Purchase this article with an account.
Carlos Subauste, Jennifer Van Grol, Saad Saffo, Jose-Andres Portillo, Genevieve Okenka; CD40 Expressed on Endothelial Cells Enhances Resistance to Ocular Toxoplasmosis. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2779.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Toxoplasma gondii is a major cause of infectious retinitis worldwide. The parasite disseminates through the bloodstream leading to ocular invasion. While endothelial cells are thought to be important in the pathogenesis of ocular toxoplasmosis, their in vivo role in this disease has not been explored. CD40 is crucial for protection against ocular toxoplasmosis. We determined whether isolated expression of CD40 on endothelial cells contributes to protection against toxoplasmosis.
Transgenic CD40-/- mice where CD40 expression was rescued in endothelial cells were generated by breeding CD40-/- Tie1-tTA with CD40-/- pTet-CD40 mice. Mice were infected with ME49 T. gondii. T. gondii DNA and mRNA levels of IFN-gamma, TNF-alpha, NOS2 were examined by qPCR. Tissues were examined for histopathology. Endothelial cells were infected in vitro with T. gondii and examined using light and fluorescent microscopy.
Transgenic CD40-/- mice conditionally rescued to express CD40 on endothelial cells (Trg-CD40) exhibited lower parasite load and diminished histopathology in the eye compared to control transgenic CD40-/- mice (Trg-Ctr). Protection against ocular toxoplasmosis was not due to increased expression of IFN-gamma, TNF-alpha and NOS2 or enhanced induction of T. gondii-reactive T cells. Furthermore, leukocyte recruitment to the eye was similar amongst transgenic mice. Engagement of CD40 on endothelial cells resulted in killing of T. gondii in vitro. CD40 stimulation increased expression of the autophagy proteins Beclin 1 and LC3 II, enhanced autophagy flux and led to recruitment of LC3 around the parasites. Fusion with late endosomes/lysosomes occurred in a Beclin 1-dependent manner and led to lysosomal degradation and killing of T. gondii.
These studies provide the first evidence of the important in vivo role of endothelial cells in protection against toxoplasmosis. They also demonstrate that CD40 expression in a non-hematopoietic cell confers resistance against an infectious organism. These studies suggest that CD40 on endothelial cells contributes to host protection by inducing direct toxoplasmacidal activity in these cells.
This PDF is available to Subscribers Only