Influenza A NP (383-391) (HLA-B27) is a CEF control peptide that is derived from Influenza A. Influenza A is an enveloped negative-strand RNA virus that is capable of interfering with host transcription, which can ultimately cause cell death. The action of the virus particles decreases the downstream gene occupancy of RNA polymerase II, as well as instigating cellular stress, resulting in the failure of polymerase II termination at poly(A) sites. Influenza A NP (383-391) (HLA-B27) is defined as a CEF control peptide due to its antigenic properties. Clinically, this peptide is a suitable epitope for CD8+ T cells and can be used to stimulate the release of IFNg. HLA-B27 refers to the cell HLA type that this peptide acts on.

The nucleoprotein (NP) is a structural protein that encapsulates the negative strand of viral RNA. NP plays a critical role in the transition of influenza virus RNA synthesis from transcription mode to replication mode.