Abstract: www.nature.com/scientificreports OPEN Ivermectin reduces in vivo coronavirus infection in a mouse experimental model A. P. Arévalo1, R. Pagotto2, J. L. Pórfido1,3, H. Daghero2, M. Segovia4,5, K. Yamasaki6, B. Varela6, M. Hill4,5, J. M. Verdes6, M. Duhalde Vega4,7, M. Bollati‑Fogolín2 & M. Crispo1* The objective of this study was to test the effectiveness of ivermectin for the treatment of mouse hepatitis virus (MHV), a type 2 family RNA coronavirus similar to SARS-CoV-2. Female BALB/cJ mice were infected with 6,000 PFU of MHV-A59 (group infected, n = 20) or infected and then immediately treated with a single dose of 500 µg/kg ivermectin (group infected + IVM, n = 20) or were not infected and treated with PBS (control group, n = 16). Five days after infection/treatment, the mice were euthanized and the tissues were sampled to assess their general health status and infection levels. Overall, the results demonstrated that viral infection induced typical MHV-caused disease, with the livers showing severe hepatocellular necrosis surrounded by a severe lymphoplasmacytic inflammatory infiltration associated with a high hepatic viral load (52,158 AU), while mice treated with ivermectin showed a better health status with a lower viral load (23,192 AU; p < 0.05), with only a few having histopathological liver damage (p < 0.05). No significant differences were found between the group infected + IVM and control group mice (P = NS). Furthermore, serum transaminase levels (aspartate aminotransferase and alanine aminotransferase) were significantly lower in the treated mice than in the infected animals. In conclusion, ivermectin diminished the MHV viral load and disease in the mice, being a useful model for further understanding this therapy against coronavirus diseases. Mouse hepatitis virus (MHV) is a single-stranded RNA coronavirus that targets different o ­ rgans1. The virus is highly contagious, has natural respiratory or oral transmission, and shows high morbidity and low mortality rates. There is no vaccine or treatment available; therefore, upon infection, an entire laboratory mouse colony must be sacrificed to control the disease. Recent studies have shown that the mechanism of infection has similarities to that of SARS-CoV-22,3: therefore, it has been proposed that MHV may be an interesting infection model to test new therapies against COVID19 in animals. Although different therapies have been evaluated, no effective treatment is available, and the mechanism by which the virus enters the cell is being e­ xplored4. After entry into the cytoplasm of the host cell, coronaviruses rely on a nuclear transport system mediated by the importin α/β1 heterodimer to facilitate replication and i­nfection5,6. Some drugs have been demonstrated to act by impairing importin α/β1 heterodimer formation to prevent viral entry. Because both MHV and SARS-CoV-2 enter the nucleus via the same mechanism, MHV may be an interesting target for the development of candidate therapies against coronavirus infection in a mouse model. Ivermectin is an efficient and inexpensive drug usually applied to treat parasitic infestations. It has been approved by the FDA for animal and human use and is available worldwide. It has a wide margin of safety with an ­LD50 of 30 mg/kg in mice and is used in humans as an antiparasitic treatment at a dose of 150–200 µg/kg7. Other effects of this drug, such as a­ ntimicrobial8, anti-trypanosome/anti-malaria9 and anticancer a­..