TWiV 1323: One influenza infection, two patients

A groundbreaking study reveals that TLR7, a key immune sensor for RNA viruses, worsens outcomes in pregnant mice infected with influenza A—driving maternal and fetal morbidity through vascular dysfunction, neuroinflammation, and impaired fetal development. Contrary to expectations, knocking out TLR7 improved survival and fetal growth, suggesting it's not protective but instead exacerbates immune pathology during pregnancy. This challenges conventional views of immune activation and points to TLR7 and its downstream target OSM as potential therapeutic targets to reduce complications in pregnant women. Separately, a new mRNA vaccine platform using mosaic RBDs delivered via dual quartet mRNA shows promise for broad protection against diverse sarbecoviruses, including future pandemic threats. The vaccine elicits strong cross-reactive antibodies and robust T-cell responses—advantages over traditional protein-based vaccines—and may overcome cold-chain limitations through novel delivery methods. Together, these findings highlight both the risks of overactive immunity in pregnancy and the transformative potential of next-generation mRNA technology.