Comparison of monkeypox viruses pathogenesis in mice by in vivo imaging

Monkeypox viruses (MPXV) cause human monkeypox, a zoonotic smallpox-like disease endemic to Africa, and are of worldwide public health and biodefense concern. Using viruses from the Congo (MPXV-2003-Congo-358) and West African (MPXV-2003-USA-044) clades, we constructed recombinant viruses that express the luciferase gene (MPXV-Congo/Luc+and MPXV-USA-Luc+) and compared their viral infection in mice by biophotonic imaging. BALB/c mice became infected by both MPXV clades, but they recovered and cleared the infection within 10 days post-infection (PI). However, infection in severe combined immune deficient (SCID) BALB/c mice resulted in 100% lethality. Intraperitoneal (IP) injection of both MPXV-Congo and MPXV-Congo/Luc+resulted in a systemic clinical disease and the same mean time-to-death at 9 (??0) days post-infection. Likewise, IP injection of SCID-BALB/c mice with MPXV-USA or the MPXV-USA-Luc+, resulted in similar disease but longer (P