Comparative infection and pathogenesis of SARS-CoV-2 Omicron and Delta variants in aged and young Syrian hamsters

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Abstract

Coronavirus disease 2019 continues to batter the world with the unceasing introduction of new variants of the causative virus, SARS-CoV-2. In order to understand differences in disease caused by variants of concern and to develop variant-specific vaccines, suitable small animal models are required that mimic disease progression in humans at various stages of life. In this study, we compared the dynamics of infection with two SARS-CoV-2 variants of concern (Delta and Omicron) in aged (>1 year 3 months old) and young (<5 weeks old) Syrian hamsters ( Mesocricetus auratus ). We show that no weight loss occurred in Omicron infected groups regardless of age, while infection with the Delta variant caused weight loss of up to 10% by day 7 post-infection with slower and incomplete recovery in the aged group. Omicron replicated to similar levels as Delta in the lungs, trachea and nasal turbinates, with no significant differences in the tissue viral loads of aged versus young animals for either variant. In contrast to rare necrosis observed in Omicron-infected animals regardless of age, severe necrosis was observed in the olfactory epithelium in Delta-infected animals. Omicron infection also resulted in mild pulmonary disease in both young and aged animals compared to the moderate acute necrotizing bronchointerstitial pneumonia seen in Delta-infected animals. These results suggest that Omicron infection results in an attenuated clinical disease outlook in Syrian hamsters compared to infection with the Delta variant irrespective of age.

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  1. SciScore for 10.1101/2022.03.02.482662: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsIACUC: Approval for this study was obtained from the Boston University Institutional Biosafety Committee (IBC) and Institutional Animal Care and Use Committee (
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    BlindingSlides were examined blinded by a board-certified veterinary pathologist (N.A.C.), with subsequent unblinding conducted to generate pathology results.
    Power Analysisnot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Experimental Models: Cell Lines
    SentencesResources
    The dilutions were then plated onto Vero E6 cells seeded at 8 × 105 cells per well (NR-596, BEI Resources).
    Vero E6
    suggested: None
    Software and Algorithms
    SentencesResources
    The half …