Key features of SARS-CoV-2 infection

New research is developing a vital animal model of SARS-CoV-2 to identify the main characteristics of an infection.

Developing effective therapies to treat COVID-19 is a problem of immense global concern. However, one of the most important steps in developing a novel therapeutic is developing a reliable animal model that can be used to test the effectiveness of the treatment prior to testing in humans. Because SARS-CoV-2 is a new virus that has only been identified in the last 12 months, there is currently no reliable animal model for the main characteristics of SARS-CoV-2 infection. The lack of an animal model is a problem that could hamper efforts to develop new therapies for COVID-19. A new study published in the Journal of Infectious Diseases attempts to address this problem (1).

The researchers are using non-human primates, particularly macaques, to develop a reliable animal model for future drug testing. The study included 16 macaques. The animals were specifically selected to include two different subspecies, both male and female macaques, and to cover an age range. All animals were infected with SARS-CoV-2 in a variety of ways, including directly into the bloodstream, into the eyes, via the nose and mouth, and directly into the trachea.

After infection, disease progression was observed in the animals. Smears were collected and tested at different sites at different times after infection. The animals were monitored using a variety of measures such as activity levels, body weight, respiratory rate, and body temperature. Although no changes in respiratory rate or weight were observed, 13 of the 16 macaques showed an increase in body temperature.

The lung tissue of these animals was examined three days after infection. Crucially, these tissue samples showed evidence of interstitial pneumonia and endothelitis (inflammation in the blood vessels). This is important as it reflects the observed impact of COVID-19 on human lung tissue.

Another interesting finding was the decrease in total lymphocytes (especially CD4 + and CD8 + T cells) observed in macaques. This is similar to the loss of lymphocytes (which are critical to the immune response) seen in 83.2% of human patients hospitalized with COVID-19, which is another key characteristic of SARS-CoV-2 infection.

Overall, the results of this study suggest that both of the macaque subspecies examined are susceptible to infection with the SARS-CoV-2 strains that are currently infecting humans. The virus's impact on these animals is similar to what has been observed in the human lungs. This suggests that macaques could be a suitable animal model to reliably predict both disease progression and the potential effects of a new treatment. In addition, the influence of the virus on the animals' immune systems suggests that they are also a useful model for studying the interaction between the virus and the host's immune system.

The results of this study are promising, but not a short-term solution to the current crisis. Despite the recent promising news in the field of vaccination, there will remain a significant need for effective therapies to treat COVID-19. Developing a reliable animal model is an important foundation on which future drug development research can build.

Written by Michael McCarthy

1. Koo B-S, Oh H., Kim G., Hwang E. H., Jung H., Lee Y. et al. Transient lymphopenia and interstitial pneumonia with endotheliitis in SARS-CoV-2 infected macaques. The Journal of Infectious Diseases. 2020; 222 (10): 1596-1. 600.

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