Invasion of human retinal vascular endothelial cells by Toxoplasma gondii tachyzoites.
BACKGROUND
Toxoplasma gondii infection is a leading cause of posterior uveitis. Human retinal endothelial cells (HREC) are more susceptible to infection with T gondii tachyzoites than other subpopulations of endothelial cells. It is hypothesised that this phenomenon reflects differences in invasion efficiency.


METHODS
YFP-expressing RH strain T gondii tachyzoites were added to confluent HREC or human dermal endothelial cells (HDEC) (MOI = 50:1). Tachyzoite invasion after 1 h was determined by microplate reading of fluorescence intensity or parasite counts obtained using image analysis software. Selected cultures were incubated for three subsequent days, at which time fluorescence intensity indicated intracellular tachyzoite proliferation.


RESULTS
HREC-tachyzoite cultures were more fluorescent than HDEC-tachyzoite cultures after 1 h (p = 0.020, paired t test, 3 experiments). Parasite counts also indicated that more tachyzoites invaded HREC than HDEC (p = 0.042, paired t test, 5 experiments). At 3 days, fluorescence intensity remained higher in HREC-tachyzoite cultures (p< or =0.002, t test, 3 experiments).


CONCLUSIONS
In culture, T gondii tachyzoites invade HREC with greater efficiency than they invade HDEC. This observation suggests that the relative susceptibility of HREC to infection may reflect a high efficiency of tachyzoite invasion which may be relevant to understanding how T gondii infects human retina.
Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, OR 97239, USA.
D O
DO
Zamora
J T
JT
Rosenbaum
J R
JR
Smith
D000818:Animals; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000469:parasitology*; D006790:Host-Parasite Interactions; D006801:Humans; D007091:Image Processing, Computer-Assisted; D010274:Parasitology / Q000379:methods; D012171:Retinal Vessels; D014122:Toxoplasma / Q000502:physiology*; D014126:Toxoplasmosis, Ocular / Q000469:parasitology*