Dengue virus disease phenotypes in C57BL/6N Ifnar1^-/-Ifngr1^-/- mice

Dengue virus (DENV) remains a major global health problem, and experimentally tractable animal models are essential for investigating severe dengue pathogenesis and antiviral or vaccine strategies. However, whereas interferon receptor-deficient mouse models are used, the disease phenotype in C57BL/6N Ifnar1-/- Ifngr1-/- double-knockout (DKO) mice has not been sufficiently characterized. Here, we generated and characterized C57BL/6N-based DKO mice deficient in both type I and type II interferon receptors (Ifnar1-/- Ifngr1-/-). We first assessed susceptibility to DENV-2 NGC infection in wild-type, single-knockout, and DKO mice and found that combined Ifnar1 and Ifngr1 loss was required for rapid and severe disease. DENV-2 NGC-infected DKO mice exhibited marked weight loss, severe clinical manifestations, and 100% mortality. We then performed phenotypic screening using selected DENV serotype 1-4 strains under strain-specific inoculation conditions. This revealed strain- and condition-dependent differences in disease outcomes, and DENV-2 NGC was selected for further characterization based on the rapid lethal disease observed under the conditions used. Detailed characterization of DENV-2 NGC infection demonstrated progressive viral RNA accumulation in multiple organs, including the liver, brain, spleen, and large intestine, and infectious virus was detected in selected peripheral tissues. Histopathological analyses revealed multi-organ tissue alterations with inflammatory changes and vascular abnormalities, and Evans blue extravasation assays demonstrated increased vascular permeability in infected tissues. Collectively, these findings establish a C57BL/6N-based Ifnar1-/- Ifngr1-/- mouse platform for studying DENV-2 NGC-induced severe disease phenotypes and provide a practical framework for future mechanistic and preclinical studies on antiviral or vaccine strategies.