Definition

A Fc-engineered recombinant human immunoglobulin (Ig) G1 kappa monoclonal antibody against the fusion protein (F protein) of human respiratory syncytial virus (RSV), that can be used for prophylactic and protective purposes in RSV infections. Upon administration, nirsevimab targets and binds to the F1 and F2 subunits of the RSV fusion (F) protein, thereby locking the RSV F protein in the prefusion conformation and blocking viral entry into the host cell. This neutralizes the virus and prevents syncytia formation. This may prevent RSV and RSV-associated lower respiratory tract infection (LRTI) among infants and young children. RSV F protein, a small envelop glycoprotein, is required for cytopathic syncytia formation resulting from cell-to-cell fusion. It is necessary for viral infection and spreading. Nirsevimab has an extended half-life and one administration may therefore provide seasonal protection against RSV.