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. 2022 Feb:198:105253.
doi: 10.1016/j.antiviral.2022.105253. Epub 2022 Jan 21.

The omicron (B.1.1.529) SARS-CoV-2 variant of concern does not readily infect Syrian hamsters

Rana Abdelnabi  1 , Caroline S Foo  1 , Xin Zhang  1 , Viktor Lemmens  2 , Piet Maes  3 , Bram Slechten  4 , Joren Raymenants  5 , Emmanuel André  6 , Birgit Weynand  7 , Kai Dallmeier  8 , Johan Neyts  9
Affiliations

The omicron (B.1.1.529) SARS-CoV-2 variant of concern does not readily infect Syrian hamsters

Rana Abdelnabi et al. Antiviral Res. 2022 Feb.

Abstract

The emergence of SARS-CoV-2 variants of concern (VoCs) has exacerbated the COVID-19 pandemic. End of November 2021, a new SARS-CoV-2 variant namely the omicron (B.1.1.529) emerged. Since this omicron variant is heavily mutated in the spike protein, WHO classified this variant as the 5th variant of concern (VoC). We previously demonstrated that the ancestral strain and the other SARS-CoV-2 VoCs replicate efficiently in and cause a COVID19-like pathology in Syrian hamsters. We here wanted to explore the infectivity of the omicron variant in comparison to the ancestral D614G strain in the hamster model. Strikingly, in hamsters that had been infected with the omicron variant, a 3 log10 lower viral RNA load was detected in the lungs as compared to animals infected with D614G and no infectious virus was detectable in this organ. Moreover, histopathological examination of the lungs from omicron-infected hamsters revealed no signs of peri-bronchial inflammation or bronchopneumonia.

Keywords: COVID-19; Hamsters; Infectivity; Omicron; SARS-CoV-2 VoC.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Characterization of the in vivo replication of the omicron SARS-CoV-2 variant versus the ancestral D614G strain. (a) Set-up of the Syrian hamster infection study. (b) Viral RNA levels in the lungs of hamsters infected with 103 TCID50 of BavPat (D614G) strain (n = 6) or the omicron (B.1.1.529) SARS-CoV-2 variant (n = 6) on day 4 post-infection (pi) are expressed as log10 SARS-CoV-2 RNA copies per mg lung tissue. Individual data and median values are presented. (c) Infectious viral loads in the lungs of hamsters infected with the D614G strain or the omicron variant at day 4 pi are expressed as log10 TCID50 per mg lung tissue. Individual data and median values are presented. (d) Weight change at day 4 pi in percentage, normalized to the body weight at the time of infection. Bars represent means ± SD. Data were analyzed with the Mann−Whitney U test, **P < 0.01. All data are from a single experiment.
Fig. 2
Fig. 2
Histopathology of lungs of Syrian hamsters infected with either the D614G strain or the omicron SARS-CoV-2 variant. (a) Representative H&E images of lungs of hamsters infected with 103 TCID50 of BavPat (D614G) strain (n = 6) or the omicron (B.1.1.529) SARS-CoV-2 variant at day 4 post-infection (pi). The lungs of hamsters infected with the ancestral D614G strain (left picture) show significant bronchopneumonia (green arrows), perivascular inflammation with peri-vascular oedema (red arrows) and peri-bronchial inflammation (blue arrows), whereas the lungs of the omicron-infected hamsters (Right picture) appear normal with no peri-bronchial inflammation (blue arrows) or bronchopneumonia. Scale bars, 100 μm. (b) Cumulative severity score from H&E stained slides of lungs from hamsters infected with the D614G strain or the omicron variant at day 4 pi. Individual data and median values are presented and the dotted line represents the median score of untreated non-infected hamsters. Data were analyzed with the Mann−Whitney U test, **P < 0.01. All data are from a single experiment.
See this image and copyright information in PMC

References

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