Establishment and characterization of a lethal mouse model for the Angola strain of Marburg virus

Infections with Marburg virus (MARV) and Ebola virus (EBOV) cause severe hemorrhagic fever in humans and nonhuman primates (NHPs) with fatality rates up to 90%. A number of experimental vaccine and treatment platforms have previously been shown to be protective against EBOV infection. However, the rate of development for prophylactics and therapeutics against MARV has been lower in comparison, possibly because a small-animal model is not widely available. Here we report the development of a mouse model for studying the pathogenesis of MARV Angola (MARV/Ang), the most virulent strain of MARV. Infection with the wild-type virus does not cause disease in mice, but the adapted virus (MARV/Ang-MA) recovered from liver homogenates after 24 serial passages in severe combined immunodeficient (SCID) mice caused severe disease when administered intranasally (i.n.) or intraperitoneally (i.p.). The median lethal dose (LD₅₀) was determined to be 0.015 50% TCID₅₀ (tissue culture infective dose) of MARV/Ang-MA in SCID mice, and i.p. infection at a dose of 1,000 × LD₅₀ resulted in death between 6 and 8 days postinfection in SCID mice. Similar results were obtained with immunocompetent BALB/c and C57BL/6 mice challenged i.p. with 2,000 × LD₅₀ of MARV/Ang-MA. Virological and pathological analyses of MARV/Ang-MA-infected BALB/c mice revealed that the associated pathology was reminiscent of observations made in NHPs with MARV/Ang. MARV/Ang-MA-infected mice showed most of the clinical hallmarks observed with Marburg hemorrhagic fever, including lymphopenia, thrombocytopenia, marked liver damage, and uncontrolled viremia. Virus titers reached 108 TCID₅₀/ml in the blood and between 10⁶ and 10¹⁰ TCID₅₀/g tissue in the intestines, kidney, lungs, brain, spleen, and liver. This model provides an important tool to screen candidate vaccines and therapeutics against MARV infections.