Influenza virus type B nucleoprotein, also known as NP, is composed of a 560 amino acid sequence and is type-specific in influenza viruses. The NP encapsidates the virus genome to form a ribonucleoprotein (RNP) particle for the purposes of transcription and packaging. The monoclonal antibody 3D7 can be paired as a capture antibody for ELISA with clone 1H7a.