Abstract
Current egg-based influenza vaccine production technology can't promptly meet the global demand during an influenza pandemic as shown in the 2009 H1N1 pandemic. Moreover, its manufacturing capacity would be vulnerable during pandemics caused by highly pathogenic avian influenza viruses. Therefore, vaccine production using mammalian cell technology is becoming attractive. Current influenza H5N1 vaccine strain (NIBRG-14), a reassortant virus between A/Vietnam/1194/2004 (H5N1) virus and egg-adapted high-growth A/PR/8/1934 virus, could grow efficiently in eggs and MDCK cells but not Vero cells which is the most popular cell line for manufacturing human vaccines. After serial passages and plaque purifications of the NIBRG-14 vaccine virus in Vero cells, one high-growth virus strain (Vero-15) was generated and can grow over 108 TCID50/ml. In conclusion, one high-growth H5N1 vaccine virus was generated in Vero cells, which can be used to manufacture influenza H5N1 vaccines and prepare reassortant vaccine viruses for other influenza A subtypes.
Highlights
Outbreaks of avian influenza H5N1 viruses emerged in 1997 and are still killing avian hosts and causing zoonotic transmission to humans in 2011, posing the persistent threat of influenza pandemics in humans [1]
It is well known that wild-type influenza viruses and eggadapted high-growth reasortant influenza vaccine viruses can grow efficiently in MDCK cells but not Vero cells [3,15,16,17,18]
After 20 passages of an egg-adaptedd high-growth reassortant H1N1 vaccine virus in Vero cells, the titer of infectious virus increased 3 (7.18 to 7.70 log10 plaque forming unit (PFU)/ml) to 26 (6.95 to 8.37 log10 TCID50/ ml) folds and their viral antigenicity and HA sequences were stable in a previous study [15]
Summary
Outbreaks of avian influenza H5N1 viruses emerged in 1997 and are still killing avian hosts and causing zoonotic transmission to humans in 2011, posing the persistent threat of influenza pandemics in humans [1]. Most current seasonal influenza vaccines are manufactured using chicken embryonated eggs, which is labor-intensive and hard to scale up during a pandemic. Vero and MDCK cells, have been licensed for manufacturing influenza vaccines [3,4,5,6]. There are four clades of influenza H5N1 viruses circulating in avian hosts and causing zoonotic transmission to humans. The NIBRG-14 vaccine virus could grow to high titers in chicken eggs and MDCK cells but not Vero cells which is the most popular cell line for manufacturing human vaccines [8,9,10,11]. This study was conducted to adapt the NIBRG-14 vaccine virus to grow efficiently in Vero cells
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