Egg-adaptive mutations in H3N2v vaccine virus enhance egg-based production without loss of antigenicity or immunogenicity. Issue 28 (22nd June 2015)

• Record Type: Journal Article
• Authors: Barman, Subrata; Franks, John; Turner, Jasmine C.; Yoon, Sun-Woo; Webster, Robert G.; Webby, Richard J.
• Is Part Of: Vaccine. Volume 33:Issue 28(2015)
• Page Start: 3186
• Page End: 3192
• Publication Date: 2015-06-22
• Subjects: Influenza A virus -- Egg adaptation -- Antigenicity -- Immunogenicity -- Vaccine virus -- Hemagglutinin H3 mutations -- Zoonosis -- Variant virus; H3N2v H3N2 variant -- CVV candidate vaccine virus -- MDCK Madin-Darby canine kidney cells -- TRBC turkey red bold cells -- CRBC chicken red blood cells -- PFU plaque forming unit.; Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2015.05.011
• Languages: English
• ISSNs: 0264-410X

Abstract

Highlights: We passaged variant influenza A H3N2v virus in eggs to induce egg-adaptive HA mutations. PR8-based 6 + 2 candidate vaccine viruses (CVVs) with the HA mutations were characterized. Four sets of HA substitutions retained their immunogenicity and produced high-yield HA. The HA substitutions G186V + N246 K appear optimal for egg-based H3N2v vaccine production. Abstract: The recently detected zoonotic H3N2 variant influenza A (H3N2v) viruses have caused 343 documented cases of human infection linked to contact with swine. An effective vaccine is needed for these viruses, which may acquire transmissibility among humans. However, viruses isolated from human cases do not replicate well in embryonated chicken eggs, posing an obstacle to egg-based vaccine production. To address this issue, we sought to identify egg-adaptive mutations in surface proteins that increase the yield of candidate vaccine viruses (CVVs) in eggs while preserving their immunizing effectiveness. After serial passage of a representative H3N2v isolate (A/Indiana/08/2011), we identified several egg-adaptive combinations of HA mutations and assessed the egg-based replication, antigenicity, and immunogenicity of A/Puerto Rico/8/34 (H1N1, PR8)-based 6 + 2 reverse genetics CVVs carrying these mutations. Here we demonstrate that the respective combined HA substitutions G1861 V + N2461 K, N1651 K + G1861 V, T1281 N + N1651 K + R762 G, and T1281 N + N1651 K + I102 M, all identified after egg passage, enhanced the replication of the CVVs in eggs without substantially affecting their antigenicity or immunogenicity. The mutations were stable, and the mutant viruses acquired no additional substitutions during six subsequent egg passages. We found two crucial mutations, G186V, which was previously defined, and N246K, which in combination improved virus yield in eggs without significantly impacting antigenicity or immunogenicity. This combination of egg-adaptive mutations appears to most effectively generate high egg-based yields of influenza A/Indiana/08/2011-like CVVs.