Type I interferon signals in macrophages and dendritic cells control dengue virus infection: Implications for a new mouse model to test dengue vaccines

Dengue virus (DENV) infects an estimated 400 million people every year, causing prolonged morbidity and sometimes mortality. Development of an effective vaccine has been hampered by the lack of appropriate small animal models; mice are naturally not susceptible to DENV and only become infected if highly immunocompromised. Mouse models lacking both type I and type II interferon (IFN) receptors (AG129 mice) or the type I IFN receptor (IFNAR^-/- mice) are susceptible to infection with mouseadapted DENV strains but are severely impaired in mounting functional immune responses to the virus and thus are of limited use for study. Here we used conditional deletion of the type IIFN receptor (IFNAR) on individual immune cell subtypes to generate a minimally manipulated mouse model that is susceptible to DENV while retaining global immune competence. Mice lacking IFNAR expression on CD11c⁺ dendritic cells and LysM⁺ macrophages succumbed completely to DENV infection, while mice deficient in the receptor on either CD11c⁺ or LysM⁺ cells were susceptible to infection but often resolved viremia and recovered fully from infection. Conditional IFNAR mice responded with a swift and strong CD8⁺ T-cell response to viral infection, compared to a weak response in IFNAR^-/- mice. Furthermore, mice lacking IFNAR on either CD11c⁺ or LysM⁺ cells were also sufficiently immunocompetent to raise a protective immune response to a candidate subunit vaccine against DENV-2. These data demonstrate that mice with conditional deficiencies in expression of the IFNAR represent improved models for the study of DENV immunology and screening of vaccine candidates.