Dengue virus infection induces autophagy: an in vivo study

Ying-Ray Lee,Trai-Ming Yeh,Huan-Yao Lei,Szu-Han Kuo,Yee-Shin Lin,Hsuan-Yun Hu,Hsiao-Sheng Liu,Ching-Chuan Liu

doi:10.1186/1423-0127-20-65

Ying-Ray Lee, Trai-Ming Yeh + Show 6 more

Open Access

https://doi.org/10.1186/1423-0127-20-65

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Abstract

BackgroundWe and others have reported that autophagy is induced by dengue viruses (DVs) in various cell lines, and that it plays a supportive role in DV replication. This study intended to clarify whether DV infection could induce autophagy in vivo. Furthermore, the effect of DV induced autophagy on viral replication and DV-related pathogenesis was investigated.Results and conclusionsThe physiopathological parameters were evaluated after DV2 was intracranially injected into 6-day-old ICR suckling mice. Autophagy-related markers were monitored by immunohistochemical/immunofluorescent staining and Western blotting. Double-membrane autophagic vesicles were investigated by transmission-electron-microscopy. DV non-structural-protein-1 (NS1) expression (indicating DV infection) was detected in the cerebrum, medulla and midbrain of the infected mice. In these infected tissues, increased LC3 puncta formation, LC3-II expression, double-membrane autophagosome-like vesicles (autophagosome), amphisome, and decreased p62 accumulation were observed, indicating that DV2 induces the autophagic progression in vivo. Amphisome formation was demonstrated by colocalization of DV2-NS1 protein or LC3 puncta and mannose-6-phosphate receptor (MPR, endosome marker) in DV2-infected brain tissues. We further manipulated DV-induced autophagy by the inducer rapamycin and the inhibitor 3-methyladenine (3MA), which accordingly promoted or suppressed the disease symptoms and virus load in the brain of the infected mice.We demonstrated that DV2 infection of the suckling mice induces autophagy, which plays a promoting role in DV replication and pathogenesis.

Highlights

We and others have reported that autophagy is induced by dengue viruses (DVs) in various cell lines, and that it plays a supportive role in DV replication
The disease symptoms progressed from mild sickness at days 2 and 3 to severe paralysis and mortally ill at day 5 p.i., and mice started to die in the DV2-infected group, whereas no deaths were noted in the mock- and inactive DV2 (iDV2)-treated groups at day 6 p.i. (Figure 1B)
To verify that the abovementioned disease symptoms were caused by dengue virus infection, NS1 protein, an indicator of DV infection, was detected by anti-NS1 antibody in the brain tissues, including the cerebrum, medulla and midbrain of the infected mice, but no NS1 antigen was seen in the cerebellum and pons (Figure 1D, arrow)

Summary

Introduction

We and others have reported that autophagy is induced by dengue viruses (DVs) in various cell lines, and that it plays a supportive role in DV replication. This study intended to clarify whether DV infection could induce autophagy in vivo. The effect of DV induced autophagy on viral replication and DV-related pathogenesis was investigated. Autophagy is characterized by a double-membrane vesicle known as an autophagosome, which recruits cytoplasmic materials and fuses with lysosome for protein degradation [2]. Tian et al, reported that autophagy was detected in brain sections of a GFP-LC3 transgenic mouse model after transient cerebral ischemia and demonstrated a relationship between autophagy and apoptosis [4,5]. Dengue virus infection induces apoptosis in various cell lines and clinical patient specimens [6]. Dengue virus-induced apoptosis and its relationship with autophagy remain to be determined

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