the development of AD. For achieving the purpose of the current study, a search of six English databases (PubMed, ScienceDirect, Web of Science, Scopus, ProQuest, and Google Scholar) was performed. The results support the involvement of T. gondii in the induction and development of AD. Indeed, T. gondii can be considered a risk factor for the development of AD and requires the special attention of specialists and patients. Furthermore, the results of this study may contribute to prevent or delay the progress of AD worldwide. Therefore, it is required to carry out further studies in order to better perceive the parasitic mechanisms in the progression of AD.

Gut and Brain: Investigating Physiological and Pathological Interactions Between Microbiota and Brain to Gain New Therapeutic Avenues for Brain Diseases

“…It has been described that it can induce immune response in the host and inflammation in the CNS, alteration in the levels of neurotransmitters, and direct infections of neuronal and astrocytic cells (in rat primary cell culture) ( Luder et al, 1999 ). For these reasons, T. gondii can be considered a possible etiologic risk factor for Alzheimer’s disease ( Nayeri et al, 2021 ).…”

The Defensive Interactions of Prominent Infectious Protozoan Parasites: The Host’s Complement System

“…In addition, Toxoplasma infection can increase neural cell death, alteration in neural gene expression and the release of inflammatory mediators in neurospheres [ 132 ]. Thus, this infection could be correlated with psychiatric diseases and human CNS disorders including Alzheimer, dementia, depression and schizophrenia [ 54 , 133 , 134 , 135 , 136 ]. On the other hand, due to the overexpression of complement components in Toxoplasma -infected brain [ 53 , 63 ], and the upregulation of C1q, C3, and C4b in some mental disorders including schizophrenia, alzheimer’s disease, aging and multiple sclerosis [ 54 , 137 , 138 , 139 , 140 ], it could be interesting to focus on therapeutic studies that share more information regarding the possible correlations between parasitic disease including toxoplasmosis and mental disorders and their association with the complement system.…”

Studies on the mechanism of Toxoplasma gondii Chinese 1 genotype Wh6 strain causing mice abnormal cognitive behavior

“…Chronic T. gondii infection affects almost one-third of the global population [4,5]. Numerous epidemiological statistics suggested that the positive rate of serum Toxoplasma antibodies in AD patients was higher than that in the control group [6]. Toxoplasma gondii can enter the brain from various anatomical sites to form tissue cysts through the blood-brain barrier and erode neurons, astrocytes and microglia [7][8][9].…”