Respiratory syncytial virus (RSV) is a virus that causes lung infections, particularly in infants and young children. It can lead to serious illness and even death in this age group. RSV is divided into two types, RSV/A and RSV/B, based on differences in a specific gene. Both types circulate, but usually one is more common each season.
The virus has two key proteins on its surface, the G protein and the F protein, which help the body produce antibodies. The F protein is more stable and has been the main focus for developing RSV vaccines. Currently, there is no approved vaccine for RSV, but many are being developed.
RSV/A and RSV/B are further divided into subtypes based on variations in the G gene. During RSV season, multiple subtypes can circulate within a community. The GA2 subtype has been the most common for RSV/A for nearly a decade but is now being replaced by the ON1 subtype. The BA subtype has been the most common for RSV/B since 2005. Both ON1 and BA have unique duplications in their G genes.
The F protein exists in two forms: pre-fusion and post-fusion. The pre-fusion form is unstable and changes to the stable post-fusion form. Both forms are being studied as vaccine candidates. They share some common sites for antibody binding but also have unique sites.
Although the F protein is generally stable, some variations have been observed in different parts of the protein. This report examines the sequence variability of the F gene from a large collection of RSV sequences over 50 years to understand how this variability affects vaccine development.