Two Nature papers in the same period: The replication and pathogenic ability of Omicron mutants are reduced

Source | Nature editor | Wang Duoyu typesetting | Shui Chengwen On January 22, 2022, Nature published two Omicron-related research papers at the same time, both of which showed that Omicron was preclinical Infectious and pathogenic capacity has decreased in rodent models
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The first paper is from the University of Hong Kong, China, and the corresponding authors are Zhu Xuan and Yuan Guoyong
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The paper is titled: Attenuated replication and pathogenicity of SARS-CoV-2 B.
1.
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529 Omicron.
The research team studied the replication efficiency and pathogenicity of Omicron in a series of cell and mouse models
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In laboratory experiments on human lung and intestinal epithelial cells, the authors found that the replication capacity of live Ormicon virus was compared with the new coronavirus wild-type and Alpha, Beta and Delta changes.
body decreased
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In human lung epithelial cells, Omicron replicates more than three times less efficiently than wild-type
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The opposite is true for alpha, beta, and delta, with these variants all having similar or higher replication efficiencies than wild type
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 Further investigation revealed that Omicron was unable to efficiently utilize a protein on the cell membrane called "transmembrane serine protease 2" (TMPRSS2), which mediates viral entry in certain cells
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The authors suggest that mutations in the Omicron spike protein may reduce its ability to utilize the TMPRSS2 pathway, thereby impairing its entry and replication in human epithelial cell lines
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 In a mouse model, Omicron has reduced replication levels in both the upper and lower airways compared to wild-type and delta
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Analysis of lung tissue showed that infection with Omicron caused less inflammation and damage in the lungs than wild-type and delta, which was associated with less weight loss and better survival of the animals
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The second paper is from the University of Wisconsin-Madison, the University of Washington School of Medicine, the University of Tokyo and other units.
The paper is titled: SARS-CoV-2 Omicron virus causes attenuated disease in mice and hamsters.
As a cooperative network for the "New Coronavirus Evolution Assessment" project As part of the study, researchers from multiple independent labs evaluated Omicron's ability to cause infection and disease in mice and hamsters
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In separate experiments, the authors vaccinated mice of different strains with isolates of Omicron and observed that the mice did not lose weight -- very different from previous infections with other variants
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When comparing virus levels in the mouse respiratory tract, the researchers found that the amount of viral RNA and infectious virus in Omicron decreased compared to the beta variant
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For example, in a series of experiments, the viral load in the nasal cavity and lungs of mice infected with Omicron was 10-100 times lower than that of beta infection, and the detection time was 3 days after infection
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 In experiments with Syrian hamsters and transgenic hamsters expressing the human ACE2 receptor, infection with Omicron also did not lead to weight loss
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Pulmonary infections, clinical disease, and pathological changes caused by Omicron are also milder than those of previous variants, including Delta
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The authors note that experiments are currently underway to determine the mechanisms that lead to reduced levels of infection in rodent models, and how this correlates with omicron infection in humans
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Paper link: https:// https:// Open for reprinting.
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