Characterization of an EG.5.1 clinical isolate in vitro and in vivo

  1. Ryuta Uraki
  2. Maki Kiso
  3. Kiyoko Iwatsuki-Horimoto
  4. Seiya Yamayoshi
  5. Mutsumi Ito
  6. Shiho Chiba
  7. Yuko Sakai-Tagawa
  8. Masaki Imai
  9. Yukie Kashima
  10. Michiko Koga
  11. Noriko Fuwa
  12. Nobumasa Okumura
  13. Masayuki Hojo
  14. Noriko Iwamoto
  15. Hideaki Kato
  16. Hideaki Nakajima
  17. Norio Ohmagari
  18. Hiroshi Yotsuyanagi
  19. Yutaka Suzuki
  20. Yoshihiro Kawaoka

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Abstract

EG.5.1 is a subvariant of the SARS-CoV-2 Omicron XBB variant that is rapidly increasing in prevalence worldwide. EG.5.1 has additional substitutions in its spike protein (namely, Q52H and F456L) compared with XBB.1.5. However, the pathogenicity, transmissibility, and immune evasion properties of clinical isolates of EG.5.1 are largely unknown.

In this study, we used wild-type Syrian hamsters to investigate the replicative ability, pathogenicity, and transmissibility of a clinical EG.5.1 isolate. Our data show that there are no obvious differences in growth ability and pathogenicity between EG.5.1 and XBB.1.5, and both EG.5.1 and XBB.1.5 are attenuated compared to a Delta variant isolate.

We also found that EG.5.1 is transmitted more efficiently between hamsters compared with XBB.1.5. In addition, unlike XBB.1.5, we detected EG.5.1 virus in the lungs of four of six exposed hamsters, suggesting that the virus tropism of EG.5.1 is different from that of XBB.1.5 after airborne transmission.

Finally, we assessed the neutralizing ability of plasma from convalescent individuals and found that the neutralizing activity against EG.5.1 was slightly, but significantly, lower than that against XBB.1.5 or XBB.1.9.2. This suggests that EG.5.1 effectively evades humoral immunity and that the amino acid differences in the S protein of EG.5.1 compared with that of XBB.1.5 or XBB.1.9.2 (i.e., Q52H, R158G, and F456L) alter the antigenicity of EG.5.1.

Our data suggest that the increased transmissibility and altered antigenicity of EG.5.1 may be driving its increasing prevalence over XBB.1.5 in the human population.

Article activity feed

  1. Rapid Reviews Infectious Diseases

    Nicholas Maness

    Review 1: "Characterization of an EG.5.1 Clinical Isolate In Vitro and In Vivo"

    While suggesting additional comparisons for broader context, the reviewer considered this an important report, emphasizing EG.5's potential for slightly increased transmissibility and immune evasion without increased pathogenicity.

  3. Version published to 10.1101/2023.08.31.555819v1 on bioRxiv