Spinal cord pathology in chronic experimental Toxoplasma gondii infection

Infection with the protozoan Toxoplasma (T.) gondii causes chronic infection of the central nervous system and can lead to life-threatening encephalomyelitis in immunocompromised patients. While infection with T. gondii has long time been considered asymptomatic in immunocompetent hosts, this view is challenged by recent reports describing links between seropositivity and behavioral alterations. However, past and current researches are mainly focused on the brain during Toxoplasma encephalitis, neglecting the spinal cord as a key structure conveying brain signals into motion. Therefore, our study aimed to fill the gap and describes the spinal cord pathology in an experimental murine model of toxoplasmosis. In the spinal cord, we found distinct histopathological changes, inflammatory foci and T. gondii cysts similar to the brain. Furthermore, the recruitment of immune cells from the periphery was detected. Moreover, resident microglia as well as recruited monocytes displayed an increased MHC classes I and II expression. Additionally, the expression of pro- and anti-inflammatory cytokines was enhanced in the brain as well as in the spinal cord. In summary, the pathology observed in the spinal cord was similar to the previously described changes in the brain during the infection. This study provides the first detailed description of histopathological and immunological alterations due to experimental T. gondii induced myelitis in mice. Thus, our comparison raises awareness of the importance of the spinal cord in chronic T. gondii infection.