Abstract
Many vertebrate and insect viruses possess antiapoptotic genes that are required for their infectivity. This led to the hypothesis that apoptosis is an innate immunoresponse important for limiting virus infections. The role of apoptosis may be especially important in insect antiviral defense because of the lack of adaptive immunity. However, the cellular mechanism that elicits apoptosis in response to viral infection in insects has not been determined. Using an in vivo infection system with the mosquito baculovirus CuniNPV (Culex nigripalpus nucleopolyhedrovirus), we demonstrated that michelob_x (mx), the mosquito ortholog of Drosophila proapoptotic gene reaper, is specifically induced in larval midgut cells following viral infection. Interestingly, the dynamics of mx induction corresponds with the outcome of the infection. In the permissive mosquito C. quinquefasciatus, a slow induction of mx failed to induce prompt apoptosis, and the infected cells eventually undergo necrosis with heavy loads of encapsulated viruses. In contrast, in the refractory mosquito Aedes aegypti, a rapid induction of mx within 30 min p.i. is followed by apoptosis within 2–6 h p.i., suggesting a possible role for apoptosis in limiting viral infection. When the execution of apoptosis was delayed by caspase inhibitors, viral gene expression became detectable in the A. aegypti larvae.
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Abbreviations
- mx :
-
michelob_x
- IAP:
-
inhibitor of apoptosis
- β-gal:
-
β-galactosidase
- IBM:
-
IAP-binding motif
- CuniNPV :
-
Culex nigripalpus nucleopolyhedrovirus
- AcMNPV :
-
Autographa californica multicapsid nucleopolyhedrovirus
- OB:
-
occlusion body
- Q-PCR:
-
quantitative real-time PCR
- FISH:
-
fluorescent in situ hybridization
- TUNEL:
-
terminal deoxynucleotidyl transferase dUTP nick end labeling
- PI:
-
propidium iodide
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Acknowledgements
This work was supported by NIH Grants R21AI067555 and R56AI079074. We are very grateful for the insightful comments provided by Dr. Rollie Clem on this manuscript and for the excellent technical support provided by Neil Sanscrainte and Kelly Anderson at USDA/CMAVE at Gainesville, FL, USA.
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Liu, B., Becnel, J., Zhang, Y. et al. Induction of reaper ortholog mx in mosquito midgut cells following baculovirus infection. Cell Death Differ 18, 1337–1345 (2011). https://doi.org/10.1038/cdd.2011.8
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DOI: https://doi.org/10.1038/cdd.2011.8
