RSV is a major cause of serious respiratory illness, particularly in infants, older adults, and people with weakened immune systems. The virus uses the attachment protein G to bind to host cells and the fusion protein F to enter them. Although approved RSV antibody products target F, no licensed antibody currently targets G.

Researchers in NIAID's Laboratory of Infectious Diseases (LID) developed a monoclonal antibody that targets a conserved region of G that may be less likely to change over time. In laboratory tests, the IgG3 subclass of this antibody showed about 9-fold greater neutralizing activity than licensed RSV antibodies. Researchers also created an IgG1 version to see whether the IgG3 subclass contributed to this strong activity. The IgG1 version was slightly less potent than the IgG3 form but still showed strong neutralizing activity. These results suggest that IgG subclass can influence the neutralizing activity of this G-targeting antibody.

This technology could support development of first-in-class antibodies targeting RSV G for the prevention or treatment of RSV disease, including in people at high risk for severe illness. These G-targeting antibodies may also be used in combination with existing F-targeting antibodies to broaden protection and potentially improve efficacy. Ongoing engineering efforts are aimed at improving the stability of the G-targeting antibodies and extending their persistence in the body.