Dose-dependent pathogenicity and inflammatory imbalance in severely immunodeficient mice infected with mpox virus

Abstract

The global spread of mpox continues to pose a threat to public health, with immunocompromised patients being at greater risk for severe disease. This study aimed to establish a lethal severe infection model using NPG (NOD.Cg-Prkdc^scidIl2rg^tm1/Vst) mice, a strain with profound immunodeficiency, to simulate severe mpox in immunocompromised patients and investigate disease progression, viral replication kinetics, tissue tropism, and immune responses. In our study, mice were inoculated with three doses of mpox virus (high: 2 × 10⁷, medium: 2 × 10⁶, low: 2 × 10⁵ TCID₅₀ [50% tissue culture infective dose]) or phosphate-buffered saline as a negative control. Body weight, clinical signs, and survival were monitored. Viral loads in plasma and tissues, histopathological changes, and inflammatory responses were evaluated to systematically characterize the pathogenicity of mpox virus in severely immunodeficient mice. The results showed that NPG mice were highly susceptible to mpox virus, showing a clear dose-dependent response. The high-dose group exhibited 100% lethality, and the medium-dose group had a 50% survival rate, whereas the low-dose and control groups survived throughout the study. Plasma and tissue viral loads, as well as histopathological severity, followed a dose-dependent pattern. Viremia remained persistently high, and animals that died at different time points exhibited uniformly high viral loads across multiple tissues. By day 10 postinfection, markedly elevated levels of pro-inflammatory cytokines were detected in plasma, whereas anti-inflammatory cytokines remained largely uninduced. We found that the infection of severely immunodeficient mice with mpox virus results in dose-dependent lethality, persistent high viral loads, and a pronounced pro−/anti-inflammatory imbalance. These findings provide important insights into the pathogenesis of mpox in immunocompromised populations and develop a practical animal model for evaluating therapeutic interventions.

Keywords

inflammatory response / lethal model / mpox virus / NPG (NOD.Cg-Prkdc^scidIl2rg^tm1/Vst) mice / viremia

References

[1] Viguier C, Delobel P, Lescure FX, Bessis S, Mansuy JM, Martin-Blondel G. From neglected to notoriety: a review of mpox clinical features, virology, epidemiology, treatment and prevention strategies. Eur J Clin Microbiol Infect Dis. 2025; 44: 2569-2596.

[2] Malla A, Saleh FM. The resurgence of monkeypox virus: a critical global health challenge and the need for vigilant intervention. Front Public Health. 2025; 13:1572100.

[3] Xing L, Li J, Guo Y, Liu Y, Xiao J, Zhao H. Clinical characteristics of six fatal cases with advanced HIV and monkeypox virus co-infection in Beijing: a retrospective analysis. J Infect Public Health. 2026; 19:103126.

[4] Garnier N, Schinazi RF, Titanji BK. Insights into host responses, viral evolution, and implications for vaccines and therapeutics for mpox. Curr Opin HIV AIDS. 2026; 21: 110-117.

[5] Ngongo N, Boum Y 2nd, Mercy K, et al. Still not over: Africa CDC and WHO issue third reaffirmation of mpox emergency. J Public Health Afr. 2025; 16:1556.

[6] Hoffmann Dahl E, Jiba DF, Casas EC, et al. Monkeypox virus-HIV co-infections in Sierra Leone. Lancet Infect Dis. 2025; 25: e623-e624.

[7] Gomes TCO, Pardal JSdO, de Almeida LG, dos Reis e Silva Gomes LdN, Lima ASS. Severe mpox infection in an immunosuppressed patient: case report from a reference hospital in Pará. Braz J Infect Dis. 2026; 30:104818.

[8] Mitjà O, Alemany A, Marks M, et al. Mpox in people with advanced HIV infection: a global case series. Lancet (London, England). 2023; 401: 939-949.

[9] Caria J, Vara-Luiz F, Maia I, et al. Fatal case of progressive mpox in a patient with AIDS-viral enteropathy and malabsorption demanding the use of full parenteral ARV and endovenous cidofovir. Infect Dis Rep. 2023; 15: 171-179.

[10] Abdo A, Rabell S, Simón F, et al. Fatal case of community-acquired pneumonia coinfected with monkeypox virus: clinical and autopsy findings. ASM Case Rep. 2024; 1(1): e00024-e00024.

[11] Chapman JL, Nichols DK, Martinez MJ, Raymond JW. Animal models of orthopoxvirus infection. Vet Pathol. 2010; 47: 852-870.

[12] Domán M, Fehér E, Varga-Kugler R, Jakab F, Bányai K. Animal models used in monkeypox research. Microorganisms. 2022; 10(11): 2192.

[13] Grosenbach DW, Honeychurch K, Rose EA, et al. Oral tecovirimat for the treatment of smallpox. N Engl J Med. 2018; 379: 44-53.

[14] Earl PL, Americo JL, Moss B. Lethal monkeypox virus infection of CAST/EiJ mice is associated with a deficient gamma interferon response. J Virol. 2012; 86: 9105-9112.

[15] Americo JL, Moss B, Earl PL. Identification of wild-derived inbred mouse strains highly susceptible to monkeypox virus infection for use as small animal models. J Virol. 2010; 84: 8172-8180.

[16] Huang B, Zhao H, Song J, et al. Isolation and characterization of monkeypox virus from the first case of monkeypox—Chongqing Municipality, China, 2022. China CDC Wkly. 2022; 4: 1019-1024.

[17] Renne R, Brix A, Harkema J, et al. Proliferative and nonproliferative lesions of the rat and mouse respiratory tract. Toxicol Pathol. 2009; 37: 5S-73S.

[18] Reynolds MG, Carroll DS, Olson VA, et al. A silent enzootic of an orthopoxvirus in Ghana, West Africa: evidence for multi-species involvement in the absence of widespread human disease. Am J Trop Med Hyg. 2010; 82: 746-754.

[19] Ramirez-Soto MC, Arroyo-Hernandez H. Monkeypox virus infections in low-risk groups during the 2022-23 global outbreak: an analysis of the WHO global report. Infez Med. 2024; 32: 12-19.

[20] Americo JL, Sood CL, Cotter CA, et al. Susceptibility of the wild-derived inbred CAST/Ei mouse to infection by orthopoxviruses analyzed by live bioluminescence imaging. Virology. 2014; 449: 120-132.

[21] Zhang Q, Song R, Huang Y, et al. Impaired cellular immunity and cross-reactive humoral responses to mpox virus in HIV-infected individuals vaccinated with vaccinia virus Tiantan strain. MedComm (2020). 2025; 6:e70399.

[22] Zhang D, Liu J, Zhu L, et al. The pathogenicity and multi-organ proteomic profiles of mpox virus infection in SIVmac239-infected rhesus macaques. Nat Commun. 2025; 16:7653.

[23] Stabenow J, Buller RM, Schriewer J, West C, Sagartz JE, Parker S. A mouse model of lethal infection for evaluating prophylactics and therapeutics against monkeypox virus. J Virol. 2010; 84: 3909-3920.

[24] Chaudhri G, Panchanathan V, Bluethmann H, Karupiah G. Obligatory requirement for antibody in recovery from a primary poxvirus infection. J Virol. 2006; 80: 6339-6344.

[25] Stanford MM, McFadden G, Karupiah G, Chaudhri G. Immunopathogenesis of poxvirus infections: forecasting the impending storm. Immunol Cell Biol. 2007; 85: 93-102.

[26] Saghazadeh A, Rezaei N. Insights on mpox virus infection immunopathogenesis. Rev Med Virol. 2023; 33:e2426.

[27] Li H, Huang QZ, Zhang H, et al. The land-scape of immune response to monkeypox virus. EBioMedicine. 2023; 87:104424.

Rights & permissions

2026 The Author(s). Animal Models and Experimental Medicine published by John Wiley & Sons Australia, Ltd on behalf of The Chinese Association for Laboratory Animal Sciences.