Differential susceptibility of immunodeficient mice to MPXV infection and the impact of various inoculation routes

Monkeypox virus (MPXV), a member of the Orthopoxvirus genus, caused a large-scale global outbreak in 2022. Developing mouse models for MPXV infection is crucial for advancing research on vaccines and therapeutic interventions. To address this, we conducted a comparative study on the susceptibility of six mouse strains-severe combined immune-deficiency (SCID), nude, genetically diabetic (db/db) and obese (ob/ob), C57BL/6J, and BALB/c-to MPXV infection. Mouse strains were infected with MPXV via intranasal inoculation, and body weight changes and mortality were monitored post-infection. Additionally, the tissue distribution of MPXV and the pathological changes in the lung tissues of the infected mice were evaluated. The results demonstrated that SCID and nude mice exhibited significant weight loss following MPXV infection, with 100 ​% mortality observed in SCID mice, while no mortality occurred in nude mice. In contrast, the other mouse strains showed no significant weight loss or mortality. Notably, the viral load in the lung tissues of SCID and nude mice was the highest among the tested strains. Furthermore, we investigated the impact of different inoculation routes-intranasal (I.N.), intraperitoneal (I.P.), and intravenous (I.V.)-on the pathogenicity of MPXV in mice. The results revealed that the intravenous route induced more pronounced pathogenic effects compared to the intranasal and intraperitoneal routes. In summary, this study provides valuable insights into the development of MPXV-infected mouse models, offering a foundation for further research on MPXV pathogenesis and therapeutic drug development.