Doctor of Philosophy / Department of Biology / Rollie J. Clem / Each year, over 500 million people are infected with mosquito-borne diseases, including
malaria, yellow fever and dengue fever, which cause several million deaths, and long-term
disability and suffering. This dissertation focused on the mosquito Aedes aegypti, a vector for
dengue virus and yellow fever virus. Since Sindbis virus (SINV) is an arthropod-borne virus
(arbovirus) that is vectored by A. aegypti and is well characterized at the molecular level, the SINV
- A. aegypti model was used to determine whether apoptosis plays a role in the control of vector
competency.
In Chapter 2, the effects of inducing or inhibiting apoptosis on SINV replication were
tested in mosquito cells. It was observed that recombinant SINVs expressing pro-apoptotic genes
caused extensive apoptosis in mosquito cells, with decreased virus production after the cells
underwent apoptosis. Infection of mosquito cells with SINV expressing the caspase inhibitor P35
inhibited actinomycin D-induced apoptosis, but had no observable effects on virus replication.
This study was the first to test directly whether inducing or inhibiting apoptosis affects arbovirus
replication in mosquito cells.
Chapter 3 examined the effects of silencing apoptosis regulatory genes on SINV replication
and dissemination in A. aegypti. Genes which either positively or negatively regulate apoptosis
were silenced by RNA interference in mosquitoes, which were then infected with a recombinant
SINV expressing green fluorescent protein (GFP). Reciprocal effects were observed on both the
occurrence and intensity of expression of GFP in various tissues. These results suggest that systemic apoptosis positively influences SINV replication in A. aegypti. This was the first direct
study to explore the role of apoptosis in determining mosquito vector competence for arboviruses.
Finally, in Chapter 4, the mechanisms of apoptosis were explored in A. aegypti.
Overexpression of IAP antagonists caused extensive cell death in mosquito cells, while silencing
the expression of IAP antagonists attenuated apoptosis. The results showed that the IAP binding
motif (IBM) of IAP antagonists was critical for their binding to AeIAP1. The IAP antagonists
released initiator and effector caspases from AeIAP1 by competing for the binding sites and
caused caspase-dependent apoptosis. These findings imply that the mechanisms of IAP
antagonists regulating apoptosis are conserved between mosquitoes and the model insect where
apoptosis has been mainly studied, Drosophila melanogaster.
| Identifer | oai:union.ndltd.org:KSU/oai:krex.k-state.edu:2097/11976 |
| Date | January 1900 |
| Creators | Wang, Hua |
| Publisher | Kansas State University |
| Source Sets | K-State Research Exchange |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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