Prefusion F-specific antibodies determine the magnitude of RSV neutralizing activity in human sera

Area of Science:

• Virology and Immunology
• Vaccine Development

Background:

• Respiratory syncytial virus (RSV) is a major global health threat, particularly to infants, causing significant mortality.
• Viral entry is mediated by the RSV fusion (F) glycoprotein, which exists in prefusion (pre-F) and postfusion (post-F) conformations.
• Antigenic site Ø on the pre-F conformation is a key target for neutralizing antibodies.

Purpose of the Study:

• To quantify the contribution of antibodies targeting antigenic site Ø and other sites on the RSV F protein to overall neutralizing activity in human sera.
• To assess the impact of antibody specificities across different age groups (7-93 years).

Main Methods:

• Sera adsorption assays using stabilized pre-F and post-F proteins to measure the reduction in neutralizing activity.
• Protein competition neutralization assays utilizing pre-F mutants with altered antigenic sites (Ø and II).
• Binding competition assays with monoclonal antibodies (mAbs) to correlate antibody binding with neutralization.

Main Results:

• Adsorption with pre-F protein removed over 90% of neutralizing activity, while post-F adsorption removed only about 30%.
• Antigenic site Ø accounted for approximately 35% of neutralizing activity, whereas site II contributed less than 10%.
• The level of site Ø-specific antibodies strongly correlated with neutralizing activity, unlike site II antibodies.

Conclusions:

• Neutralizing activity in human sera against RSV is predominantly mediated by antibodies specific for the prefusion F protein, particularly those targeting site Ø.
• Vaccine strategies aiming to induce or enhance RSV neutralizing activity should utilize pre-F antigens that effectively present and preserve antigenic site Ø.