Influenza virus type A nucleoprotein, also known as NP, is composed of a 498 amino acid sequence and is type-specific in influenza viruses. The NP encapsulates the virus genome to form a ribonucleoprotein (RNP) particle for the purposes of transcription and packaging. The monoclonal antibody FluA-NP 4F1 has been shown to specifically recognize type A influenza virus NP in virus infected cell culture and patient samples. This clone can be paired as a detection antibody for ELISA with clone FluA-NP 2C9.