Comparing the Infectivity of Recent SARS-CoV-2 Omicron Sub-Variants in Syrian Hamsters

Since the emergence of the first omicron SARS-CoV-2 variant at the end of 2021, several sub-variants have evolved and become predominant in the human population, showing enhanced transmissibility and ability to (partly) escape the adaptive immune response. The XBB sub-variants (e.g., EG.5.1) have become globally dominant. Besides the XBB sub-variants, a phylogenetically distinct variant, i.e., BA.2.86, is also circulating; it carries several mutations in the spike protein as compared to its parental BA.2 variant. Here, we explored the infectivity of the BA.2.86 and EG.5.1 sub-variants compared to the preceding BA.5 sub-variant in Syrian hamsters. Such preclinical models are important for the evaluation of updated vaccine candidates and novel therapeutic modalities. Following intranasal infection with either variant, throat swabs and lung samples were collected on days 3 and 4 post infection. No significant differences in viral RNA loads in throat swabs were observed between these sub-variants. However, the infectious virus titers in the lungs of EG.5.1- and BA.2.86-infected animals were significantly lower compared to the BA.5-infected ones. The lung pathology scores of animals infected with EG.5.1 and BA.2.86 were also markedly lower than that of BA.5 sub-variant. Together, we show that EG.5.1 and BA.2.86 sub-variants exhibit an attenuated replication in hamsters' lungs as compared to the BA.5 sub-variant.