Immunity’s pregnant pause facing influenza in allogenically-mated mice

Over the last centuries, influenza pandemics caused a high number of fatalities worldwide. Lessons learned from the recent 2009 H1N1 pandemic resulted in a paradigm shift, as pregnant women are now recognizing as the highest risk group. Here, we present an allogenic mouse infection model, which mirrors this severe course of pandemic influenza observed in pregnant women. Using this model, we identified a failure to mount the innate and adaptive immune response in pregnant mice, including a reduced migratory capacity of anti-viral effector CD8+ T cells into the lung. The resulting prolonged viral presence prompted an increased viral mutation rate in pregnant mice, which revealed an enhanced viral pathogenicity. Our present findings will increase the alertness of influenza as a threat in humans, which can fundamentally revise the currently poor influenza vaccination compliance among women during their reproductive years.