Influenza virus lung infection protects from respiratory syncytial virus-induced immunopathology

The effect of infection history is ignored in most animal models of infecti ous disease. The attachment protein of respiratory syncytial virus (RSV) in duces T helper cell type 2-driven pulmonary eosinophilia in mice similar to that seen in the failed infant vaccinations in the 1960s. We show that pre vious influenza virus infection of mice: (a) protects against weight loss, illness, and lung eosinophilia; (b) attenuates recruitment of inflammatory cells; and (c) reduces cytokine secretion caused by RSV attachment protein without affecting RSV clearance. This protective effect can be transferred via influenza-immune splenocytes to naive mice and is long lived. Previous immunity to lung infection clearly plays an important and underestimated ro le in subsequent vaccination and infection. The data have important implica tions for the timing of vaccinations in certain patient groups, and may con tribute to variability in disease susceptibility observed in humans.