Abstract
In addition to influenza A subtypes, two distinct lineages of influenza B virus also cause seasonal epidemics to humans. Recently, Dudas et al. have done evolutionary analyses of reassortment patterns of the virus and suggested genetic lineage relationship between PB1, PB2, and HA genes. Using genetic plasmids and reassortant viruses, we here demonstrate that a homologous lineage PB1-PB2 pair exhibits better compatibility than a heterologous one and that the lineage relationship between PB1 and HA is more important for viral replication than that between PB2 and HA. However, co-adaptation of PB1-PB2-HA genes appears to be affected by complete gene constellation.
Highlights
In addition to influenza A subtypes, two distinct lineages of influenza B virus cause seasonal epidemics to humans
No subtype classification has been applied to this virus, but the two antigenically distinct lineages, so-called Victoria (B/Victoria/2/87) and Yamagata (B/Yamagata/16/88), have diverged since mid 1980s3
Based on the analysis of the eight genetic segments, Dudas et al reported that only PB1, PB2, and HA genes of influenza B virus (IBV) maintain two separate lineages whereas the other segments are frequently exchanged between the Yamagata (PA, NP, NA, and M genes) and Victoria (NS gene) lineages[6]
Summary
After propagation in embryonated chicken eggs and purification by a plaque assay in MDCK cells (ATCC, Manassas, VA, USA), viral RNA sequences of the eight gene segments of these viruses were determined and used for the full gene plasmid construction into a bidirectional pDZ plasmid[19]. Using these plasmids, we generated PB1-, PB2-, and/or HA-reassorted viruses on either Bris-Vc or Wisc-Ym genetic backbone by reverse genetics[20] and confirmed the correct genetic replacement of the target gene(s) from one lineage to the other using a reverse transcription PCR method. Cell supernatants were collected at 8, 16, 24, and 48 hpi and used for the titration of viral replication in MDCK cells by the plaque assay
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