Analytical technologies for influenza virus-like particle candidate vaccines: challenges and emerging approaches

Table 3 Comparison of HA assay response from VLPs produced in Mammalian and Insect cells and chicken egg derived influenza virus

Production System	Influenza strain	Sample preparation	HA titer	Contamination	Normalized Concentration (HA units/ml)
VLPs from Sf9 - baculovirus infection [16]	HA:A/California/07/2009 (H1N1)	Cell culture media	16 HA units/50 μl	baculovirus 10⁸ BV/ml	16 HA units/50 μl
VLPs from Sf9 - baculovirus infection [16]	M1:A/Udorn/307/1972 (H3N2)	Cell culture media	16 HA units/50 μl	baculovirus 10⁸ BV/ml	16 HA units/50 μl
VLPs from HighFive - baculovirus infection [16]	HA:A/California/07/2009 (H1N1)	Cell culture media	16 HA units/50 μl	baculovirus 10⁶ BV/ml	16 HA units/50 μl
VLPs from HighFive - baculovirus infection [16]	M1:A/Udorn/307/1972 (H3N2)	Cell culture media	16 HA units/50 μl	baculovirus 10⁶ BV/ml	16 HA units/50 μl
VLPs from HEK 293 T - plasmid transfection [17]	HA/NA/M1: A/Puerto Rico/8/34 (H1N1)	Purified VLPs concentrated 200 times	32 HA units/50 μl	none	0.16 HA units/50 μl
VLPs from HEK 293 T - baculovirus transduction [17]	HA/NA/M1	Purified VLPs concentrated 200 times	128 HA units/50 μl	none	0.64 HA units/50 μl
VLPs from HEK 293 T - baculovirus transduction [17]	A/Puerto Rico/8/34 (H1N1)	Purified VLPs concentrated 200 times	128 HA units/50 μl	none	0.64 HA units/50 μl
Influenza virus Chicken Eggs [59]	H1N1 A/PR/8/1934	Purified virus	256 HA units/50 μl	none	256 HA units/50 μl

This is a rough comparison, as each system used a different source of red blood cells (chicken, turkey, human) at different percentages (0.5-1.25%).

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