The central goal of this project is to examine the antiviral mechanisms in mosquitoes. As a first step, in this R21 proposal we will explore the antiviral system in the mosquito cells, Aag2. Mosquito transmission of arboviruses causes widespread and debilitating disease across the globe. Viral replication and dissemination in the mosquito are critical factors in transmission competence. RNA interference inhibits viral replication and virus-derived small RNAs accumulate during infection. Interestingly, while piRNAs are generally associated with germline defense against mobile genetic elements, in mosquitoes, virus genome-derived piRNAs (v-piRNAs) are produced during infection in somatic tissues. We discovered that Piwi4 is a viral restriction factor, and demonstrated that the piRNA pathway mediates antiviral immunity in cell culture and in mosquitoes. Furthermore, production of mature v-piRNAs requires Piwi4 and, strikingly, also depends on viral cDNA, which is synthesized by endogenous reverse transcriptases. These viral derived cDNAs are incorporated into the genome in the form of endogenous viral elements (EVEs), which are transmitted to the progeny. These results indicate that mosquitoes have evolved CRISPR-like, trans-generational adaptive antiviral immunity through the acquisition of EVEs that serve as templates for biogenesis of small antiviral RNAs. We propose to examine the role of piRNAs in mosquito antiviral immunity and to study their biological significance, mechanisms, and how ZIKV modulate piRNA immunity. Our experiments will examine the relation between ZIKV and the mosquito immune system. Specifically, we will: (1) antiviral function in the Ae. Aegypti-derived Aag2 cell and (2) identify and study ZIKV encoded piRNA suppressors.

Public Health Relevance

Zika is an emerging viral infection caused by a mosquito-transmitted flavivirus that is rapidly spreading throughout the Americas and causing severe morbidity, particularly in newborn babies. A number of Zika cases have been imported to the US. We propose to examine the interaction of ZIKV with the mosquito immune system to better understand how the mosquito vector facilitates virus spread.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21AI129863-01
Application #
9278405
Study Section
Special Emphasis Panel (ZAI1)
Program Officer
Challberg, Mark D
Project Start
2017-09-01
Project End
2019-08-31
Budget Start
2017-09-01
Budget End
2018-08-31
Support Year
1
Fiscal Year
2017
Total Cost
Indirect Cost
Name
University of California San Francisco
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
094878337
City
San Francisco
State
CA
Country
United States
Zip Code
94118