Limiters of gene exchange
Influenza viruses, which have segmented genomes, can exchange genes through a process called reassortment, which can lead to the formation of novel influenza viruses. At the termini of each gene segment are regions called packaging signals, which direct the incorporation of each gene segment into virus particles during assembly.
A recent study by White et al (2017) demonstrated that heterologous packaging signals limit the efficiency of reassortment, but that this phenotype is dependent on the influenza virus gene segment being examined.
Of note, 85% of the reassortant viruses studied packaged a hemagglutinin (HA) segment carrying matched packaging signals relative to the background of the virus. The HA segment is of particular interest from a public health perspective due to its antigenic properties, and these data suggest that HA packaging signals could be an important factor in determining the likelihood that two influenza virus strains will undergo reassortment.
Original research: https://dx.doi.org/10.1128%2FJVI.00195-17
Maria White is a PhD candidate in the Immunology and Molecular Pathogenesis program at Emory University.