A Respiratory Syncytial Virus trailer sequence modulates viral replication and copy-back defective viral genome generation and propagation kinetics

Once considered byproducts of in vitro viral replication, cbDVGs have since been detected in clinical specimens and implicated in affecting infection outcomes. The molecular mechanism of cbDVG generation remains unclear, thereby hindering our ability to manipulate cbDVG production during infection for therapeutic gain.

Previous work showed that respiratory syncytial virus (RSV) cbDVG re-initiation sites cluster in trailer-end hotspots R1, R2, and R3, and that a poly-U mutation in R1 selectively reduced cbDVG formation at the mutated region. Here, we reported that a 10U mutation in R2 drastically reduced cbDVGs in this region in both minigenome and recombinant virus systems. Furthermore, during high-MOI passaging of the R2-10U virus, we observed delayed detection of cbDVGs with re-initiation sites in R1-R3 (trailer cbDVGs) compared to WT, while no differences in virus titers were observed.