Efficacy and safety studies of a recombinant chimeric respiratory syncytial virus FG glycoprotein vaccine in cotton rats

Several formulations of a recombinant chimeric respiratory syncytial virus (RSV) vaccine consisting of the extramembrane domains of the F and G glycop roteins (FG) were tested in cotton rats to evaluate efficacy and safety. Th e FG vaccine was highly immunogenic, providing nearly complete resistance t o pulmonary infection at doses as low as 25 ng in spite of inducing relativ ely low levels of serum neutralizing antibody at low vaccine doses. Upon RS V challenge animals primed,vith FG vaccine showed quite mild alveolitis and interstitial pneumonitis, which were eliminated by the addition of monopho sphoryl lipid A to the formulation.