# Novel antiviral activity of interferon-gamma against viral replication complex

> **NIH NIH R01** · UNIVERSITY OF CHICAGO · 2020 · $405,000

## Abstract

Project Summary/Abstract
Viruses with positive-sense RNA (+RNA) genome compose a large group of plant and animal viruses, and many
human viruses of medical concerns belong to this group of viruses. All known +RNA viruses form and replicate
within vacuole-like structures in the cytoplasm, called replication complex (RC). Viral RC is made by viruses
through reorganization of cellular organelle membranes, and it provides a favorable microenvironment for the
viruses to replicate. Nevertheless, it has been obscure whether and how the host immune system counteracts
such viral RCs. Understanding the host immune defense strategy against viral RC may allow us to develop
broadly applicable antiviral strategies against +RNA viruses. We recently found that interferon-gamma (IFNG)
inhibits the replication of murine norovirus (MNV) at the stage of RC formation. Intriguingly, this antiviral activity
of IFNG depends on a protein complex involved in cellular autophagy. Autophagy is an evolutionarily conserved
pathway that sequesters cytoplasmic materials in double-membrane-bound autophagosomes and delivers them
to the lysosome for degradation. To form a globular autophagosome, the microtubule-associated-protein-1-light-
chain-3 (LC3) conjugation system is essential. We found that only the LC3 conjugation system of autophagy, but
not the lysosomal degradation through autophagy, is required for IFNG to inhibit MNV RC formation.
Interestingly, IFNG also requires the same LC3 conjugation system, but not the lysosomal degradation, to disrupt
a cytosolic vacuole containing a protist parasite Toxoplasma gondii. Through a comparative mechanism study
of MNV and T. gondii models, we found that the LC3 conjugation system was required to recruit IFN-inducible
GTPases, immunity related GTPases (IRGs) and guanylate binding proteins (GBPs), to the RC of MNV. Both
IRGs and GBPs are known to be targeted to the membrane of vacuoles containing bacterium, protist, or fungus.
The targeted membranes are vesiculated and eventually the vacuoles rupture, leading to the death of exposed
pathogens. Similarly, the GTPases were required for IFNG to disrupt MNV RCs and consequently to inhibit the
replication of MNV in both mouse and human systems. This is a novel and paradigm-shifting antiviral mechanism
of IFNG, indicating a common effector mechanism against disparate pathogens replicating in cytosolic
membranous shelters, including +RNA virus as well as bacterium, protist, and fungus. Our long-term goal is to
harness the medical benefits based on the functional mechanism of this antiviral immune defense against viral
RCs. The overall objective of this proposal, as the next step to pursue that goal, is to determine how the RC of
MNV is detected and disrupted by the immune system. Our central hypothesis is that MNV RC is detected by
the LC3 conjugation system of the autophagy pathway and then the structure/function of RC is disrupted by the
IFN-inducible GTPases recruited via the LC3 conjugat...

## Key facts

- **NIH application ID:** 9988363
- **Project number:** 5R01AI127518-04
- **Recipient organization:** UNIVERSITY OF CHICAGO
- **Principal Investigator:** Glenn C Randall
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $405,000
- **Award type:** 5
- **Project period:** 2017-09-02 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9988363

## Citation

> US National Institutes of Health, RePORTER application 9988363, Novel antiviral activity of interferon-gamma against viral replication complex (5R01AI127518-04). Retrieved via AI Analytics 2026-05-29 from https://api.ai-analytics.org/grant/nih/9988363. Licensed CC0.

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