# Flavivirus NS3-mediated Innate Immune Escape

> **NIH NIH R01** · CLEVELAND CLINIC LERNER COM-CWRU · 2020 · $543,349

## Abstract

PROJECT SUMMARY
Flaviviruses that are transmitted by mosquitoes, including dengue (DV) and West Nile (WNV)
viruses as well as the recently emerging Zika virus (ZIKV), represent a significant global health
concern. Despite the high morbidity and mortality resulting from infection by these viral
pathogens, there are currently no FDA-approved therapies. Hence, there is a pressing need to
understand better the pathogenesis of these viruses to aid the design of vaccines and antivirals.
Disease severity and pathogenesis of viral infections in humans depend on many factors,
including pre-existing immunity, strain virulence, host genetics and virus-host interactions.
Among the virus-host interactions that modulate pathogenesis, virus-mediated suppression of
innate immune signaling pathways has a critical role. However, the precise mechanisms by
which flaviviruses evade host innate immunity are not well characterized.
The proposed study builds on a recent discovery by the Gack laboratory that the NS3 protein of
DV interacts with the mitochondrial-targeting trafficking protein 14-3-3ε to block the cytosol-to-
mitochondria translocation of the viral RNA sensor RIG-I, thereby suppressing antiviral signaling
and type I interferon (IFN) induction. We have identified the precise motif in DV NS3 for 14-3-3ε
interaction, a four-amino-acid phosphomimetic 64RxEP67 motif, and also generated a
recombinant mutant DV. This recombinant DV, encoding a 14-3-3ε-binding-deficient mutant
NS3 protein, is growth-attenuated compared to wild-type DV in cells with intact innate host
defense and elicits robust innate immune and T cell responses in vitro. WNV and ZIKV NS3
proteins encode a similar phosphomimetic motif, 64RLDP67, and our preliminary results show
that WNV NS3 also targets 14-3-3ε to block RIG-I-mediated innate immunity.
Using molecular, biochemical and cell biological approaches combined with infection studies
with recombinant NS3 mutant viruses, we will define in precise detail how DV and WNV NS3
inhibits the host IFN response. This study also will yield insight into the mechanism(s) by which
ZIKV NS3 protein modulates IFN-mediated host defense responses (Aim 1). Finally, we will
determine the physiological relevance of the 14-3-3ε-NS3 interaction for viral pathogenesis and
escape from host innate and adaptive immunity using in vitro cell culture systems and mouse
models of WNV infection (Aim 2). Our studies will provide a molecular understanding of the
immune escape mechanisms of DV, WNV and ZIKV, which may guide the rational design of
new vaccines and antivirals.

## Key facts

- **NIH application ID:** 10290686
- **Project number:** 7R01AI127774-06
- **Recipient organization:** CLEVELAND CLINIC LERNER COM-CWRU
- **Principal Investigator:** Michaela Ulrike Gack
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $543,349
- **Award type:** 7
- **Project period:** 2016-09-23 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10290686

## Citation

> US National Institutes of Health, RePORTER application 10290686, Flavivirus NS3-mediated Innate Immune Escape (7R01AI127774-06). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10290686. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*