Comparative pathogenicity study of monkeypox virus Clade Ib and Clade IIb in a rabbit model.

Mpox has emerged as a significant public health concern, spreading across continents with the emergence of new variants. Clade IIb, from the recent global outbreak, and the newly identified Clade Ib have shown changes in transmission dynamics and possibly in severity. We developed a New Zealand White rabbit model of Mpox by using a combination of intradermal and intravenous routes of administration. Following infection, the rabbits developed erythematous papular lesions on the skin, which progressed to crust and scab formation by the second week, ultimately leading to healing and seroconversion. Infection with the Clade Ib and IIb.A.2.1 lineages revealed that both Monkeypox virus (MPXV) variants caused skin and testicular lesions, as well as viral excretion from the nasal cavity, skin, and testicular tissue. However, there were no significant differences in disease severity between the two variants. These findings suggest that this rabbit model could be useful for evaluating countermeasures against MPXV.