Table 1.

Influenza virus genes and proteins. Gene segments are listed for influenza A virus (IAV), influenza B virus (IBV), influenza C virus (ICV), and influenza D virus (IDV). The protein product(s) of each segment and their associated functions are summarized for each influenza species [4,27,31].

Gene Segment	IAV	IBV	Viral Function
1	PB2	PB2	RNA-dependent RNA polymerase (RDRP) component
2	PB1	PB1	RDRP component
	PB1-F2 1		Inflammation, apoptosis, regulation of host immune responses
	PB1-N40 1		Regulates PB1 expression and activity
3	PA	PA	RDRP component
	PA-X 1		Enhances viral gene expression, facilitates host mRNA degradation, regulation of cell-mediated host responses
	PA-N155 1		Functions unknown, likely involved with viral replication
	PA-N182 1		Functions unknown, likely involved with viral replication
4	HA	HA	Host receptor binding and membrane fusion
5	NP	NP	Packages viral RNA in vRNPs 2 with RDRP components
6	NA	NA	Sialidase; assists with release of new virions from host cell
		NB	Function unknown but highly conserved
7	M1	M1	Facilitates packing of vRNPs into new virions
	M2	BM2	Ion channel; assists in release of vRNPs into host cytoplasm
	M42 1		Alternate ion channel
8	NS1	NS1	Host immune response antagonism
	NS2/NEP	NS2/NEP	Nuclear export protein for newly synthesized vRNPs
Gene Segment	ICV	IDV	Viral Function
1	PB2	PB2	RNA-dependent RNA polymerase (RDRP) component
2	PB1	PB1	RDRP component
3	P3	P3	RDRP component
4	HEF	HEF	Host receptor binding, membrane fusion; esterase; assists release of new virions
5	NP	NP	Packages viral RNA in vRNPs with RDRP components
6	M1	M1	Facilitates packing of vRNPs into new virions
	CM2	DM2	Ion channel; assists in release of vRNPs into host cytoplasm
7	NS1	NS1	Host immune response antagonism
	NS2	NS2	Nuclear export protein for newly synthesized vRNPs

¹ Accessory protein; ² vRNPs: viral ribonucleoproteins.