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Updated: Sep 30, 2025
Live Imaging and Quantification of Viral Infection in K18 hACE2 Transgenic Mice Using Reporter-Expressing Recombinant SARS-CoV-2
Published on: November 5, 2021
Real-Time Visualization of the Infection and Replication of a Mouse-Lethal Recombinant H9N2 Avian Influenza Virus
Guangjie Lao1,2, Kaixiong Ma1,2, Ziwen Qiu1,2
1National Avian Influenza Para-Reference Laboratory (Guangzhou), South China Agricultural University, Guangzhou, China.
Abstract:
H9N2 avian influenza viruses (AIVs) continuously cross the species barrier to infect mammalians and are repeatedly transmitted to humans, posing a significant threat to public health. Importantly, some H9N2 AIVs were found to cause lethal infection in mice, but little is known about the viral infection dynamics in vivo. To analyze the real-time infection dynamics, we described the generation of a mouse-lethal recombinant H9N2 AIV, an influenza reporter virus (VK627-NanoLuc virus) carrying a NanoLuc gene in the non-structural (NS) segment, which was available for in vivo imaging. Although attenuated for replication in MDCK cells, VK627-NanoLuc virus showed similar pathogenicity and replicative capacity in mice to its parental virus. Bioluminescent imaging of the VK627-NanoLuc virus permitted successive observations of viral infection and replication in infected mice, even following the viral clearance of a sublethal infection. Moreover, VK627-NanoLuc virus was severely restricted by the K627E mutation in PB2, as infected mice showed little weight loss and a low level of bioluminescence. In summary, we have preliminarily established a visualized tool that enables real-time observation of the infection and replication dynamics of H9N2 AIV in mice, which contributes to further understanding the mechanisms underlying the pathogenic enhancement of H9N2 AIV to mice.
Insights
Researchers developed a novel reporter virus to visualize H9N2 avian influenza virus (AIV) infection dynamics in real-time within mice. This tool aids in understanding how AIV causes severe illness in mammals.
Area of Science:
- Virology
- Infectious Diseases
- Public Health
Background:
- H9N2 avian influenza viruses (AIVs) pose a significant public health threat due to interspecies transmission to mammals and humans.
- While some H9N2 AIV strains are lethal in mice, their in vivo infection dynamics remain poorly understood.
Purpose of the Study:
- To develop a reporter virus for real-time in vivo imaging of H9N2 AIV infection dynamics.
- To investigate the role of the K627E mutation in the PB2 gene on H9N2 AIV pathogenicity in mice.
Main Methods:
- Generation of a recombinant H9N2 AIV reporter virus (VK627-NanoLuc) incorporating a NanoLuc gene in the NS segment for bioluminescence imaging.
- Assessment of viral pathogenicity and replication in mice compared to the parental virus.
- In vivo bioluminescent imaging to track viral infection, replication, and clearance.
Main Results:
- The VK627-NanoLuc virus exhibited similar pathogenicity and replication in mice as the parental H9N2 AIV, despite being attenuated in cell culture.
- Bioluminescent imaging successfully monitored viral infection, replication, and clearance in real-time in infected mice.
- The K627E mutation in PB2 significantly restricted viral replication, leading to reduced weight loss and lower bioluminescence signals in infected mice.
Conclusions:
- A visualized tool for real-time observation of H9N2 AIV infection and replication in mice has been established.
- This reporter virus system facilitates a deeper understanding of the mechanisms driving H9N2 AIV pathogenicity in mammalian models.
- The findings highlight the critical role of the PB2 K627E mutation in modulating H9N2 AIV virulence.
