Abstract
Purpose:
Autophagy is an important catabolic process of the cell, and also an essential defense mechanism. Our study demonstrates a unique role of autophagy in regulating herpes simplex virus type-1 (HSV-1) infection, which has been debatable and poorly defined for ocular infection.
Methods:
Multiple methods including starvation, physical stress, and pharmacological agents including proteosomal inhibitors, Bafilomycin A1, and Chloroquine were used to modulate autophagy in human corneal epithelial cells. Flow cytometry, fluorescence microscopy, and confocal fluorescence microscopy were used for monitoring and quantitative assessment of LC3-GFP or HcRed-LC3 autophagosomal punctae. Quantitative PCR was used for HSV genome quantification and immunoblotting to assess autophagy proteins. Wild-type (WT) or ATG5-/- MEFs were also used to study infection and autophagy.
Results:
Utilizing a comprehensive approach, we show that inducing autophagy of host cells suppresses HSV-1 infection in ocular cells that represent natural targets of HSV infection in vivo. Measuring the autophagic response of cells to HSV infection, we found that HSV requires a “normo-autophagic” state in host cells for productive infection. Suppression of this physiologically normal level of autophagy dramatically diminished the viral infection and resulted in a measureable loss of viral DNA copy numbers. Along these lines, ATG5-/- mouse embryo fibroblasts showed a clear loss of productive infection. Inducing autophagy, on the other hand, also had detrimental effects on viral growth and copy numbers.
Conclusions:
Overall, our findings suggest a model, whereby HSV-1, in order to support its own replication, fine-tunes the autophagic activity of the host, preventing induction of autophagy that suppresses the infection, while maintaining an intermediate level of autophagy required for virus replication. Our work establishes the existence of various tints of autophagy with distinct biological functions, and provides a druggable pathway for ocular herpes management.