Shillong, September 26: A recent study has revealed that the Omicron sub-variant BA.5 exhibits greater virulence due to its ability to replicate rapidly early during infection.
As per IANS, researchers at Cornell University in the US conducted the study using genetically modified mice, called K18-hACE2 mice, which express a human receptor that allows the SARS-CoV-2 virus, including its sub-variants, to enter mouse cells that would otherwise be inaccessible.
Avery August, a Professor of microbiology and immunology, stated, “One of the things we found is that the strain that causes more pathology, BA.5, replicates much faster early on during infection. By doing that, the virus generates a really strong immune response, which then leads to increased pathology and symptoms compared to sub-variants that don’t replicate as fast.”
The research, published in the journal Science Advances, also found that early Omicron BA.1 and BA.2 sub-variants replicated and spread in the K-18 mice but caused minimal illness and death. In contrast, BA.5-infected mice experienced significant weight loss, lung pathology, high levels of inflammatory cells, and cytokines associated with inflammation.
While some 3-month old mice survived, all 5 to 8 month-old BA.5-infected mice died. This animal model allows researchers to explore components of the immune system that could be targeted or blocked to potentially mitigate or eliminate the disease.
The study suggested that targeting cytokines with drugs might provide a potential treatment to modulate the immune response and reduce symptoms. The researchers noted that BA.5 displayed similar behavior in both the mouse model and humans, with increased virulence.
However, it’s worth noting that most people who contracted BA.5 did not die, whereas in K-18 mice, the subvariant was notably pathogenic and lethal.
The mouse model offers advantages such as genetic uniformity, which reduces variables that can affect disease outcomes when studying humans, such as previous health conditions, genetics, and vaccination or prior infection history. Additionally, it enables the examination of lung disease progression over time, demonstrating higher pathology and viral loads with BA.5 compared to other strains or control mice, particularly affecting older mice.