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Host susceptibilities and entry processes of SARS-CoV-2 Omicron variants using pseudotyped viruses carrying spike

Alexandria Zabiegala1, Yunjeong Kim1, Kyeong-Ok Chang2

  • 1Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, 1800 Denison Avenue, Manhattan, KS, 66506, USA.

BMC Veterinary Research
|May 28, 2025
PubMed

Insights

SARS-CoV-2 Omicron variants efficiently infect human and animal cells, with some variants showing enhanced entry compared to the parental strain. Omicron variants rely less on endosomal pathways for cell entry than the original SARS-CoV-2.

Area of Science:

  • Virology
  • Zoonotic Diseases
  • Molecular Biology

Background:

  • Zoonotic potential of SARS-CoV-2 and earlier variants is known, but data for Omicron variants and SARS-CoV is limited.
  • Understanding viral entry mechanisms is crucial for assessing transmission and developing countermeasures.

Purpose of the Study:

  • To evaluate the zoonotic potential of SARS-CoV-2 Omicron variants (BA.1.1, BA.4/5, XBB.1, JN.1) and SARS-CoV.
  • To compare the entry efficiency of these variants into human and animal cells (dogs, cats, white-tailed deer).
  • To investigate the role of host proteases (TMPRSS2, cathepsins) in viral entry.

Main Methods:

  • Generation of lentivirus-based pseudoviruses displaying spike proteins from SARS-CoV-2 parental and Omicron variants, MERS-CoV, and SARS-CoV.
  • Assessment of pseudovirus entry into cells expressing human or animal ACE2 receptors.
  • Western blotting for protease processing, entry/inhibition assays, and fusion assays.
  • Evaluation of cathepsin inhibitor efficacy on viral entry.

Main Results:

  • SARS-CoV-2 Omicron variants efficiently entered human and animal ACE2-expressing cells, with BA.4/5 and XBB.1 showing enhanced entry compared to the parental strain.
  • SARS-CoV pseudoviruses also efficiently entered human and animal cells.
  • TMPRSS2 significantly enhanced entry for all tested pseudoviruses, particularly Omicron variants BA.1.1, JN.1, and XBB.1.
  • Cathepsin inhibitors were less effective against Omicron variants than the parental strain, indicating reduced reliance on the endosomal entry pathway.

Conclusions:

  • SARS-CoV-2 Omicron variants possess significant zoonotic potential, efficiently utilizing ACE2 receptors in various animal species.
  • Omicron variants exhibit altered cell entry mechanisms, relying more on TMPRSS2 and less on endosomal cathepsin pathways compared to the parental SARS-CoV-2 strain.
  • These findings highlight the evolving nature of SARS-CoV-2 and underscore the need for continued surveillance of emerging variants and their zoonotic capabilities.
Keywords:
ACE2CoronavirusPseudovirus assaySARS-CoVSARS-CoV-2SpikeTMPRSS2

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