Abstract: The respiratory syncytial virus (RSV) is a major cause of lower respiratory tract disease in infants and children throughout the world. RSV is a major cause of pneumonia and bronchiolitis in infants under one year of age, and is a major cause of fatal respiratory tract disease in these infants. The treatment and prevention of RSV infection has been problematic. However, the present invention addresses some of these concerns by providing attenuated RSV strains that are suitable for inclusion in immunizing compositions. Specifically, the present invention is directed toward the introduction of growth restriction mutations into incompletely attenuated host range-restricted cold-passaged respiratory syncytial virus (cpRSV) strains by further passage of the strains at increasingly reduced temperatures to produce derivative strains which are more satisfactorily attenuated.

Abstract: The present invention provides vaccine compositions of attenuated respiratory syncytial virus (RSV). More particularly, the attenuated virus may be a derivative of RSV which has been incompletely attenuated by cold-passage or introduction of mutations which produce virus having a temperature sensitive (ts) or cold adapted (ca) phenotype. The invention also provides methods for stimulating the immune system of an individual to induce protection against respiratory syncytial virus by administration of attenuated RSV. The invention also provides pure cultures of attenuated RS virus, wherein the virus has been more completely attenuated by the further derivatization of previously identified incompletely attenuated ts or cp mutants.