Abstract
The H1N1 influenza pandemic vaccine has been developed from the A/California/07/09 (Cal) virus and the well-known high-yield A/Puerto Rico/8/34 (PR8) virus by classical reassortment and reverse genetics (RG) in eggs. Previous studies have suggested that Cal-derived chimeric hemagglutinin (HA) and neuraminidase (NA) improve virus yields. However, the cell-based vaccine of the H1N1 pandemic virus has been less investigated. RG viruses that contained Cal-derived chimeric HA and NA could be rescued in Madin–Darby canine kidney cells that expressed α2,6-sialyltransferase (MDCK-SIAT1). The viral growth kinetics and chimeric HA and NA properties were analyzed. We attempted to generate various RG viruses that contained Cal-derived chimeric HA and NA, but half of them could not be rescued in MDCK-SIAT1 cells. When both the 3′- and 5′-terminal regions of Cal HA viral RNA were replaced with the corresponding regions of PR8 HA, the RG viruses were rescued. Our results were largely consistent with those of previous studies, in which the N- and C-terminal chimeric HA slightly improved virus yield. Importantly, the chimeric HA, compared to Cal HA, showed cell fusion ability at a broader pH range, likely due to amino acid substitutions in the transmembrane region of HA. The rescued RG virus with high virus yield harbored the chimeric HA capable of cell fusion at a broader range of pH.
Highlights
The new H1N1 influenza virus emerged in 2009 and has rapidly spread worldwide
Previous studies have indicated that reverse genetics (RG) viruses with chimeric HA viral RNA (vRNA), NIBRG-118, and NIBRG-119, in which the TM-cytoplasmic tail (CT) regions are replaced by the corresponding regions of Puerto Rico/8/34 (PR8)
When the association of NA to the lipid rafts was and P-Cal NAs were found to be not significantly different. These results suggested that the growth investigated, the distribution patterns of PR8, Cal, and P-Cal NAs were found to be not significantly efficiency of RG viruses was not attributed to the affinity of their HA/NA to the lipid rafts
Summary
The new H1N1 influenza virus emerged in 2009 and has rapidly spread worldwide This virus, termed A/California/07/09 (H1N1) (designated as Cal), has a unique feature in terms of genetic combination: five viral RNA (vRNA) segments of swine origin (for hemagglutinin (HA), nucleoprotein (NP), neuraminidase (NA), matrix (M), and non-structure), two of avian origin (for PB2 and PA), and one of human origin (for PB1). The pathogenicity and virulence of this virus were relatively mild, the HA was genetically and antigenically different from that of the previous H1N1 seasonal virus, suggesting the need for a vaccine for the new H1N1 virus. This virus grew very poorly in eggs, which were generally used for the vaccine manufacturing process. The A/Puerto Rico/8/34 (H1N1) virus (designated as PR8) has been used as a backbone virus because it is a well-known high-yield strain in eggs and laboratory
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