Stabilization of respiratory syncytial virus (RSV) against thermal inactivation and freeze-thaw cycles for development and control of RSV vaccines and immune globulin.

A high-titered and stable respiratory syncytial virus (RSV) is essential for the development of RSV vaccines and quality control of vaccines and RSV immune globulin. We increased the virus titer of RSV seed stock, and virus preparations made from this seed stock, 100 times by removing defective interfering particles using limiting dilution procedure. RSV preparations made from the new seed stock had infectivity titers ranging from 10(7.6) to 10(8.2) TCID50 per ml for five lots made over a period of 3 years. Unstabilized RSV lost most of its infectivity at -86 degrees C within 2-3 weeks, at 37 degrees C within 24 hr, at 56 degrees C within 3 min and after five freeze-thaw cycles. The high titered virus was stabilized at -86 degrees C for 3 years, at 37 degrees C for 3 days, at 56 degrees C for 6 min and against five freeze-thaw cycles. Most effective stabilizers included 25% sucrose, 10% trehalose and 45% fetal bovine serum (FBS) in Medium 199 whereas 3.5% dimethyl sulfoxide, > or = 45% FBS in phosphate buffered saline, 40% glycerol and 10% sorbitol also stabilized RSV to lesser and variable degrees. A mixture of 0.5% gelatine and 0.3% sodium glutamate stabilized the virus for a short period whereas 0.1 M MgCl2 and 25% FBS did not stabilize the virus. The stabilized high-titered virus is very useful for achieving reproducibility in serologic assays. A broad spectrum of stabilizers, such as those evaluated in this study, would be useful in choosing the most suitable formulation for stabilizing a live RSV vaccine.