Contribution of Neuraminidase of Influenza Viruses to the Sensitivity to Sera Inhibitors and Reassortment Efficiency

Table 7.: Origin of NA and PB2 genes of A/Leningrad/134/17/57 MDV reassortants with PR8-based strains for inactivated influenza vaccine.

PR8-based Strain for Inactivated Influenza Vaccine2	Reassortants1 of A/Leningrad/134/17/57 (H2N2) MDV with PR8-based Strains
	Total	Number (%) of Reassortants Inheriting PB2 and NA Gene Segments from MDV or WT Parental Virus2
		PB2 Gene From		NA Gene From
		PR8	MDV3	WT virus	MDV
NIBRG-23 (H5N1)4	17	0	17 (100%)	0	17 (100%)
NIBRG-23 (H5N1)4	20	20 (100%)	0	20 (100%)	0
INDO/05 (H5N1)	11	0	11 (100%)	0	11 (100%)
VN1203 (H5N1)	28	0	28 (100%)	0	28 (100%)
VN1203 (H5N1)	14	14 (100%)	0	14 (100%)	0
IRV-148 (H1N1)	285	0	28 (100%)	28 (100%)	0
NIB-64 (H3N2)	96	4 (44.4%)	5 (55.6%)	9 (100%)	0

¹All reassortants contained HA from WT virus. The origin of PB1, PA, NP, M, and NS genes varied. ²PR8-based strains for inactivated influenza vaccine contain HA and NA from the appropriate WT virus, and the 6 internal genes from PR8 virus. ³MDV: A/Leningrad/134/17/57 (H2N2). ⁴Reassortants were generated after co-infecting MDV and NIBRG-23 (H5N1) virus inactivated by ultraviolet light. 56/28 IRV-148-based reassortants and 62/9 NIB-64-based reassortants were 6:2.