Discussion
Automated activity monitoring of laboratory animals may provide an
objective measure to follow disease progression following infection with
respiratory viruses. Here we tested a system using RFID transponders to
follow the activity of individual mice challenged with mouse-adapted
Influenza A/PR8 virus. We noted a decline in activity, which correlated
with weight loss. In contrast, vaccination prevented this decline in
activity. A similar decline in activity was observed in previous studies
using computerized home cage monitoring (HCM) to measure average group
activity of mice in the context of SARS-CoV-2 and influenza virus
infection5,6.
Automated activity monitoring presents a number of advantages over more
subjective symptom scoring, which is typically performed by animal
research technicians. By following the mice in their familiar
environment and minimizing animal-human interactions, automated activity
monitoring may cause less stress to the animals and has the potential to
improve the data quality by offering an objective assessment.
Furthermore, automated monitoring, could give less data variation, which
may allow for reductions in the number of animals used to test the
protective efficacy of vaccines7. Notably, using
automated monitoring of activity, we found that reduced activity
preceded weight loss. An advantage of the RFID transponder system used
in our studies is the ability to monitor mice at an individual level.
Activity monitoring may therefore be used to inform animal caretakers to
follow specific animals more closely and could potentially serve as
endpoint in murine challenge studies. As an objective measure of animal
health status, activity monitoring could thus be used to improve animal
welfare by alerting animal caretakers upon a sudden decline in activity.
In summary, the use of automated activity monitors could present
significant advantages for data accuracy and animal welfare and is
increasingly used in preclinical research8-10. By
providing continuous and objective monitoring, automated activity
monitors may also be implemented for respiratory virus challenge models
and vaccine testing. Here we tested their use in influenza vaccine
studies and demonstrate that mice immunized with HA protein formulated
in CAF01 retained their activity following challenge. The data
demonstrate the promise of using automated activity monitors for
challenge studies with influenza and possibly other respiratory viruses.