Omicron subvariant BA.5 more virulent, study on mice revealed, Health News, ET HealthWorld

New Delhi: Scientists have used engineered mice to compare SARS-COV-2 Omicron subvariants and found that the BA.5 strain was more infectious due to its ability to replicate rapidly during infection.

The research, published in the journal Science Advances, addresses the challenge of studying and understanding rapidly evolving variants of concern due to the lack of animal models to run tests that can help explain why variants and subvariants are affecting each person. Why do we behave differently?

The genetically modified mice called K18-hACE2 used in the research express a human receptor that allows SARS-COV-2 to enter otherwise inaccessible mouse cells.

Professor Avery August of the College of Veterinary Medicine (CVM) at Cornell University in the US said: “One of the things we found is that the strain that causes more morbidity, BA.5, grows very rapidly during infection. Repeats.” ,

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“By doing this, the virus actually generates a stronger immune response, which then leads to increased morbidity and symptoms compared to subvariants that don’t replicate as rapidly,” August said.

The researchers said that before this study, there were no small animal models to study the new SARS-CoV-2 Omicron variant of concern, because no animals had become sick from other variants.

Hector Aguilar-Carreño said, “Our study allows us to use relatively old K18-hACE2 mice as a disease model to understand how the virus becomes pathogenic, and to test whether vaccines and “How antivirals work for the new Omicron sub-variant.” Professor of Virology at CVM.

The early Omicron BA.1 and BA.2 subvariants also replicated and spread in K-18 mice, but they caused minimal disease and death.

On the other hand, BA.5-infected mice displayed significant weight loss, higher pathology in the lungs, inflammatory cells and higher levels of cytokines, signaling proteins that are associated with inflammation.

While some 3-month-old mice survived, all 5- to 8-month-old BA.5-infected mice died.

The animal models make it possible for researchers to begin to isolate components of the immune system that can be focused on or blocked to potentially reduce or eliminate the disease, the researchers said.

Some scientists believe that targeting cytokines with drugs could provide a potential treatment that controls the immune response and reduces symptoms, he said.

The researchers found several similarities between how these subvariants behave in mouse models and humans, with BA.5 being more virulent in both. One major difference was that most people who developed disease from BA.5 did not die, but in K-18 mice, the subvariant was particularly pathogenic and lethal.

One advantage of mouse models is that all mice are identical, with the same genetic background. When studying humans, many variables – such as previous conditions, genetics and whether someone has been previously immunized or infected – can influence the pathological outcome of the disease.

Additionally, the mouse model allowed researchers to examine disease in the lungs over time.

“With BA.5, we see more pathology during infection than mice infected with other strains or control mice,” August said.

The team also found a higher viral load in the strain that caused more infections. Old mice were also more affected by this virus than young mice.

  • Published on September 27, 2023 at 11:25 am IST

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