FluB-RAM and FluB-RANS: Genome re-arrangement as safe and efficacious live attenuated influenza B virus vaccines. FluB-RAM and FluB-RANS: Genome re-arrangement as safe and efficacious live attenuated influenza B virus vaccines

Influenza B virus (IBV) is considered a major respiratory pathogen responsible for seasonal respiratory disease in humans, particularly severe in children and the elderly. Seasonal influenza vaccination is considered the most efficient strategy to prevent and control IBV infections. Live attenuated influenza virus vaccines (LAIVs) are thought to induce both humoral and cellular immune responses by mimicking a natural infection, but their effectiveness have recently come into question. Thus, the opportunity exists to find alternative approaches to improve overall influenza vaccine effectiveness. Two alternative IBV backbones were developed with re-arranged genomes, re-arranged M (FluB-RAM) and a re-arranged NS (FluB-RANS). Both re-arranged viruses showed temperature sensitivity in vitro compared to the WT type B/Bris strain, were genetically stable over multiple passages in embryonated chicken eggs and were attenuated in vivo in mice. In a prime-boost regime in naïve mice, both re-arranged viruses induced antibodies against HA with hemagglutination inhibition titers considered of protective value. In addition, antibodies against NA and NP were readily detected with potential protective value. Upon lethal IBV challenge, mice previously vaccinated with either FluB-RAM or FluB-RANS were completely protected against clinical disease and mortality. In conclusion, genome re-arrangement renders efficacious LAIV candidates to protect mice against IBV. Overall design: We developed two live attenuated vaccine candidates with re-arranged genome expressing the M2 or NS2 from the PB1 gene segment. DBAJ/2 mice were primed and boosted (3 weeks ppart) with the re-arranged viruses to test safety and protection efficacy. Body weight was recoreded for up to 12 days post vaccination and clinical signs were monitored daily throughout the length of the study. Blood samples were collected at 19 days post-boost (dpb) to assess neutralizing antibody responses through HI and virus neutralization. In addition, sera were used to performa microarrays against multiple influenza A and B protein antigens. Three weeks after boost, mice were challenged with a lethal dose of B/Brisbane/60/2008 PB2 F406Y. Body weigh was recorded for up to 12 days post-challenge (dpc) and clinical signs for up to 14 dpc. Blood and nasal wash samples were collecte at 14 dpc for serology and to determine antigen-specific IgG and IgA responses through microarray analysis.