WHO/BS/2017.2318 Report on the WHO collaborative study to establish the 1st IS for antiserum to Respiratory Syncytial Virus

Overview

A collaborative study was conducted with the aim to establish the 1st International Standard for antiserum to RSV. Two candidate standards were produced from serum samples donated by healthy adult individuals in the US. The candidate standards are intended to standardize RSV neutralization assays across multiple assay formats. These assays are particularly useful in the evaluation of immunogenicity of RSV vaccine candidates. The candidates were processed, filled and freeze-dried at NIBSC. The study consisted of 21 laboratories from 9 countries and included university laboratories, manufacturers/developers of RSV vaccines and public health laboratories. All participants used their own in-house virus neutralization assay and their own virus stocks. The study samples comprised the two candidate standards,16/284 and 16/322, naturally infected adult sera, age stratified naturally infected paediatric sera, sera from RSV vaccine clinical trials in maternal and elderly subjects, a monoclonal antibody to RSV (palivizumab), two cotton rat serum samples and samples from the BEI Resources panel of human antiserum and immune globulin to RSV.

The collaborative study showed that between-laboratory variability in neutralization titres was significantly reduced when values were expressed relative to those of either of the two candidate international standards. Stability of 16/284 maintained for 6 months at different temperatures showed no significant loss of activity (relative to that at -20 oC storage temperature) at temperatures of up to +20oC. Stability data are not yet available for 16/322. From these results, 16/284 is recommended as the 1st international standard for antiserum to RSV, with 16/322 as a potential replacement for 16/284 in the future, with an assigned unitage of 1,000 and 960 International Units (IU) of anti-RSV neutralising antibodies per vial, respectively.