Toxoplasma gondii Migration within and Infection of Human Retina

Abstract

Toxoplasmic retinochoroiditis is a common blinding retinal infection caused by the parasite, Toxoplasma gondii. Basic processes relating to establishment of infection in the human eye by T. gondii tachyzoites have not been investigated. To evaluate the ability of tachyzoites to navigate the human retina, we developed an ex vivo assay, in which a suspension containing 1.5×107 parasites replaced vitreous in a posterior eyecup. After 8 hours, the retina was formalin-fixed and paraffin-embedded, and sections were immunostained to identify tachyzoites. To determine the preference of tachyzoites for human retinal neuronal versus glial populations, we infected dissociated retinal cultures, subsequently characterized by neuron-specific enolase or glial fibrillary acidic protein expression, and retinal cell lines, with YFP-expressing tachyzoites. In migration assays, retinas contained 110–250 live tachyzoites; 64.5–95.2% (mean = 79.6%) were localized to the nerve fiber layer, but some were detected in the outer retina. Epifluorescence imaging of dissociated retinal cultures 24 hours after infection indicated preferential infection of glia. This observation was confirmed in growth assays, with significantly higher (p≤0.005) numbers of tachyzoites measured in glial verus neuronal cell lines. Our translational studies indicate that, after entering retina, tachyzoites may navigate multiple tissue layers. Tachyzoites preferentially infect glial cells, which exist throughout the retina. These properties may contribute to the success of T. gondii as a human pathogen.

Infection and characterization of Toxoplasma gondii in human induced neurons from patients with brain disorders and healthy controls

“…Second, iN cells display key neuronal traits, such as action potentials that are not observed in less differentiated cells, including neuroblastoma cells. While there are a few reports of T. gondii infection in human primary neuronal cultures derived from retina of cadavers [29] or aborted fetuses [30], iN cells have a major advantage over these earlier cell culture that neuronal cells can be obtained from living subjects with defined genetic and clinical characteristics at the individual levels.…”

Expression of Long Non-Coding RNAs by Human Retinal Müller Glial Cells Infected with Clonal and Exotic Virulent Toxoplasma gondii

“…However, they are unable to control tachyzoite proliferation alone [18]. Müller cells also are a preferential target of T. gondii in the human retina-Furtado et al [19] highlighted that Müller cells are more susceptible to the infection than retinal neurons. Along with ganglion neuronal cells, Müller cells are the intraocular cell population that harbors the latent form of the parasite-the bradyzoite [20][21][22][23].…”

“…The involvement of lncRNAs in T. gondii infection of Müller cells is unstudied. Indeed, there is little published literature on the role of Müller cells during a T. gondii infection [18,19,36], or during intracellular pathogen infection in general [37,38]. Here, we were interested in the lncRNA response of Müller cells to infection with virulent strains of T. gondii, with a focus on the acute immune response.…”

From the blood to the brain: avenues of eukaryotic pathogen dissemination to the central nervous system

“…Interestingly, human brain endothelial cells are more permissive to T. gondii replication than neurons or microglia [10]. The extracellular parasite can also migrate through multiple tissue layers of the human retina [11]. Infection enhances the expression of the host adhesion molecules ICAM-1, VCAM-1, and ALCAM in the CNS [6,12].…”