Alternative Live-Attenuated Influenza Vaccines Based on Modifications in the Polymerase Genes Protect against Epidemic and Pandemic Flu

Abstract

Human influenza is a seasonal disease associated with significant morbidity and mortality. Influenza vaccination is the most effective means for disease prevention. We have previously shown that mutations in the PB1 and PB2 genes of the live-attenuated influenza vaccine (LAIV) from the cold-adapted (ca) influenza virus A/Ann Arbor/6/60 (H2N2) could be transferred to avian influenza viruses and produce partially attenuated viruses. We also demonstrated that avian influenza viruses carrying the PB1 and PB2 mutations could be further attenuated by stably introducing a hemagglutinin (HA) epitope tag in the PB1 gene. In this work, we wanted to determine whether these modifications would also result in attenuation of a so-called triple reassortant (TR) swine influenza virus (SIV). Thus, the TR influenza A/swine/Wisconsin/14094/99 (H3N2) virus was generated by reverse genetics and subsequently mutated in the PB1 and PB2 genes. Here we show that a combination of mutations in this TR backbone results in an attenuated virus in vitro and in vivo. Furthermore, we show the potential of our TR backbone as a vaccine that provides protection against the 2009 swine-origin pandemic influenza H1N1 virus (S-OIV) when carrying the surface of a classical swine strain. We propose that the availability of alternative backbones to the conventional ca A/Ann Arbor/6/60 LAIV strain could also be useful in epidemic and pandemic influenza and should be considered for influenza vaccine development. In addition, our data provide evidence that the use of these alternative backbones could potentially circumvent the effects of original antigenic sin (OAS) in certain circumstances.

Influenza Viruses with Rearranged Genomes as Live-Attenuated Vaccines

“…We chose this strain because it grows well in eggs and tissue culture and has been shown to replicate in several animal species, such as mice, chickens, and ferrets, without previous adaptation (13,21). In addition, we previously showed that LAIVs based on the wt H9N2 background have adequate attenuation and protection efficacy profiles (13,21,22).…”

Efficacy in Pigs of Inactivated and Live Attenuated Influenza Virus Vaccines against Infection and Transmission of an Emerging H3N2 Similar to the 2011-2012 H3N2v

“…While live attenuated influenza virus (LAIV) vaccines have been approved for use in people and horses, a LAIV for swine has yet to make it to market. This is despite a number of LAIV vaccines that have been developed and demonstrated to provide significant cross-protection in experimentally infected pigs (12)(13)(14)(15).…”

The Temperature-Sensitive and Attenuation Phenotypes Conferred by Mutations in the Influenza Virus PB2, PB1, and NP Genes Are Influenced by the Species of Origin of the PB2 Gene in Reassortant Viruses Derived from Influenza A/California/07/2009 and A/WSN/33 Viruses

“…The WF10 virus backbone is of avian origin, whereas the Sw99 and 2009 pH1N1 virus backbones contain a triple-reassortant internal gene (TRIG) cassette with the PA and PB2 gene segments from an avian influenza virus and the PB1 gene segment from a human influenza virus. The NP, M, and NS gene segments of Sw99 are derived from a classical swine influenza virus lineage (8), while the NA and M gene segments of the pH1N1 virus are from a Eurasian swine H1N1 virus lineage and the HA, NP, and NS gene segments are from a classical swine H1N1 virus lineage (10).…”

“…In order to develop LAIVs for use in the poultry and swine industries and to protect humans against zoonotic influenza virus infections, several groups have investigated the use of backbones comprised of gene segments from avian and/or swine viruses as an alternative to AA ca. To this end, the ts signature from the AA ca virus has been experimentally inserted into a backbone of influenza A/Guinea fowl/Hong Kong/WF10/99 H9N2 virus (WF10) (6,7), A/swine/Wisconsin/14094/99 H3N2 virus (Sw99) (8), and 2009 pandemic HIN1 (pH1N1) influenza A/New York/1682/2009 virus (NY1682) (9). The WF10 virus backbone is of avian origin, whereas the Sw99 and 2009 pH1N1 virus backbones contain a triple-reassortant internal gene (TRIG) cassette with the PA and PB2 gene segments from an avian influenza virus and the PB1 gene segment from a human influenza virus.…”