Usutu virus encephalitis: establishment of a mouse model and characterization of severe disease

Author(s)

Rebeca de Paiva Froes Rocha

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2022-11-16

Examining board members

Rafael Elias Marques; José Luiz Proença Módena; Murilo de Carvalho; Luciana Barros de Arruda; Mauro Martins Teixeira

• Advisor: Rafael Elias Marques

Abstract

Encephalitis is a severe manifestation of neurological disease that may lead to sequelae or death. The causes of encephalitis in humans are undetermined in up to 60% of all cases, which may be attributed to neurotropic viruses. "Usutu virus" (USUV) is an arbovirus that may cause encephalitis in humans and other vertebrates. This pathogen demands greater attention due to increased detection in mosquitos and birds throughout Africa and Central Europe, and due to the lack of specific treatments or vaccines. In this work, we established a mouse model of USUV infection to characterize disease and pathogenic inflammatory processes associated to infection. C57BL/6J mice (8-12 weeks old) were intracranially infected with 104 PFU of USUV, leading to signs of neurological disease including hunched back, paralysis, and conjunctivitis, and death on day 6 p.i.. On the peak of disease, we observed increased viral load and levels of Inflammatory cytokines such as CXCL1, CCL5, IFN-Y, IL-6 in the brain but not in the periphery. Disease was also characterized by meningeal cell infiltration and microglia activation. Aiming to identify an effective antiviral drug against USUV infection, we tested the viral polymerase inhibitor 7-Deaza-2’-C-Methyladenosine (7DMA). Type I Interferon receptor knockout mice (IFNAR?/?) were subcutaneously infected with a lethal dose of USUV and treated daily with either the vehicle solution or 7DMA [50mg/kg] via gavage for 6 days after the infection. Mice treated with 7DMA showed delayed mortality when compared to vehicle treated mice. The treatment also resulted in decreased viral loads in the brain, spleen liver and serum. CCL5, CXCL-1 and IFNy were increased in the spleen but only CXCL-1 was increased in the brain. The treatment was able to decrease the levels of CXCL1 in the brain during early points of the infection but not on the peak of disease. In summary, we were able to characterize some of the inflammatory features of USUV infection in adult wild type mice. From the standpoint of pharmacological strategies against USUV infection, 7DMA efficiently reduced the viral load and delayed mortality in mice, indicating that antiviral strategies were partially protective against disease and that 7DMA is a promising drug against USUV infection (AU)

• FAPESP's process: 18/02594-9 - Development of a model of Usutu virus infection in mice: study of disease and testing of a neuroprotective compound
• Grantee: Rebeca de Paiva Froes Rocha
• Support Opportunities: Scholarships in Brazil - Doctorate