Efficacy of oseltamivir treatment in influenza virus infected obese mice

Obesity has been epidemiologically and empirically linked with more severe disease upon influenza infection. To ameliorate severe disease, treatment with antivirals, such as the neuraminidase inhibitor oseltamivir, are suggested to begin within days of infection, especially in hosts at higher risk for poor outcomes. However, this treatment is often poorly effective and can generate resistance variants within the treated host. Here, we hypothesized that oseltamivir treatment would not be effective in genetically obese mice and would generate a more diverse and drug resistant viral population. We demonstrated that oseltamivir treatment does not improve viral clearance in obese mice. While no traditional variants associated with oseltamivir resistance emerged, we did note that drug treatment failed to quench the viral population and did lead to phenotypic drug resistance in vitro. Mechanistically, we demonstrate the blunted interferon response in obese hosts may be contributing to treatment failure, as type I interferon receptor deficient mice also fail to clear influenza virus infection upon oseltamivir administration. Together, these studies suggest that the unique pathogenesis and immune responses in obese mice could have implications for pharmaceutical interventions and the within-host dynamics of the influenza virus population. IMPORTANCEInfluenza virus infections, while typically resolving within days to weeks, can turn critical especially in high-risk populations. Prompt antiviral administration is crucial to mitigating these severe sequalae, yet concerns remain if antiviral treatment is effective in hosts with obesity. Here, we show that oseltamivir does not improve viral clearance in genetically obese or type I IFN receptor-deficient mice and increases the genetic entropy of the within-host viral population. This suggests a blunted immune response may impair oseltamivir efficacy and render a host more susceptible to severe disease. This study furthers our understanding of oseltamivir treatment dynamics both systemically and in the lungs of obese mice, as well as the consequences of oseltamivir treatment for the within-host emergence of drug-resistant variants.