Poster Presentation 12th Australasian Virology Society Meeting 2024

Identification of molecular factors that influenced reassortment and the emergence of the 1957 and 1968 pandemic influenza viruses (#259)

Mingyang Wang 1 , Ziyi Yang 2 , Sanja Trifkovic 1 , Michael L. Knight 2 , Steven Rockman 1 3 , Ervin Fodor 4 , Lorena Brown 1 , Kanta Subbarao 1 5 , David Bauer 2 , Brad Gilbertson 1
  1. Department of Microbiology and Immunology, University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Parkville, Victoria, Australia
  2. Francis Crick Institute, London, United Kingdom
  3. Seqirus, Parkville, Victoria, Australia
  4. Sir William Dunn School of Pathology, The University of Oxford , Oxford, United Kingdom
  5. WHO Collaborating Centre for Reference and Research on Influenza at The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia

Introduction: The segmented nature of influenza A viruses (IAV) allows reassortment when two strains co-infect a cell, which can lead to the emergence of novel pandemic strains. There is little or no pre-existing immunity in the human population, as occurred in the 1957 and 1968 influenza pandemics.

Methods: We have used two complementary approaches to understand the molecular factors that led to the emergence of the 1957 and 1968 pandemic strains by reassortment. A nine-plasmid competitive transfection model to evaluate bias of incorporation of gene segments into progeny virions one at a time, and sequencing of psoralen-crosslinked, ligated, and selected hybrids (SPLASH), which maps RNA interactions between segments by high-throughput sequencing.

Results: We generated plasmids from A/Singapore/57(H2N2) and A/Hong Kong/68(H3N2) pandemic viruses and precursor viruses circulating in 1956 and 1967. Competitive transfection experiments were used to model reassortment that selected the HA, NA and PB1 genes of avian viruses over those of previously circulating human viruses. SPLASH was performed on wild-type (WT) A/Northern Territory/68 virus as well as A/PR/8/34 (PR8) reassortant viruses containing gene segments derived from 1956/1957 or 1967/1968 viruses. We showed that the PB1 gene segments of both pandemic viruses were preferentially selected over those of precursor circulating viruses in the presence of their cognate pandemic NA gene segments, and that selection was driven by two high-frequency interactions between these segments.