MPXV Clade IIb virus infection in mice leads to prolonged viral replication, macrophage infiltration, and decreased spermatogenesis in the testes.

Mpox (formerly monkeypox) is caused by monkeypox virus (MPXV) and has prompted two recent global health emergencies. Clade IIb MPXV, a recently recognized subclade, has been associated with oral and genital lesions and transmission among men who have sex with men (MSM); however, mechanisms of genital pathogenesis and sexual transmission are not understood. We investigated several routes of MPXV Clade IIb virus infection (intranasal, oral, anal, and intraperitoneal) and found high and prolonged viral titres in the testes after IP inoculation still detectable at 21 days. The testes had significant changes to tissue architecture including loss of spermatogenesis, disorganization of spermatozoa, loss of Leydig cells, and breakdown of the seminiferous tubule membranes. Viral antigen positive cells were present in the interstitial spaces between the seminiferous tubules with macrophage infiltration also evident. This work provides insights into potential of sexual transmission for MPXV viruses as well as mechanisms of Mpox disease which may significantly impact long-term fertility or sex organ health of infected males. Author SummaryMpox (formerly monkeypox) is a painful disease similar to smallpox caused by the monkeypox virus (MPXV) which is an emerging/re-emerging virus. Recently the WHO has declared two global health emergencies due to human-to-human transmission of MPXV. Clade IIb MPXV is a newly recognized subclade that has been associated with genital lesions and sexual transmission/contact; however, how the virus causes disease in sex-organs or how it is passed from person-to-person is not understood. We investigated several routes of MPXV Clade IIb inoculation and found IP inoculation in male mice led to high and prolonged viral titres in testes. Additionally, the testes were significantly affected having loss of sperm and cellular organization. Evidence of inflammatory cell infiltration, specifically, macrophages, are suspected to be the cause of testes specific disease. This work provides insights into potential of sexual transmission for MPXV viruses as well as mechanisms of Mpox disease.