Monitoring Group Activity of Hamsters and Mice as a Novel Tool to Evaluate COVID-19 Progression, Convalescence, and rVSV-ΔG-Spike Vaccination Efficacy.

The COVID-19 pandemic initiated a worldwide race toward the development of treatments and vaccines. Small animal models included the Syrian golden hamster and the K18-hACE2 mice infected with SARS-CoV-2 to display a disease state with some aspects of human COVID-19. A group activity of animals in their home cage continuously monitored by the HCMS100 (Home cage Monitoring System 100) was used as a sensitive marker of disease, successfully detecting morbidity symptoms of SARS-CoV-2 infection in hamsters and in K18-hACE2 mice. COVID-19 convalescent hamsters rechallenged with SARS-CoV-2 exhibited minor reduction in group activity compared to naive hamsters. To evaluate the rVSV-ΔG-spike vaccination efficacy against SARS-CoV-2, we used the HCMS100 to monitor the group activity of hamsters in their home cage. A single-dose rVSV-ΔG-spike vaccination of the immunized group showed a faster recovery than the nonimmunized infected hamsters, substantiating the efficacy of rVSV-ΔG-spike vaccine. HCMS100 offers nonintrusive, hands-free monitoring of a number of home cages of hamsters or mice modeling COVID-19.

Group activity of mice in communal home cage used as an indicator of disease progression and rate of recovery: Effects of LPS and influenza virus.

Large numbers of rodents are often used in the study of disease progression and in the evaluation of its potential treatments. To avoid subjective observation and to minimize home cage interference, we developed a computerized home cage monitoring system (HCMS100) based on a standard cage rack adapted with a single laser beam and a detector mounted on each cage, enabling to monitor mice movements based on laser beam interruptions. This retrofit system provided continuous and uninterrupted monitoring of spontaneous movement of a group of mice in a home cage. Validity was evaluated using disease state induced by LPS modelling bacterial infection and by influenza virus. RESULTS: Spontaneous activity of different number of mice (2-8) per cage showed the expected circadian rhythm with increased activity during the night, and its extent dependent on the number of mice in the cage. Females and males show similar circadian rhythm. Intranasal LPS administration and pulmonary infection with live influenza virus resulted in major reduction of mice activity along disease progression. Increase in activity over time was a good indicator of the recovery process from both LPS exposure and the flu infection. CONCLUSIONS: HCMS100 was shown to be a reliable, inexpensive, easy to use system that requires no changes in the common housing of various experimental animals (mice, hamsters, rats etc.). With minimal intervention, HCMS100 provides a continuous record of group activity with clear pattern of circadian rhythm, allowing long term recording of home cage activity even in restricted access environments.